Patent Publication Number: US-11648364-B2

Title: Textile seal-forming structure with multiple curvatures

Description:
1 CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. national phase of International Application No. PCT/AU2020/051109 filed Jul. 9, 2020 which designated the U.S. and claims priority to AU 2020902371 filed Jul. 9, 2020, and is a continuation-in-part of U.S. application Ser. No. 16/850,803, filed Apr. 16, 2020, which is a continuation-in-part of International Application No. PCT/IB2019/058832, the entire contents of each of which are hereby incorporated by reference. 
     International Application No. PCT/IB2019/058832 claims the benefit of U.S. Provisional Application No. 62/805,147, filed Feb. 13, 2019, and also claims the benefit of Australian Provisional Application Nos. AU2018904886, filed Dec. 21, 2018, and AU2018903752, filed Oct. 16, 2018, each of which is also hereby incorporated herein by reference in their entirety. 
     2 BACKGROUND OF THE TECHNOLOGY 
     2.1 Field of the Technology 
     The present technology relates to one or more of the screening, diagnosis, monitoring, treatment, prevention and amelioration of respiratory-related disorders. The present technology also relates to medical devices or apparatus, and their use. 
     2.2 Description of the Related Art 
     2.2.1 Human Respiratory System and its Disorders 
     The respiratory system of the body facilitates gas exchange. The nose and mouth form the entrance to the airways of a patient. 
     The airways include a series of branching tubes, which become narrower, shorter and more numerous as they penetrate deeper into the lung. The prime function of the lung is gas exchange, allowing oxygen to move from the inhaled air into the venous blood and carbon dioxide to move in the opposite direction. The trachea divides into right and left main bronchi, which further divide eventually into terminal bronchioles. The bronchi make up the conducting airways, and do not take part in gas exchange. Further divisions of the airways lead to the respiratory bronchioles, and eventually to the alveoli. The alveolated region of the lung is where the gas exchange takes place, and is referred to as the respiratory zone. See “ Respiratory Physiology ”, by John B. West, Lippincott Williams &amp; Wilkins, 9th edition published 2012. 
     A range of respiratory disorders exist. Certain disorders may be characterised by particular events, e.g. apneas, hypopneas, and hyperpneas. 
     Examples of respiratory disorders include Obstructive Sleep Apnea (OSA), Cheyne-Stokes Respiration (CSR), respiratory insufficiency, Obesity Hyperventilation Syndrome (OHS), Chronic Obstructive Pulmonary Disease (COPD), Neuromuscular Disease (NMD) and Chest wall disorders. 
     Obstructive Sleep Apnea (OSA), a form of Sleep Disordered Breathing (SDB), is characterised by events including occlusion or obstruction of the upper air passage during sleep. It results from a combination of an abnormally small upper airway and the normal loss of muscle tone in the region of the tongue, soft palate and posterior oropharyngeal wall during sleep. The condition causes the affected patient to stop breathing for periods typically of 30 to 120 seconds in duration, sometimes 200 to 300 times per night. It often causes excessive daytime somnolence, and it may cause cardiovascular disease and brain damage. The syndrome is a common disorder, particularly in middle aged overweight males, although a person affected may have no awareness of the problem. See U.S. Pat. No. 4,944,310 (Sullivan). 
     Respiratory failure is an umbrella term for respiratory disorders in which the lungs are unable to inspire sufficient oxygen or exhale sufficient CO 2  to meet the patient&#39;s needs. Respiratory failure may encompass some or all of the following disorders. 
     A patient with respiratory insufficiency (a form of respiratory failure) may experience abnormal shortness of breath on exercise. 
     A range of therapies have been used to treat or ameliorate such conditions. Furthermore, otherwise healthy individuals may take advantage of such therapies to prevent respiratory disorders from arising. However, these have a number of shortcomings. 
     2.2.2 Therapies 
     Various respiratory therapies, such as Continuous Positive Airway Pressure (CPAP) therapy, Non-invasive ventilation (NIV), Invasive ventilation (IV), and High Flow Therapy (HFT) have been used to treat one or more of the above respiratory disorders. 
     2.2.2.1 Respiratory Pressure Therapies 
     Respiratory pressure therapy is the application of a supply of air to an entrance to the airways at a controlled target pressure that is nominally positive with respect to atmosphere throughout the patient&#39;s breathing cycle (in contrast to negative pressure therapies such as the tank ventilator or cuirass). 
     Continuous Positive Airway Pressure (CPAP) therapy has been used to treat Obstructive Sleep Apnea (OSA). The mechanism of action is that continuous positive airway pressure acts as a pneumatic splint and may prevent upper airway occlusion, such as by pushing the soft palate and tongue forward and away from the posterior oropharyngeal wall. Treatment of OSA by CPAP therapy may be voluntary, and hence patients may elect not to comply with therapy if they find devices used to provide such therapy one or more of: uncomfortable, difficult to use, expensive and aesthetically unappealing. 
     2.2.2.2 Flow Therapies 
     Not all respiratory therapies aim to deliver a prescribed therapeutic pressure. Some respiratory therapies aim to deliver a prescribed respiratory volume, by delivering an inspiratory flow rate profile over a targeted duration, possibly superimposed on a positive baseline pressure. In other cases, the interface to the patient&#39;s airways is ‘open’ (unsealed) and the respiratory therapy may only supplement the patient&#39;s own spontaneous breathing with a flow of conditioned or enriched gas. In one example, High Flow therapy (HFT) is the provision of a continuous, heated, humidified flow of air to an entrance to the airway through an unsealed or open patient interface at a “treatment flow rate” that is held approximately constant throughout the respiratory cycle. The treatment flow rate is nominally set to exceed the patient&#39;s peak inspiratory flow rate. HFT has been used to treat OSA, CSR, respiratory failure, COPD, and other respiratory disorders. One mechanism of action is that the high flow rate of air at the airway entrance improves ventilation efficiency by flushing, or washing out, expired CO 2  from the patient&#39;s anatomical deadspace. Hence, HFT is thus sometimes referred to as a deadspace therapy (DST). Other benefits may include the elevated warmth and humidification (possibly of benefit in secretion management) and the potential for modest elevation of airway pressures. As an alternative to constant flow rate, the treatment flow rate may follow a profile that varies over the respiratory cycle. 
     Another form of flow therapy is long-term oxygen therapy (LTOT) or supplemental oxygen therapy. Doctors may prescribe a continuous flow of oxygen enriched air at a specified oxygen concentration (from 21%, the oxygen fraction in ambient air, to 100%) at a specified flow rate (e.g., 1 litre per minute (LPM), 2 LPM, 3 LPM, etc.) to be delivered to the patient&#39;s airway. 
     2.2.2.3 Supplementary Oxygen 
     For certain patients, oxygen therapy may be combined with a respiratory pressure therapy or HFT by adding supplementary oxygen to the pressurised flow of air. When oxygen is added to respiratory pressure therapy, this is referred to as RPT with supplementary oxygen. When oxygen is added to HFT, the resulting therapy is referred to as HFT with supplementary oxygen. 
     2.2.3 Respiratory Therapy Systems 
     These respiratory therapies may be provided by a respiratory therapy system or device. Such systems and devices may also be used to screen, diagnose, or monitor a condition without treating it. 
     A respiratory therapy system may comprise a Respiratory Pressure Therapy Device (RPT device), an air circuit, a humidifier, a patient interface, an oxygen source, and data management. 
     2.2.3.1 Patient Interface 
     A patient interface may be used to interface respiratory equipment to its wearer, for example by providing a flow of air to an entrance to the airways. The flow of air may be provided via a mask to the nose and/or mouth, a tube to the mouth or a tracheostomy tube to the trachea of a patient. Depending upon the therapy to be applied, the patient interface may form a seal, e.g., with a region of the patient&#39;s face, to facilitate the delivery of gas at a pressure at sufficient variance with ambient pressure to effect therapy, e.g., at a positive pressure of about 10 cmH 2 O relative to ambient pressure. For other forms of therapy, such as the delivery of oxygen, the patient interface may not include a seal sufficient to facilitate delivery to the airways of a supply of gas at a positive pressure of about 10 cmH 2 O. For flow therapies such as nasal HFT, the patient interface is configured to insufflate the nares but specifically to avoid a complete seal. One example of such a patient interface is a nasal cannula. 
     Certain other mask systems may be functionally unsuitable for the present field. For example, purely ornamental masks may be unable to maintain a suitable pressure. Mask systems used for underwater swimming or diving may be configured to guard against ingress of water from an external higher pressure, but not to maintain air internally at a higher pressure than ambient. 
     Certain masks may be clinically unfavourable for the present technology e.g. if they block airflow via the nose and only allow it via the mouth. 
     Certain masks may be uncomfortable or impractical for the present technology if they require a patient to insert a portion of a mask structure in their mouth to create and maintain a seal via their lips. 
     Certain masks may be impractical for use while sleeping, e.g. for sleeping while lying on one&#39;s side in bed with a head on a pillow. 
     The design of a patient interface presents a number of challenges. The face has a complex three-dimensional shape. The size and shape of noses and heads varies considerably between individuals. Since the head includes bone, cartilage and soft tissue, different regions of the face respond differently to mechanical forces. The jaw or mandible may move relative to other bones of the skull. The whole head may move during the course of a period of respiratory therapy. 
     As a consequence of these challenges, some masks suffer from being one or more of obtrusive, aesthetically undesirable, costly, poorly fitting, difficult to use, and uncomfortable especially when worn for long periods of time or when a patient is unfamiliar with a system. Wrongly sized masks can give rise to reduced compliance, reduced comfort and poorer patient outcomes. Masks designed solely for aviators, masks designed as part of personal protection equipment (e.g. filter masks), SCUBA masks, or for the administration of anaesthetics may be tolerable for their original application, but nevertheless such masks may be undesirably uncomfortable to be worn for extended periods of time, e.g., several hours. This discomfort may lead to a reduction in patient compliance with therapy. This is even more so if the mask is to be worn during sleep. 
     CPAP therapy is highly effective to treat certain respiratory disorders, provided patients comply with therapy. If a mask is uncomfortable, or difficult to use a patient may not comply with therapy. Since it is often recommended that a patient regularly wash their mask, if a mask is difficult to clean (e.g., difficult to assemble or disassemble), patients may not clean their mask and this may impact on patient compliance. 
     While a mask for other applications (e.g. aviators) may not be suitable for use in treating sleep disordered breathing, a mask designed for use in treating sleep disordered breathing may be suitable for other applications. 
     For these reasons, patient interfaces for delivery of CPAP during sleep form a distinct field. 
     2.2.3.1.1 Seal-Forming Structure 
     Patient interfaces may include a seal-forming structure. Since it is in direct contact with the patient&#39;s face, the shape and configuration of the seal-forming structure can have a direct impact the effectiveness and comfort of the patient interface. 
     A patient interface may be partly characterised according to the design intent of where the seal-forming structure is to engage with the face in use. In one form of patient interface, a seal-forming structure may comprise a first sub-portion to form a seal around the left naris and a second sub-portion to form a seal around the right naris. In one form of patient interface, a seal-forming structure may comprise a single element that surrounds both nares in use. Such single element may be designed to for example overlay an upper lip region and a nasal bridge region of a face. In one form of patient interface a seal-forming structure may comprise an element that surrounds a mouth region in use, e.g. by forming a seal on a lower lip region of a face. In one form of patient interface, a seal-forming structure may comprise a single element that surrounds both nares and a mouth region in use. These different types of patient interfaces may be known by a variety of names by their manufacturer including nasal masks, full-face masks, nasal pillows, nasal puffs and oro-nasal masks. 
     A seal-forming structure that may be effective in one region of a patient&#39;s face may be inappropriate in another region, e.g. because of the different shape, structure, variability and sensitivity regions of the patient&#39;s face. For example, a seal on swimming goggles that overlays a patient&#39;s forehead may not be appropriate to use on a patient&#39;s nose. 
     Certain seal-forming structures may be designed for mass manufacture such that one design fit and be comfortable and effective for a wide range of different face shapes and sizes. To the extent to which there is a mismatch between the shape of the patient&#39;s face, and the seal-forming structure of the mass-manufactured patient interface, one or both must adapt in order for a seal to form. 
     One type of seal-forming structure extends around the periphery of the patient interface, and is intended to seal against the patient&#39;s face when force is applied to the patient interface with the seal-forming structure in confronting engagement with the patient&#39;s face. The seal-forming structure may include an air or fluid filled cushion, or a moulded or formed surface of a resilient seal element made of an elastomer such as a rubber. With this type of seal-forming structure, if the fit is not adequate, there will be gaps between the seal-forming structure and the face, and additional force will be required to force the patient interface against the face in order to achieve a seal. 
     Another type of seal-forming structure incorporates a flap seal of thin material positioned about the periphery of the mask so as to provide a self-sealing action against the face of the patient when positive pressure is applied within the mask Like the previous style of seal forming portion, if the match between the face and the mask is not good, additional force may be required to achieve a seal, or the mask may leak. Furthermore, if the shape of the seal-forming structure does not match that of the patient, it may crease or buckle in use, giving rise to leaks. 
     Another type of seal-forming structure may comprise a friction-fit element, e.g. for insertion into a naris, however some patients find these uncomfortable. 
     Another form of seal-forming structure may use adhesive to achieve a seal. Some patients may find it inconvenient to constantly apply and remove an adhesive to their face. 
     A range of patient interface seal-forming structure technologies are disclosed in the following patent applications, assigned to ResMed Limited: WO 1998/004,310; WO 2006/074,513; WO 2010/135,785. 
     One form of nasal pillow is found in the Adam Circuit manufactured by Puritan Bennett. Another nasal pillow, or nasal puff is the subject of U.S. Pat. No. 4,782,832 (Trimble et al.), assigned to Puritan-Bennett Corporation. 
     ResMed Limited has manufactured the following products that incorporate nasal pillows: SWIFT™ nasal pillows mask, SWIFT™ II nasal pillows mask, SWIFT™ LT nasal pillows mask, SWIFT™ FX nasal pillows mask and MIRAGE LIBERTY™ full-face mask. The following patent applications, assigned to ResMed Limited, describe examples of nasal pillows masks: International Patent Application WO2004/073,778 (describing amongst other things aspects of the ResMed Limited SWIFT™ nasal pillows), US Patent Application 2009/0044808 (describing amongst other things aspects of the ResMed Limited SWIFT™ LT nasal pillows); International Patent Applications WO 2005/063,328 and WO 2006/130,903 (describing amongst other things aspects of the ResMed Limited MIRAGE LIBERTY™ full-face mask); International Patent Application WO 2009/052,560 (describing amongst other things aspects of the ResMed Limited SWIFT™ FX nasal pillows). 
     2.2.3.1.2 Positioning and Stabilising 
     A seal-forming structure of a patient interface used for positive air pressure therapy is subject to the corresponding force of the air pressure to disrupt a seal. Thus a variety of techniques have been used to position the seal-forming structure, and to maintain it in sealing relation with the appropriate portion of the face. 
     One technique is the use of adhesives. See for example US Patent Application Publication No. US 2010/0000534. However, the use of adhesives may be uncomfortable for some. 
     Another technique is the use of one or more straps and/or stabilising harnesses. Many such harnesses suffer from being one or more of ill-fitting, bulky, uncomfortable and awkward to use. 
     2.2.3.2 Respiratory Pressure Therapy (RPT) Device 
     A respiratory pressure therapy (RPT) device may be used individually or as part of a system to deliver one or more of a number of therapies described above, such as by operating the device to generate a flow of air for delivery to an interface to the airways. The flow of air may be pressure-controlled (for respiratory pressure therapies) or flow-controlled (for flow therapies such as HFT). Thus RPT devices may also act as flow therapy devices. Examples of RPT devices include a CPAP device and a ventilator. 
     Air pressure generators are known in a range of applications, e.g. industrial-scale ventilation systems. However, air pressure generators for medical applications have particular requirements not fulfilled by more generalised air pressure generators, such as the reliability, size and weight requirements of medical devices. In addition, even devices designed for medical treatment may suffer from shortcomings, pertaining to one or more of: comfort, noise, ease of use, efficacy, size, weight, manufacturability, cost, and reliability. 
     An example of the special requirements of certain RPT devices is acoustic noise. 
     Table of noise output levels of prior RPT devices (one specimen only, measured using test method specified in ISO 3744 in CPAP mode at 10 cmH 2 O). 
     
       
         
           
               
               
               
             
               
                   
               
               
                   
                 A-weighted sound 
                 Year 
               
               
                 RPT Device name 
                 pressure level dB(A) 
                 (approx.) 
               
               
                   
               
             
            
               
                 C-Series Tango ™ 
                 31.9 
                 2007 
               
               
                 C-Series Tango ™ with Humidifier 
                 33.1 
                 2007 
               
               
                 S8 Escape ™ II 
                 30.5 
                 2005 
               
               
                 S8 Escape ™ II with H4i ™ Humidifier 
                 31.1 
                 2005 
               
               
                 S9 AutoSet ™ 
                 26.5 
                 2010 
               
               
                 S9 AutoSet ™ with H5i Humidifier 
                 28.6 
                 2010 
               
               
                   
               
            
           
         
       
     
     One known RPT device used for treating sleep disordered breathing is the S9 Sleep Therapy System, manufactured by ResMed Limited. Another example of an RPT device is a ventilator. Ventilators such as the ResMed Stellar™ Series of Adult and Paediatric Ventilators may provide support for invasive and non-invasive non-dependent ventilation for a range of patients for treating a number of conditions such as but not limited to NMD, OHS and COPD. 
     The ResMed Elisée™ 150 ventilator and ResMed VS III™ ventilator may provide support for invasive and non-invasive dependent ventilation suitable for adult or paediatric patients for treating a number of conditions. These ventilators provide volumetric and barometric ventilation modes with a single or double limb circuit. RPT devices typically comprise a pressure generator, such as a motor-driven blower or a compressed gas reservoir, and are configured to supply a flow of air to the airway of a patient. In some cases, the flow of air may be supplied to the airway of the patient at positive pressure. The outlet of the RPT device is connected via an air circuit to a patient interface such as those described above. 
     The designer of a device may be presented with an infinite number of choices to make. Design criteria often conflict, meaning that certain design choices are far from routine or inevitable. Furthermore, the comfort and efficacy of certain aspects may be highly sensitive to small, subtle changes in one or more parameters. 
     2.2.3.3 Air Circuit 
     An air circuit is a conduit or a tube constructed and arranged to allow, in use, a flow of air to travel between two components of a respiratory therapy system such as the RPT device and the patient interface. In some cases, there may be separate limbs of the air circuit for inhalation and exhalation. In other cases, a single limb air circuit is used for both inhalation and exhalation. 
     2.2.3.4 Humidifier 
     Delivery of a flow of air without humidification may cause drying of airways. The use of a humidifier with an RPT device and the patient interface produces humidified gas that minimizes drying of the nasal mucosa and increases patient airway comfort. In addition, in cooler climates, warm air applied generally to the face area in and about the patient interface is more comfortable than cold air. 
     A range of artificial humidification devices and systems are known, however they may not fulfil the specialised requirements of a medical humidifier. 
     Medical humidifiers are used to increase humidity and/or temperature of the flow of air in relation to ambient air when required, typically where the patient may be asleep or resting (e.g. at a hospital). A medical humidifier for bedside placement may be small. A medical humidifier may be configured to only humidify and/or heat the flow of air delivered to the patient without humidifying and/or heating the patient&#39;s surroundings. Room-based systems (e.g. a sauna, an air conditioner, or an evaporative cooler), for example, may also humidify air that is breathed in by the patient, however those systems would also humidify and/or heat the entire room, which may cause discomfort to the occupants. Furthermore, medical humidifiers may have more stringent safety constraints than industrial humidifiers 
     While a number of medical humidifiers are known, they can suffer from one or more shortcomings. Some medical humidifiers may provide inadequate humidification, some are difficult or inconvenient to use by patients. 
     2.2.3.5 Data Management 
     There may be clinical reasons to obtain data to determine whether the patient prescribed with respiratory therapy has been “compliant”, e.g. that the patient has used their RPT device according to one or more “compliance rules”. One example of a compliance rule for CPAP therapy is that a patient, in order to be deemed compliant, is required to use the RPT device for at least four hours a night for at least 21 of 30 consecutive days. In order to determine a patient&#39;s compliance, a provider of the RPT device, such as a health care provider, may manually obtain data describing the patient&#39;s therapy using the RPT device, calculate the usage over a predetermined time period, and compare with the compliance rule. Once the health care provider has determined that the patient has used their RPT device according to the compliance rule, the health care provider may notify a third party that the patient is compliant. 
     There may be other aspects of a patient&#39;s therapy that would benefit from communication of therapy data to a third party or external system. 
     Existing processes to communicate and manage such data can be one or more of costly, time-consuming, and error-prone. 
     2.2.3.6 Mandibular Repositioning 
     A mandibular repositioning device (MRD) or mandibular advancement device (MAD) is one of the treatment options for sleep apnea and snoring. It is an adjustable oral appliance available from a dentist or other supplier that holds the lower jaw (mandible) in a forward position during sleep. The MRD is a removable device that a patient inserts into their mouth prior to going to sleep and removes following sleep. Thus, the MRD is not designed to be worn all of the time. The MRD may be custom made or produced in a standard form and includes a bite impression portion designed to allow fitting to a patient&#39;s teeth. This mechanical protrusion of the lower jaw expands the space behind the tongue, puts tension on the pharyngeal walls to reduce collapse of the airway and diminishes palate vibration. 
     In certain examples a mandibular advancement device may comprise an upper splint that is intended to engage with or fit over teeth on the upper jaw or maxilla and a lower splint that is intended to engage with or fit over teeth on the lower jaw or mandible. The upper and lower splints are connected together laterally via a pair of connecting rods. The pair of connecting rods are fixed symmetrically on the upper splint and on the lower splint. 
     In such a design the length of the connecting rods is selected such that when the MRD is placed in a patient&#39;s mouth the mandible is held in an advanced position. The length of the connecting rods may be adjusted to change the level of protrusion of the mandible. A dentist may determine a level of protrusion for the mandible that will determine the length of the connecting rods. 
     Some MRDs are structured to push the mandible forward relative to the maxilla while other MADs, such as the ResMed Narval CC™ MRD are designed to retain the mandible in a forward position. This device also reduces or minimises dental and temporo-mandibular joint (TMJ) side effects. Thus, it is configured to minimises or prevent any movement of one or more of the teeth. 
     2.2.3.7 Vent Technologies 
     Some forms of treatment systems may include a vent to allow the washout of exhaled carbon dioxide. The vent may allow a flow of gas from an interior space of a patient interface, e.g., the plenum chamber, to an exterior of the patient interface, e.g., to ambient. 
     The vent may comprise an orifice and gas may flow through the orifice in use of the mask. Many such vents are noisy. Others may become blocked in use and thus provide insufficient washout. Some vents may be disruptive of the sleep of a bed partner  1100  of the patient  1000 , e.g. through noise or focused airflow. 
     ResMed Limited has developed a number of improved mask vent technologies. See International Patent Application Publication No. WO 1998/034,665; International Patent Application Publication No. WO 2000/078,381; U.S. Pat. No. 6,581,594; US Patent Application Publication No. US 2009/0050156; US Patent Application Publication No. 2009/0044808. 
     Table of noise of prior masks (ISO 17510-2:2007, 10 cmH 2 O pressure at 1 m) 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                   
                 A-weighted 
                 A-weighted 
                   
               
               
                   
                   
                 sound power 
                 sound pressure 
               
               
                   
                 Mask 
                 level dB(A) 
                 dB(A) 
                 Year 
               
               
                 Mask name 
                 type 
                 (uncertainty) 
                 (uncertainty) 
                 (approx.) 
               
               
                   
               
             
            
               
                 Glue-on (*) 
                 nasal 
                 50.9 
                 42.9 
                 1981 
               
               
                 ResCare 
                 nasal 
                 31.5 
                 23.5 
                 1993 
               
               
                 standard (*) 
               
               
                 ResMed 
                 nasal 
                 29.5 
                 21.5 
                 1998 
               
               
                 Mirage ™ (*) 
               
               
                 ResMed 
                 nasal 
                 36 (3) 
                 28 (3) 
                 2000 
               
               
                 UltraMirage ™ 
               
               
                 ResMed 
                 nasal 
                 32 (3) 
                 24 (3) 
                 2002 
               
               
                 Mirage 
               
               
                 Activa ™ 
               
               
                 ResMed 
                 nasal 
                 30 (3) 
                 22 (3) 
                 2008 
               
               
                 Mirage 
               
               
                 Micro ™ 
               
               
                 ResMed 
                 nasal 
                 29 (3) 
                 22 (3) 
                 2008 
               
               
                 Mirage ™ 
               
               
                 SoftGel 
               
               
                 ResMed 
                 nasal 
                 26 (3) 
                 18 (3) 
                 2010 
               
               
                 Mirage ™ FX 
               
               
                 ResMed 
                 nasal 
                 37   
                 29   
                 2004 
               
               
                 Mirage Swift ™ 
                 pillows 
               
               
                 (*) 
               
               
                 ResMed 
                 nasal 
                 28 (3) 
                 20 (3) 
                 2005 
               
               
                 Mirage Swift ™ 
                 pillows 
               
               
                 II 
               
               
                 ResMed 
                 nasal 
                 25 (3) 
                 17 (3) 
                 2008 
               
               
                 Mirage Swift ™ 
                 pillows 
               
               
                 LT 
               
               
                 ResMed AirFit 
                 nasal 
                 21 (3) 
                 13 (3) 
                 2014 
               
               
                 P10 
                 pillows 
               
               
                   
               
               
                 ((*) one specimen only, measured using test method specified in ISO 3744 in CPAP mode at 10 cmH 2 O) 
               
            
           
         
       
     
     Sound pressure values of a variety of objects are listed below 
                                         A-weighted sound           Object   pressure dB(A)   Notes                  Vacuum cleaner: Nilfisk   68   ISO 3744 at 1 m       Walter Broadly Litter Hog: B+       distance       Grade       Conversational speech   60   1 m distance       Average home   50       Quiet library   40       Quiet bedroom at night   30       Background in TV studio   20                    
2.2.4 Screening, Diagnosis, and Monitoring Systems
 
     Polysomnography (PSG) is a conventional system for diagnosis and monitoring of cardio-pulmonary disorders, and typically involves expert clinical staff to apply the system. PSG typically involves the placement of 15 to 20 contact sensors on a patient in order to record various bodily signals such as electroencephalography (EEG), electrocardiography (ECG), electrooculograpy (EOG), electromyography (EMG), etc. PSG for sleep disordered breathing has involved two nights of observation of a patient in a clinic, one night of pure diagnosis and a second night of titration of treatment parameters by a clinician. PSG is therefore expensive and inconvenient. In particular it is unsuitable for home screening/diagnosis/monitoring of sleep disordered breathing. 
     Screening and diagnosis generally describe the identification of a condition from its signs and symptoms. Screening typically gives a true/false result indicating whether or not a patient&#39;s SDB is severe enough to warrant further investigation, while diagnosis may result in clinically actionable information. Screening and diagnosis tend to be one-off processes, whereas monitoring the progress of a condition can continue indefinitely. Some screening/diagnosis systems are suitable only for screening/diagnosis, whereas some may also be used for monitoring. 
     Clinical experts may be able to screen, diagnose, or monitor patients adequately based on visual observation of PSG signals. However, there are circumstances where a clinical expert may not be available, or a clinical expert may not be affordable. Different clinical experts may disagree on a patient&#39;s condition. In addition, a given clinical expert may apply a different standard at different times. 
     3 BRIEF SUMMARY OF THE TECHNOLOGY 
     The present technology is directed towards providing medical devices used in the screening, diagnosis, monitoring, amelioration, treatment, or prevention of respiratory disorders having one or more of improved comfort, cost, efficacy, ease of use and manufacturability. 
     A first aspect of the present technology relates to apparatus used in the screening, diagnosis, monitoring, amelioration, treatment or prevention of a respiratory disorder. 
     Another aspect of the present technology relates to methods used in the screening, diagnosis, monitoring, amelioration, treatment or prevention of a respiratory disorder. 
     An aspect of certain forms of the present technology is to provide methods and/or apparatus that improve the compliance of patients with respiratory therapy. 
     One form of the present technology is a patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to a patient&#39;s airways including at least entrance of a patient&#39;s nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient&#39;s respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: 
     a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and 
     a seal-forming structure. 
     One form of the present technology comprises a textile seal-forming structure with a bridge portion between a first hole and a second hole, the bridge portion is crimped so as to be held in greater tension than a remainder of the textile membrane. 
     Another aspect of one form of the present technology is a seal-forming structure having a textile membrane coupled to a flexible support structure in a relaxed state, and a bridge portion of the textile membrane is crimped so as to be held in greater tension than a remainder of the textile membrane. 
     Another aspect of the present technology is a patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to a patient&#39;s airways including at least entrance of a patient&#39;s nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient&#39;s respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: 
     a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and 
     a seal-forming structure having:
         a textile membrane constructed and arranged to form a pressure-assisted seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways inferior to a nasal bridge region of the patient&#39;s face, said textile membrane having a portion, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use,       

     wherein:
         the textile membrane is held in a relaxed state, and   the portion is held in greater tension than a remainder of the textile membrane, e.g., selectively tensioned.       

     In some aspects, the textile membrane has at least one hole or two holes formed such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient&#39;s airways. 
     In some aspects, the portion is tensioned via various techniques, including crimping at one or more portions of the textile membrane, e.g., a central portion and/or a bridge portion. Instead of or in addition to the central or bridge portion, one or more other portions of the textile membrane may be tensioned, e.g., crimping or other techniques. The textile membrane may be supported by a flexible support that may be subject to selective tensioning, as an alternative or in addition to selective tensioning of one or more portions of the textile membrane. 
     Another aspect of the present technology is a patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to a patient&#39;s airways including at least entrance of a patient&#39;s nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient&#39;s respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: 
     a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and 
     a seal-forming structure having:
         a textile membrane constructed and arranged to form a pressure-assisted seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways inferior to a nasal bridge region of the patient&#39;s face, said textile membrane having at least one hole such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient&#39;s nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use,       

     wherein:
         the textile membrane includes a first portion held in a relaxed state and a second portion held in a taut state, the taut state of the second portion configured to allow the seal-forming structure to include a three-dimensional shape having multiple curvatures.       

     In some aspects, a) an area of the first portion is greater than an area of the second portion; b) the at least one hole includes a first hole and a second hole, each configured to be positioned adjacent one of the patient&#39;s nares in use, and wherein a bridge portion is disposed between the first hole and the second hole; c) the bridge portion is the second portion and is held in a taut state; d) the bridge portion is crimped so as to be held in greater tension than the first portion of the textile membrane; e) the bridge portion includes a first section and a second section, the first section being substantially flat and configured to contact the patient in use, and the second section extending into the plenum chamber; f) the bridge portion is crimped using ultrasonic welding and/or an adhesive; and/or g) ultrasonic welding and/or adhesives are applied to the second section. 
     In some aspects a) the seal-forming structure further includes a flexible support structure for holding the textile membrane in the three-dimensional shape; b) the seal-forming structure includes a single wall, and wherein an end of the flexible support structure contacts the textile membrane; c) the seal-forming structure includes a pair of walls, wherein the flexible support structure includes a free end, and the textile membrane is coupled to the flexible support structure distal to the free end, and wherein the free end is spaced apart from the textile membrane so that the textile membrane is arranged radially outside of the free end; d) the flexible support structure is coupled to the textile membrane using injection molding; and/or e) the bridge portion is a locating spigot after being crimped. 
     In some aspects a) the textile membrane includes a first curvature about a first axis intersecting the first hole and the second hole, and wherein before being crimped, the bridge portion includes a bridge curvature about the first axis in an opposite direction from a remainder of the textile membrane; b) a second axis extends transverse to the first axis and along the bridge portion, the textile membrane including a secondary curvature about the second axis; c) the secondary curvature has one of a domed region and a saddle region, and the first curvature has the other of a domed region and a saddle region; d) the secondary curvature is configured to contact the patient&#39;s subnasale, in use; e) a third axis extends transverse to the second axis and skewed with respect to the first axis, the textile membrane including a tertiary curvature about the third axis; f) the tertiary curvature is configured to contact the patient&#39;s lip superior, in use; g) a fourth axis extends transverse to the second axis and to the third axis, and parallel to the first axis, the textile membrane including a quaternary curvature about the fourth axis; h) the quaternary curvature includes a variable radius of curvature; and/or i) the quaternary curvature extends into the primary curvature proximate to an edge of the textile membrane. 
     In some aspects a) a portion of the first hole distal to the bridge portion is movable between a first position and a second position; b) the first position is a natural state, and the textile membrane moves to the second position as a result of an external force; c) the portion of the first hole extends into the plenum chamber in the second position; d) the first hole includes a substantially tear-drop shape in the second position; e) in the second position, the first hole is configured to contact a periphery of the entrance to one of the patient&#39;s nares proximate to an alar rim; and/or f) a portion of the second hole distal to the bridge portion is movable between the first position and the second position. 
     In some aspects a) the textile membrane includes a textile layer and a silicone layer coupled to the textile layer, the silicone layer having impermeable properties; b) the silicone layer is approximately 0.5 mm thick.; c) the silicone layer is disposed within the cavity and is configured to not touch the patient&#39;s skin, in use; and/or d) the silicone layer has a low durometer characteristic, and the textile membrane includes a high stretch capability when coupled to the flexible support structure. 
     In some aspects a) a length of the bridge portion is directly related to a size of the first hole and to a size of the second hole; b) the textile membrane is configured to be curved about at least two non-parallel axes as a result of taut state of the second portion in order to form the three-dimensional shape; c) the textile membrane includes a multi-layered textile material and silicone layer coupled to the multi-layered textile material; d) the multi-layered textile material includes a first layer, a second layer, and a third layer, the silicone layer contacting only the first layer, and wherein the third layer is configured to contact the patient&#39;s face, in use; e) the first layer and the third layer are constructed from nylon, and wherein the second layer is constructed from spandex; f) the textile membrane is approximately 0.35 mm to approximately 0.45 mm thick; and/or g) the patient&#39;s nose and lip superior are configured to contact only the textile membrane, in use. 
     Another aspect of the present technology is a patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to a patient&#39;s airways including at least entrance of a patient&#39;s nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient&#39;s respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: 
     a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and 
     a seal-forming structure having:
         a textile membrane constructed and arranged to form a pressure-assisted seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways inferior to a nasal bridge region of the patient&#39;s face, said textile membrane having a first hole and a second hole and a bridge portion disposed between the first hole and the second hole, the first hole and the second hole formed therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient&#39;s nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use, and   a flexible support structure for holding the textile membrane in a predefined shape;       

     wherein:
         the textile membrane is coupled to the flexible support structure in a relaxed state, and   the bridge portion is crimped so as to be held in greater tension than a remainder of the textile membrane.       

     Another aspect of the present technology is a patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance of a patient&#39;s nares and to an entrance of the patient&#39;s mouth, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient&#39;s respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: 
     a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and 
     a seal-forming structure comprising a textile membrane constructed and arranged to form a pressure-assisted seal with a region of the patient&#39;s face surrounding the entrance to the patient&#39;s nares and the entrance to the patient&#39;s mouth, the seal-forming structure comprising:
         a nasal portion configured to at least partially surround the entrance to the patient&#39;s nares, and   an oral portion configured to at least partially surround the entrance to the patient&#39;s mouth,   wherein said textile membrane having at least one hole such that the flow of air at said therapeutic pressure is delivered to at least the entrance to the patient&#39;s nares and/or to the entrance of the patient&#39;s mouth, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use,   wherein the textile membrane includes a first portion held in a relaxed state and a second portion held in a taut state, the taut state of the second portion configured to allow the seal-forming structure to include a three-dimensional shape having multiple curvatures.       

     In some aspects a) the at least one hole includes a naris opening configured to be positioned adjacent to the patient&#39;s nares, and an oral portion hole configured to be positioned adjacent the patient&#39;s mouth in use; b) a bridge portion extends across the naris opening and divides the naris opening into a first hole and a second hole, each of the first hole and the second hole configured to be positioned adjacent to one of the patients nares in use; c) the bridge portion is the second portion and is held in a taut state; and/or d) the bridge portion is crimped using ultrasonic welding and/or an adhesive. 
     In some aspects a) the first portion is at least partially comprised of the oral portion; b) the first portion includes the oral portion and a section of the nasal portion; c) the seal-forming structure further includes a flexible support structure for holding the textile membrane in the three-dimensional shape; d) the flexible support structure includes at least one support rib that engages the oral portion within the cavity of the plenum chamber; e) the flexible support structure further comprises a secondary rib disposed within the cavity, the support rib extending between the secondary rib and the oral portion; f) the textile membrane of the seal-forming structure is curved about at least two non-parallel axes as a result of taut state of the second portion in order to form the three-dimensional shape; g) the oral portion is curved about the at least two non-parallel axes; and/or h) the textile membrane includes a textile layer and a silicone layer coupled to the textile layer, the silicone layer having impermeable properties. 
     In some aspects a) the seal-forming structure is constructed from a textile membrane having a first sub-section and a second sub-section that is spaced apart from the first sub-section; b) the seal-forming structure further comprises a flexible support portion constructed from a material other than the textile membrane, the flexible support portion disposed between the first sub-section and the second sub-section; c) the second sub-section is positioned superior to the first sub-section in use; d) the second sub-section is disposed at least partially between ends of the first sub-section; e) the at least one hole includes a naris opening configured to be positioned adjacent to the patient&#39;s nares, and an oral portion hole configured to be positioned adjacent the patient&#39;s mouth, wherein, the first sub-section completely forms a perimeter of the oral portion hole; and the second sub-section completely forms a perimeter of the naris opening; f) the at least one hole includes a naris opening configured to be positioned adjacent to the patient&#39;s nares, and an oral portion hole configured to be positioned adjacent the patient&#39;s mouth, wherein, a perimeter of the naris opening is completely formed by the second sub-section; and a perimeter of the oral portion hole is at least partially formed by a combination of the first sub-section the second sub-section; g) the first sub-section forms at least part of the oral portion and includes an annular shape; and/or h) the second sub-section forms at least part of the oral portion and includes a U-shape. 
     In some aspects a) a single, continuous piece of the textile membrane is used to construct the oral portion and the nasal portion; b) the patient&#39;s nose and lip superior are configured to contact only the textile membrane, in use; and/or c) foam inserts coupled to the seal-forming structure and configured to contact the patient&#39;s nasal ala in use. 
     In some aspects, the textile membrane is configured to include be curved about at least two non-parallel axes as a result of the bridge portion being crimped. 
     In some aspects, the bridge portion is crimped using ultrasonic welding and/or an adhesive. 
     In some aspects, a length of the bridge portion is directly related to a size of the first hole and to a size of the second hole. 
     In some aspects, the bridge portion includes a first section and a second section, the first section being substantially flat and configured to contact the patient in use, and the second section extending into the plenum chamber. 
     In some aspects, ultrasonic welding and/or adhesives are applied to the second section. 
     In some aspects, the seal-forming structure includes a single wall, and wherein an end of the flexible support structure contacts the textile membrane. 
     In some aspects, the seal-forming structure includes a pair of walls, wherein the flexible support structure includes a free end, and the textile membrane is coupled to the flexible support structure distal to the free end, and wherein the free end is spaced apart from the textile membrane so that the textile membrane is arranged radially outside of the free end. 
     In some aspects, the flexible support structure is coupled to the textile membrane using injection molding. 
     In some aspects, the bridge portion is a locating spigot after being crimped. 
     In some aspects, the textile membrane includes a textile layer and a silicone layer coupled to the textile layer, the silicone layer having impermeable properties. 
     In some aspects, the silicone layer is approximately 0.5 mm thick. 
     In some aspects, the textile membrane includes a multi-layered textile material and silicone layer coupled to the multi-layered textile material. 
     In some aspects, the multi-layered textile material includes a first layer, a second layer, and a third layer, the silicone layer contacting only the first layer, and the third layer configured to contact the patient&#39;s face, in use. 
     In some aspects, the first layer and the third layer are constructed from nylon, and wherein the second layer is constructed from spandex. 
     In some aspects, the silicone layer is disposed within the cavity and is configured to not touch the patient&#39;s skin, in use. 
     In some aspects, the silicone layer has a low durometer characteristic, and the textile membrane includes a high stretch capability when coupled to the flexible support structure. 
     In some aspects, the textile membrane is approximately 0.35 mm to approximately 0.45 mm thick. 
     In some aspects, the textile membrane includes a first curvature about a first axis intersecting the first opening and the second opening, and wherein before being crimped, the bridge portion includes a bridge curvature about the first axis in an opposite direction from a remainder of the textile membrane. 
     In some aspects, a second axis extends transverse to the first axis and along the bridge portion, the textile membrane including a secondary curvature about the second axis. 
     In some aspects, the secondary curvature has an opposite concavity than the first curvature. 
     In some aspects, the secondary curvature is configured to contact the patient&#39;s subnasale, in use. 
     In some aspects, a third axis extends transverse to the second axis and skewed with respect to the first axis, the textile membrane including a tertiary curvature about the third axis. 
     In some aspects, the tertiary curvature is configured to contact the patient&#39;s lip superior, in use. 
     In some aspects, a fourth axis extends transverse to the second axis and to the third axis, and parallel to the first axis, the textile membrane including a quaternary curvature about the fourth axis. 
     In some aspects, the quaternary curvature includes a variable radius of curvature. 
     In some aspects, the quaternary curvature extends into the primary curvature proximate to an edge of the textile membrane. 
     In some aspects, a portion of the first hole distal to the bridge portion is movable between a first position and a second position. 
     In some aspects, the first position is a natural state, and the textile membrane moves to the second position as a result of an external force. 
     In some aspects, the portion of the first hole extends into the plenum chamber in the second position. 
     In some aspects, the first hole includes a substantially tear-drop shape in the second position. 
     In some aspects, in the second position, the first hole is configured to contact a periphery of the entrance to one of the patient&#39;s nares proximate to an alar rim. 
     In some aspects, a portion of the second hole distal to the bridge portion is movable between the first position and the second position. 
     In some aspects, the patient&#39;s nose and lip superior are configured to contact only the textile membrane, in use. 
     In some aspects, the patient interface is a nasal cushion, nasal cradle, oronasal cushion, ultra-compact full-face mask, or full-face mask. 
     In another aspect of the present invention, a patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to a patient&#39;s airways including at least entrance of a patient&#39;s nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient&#39;s respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: 
     a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and 
     a seal-forming structure having a textile membrane constructed and arranged to form a pressure-assisted seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways inferior to a nasal bridge region of the patient&#39;s face, said textile membrane having a first hole and a second hole and a bridge portion disposed between the first hole and the second hole, the first hole and the second hole formed therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient&#39;s nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use, 
     wherein:
         the seal-forming structure includes a flexible support structure to hold the textile membrane in a predefined curved shape, the textile membrane includes a first curvature about a first axis and a second curvature about a second axis generally transverse to the first axis, the first axis configured to be generally transverse to a sagittal plane of the patient&#39;s head so that the first curvature includes a vertex in a posterior direction so that the first curvature passes around the nasolabial sulcus of the patient&#39;s nose, and the second axis configured to be generally parallel with the sagittal plane so that the second curvature includes a vertex in an inferior direction so that the second curvature is a saddle region and has a generally a positive curvature with respect to the patient&#39;s lip superior in use,   the bridge portion has a third curvature opposite of the first curvature, the third curvature of the bridge portion limiting creasing along the surface of the textile membrane,   the textile membrane is coupled to the flexible support structure in a relaxed state,   in use, the textile membrane is configured to press against the patient&#39;s face such that the patient&#39;s nose is not received in the cavity, and   the textile membrane is attached to the flexible support structure along an outer perimeter of the textile membrane such that textile membrane extends radially inwardly beyond the support structure.       

     In some aspects, the bridge portion is crimped in order to maintain the third curvature and limit flipping to the first curvature. 
     In some aspects, the bridge portion is crimped using ultrasonic welding and/or an adhesive. 
     In some aspects, the textile membrane is substantially impermeable to air. 
     In some aspects, the textile membrane includes a textile layer and a silicone layer coupled to the textile layer, the silicone layer having impermeable properties. 
     In some aspects, the silicone layer is approximately 0.5 mm thick. 
     In some aspects, the silicone layer is disposed within the cavity and is configured to not touch the patient&#39;s skin, in use. 
     In some aspects, the silicone layer has a low durometer characteristic, and the textile layer includes a high stretch capability when coupled to the support structure. 
     In some aspects, the textile membrane is approximately 0.35 mm to approximately 0.45 mm thick. 
     In some aspects, the seal-forming structure includes a single wall, and wherein an end of the flexible support structure contacts the textile membrane. 
     In some aspects, the seal-forming includes a pair of walls, wherein the flexible support structure includes a free end, and the textile membrane is coupled to the flexible support structure distal to the free end, and wherein the free end is spaced apart from the textile membrane so that the textile membrane is arranged radially outside of the free end. 
     In some aspects, the first hole includes a first arched portion, the first arched portion having generally the first curvature, and the first arched portion is configured to be positioned within a first naris of the patient. 
     In some aspects, the first arched portion is configured to flip from having generally the first curvature to having generally the third curvature after being positioned within the first naris of the patient, the arched portion configured to wrap around a periphery of an entrance to the first naris. 
     In some aspects, the second hole includes a second arched portion, the second arched portion having generally the first curvature, and the second arched portion configured to be positioned within a second naris of the patient. 
     In some aspects, the first hole includes a substantially circular shape, and is configured to include a substantially tear-drop shape after contacting the patient&#39;s face. 
     In some aspects, the textile membrane is configured to contact only the patient&#39;s lip superior, subnasale, and pronasale, in use. 
     In some aspects, the flexible support is coupled to the textile membrane using injection molding. 
     In some aspects, the textile membrane includes a fourth curvature about a fourth axis, the fourth curvature being generally a saddle region with a positive curvature with respect to the patient&#39;s subnasale in use, and the fourth axis being generally transverse to the first axis and to the second axis. 
     In some aspects, an area influenced by the second curvature is formed by a generally rectangular region encompassing the first hole and the second hole, the generally rectangular region having a generally tangential relationship with respect to the first hole and to the second hole, wherein the generally tangential relationship limits creasing in the textile membrane. 
     In another aspect of the present technology, a patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to a patient&#39;s airways including at least entrance of a patient&#39;s nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient&#39;s respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: 
     a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and 
     a seal-forming structure having a textile membrane constructed and arranged to form a pressure-assisted seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways inferior to a nasal bridge region of the patient&#39;s face, said textile membrane having a first hole and a second hole and a bridge portion disposed between the first hole and the second hole, the first hole and the second hole formed therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient&#39;s nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use, 
     wherein:
         the seal-forming structure includes a flexible support structure to hold the textile membrane in a predefined curved shape, the textile membrane includes a first curvature about a first axis and a second curvature about a second axis generally transverse to the first axis, the first axis is configured to be generally transverse to a sagittal plane of the patient&#39;s head so that the first curvature includes a vertex in a posterior direction so that the first curvature is generally a negative dome curvature with respect to the patient&#39;s lip superior in use, and the second axis is configured to be generally parallel with the sagittal plane so that the second curvature includes a vertex in an inferior direction so that the second curvature is generally a saddle region and a positive curvature with respect to the patient&#39;s pronasale in use,   the bridge portion has a third curvature opposite of the first curvature, the third curvature of the bridge portion limiting creasing along the surface of the textile membrane,       

     the textile membrane is coupled to the flexible support structure in a relaxed state, 
     in use, the textile membrane is configured to press against the patient&#39;s face such that the patient&#39;s nose is not received in the cavity, and 
     the textile membrane is attached to the flexible support structure along an outer perimeter of the textile membrane such that textile membrane extends radially inwardly beyond the support structure. 
     In some aspects, the textile membrane includes a fourth curvature about a fourth axis configured to be generally parallel to the first axis so that the fourth curvature includes a vertex in the posterior direction so that the fourth curvature passes around the nasolabial sulcus of the patient&#39;s nose. 
     In some aspects, the bridge portion is crimped in order to maintain the third curvature and limit flipping to the first curvature. 
     In some aspects, the bridge portion is crimped using ultrasonic welding and/or an adhesive. 
     In some aspects, the textile membrane is substantially impermeable to air. 
     In some aspects, the textile membrane includes a textile layer and a silicone layer coupled to the textile layer, the silicone layer having impermeable properties. 
     In some aspects, the silicone layer is approximately 0.5 mm thick. 
     In some aspects, the silicone layer is disposed within the cavity and is configured to not touch the patient&#39;s skin, in use. 
     In some aspects, the silicone layer has a low durometer characteristic, and the textile layer includes a high stretch capability when coupled to the support structure. 
     In some aspects, the textile membrane is approximately 0.35 mm to approximately 0.45 mm thick. 
     In some aspects, the seal-forming structure includes a single wall, and wherein an end of the flexible support structure contacts the textile membrane. 
     In some aspects, the seal-forming includes a pair of walls, wherein the flexible support structure includes a free end, and the textile membrane is coupled to the flexible support structure distal to the free end, and wherein the free end is spaced apart from the textile membrane so that the textile membrane is arranged radially outside of the free end. 
     In some aspects, the first hole includes a first arched portion, the first arched portion having generally the first curvature, and the first arched portion is configured to be positioned within a first naris of the patient. 
     In another aspect of the present technology, a seal-forming structure has: 
     a textile membrane constructed and arranged to form a pressure-assisted seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways inferior to a nasal bridge region of the patient&#39;s face, said textile membrane having a first hole and a second hole and a bridge portion disposed between the first hole and the second hole, the first hole and the second hole formed therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient&#39;s nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use, and 
     a flexible support structure for holding the textile membrane in a predefined shape; 
     wherein: 
     the textile membrane is coupled to the flexible support structure in a relaxed state, and 
     the bridge portion is crimped so as to be held in greater tension than a remainder of the textile membrane. 
     Another aspect of the present technology is a patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to a patient&#39;s airways including at least entrance of a patient&#39;s nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient&#39;s respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: 
     a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and 
     a seal-forming structure having:
         a textile membrane constructed and arranged to form a pressure-assisted seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways inferior to a nasal bridge region of the patient&#39;s face, said textile membrane having a portion, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use,       

     wherein the textile membrane is held in a taut state. 
     One form of the present technology comprises a textile seal-forming structure with a bridge portion between a first hole and a second hole, the entire textile seal-forming structure being held in a taut state. 
     Another aspect of one form of the present technology is a seal-forming structure having a textile membrane coupled to a flexible support structure in a taut state, and a bridge portion of the textile membrane is substantially flat as a result of the tension. 
     Another aspect of one form of the present technology is a seal-forming structure having a textile membrane coupled to a flexible support structure in a taut state prior to use, the textile membrane having a substantially flat surface in at least one direction in the taut state prior to use. 
     In some aspects, the textile membrane is tensioned via various techniques, including without crimping at one or more portions of the textile membrane, e.g., a central portion and/or a bridge portion. The central portion and/or a bridge portion may be taut and substantially flat prior to use by a patient. The textile membrane may be supported by a flexible support and may be stretched, or otherwise tensioned, prior to connecting to flexible support. 
     Another aspect of one form of the present technology is a patient interface that is moulded or otherwise constructed with a perimeter shape which is complementary to that of an intended wearer. 
     An aspect of one form of the present technology is a method of manufacturing apparatus. 
     An aspect of certain forms of the present technology is a medical device that is easy to use, e.g. by a person who does not have medical training, by a person who has limited dexterity, vision or by a person with limited experience in using this type of medical device. 
     An aspect of one form of the present technology is a portable RPT device that may be carried by a person, e.g., around the home of the person. 
     An aspect of one form of the present technology is a patient interface that may be washed in a home of a patient, e.g., in soapy water, without requiring specialised cleaning equipment. An aspect of one form of the present technology is a humidifier tank that may be washed in a home of a patient, e.g., in soapy water, without requiring specialised cleaning equipment. 
     The methods, systems, devices and apparatus described may be implemented so as to improve the functionality of a processor, such as a processor of a specific purpose computer, respiratory monitor and/or a respiratory therapy apparatus. Moreover, the described methods, systems, devices and apparatus can provide improvements in the technological field of automated management, monitoring and/or treatment of respiratory conditions, including, for example, sleep disordered breathing. 
     Of course, portions of the aspects may form sub-aspects of the present technology. Also, various ones of the sub-aspects and/or aspects may be combined in various manners and also constitute additional aspects or sub-aspects of the present technology. 
     Other features of the technology will be apparent from consideration of the information contained in the following detailed description, abstract, drawings and claims. 
    
    
     
       4 BRIEF DESCRIPTION OF THE DRAWINGS 
       The present technology is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements including: 
       4.1 Respiratory Therapy Systems 
         FIG.  1 A  shows a system including a patient  1000  wearing a patient interface  3000 , in the form of nasal pillows, receiving a supply of air at positive pressure from an RPT device  4000 . Air from the RPT device  4000  is humidified in a humidifier  5000 , and passes along an air circuit  4170  to the patient  1000 . A bed partner  1100  is also shown. The patient is sleeping in a supine sleeping position. 
         FIG.  1 B  shows a system including a patient  1000  wearing a patient interface  3000 , in the form of a nasal mask, receiving a supply of air at positive pressure from an RPT device  4000 . Air from the RPT device is humidified in a humidifier  5000 , and passes along an air circuit  4170  to the patient  1000 . 
         FIG.  1 C  shows a system including a patient  1000  wearing a patient interface  3000 , in the form of a full-face mask, receiving a supply of air at positive pressure from an RPT device  4000 . Air from the RPT device is humidified in a humidifier  5000 , and passes along an air circuit  4170  to the patient  1000 . The patient is sleeping in a side sleeping position. 
     
    
    
     4.2 Respiratory System and Facial Anatomy 
       FIG.  2 A  shows an overview of a human respiratory system including the nasal and oral cavities, the larynx, vocal folds, oesophagus, trachea, bronchus, lung, alveolar sacs, heart and diaphragm. 
       FIG.  2 B  shows a view of a human upper airway including the nasal cavity, nasal bone, lateral nasal cartilage, greater alar cartilage, nostril, lip superior, lip inferior, larynx, hard palate, soft palate, oropharynx, tongue, epiglottis, vocal folds, oesophagus and trachea. 
       FIG.  2 C  is a front view of a face with several features of surface anatomy identified including the lip superior, upper vermilion, lower vermilion, lip inferior, mouth width, endocanthion, a nasal ala, nasolabial sulcus and cheilion. Also indicated are the directions superior, inferior, radially inward and radially outward. 
       FIG.  2 D  is a side view of a head with several features of surface anatomy identified including glabella, sellion, pronasale, subnasale, lip superior, lip inferior, supramenton, nasal ridge, alar crest point, otobasion superior and otobasion inferior. Also indicated are the directions superior &amp; inferior, and anterior &amp; posterior. 
       FIG.  2 E  is a further side view of a head. The approximate locations of the Frankfort horizontal and nasolabial angle are indicated. The coronal plane is also indicated. 
       FIG.  2 F  shows a base view of a nose with several features identified including naso-labial sulcus, lip inferior, upper Vermilion, naris, subnasale, columella, pronasale, the major axis of a naris and the midsagittal plane. 
       FIG.  2 G  shows a side view of the superficial features of a nose. 
       FIG.  2 H  shows subcutaneal structures of the nose, including lateral cartilage, septum cartilage, greater alar cartilage, lesser alar cartilage, sesamoid cartilage, nasal bone, epidermis, adipose tissue, frontal process of the maxilla and fibrofatty tissue. 
       FIG.  2 I  shows a medial dissection of a nose, approximately several millimeters from the midsagittal plane, amongst other things showing the septum cartilage and medial crus of greater alar cartilage. 
       FIG.  2 J  shows a front view of the bones of a skull including the frontal, nasal and zygomatic bones. Nasal concha are indicated, as are the maxilla, and mandible. 
       FIG.  2 K  shows a lateral view of a skull with the outline of the surface of a head, as well as several muscles. The following bones are shown: frontal, sphenoid, nasal, zygomatic, maxilla, mandible, parietal, temporal and occipital. The mental protuberance is indicated. The following muscles are shown: digastricus, masseter, sternocleidomastoid and trapezius. 
       FIG.  2 L  shows an anterolateral view of a nose. 
     4.3 Patient Interface 
       FIG.  3 A  shows a patient interface in the form of a nasal mask in accordance with one form of the present technology. 
       FIG.  3 B  shows a schematic of a cross-section through a structure at a point. An outward normal at the point is indicated. The curvature at the point has a positive sign, and a relatively large magnitude when compared to the magnitude of the curvature shown in  FIG.  3 C . 
       FIG.  3 C  shows a schematic of a cross-section through a structure at a point. An outward normal at the point is indicated. The curvature at the point has a positive sign, and a relatively small magnitude when compared to the magnitude of the curvature shown in  FIG.  3 B . 
       FIG.  3 D  shows a schematic of a cross-section through a structure at a point. An outward normal at the point is indicated. The curvature at the point has a value of zero. 
       FIG.  3 E  shows a schematic of a cross-section through a structure at a point. An outward normal at the point is indicated. The curvature at the point has a negative sign, and a relatively small magnitude when compared to the magnitude of the curvature shown in  FIG.  3 F . 
       FIG.  3 F  shows a schematic of a cross-section through a structure at a point. An outward normal at the point is indicated. The curvature at the point has a negative sign, and a relatively large magnitude when compared to the magnitude of the curvature shown in  FIG.  3 E . 
       FIG.  3 G  shows a cushion for a mask that includes two pillows. An exterior surface of the cushion is indicated. An edge of the surface is indicated. Dome and saddle regions are indicated. 
       FIG.  3 H  shows a cushion for a mask. An exterior surface of the cushion is indicated. An edge of the surface is indicated. A path on the surface between points A and B is indicated. A straight line distance between A and B is indicated. Two saddle regions and a dome region are indicated. 
       FIG.  3 I  shows the surface of a structure, with a one dimensional hole in the surface. The illustrated plane curve forms the boundary of a one dimensional hole. 
       FIG.  3 J  shows a cross-section through the structure of  FIG.  3 I . The illustrated surface bounds a two dimensional hole in the structure of  FIG.  3 I . 
       FIG.  3 K  shows a perspective view of the structure of  FIG.  3 I , including the two dimensional hole and the one dimensional hole. Also shown is the surface that bounds a two dimensional hole in the structure of  FIG.  3 I . 
       FIG.  3 L  shows a mask having an inflatable bladder as a cushion. 
       FIG.  3 M  shows a cross-section through the mask of  FIG.  3 L , and shows the interior surface of the bladder. The interior surface bounds the two dimensional hole in the mask. 
       FIG.  3 N  shows a further cross-section through the mask of  FIG.  3 L . The interior surface is also indicated. 
       FIG.  3 O  illustrates a left-hand rule. 
       FIG.  3 P  illustrates a right-hand rule. 
       FIG.  3 Q  shows a left ear, including the left ear helix. 
       FIG.  3 R  shows a right ear, including the right ear helix. 
       FIG.  3 S  shows a right-hand helix. 
       FIG.  3 T  shows a view of a mask, including the sign of the torsion of the space curve defined by the edge of the sealing membrane in different regions of the mask. 
       FIG.  3 U  shows a view of a plenum chamber  3200  showing a sagittal plane and a mid-contact plane. 
       FIG.  3 V  shows a view of a posterior of the plenum chamber of  FIG.  3 U . The direction of the view is normal to the mid-contact plane. The sagittal plane in  FIG.  3 V  bisects the plenum chamber into left-hand and right-hand sides. 
       FIG.  3 W  shows a cross-section through the plenum chamber of  FIG.  3 V , the cross-section being taken at the sagittal plane shown in  FIG.  3 V . A ‘mid-contact’ plane is shown. The mid-contact plane is perpendicular to the sagittal plane. The orientation of the mid-contact plane corresponds to the orientation of a chord  3210  which lies on the sagittal plane and just touches the cushion of the plenum chamber at two points on the sagittal plane: a superior point  3220  and an inferior point  3230 . Depending on the geometry of the cushion in this region, the mid-contact plane may be a tangent at both the superior and inferior points. 
       FIG.  3 X  shows the plenum chamber  3200  of  FIG.  3 U  in position for use on a face. The sagittal plane of the plenum chamber  3200  generally coincides with the midsagittal plane of the face when the plenum chamber is in position for use. The mid-contact plane corresponds generally to the ‘plane of the face’ when the plenum chamber is in position for use. In  FIG.  3 X  the plenum chamber  3200  is that of a nasal mask, and the superior point  3220  sits approximately on the sellion, while the inferior point  3230  sits on the lip superior. 
     4.4 RPT Device 
       FIG.  4 A  shows an RPT device in accordance with one form of the present technology. 
       FIG.  4 B  is a schematic diagram of the pneumatic path of an RPT device in accordance with one form of the present technology. The directions of upstream and downstream are indicated with reference to the blower and the patient interface. The blower is defined to be upstream of the patient interface and the patient interface is defined to be downstream of the blower, regardless of the actual flow direction at any particular moment. Items which are located within the pneumatic path between the blower and the patient interface are downstream of the blower and upstream of the patient interface. 
     4.5 Breathing Waveforms 
       FIG.  5    shows a model typical breath waveform of a person while sleeping. 
     4.6 Patient Interface According to the Present Technology 
       FIG.  6    is a perspective view of a patient interface according to an example of the present technology worn by a patient. 
       FIG.  7    is a perspective view of a patient interface according to another example of the present technology worn by a patient. 
       FIG.  8    is a cross-sectional view of the positioning and stabilising structure along the line  8 - 8  in  FIG.  7   . 
       FIG.  9    is an enlarged view of a portion of the positioning and stabilising structure of  FIG.  8   . 
       FIG.  10    is an enlarged view of a portion of the positioning and stabilising structure of  FIG.  8   . 
       FIG.  11    is a front view of the cushion assembly of  FIG.  6    positioned on a patient&#39;s face. 
       FIG.  12    is a front perspective view of a cushion assembly according to an example of the present technology. 
       FIG.  13    is a front view of the cushion assembly of  FIG.  12   . 
       FIG.  14    is a top perspective view of the cushion assembly of  FIG.  12   . 
       FIG.  15    is a top view of the cushion assembly of  FIG.  12   . 
       FIG.  16    is a cross-sectional view along the line  16 - 16  in  FIG.  12   . 
       FIG.  17    is a cross-sectional view along the line  17 - 17  in  FIG.  12   . 
       FIG.  18    is an enlarged detail taken from  FIG.  16   . 
       FIGS.  19 - 21    are front perspective views of cushion assemblies having grip pads disposed on the textile membrane according examples of the present technology. 
       FIG.  22    is a perspective view of a patient interface according to another example of the present technology. 
       FIG.  23    is a perspective view of the patient interface of  FIG.  22    worn by a patient. 
       FIG.  24    is a side view of the patient interface of  FIG.  23   . 
       FIG.  25    is a front perspective view of the patient interface of  FIG.  23   . 
       FIG.  26    is a front view of a cushion assembly of a patient interface in accordance to an example of the present technology. 
       FIG.  27    is a top view of the cushion assembly of  FIG.  26   . 
       FIG.  28    is a bottom view of the cushion assembly of  FIG.  26   . 
       FIG.  29    is a front perspective view of the cushion assembly of  FIG.  26   . 
       FIG.  30    is a rear perspective view of the cushion assembly of  FIG.  26   . 
       FIG.  31    is a side perspective view of the cushion assembly of  FIG.  26   . 
       FIG.  32    is a front perspective view of the cushion assembly of  FIG.  26    showing an interior portion of the cushion assembly. 
       FIG.  33    is a front view of the cushion assembly of  FIG.  26    showing an interior portion of the cushion assembly. 
       FIG.  33 - 1    is a rear perspective view of a cushion assembly according to an example of the present technology. 
       FIG.  33 - 2    is a rear perspective view of a cushion assembly according to an example of the present technology. 
       FIG.  33 - 3    is a rear perspective view of a cushion assembly according to an example of the present technology, where a sealing portion is constructed from a single piece of textile material. 
       FIG.  33 - 4    is a rear perspective view of the cushion assembly of  FIG.  33 - 3   , illustrating a more positively domed curvature of the sealing portion at a location configured to contact the patient&#39;s lip superior. 
       FIG.  33 - 5    is a top view of the cushion assembly of  FIG.  33 - 4   . 
       FIG.  33 - 6    is a side perspective view of the cushion assembly of  FIG.  33 - 3   , illustrating support ribs. 
       FIG.  33 - 7    is a side perspective view of the cushion assembly of  FIG.  33 - 3   , illustrating larger support ribs as compared to  FIG.  33 - 6   . 
       FIG.  33 - 8    is a rear perspective view of the cushion assembly of  FIG.  33 - 3    having a thicker corner of nose region in order to provide a narrower space to receive a patient&#39;s nose. 
       FIG.  33 - 9    is a top view of the cushion assembly of  FIG.  33 - 8   . 
       FIG.  33 - 10    is a front view of the cushion assembly of  FIG.  33 - 3   , illustrating raising a conduit connector portion as compared to the patient interface of  FIG.  24   . 
       FIG.  33 - 11    is a rear perspective view of the cushion assembly of  FIG.  33 - 3   , illustrating foam inserts configured to contact a patient&#39;s corner of nose region. 
       FIG.  34    is a rear view of a cushion assembly used with the patient interface of  FIG.  22   . 
       FIG.  35    is a front view of the cushion assembly of  FIG.  34   . 
       FIG.  36    is a cross-sectional view of the cushion assembly of  FIG.  34   , viewed along line  36 - 36 . 
       FIGS.  37 - 39    are front perspective views of cushion assemblies having grip pads disposed on the textile membrane according examples of the present technology. 
       FIG.  40    is a schematic illustration of a process of providing an air impermeable layer to a textile material according to an example of the present technology. 
       FIG.  40 - 1    is a schematic illustration a process of providing an air impermeable layer to a textile material according to another example of the present technology. 
       FIG.  41    is a schematic illustration depicting a patient&#39;s face being presented to a textile membrane in light tension prior to use. 
       FIG.  42    is a schematic illustration showing a resulting force exerted by the textile membrane on the patient&#39;s face due to tensile stress in the textile membrane. 
       FIG.  43    is a schematic illustration of tension forces exerted on the sealing portion of a cushion assembly according to an example of the present technology. 
       FIG.  44    is a schematic illustration of a force exerted by the textile membrane on the patient&#39;s face due to air pressure within the cavity formed by the cushion assembly. 
       FIGS.  45  and  46    depict a knitting process. 
       FIG.  47    illustrates a warp knitted textile according to an example of the present technology. 
       FIG.  48    illustrates a weft knitted textile according to an example of the present technology. 
       FIG.  49    is a perspective view of a textile material folded about a first axis. 
       FIG.  50    is a perspective view of the textile material of  FIG.  49   , folded about the first axis and a second axis. The second axis is non-parallel to the first axis, and a fold about the second axis creates a crease and/or wrinkle in the textile material. 
       FIG.  51    is a perspective view of a textile material for use as a seal-forming structure. The textile material is folded about three, non-parallel axes and treated in order to limit the creation of creases and/or wrinkles. 
       FIG.  52    is a perspective view of the textile material of  FIG.  49   , with a pair of openings cut into the material, and a bridge portion positioned between the two openings. 
       FIG.  53    is a perspective view of the textile material of  FIG.  52   , illustrating the bridge portion flipped about a second axis, parallel to the first axis. 
       FIG.  54    is a perspective view of the textile material of  FIG.  53   , illustrating the bridge portion under tension via a crimping process. 
       FIG.  55    is a perspective view of the textile material of  FIG.  53   , folded about non-parallel axes. Folding the bridge portion limits the creation of creases and/or wrinkles in the textile material. 
       FIG.  56    is a detail view of the textile material of  FIG.  55   , illustrating the curvatures about different axes. 
       FIG.  57    is a detail view of a textile material illustrating a circumference of the opening, which may be changed depending on the length of the bridge portion that is crimped. 
       FIG.  58    is a cross-sectional view of a cushion assembly formed with the textile material of  FIG.  54   . A flexible support structure contacts the textile material in order to form a single wall. 
       FIG.  59    is a cross-sectional view of a cushion assembly formed with the textile material of  FIG.  54   . A portion of a flexible support structure is spaced apart from the textile material in order to form two walls. 
       FIG.  60    is a perspective view of a cushion assembly formed with the textile material of  FIG.  54   . The textile material includes an arched portion partially surrounding the opening. 
       FIG.  61    is a perspective view of the cushion assembly of  FIG.  60   , illustrating the arched portion flipped inwardly so that the opening includes a substantially tear-dropped shape. 
     5 DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY 
     Before the present technology is described in further detail, it is to be understood that the technology is not limited to the particular examples described herein, which may vary. It is also to be understood that the terminology used in this disclosure is for the purpose of describing only the particular examples discussed herein, and is not intended to be limiting. 
     The following description is provided in relation to various examples which may share one or more common characteristics and/or features. It is to be understood that one or more features of any one example may be combinable with one or more features of another example or other examples. In addition, any single feature or combination of features in any of the examples may constitute a further example. 
     5.1 Therapy 
     In one form, the present technology comprises a method for treating a respiratory disorder comprising applying positive pressure to the entrance of the airways of a patient  1000 . 
     In certain examples of the present technology, a supply of air at positive pressure is provided to the nasal passages of the patient via one or both nares. 
     In certain examples of the present technology, mouth breathing is limited, restricted or prevented. 
     5.2 Respiratory Therapy Systems 
     In one form, the present technology comprises a respiratory therapy system for treating a respiratory disorder. The respiratory therapy system may comprise an RPT device  4000  for supplying a flow of air to the patient  1000  via an air circuit  4170  and a patient interface  3000 . 
     5.3 Patient Interface 
     A non-invasive patient interface  3000  in accordance with one aspect of the present technology comprises the following functional aspects: a seal-forming structure  3100 , a plenum chamber  3200 , a positioning and stabilising structure  3300 , a vent  3400 , one form of connection port  3600  for connection to air circuit  4170 , and a forehead support  3700 . In some forms a functional aspect may be provided by one or more physical components. In some forms, one physical component may provide one or more functional aspects. In use the seal-forming structure  3100  is arranged to surround an entrance to the airways of the patient so as to maintain positive pressure at the entrance(s) to the airways of the patient  1000 . The sealed patient interface  3000  is therefore suitable for delivery of positive pressure therapy. 
     If a patient interface is unable to comfortably deliver a minimum level of positive pressure to the airways, the patient interface may be unsuitable for respiratory pressure therapy. 
     The patient interface  3000  in accordance with one form of the present technology is constructed and arranged to be able to provide a supply of air at a positive pressure of at least 6 cmH 2 O with respect to ambient. 
     The patient interface  3000  in accordance with one form of the present technology is constructed and arranged to be able to provide a supply of air at a positive pressure of at least 10 cmH 2 O with respect to ambient. 
     The patient interface  3000  in accordance with one form of the present technology is constructed and arranged to be able to provide a supply of air at a positive pressure of at least 20 cmH 2 O with respect to ambient. 
     5.3.1 Seal-Forming Structure 
     In one form of the present technology, a seal-forming structure  3100  provides a target seal-forming region, and may additionally provide a cushioning function. The target seal-forming region is a region on the seal-forming structure  3100  where sealing may occur. The region where sealing actually occurs—the actual sealing surface—may change within a given treatment session, from day to day, and from patient to patient, depending on a range of factors including for example, where the patient interface was placed on the face, tension in the positioning and stabilising structure and the shape of a patient&#39;s face. 
     In one form the target seal-forming region is located on an outside surface of the seal-forming structure  3100 . 
     In certain forms of the present technology, the seal-forming structure  3100  is constructed from a biocompatible material, e.g. silicone rubber. 
     A seal-forming structure  3100  in accordance with the present technology may be constructed from a soft, flexible, resilient material such as silicone. 
     In some forms, such as those illustrated in  FIGS.  6  to  39   , the seal-forming structure  3100 ,  6100 ,  9100  has a sealing portion that comprises a textile material, which may cover the entirety or a portion of the seal-forming structure  3100 ,  6100 ,  9100 . In some forms, the textile may comprise a material formed of a network of fibres and be adapted such that it is air impermeable. For example, the textile may have an air impermeable film on at least one surface thereof thereby forming a textile membrane or textile sealing portion. 
     In some forms, the textile membrane may be constructed so as to stretch elastically in at least one dimension. For example, when a textile membrane is constructed from a network of fibres, the textile membrane may be capable of elongating in a longitudinal warp direction and/or a lateral weft direction across the textile membrane. In some forms, a textile membrane is constructed so as to elongate elastically to an extent greater than that achievable by conventional silicone seal-forming structures. 
     In some forms, the textile membrane is constructed so as to be substantially inelastic in at least one dimension. For example, when a textile membrane is constructed from a woven textile material, the textile membrane may be capable of substantially resisting elongation in either, or both of, a longitudinal warp direction or a lateral weft direction across the textile membrane. 
     The textile membrane may comprise a single layer or a plurality of layers. In forms where a plurality of layers are utilised, the individual layers can be formed using the same material, or a variety of different materials each with unique material properties. 
     In some forms, the textile membrane may comprise at least one layer that exhibits substantially air-impermeable characteristics, while maintaining the material characteristics necessary for providing comfort and minimal pressure points to the patient. For example, as illustrated in  FIG.  40   , in some forms a textile membrane may comprise an air impermeable material  10131  (e.g., a silicone layer) formed on one surface of a textile material  10133 . The air impermeable material  10131  can in some forms be laminated onto the textile material  10133 . The air impermeable material  10131  and textile material  10133  can, in some forms, be selected such that the resulting textile membrane  10135  can exhibit a predetermined overall elasticity, or a resistance to elasticity, as required. For example, the addition of the air impermeable material  10131  (or membrane layer) may add elasticity (or stretchiness) to the textile material  10133  such that the resulting textile membrane  10135  has increased stretchability. The air impermeable material  10131  may also have a low durometer characteristic so as not to impede on the elasticity of the textile material  10133 . In other words, the textile membrane  10135  will have substantially the same elasticity as the textile material  10133  does alone, so that the addition of the air impermeable material  10131  will not substantially reduce the elasticity (or stretchiness) of the textile material  10133 . 
     The air impermeable material  10131  may have a thickness substantially less than the thickness of the textile material  10133 . This may assist in maintaining a substantially light weight textile membrane  10135 , because the relatively small thickness of air impermeable material  10131  may not significantly add weight to the textile material  10133 . The patient interface with a textile membrane  10135  that includes the air impermeable material  10131  may not feel noticeably heavier than a patient interface that includes only the textile material  10133 . 
     In some examples, the thickness of the textile membrane  10135  is between approximately 0.25 mm and approximately 0.55 mm. In some examples, the thickness of the textile membrane  10135  is between approximately 0.30 mm and approximately 0.50 mm. In some examples, the thickness of the textile membrane  10135  is between approximately 0.35 mm and approximately 0.45 mm. In some examples, the thickness of the textile membrane  10135  is approximately 0.40 mm. 
     In some examples, the thickness of the air impermeable membrane  10131  is between approximately 0.01 mm and approximately 0.10 mm. In some examples, the thickness of the air impermeable membrane  10131  is between approximately 0.02 mm and approximately 0.08 mm. In some examples, the thickness of the air impermeable membrane  10131  is between approximately 0.03 mm and approximately 0.07 mm. In some examples, the thickness of the air impermeable membrane  10131  is between approximately 0.04 mm and approximately 0.06 mm. In some examples, the thickness of the air impermeable membrane  10131  is approximately 0.05 mm. 
     In some forms, the textile material  10133  may be formed as a multiple layered textile. In other words, multiple pieces of textiles may be combined together in order to form the overall textile material  10133 . As shown in  FIG.  40 - 1   , the textile material  10133  may be constructed from three layers (although any number of layers may be used). A second layer  10133   b  of the textile material  10133  may be sandwiched between a first layer  10133   a  and a third layer  10133   c . In the illustrated example, the second layer  10133   b  (i.e., the middle layer) is constructed from spandex, and the first and third layers  10133   a ,  10133   c  (i.e., inner and outer layers) are constructed from nylon. However, other materials may be used without departing from the scope and spirit of these forms. Additionally, the first and third layers  10133   a ,  10133   c  may be formed from different materials (i.e., non-identical materials). 
     In some forms, the overall composition of the textile material  10133  may be at least 50% nylon and at most 50% spandex. In some forms, the overall composition of the textile material  10133  may be between approximately 60% to approximately 90% nylon and between approximately 10% to approximately 40% spandex. In some forms, the overall composition of the textile material  10133  may be between approximately 70% to approximately 85% nylon and between approximately 15% to approximately 30% spandex. In some forms, the overall composition of the textile material  10133  may be approximately 82% nylon and approximately 18% spandex (e.g., JCD4018 produced by WeiMei Fabrics Limited). 
     In some forms, the layered structure may provide the textile material  10133  with a spongy feel. In other words, the textile material  10133  may be compliant and may deform as it comes in contact with the patient&#39;s face. Specifically, the thickness of the textile material  10133  may be capable of decreasing when a force is applied, and returning to its original shape when the force is removed. Thus, the textile material  10133  may act like a sponge because it is capable of at least partially absorbing an applied force. Specifically, the spandex layer  10133   b  of the textile material  10133  may provide the spongy feel (e.g., because of its elastic properties). The spongy feel of the textile material  10133  may help to improve comfort against a patient&#39;s skin (e.g., because the textile material  10133  is able to conform to a variety of facial contours). The spongy feel of the textile material  10133  may also assist in improving the seal against the patient&#39;s face. Particularly, the textile material  10133  may be able to deform into crevices on the patient&#39;s face (e.g., the region between the nasal ala and the nasolabial sulcus) as a result of an applied force (e.g., via a positioning and stabilizing structure  3300 ), but will not crease and form locations where air could leak out. This may assist the patient in establishing a seal between their skin and the textile membrane  10135 , without needing the textile membrane  10135  to contact the exact same location (e.g., which may make donning the seal-forming structure  3100  easier). This may also allow the seal-forming structure  3100 ,  6100 ,  9100  to move and/or shift while it is worn without creating a leak, because the spongy properties assist in maintaining the necessary contact against the patient&#39;s skin. 
     In some forms, the textile material  10133  is coated (e.g., laminated) with an air impermeable layer  10131  (e.g., liquid silicone rubber) in order to form a textile membrane  10135  with impermeable properties. In the illustrated example, the air impermeable layer  10131  is applied to a single side of the textile material  10133 . In other words, the air impermeable layer  10131  may be applied to the first layer  10133   a , but not to the second or third layers  10133   b ,  10133   c . When the textile membrane  10135  is constructed as a seal-forming structure  3100 ,  6100 ,  9100 , the first layer  10133   a  is configured to be positioned within a cavity  3101 ,  6001 ,  9001 , so that the third layer  10133   c  is configured to face and contact the patient. 
     In one form, the textile material  10133  is formed from a fine knit textile. Specifically, the first and third layers  10133   a ,  10133   c  are constructed with a fine knit. This may be a textile that is less than approximately 100 denier. This may be a textile that is less than approximately 50 denier. This may be a textile that is approximately 20 denier. The fine knit of the textile, particularly in the third layer  10133   c , provides a smooth feeling to the patient&#39;s skin, which may promote patient compliance (e.g., because of added comfort). The fine knit of the textile may also prevent seepage of the air impermeable layer  10131  through the textile layer  10133  (e.g., during a manufacturing process). For example, the fine knit of the first layer  10133   a  may limit all seepage, or may allow some seepage, but may substantially limit seepage into the other layers  10133   b ,  10133   c . In other words, the first layer  10133   a  acts as a barrier and substantially limits the air impermeable layer  10131  from contacting and/or coating the second layer  10133   b  or the third layer  10133   c . Since the first layer  10133   a  does not contact the patient, some seepage may be permitted since the relative stiffness of the first layer  10133   a  is less important to patient comfort than that of the third layer  10133   c  (i.e., which directly contacts the patient&#39;s skin). Thus, the spandex may not lose its elasticity as a result of contacting the air impermeable layer  10131 . Additionally, the third layer  10133   c  may not lose its smooth texture as a result of becoming impregnated with the air impermeable layer  10131 . And since only one surface of the textile material  10133  needs to be coated with the air impermeable material  10131  (i.e., for the textile membrane  10135  to have impermeable properties), an impermeable membrane  10135  may be constructed that does not substantially limit patient comfort. 
     In some embodiments, coating the textile material  10133  with the air impermeable material does not substantially affect the material properties of the textile membrane  10133 . For example, since the air impermeable material  10131  is substantially blocked from reaching the second layer  10133   b , the spandex that forms the second layer  10133   b  does not experience a substantial decrease in elasticity. This enables the textile membrane  10135  as a whole to continue to stretch as a result of an applied force. Additionally, the third layer  10133   c  may lose its ability to drape, and instead become stiff, if impregnated with the air impermeable layer  10131 . This may reduce the ability for the third layer  10133   c  to seal against a patient&#39;s face. Thus, in addition to comfort, blocking the air impermeable layer  10131  from the third layer  10133   c  keeps the third layer  10133   c  substantially loose, and capable of sealing against a patient&#39;s face. 
     In some embodiments, the air impermeable layer  10131  includes a thickness T I1  of no more than approximately 500 microns. In some embodiments, the air impermeable layer  10131  includes a thickness T I1  of between approximately 4 microns to approximately 400 microns. In some embodiments, the air impermeable layer  10131  includes a thickness T I1  of between approximately 8 microns to approximately 300 microns. In some embodiments, the air impermeable layer  10131  includes a thickness T I1  of between approximately 12 microns to approximately 200 microns. In some embodiments, the air impermeable layer  10131  includes a thickness T I1  of between approximately 16 microns to approximately 100 microns. In some embodiments, the air impermeable layer  10131  includes a thickness T I1  of between approximately 20 microns to approximately 70 microns. In some embodiments, the air impermeable layer  10131  includes a thickness T I1  of approximately 40 microns. 
     In some embodiments, the actual thickness T I2  of the air impermeable layer  10131  in the textile membrane  10135  may be less than the thickness T I1  of the air impermeable layer  10131  prior to being coated to the textile material  10133  (although this is not always the case). In other words, if the air impermeable material  10131  seeps into the first layer  10133   a , then the thickness T I1  of the air impermeable layer  10131  partially overlaps with the thickness of the first layer  10133   a , so that a thickness T I2  measured from an outer surface (i.e., surface facing the cavity) of the first layer  10133   a  to an exposed surface (i.e., surface facing the cavity) of the air impermeable layer  10131  is less than the total thickness T I1  of the air impermeable layer  10131 . 
     Even if the thickness T I2  of the air impermeable layer  10131  is less (e.g., because of seepage), the density remains substantially the same. In some embodiments, the air impermeable layer  10131  includes a density of no more than approximately 500 grams per meter squared (GSM). In some embodiments, the air impermeable layer  10131  includes a density of between approximately 5 GSM to approximately 400 GSM. In some embodiments, the air impermeable layer  10131  includes a density of between approximately 50 GSM to approximately 300 GSM. In some embodiments, the air impermeable layer  10131  includes a density of between approximately 100 GSM to approximately 200 GSM. In some embodiments, the air impermeable layer  10131  includes a density of between approximately 110 GSM to approximately 130 GSM. In some embodiments, the air impermeable layer  10131  includes a density of approximately 120 GSM. 
     The textile membrane  10135  includes a variety of benefits as a result of maintaining separation between the air impermeable layer  10131  and the second and third layers  10133   b  (i.e., the middle layer),  10133   c  (i.e., the patient contacting layer). As described above, the material properties of the textile material  10133  is not substantially sacrificed in order to achieve an impermeable membrane  10135 . The third layer in particular  10133  maintains a smooth surface texture in order to provide comfort to the patient, and the second layer  10133   b  does not substantially lose its elasticity. The first layer  10133   a , the third layer  10133   c , and the air impermeable layer  10131  may all also have elastic properties, so that they can stretch with the second layer  10133   b . In particular, the air impermeable layer may have a low durometer (e.g., between approximately 20 to approximately 40), which may provide it with more stretchiness (e.g., it does not substantially limit the ability of the textile material  10133  to stretch) as compared to an air impermeable layer  10131  with a greater durometer. 
     In other examples, the textile membrane  10135  in constructed entirely from a textile material  10133 . The textile material  10133  may include air impermeable threads that impart impermeability onto the textile membrane  10135 . The additional layer of air impermeable material  10131  may not be needed, which may allow the textile membrane  10135  to be thinner (i.e., just the thickness of the textile material). The air impermeable threads may have similar elastic properties to non-air impermeable threads, so that the textile membrane  10135  with the air impermeable threads does not lose stretchiness. 
     In some forms, the textile membrane  10135  can exhibit a low spring constant (i.e. high compliance) in both warp and weft. In such forms, unlike conventional designs where a fixed cushion may cause the skin of a patient&#39;s face  1300  to distort in order to form an effective seal, the textile material  10133  and/or the resulting textile membrane  10135  may have a material spring constant and spring length such that the textile membrane  10135  is more compliant than the patient&#39;s skin that engages the textile membrane  10135 . This may advantageously improve the comfort of the mask, and reduce the formation of localized pressure “hot spots,” or locations likely to result in irritation because of contact with the seal-forming structure  3100 ,  6100 ,  9100 . 
     In some forms, the surface of the textile material  10133  that contacts the patient&#39;s face  1300  can have low friction characteristics. This may advantageously improve the comfort of the surface texture of the textile membrane  10135  and reduce friction relative to the patient&#39;s face  1300 . The textile material  10133  may have a surface (e.g., herringbone) that may have a first coefficient of friction in a first direction that is different (e.g., greater or less) than a coefficient of friction in a second direction. In contrast, higher friction textiles may cause the textile membrane  10135  to grip or rub against contacted regions of the patient&#39;s face, in use. Such rubbing or gripping may cause the textile membrane  10135  to be distorted or deformed thereby reducing the effectiveness of the seal and allowing air to leak undesirably from the device. 
     In certain forms of the present technology, a system is provided comprising more than one a seal-forming structure  3100 , each being configured to correspond to a different size and/or shape range. For example the system may comprise one form of a seal-forming structure  3100  suitable for a large sized head, but not a small sized head and another suitable for a small sized head, but not a large sized head. 
     It is noted that although the specification may refer (e.g., by reference character) to a particular illustrated example or a feature of a particular illustrated example (e.g., seal-forming structure  3100 ), such discussion may be applicable to other examples and/or features (e.g., seal-forming structure  6100 ,  9100 ). 
     5.3.1.1 Sealing Mechanisms 
     In one form, the seal-forming structure includes a sealing flange utilizing a pressure assisted sealing mechanism. In use, the sealing flange can readily respond to a system positive pressure in the interior of the plenum chamber  3200  acting on its underside to urge it into tight sealing engagement with the face. The pressure assisted mechanism may act in conjunction with elastic tension in the positioning and stabilising structure. 
     In one form, the seal-forming structure  3100  comprises a sealing flange and a support flange. The sealing flange comprises a relatively thin member with a thickness of less than about 1 mm, for example about 0.25 mm to about 0.45 mm, which extends around the perimeter of the plenum chamber  3200 . Support flange may be relatively thicker than the sealing flange. The support flange is disposed between the sealing flange and the marginal edge of the plenum chamber  3200 , and extends at least part of the way around the perimeter. The support flange is or includes a spring-like element and functions to support the sealing flange from buckling in use. 
     In one form, a textile membrane  3130  (e.g., comprising nylon, polyester, nylon and polyester mix, microfiber or polyurethane) is used as the face-contacting portion of the seal-forming structure  3100  for the CPAP mask. The textile membrane  3130  may be bio-compliant, and may provide a substantially smooth and comfortable surface for the patient, which may improve patient compliance (e.g., because they are not wearing an irritating device). The textile membrane  3130  may have properties such that it is capable of elongating in at least one dimension. Prior to use, the textile membrane  3130  can be either permanently attached (e.g., molded) or attached as a removable module to a support structure (e.g., a flexible support structure  3120 ). 
     In one form, the textile membrane  3130  can be formed as a complex three-dimensional pre-determined shape such that it is untensioned (e.g., loose, slack and/or unwrinkled) prior to and/or during use, but there are no substantial leak causing wrinkles. The textile membrane  3130  may include one or more curvatures when attached to a support structure  3120 , which may assist in conforming to various contours of a patient&#39;s face. Before the patient&#39;s face (e.g., a nose) approaches and depresses the textile membrane  3130 , the textile membrane  3130  is adapted to form a constant surface without interruptions such as creases, folds or wrinkles. In some forms, this can be accomplished by molding the textile membrane  3130  such that it is substantially free of any leak causing wrinkles. This can be advantageous in ensuring that the textile membrane  3130  forms a smooth and continuous seal on and around the patient&#39;s face. This may provide improved respiratory pressure therapy by reducing occurrences of folded or wrinkled sections of the seal-forming structure  3100  through which treatment air may leak. 
     In some forms, regions of the textile membrane  3130  can be pre-tensioned (e.g., under tension before being contacted by the patient&#39;s face) and lightly stretched while other regions of the textile membrane  3130  can remain slack. In other words, the entire textile membrane  3130  may not be pre-tensioned. Having a textile membrane  3130  with various tensions may advantageously improve the seal efficiency while reducing pressure (i.e. “hot spots”) on regions where the facial anthropometrics protrude a greater distance into or towards the cavity  3101 . In some examples, the side of nose region (e.g., lateral side  3250  and/or corner regions  3252 ) may remain untensioned and/or slack prior to use, in order to provide additional material to accommodate the facial contours of these sensitive facial areas. In some examples, a bridge portion  3104  may extend between two naris openings  3102 , and may be tensioned, as shown for example in  FIG.  12 - 21   . The tension applied to the bridge portion  3104  may allow for one possible way for the textile membrane  3130  to include complex shapes (e.g., multiple curvatures) in order to better contour to a patient&#39;s face, while including significantly less tension throughout the remainder of the textile membrane  3130  (e.g., as compared to the bridge portion  3104 ). Having a wide expanse of untensioned textile membrane  3130  may be more comfortable in some arrangements, as the untensioned textile may apply less pressure on the patient&#39;s face. 
     By retaining the textile membrane  3130  in an unwrinkled state continuously prior to and during use, the textile membrane  3130  can conform to the patient&#39;s facial profile while minimizing wrinkles and/or blow-out of the seal-forming structure. In some forms, this may also improve seal performance by maximising the contact area of the textile membrane  3130  on the patient&#39;s face. In some forms, this may also improve the performance of the CPAP device when it is impacted by external lateral or longitudinal forces (e.g., tube drag). 
     In some forms, when the plenum chamber  3200  is pulled a small distance away from the patient&#39;s face, the applied loading of the air pressure from within the plenum chamber  3200  can assist the textile membrane  3130  in retaining an effective seal. The applied loading of the air pressure can be sufficient so as to elastically stretch the textile membrane  3130  in at least one dimension such that it forms a “hover-craft” like balloon effect over the anthropometric contours of a patient&#39;s face  1300  thus retaining an effective seal thereon. 
     In some forms, the textile membrane  3130  may be held by a relatively stiffer support structure  3120 . In various forms, the support structure  3120  can be formed from for example, any of silicone, PU foam, PU solid material or another suitable materials. While the support structure  3120  is stiffer than the textile membrane  3130 , it may still be described as flexible, and may be capable of flexing or bending as a result of an applied tension. In some forms, the support structure  3120  may be relatively less stiff than a shell or frame of the plenum chamber  3200  (e.g., that is formed from hard plastic). In other forms, the plenum chamber  3200  does not include a shell or frame, and is constructed entirely from the textile membrane  3130  and the support structure  3120 . 
     In some forms, a magnitude of the tensile stress can vary across the textile membrane  3130  of the seal-forming structure  3100  as required. The bridge portion  3104  may be held in tension, and the remainder of the textile membrane  3130  may be understood to be unstretched, as compared to the bridge portion  3104 . The bridge portion  3104  is illustrated as being in a central portion of the textile membrane  3130 , however the bridge portion  3104  (or any similar feature where tension is selectively applied), may be at any location throughout the textile membrane  3130 . However, different locations on the textile membrane  3130  may include different degrees of tension (i.e., but all less than the bridge portion  3104 ). For example, there may be a region of stress concentration proximal to one or more holes (e.g., naris openings  3102 ) in the textile membrane  3130  through which treatment is administered or in wider stretches of material. In some examples, the region of the textile membrane  3130  (e.g., outer periphery) directly connected to the support structure  3120  may be held in greater tension than the radially inner portions of the textile membrane  3130 , except for the bridge portion  3104 , which may include the highest tension. 
     In some forms, the seal-forming structure  3100  can utilize a number of different cushion configurations including a single air assisted textile membrane  3130 , a double air assisted textile membrane  3130 , a textile membrane  3130  with compression support, or a textile membrane  3130  with TPU/TPE/Si support. In some forms, the cushion configuration of the seal-forming structure  3100  may be formed such that it can advantageously provide a “one-size-fits-most” solution. 
     In examples, the seal-forming structure  3100  and plenum chamber  3200  can be applied to nasal cushions, nasal cradles, oronasal cushions, ultra-compact full-face masks, full-face masks and other suitable cushion arrangements. 
     In some forms, the textile membrane  3130  may be configured to generate an effective seal against the subnasale portion of the patients nose such that the textile membrane  3130  does not engage the pronasale, as shown for example in  FIG.  23   . In some forms, the textile membrane may be configured to generate an effective seal across the patient&#39;s pronasale (not shown). 
     In some forms, the air pressure within the cavity  3101  may apply a load against the inside surface of the textile membrane (e.g., an air impermeable layer  10131 ) to create further tensile stress such that the textile membrane  3130  substantially fills the depressed contours of a patient&#39;s face  1300  (e.g. around the nasal ala, adjacent to the alar rim, etc.). In some forms, the elasticity of the textile membrane  3130 , when combined with the applied load of the internal air pressure, can elastically stretch the textile membrane  3130  such that it forms a larger seal contact area on the patient&#39;s face. This may in some forms also be advantageous in providing a continuous seal, even when the mask is partially displaced from an optimal interface with the patient&#39;s face, as the textile membrane  3130  may partially inflate (i.e. a “hovercraft effect”) due to the counter-force from the internal air pressure. 
     In some forms, such as illustrated in  FIGS.  19 - 21  and  37 - 39   , the textile membrane  3130 ,  9130  may have one or more grip pads  3150 ,  9150  arranged thereon. In an example, the grip pads  3150 ,  9150  may be configured to be either substantially flat along the patient facing surface of the textile membrane  3130 ,  9130 . In other examples, the grip pads  3150 ,  9150  may be embossed such that the grip pad  3150 ,  9150  may form a bead or rim that protrudes slightly above the surface of the textile membrane  3130 ,  9130 . In some forms, the grip pads  3150 ,  9150  may have a high coefficient of friction. In some forms, the grip pads  3150 ,  9150  may have a determined shape (e.g., ovular (see  FIGS.  19 ,  21 ,  37 , and  39   ), circular, square, etc.). In some forms, the grip pads  3150 ,  9150  may be elongate (see  FIGS.  19  and  37   ). In some forms, the grip pads  3150 ,  9150  may be linear. In some forms, the grip pads  3150 ,  9150  may be arranged in a pattern across the surface of the seal-forming structure  3100 ,  9100 . In some forms, the grip pads  3150 ,  9150  may be arranged sporadically across the surface of the seal-forming structure  3100 ,  9100  (see  FIGS.  21  and  39   ). In some forms, the grip pads  3150 ,  9150  may be arranged to form a perimeter proximal to the peripheral edges of the textile membrane  3130 ,  9130  (see  FIGS.  19 ,  20 ,  37 , and  38   ). In some forms, the grip pads  3150 ,  9150  that form a perimeter can be in the form of a dotted line (see  FIGS.  19  and  37   ). In some forms, the grip pads  3150 ,  9150  that form a perimeter can be in the form of a solid line (see  FIGS.  20  and  38   ). In some forms, the grip pads  3150 ,  9150  that form a perimeter can be in the form of a plurality of lines, dotted or solid or a combination thereof. In some forms, the grip pads  3150 ,  9150  may assist a textile membrane  3130 ,  9130  in gripping a patient&#39;s face. In an example, the grip pads  3150 ,  9150  are formed as a relatively thin layer of silicone applied to the surface of the textile membrane  3130 ,  9130 . In any of the above configurations, the grip pads  3150 ,  9150  may provide an additional material (e.g., textile and silicone) that contacts the patient&#39;s face. While it may not provide the level of comfort that an entirely textile surface could provide (e.g., where only the textile material of the textile membrane contacts the patient&#39;s nose), including grip pads  3150 ,  9150  on the textile membrane  3130 ,  9130  may provide benefits of helping to ensure that the seal-forming structure  3100 ,  9100  remains in a proper position (e.g., in order to deliver therapeutic pressure to a patient). Additionally, having only a small area covered with silicone (or other gripping material) as compared to the relatively large area of textile (or being entirely silicone), may be more comfortable to a patient than an entire seal-forming structure  3100 ,  9100  formed from silicone (or other similar material). 
     In some forms, the textile membrane  3130  may be integrated to the support structure  3120  by attaching (e.g., molding) an outer edge (e.g., outer perimeter) of the textile membrane  3130  around a lip of the curved edges (i.e., inner edge) of the support structure  3120 . In an example, the textile membrane  3130  is attached so as to provide a front face of the seal-forming structure  3100 . The textile membrane  3130  also extends in the anterior direction, so that the textile membrane  3130  curves away from the front face. In other words, the textile membrane  3130  is curved so as to extend beyond the front face, and provides additional surface area of textile material exposed to the patient. This arrangement may be advantageous because substantially all of the patient&#39;s face in contact with the seal-forming structure  3100  is in contact with the textile membrane  3130 . This may be beneficial in improving patient compliance, because contact with the textile membrane  3130  may be more comfortable for a patient, and therefore the patient may be more likely to wear a patient interface  3000  that incorporates the textile membrane  3130 , than a patient interface  3000  that includes at least some other material (e.g., silicone) in a face contacting region. 
     In an example, the textile membrane  3130  is attached to the support structure  3120  by a specific process (as will be described later) that may form the curved portions without creating folds, creases, wrinkles, or buckles in the textile membrane surface  3130 . As can be seen, in some examples, at a transition portion  36 , the support structure  3120  and the textile membrane  3130  may both have a radius of curvature (e.g., the same or similar radius of curvature) along the curve  35  in a direction from the anterior side of the seal-forming structure  3100  to the posterior side of the seal-forming structure (see  FIGS.  16 - 18   ). The textile membrane  3130  may have a predefined curvature imparted thereto such that a portion of the textile membrane  3130  not directly supported by the support structure  3120  extends along the curve  35  ( FIGS.  16 - 18   ). The textile membrane  3130  may be held in slight tension against the support structure  3120 , but the textile membrane  3130  not directly supported by (e.g., not in direct contact with) the support structure  3120  may be considered to be substantially slack (e.g., and under less tension than the bridge portion  3104 ). This may help create a dome shape (e.g., convex dome) in certain regions (e.g., lateral side  3250  and/or corner regions  3252 ) of the textile membrane  3130  which may help the textile membrane  3130  seal against the contours of the patient&#39;s face (e.g., the subalare region of the patient&#39;s face (i.e., the corner of nose regions, i.e., the region where the ala terminate at the lip superior proximate the nasolabial sulcus)), as shown for example in  FIG.  12   . The dome shape may help prevent creases, wrinkles, folds, and buckles from forming in the textile membrane  3130  which may help avoid the creation of leak paths. Also, the dome shape may help the textile membrane  3130  reach into hard to seal areas of the patient&#39;s face, such as the corner of nose regions. The textile membrane  3130  may have a saddle shape at a medial subnasale region  3260  configured to seal against the patient&#39;s subnasale thereby matching the saddle shape formed by the patient&#39;s nasolabial angle and lip superior, as shown in  FIG.  12   . Similarly, a pronasale region  3270  may also have a saddle shape configured to seal against the matching profile presented at or below the patient&#39;s pronasale. The curvature (e.g., magnitude of curvature and/or radius of curvature) of the textile membrane  3130  in the direction of the curve  35  may vary in different regions of the cushion assembly along an outer perimeter of the textile membrane  3130 . For example, as shown in  FIG.  16   , the textile membrane  3130  in the medial pronasale region  3270  may have different curvature in the direction of the curve  35  than the textile membrane  3130  in the medial subnasale region  3260 . In an example, the curvature (e.g., magnitude of curvature and/or radius of curvature) at a lateral side  3250  of the textile membrane  3130  may be different that the curvature at the medial pronasale region  3270  and/or medial subnasale region  3260 . 
     In some forms, the textile membrane  3130  may be slightly angled or curved inwardly toward the mask interior (e.g., positive domed curvature in a left-right direction), as shown for example in  FIGS.  12 - 21   . In some forms, the textile membrane  3130  may form a dome shape over the support structure  3120 , as shown for example in  FIGS.  26 - 33   . It is noted that any of the cushion assemblies  6105 ,  9105  disclosed herein may have the textile membrane  6130 ,  9130  attached to an outer edge of the support structure  6120 ,  9120  such that the textile membrane  6130 ,  9130  forms part of the portion of the seal-forming structure  6100 ,  9100  that extends along the curve  35  from the anterior side of the seal-forming structure to the posterior face-contacting side as discussed above with reference to  FIG.  12   , such that, for example, the textile membrane  6130  of cushion assembly  6105  may have more of a dome shape by virtue of a negative curvature from one lateral side to the other lateral side. In other words, the textile membrane  6130  can be formed with both an inward curve and a dome shape, because the textile membrane  6130  is attached to the support structure  6120  with curvatures in different directions and/or about different axes. In one example, the majority of the textile membrane  6130  includes a positive (e.g., inward) curvature that may cradle a portion of the patient&#39;s face, and only the peripheries (e.g., regions proximate to the support structure) are dome shaped (e.g., include a negative curvature). 
     In some forms, a central portion of the textile membrane  3130  has a saddle shape. In other words, the peripheries of the textile membrane  3130  may be shaped with a negatively domed curvature (e.g., relative to the patient&#39;s face in use), and the central portion includes a positively domed curvature (e.g., about the bridge portion  3104 ), so that the central portion (e.g., proximate to the bridge portion  3104 ) may be considered a minimax point (e.g., relative to the patient&#39;s face in use), and thus a saddle. 
     In some forms where the textile membrane  3130  is not under continuous tension (prior to and/or during use) or is non-elastic, the textile membrane  3130  may form an improved air-assisted seal on a patient&#39;s face that conforms dynamically to alterations/movement (i.e. “hovercraft effect”), for example due to the textile membrane  3130  being thinner and having a lower structural stiffness than support structure  3120  (e.g., silicone membrane). 
     In some forms, the textile membrane  3130  may be supported by a secondary or tertiary support structure that may act as a cushion support. A cushion support can provide additional flexibility and may be suitable for use by most patient&#39;s faces (one-size-fits-most). The second or third support layer can be formed using a membrane of a textile, a textile with PU/Si membrane, laminated open cell foam, a laminated PU foam, PU molding, TPU/TPE or silicone. In some forms, additional support layers can themselves be supported by a structural/rigid plastic such as PP/PC/PA/PET or other suitable materials. 
     In some forms, 3D printing of the textile membrane and/or cushion support sections as a “skeleton” can reduce the thickness and as a consequence, may reduce the weight of the mask. 
     In some forms, multiple different layers of the mask layers could be printed with different rigidity, hardness, or thicknesses. For example, “skeleton” sections may be formed using Si, PU Foam, PU solid material or any suitable plastic material. 
     In one form, the seal-forming structure may comprise a compression sealing portion or a gasket sealing portion. In use the compression sealing portion, or the gasket sealing portion is constructed and arranged to be in compression, e.g. as a result of elastic tension in the positioning and stabilising structure. 
     In one form, the seal-forming structure comprises a tension portion. The tension portion may be located at any number of discrete locations throughout the seal-forming structure. In use, the tension portion is held in tension, e.g. by adjacent regions of the sealing flange. 
     In one form, the seal-forming structure comprises a region having a tacky or adhesive surface. 
     In certain forms of the present technology, a seal-forming structure may comprise one or more of a pressure-assisted sealing flange, a compression sealing portion, a gasket sealing portion, a tension portion, and a portion having a tacky or adhesive surface. 
     5.3.1.2 Nose Bridge or Nose Ridge Region 
     In one form, the non-invasive patient interface  3000  comprises a seal-forming structure that forms a seal in use on a nose bridge region or on a nose-ridge region of the patient&#39;s face. 
     In one form, the seal-forming structure includes a saddle-shaped region constructed to form a seal in use on a nose bridge region or on a nose-ridge region of the patient&#39;s face. 
     5.3.1.3 Upper Lip Region 
     In one form, the non-invasive patient interface  3000  comprises a seal-forming structure that forms a seal in use on an upper lip region (that is, the lip superior) of the patient&#39;s face. 
     In one form, the seal-forming structure includes a saddle-shaped region constructed to form a seal in use on an upper lip region of the patient&#39;s face. 
     5.3.1.4 Chin-Region 
     In one form the non-invasive patient interface  3000  comprises a seal-forming structure that forms a seal in use on a chin-region of the patient&#39;s face. 
     In one form, the seal-forming structure includes a saddle-shaped region constructed to form a seal in use on a chin-region of the patient&#39;s face. 
     5.3.1.5 Forehead Region 
     In one form, the seal-forming structure that forms a seal in use on a forehead region of the patient&#39;s face. In such a form, the plenum chamber may cover the eyes in use. 
     5.3.1.6 Nasal Pillows 
     In one form the seal-forming structure of the non-invasive patient interface  3000  comprises a pair of nasal puffs, or nasal pillows, each nasal puff or nasal pillow being constructed and arranged to form a seal with a respective naris of the nose of a patient. 
     Nasal pillows in accordance with an aspect of the present technology include: a frusto-cone, at least a portion of which forms a seal on an underside of the patient&#39;s nose, a stalk, a flexible region on the underside of the frusto-cone and connecting the frusto-cone to the stalk. In addition, the structure to which the nasal pillow of the present technology is connected includes a flexible region adjacent the base of the stalk. The flexible regions can act in concert to facilitate a universal joint structure that is accommodating of relative movement both displacement and angular of the frusto-cone and the structure to which the nasal pillow is connected. For example, the frusto-cone may be axially displaced towards the structure to which the stalk is connected. 
     5.3.2 Nasal Cushion 
     Referring to  FIGS.  6 - 21    a patient interface  3000  with a cushion assembly  3105  including a seal-forming structure  3100  and a plenum chamber  3200  is shown in accordance with a first example of the present technology. 
     The examples of seal-forming structure  3100  described in the preceding paragraph may be considered nasal cradle cushions and are intended to provide a flow of pressurised gas to the patient&#39;s nares by sealing against at least the underside of the patient&#39;s nose. The exemplary seal-forming structure  3100  may engage the patient&#39;s face below the bridge of the nose and some examples, depending on the size and shape of the patient&#39;s nose, may engage the patient&#39;s nose below the pronasale. The exemplary seal-forming structure  3100  may also engage the patient&#39;s face at least above the upper vermillion. Thus, the exemplary seal-forming structure  3100  may seal against the patient&#39;s lip superior in use. Furthermore, the patient&#39;s mouth may remain uncovered by the seal-forming structure  3100  of the depicted examples such that the patient may breathe freely, i.e., directly to atmosphere, without interference from the seal-forming structure  3100 . The under-the-nose nasal cradles may be configured such that they do not have an aperture sized to receive the patient&#39;s nose within the cavity. Further, a height of the cushion  3105  from an inferior edge of the textile membrane at a medial subnasale region to a superior edge of the textile membrane  3130  at a medial pronasale region may be less than a width of the cushion  3105  in a left-right direction from a lateral edge of the textile membrane  3130  to the other lateral edge of the textile membrane  3130  (see e.g.,  FIG.  12   ). 
     Examples of a nasal cradle cushion  3105 , e.g., the exemplary seal-forming structures  3100  disclosed herein, may include a superior saddle or concave region that has positive curvature across the cushion. Also, a nasal cradle cushion  3105  may be understood to have a single target seal forming region or surface, whereas a pillows cushion may have two target seal forming regions (one for each naris). Cradle cushions  3105  may also have a posterior wall that contacts the patient&#39;s lip superior and an upper, central, surface contacts the underside of the patient&#39;s nose (e.g., the patient&#39;s subnasale and/or columella). These two surfaces on the patient&#39;s face may form a nasolabial angle between them (see  FIG.  2 E ). A cradle cushion  3105  may be shaped to have a nasolabial angle within the range of 90 degrees to 120 degrees. 
     Furthermore, the exemplary seal-forming structure  3100  may also be shaped and dimensioned such that no portion of the seal-forming structure  3100  substantially enters into the patient&#39;s nares during use. In other words, a portion of the seal-forming structure  3100  may contact the alar rim and extend slightly inside in some orientations, but the seal-forming structure  3100  is not substantially sealing within the nasal passages (e.g., as opposed to a nasal pillow style mask). 
     5.3.2.1 Plenum Chamber 
     Referring to  FIGS.  6 - 21   , the plenum chamber  3200  has a perimeter that is shaped to be complementary to the surface contour of the face of an average person in the region where a seal will form in use. In use, a marginal edge of the plenum chamber  3200  is positioned in close proximity to an adjacent surface of the face. Actual contact with the face is provided by the seal-forming structure  3100 . The seal-forming structure  3100  may extend in use about any portion of the perimeter of the plenum chamber  3200  (e.g., about the entire perimeter, about a majority of the perimeter, etc.). 
     In certain forms of the present technology, the plenum chamber  3200  may be constructed from a flexible material (e.g., silicone) and may be formed as a one-piece structure with the support structure  3120  (e.g., from any of the materials described herein as suitable for the support structure  3120  and/or plenum chamber  3200 ). In some examples, the seal-forming structure  3100  may be an extension of the plenum chamber  3200  or formed as a part of the plenum chamber  3200  such that the plenum chamber  3200  encompasses the seal-forming structure  3100 . In such an example, the support structure  3120  and textile membrane  3130  may be considered part of the plenum chamber  3200  (e.g., the seal-forming structure  3100  at least partially forms the internal volume of the plenum chamber  3200 ). In some examples, the plenum chamber  3200  may be constructed from a transparent material (e.g. a transparent silicone). The use of a transparent material can reduce the obtrusiveness of the patient interface  3000 , and help improve compliance with therapy. The use of a transparent material can aid a clinician (or patient) in observing how the patient interface is located and functioning (e.g., to ensure a proper seal), and in observing the cleanliness of the patient interface  3000 . A transparent material may allow a clinician or patient to observe a build-up of debris (e.g., dirt, mold, etc.) within the plenum chamber  3200 , so that the patient interface  3000  can be cleaned or replaced. This may give the patient a sense of cleanliness when wearing the patient interface and may assist in ensuring that the patient is not inhaling harmful materials, both of which may improve patient compliance. A translucent material may be used instead of or in addition to a transparent material, and may provide the patient with similar benefits. Alternatively, the plenum chamber  3200  is constructed from a relatively rigid material (e.g., polycarbonate) as compared to the seal-forming structure  3100 . The rigid material may also be constructed from a transparent and/or translucent material (e.g., a transparent polycarbonate, etc.), in order to achieve the similar benefits of flexible transparent material (e.g., to allow for observation). 
     In some forms, the seal-forming structure  3100  may include a plenum chamber  3200  connection opening where the seal-forming structure  3100  is sealingly joined to the plenum chamber  3200 . The seal-forming structure  3100  and the plenum chamber  3200  may at least partly form a cavity  3101  that is pressurized by the flow of air. In the illustrated example, the seal-forming structure  3100  and the plenum chamber  3200  together form the cavity  3101 . At least one opening (e.g., a pair of nasal openings  3102 ) in the seal-forming structure may allow for fluid communication between the cavity  3101  and the patient&#39;s nares. However, the nasal openings  3102  are not large enough to allow the patient&#39;s nose (e.g., the pronasale) into the cavity  3101 . 
     The connection between the seal-forming structure  3100  and the plenum chamber  3200  at the plenum chamber connection opening  3106  may be a permanent bond. The connection between the seal-forming structure  3100  and the plenum chamber  3200  at the plenum chamber connection opening  3106  may be a chemical bond. The seal-forming structure  3100  may be joined to the plenum chamber  3200  at the plenum chamber  3200  connection opening without a mechanical connection. Alternatively, the seal-forming structure  3100  may be joined to the plenum chamber  3200  at the plenum chamber connection opening by a mechanical removably detachable connection. 
     At each lateral side of the plenum chamber  3200  there may be a plenum chamber lateral end  3202  in the form of a hollow passageway forming a plenum chamber inlet port sized and structured to receive a flow of air. A plenum chamber connector  3204  may also be provided at each lateral side of the plenum chamber  3200  laterally outward of the plenum chamber lateral end  3202 . The plenum chamber connectors  3204  may connect to respective ends  3314  of the positioning and stabilising structure  3300 . The connection between the plenum chamber connectors  3204  and respective ends  3314  of the positioning and stabilising structure  3300  may be releasable at both sides. In other examples, one side may have a permanent connection while the other side has a releasable connection. In still further examples, both connections between the plenum chamber connectors  3204  and respective ends  3314  of the positioning and stabilising structure  3300  may be permanent. 
     The plenum chamber lateral ends  3202  may receive the flow of pressurised gas from the positioning and stabilising structure  3300  (e.g., conduit headgear). The flow of pressurised gas may then pass through the plenum chamber  3200 , then through the seal-forming structure  3100 , and into the patient&#39;s airways for inhalation. 
     The ends  3314  of the positioning and stabilising structure  3300  (e.g., openings in the respective conduits) may be connected to the plenum chamber lateral ends  3202 . Each plenum chamber connector  3204  in these examples may include a slot  3209 , a chamfered edge  3208 , and a notch  3206  that may be removably connected to a clip of the positioning and stabilizing structure with a snap-fit. 
     5.3.2.2 Seal-Forming Structure of the Present Technology 
     The seal-forming structure  3100  may each include a support structure  3120  that provides support to a sealing portion  29130  (e.g., a textile membrane) that creates a seal with the patient&#39;s face. The sealing portion  29130  is configured to sealingly engage the patient&#39;s face (e.g., when pressurized air is supplied to the plenum chamber  3200 ). 
     In one example, the seal-forming structure  3100  may include a support structure having at least two regions (e.g., two, three, four, etc. regions) of different thickness (e.g., seal-forming structure  3100  comprises support structure  3120  which has a wall structure having lateral support regions  3122  of an increased thickness with respect to other portions of the wall structure). For example, as shown in  FIGS.  58  and  59   , some portions  3123  of the support structure  3120  may be thicker than other portions  3124 ,  3126  of the support structure  3120 . For example, the thicker portions  3123  may be adjacent to or connecting to the plenum chamber  3200  and portions  3124 ,  3126  may be adjacent to or connecting to the textile membrane  3130  so as to provide structural stability at the connection with the plenum chamber  3200  and flexibility at the interface with the patient. Alternatively, the thicker lateral support regions  3122  may be located, for example, at the corner of nose region of the seal-forming structure (and e.g., may connect directly to the textile membrane), to ensure adequate sealing in the subalare region of the patient&#39;s face. 
     Further, in the depicted examples, each textile membrane (e.g., sealing portion) may have two separate naris openings  3102  corresponding respectively to one of the patient&#39;s nares to provide the flow of air to both of the patient&#39;s nares. There may also be a bridge portion  3104  positioned between the naris openings  3102 . The bridge portion  3104  may assist in maintaining a desired shape of the textile membrane prior to and/or during use. 
     The sealing portion  3130  may be less rigid than the support structure  3120  and may be constructed from a textile material such as nylon, polyester, nylon and polyester mix, microfiber or polyurethane, for example, as will be described in more detail later. The sealing portion  3130  described in any of the examples of this disclosure may be referred to as a textile sealing portion or textile membrane and may comprise a textile material having an air impermeable property (e.g., a material layered, coated or otherwise applied thereon). 
     The support structure  3120  may have an aperture formed therein providing an inner edge of the support structure  3120  along which the sealing portion  3130  (e.g., an outer perimeter of the sealing portion  3130 ) may be attached to the support structure  3120  such that the sealing portion  3130  extends radially inwardly of the seal-forming structure  3100  beyond or to a further extent than the support structure, as shown for example in  FIGS.  12 - 21   . For example, the sealing portion  3130  may be molded around the inner edge of the support structure  3120  or connected to the support structure  3120  in other suitable ways, as will be described later. 
     Referring to  FIGS.  12 - 15   , the seal-forming portion  3100  has a wall structure that may include lateral support regions  3122  having an increased thickness as compared to other portions of the wall structure of the support structure  3120 . At each lateral most side of the seal-forming structure  3100 , a lateral support region  3122  may be provided. The seal-forming structure  3100  may include two lateral support regions  3122 , each spaced distal from a plane bisecting the seal-forming structure  3100  that would be parallel to the patient&#39;s sagittal plane, in use. The lateral support regions  3122  may be the thickest portions of the seal-forming structure  3100  to provide resistance to lateral displacement (e.g., caused by the patient sleeping on the side of their head such that the pillow pushes laterally against the seal-forming structure) and to provide robust engagement against the patient&#39;s ala. The lateral support regions  3122  may have a thickness of approximately 0.9 mm to approximately 1.5 mm, or approximately 1.3 mm to approximately 1.4 mm, or approximately 1.3 mm, or approximately 1 mm to approximately 1.5 mm. Due to the lateral support regions  3122  being the thickest regions of the seal-forming structure  3100  in the depicted examples, the lateral support regions  3122  may also provide the greatest resistance to deformation. 
     The textile membrane  3130  may be formed such that the textile membrane  3130  forms part of the portion of the seal-forming structure  3100  that curves from the anterior side of the seal-forming structure  3100  to the posterior face-contacting side, as described earlier. That is, the textile membrane  3130  is in contact with the support structure  3120  in the transition portion  36  such that the textile membrane portion  3130  may be configured to engage the subalare region of the patient&#39;s face (i.e., the region where the ala terminate at the lip superior proximate the nasolabial sulcus), which is a region of particularly complex geometry. The subalare region of a patient&#39;s face presents particularly complex geometry because at least three facial surfaces—the ala, the lip superior, and the cheek—converge at this region. As a result, the seal-forming structure  3100  may be more flexible and compliant (e.g., not under tension proximate the outer periphery of the textile membrane  3130 ) so as to more readily conform to the patient&#39;s facial contours. 
     As described earlier,  FIGS.  19 - 21    show grip pads  3150  on the surface of the textile membrane  3130 . 
     5.3.2.3 Positioning and Stabilising Structure 
     The seal-forming structure  3100  of the patient interface  3000  of the present technology may be held in sealing position in use by the positioning and stabilising structure  3300 . 
     In one form the positioning and stabilising structure  3300  provides a retention force at least sufficient to overcome the effect of the positive pressure in the plenum chamber  3200  to lift off the face. 
     In one form the positioning and stabilising structure  3300  provides a retention force to overcome the effect of the gravitational force on the patient interface  3000 . 
     In one form the positioning and stabilising structure  3300  provides a retention force as a safety margin to overcome the potential effect of disrupting forces on the patient interface  3000 , such as from tube drag, or accidental interference with the patient interface. 
     In one form of the present technology, a positioning and stabilising structure  3300  is provided that is configured in a manner consistent with being worn by a patient while sleeping. In one example the positioning and stabilising structure  3300  has a low profile, or cross-sectional thickness, to reduce the perceived or actual bulk of the apparatus. In one example, the positioning and stabilising structure  3300  comprises at least one strap having a rectangular cross-section. In one example the positioning and stabilising structure  3300  comprises at least one flat strap. 
     In one form of the present technology, a positioning and stabilising structure  3300  is provided that is configured so as not to be too large and bulky to prevent the patient from lying in a supine sleeping position with a back region of the patient&#39;s head on a pillow. 
     In one form of the present technology, a positioning and stabilising structure  3300  is provided that is configured so as not to be too large and bulky to prevent the patient from lying in a side sleeping position with a side region of the patient&#39;s head on a pillow. 
     In one form of the present technology, a positioning and stabilising structure  3300  is provided with a decoupling portion located between an anterior portion of the positioning and stabilising structure  3300 , and a posterior portion of the positioning and stabilising structure  3300 . The decoupling portion does not resist compression and may be, e.g. a flexible or floppy strap. The decoupling portion is constructed and arranged so that when the patient lies with their head on a pillow, the presence of the decoupling portion prevents a force on the posterior portion from being transmitted along the positioning and stabilising structure  3300  and disrupting the seal. 
     In one form of the present technology, a positioning and stabilising structure  3300  comprises a strap constructed from a laminate of a fabric patient-contacting layer, a foam inner layer and a fabric outer layer. In one form, the foam is porous to allow moisture, (e.g., sweat), to pass through the strap. In one form, the fabric outer layer comprises loop material to engage with a hook material portion. 
     In certain forms of the present technology, a positioning and stabilising structure  3300  comprises a strap that is extensible, e.g. resiliently extensible. For example the strap may be configured in use to be in tension, and to direct a force to draw a seal-forming structure  3100  into sealing contact with a portion of a patient&#39;s face. In an example the strap may be configured as a tie. 
     In one form of the present technology, the positioning and stabilising structure comprises a first tie, the first tie being constructed and arranged so that in use at least a portion of an inferior edge thereof passes superior to an otobasion superior of the patient&#39;s head and overlays a portion of a parietal bone without overlaying the occipital bone. 
     In one form of the present technology suitable for a nasal-only mask or for a full-face mask, the positioning and stabilising structure includes a second tie, the second tie being constructed and arranged so that in use at least a portion of a superior edge thereof passes inferior to an otobasion inferior of the patient&#39;s head and overlays or lies inferior to the occipital bone of the patient&#39;s head. 
     In one form of the present technology suitable for a nasal-only mask or for a full-face mask, the positioning and stabilising structure includes a third tie that is constructed and arranged to interconnect the first tie and the second tie to reduce a tendency of the first tie and the second tie to move apart from one another. 
     In certain forms of the present technology, a positioning and stabilising structure  3300  comprises a strap that is bendable and e.g. non-rigid. An advantage of this aspect is that the strap is more comfortable for a patient to lie upon while the patient is sleeping. 
     In certain forms of the present technology, a positioning and stabilising structure  3300  comprises a strap constructed to be breathable to allow moisture vapour to be transmitted through the strap. 
     In certain forms of the present technology, a system is provided comprising more than one positioning and stabilizing structure  3300 , each being configured to provide a retaining force to correspond to a different size and/or shape range. For example the system may comprise one form of positioning and stabilizing structure  3300  suitable for a large sized head, but not a small sized head, and another. suitable for a small sized head, but not a large sized head. 
     5.3.2.3.1 Positioning and Stabilising Structure of the Present Technology 
       FIG.  6    depicts an example of the present technology, including a positioning and stabilising structure  3300 . In this example, the positioning and stabilising structure  3300  includes lateral portions  3302  and superior portions  3304  in the form of conduits that direct a flow pressurised gas from a hub  3306  to ends  3314 . The positioning and stabilising structure  3300  may be arranged such that the hub  3306  and the decoupling structure  3500  are positioned superior to the patient&#39;s head in use. As described below, the decoupling structure  3500  may be rotatable within the hub  3306  and when the patient is wearing the patient interface  3000 , e.g., during therapy, the location of the hub  3306  and the decoupling structure  3500  superior to the patient&#39;s head allows the patient to move more freely without becoming entangled with the air circuit  4170 . 
     The positioning and stabilising structure  3300  may be constructed of silicone. For example, the lateral portions  3302 , the superior portions  3304 , the hub  3306 , and the lateral ends  3314  may able constructed or molded from a single piece of silicone. 
     The superior portions  3304  of the positioning and stabilising structure  3300  have ridges and valleys (or concertina sections) that allow the superior portions  3304  to conform to the shape of the corresponding portion of the patient&#39;s head in use. The ridges and valleys of the superior portions  3304  allow the superior portions  3304  to be extended and contracted along the longitudinal axis to accommodate larger or smaller heads. The ridges and valleys of the superior portions  3304  allow the superior portions  3304  to be flexed to different radii of curvature to accommodate patient heads of different shapes and sizes. 
     The lateral portions  3302  of the positioning and stabilising structure  3300  may not be formed with the ridges and valleys of the superior portions  3304 . Therefore, the lateral portions  3302  may be less extensible and flexible than the superior portions  3304 , which may be advantageous because there is less variability in the shape and size of the lateral sides of a patient&#39;s head. 
     The ends  3314  may connect to respective plenum chamber lateral ends  3202 . As described above, the plenum chamber lateral ends  3202  receive the flow of pressurised gas from the positioning and stabilising structure  3300 , which passes through the plenum chamber  3200 , through the seal-forming structure  3100 , and on to the patient&#39;s airways. As described above, the ends  3314  may connect to the plenum chamber connectors  3204  of a respective plenum chamber lateral end  3202 . 
     The positioning and stabilising structure  3300  may be structured and arranged to direct a force/tension provided by the lateral portions  3302  into a partially superior and partially posterior force vector applied to the plenum chamber  3200 . The partially superior and partially posterior force vector urges, in particular, the textile membrane of the seal forming structure  3100  into sealing contact with an underside of the patient&#39;s nose contacting, e.g., at or below the pronasale and at least above the upper vermillion. 
     The lateral portions  3302  may also each include a tab  3308  that receives a posterior strap end portion  3311  of a posterior strap  3310 . The posterior strap  3310  may be length-adjustable, e.g., with a hook and loop material arrangement whereby one of the posterior strap end portion  3311  and the remainder of the posterior strap  3310  includes hook material on its exterior while the other includes loop material on its exterior. The length adjustability of the posterior strap  3310  allows tension on the lateral portions  3302  to be increased to pull the seal-forming structure  3100  into sealing engagement with the patient&#39;s face at a desired amount of pressure (i.e., sufficiently tight to avoid leaks while not so tight as to cause discomfort). 
     The lateral portions  3302  may also be provided with sleeves  3312  that cushion the patient&#39;s face against the lateral portions  3302 . The sleeves  3312  may be constructed of a breathable textile material that has a soft feel. The sleeves  3312  may be removable from the lateral portions  3302  after the ends  3314  are removed from the plenum chamber lateral ends  3202 . 
     In some forms (see e.g.,  FIG.  7   ), a positioning and stabilizing structure  6300  may include a textile tube  6350  with a left arm  6305  and a right arm  6307 . The textile tube  6350  may be formed with a first side that is configured to contact the patient. This may be referred to as the inner layer  6352 . The textile conduit may also include a second side that is attached to the inner layer  6352 , but faces away from the patient that may be referred to as the outer layer  6354 . The inner layer  6352  and the outer layer  6354  may each be secured to each other along the edges of the inner layer  6352  and the outer layer  6354  such that a channel or passageway is formed between the seams of the inner layer  6352  and the outer layer  6354 . That is, the space between the seams remains unattached and forms an air passage  6372 . The inner layer  6352  and the outer layer  6354  may be joined using various techniques that impart particular properties to the seam or joint. For example, in some forms, the seams are formed using ultrasonic welding, radio frequency welding, as well as cut and weld techniques. Heat may be applied in particular areas that activates a thermoset or thermoplastic material used in tube  6350 . This heat may not only be used to join the layers together, but may also be used to thermoform the layers, such as outer layer  6354 . Further, in some forms stitching or an adhesive such as a glue may be utilized to join the layers together. In some forms, stitching is not used. In still further forms, material beyond what is located within the layers is not utilized to join the inner and outer layers  6352 ,  6354  of tube. For example, in some forms the inner and outer layers  6352 ,  6354  may be formed such that no additional material such as glue or stitching, is necessary to join the inner and outer layers  6352 ,  6354  together. 
     Each of the inner layer  6352  and the outer layer  6354  may include an interior surface and an exterior surface. The interior surface of the inner layer  6352  is the surface that faces the exterior layer  6354 . The interior surface of the exterior layer  6354  is the surface that faces the inner layer  6352 . Likewise, the exterior surface of the outer layer  6354  faces away from the inner layer  6352  and the exterior surface of the inner layer  6352  faces away from the outer layer  6354 . Further, in forms that include a single sheet, the interior surface is the surface of the sheet that faces inwards and towards itself. 
     In some forms, the sheet or sheets of the tube may include an air impermeable layer or membrane. In some forms, the interior surface of both of the layers includes a membrane that is configured to restrict or restrain air from passing through the layer from the interior surface to the exterior surface. The impermeable layer may be a thin layer that is less than the thickness of the textile sheets of the inner layer or outer layer. In other forms, the impermeable layer may be greater than the thickness of the sheets of textiles of either of the layers. The impermeable layer or membrane or film may be completely impermeable to air transfer or may be formed to allow a predetermined rate or air transfer and particular pressures. 
     The membrane may be formed of thermoplastic or thermoset materials such that when exposed to a particular temperature membrane material may be able to be molded or shaped into a particular form and then cures or solidifies or sets upon cooling. In some forms the membrane may be formed of silicone or polyurethane. In some forms, outer layer  6354  may be pre-formed such that in an unpressurized or supported state, outer layer  6354  is pre-positioned and pre-formed to extend away from inner layer  6352  between the opposing joints  6312 . That is, outer layer  6354  may support its own weight such that when not supported by pressurized air or other support mechanism, outer layer  6354  remains spaced from inner layer  6352  between joints  6312 . 
     In contrast, inner layer  6352  may be a floppy component. Inner layer  6352  may be attached and secured to the edges of outer layer  6354  such that inner layer  6352  is a substantially planar layer. 
     As shown in  FIG.  8   , and in particular  FIG.  9   , inner layer  6352  comprises a textile sheet  6360  along with membrane  6362 . Textile sheet  6360  may be formed of felt, foam, woven, knit, or non-woven material or other network of fibers. 
     Outer layer  6354  includes tube sheet  6364  and outer covering  6366 . In some forms, both sides of tube sheet  6364  may be covered with a membrane. As shown in  FIG.  10   , tube sheet  6364  includes membrane  6368  exposed to the chamber of tube  6350  and membrane  6370  along an opposite surface of tube sheet  6364 . membrane  6368  may assist in providing a seal between inner layer  6352  and outer layer  6354  as well as forming an air tight tube. Membrane  6370  may assist in joining tube sheet  6364  to outer covering  6366 . 
     5.3.2.4 Vent 
     In one form, the patient interface  3000  includes a vent  3400  constructed and arranged to allow for the washout of exhaled gases, e.g. carbon dioxide. 
     In certain forms the vent  3400  is configured to allow a continuous vent flow from an interior of the plenum chamber  3200  to ambient whilst the pressure within the plenum chamber is positive with respect to ambient. The vent  3400  is configured such that the vent flow rate has a magnitude sufficient to reduce rebreathing of exhaled CO 2  by the patient while maintaining the therapeutic pressure in the plenum chamber in use. 
     One form of vent  3400  in accordance with the present technology comprises a plurality of holes, for example, about 20 to about 80 holes, or about 40 to about 60 holes, or about 45 to about 55 holes. 
     The vent  3400  may be located in the plenum chamber  3200 . The vent  3400  may comprise a plurality of holes, as described above. The holes of the vent  3400  may be divided into two groups spaced apart laterally. The axis of the flow path through each of the holes of the vent  3400  may be parallel such that cross-flow is avoided to prevent generation of additional noise. The vent holes may be circular. 
     The holes of the vent  3400  may decrease in radius from the interior of the plenum chamber  3200  to the exterior. Each vent hole is provided with a draft angle. Each hole has a smaller diameter at its anterior end than at its posterior end. The draft angle means that the holes do not have a small cross section across the entire chassis thickness, which helps to provide effective carbon dioxide wash out at high levels of humidification. Additionally, a larger draft angle may result in a plenum chamber  3200  that is easier to manufacture, especially when the plenum chamber  3200  is formed from an injection moulded plastics material. The draft angle enables relatively thick vent pins to be used in the mould and easier ejection. 
     The holes of the vent  3400  may be provided in two sets towards the middle of the plenum chamber  3200  and the sets may be symmetrical across the centreline of the plenum chamber  3200 . Providing a pattern of multiple vent holes may reduce noise and diffuse the flow concentration. 
     The holes of the vent  3400  may be placed at an optimum distance away from the centreline of the plenum chamber  3200 . Placing the holes of the vent  3400  towards the centreline may advantageously reduce the chance that the vent holes are blocked when the patient is sleeping on their side. However, placing the vent holes too close to the middle of the plenum chamber  3200  may result in excessive weakening of the plenum chamber  3200  at the center, especially since the cross-section of the plenum chamber  3200  in the depicted examples is smallest at the center due to the overall shape of the plenum chamber  3200 . The location of the holes of the vent  3400  may avoid hole blockage during side sleep while leaving the middle section of the chassis sufficiently strong. 
     The size of each vent hole and the number of vent holes may be optimised to achieve a balance between noise reduction while achieving the necessary carbon dioxide washout, even at extreme humidification. In the depicted examples, the vent holes of the vent  3400  may not provide the total amount of venting for the system. The decoupling structure  3500  may include a decoupling structure vent  3402 . The decoupling structure vent  3402  may include one hole or a plurality of holes through the decoupling structure  3500 . The decoupling structure vent  3402  may function to bleed off excess pressure generated by the RPT device  4000  before reaching the patient, while the vent  3400  may function to washout carbon dioxide exhaled by the patient during therapy. 
     In some examples, a vent insert (not shown) attaches, removably or permanently, to the plenum chamber  3200  at a vent insert opening. The vent insert may be constructed from a material that is more flexible than the material of the plenum chamber  3200 . In one example, heat and moisture exchanging (HME) material (e.g., a foam) is housed in the removable vent, in order to humidify air the patient inhales, without the need for a separate humidifier. The vent insert may be removable in order to allow the patient to replace the HME material after a certain time period as past, with a fresh, clean sheet of HME material. In addition, the entire vent structure could be replaceable (e.g., as opposed to the HME material alone). 
     5.3.2.5 Decoupling Structure(s) 
     In one form the patient interface  3000  includes at least one decoupling structure, for example, a swivel or a ball and socket. 
     The hub  3306 , described above, is connected to a decoupling structure  3500 , which is a rotatable elbow in these examples. The decoupling structure  3500  may be rotatable 360° within the hub  3306  in use. The decoupling structure  3500  may be removable from the hub  3306  by manually depressing buttons  3504  to release catches (not shown) from within the hub  3306 . 
     The decoupling structure  3500  may also include a swivel  3502  that allows for rotatable connection to an air circuit  4170 . 
     The rotatability of the decoupling structure  3500 , the decoupling structure  3500  being in the form of an elbow, and the rotatability of the swivel  3502  on the decoupling structure  3500  may all increased the degrees of freedom, which in turn reduce tube drag and torque on the patient interface  3000  caused by the connection to the air circuit  4170 . 
     5.3.2.6 Connection Port 
     Connection port  3600  allows for connection to the air circuit  4170 . 
     5.3.2.7 Forehead Support 
     In one form, the patient interface  3000  includes a forehead support  3700 . 
     5.3.2.8 Anti-Asphyxia Valve 
     In one form, the patient interface  3000  includes an anti-asphyxia valve. 
     5.3.2.9 Ports 
     In one form of the present technology, a patient interface  3000  includes one or more ports that allow access to the volume within the plenum chamber  3200 . In one form this allows a clinician to supply supplementary oxygen. In one form, this allows for the direct measurement of a property of gases within the plenum chamber  3200 , such as the pressure. 
     5.3.3 Full Face Cushion 
     Referring to  FIGS.  26 - 33   , patient interface  6000  includes cushion assembly  6105  having a seal-forming structure  6100  that is configured to seal separately around the patient&#39;s nares and mouth (e.g., an oro-nasal cushion assembly or ultra-compact full face mask). The cushion assembly  6105  is at least partially formed by a plenum chamber  6200  and a seal-forming structure  6100  that is attached to the plenum chamber in accordance with an example of the present technology. 
     Referring to  FIGS.  22 - 25  and  34 - 39   , a cushion assembly  9105  is shown. Cushion assembly  9105  is similar to cushion assembly  6105  and has a seal-forming structure  9100  that is configured to seal separately around the patient&#39;s nares and mouth (e.g., an oro-nasal cushion assembly or ultra-compact full face mask). The cushion assembly  9105  is at least partially formed by a plenum chamber  9200  and a seal-forming structure  9100  that is attached to the plenum chamber in accordance with an example of the present technology. 
     The cushion assembly  9105  includes nasal portion  9101 , nasal portion holes  9103 , oral portion  9102 , oral portion hole  9104 , cavity  9001 , support structure  9120 , sealing portion  9130 , and vent  9400  which are similar to the features described in  FIG.  26 - 33   . The description of  FIGS.  26 - 33    may generally apply to  FIGS.  22 - 25  and  34 - 39   , and many similarities and differences not discussed separately. A pair of plenum chamber holes are configured to receive a flow of air. 
     The cushion assembly  9105  (e.g., specifically the nasal portion  9101 ) may include at least one curved surface as a result of the connection to the support structure  9120 . This curved surface may extend from an anterior to a posterior side of the cushion assembly  9105  (see e.g.,  FIG.  24   ). A similar curvature may be present on the cushion assembly  6105  (see e.g.,  FIGS.  30  and  31   ). However, unlike the cushion assembly  6105 , the cushion assembly  9105  (e.g., specifically the nasal portion  9101 ) may include at least one curved surface, which may be the result of a crimp in the nasal portion  9101 , which is described in more detail below. The curved surface of the cushion assembly  9105  resulting from the crimp may extend along a lateral direction of the patient&#39;s face (e.g., in the left-right direction) while the cushion assembly  9105  is in use. For example, the curved surface of the cushion assembly  9105  that results from the crimp may curve about an axis perpendicular to an axis through section line  36 - 36  (see e.g.,  FIG.  34   ), and/or about a third axis  13000  (described in detail below). The curved surface resulting from the crimp may also have a positive curvature relative to the patient&#39;s face. 
     As described earlier,  FIGS.  37 - 39    show grip pads  9150  on the surface of the textile membrane. The grip pads  9150  may be on the first sealing portion  9131  and/or the second sealing portion  9132 . Although illustrated with the cushion assembly  9105 , the grip pads  9150  may also be incorporated into the cushion assembly  6105 . 
     Referring to  FIG.  33 - 1   , patient interface  21000  includes a cushion assembly  21105  with a seal-forming structure  21100  that is configured to seal around the patient&#39;s nares and mouth (e.g., an oro-nasal cushion assembly or ultra-compact full face mask). The cushion assembly  21105  is similar to the cushion assemblies  6105  and  9105 . The cushion assembly  21105  is at least partially formed by a plenum chamber  21200  and the seal-forming structure  21100  that is attached to the plenum chamber in accordance with an example of the present technology. The seal-forming structure  21100  may also include a curved surface like the nasal portion  9101 . 
     Referring to  FIG.  33 - 2   , patient interface  23000  includes a cushion assembly  23105  with a seal-forming structure  23100  that is configured to seal around the patient&#39;s nares and mouth (e.g., an oro-nasal cushion assembly or ultra-compact full face mask). The cushion assembly  23105  is similar to the cushion assemblies  6105  and  9105 . The cushion assembly  23105  is at least partially formed by a plenum chamber  23200  and the seal-forming structure  23100  that is attached to the plenum chamber in accordance with an example of the present technology. The seal-forming structure  23100  may also include a curved surface like the nasal portion  9101 . 
     Referring to  FIGS.  33 - 3  to  33 - 11   , patient interface  25000  includes a cushion assembly  25105  with a seal-forming structure  25100  that is configured to seal around the patient&#39;s nares and mouth (e.g., an oro-nasal cushion assembly or ultra-compact full face mask). The cushion assembly  25105  is similar to the cushion assemblies  6105  and  9105 . The cushion assembly  25105  is at least partially formed by a plenum chamber  25200  and the seal-forming structure  25100  that is attached to the plenum chamber in accordance with an example of the present technology. The seal-forming structure  25100  may also include a curved surface like the nasal portion  9101 . 
     The full face cushions of  FIGS.  22 - 39    may have some similarities to the nasal cushion  3000  described above. For example, the seal-forming structures described in more detail below, may have tension selectively applied in order to assist in forming a resulting shape (e.g., a two-dimensional shape or a three-dimensional shape). Various similarities and differences between the full face cushions and the nasal cushion  3000  are described below. 
     5.3.3.1 Plenum Chamber 
     The plenum chamber  6200  has a perimeter that is shaped to be complementary to the surface contour of the face of an average person in the region where a seal will form in use. In use, a marginal edge of the plenum chamber  6200  is positioned in close proximity to an adjacent surface of the face. Actual contact with the face is provided by the seal-forming structure  6100 . The seal-forming structure  6100  may extend in use about the entire perimeter of the plenum chamber  6200 . 
     In certain forms of the present technology, the plenum chamber  6200  is constructed from a relatively rigid material (e.g., polycarbonate) as compared to the seal-forming structure  6100 . In another example, the plenum chamber  6200  is constructed from a flexible material (e.g., silicone, textile, etc.), and may have a similar rigidity as compared to the seal-forming structure  6100 . In another example, the plenum chamber  6200  may be constructed from a transparent material, e.g. a transparent polycarbonate. The use of a transparent material can reduce the obtrusiveness of the patient interface  6000 , and help improve compliance with therapy. The use of a transparent material can aid a clinician in observing how the patient interface  6000  is located and functioning and/or in observing any build-up of debris (e.g., dirt, mold, etc.). 
     In certain forms of the present technology, the plenum chamber  6200  is constructed from a translucent material. The use of a translucent material can reduce the obtrusiveness of the patient interface  6000 , and help improve compliance with therapy. 
     The plenum chamber  6200  according to examples of the present technology may include a plenum chamber hole on each lateral side. The plenum chamber hole may provide pneumatic communication between the conduit connectors  6800 , which are described in greater detail below, and the cavity  6001 . A connection rim portion around each plenum chamber hole may facilitate a mechanical connection, e.g., snap-fit or friction fit, with the respective conduit connector. The plenum chamber  6200  may be constructed of a sufficiently rigid material to provide audible and/or tactile feedback to the patient when the conduit connectors  6800  are connected to or removed from the plenum chamber  6200 . 
     The seal-forming structure  6100  may be sealingly connected to the plenum chamber  6200 . The connection may be permanent or the seal-forming structure  6100  may be removable from the plenum chamber  6200 . The seal-forming structure  6100  may be molded (e.g., overmoulded, injection molded, etc.) to the plenum chamber  6200 . The seal-forming structure  6100  and the plenum chamber  6200  may be joined by a mechanical connection in which no chemical bond is formed between the plenum chamber  6200  and the seal-forming structure  6100 . 
     5.3.3.2 Seal-Forming Structure 
     Referring to  FIGS.  26 - 33   , the seal-forming structure  6100  may include a nasal portion  6101  that has at least one hole (e.g., a pair of nasal portion holes  6103 ) to seal with, and convey pressurized air to, the patient&#39;s nares. The depicted examples provide two separate holes  6103  that each corresponds to one of the patient&#39;s nares to provide the flow of air to both of the patient&#39;s nares. There may also be a bridge portion  6106  positioned between the naris openings  6103 . In an alternative example, a single hole may be used to provide the flow of air to both of the patient&#39;s nares. A further alternative may include three or more holes. Unlike the bridge portion  3104 , the bridge portion  6106  may not be selectively tensioned. For example, the bridge portion  6106  and the surrounding material of the nasal portion  6101  may be held under tension together, instead of tension being applied only to the bridge portion  6106 . 
     Referring briefly to  FIGS.  22 - 25  and  34 - 39   , the bridge portion  9106  may be selectively tensioned in a similar manner as the bridge portion  3104 . For example, the bridge portion  9106  may be tauter than the surrounding first sealing portion  9131 . 
     With continued reference to  FIGS.  26 - 33   , the seal-forming structure  6100  may include an oral portion  6102  having an oral portion hole  6104  to seal with the patient&#39;s mouth. In some examples, the oral portion  6102  is held at least partially in tension (e.g., at any number of discrete locations) when not in use (i.e., when not contacting the patient&#39;s face). For example, the oral portion may be in tension at a join with the support structure  6120 , but relaxed on an exposed sealing edge (e.g., an inner edge proximate to an opening of the cavity  6001 ). In some examples, the oral portion  6102  is entirely in a relaxed state when not in use. In any of the examples, contact with the patient&#39;s face may stretch the oral portion  6102 , so that it is under tension while in use. 
     The seal-forming structure  6100  may at least partly form a cavity  6001  that is pressurized by the flow of air. The plenum chamber  6200  may be joined to the seal-forming structure  6100  to further form the cavity  6001 . 
     The seal-forming structure  6100  may include a support structure  6120  that provides support to a sealing portion  6130  (e.g., a textile membrane). The sealing portion is configured to sealingly engage the patient&#39;s face. The sealing portion  6130  is large enough (e.g., curves in the anterior direction a sufficient amount) so that only the sealing portion  6130  (e.g., only the textile membrane) may contact and sealingly engage a patient&#39;s face. Alternatively, the support structure  6120  may also be constructed from a textile material. 
     In one example, the seal-forming structure  6100  may include a support structure  6120  having at least two regions (e.g., two, three, or four regions) of different thickness (e.g., seal-forming structure  6100  comprises support structure  6120  which has a wall structure having lateral support regions (see e.g.,  3122  in  FIGS.  58  and  59   ) of an increased thickness with respect to other portions of the wall structure). For example, as shown in  FIGS.  58  and  59   , some portions  3123  of the support structure  3120  may be thicker than other portions  3124 ,  3126  of the support structure  3120 . For example, thicker portions  3123  may be adjacent to or connecting to the plenum chamber and portions  3124 ,  3126  may be adjacent to or connecting to the textile membrane  3130  so as to provide structural stability at the connection with the plenum chamber  3200  and flexibility at the interface with the patient. Alternatively, the thicker portions of the lateral support regions  3122  may be located, for example, at the corner of nose region of the seal-forming structure (and e.g., may connect directly to the textile membrane), to ensure adequate sealing in the subalare region of the patient&#39;s face. 
     As described above, the seal-forming structure  6100  may be sealingly connected to the plenum chamber  6200 . The support structure  6120  may be less rigid than the plenum chamber  6200  and may be constructed from silicone, foam (e.g., polyurethane foam), polyurethane solid material, thermoplastic elastomers (e.g., thermoplastic polyurethane), suitable plastics, or other suitable materials, as will be described later. Further, the sealing portion  6130  may be less rigid than the support structure  6120  and may be constructed from a textile material  6130  such as nylon, polyester, nylon and polyester mix, microfiber or polyurethane, for example, as will be described in more detail later. 
     In the example of  FIG.  32   , the support structure  6120  may extend into the cavity  6001  forming an underlying cushion  6121  to provide support to the sealing portion  14130 . The underlying cushion  6121  and the sealing portion  6130  may form a dual wall structure around the perimeter of sealing portion. In alternative examples, a second or third underlying cushion layer may be provided to form a triple or quadruple wall structure. In the example of  FIG.  32   , the underlying cushion is constructed of a foam material (e.g., polyurethane foam). In an alternative example, the underlying cushion  6122  may be constructed of silicone, as shown in  FIG.  33   . However, it will be recognized that the underlying cushion may be constructed from other suitable materials (e.g., textile). 
     The sealing portion  6130  may be constructed from two different pieces of a textile membrane. For example, one piece  6131  may be used to seal around the patient&#39;s nose, while a separate piece  6132  may be used to seal around the patient&#39;s mouth. The sealing portions  6131 ,  6132  may be used to independently seal around the respective orifice. In other words, the first or upper sealing portion  6131  may not contact the area around the patient&#39;s mouth, and the second or lower sealing portion  6132  may not contact the area around the patient&#39;s nose. 
     As shown in  FIGS.  26 - 33   , the first sealing portion  6131  is disposed in a superior portion (i.e., when in use) of the patient interface  6000  as compared to the second sealing portion  6132 . The first sealing portion  6131  forms a round (e.g., generally tri-oval) perimeter that seals around the patient&#39;s nares while in use. 
     In some forms, the first sealing portion  6131  may contact a region between the nasal ala and the lip superior, while leaving the pronasale exposed (see e.g.,  FIGS.  23 - 25    illustrating the similar first sealing portion  9131 ). The textile membrane of the first sealing portion  6131  may be the only material of the seal-forming structure  6100  to contact the patient in this region. In other words, the second sealing portion  6132  and the support structure  6120  do not contact the patient in this region. This may assist in improving patient compliance because the patient may only contact a textile layer in this region of their face, which they may more closely associate with bedclothes, instead of a medical device. 
     The second sealing portion  6132  is disposed in an inferior portion (i.e., when in use and as compared to the first sealing portion  6131 ) of the patient interface  6000 . In the illustrated example, the second sealing portion  6132  forms a generally U-shape, and seals around a portion of the patient&#39;s mouth. The textile membrane that forms the second sealing portion  6132  does not extend completely around the patient&#39;s mouth. In other words, a material other than the textile membrane may contact the patient in order to form a seal around the patient&#39;s mouth. In this example, the support structure  6120  (e.g., a silicone material) is molded between free ends of the second sealing portion  6132  in order to complete an oral portion hole  6104 . The textile membrane of the second sealing portion  6132  may contact the patient&#39;s lip inferior, a region outside the patient&#39;s cheillion, and a portion of the patient&#39;s lip superior, and may not contact the central portion of the patient&#39;s lip superior (e.g., proximate to the patient&#39;s philtrum). The support structure  6120  extends across the patient&#39;s philtrum, between the ends of the second sealing portion  6132 . A combination of the textile membrane of the sealing portion  6130  and the silicone material of the support structure  6120  may be responsible for creating a seal around the patient&#39;s mouth. 
     The support structure  6120  extends from a lower surface of the first sealing portion  6131  to an opening of the cavity  6001 . In other words, the first sealing portion  6131  is separated from the second sealing portion  6132  by the support structure  6120 . The material (e.g., silicone) of the support structure  6120  also assists in coupling the first sealing portion  6131  and the second sealing portion  6132  to each other during the manufacturing process. 
     As shown in  FIG.  33 - 1   , the second sealing portion  21130   b  extends completely around the patient&#39;s mouth. In other words, textile membrane contacts the philtrum as opposed to the support structure  21120 . The support structure  21120  (e.g., silicone material) is disposed in the inferior/superior direction between the first and second sealing portions  21130   a ,  21130   b  (e.g., first and second sub-sections). The support structure  21120  may slightly contact the patient&#39;s lip superior, although sealing is accomplished primarily or exclusively via the textile membrane in the first and second sealing portions  21130   a ,  21130   b . In other words, a location where support structure  21120  contacts the patient&#39;s skin may be unpressurized and/or exposed to ambient during therapy. Having the second support structure  21130   b  extend all the way around the patient&#39;s mouth may provide the patient with more comfort as compared with the U-shaped second sealing structure  21130   b  (e.g., because the patient may find the textile membrane more comfortable than the silicone), which may increase the patient&#39;s compliance with the therapy. 
     In another example of the patient interface  23000 , as shown in  FIG.  33 - 2   , the second sealing portion  23130   b  is U-shaped. However, the philtrum and central portion of the lip superior are contacted by textile membrane. In this example, the first sealing portion  23130   a  extends down to an edge of the oral portion hole  23104 . In other words, the first sealing portion  23130   a  is responsible for forming the seal around the patient&#39;s nose, and is also partially responsible for forming the seal around the patient&#39;s mouth. The U-shaped second sealing portion  23130   b  extends substantially around the remainder of the patient&#39;s mouth (although a small portion of the support structure  23120  is disposed laterally between the first and second sealing portions  23130   a ,  23130   b  in the left/right direction). This example may provide similar comfort benefits as described above with respect to  FIG.  33 - 1    (e.g., because substantially all of the patient&#39;s nose and mouth contact by the patient interface  23000  is contacted by the textile membrane). However, the example of  FIG.  33 - 2    may be easier to manufacture because the support material  23120  between the first and second seal portions  23130   a ,  23130   b  is removed in the superior/inferior direction. The small portions of the support structure  23120  between the sealing portions  23130   a ,  23130   b  may assist in forming the pressurized volume around the patient&#39;s mouth. 
     In other example of the patient interface  25000 , as shown in  FIG.  33 - 3   , the sealing portion  25130  is formed from a single piece of textile material. In other words, the first and second sealing portions  25130   a ,  25130   b  are not constructed from separate pieces of material. The single piece of material that forms the sealing portion  25130  is responsible for forming a seal around both the patient&#39;s nose and the patient&#39;s mouth. The sealing portion  25130  may have a similar outer perimeter as described above (e.g., in examples of the patient interface  25000  having first and second sealing portions  25130 ). In some examples, the sealing portion  25130  may only seal around its outer perimeter, since not sealing against the patient&#39;s lip superior may not allow air to leak out of the seal-forming structure  25100 . However, the sealing portion  25130  may still seal against the patient&#39;s lip superior so that pressurized air is more directly delivered to the patient&#39;s airways. By using a single piece of textile membrane to form the sealing portion  25130 , the support structure  25120  may not contact the patient&#39;s upper lip. Additionally, manufacturing the patient interface may be easier because the thin strip of support structure  25120  no longer needs to be formed between two pieces of textile membrane to connect them together. Thus, the molding process may be simplified so that small amounts of a material like silicone do not need to flow between, but not cover a textile layer  10133 . 
     As shown in  FIGS.  22  to  25  and  31 - 1  to  39   , the respective seal forming structures may all have a three-dimensional shape. Specifically, the respective first sealing portions may have a curved surface (e.g., in left-right direction), as opposed to the flat surface (e.g., in the left-right direction) shown in  FIGS.  26 - 33   . The three-dimensional shape may be formed, at least in part, by selectively applying tension to the bridge portion of the respective first sealing portion. Tension may not be applied to the material of the first sealing portion surrounding the bridge portion on the respective seal forming structures so that the first sealing portion may include a curved shape. 
     In any of these embodiments (e.g.,  FIGS.  22 - 39   ), the strength of the seal against the patient&#39;s face is substantially the same. For example, having textile material alone, or a combination of textile and silicone material does not substantially effect the quality of the seal (i.e., increase or decrease areas of leak). Different patients (e.g., different facial geometries) may be better suited for one of the particular examples over the others (e.g., because of comfort, fit, etc.). Additionally, while examples with more textile coverage may provide additional comfort to the patient, the added comfort may be minimal (e.g., since the support structure  6120  provides minimal contact in examples with both the first and second sealing portions  6131 ,  6132 ). 
     5.3.3.3 Positioning and Stabilising Structure 
     The seal-forming structure  9100  of the patient interface  9000  of the present technology may be held in sealing position in use by the positioning and stabilising structure  9300 . While the positioning and stabilizing structure  9300  is specifically shown with the patient interface  9000 , it may be used with any of the full face cushions (e.g., any example in  FIGS.  22 - 39   ). The positioning and stabilizing structure  9300  may also be similar to the positioning and stabilizing structure  3300 . 
     In one form the positioning and stabilising structure  9300  provides a retention force at least sufficient to overcome the effect of the positive pressure in the cavity  9001  to lift off the face. 
     In one form the positioning and stabilising structure  9300  provides a retention force to overcome the effect of the gravitational force on the patient interface  9000 . 
     In one form the positioning and stabilising structure  9300  provides a retention force as a safety margin to overcome the potential effect of disrupting forces on the patient interface  9000 , such as from tube drag, or accidental interference with the patient interface. 
     In one form of the present technology, a positioning and stabilising structure  9300  is provided that is configured in a manner consistent with being worn by a patient while sleeping. In one example the positioning and stabilising structure  9300  has a low profile, or cross-sectional thickness, to reduce the perceived or actual bulk of the apparatus. In one example, the positioning and stabilising structure  9300  comprises at least one strap having a rectangular cross-section. In one example the positioning and stabilising structure  9300  comprises at least one flat strap. 
     In one form of the present technology, a positioning and stabilising structure  9300  is provided that is configured so as not to be too large and bulky to prevent the patient from lying in a supine sleeping position with a back region of the patient&#39;s head on a pillow. 
     In one form of the present technology, a positioning and stabilising structure  9300  is provided that is configured so as not to be too large and bulky to prevent the patient from lying in a side sleeping position with a side region of the patient&#39;s head on a pillow. 
     In one form of the present technology, a positioning and stabilising structure  9300  is provided with a decoupling portion located between an anterior portion of the positioning and stabilising structure  9300 , and a posterior portion of the positioning and stabilising structure  9300 . The decoupling portion does not resist compression and may be, e.g. a flexible or floppy strap. The decoupling portion is constructed and arranged so that when the patient lies with their head on a pillow, the presence of the decoupling portion prevents a force on the posterior portion from being transmitted along the positioning and stabilising structure  9300  and disrupting the seal. 
     In one form of the present technology, a positioning and stabilising structure  9300  comprises a strap constructed from a laminate of a fabric patient-contacting layer, a foam inner layer and a fabric outer layer. In one form, the foam is porous to allow moisture, (e.g., sweat), to pass through the strap. In one form, the fabric outer layer comprises loop material to engage with a hook material portion. In one form, conduits  9900  for delivering air to the cushion assembly  9105  may also make up the positioning and stabilizing structure  9100 . 
     In certain forms of the present technology, a positioning and stabilising structure  9300  comprises a strap that is extensible, e.g. resiliently extensible. For example the strap may be configured in use to be in tension, and to direct a force to draw a seal-forming structure into sealing contact with a portion of a patient&#39;s face. In an example the strap may be configured as a tie. 
     In one form of the present technology, the positioning and stabilising structure may include a first tie (e.g., upper strap  9302  ( FIG.  24   )), the first tie being constructed and arranged so that in use at least a portion of an inferior edge thereof passes superior to an otobasion superior of the patient&#39;s head. 
     In one form of the present technology suitable for a full-face mask, the positioning and stabilising structure includes a second tie (e.g., lower strap  9303  (FIG.  24 )), the second tie being constructed and arranged so that in use at least a portion of a superior edge thereof passes inferior to an otobasion inferior of the patient&#39;s head and overlays or lies inferior to the occipital bone of the patient&#39;s head. 
     In one form of the present technology suitable for a nasal-only mask or for a full-face mask, the positioning and stabilising structure includes a third tie (e.g., strap connector  9304  ( FIG.  22   )) that is constructed and arranged to interconnect the first tie and the second tie to reduce a tendency of the first tie and the second tie to move apart from one another. 
     In certain forms of the present technology, a positioning and stabilising structure  9300  comprises a strap that is bendable and e.g. non-rigid. An advantage of this aspect is that the strap is more comfortable for a patient to lie upon while the patient is sleeping. 
     In certain forms of the present technology, a positioning and stabilising structure  9300  comprises a strap constructed to be breathable to allow moisture vapour to be transmitted through the strap, 
     In certain forms of the present technology, a system is provided comprising more than one positioning and stabilizing structure  9300 , each being configured to provide a retaining force to correspond to a different size and/or shape range. For example, the system may comprise one form of positioning and stabilizing structure  9300  suitable for a large sized head, but not a small sized head, and another suitable for a small sized head, but not a large sized head. 
     The positioning and stabilising structure  9300  may include a clip  9301  to secure respective ties, e.g., to the conduit connectors  9800  as shown in  FIG.  22   . The clip  9301  and the conduit connector  9800  may each include a magnet arranged with opposing polarities to facilitate a connection therebetween. 
     5.3.3.4 Vent 
     In one form, the patient interface  6000  includes a vent  6400  constructed and arranged to allow for the washout of exhaled gases, e.g. carbon dioxide, as shown in  FIG.  30   . 
     In certain forms, the vent  6400  is configured to allow a continuous vent flow from an interior of the plenum chamber  6200  to ambient whilst the pressure within the plenum chamber is positive with respect to ambient. The vent  6400  is configured such that the vent flow rate has a magnitude sufficient to reduce rebreathing of exhaled CO2 by the patient while maintaining the therapeutic pressure in the plenum chamber in use. 
     One form of vent  6400  in accordance with the present technology comprises a plurality of holes, for example, about 20 to about 80 holes, or about 40 to about 60 holes, or about 45 to about 55 holes. 
     A vent  6400  may be located in the plenum chamber  6200 . Alternatively, a vent  9404  is located in a decoupling structure, e.g., a swivel (see e.g.,  FIG.  22   ). 
     The conduit connectors  6800 , which are described in greater detail below, may also include vent features. 
     5.3.3.5 Decoupling Structure(s) 
     In one form, the patient interface  9000  includes at least one decoupling structure, for example, a swivel or a ball and socket. 
     5.3.3.6 Connection Port 
     Connection port  6600  allows for connection to the tube  6348  of air circuit  4170  (see e.g.,  FIG.  7   ). The connection port  9600  according to an example of the present technology may be connected to the connection port housing  9903  (see e.g.,  FIG.  22   ). The connection port  9600  may be swivelable relative to the connection port housing  9903  and the connection to the air circuit  4170  may also be swivelable. 
     The connection port  9600  and the connection port housing  9903  may be positioned superior to the patient&#39;s head in use. 
     5.3.3.7 Forehead Support 
     Examples of the patient interfaces of the present technology shown in  FIGS.  22 - 39    do not include a forehead support. Variations of the patient interface of the present technology may include a forehead support. 
     5.3.3.8 Conduits 
     The patient interface  9000  according to examples of the present technology may include conduits  9900  to provide the flow of pressurized air from the connection port  9600  to the cavity  9001  in the plenum chamber  9200 . The conduits  9900  may be similar to the lateral portions  3302  and superior portions  3304  of  FIG.  6   , and to the tube  6350  of  FIG.  7   . The conduits  9900  may be joined superior to the patient&#39;s head at the connection port housing  9903  and may pass along lateral sides of the patient&#39;s head between corresponding ones of the patient&#39;s eyes and ears. The conduits  9900  may be connected to the cushion assembly  9105  (e.g., plenum chamber  9200 ) via conduit connectors  9800 , as described below, to provide the flow of pressurized air to the cavity  9001 . 
     The conduits  9900  may also stabilize and position the seal-forming structure  9100  on the patient&#39;s face. Thus, the conduits  9900  may function similarly to the ties of the positioning and stabilising structure  9300 . Accordingly, the mechanical connection of the conduits  9900  to the conduit connectors  9800  may be sufficient for tension forces in the conduits  9900  to be transmitted to the seal-forming structure  9100  through the conduit connectors  9800 . 
     The conduits  9900  may include features of similar conduits disclosed in International Application Publication No. WO 2017/124155 A1, which is hereby incorporated by reference herein in its entirety. For example, the conduits  9900  of the present technology may include features of the headgear tubes  3350  depicted in  FIGS.  3 A- 3 L  of this document, as well as the associated written description. 
     The conduits  9900  may also be provided with sleeves  9901  to cushion the patient&#39;s face against the conduits  9900 . The sleeves  9901  may be removable. The sleeves  9901  may be made from a breathable material. 
     The conduits  9900  may also include tie connectors  9902  to facilitate connection with ties of the positioning and stabilising structure  9300 . 
     5.3.3.9 Conduit Connectors 
     As shown in  FIGS.  26 - 33   , the patient interface  6000  may include several views of conduit connectors  6800  of the patient interface  6000 , according to examples of the present technology. The conduit connectors may connect the conduits to the cushion assembly  6105  to provide the flow of pressurized air to the cavity  6001 . These conduit connectors  6800  may be similar to the conduit connectors  9800  (see e.g.,  FIGS.  22 - 25   ), and the following description may equally apply to the conduit connectors  9800 . 
     The conduit connectors  6800  may each be formed with a conduit connector housing  6801 . The conduit connectors  6800  may provide other functions, as described below, such as venting of the plenum chamber  6200 , connection to the positioning and stabilising structure, and asphyxia prevention by inclusion of an anti-asphyxia valve  6850 . 
     In  FIGS.  26 - 33   , the conduit connectors  6800  are shown attached to the plenum chamber  6200  at the plenum chamber holes (see e.g., similar plenum chamber holes  9210 ). As can be seen, there is one conduit connector  6800  on each lateral side of the cushion assembly  6105 , and each conduit connector  6800  is connected to a plenum chamber hole on each corresponding lateral side of the cushion assembly  6105 . The conduit connectors  6800  may each include a conduit connector attachment structure to connect each of the conduit connectors  6800  to a respective plenum chamber hole at the connection rim (not shown). The connection may be mechanical, e.g., snap-fit or friction fit. The connection may also be removable. The material of the conduit connectors  6800  and the material of the plenum chamber  6200  may each be selected to facilitate the desired connection features. For example, the material of the conduit connectors  6800  and the material of the plenum chamber  6200  may each be relatively rigid to permit the audible and/or tactile feedback associated with a snap-fit. The material of the conduit connectors  6800  and the material of the plenum chamber  6200  may be different in at least one aspect or the materials may be the same. The conduit connectors  6800  may also be permanently connected to the plenum chamber at the plenum chamber holes. For example, the conduit connectors  6800  may be ultrasonically welded to the plenum chamber  6200 . The connection between the conduit connectors  6800  and the plenum chamber  6200 , whether removable or permanent, may also be designed to be sufficiently strong such that tension from the conduits can be transferred to the plenum chamber  6200  without disrupting the connection because, as explained above, the conduit connectors  6800  may facilitate positioning and stabilising of the seal-forming structure  6100  on the patient&#39;s head. 
     The conduit connectors  6800  may also be attached to lateral sides of the plenum chamber  6200  to improve aesthetics of the patient interface  6000 . As explained above, the plenum chamber  6200  may be constructed of a transparent or translucent material, which may allow visibility of the patient&#39;s facial features. By locating the conduit connectors  6800  laterally on the plenum chamber, e.g., as shown in the depicted examples, more of the patient&#39;s face is visible, and that arrangement can improve aesthetics of the patient interface  6000 . This contrasts with alternative designs where an elbow and air circuit may be joined to the center of the plenum chamber  6200 , thereby obstructing the view of the patient&#39;s face. 
     The conduit connectors  6800  may also each include a conduit connection end  6802  that connects to a respective conduit (e.g., similar to the conduit  9900  in  FIG.  22   ). The connection between the conduits and the conduit connectors  6800  at the conduit connection ends  6802  may be removable or permanent. A conduit connector inlet hole  6803  may be formed in the conduit connector housing  6801  at the conduit connection end  6802  to receive the flow of pressurized air. The conduit connectors  6800  may include structure, e.g., an undercut, to facilitate a removable, snap-fit connection with corresponding conduits, and each conduit may include a relatively rigid structure at the end that connects to the conduit connectors  6800  to facilitate such a connection. The conduit connectors  6800  may also be joined to the conduits with a friction fit, a snap-fit, or any similar fit. Again, as explained above, the conduits may provide a positioning and stabilising function to locate the seal-forming structure in a therapeutically effective sealing position on the patient&#39;s face, and therefore the connection between the conduits and the conduit connectors  6800  at the conduit connection ends  6802  may be sufficiently secure to permit tension forces from the conduits to be transmitted to the conduit connectors  6800  without disrupting the connection between the conduits and the conduit connectors  6800  at the conduit connection ends  6802 . 
     As shown in  FIG.  29   , the conduit connectors  6800  may also provide a venting function for the patient interface  6000 . The conduit connector housing  6801  may include a vent inlet that is in pneumatic communication with the cavity  6001  when the patient interface  6000  is assembled. The conduit connector housing  6801  may also include at least one conduit connector vent hole  6831 . As can be seen in the depicted examples, each conduit connector housing  6801  includes a plurality of conduit connector vent holes  6831 . This ensures adequate mixing of newly introduced air and air already present in the plenum chamber  6200 , which can enhance carbon dioxide washout and increase the amount of fresh air provided to the patient for respiration. 
     As shown in  FIG.  22 - 24   , the similar conduit connectors  9800  may also provide a connection to ties of the positioning and stabilising structure  9300 . The inferior ties may be joined to the conduit connectors  9800  with clips  9301 . The clips  9301  and the conduit connectors  9800  may include magnets with opposing polarities to facilitate the connection. The connection between the ties of the positioning and stabilising structure  9300  and the conduit connectors  9800  may be releasable. The tension from the inferior ties of the positioning and stabilising structure  9300  may urge inferior portions of the seal-forming structure  9100  into sealing engagement with the patient&#39;s face, e.g., around the mouth. Alternatively, structure to connect to the clips  9301  may be formed directly on a conduit connector housing. 
     5.3.3.10 Anti-Asphyxia Valve 
     In one form, the patient interface  6000  includes an anti-asphyxia valve. As best shown in  FIGS.  30  and  31   , each of the conduit connectors  6800  may include an anti-asphyxia valve assembly  6850 . Accordingly, the patient interface  6000  may include two anti-asphyxia valve assemblies  6850 . Each of the anti-asphyxia valve assemblies  6850  may operate independent of the other, i.e., in response to a cessation of the flow of pressurized air. For example, if the patient is sleeping on his or her side when there is a cessation of the flow of pressurized air and one of the anti-asphyxia valve assemblies  6850  is occluded, e.g., by a pillow, the other of the anti-asphyxia valve assemblies  6850  can function to prevent the patient from being asphyxiated. Although not explicitly shown, the patient interfaces of  FIGS.  22  to  25  and  33 - 1  to  39    may also include at least one anti-asphyxia valve. 
     5.3.3.11 Ports 
     In one form of the present technology, a patient interface  6000  includes one or more ports that allow access to the volume within the plenum chamber  6200 . 
     In one form this allows a clinician to supply supplemental oxygen. In one form, this allows for the direct measurement of a property of gases within the plenum chamber  6200 , such as the pressure. Although not explicitly shown, the patient interfaces of  FIGS.  22  to  25  and  33 - 1  to  39    may also include at least one port. 
     5.3.4 Support Structure and Sealing Portion Arrangements 
     The support structures and sealing portions in the examples described above may have a number of different configurations and arrangements. 
     In use, the sealing portion  3130  (e.g., textile membrane) may be maintained in sealing contact with the patient&#39;s face by 1) a reactive stress of the support structure  3120 ; 2) a pre-formed state of the textile membrane  3130  formed as a non-tensioned, yet substantially constant surface, without leak causing interruptions such as creases, folds, buckles or wrinkles in the textile membrane  3130 ; and/or 3) air pressure within the cavity against an inside surface of the sealing portion  3130 . Each of these factors may contribute to the sealing portion  3130  complying with the anthropometric contours of the patient&#39;s face, thereby minimizing wrinkles or blow-out and maximizing the contact area of the sealing portion  3130 . Tension in the sealing portion  3130  may increase as a result of any of these factors, but the sealing portion  3130  may return to a relaxed state with the removal of the associated factor. 
     In some examples, the sealing portion  3130  may comprise a relatively thin, compliant, stretchable, elastic material, such as a textile membrane comprising a suitable textile material (e.g., nylon, polyester, nylon and polyester mix, microfiber or polyurethane). The sealing portion  3130  may be molded or otherwise attached (e.g., adhered, glued) to the support structure  3120  so that there are no wrinkles in the material of the sealing portion  3130 . This may be advantageous in ensuring that the sealing portion forms a smooth and continuous seal on the patient&#39;s face without any folded sections through which air may leak. Further, the sealing portion  3130  may be shaped or have curvature imparted thereto. The support structure  3120  may also impart curvature to the sealing portion  3130 . In the illustrated examples, the sealing portion  3130  may include curvatures about multiple axes. This may assist the sealing portion  3130  in contouring to the complex facial structure of different patients. 
     For example, as shown in  FIGS.  12 - 21    the sealing portion  3130  may have a concave curved profile from one lateral side (right) to an opposing lateral side (left) (e.g., positive domed curvature in a left-right direction) in order to cradle the patient&#39;s nose while the patient interface  3000  is being worn. In other words, the curvature of the sealing portion  3130  is positive relative to a location where the patient&#39;s columella and/or subnasale contact the sealing portion  3130 . 
     In some forms, as shown for example in  FIGS.  11 - 39   , the patient&#39;s nose is not intended to be received in the cavity  3101  formed by the plenum chamber  3200  and the seal-forming structure  3100 . Instead, unlike conventional masks, the patient&#39;s nose is intended to press against the textile membrane  3130  which in turn accommodates the contours of the patient&#39;s face to comfortably form a reliable seal with the patient&#39;s airways. The textile membrane  3130  may stretch to accommodate the patient&#39;s face. Specifically, the textile membrane  3130  in  FIGS.  11 - 21    and the textile membranes in  FIGS.  31 - 1  to  39    may be held in a relatively relaxed (i.e., untensioned) state prior to contact with the patient. As the patient contacts the textile membrane  3130  (e.g., via their nose), the seal-forming structure  3100  forms to the patient&#39;s face (e.g., their nose) as a result of the compliant, stretchy nature. In other words, contact with the patient&#39;s face applies tension to the textile membrane  3130 , and causes it to form a complimentary shape to the patient&#39;s nose. The slack in the initial form of the seal-forming structure  3100  may allow better contouring to a patient&#39;s face than if the seal-forming structure  3100  was initially under tension, because there are fewer locations resistant to changing shape. Some examples include the bridge portion  3104  that may function to help provide, by eliminating a central opening in the textile membrane  3130 , a sealing portion that presses against the patient&#39;s nose rather than receives the patient&#39;s nose in the cavity  3101 . The bridge portion  3104  may create a location where the patient may apply tension to the textile membrane  3130  so that the seal-forming structure  3100  is snug and/or tight against the patient&#39;s facial features (e.g., in order to limit and/or prevent leaks). This also creates a different sealing experience as compared to conventional masks. This sealing experience may provide enhanced comfort due to contact with a compliant textile membrane  3130  rather than the more rigid materials of conventional masks or conventional sealing arrangements where the sealing portion  3130  has a smaller contact area around a perimeter of the nose and/or mouth. The bridge portion  3104  (or any area selectively tensioned) may create a location where the patient may apply tension to the textile membrane  3130  regardless of whether the bridge portion  3104  is located near at least one hole. 
     The textile membranes  6130  (e.g., the first sealing portion  6131 ) may be held in a relatively tensed state prior to contact with the patient (e.g., the first sealing portion  6131  may be under continuous tension). As the patient contacts the textile membrane  6130  (e.g., via their nose), the seal-forming structure  6100  forms to the patient&#39;s face (e.g., their nose) as a result of the compliant, stretchy nature. In other words, contact with the patient&#39;s face applies additional tension to the textile membrane  6130 , and causes it to form a complimentary shape to the patient&#39;s nose. The entire first sealing portion  6131  may act in a manner similar to the bridge portion  3104  described above, because it may create a location where the patient may apply tension to the textile membrane  6130  so that the seal-forming structure  6100  is snug and/or tight against the patient&#39;s facial features (e.g., in order to limit and/or prevent leaks). While the textile membrane  6130  is taut, the material may be sufficiently complaint or stretchy so that the material can conform to the patient&#39;s facial features with the application of additional tension. The pre-tension in the first sealing portion  6131 , combined with the pressurized seal resulting from the flow of pressurized air, may create a more robust seal in comparison having only pressurized seal resulting from the flow of pressurized air (e.g., as in the patient interfaces  3000 ,  9000 ,  21000 ,  23000 ,  25000 ). 
     Compared to conventional silicone membranes and compression foam seals, the sealing portion  3130  in some of the present examples has a more flexible structural stiffness and therefore has a dynamic spring back characteristic that enables the sealing portion  3130  to recover more quickly when disturbed by an external force. Further, due to the lower structural stiffness a smaller seal force is required allowing the sealing portion  3130  to be more comfortable and create less facial marks during use. 
     The textile membrane  3130  may exhibit variable tension forces across the material (e.g., less tension forces proximal to the naris openings  3102  or in wider stretches of material). The textile membrane  6130  may also be under less tension proximal to the naris openings  6103  since the central portion of the textile membrane  6130  may be unsupported and slightly slacked compared to the perimeter of the textile membrane  6130 . In some forms, the surface of the material of the sealing portion (e.g.,  3130 ) that contacts the patient&#39;s face may have low friction characteristics (e.g., a low friction finish), which may advantageously improve compliance of the material with the patient&#39;s face while also improving patient comfort. 
     The textile membrane  3130  may exhibit variable tension forces across the material (e.g., greater tension forces proximal to the bridge portion  3104 ). The textile membranes  9130 ,  21130 ,  23130 ,  21530  may exhibit similar variable tension forces. In some forms, the surface of the material of the textile membrane  3130  that contacts the patient&#39;s face may have low friction characteristics (e.g., a low friction finish), which may advantageously improve compliance of the material with the patient&#39;s face while also improving patient comfort. 
     In some examples, underlying cushion layer(s) (e.g., portion or second wall  3126 ) may assist in optimizing the sealing portion  3130  contact surface area with the patient&#39;s face. Further, in examples where the sealing portion  3130  is constructed from a breathable material (e.g., a breathable textile), the underlying cushion layer(s) may provide sufficient contact area behind the sealing portion to adequately seal the sealing portion against the patient&#39;s face and prevent leakage. 
     The underlying cushion layer(s) may provide additional flexibility and allow the cushion to be suitable for use by most patient faces (e.g., one size fits most). For example, the sealing portion may be structured as a double air assisted sealing portion (e.g., dual textile membranes), a sealing portion with compression support layer(s) (e.g., open cell foam, polyurethane foam, gel), a sealing portion with TPU, TPE or silicone support layer(s), or a double air assisted sealing portion with additional support layer(s) (e.g., dual textile membranes wherein the inner membrane has a foam laminate layer (e.g., open cell, polyurethane) or a TPU, TPE, polyurethane or silicone molded layer thereon). 
     In use, engagement of the patient&#39;s face  1000  with the sealing portion  10130  will create a temporary strain force that attempts to pull the walls of the support structure  10120  toward one another, as shown in  FIG.  43   . The support structure  10120  will respond to the strain force with an outwardly pulling reaction force. The reaction force transfers more tension to the sealing portion  10130  by preferentially stretching the more compliant sealing portion which creates a resultant spring force in the sealing portion that is exerted on the patient&#39;s face. 
     The sealing portion  10130  may be integrated with the support structure by molding or otherwise attaching the sealing portion  10130  to the inner edge of the support structure  10120 . Thus, for example, an outer perimeter of the sealing portion  10130  may be attached to the inner edge of the support structure  10120  such that the sealing portion  10130  extends radially inwardly of the seal-forming structure beyond or to a further extent than the support structure  10120 . The inner edge of the support structure  10120  may be curved such that the sealing portion  10130  may be slightly angled inwardly toward the mask interior. By attaching the sealing portion  10130  along the inner edge of the support structure  10120 , the sealing portion  10130  does not need to be folded or cut to blend around the corners of the support structure  10120 . This may advantageously reduce the occurrence of protruding folds or wrinkles in the sealing portion  10130 , which may cause leakage, thereby improving the performance of the seal. 
     5.3.4.1 Textile Membrane 
     In accordance with an example of the disclosed technology, the sealing-forming structure  3100  may include a textile membrane  3130  comprising a textile material (see e.g.,  10133 ). The textile material may have an airtight membrane/film or layer coated or otherwise applied thereto to create an air-holding textile composite. The textile composite may be cut (e.g., die cut, ultrasonic, laser, or RF) to a desired shape and then attached to the support structure  3120 . The resulting textile sealing portion  3130  (or textile membrane) may be attached to the support structure  3120  (e.g., silicone, TPE), for example, by overmolding or injection molding. In another example, the textile sealing portion  3130  may be thermo-welded at its edges (outer perimeter) onto the material of the support structure  3120  (e.g., silicone, TPE). In another example, the textile sealing portion  3130  may not be coupled to a support structure  3120 , and the cushion interface  3105  may be constructed substantially from a textile material. 
     In an example, the textile material  10133  is a stretch textile. This may include a knitted material, a woven material, or any other suitable material. A knitted material may be preferable as it provides the textile with elasticity (e.g., stretchiness), particularly in comparison with woven materials. This may be advantageous in providing comfort to the patient, as described below. The elasticity may be in all directions (e.g., four-way stretch/elasticity, e.g., substantially equal elasticity in all directions), and at least in the lateral left-right direction of the textile membrane. The textile material may have a weft knit structure or a warp knit structure, for example. The textile material  10133  may also be any other suitable knit structure. A weft knit structure may be more desirable as the elasticity of weft knit textiles is higher than the elasticity of warp knit textiles. 
       FIG.  45    illustrates the wale  70  of a weft knit fabric, or the direction that the loops of one thread join to a loop of another thread. The course  80 , or the direction of the loops from a single thread is shown in  FIG.  46   .  FIG.  47    illustrates a basic closed loop warp knit  90  in which the wales and courses running parallel to one another.  FIG.  48    illustrates a weft knit  100  in which the wales  70  run perpendicular to the course  80 . 
     5.3.4.1.1 Manufacturing 
     The human face includes a variety of contours, which may be described as either positive or negative curvatures, and either dome or saddle regions. In order to provide increased comfort to a patient, the seal-forming structure  3100  ideally matches or substantially matches the contours. As described above however, the seal-forming structure  3100  should be smooth and continuous on the patient&#39;s face without any folded sections through which air may leak. Thus, a complex geometry of the seal-forming structure  3100  needs to be formed with multiple curvatures to compliment the patient&#39;s face, without creating a surface that is susceptible to leaks. 
     As shown in  FIG.  49   , a textile material (e.g., the textile membrane  3130 ) can be folded about a single axis  11000  (e.g., a horizontal axis as viewed in  FIG.  49   ). In this state, the textile material  3130  has a negative domed curvature (e.g., is substantially convex) as viewed in  FIG.  49   . The textile material  3130  is substantially smooth in this orientation (e.g., the curvature has a constant radius R). In other words, the textile material  3130  is substantially free of wrinkles and/or creases while oriented with a fold about a single axis  11000 . This would remain true regardless of which axis the textile material  3130  was folded about, or in which direction. In other words, the textile material  3130  could be folded about a vertical axis (i.e., instead of a horizontal axis) and/or could have a positive domed curvature (i.e., instead of a negative curvature), and the surface of the textile material  3130  would remain substantially free from wrinkles and/or creases. Additionally, altering the magnitude of curvature would not create wrinkles and/or creases in the textile material. In other words, the singular fold in the textile material can include either a large radius of curvature or a small radius of curvature without creating wrinkles and/or creases in the textile material. Thus, different positive and negative curvatures (e.g., as illustrated in  FIGS.  3 B- 3 C and  3 E- 3 F ) could be applied to a textile material without creating wrinkles and/or creases. 
     In order to compliment the complex surface orientations of a patient (and the differences between individual patients), a seal-forming structure  3100  with multiple folds is more desirable in order to provide more contact with the patient&#39;s face. These curves are ideally about different, non-parallel axes, since the curvatures on a patient&#39;s face are about a variety of axes oriented in multiple directions. However, as shown in  FIG.  50   , providing an additional (e.g., a second, third, fourth, etc.) fold to the textile material may create a wrinkle and/or crease. The creases and/or wrinkles may arise when two or more folds are produced along non-parallel axes  11000 ,  11500 . In other words, multiple folds all along parallel axes may not produce wrinkles and/or creases, but would also not produce a three-dimensional shape optimal for sealing with a patient&#39;s face (e.g., because it would not match the patient&#39;s facial contours). By including curvatures along non-parallel axes, the surface may no longer be maintained as smooth and continuous. Thus, any seal-forming structure  3100  created from a textile with two or more folds would be unlikely to effectively seal against a patient&#39;s face. 
     One way to effectively create curvatures in a material along multiple, non-parallel axes is to apply tension to at least a portion of the textile material  3130 . The application of tension may assist in maintaining the shapes of the various curvatures, while also limiting and/or preventing the formation of creases and/or wrinkles. 
     One way to apply the tension is to stretch the textile material  3130 , and impart multiple curvatures (e.g., along multiple, non-parallel axes) on the textile material while it is under tension. Then, the textile material  3130  can undergo a process (e.g., thermoforming), so that the textile material  3130  can be permanently held in its distorted state (i.e., with its multiple curvatures). As shown in  FIG.  51   , the textile material  3130  includes multiple curvatures, and its surface remains relatively smooth. Thus, this textile material  3130  could be incorporated into a patient interface  3000  as a seal-forming structure  3100 , and provide a seal with a patient&#39;s face, without substantially any leaks of pressurized air from the plenum chamber  3200  to the ambient. In this example, substantially the entire textile material  3130  is under tension. 
     However, once the textile material  3130  is stretched and thermoformed (or a similar process is applied), the textile material  3130  substantially loses its free-state properties. For example, the elasticity that the textile material  3130  may naturally have, would be substantially lost after the thermoforming was completed. A once stretchy textile material  3130  would become relatively stiff while including multiple curvature. A textile material&#39;s  3130  free-state (i.e., before being thermoformed) properties (e.g., drape, flexibility, elasticity, etc.) are also important in determining the sealing capabilities of the eventual textile seal-forming structure  3100 . Thus, if the textile material  3130  is no longer in its free-state, the quality of the seal produced by the textile material  3130  may also be reduced for some patients. In other words, while the curved textile material  3130  formed using thermoforming may be more comfortable in conforming to a patient&#39;s face (e.g., as compared to a textile membrane  3130  formed with only a single bend), the loss of its free state properties may disrupt the ability for the patient interface  3000  to effectively seal with some patient&#39;s faces. Even though there may be no wrinkles and/or creases, a seal-forming structure  3100  formed in this way may still allow leaks (e.g., because the textile membrane  3130  is too stiff to conform to some patient&#39;s faces). Other patients may experience a seal sufficient to prevent leaks. 
     This is not the case in the textile material  6130  of  FIGS.  26 - 33    because the material may still include its free-state properties. Since the first sealing portion  6131  is intended to be substantially flat prior to use, the material does not need to be thermoformed in order to keep its shape. The material may still stretch and conform to a patient&#39;s face. Thus, the textile material  6130  may be able to limit leaks, unlike the example described above. The patient interface  6000  may also be easier to manufacture since the textile material  6130  may not include complex curvatures. 
       FIGS.  52 - 61    show another way to apply tension to only a portion of the textile membrane  3130 . For example, less than half of the textile membrane  3130  may be under tension, while the remained of the textile membrane  3130  may be loose or slack. Thus, the tension is selectively applied to discrete locations of the textile membrane  3130 . Different locations (e.g., a central portion, side portions, etc.) of the textile membrane  3130  may be tensioned in order to assist in imparting differently shaped curvatures. Additionally, more than one location may be under tension in a single textile membrane  3130 . Tension may be selectively applied to the textile membrane  3130  using any number of techniques, some of which are described below. 
     One example technique of selectively applying tension to only a portion of the textile membrane  3130  may be accomplished by applying a crimp to a portion of the textile membrane  3130 . The crimp may apply localized tension without causing the entire textile membrane  3130  to be under tension. The crimp may be applied to any portion or portions of the textile membrane  3130 . In some examples, the majority of the textile membrane  3130  is not imparted with a crimp. In other words, the area of the textile membrane  3130  that is crimped is less than the area of the textile membrane  3130  that is not crimped. In some examples, sections of the textile material  3130  may be removed on at least one side of the crimped portion. In some examples, holes or other discontinuities are not needed in order to form the crimped portion. 
     In some examples, the crimp may be applied to a central portion of the textile membrane  3130 . Applying the crimp may be accomplished by removing sections of the textile material  3130  (e.g., in order to form holes  3102 ) while the textile is in its free state (i.e., has not be thermoformed). The textile material  3130  can then be manipulated around the created holes  3102  in order to limit the formation of any wrinkles and/or creases. These holes  3102  may be used later as the naris openings, through which pressurized air may be delivered to the patient&#39;s nares. 
     As shown in  FIG.  52   , a textile material  3130  for use in a nasal only patient interface  3000  is shown. Two holes  3102  cut into the textile material (e.g., by hand, with a laser, etc.), with each hole  3102  corresponding to a single naris of a patient. However, any number of holes  3102  may be cut depending on the final use of the textile material (e.g., a single opening for both nares, an additional opening for the mouth, etc.). These holes  3102  may be cut into the textile material  3130  either before the first fold is made or after the first fold is made. The order of forming a single (i.e., first) fold and cutting will not substantially effect the presence of creases and/or wrinkles. 
     With specific reference to the textile material for use in a nasal only mask as shown in  FIG.  52   , each of the holes  3102  is elongated, and formed as a generally rectangular shape, although other shapes (e.g., circular, triangular, etc.) may be used in other examples. The holes  3102  may be separated by a strip of material that may be formed as a bridge portion  3104 . Although the bridge portion  3104  may also be formed independently of the holes  3102 . If more than two holes  3102  are cut into the textile material  3130 , there may be multiple bridge portions  3104 . Creating more bridge portions  3104  may be useful when additional holes are needed, and/or if the textile material  3130  is larger (e.g., so that it does not buckle despite a single bridge portion  3104 ). As described above, the patient&#39;s nose (e.g., their pronasale) may contact the bridge portion  3104 , and the bridge portion  3104  may limit the patient&#39;s nose from extending into the plenum chamber  3200 . 
     As shown in  FIG.  53   , once the initial fold is made about a first axis  11000  (e.g., a horizontal axis as shown in  FIG.  53   ) and the holes  3102  have been cut, the bridge portion  3104  may be folded (e.g., a second fold) about a second axis  12000  that is parallel to (or collinear with) the first axis  11000 . In the illustrated example, the bridge portion  3104  is flipped into a downward direction (as viewed in  FIG.  53   ) in order to clear a space between the pair of holes  3102 . In other words, a positive domed curvature (e.g., as viewed in  FIG.  53   ) is imparted on the bridge portion  3104 , while the first fold was a negative domed curvature. 
     In some forms, once the bridge portion  3104  is folded, a space  3180  is created between the holes  3102 . Specifically, the holes  3102  may be vertically oriented (e.g., as viewed in  FIG.  53   ) and the space  3180  is oriented along the first axis  11000 . In other words, each of the holes  3102  are substantially perpendicular to the first axis  11000 , and the space  3180  exists between openings to each of the holes  3102 . A width of the space  3180  substantially corresponds to a width between the nasal alas or alar ridges of the patient. In other word, the width of the space  3180  is large enough to receive a patient&#39;s nose, and have the patient&#39;s nares approximately aligned with the holes. Apexes of the textile material  3130  (i.e., created by the first fold) would contact the patient proximate to the nasolabial sulcus when the nose is positioned within the space. 
     As shown in  FIG.  54   , once the bridge portion  3104  has been folded about the second axis  12000 , the material may be crimped in order to maintain its “flipped” orientation. Crimping may be one way to selectively apply tension to a portion of the textile membrane  3130 , without applying tension to the entire textile membrane  3130 . Other techniques of selectively applying tension may similarly be incorporated either with or instead of crimping. The bridge portion  3104  is maintained so as to no longer have the first curvature  10000  about the first axis  11000 . For example, the bridge portion  3104  may not have an explicitly positive domed curvature (e.g., the bridge portion  3104  may have a smaller magnitude of curvature in  FIG.  54    than in  FIG.  53   , the bridge portion  3104  may have a zero curvature, etc.), but would not have a negative dome curvature along with the remainder of the textile material  3130  (e.g., while the cushion assembly  3105  is in use). In other words, after the crimping occurs, the curvature in the bridge portion  3104  is different (e.g., in magnitude and/or direction) than the rest of the textile material  3130 . 
     In some examples, the bridge portion  3104  is crimped so that the material forming the bridge portion alone is taut (i.e., crimping may not apply tension to the rest of the textile membrane  3130 ). Specifically, a length of the bridge portion  3104  is folded against itself in order to reduce a total exposed length. The tension in the textile that comprises the crimped bridge portion  3104  is greater than the tension in the surrounding textile, which has not been crimped. Thus, a surface of the bridge portion  3104  may be substantially flat and/or may have minimal curvature (e.g., while the curvature about the first axis  11000  remains through the rest of the textile material  3130 ). The fold in the bridge portion  3104  may be substantially in the center, so that a length of material on either side of the fold line is substantially equal, although one side may be longer than the other. Although the crimp creates tension, the bridge portion  3104  may still be able to flex relative to the holes  3102  (e.g., as a result of the free-state properties of the textile). The crimped bridge portion  3104  may be similar to the un-crimped bridge portion  6106  since both are under tension, but also retain their free-state material properties. 
     In other examples, other ways of applying tension may be used to create a taut bridge portion  3104 , and/or tension may be applied to other locations of the textile membrane  3130 . 
     In some examples, the resulting length of the bridge portion  3104  after being crimped affects the size of the holes  3102 . For example, if the usable length remains large (i.e., the crimped length is small), the holes  3102  remain large. Said another way, there is a direct relationship between the length of the bridge portion  3104  that is crimped and the size of the holes  3102 . When the length of the bridge portion  3104  decreases (i.e., because the crimped length increases), the tension in the crimped bridge portion reduces the size (e.g., the circumference) of each hole  3102 . The length of the bridge portion  3104  may be adjusted based on a size of the patient&#39;s nose (e.g., the bridge portion  3104  may be crimped with small, medium, and large sizes in order to accommodate different sized nares). 
     In some examples, the bridge portion  3104  is maintained in its crimped state as a result of ultrasonic welding and/or applying an adhesive (e.g., glue), although any suitable method may be used. Any of these methods may be applied to the non-usable length  3184  of the bridge portion  3104 . For example, an adhesive may be applied to a selected portion of the textile layer of textile membrane  3130 , and the selected portions are folded against one another. In other words, the useable length of the bridge portion  3104  may be substantially free from any substance that was applied. The crimped region of the bridge portion  3104  may still have the positive domed curvature described above, even after one of the securing methods has been applied. 
     In one example, a portion of the non-usable portion  3184  of the bridge portion  3104  may be trimmed or cut after the securing method is applied. Once the textile membrane  3130  is completely assembled as a seal-forming structure  3100 , the non-usable portion  3184  would be positioned within the plenum chamber  3200 , and may cause a disruption to airflow (e.g., and create noise). Thus, trimming the non-usable portion  3184  may reduce or eliminate any disturbances. 
     As shown in  FIGS.  55 - 57   , once the crimping is complete, additional curvatures about different axes may be applied to the textile material  3130 . Crimping the bridge portion  3104  may reduce the total area  3188  that is affected by additional curvatures. Said another way, the affected area  3188  (i.e., shown in hatching) with the bridge portion  3104  crimped in  FIG.  55    is less than the affected area  3190  in  FIG.  51    where crimping has not occurred. The affected area  3188 ,  3190  relates to the area where creases and/or wrinkles are likely to appear as a result of introducing multiple curvatures to the textile material  3130 . When the bridge portion  3104  is crimped, the affected area  3188  is substantially close to the holes  3102 . For example, the affected area  3188  may form a substantially rectangular shape, with edges substantially tangent to the holes  3102 . The close proximity of the affected area  3188  to the holes  3102  substantially prevents creases and/or wrinkles from forming when additional curvatures are applied to the textile material  3130 . 
     In some examples, a third curvature  30000  is formed in the textile material  3130  about a third axis  13000 . The third axis may extend along a direction substantially perpendicular to the first and second axes  11000 ,  12000  (although it could also be oblique or skew). In other words, the third axis  13000  may be a substantially horizontal axis (e.g., as viewed in  FIGS.  55 - 57   ). In the illustrated example, the third axis  13000  is centered on the textile material  3130 , and extends along the bridge portion  3104 . The third curvature  30000  may have a substantially saddle region (e.g., as viewed in  FIGS.  55 - 57   ). In other words, the third curvature  30000  may be positively curved and may cradle the patient&#39;s nose after the patient dons the patient interface  3000 . This means that the textile layer  10133  specifically is a saddle region about the third axis  13000  when the patient interface  3000  is worn. Thus, the second and third curvatures  20000 ,  30000  may curve in the same direction (e.g., both positive curvatures), although about substantially perpendicular axes and may define different regions (e.g., the second curvature  20000  is a dome and the third curvature  30000  is a saddle). While the third curvature  30000  is applied, the first and second curvatures  10000 ,  20000  remain in their previously curved position. In other words, the application of the third curvature  30000  (or additional curvatures) may not substantially affect the magnitude and/or direction of the previous curvatures. 
     In some examples, a fourth curvature  40000  may be formed in the textile material  3130  about a fourth axis  14000 , which may extend along a direction substantially perpendicular to the first, second, and third axes  11000 ,  12000 ,  13000  (although the fourth axis  14000  may have any relationship to the other axes). In other words, the fourth axis  14000  may be a substantially vertical axis (e.g., as viewed in  FIG.  55   ). In the illustrated example, the fourth axis  14000  does not intersect the bridge portion  3104 . The fourth curvature  40000  may extend toward a center of the textile material  3130 , and may be a saddle region as viewed in  FIG.  55   . In other words, the fourth curvature  40000  may cradle the patient&#39;s face (e.g., their lip superior) after the patient dons the patient interface  3000 . 
     In some examples, the fifth curvature  50000  may be formed in the textile material  3130  about a fifth axis  15000 , which extends along a direction substantially parallel to, and offset from, the first and second axes  11000 ,  12000  (although the fifth axis  15000  may have any orientation). In other words, the fifth axis  15000  is a substantially horizontal axis (e.g., as viewed in  FIG.  56   ). In the illustrated example, the fifth axis  15000  does not intersect the bridge portion  3104 . The fifth curvature  50000  includes a similar orientation as the first curvature  10000 , and may be a negative dome curvature (e.g., as viewed in  FIG.  56   ). The first and fifth curvatures  10000 ,  50000  may have different magnitudes of curvature (e.g., the magnitude of the first curvature  10000  may be more negative than that of the fifth curvature  50000 ). The fifth curvature  50000  may have a variable curvature, in that its radius of curvature may not be constant along the length of the axis  15000 . For example, since the fifth curvature  50000  and the first curvature  10000  are along substantially parallel axes, changing the radius of curvature of the fifth curvature  50000  may bring the two curvatures  10000 ,  50000  together (e.g., blend them into one curvature). The fifth curvature  50000  may have a smaller radius of curvature proximate its center (e.g., proximate to an intersection with the third axis  13000 ), and has a larger radius of curvature proximate an edge of the textile material  3130 . Here, the larger radius of curvature of the fifth curvature  50000  may blend into the first curvature  10000  (e.g., proximate to an edge of the textile material  3130 ). In other words, fifth curvature  50000  may extend into the first curvature  10000  as the radius of curvature in the fifth curvature  50000  increases. Blending the curvatures may assist in providing a smooth surface, and limiting the potential of forming creases and/or wrinkles in the bent textile material  3130 . 
     In some examples, the fourth and fifth curvatures  40000 ,  50000  are both included on the textile material  3130 . In other words, the medial subnasale region  3260  of the eventual seal-forming structure  3100  constructed from the textile material  3130  may include both the fourth curvature  40000  and the fifth curvature  50000 . These curvatures  40000 ,  50000  may work together to seal against the compound curvature (e.g., multiple curvatures in multiple directions) on a patient&#39;s lip superior. In the illustrated example, the fourth curvature  40000  is the dominate curvature of the medial subnasale region  3260  when both the fourth and fifth curvatures  40000 ,  50000  are included on the textile material  3130 . For example, the human head has a natural curvature toward either lateral side. In other words, the lip superior curves to the left and right sides of the patient&#39;s face, from the philtrum and toward the cheilion. The lip superior may also include a curvature about a substantially horizontal axis, which runs perpendicular to the sagittal plane. However, this curvature is over a smaller distance (i.e., the distance between the subnasale and the upper vermillion is less than the mouth width), and may have more variance among different patients (e.g., some may have a larger, more defined curve than others). 
     The fourth curvature  40000  would be the larger curvature, as compared to the fifth curvature  50000 . This may include the textile material  3130  extending around the fourth axis  14000 , and a lower edge of the textile material  3130  being folded about the fifth axis  15000 , so that the fourth curvature  40000  includes more total area on the textile material  3130 . However, the crimped bridge portion  3104  allows both curvatures  40000 ,  50000  to be maintained in an overlapping region without forming creases and/or wrinkles. Thus, in some examples, the fifth curvature  50000  may not be entirely along the fifth axis  15000 , and may instead extend along a curved path as it follows the length of the fourth curvature  40000 . 
     Some patients may have a substantially vertical lip superior between the subnasale and the upper vermillion, and thus there may be substantially no curvature along the substantially horizontal axis perpendicular to the sagittal plane. In these patients, the fifth curvature  50000  may not include a curved lip region to seal against. However, the material of the fifth curvature  50000  may deform into the substantially vertical (e.g., flat) region, and is still capable of maintaining an effective seal against the patient&#39;s face. Additionally, the height between the subnasale and the upper vermillion may be different on different patients. For example, this distance may be very small. In this example, the textile material of the fifth curvature  50000  may be able to deform into the tight region and work as a lead in, in order to effectively seal against any height. In other examples, the textile material may be customizable for individual patients, and the curvatures, as well as radii of curvature, are selected based on a particular patient&#39;s facial geometry (e.g., which may be identified using scanning). 
     Any number of these curvatures may be applied to a single seal-forming structure  3100  in order to assist in enhancing the fit of the patient interface  3000  against the patient&#39;s face. For example, all five of these curvatures may be applied to a single seal-forming structure  3100 . In other examples, only some of the curvatures may be applied to the seal-forming structure  3100 . In other examples, more than five curvatures may be applied to the seal-forming structure  3100 . The magnitude and/or directions of the curvatures may be variable across individual cushion assemblies  3105  (e.g., the textile membrane  3130  may be custom made for an individual patient). 
     In some examples, the shape of the textile membrane  3130  may be formed, and the textile membrane  3130  may be connected to the lateral support region  3122 . In the illustrated example, the textile membrane  3130  and the lateral support region  3122  are connected using injection molding so that they are formed integrally with one another. In other examples, the textile membrane  3130  and the lateral support region  3122  may be coupled together in a different way (e.g., by overmolding). In still other examples, the textile membrane  3130  may not be coupled to a lateral support region  3122 . 
     In some examples, the three-dimensional shape (i.e., resulting from the multiple curvatures) of the textile membrane  3130  may assist an injection molding tool in forming the flexible support structure  3120  and/or the plenum chamber  3200 . For example, the bridge portion  3104  folded about the second axis  12000  (e.g., and crimped) may be useful when loading the textile membrane  3130  into the injection molding tool. Specifically, the crimped bridge portion  3104  may be used as a spigot when placing the textile membrane  3130  in the injection molding tool. In other examples, the textile material  3130  may be curved in order to completely form the plenum chamber  3200 , such that an injection molded material is not needed in the patient interface  3000 . In other words, the plenum chamber  3200  and seal-forming structure  3100  may be constructed from the textile material  3130 , and not from silicone, or other flexible, molded material. 
     As shown in  FIGS.  58  and  59   , a material (e.g., silicone) may be molded onto the textile membrane  3130 . The material may be applied to the inner layer  3194  of the textile membrane  3130  (e.g., the layer coated with an air impermeable material  10131 ), so as to avoid covering a portion of the textile on the posterior surface (and potentially contact the patient&#39;s face, in use). Although, in other examples, the material may be applied to the outer layer  3196  of the textile membrane  3130 . The material may extend beyond an end of the textile membrane  3130  and toward the plenum chamber  3200  (e.g., the material may be molded so that some of the lateral support region  3122  does not contact the textile membrane  3130 ). As the material is molded to the textile membrane  3130 , the resulting support structure  3120  may have substantially the same curvature (i.e., magnitude and direction) as the adjacent textile membrane  3130  (e.g., in order to create a substantially smooth, and uninterrupted surface). The thickness of the material (i.e., the lateral support region) may change along its length. For example, the lateral support region  3122  may be thicker distal to the textile membrane  3130 . Additionally, a total thickness of the overlapping textile membrane and material may also be thinner than the adjacent region containing only the molded material (i.e., the lateral support region  3122 ). 
     As shown in  FIG.  58   , some examples of the patient interface  3000  may include a single wall lateral support region coupled to the textile membrane  3130 . A single wall of silicone material may be molded to the textile membrane  3130 , in order to form the support structure  3120  that connects the seal-forming structure  3100  to the plenum chamber  3200 . An outer surface  3195  of the support structure  3120  substantially matches the outer surface  3196  of the textile membrane  3130  (i.e., the textile layer), in order to form a smooth, continuous surface. The inner surface  3197  may have a different thickness as described above. The silicone material overlaps a portion of the textile membrane  3130  in order to form a sturdy connection, but not add unnecessary weight to the patient interface  3000 . The silicone material may taper to its smallest thickness at an end of the overlap region  3199  (e.g., proximate to end  3124 ). The end of the overlap region  3199  is spaced apart from the naris opening  3102  in order to avoid potential interference (e.g., that creates noise) of pressurized air into the patient&#39;s nares. The overlap region  4000  substantially on the first curvature  10000 , and may provide additional support for maintaining the appropriate magnitude for the first curvature  10000 . 
     As shown in  FIG.  59   , some examples of the patient interface may include a dual walled support structure  3120  coupled to the textile membrane  3130 . A single wall of silicone material may be molded to the textile membrane  3130 , in order to connect the seal-forming structure  3100  to the plenum chamber  3200 . As described above, the outer surface  3195  substantially matches the outer surface  3196  of the textile membrane  3130 , and the inner surface  3197  includes varying thicknesses along its length. However, the overlap region  3199  may extend a different length along the inner surface  3194  of the textile membrane  3130 . Specifically, the overlap region  3199  may contact a length of the textile membrane  3130  that is less than in the single wall support structure  3120 , described above. Instead, a portion of the silicone wall  3126  may continue to extend along a length of the textile membrane  3130 , but spaced apart from the inner surface  3194 . This second wall  3126  of the support structure  3120  may extend in a cantilevered manner from the remainder of the lateral support region (i.e., from end  3124 ). The support structure  3120 , with the inclusion of the second wall  3126 , may extend along a similar total overlapped length as the support structure  3120  in the single wall example. The second wall  3126  may particular be disposed proximate to an apex of the first curvature  10000 , in order to provide additional support. The second wall  3126  is stiffer than the textile membrane  3130 , and may assist in maintaining the shape of first curvature  10000  when the textile membrane  3130  contacts the patient&#39;s face. If additional force is applied, the textile membrane  3130  and the second wall  3126  may deform together. 
     After assembling the textile membrane  3130  to the support structure  3120 , the resulting cushion assembly  3105  may be used in a patient interface  3000 . Specifically, the patient&#39;s face (e.g., the patient&#39;s nose) may be positioned within the space  3180  so that the naris openings  3102  are positioned proximate to the respective nares. 
     When positioning the cushion assembly  3105 , the patient may align the bridge portion  3104  with their nose. Specifically, the bridge portion  3104  may be directed in the anterior/posterior direction as the cushion assembly  3105  is donned (e.g., the textile membrane  3130  may be substantially facing the superior direction). The patient moves the bridge portion  3104  into contact with their nose, where the taut material of the bridge portion  3104  presses against the patient&#39;s nose (e.g., in the subnasale region and may contact the columella). The bridge portion  3104  limits the patient&#39;s nose from moving into the cavity  3101 , but as the patient&#39;s nose presses against the taut material, tension may be applied to the surrounding regions on the textile membrane  3130 . In other examples, the patient may move their face toward a separate area of the textile membrane  3130  that is under tension (e.g., if the entire area of the textile membrane is under tension like in  FIGS.  26 - 33   ). 
     While the patient contacts the bridge portion  3104 , the patient may also contact the lateral side  3250  and/or corner regions  3252  of the textile membrane. The lateral side  3250  and the corner region are disposed on a region of the third curvature  30000  proximate to an apex of the first curvature  10000 . In other words, the lateral side  3250  and corner region  3252  are disposed on a surface having a saddle region, and face toward a center of the cushion assembly  3105 . A positive curvature may be between the opposing lateral sides  3250 . The lateral side  3250  and corner regions  3252  are also positioned proximate to where the textile membrane transitions to a negative dome curvature (i.e., formed by the first curvature  10000 ), and may be understood to be at a posterior portion of the cushion assembly  3105 . This transition region may be understood to be a domed region of the sealing portion  3130 . The lateral side  3250  and/or the corner regions  3252  contact the outer surface of the patient&#39;s nose (e.g., proximate to the patient&#39;s nasal ala), and may terminate proximate to the alar crest points on either side of the patient&#39;s nose. In this orientation, the naris openings  3102  are aligned with the patient&#39;s nares, and may effectively deliver pressurized air to the patient&#39;s airways. The lateral side  3250  and/or corner regions  3252  are generally loose, which allows these regions of the textile membrane  3130  to better form to the various contours of the patient&#39;s face. For example, the lateral side  3250  and/or corner regions  3252  may be able to adjust in shape in order to better conform to the region surrounding the patient&#39;s nares in order to develop a tight seal. As the patient&#39;s nose engages the bridge portion  3104 , the lateral side  3250  and/or corner regions  3252  may experience tension, in order to maintain the appropriate shape from the patient. 
     As shown in  FIG.  60   , the textile membrane  3130  may include an arch  60000  adjacent each of the naris openings  3102 . The arches  60000  are also disposed proximate to the lateral side  3250  and/or corner regions  3252 . The arches  60000  have a saddle region in the same direction as the first curvature  10000  (and may also be about the first axis  11000 ). The arches  60000  extend into the space  3180  so that a distance between the arches  60000  may be the narrowest distance between opposing lateral sides  3250  and/or corner regions  3252 . 
     When the patient dons the cushion assembly  3105 , the naris openings  3102  may have a generally vertical alignment (as described above), and an inner surface of each nostril contacts the respective arch  60000 . In other words, the each arch  60000  is configured to contact an inner surface of the each respective nasal ala. Since the patient&#39;s nose is also contacting the bridge portion  3104  of the textile membrane  3130 , each naris opening  3102  fully surrounds each respective naris. 
     As shown in  FIG.  61   , once each of the arches  60000  contacts the inner surface of the respective naris, the arch  60000  flips to a concave orientation (i.e., a positive dome curvature relative to the inner surface of the respective naris). This is similar to what occurred with the bridge portion  3104 , although a curvature of the arches  60000  may be directed in a different direction. For example, each arch  60000  may move along the first axis  11000  toward the respective plenum chamber connector  3204 . In this orientation, each naris opening may have a substantially tear-drop shape. 
     When the arch  60000  flips (i.e., from a negative dome curvature to a positive dome curvature), the arch  60000  may wrap around an alar rim of the respective naris. In other words, each arch  60000  wraps around the outer periphery of the respective naris. The compliant nature of the textile membrane  3130  allows the arches  60000  to adjust to the shape of the patient&#39;s alar rim in order to form a seal sufficient to maintain the therapeutic pressure within the plenum chamber  3200 . 
     Once the cushion assembly  3105  is properly positioned, the patient may supply pressurized air. The compliant nature of the textile membrane  3130 , and the fact that the outer portions are initial loose (e.g., as opposed to taut like the bridge portion), allows the seal-forming structure  3100  to form a dynamic seal as pressurized air fills the cavity  3101 . The dynamic seal allows the cushion assembly to shift slightly on the patient&#39;s nose, while still maintaining a pressurized cavity  3101 , and delivering pressurized air to the patient&#39;s airways. For example, the arches  60000  may be able to slightly move against the alar rims without losing their seal. 
     Additionally, the third, fourth, and/or fifth curvatures  30000 ,  40000 ,  50000  may provide additional assistance in maintaining the position of the seal-forming structure  3100 , and enhancing comfort for the patient. For example, the third curvature  30000  may have a saddle region relative to the patient, and may contact the subnasale region of the patient along the columella (e.g., via a positive curvature). The third curvature  30000  may not extend to the patient&#39;s pronasale, leaving it exposed. The third curvature  30000  may be disposed in the pronasale region  3270  of the textile membrane  3130 . The fourth curvature  40000  may have a saddle region relative to the patient, and may contact the patient&#39;s lip superior (e.g., via a positive curvature). Thus, the fourth curvature  40000  extends in the lateral (left/right) direction while worn by the patient, and may also extend substantially along the mouth width. The fifth curvature  50000  may have a negative dome curvature relative to the patient&#39;s lip superior. In other words, the fifth curvature  50000  curves away from, and does not cradle, the patient&#39;s lip superior. The fourth and fifth curvatures  40000 ,  50000  may contact substantially the same region of the patient&#39;s face, and one or both may be included on a given textile membrane  3130 . The fourth and/or fifth curvatures  40000 ,  50000  may be disposed in the medial subnasale region  3260  of the textile membrane  3130 . The fifth curvature  50000  may create a “pillow” and/or “airbag” effect on the patient. In other words, the negative dome curvature of the fifth curvature, relative to the patient&#39;s lip superior in use, may provide additional cushioning and/or comfort to the patient as a result of the pressurized air inflating the textile membrane  3130 . 
     While the above description was specifically directed toward a nasal cradle, it is equally applicable to the patient interfaces  9000 ,  21000 ,  23000 ,  25000  described above. Additional description specific to the full face cushion is described below. 
     5.3.4.1.1.1 Full Face Cushion 
     In addition to the steps described above, manufacturing and assembling the full face cushion differs from the nasal cushion because of the additional area that the full face cushion is required to seal around (i.e., both the patient&#39;s nares and mouth). Accordingly, additional surface area of textile membrane  10135  is required, and additional surface area of the support structure  6120  (e.g., silicone material) is required, since the overall size of the full face cushion is larger than the nasal cushion. 
     The patient interfaces, illustrated in  FIGS.  22  to  39   , are assembled by placing two pieces of textile membrane  10135  into a molding tool, and molding a flexible material (e.g., silicone) onto the textile membranes  10135  in order to form the patient interface  6000 ,  9000 ,  21000 ,  23000 ,  25000 . In these examples, the two textile membranes  10135  are different shapes, in order to seal with a specific region on the patient&#39;s face (although a single textile membrane  10135  could be used). As described above, the first textile membrane  10135  (i.e., used to form the first sealing portion  6131 ) has a rounded shape, and the second textile membrane  10135  includes a U-shape or a C-shape (see e.g.,  FIG.  33   ), or a ring or annular shape (see e.g.,  FIG.  33 - 1   ). The textile membranes  10135  are substantially flat (e.g., having a two-dimensional shape) prior to being placed into the mold. Once they are positioned in the mold, the two textile membranes  10135  are spaced slightly apart from one another (e.g., via a gap  21190 ). In some examples, the mold maintains the textile membrane  10135  in a partially flat position as the flexible material (e.g., silicone) is introduced into the mold (e.g., the patient interface  6000 ). In some examples, the mold introduces curvatures to the textile membranes  10135  and holds the textile membranes  10135  in their curved shape as flexible material (e.g., silicone) is introduced into the mold (e.g., the patient interface  9000 ,  21000 ,  23000 ,  25000 ). The curvatures introduced to the textile membranes  10135  by the mold may cause the bridge portion (e.g.,  9106 ) to fold on itself. As the flexible material is introduced into the mold and hardens, it secures the two flexible textile membranes  10135  together. After the molding process is complete, the bridge portion  9106  can be crimped in order to remove slack from the textile membrane  10135 . Alternatively, the bridge portion  9106  can be crimped prior to positioning the textile membranes  10135  in the mold. This may impart a pre-deformation onto the textile membranes  10135  (e.g., the textile membranes  10135  deform prior to being positioned within the mold and having additional curvatures imparted on the remainder of the textile membranes  10135 ). The bridge portion  6106  may not need to be crimped since the textile membrane  10135  was held in taut position by the mold, and may be generally flat along the lateral direction. The bridge portion  6106  may be under tension without a crimp, and may apply substantially the same benefits as the bridge portions with a crimp. As noted previously, it may be easier to manufacture the textile membrane  10135  into the first sealing structure  6131  as opposed to the first sealing structure on another patient interface (e.g.,  9000 ) since the first sealing structure  6131  may not include complex curvatures. 
     By using two separate pieces of textile membrane  10135  to form the patient interface (e.g.,  9000 ,  21000 , etc.), overlap of the textile material  10135  can be avoided. Particularly, overlap may be an issue when attempting to impart complex curvatures onto a large piece of textile membrane  10135 , because longer curvatures may be possible, which may lead to more opportunities for the textile membrane  10135  to fold on itself. Since the patient interface  6000  does not include complex curvatures, overlap of the textile material  10135  may be less likely. However, using two separate pieces of textile material  10135  may allow the patient interface  6000  to include a substantially planar surface of the first sealing structure  6131  oriented in a first direction, and a substantially planar surface of the second sealing structure  6132  in a second direction. In other words, the separate pieces of textile membranes  10135  may be disposed in different orientations in order to better conform to a patient&#39;s face as a result of the patient interface  6000  being constructed from separate textile membranes  10135 . 
     One way to solve the issue of overlap was to stack multiple pieces of the textile membrane  10135  on top of one another to produce complex curvatures (e.g., by creating an overlap of a few millimeters with two or more textile membranes  10135 ), while reducing the stress experienced in each textile membrane  10135  (e.g., as compared to a single textile membrane  10135 ). However, leaks could occur in the overlapped region, which could degrade the quality of the seal in the eventual patient interface  9000 ,  21000 , etc. 
     If two separate pieces of the textile membrane  10135  are used but not overlapped, the likelihood that a single piece of textile membrane  10135  will fold on itself is reduced because the length of each individual curve is reduced. Additionally, the likelihood of leaks occurring may be reduced from an example where the textile membranes  10135  overlap, since the overlapping interface of textile membranes  10135  has been removed. 
     Two spaced apart pieces of textile membrane  10135  are used, and the flexible material may be molded in the space between the two textile membranes  10135 . As illustrated, this space may be relatively small (e.g., in order to reduce contact between the patient&#39;s skin and the support structure  9120 ,  21120 , etc.). As a result, this may make molding this section of the patient interface (e.g.,  9000 ,  21000 , etc.) difficult (e.g., because the textile membranes  10135  have to be accurately positioned, the flexible material has to fill the space without covering the textile layer  10133 , etc.), but may increase the likelihood that the resulting patient interface (e.g.,  9000 ,  21000 , etc.) will not include creases formed as a result of the complex curvatures imparted on the textile membrane  10135 . A similar principle may be true for the patient interface  6000 , even though there are no complex curvatures in the first sealing portion  6131 . 
     In this example, there is a direct trade-off between ease of manufacturing, and full textile contact. For example, the patient interface  9000  shown in  FIG.  35    (or the patient interface  6000  in  FIG.  33   ) may be easier to manufacture than the patient interface  21000  shown in  FIG.  33 - 1    (e.g., because the liquid material may not be molded into as small of spaces). However, the patient&#39;s lip superior (e.g., proximate to the philtrum) will contact a larger surface area of the support structure  9120  (i.e., not the textile layer  10133 ) in the example shown in  FIG.  35   , potentially having a lower comfort level for the patient than the patient interface  21000  of  FIG.  33 - 1   . 
     The example of the patient interface  23000  shown in  FIG.  33 - 2    may attempt to balance the issues observed in the patient interface  9000  of  FIG.  34    (or  6000  of  FIG.  33   ) and the patient interface  21000  of  33 - 1 . In other words, the patient interface  23000  of  FIG.  33 - 2    may attempt to reduce the manufacturing complexity, without sacrificing patient comfort. To do this, the second textile membrane  10133  may include a U-shape or C-shape (e.g., similar to the example shown in  FIGS.  33  and  35   ). The U-shaped textile membrane  10135  includes an outer edge  23180  that forms a portion of the outer periphery of the lower sealing portion  23130   b , and an inner edge  23182  that forms a portion of the oral portion hole  23104 . The first textile membrane  10135 , which forms the upper sealing portion  23130   a  of  FIG.  33 - 2   , may be larger than the first textile membrane  10135  that forms the upper sealing portion  21130   a  of  FIG.  33 - 1   , so that a lower edge  23184  of the first textile membrane  10135  may be aligned with the inner edge  23182  of the second textile membrane  10135 . In other words, substantially all of the perimeter of the oral portion hole  23104  includes the textile membrane  10135 , as opposed to the support structure  23120 . Since the textile membranes  10135  are separate pieces, gaps  23190  filled with the flexible material may still exist between the individual pieces (i.e., between the upper and lower sealing portions  23130   a ,  23130   b ). These gaps  23190  are generally in the longitudinal (e.g., left/right) direction, and extend at least between the outer and inner edges  23180 ,  23182 . The gaps  23190  may be small enough that the patient&#39;s comfort is not effected by their presence (e.g., the patient may not feel the support structure  23120  between the sealing portions  23130   a ,  23130   b , and may instead feel as though only textile material contacts the region around their mouth). In some examples, the gap  23190  may be substantially small, so that the patient may be unable to detect its presence. 
     In the mold, the textile membranes  10135  are arranged in the manner described above, and the flexible material is introduced into the mold to form the patient interface  23000 . Since the lower edge  23184  of the first textile membrane  10135  extends to the inner edge  23182  of the second textile membrane, the flexible material is not introduced into the mold in an area that will be between the naris opening  23103  and the oral portion hole  23104 . In other words, the textile membrane  11035  is the only material that is configured to contact the lip superior in this region (e.g., against the philtrum). Even though the flexible material is able to bend and move, the combination of textile membrane  10135  with the flexible material may reduce the resiliency of the patient interface  23000 . For example, during the molding process, the flexible material may solidify on an interior surface (i.e., within the cavity  23001 ) of the textile membrane  10135 , which increases the thickness of this region. In use, the patient interface  23000  may have more difficulty flexing when the patient&#39;s lip superior contacts this region, which may result in an imperfect seal (i.e., allow for leaks). By removing the need for the support region between the naris openings  23103  and the oral portion hole  23104 , the flexible material does not need to flow into this region, and the thickness of the textile membrane  10135  may not substantially increase. Without the flexible material substantially backing the textile membranes  10135  (e.g., as in  FIG.  33 - 1   ), the textile membrane  10135  may be able to stretch as much as a patient interface made entirely from silicone (e.g., 0.3 mm thick silicone), so that the textile membrane  10135  can achieve substantially the same or similar quality of seal against the patient&#39;s face as with the entirely silicone membrane. 
     In order to manufacture this patient interface  23000 , the textile membranes  10135  may be substantially flat (e.g., have a two-dimensional shape) prior to being placed into the mold, and may receive complex curvatures as a result of being placed into the mold. The liquid flexible material may be applied in order to form the three-dimensional patient interface  23000  (e.g., maintain the complex curvatures in the textile membranes  10135  after being removed from the mold). As described above, any crimp may be applied either before or after the textile membrane  10135  is placed into the mold. 
     As shown in  FIG.  33 - 3   , the patient interface  25000  may be formed using a single textile membrane  10135  when constructing the sealing portion  25130 . In other words, one sheet of textile membrane  10135  is used to seal around both the patient&#39;s nares and the patient&#39;s mouth. The sealing portion  25000  includes an upper sealing portion  25130   a  and a lower sealing portion  25130   b . The outer perimeter of the sealing portion  25130  is substantially the same as the examples mentioned above. However, in this example, the support structure  25120  is not needed to be formed between first and second textile membranes  10135  in order to space them apart and connect them together. Thus, manufacturing may be easier since textile membranes do not have to be properly spaced and filled with the liquid mold material. Additionally, the entire area of the patient interface  25000  that contacts the patient proximate to the mouth and/or nose is constructed from the textile layer  10133 . This may help to improve patient comfort, since the support structure  25120  will not contact the patient proximate to their lip superior. 
     Using the crimp method described above, the likelihood of the single textile membrane  10135  folding onto itself may be reduced or eliminated, even while using a larger piece of textile membrane  10135  (e.g., as compared to the examples shown in  FIGS.  33 - 1  and  33 - 2   ). Particularly, the crimp may reduce or eliminate overlap from occurring in the nasal region, where more curvatures are applied. 
     Additionally, there may not be a significant drop off in the quality of the seal in the resulting patient interface (e.g., as compared to the patient interfaces  21000 ,  23000  of  FIGS.  33 - 1  and  33 - 2   ). The textile membrane  10135  in  FIG.  33 - 3    may include the textile layer  10133  backed with the impermeable layer  10131 , but the overall textile membrane  10135  may be unbacked (e.g., may not be backed with the flexible material of the support structure  25120 ). The textile membrane  10135  may be able to stretch a similar amount as silicone alone (e.g., the impermeable layer  10131  may not significantly reduce the stretchability of the textile membrane  10135 ), and thus may be able to accommodate various contours along the patient&#39;s face (e.g., proximate to the patient&#39;s nasal ala), which may assist in forming the seal. 
     In order to reduce and/or eliminate leaks from occurring while the patient interface  25000  is worn, the shape of the textile membrane  10135  may be modified in order to better accommodate a wider range of patient&#39;s faces, and limit leaks from occurring (see e.g.,  FIGS.  33 - 4  to  33 - 5   ). In one example, the modifications to the textile membrane  10135  may include reducing the radius of curvature in the upper sealing portion  25130   a . Reducing the radius of curvature creates a deeper pocket or nasal radii to receive the patient&#39;s face. For example, the portion of the upper sealing portion  25130   a  that receives the patient&#39;s nose may be narrower, so that when the patient&#39;s nose contacts the textile layer  10133  of the sealing portion  25130 , the textile membrane  10135  is tighter against the patient&#39;s nose. This may be particularly beneficial for patients with smaller and/or narrower noses, who found the sealing portion  25130  with a larger radius of curvature to fit too loosely. Since the textile membrane  10135  are able to flex and deform, patient&#39;s with slightly larger noses may still use the patient interface  25000 , and experience the tight fit (e.g., in order to reduce leaks). 
     Additionally, reducing the radius of curvature of the upper sealing portion  25130   a  may impart a similar shape on the join between the sealing portion  25130  and the support structure  25120 . Since the upper sealing portion  25130   a  and the support structure  25120  are connected, the support structure  25120  may be pulled in the direction of the deep pocket formed in the upper sealing portion  25130   a.    
     Reducing the radius of curvature of the upper sealing portion  25130   a  may impart a similar shape on the lower sealing portion  25130   b , since the upper and lower sealing portions  25130   a ,  25130   b  are formed from one piece of the same textile membrane  10135 . This may specifically reduce the curvature at the inferior end of the lower sealing portion  25130   b  (e.g., region configured to contact the patient&#39;s chin), and provide similar benefits of the deeper pocket described above. 
     In some examples, the radius of curvature may be adjusted about the third axis  13000 . In other words, lateral sides  25250  and/or corner regions  25252  of the patient interface  25000  may be closer together and the patient may have to put their nose further into the cushion assembly  25105  in order to contact the bridge portion  25106 . Additionally, the radius of curvature about the fifth axis  15000  may be increased, so that the curvature is reduced. Increasing the radius of curvature about the fifth axis  15000  helps to maintain the deep curvature about the third axis  13000  because the fifth curvature  50000  does not flatten out the third curvature  30000  (e.g., as a result of the third curvature  30000  and the fifth curvature  50000  being about non-parallel axes). 
     In some examples, the radius of curvature about the third axis may be less than approximately 40 mm. In some examples, the radius of curvature about the third axis may be less than approximately 30 mm. In some examples, the radius of curvature about the third axis may be between approximately 25 mm and approximately 15 mm. In some examples, the radius of curvature about the third axis may be approximately 20 mm. This radius of curvature may be in the textile membrane  10135  only. By reducing the radius of curvature, the patient&#39;s nose is secured within the sealing portion with a tighter fit, and leaking may be reduced. Reducing the radius of curvature also assists the patient to more accurately position their nose against the patient interface  25000  (e.g., to more accurately align their nares with the respective naris openings  25103 ) because there is less room for the patient&#39;s nose to move laterally (e.g., slide and/or shift) against the patient interface  25000 . 
     Leaks may also be prevented and/or reduced by reinforcing the sealing portion  25130  and/or the support structure  25120 . As shown in  FIG.  33 - 6   , support ribs  25186  may be added within the cavity  25001  in order to increase the localized stiffness of the patient interface, and improve the quality of the seal against the patient&#39;s skin. In some examples, a support rib  25186  may be included and/or enlarged in order to increase the localized stiffness. In some examples, the support rib  25186  is enlarged by adding a secondary rib  25188 . In some examples, the support rib  25186  is enlarged by increasing its width. In some examples, the support rib  25186  is enlarged by increasing its length. 
     In one example, the support rib  25186  is molded to the patient interface  25000  within the cavity  25001 , and the secondary rib  25188  is molded to an end of the support rib  25186 . One end of the support rib  25186  may contact the impermeable layer  10131  of the sealing portion  25130 , and the secondary rib  25188  may be molded to the other end of the support rib  25186 . Together, the support rib  25186  and the secondary rib  25188  may form an L-shape. The support rib  25816  may intersect the secondary rib in approximately a perpendicular relationship. The secondary rib  25188  may be parallel to at least a section of the sealing portion  25130 . In the illustrated example, the patient interface may include two support ribs  25186  (although any number is acceptable), which each connect to the sealing portion  25130 . An inner end of each support rib  25186  may extend between approximately 2 mm to approximately 8 mm from an inner edge of the sealing portion  25130  (e.g., a free end proximate an opening to the cavity  25001 ). Each secondary rib  25188  may not extend further so as to not block airflow through the naris openings  25103 . The single secondary rib  25188  may extend between the two support ribs  25186 . The ends of the secondary rib  25188  may connect to the impermeable layer  10131  of the sealing portion  25130  so that the secondary rib  25186  follows an arcuate pattern. In other examples, the secondary rib  25188  may not extend beyond the furthest support ribs  25186 . In other words, the distance between the support ribs  25186  may be approximately the length of the secondary rib  25188 . 
     Including the secondary rib  25188  may improve the sealing of the patient interface  25000  when worn by the patient. Specifically, the stiffness of the sealing portion  25130  may increase. For example, the portion of the sealing portion  25130  configured to contact the lip superior may increase in stiffness as a result of the support ribs  25186  and/or the secondary rib  25188 . The distance between the support ribs  25186 , as well as the number of support ribs  25186 , may affect the total increase in stiffness. In other words, increasing the number of support ribs  25186  and/or decreasing the distance between adjacent support ribs  25186  will increase the stiffness of the sealing portion  25130 . The secondary rib  25188  may act as a backstop, and help limit the compression of the support ribs  25186  (e.g., because of contact with the patient&#39;s face). Increasing the stiffness may help to maintain the shape of the different curvatures, and allow for an ideal fit for the patient. For example, the ribs  25186 ,  25188  assist in maintaining the various radii of curvature of the sealing portion  25130 , and limit creasing or folding from occurring, in order to limiting leaking from occurring. 
     In one example (see e.g.,  FIG.  33 - 7   ), the support ribs  25186  are molded to the patient interface  25000  within the cavity  25001 , with a length that is longer than the length shown in  FIG.  33 - 6   . The support ribs  25186  that have the larger width may be molded with or without the secondary rib  25188 . Increasing the width of the support ribs  25186  decreases the likelihood that the support ribs  25186  will buckle when the patient dons the patient interface  25000 . Thus, the stiffness of the support ribs  25186  will be greater, so there will be a decreased likelihood that the sealing portion  25130  will crease and/or fold. Providing the secondary rib  25188  in conjunction with the wider support ribs  25186  may increase the stiffness of the sealing portion  25130  more than if only one of these modifications were included. However, increasing the thickness of the support ribs  25186  may specifically increase the stiffness in locations where they are attached to the sealing portion  25130  (i.e., a localized increase in stiffness), as opposed to the secondary rib  25188  increasing the stiffness around a larger area of the sealing portion  25130 . 
     In one example, the support ribs  25186  are molded to the patient interface  25000  within the cavity  25001 , with a length that is longer than the length shown in  FIG.  33 - 7   . The longer support ribs  25186  may be molded with or without the secondary rib  25188 , and/or with or without the wider support ribs  25186 . In some examples the length of each of the support ribs  25186  may increase by between approximately 0.1 mm to approximately 8 mm. In some examples the length of each of the support ribs  25186  may increase by between approximately 0.5 mm to approximately 5 mm. In some examples the length of each of the support ribs  25186  may increase by between approximately 1 mm to approximately 3 mm. In some examples the length of each of the support ribs  25186  may increase by approximately 2.5 mm. Lengthening the support ribs  25186  may provide additional support for the portion of the sealing portion  25130  along the third curvature  30000  that may contact the patient&#39;s lip superior. 
     Leaks may also be prevented and/or reduced by changing a shape of the patient interface  25000  (see e.g.,  FIGS.  33 - 8  and  33 - 9   ). For example, the shape and/or contour of the lateral side  25250  and/or the corner regions  25252  of the sealing portion  25130  may be adjusted in order to better conform to the patient&#39;s face (e.g., proximate the corner of nose or nasal ala region). The shape change to the sealing portion  25130  may be caused by changing the shape of the support structure  25120 . Since the support structure  25120  helps to determine where the sealing portion  25130  sits, the shape of the support structure  25120  will change with the shape of the sealing portion  25130 . 
     In some examples, the first curvature  10000  may be adjusted in order to assist in providing an improved seal for the patient. Specifically, the magnitude of the first curvature  10000  may be more negative (i.e., than in previously described examples) about the first axis  11000 . As described above, the lateral side  25250  and/or the corner regions  25252  are disposed on the sealing portion  25130  proximate a transition between the positive curvature about the third axis  13000  (i.e., the third curvature) and the first curvature  10000 . By increasing the magnitude of the first curvature  10000 , the positive dome shape may become more pronounced (e.g., the curvature is steeper). This may decrease the width between the opposing lateral sides  25250 , which may provide a tighter fit for the patient wearing the patient interface  25000 , which in turn could limit the patient&#39;s nose from shifting against the sealing portion  25130 . 
     The shape of the support structure  25120  may also be adjusted in order to limit and/or prevent leaks. Changing the shape of the support structure  25120  (e.g., molding a negative curvature with a larger magnitude) may also impart a shape change on the sealing portion  25130 , since the support structure  25120  is molded to the sealing portion  25130 . This may be specifically shown in  FIG.  33 - 9   , which shows the sealing portion  25130 - 1  after the shape change, and the sealing portion  25130  before the shape change. Creating a larger positive dome shape in the support structure  25120  creates a similar affect as described above with respect to the sealing portion  25130 . 
     As shown in  FIG.  33 - 10   , leaks may be prevented and/or limited by raising the top vector of the patient interface  25000 . Similar to the patient interface  9000  shown in  FIG.  24   , the positioning and stabilizing structure  9300  may engage the patient interface  25000  at four points of contact (i.e., two on either side) with the plenum chamber  25200  and/or the seal-forming structure  25100 . For example, a clip  9301  and a conduit  9900  (see e.g.,  FIG.  24   ) connect on the left side and on the right side of the cushion assembly  25105 . When worn, the patient may adjust a length of the upper strap  9302  and/or the conduits  9900  may stretch (e.g., because of the elastomeric material, because of concertinas, etc.) in order to pull the cushion assembly  25105  against the patient&#39;s face. The tensile force from the positioning and stabilizing structure  9300  assists in forming a seal between the sealing portion  25130  (see e.g.,  FIG.  33 - 3   ) and the patient&#39;s face. 
     The sealing force from the tensile force may be improved by changing the position that the clips  9301  and/or the conduits  9900  connect to the cushion assembly  25105 . For example, changing the location of the vectors may allow the patient to achieve a tighter seal against their face. This may be achieved by spacing the connection points of clip  9301  and of the conduit  9900  further apart (i.e., on either lateral side). In one example, the connection points for the conduits  9900  are raised from the position the example illustrated in  FIG.  24    (e.g., and are closer to the pronasale when worn). Raising where the conduits  9900  connect to the cushion assembly  25105  allows the force supplied by the conduits  9900  to act more directly on the nasal portion (e.g., proximate to the naris openings  25103 ) of the cushion assembly  25105 . Raising the conduit connection point may also cause the forces applied by the conduits to be more localized about the naris openings  25103  (e.g., so that a larger component of the force is applied at that location). Since the patient&#39;s nose includes a variety of contours, concentrating a greater portion of the force from the conduits  9900  may allow the sealing portion  25130  to more accurately compliment the patient&#39;s facial geometry. 
     As shown in  FIG.  33 - 10   , the upper vector may be raised from a first height H 1  to a second height H 2 . The second height H 2  is closer to the naris openings  25103  than the first height H 1 . In some examples the distance between the first height H 1  and the second height H 2  is at least approximately 0.5 mm. In some examples the distance between the first height H 1  and the second height H 2  is between approximately 1 mm and approximately 10 mm. In some examples the distance between the first height H 1  and the second height H 2  is between approximately 2 mm and approximately 8 mm. In some examples the distance between the first height H 1  and the second height H 2  is between approximately 3 mm and approximately 5 mm. In some examples the distance between the first height H 1  and the second height H 2  is approximately 4 mm. 
     As shown in  FIG.  33 - 11   , leaks may be prevented and/or limited by applying inserts  25194  to a surface of the cushion assembly  25105 . In some examples, the inserts  25194  may be constructed from a foam material, and may be disposed on an outer surface of the sealing portion  25130  (e.g., in contact with the textile layer  10133 ). The inserts  25194  may also be disposed on a surface of the support structure  25120  in addition to and/or instead of being disposed on the sealing portion  25130 . 
     The inserts  25194  may be disposed at any location along the cushion assembly  25105 . In the illustrated example, the inserts  25194  are disposed at discrete locations throughout the cushion assembly  25105 , and may specifically be disposed at locations susceptible to leaks. For example, this may be proximate to the lateral side  25150  and/or corner regions  25252 , which is configured to contact the nasal alar region of the patient&#39;s face. The inserts may be able to deform into the complex facial geometry of the patient, in order to form a tighter seal, and reduce gaps through which air can escape. In some examples, the foam is not exposed to the ambient when the cushion assembly  25105  is donned by the patient. Thus, the insert  25194  provides additional material to tighten the fit at some areas, but does not provide passages through itself where air can leak. 
     In some examples, the inserts  25194  are permanently fixed to the cushion assembly  25105 . For example, the inserts  25194  may be glue, or otherwise fixed, to a surface of the cushion assembly  25105  so that a patient is unable to remove the inserts  25194  without potentially damaging the cushion assembly  25105 . In other examples, the inserts  25194  may be removable so that the patient can position them in a variety of locations, or remove the inserts  25194  entirely. 
     Any combination of the leak prevention and/or reduction examples described above and in  FIGS.  33 - 1  to  33 - 11    may be used in a single cushion assembly  25105 . Including several of the above described examples may offer further improvements in preventing and/or limiting leaks from occurring. However, some patients may experience substantially no leaks of pressurized air, and may not require a cushion assembly  25105  with any of these examples. For example, patients with larger noses may have a more secure fit against an unmodified cushion assembly  6105 ,  9105 , or their nose may be too tight against the modified cushion assembly  25105 . 
     5.3.4.1.2 Textile Membrane Examples 
     Below are example properties and structural arrangements of the textile composite used as the material for the textile membrane. 
     5.3.4.1.2.1 Textile Composite Structure 
     Various combinations of textile materials and membrane/film layers may be used. In an example, a three-layer arrangement including a thermoplastic polyurethane (TPU) film disposed between two textile layers (e.g., nylon, nylon and polyester mix, nylon and spandex mix, polyester and spandex mix, or nylon/polyester/spandex mix) is used. The additional textile layer is needed to protect the TPU film from breaking (e.g., during cleaning). 
     In another example, a two-layer arrangement including a textile (e.g., nylon, nylon and polyester mix, nylon and spandex mix, polyester and spandex mix, or nylon/polyester/spandex mix) having a silicone layer (e.g., coated thereon) is used. This composite material may be less expensive than the three-layer arrangement discussed above, since only one layer of textile is needed. 
     In another example, a textile material (e.g., a microfiber or polyurethane material) may be coated with a polyurethane film to form a two-layer arrangement. 
     5.3.4.1.2.2 Textile Material 
     As described above, a number of textile materials maybe used to form the sealing portion, such as nylon, polyester, spandex, nylon and polyester mix, nylon and spandex mix, polyester and spandex mix, nylon/polyester/spandex mix, microfiber or polyurethane. 
     In an example, a nylon material is used. Nylon may provide comfort benefits to the patient as it is softer than polyester. Nylon is also more durable than polyester and therefore provides enhancements in life span and durability. Further, as compared to polyester, nylon has a higher melt temperature and therefore is able to withstand higher temperature manufacturing conditions. 
     In another example, a nylon and polyester mix material is used. This material may be more desirable as it absorbs moisture less readily due to the addition of polyester and therefore reduces irritation to the patient. The nylon and polyester mix is also less expensive than nylon. 
     5.3.4.1.2.3 Textile Composite Total Thickness 
     Thicker textile membrane thicknesses (e.g., 0.5 mm) may be sturdier and provide a less flimsy impress. These textile membranes may be easier to handle during manufacturing as they are less likely to flop around. 
     A middle range thickness (e.g., 0.35 mm to 0.45 mm) may provide a flexible, lightweight structure that is relatively easy to handle during manufacturing and may provide more comfort to the patient than a thicker textile membranes. 
     A thinner textile membrane may provide a very lightweight structure that provides a soft comfortable touch to the patient, but may provide less durability than thicker textile membranes. 
     5.3.4.1.2.4 Knit Structure 
     The textile material of the textile membrane may have a weft knit structure or, alternatively, a warp knit structure, for example. A textile material with a weft and/or warp knit structure may be considered a stretch textile. A weft knit textile may be more desirable as this may provide the material with higher elasticity as compared to a warp knit textiles. This may be advantageous as it may provide more comfort to the patient by stretching as the patient&#39;s face engages the textile membrane thereby reducing the force applied to the patient&#39;s face by the textile membrane. 
     In an example, the weft direction (direction of the course  80 ) may extend in the nose width direction of the textile membrane, since the weft direction may have greater elasticity or stretch. Alternatively, the weft direction may extend in the nose length direction (superior-inferior direction). 
     Additionally, weft knitting is more suitable for producing relatively thin materials, such as discloses herein. Also, weft knitting is generally less cost prohibitive than warp knitting. 
     However, in some examples, warp knitting may be desirable as it provides less shrinkage than weft knit materials. 
     In some examples, the textile membrane may include any knit structure that allows the textile membrane to stretch. 
     In other examples, the textile membrane may include a different structure (e.g., woven), but may still be considered a stretch textile. 
     5.3.4.1.2.5 Knitting Machine 
     A weft knit textile material may have a single jersey knit structure which provides a technical face and a technical back that have different appearances. A single jersey knit may be formed by one set of needles and may provide knit stitches on the technical face (front) and purl stitches on the technical back. In an example, the technical face may form the outer surface of the textile membrane and the air impermeable membrane may be attached to the technical back. Alternatively, the technical face could be oriented towards an inner surface of the textile membrane and have the membrane attached thereto. 
     In an example where the textile membrane includes an air impermeable membrane sandwiched between two textile layers, the technical face of each textile material may form the exposed surfaces of the textile membrane. 
     5.3.4.1.2.6 Textile Weight 
     The textile material may have a weight in the range of 95 grams per square meter (gsm) to 130 gsm (e.g., 105 gsm to 120 gsm, or 110 gsm to 115 gsm, or 105 gsm, or 110 gsm, or 120 gsm). A heavier weight textile (e.g., 120 gsm) may provide a desirable comfortable textile feel even after being coated with a laminate layer due to the weightiness/thickness of the textile. A lighter weight textile (e.g., 105 gsm) may be desirable as it provides a lighter product. 
     5.3.4.1.2.7 Machine Gauge 
     The machine gauge (i.e., the number of stitches per inch) of the textile material may vary. For example, the machine gauge may be in the range of 35 GG to 70 GG (e.g., 44 GG to 60 GG, or 50 GG to 55 GG, or 55 GG to 60 GG, or 44 GG, or 50 GG, or 55 GG, or 60 GG). 
     Using relatively larger gauge materials (e.g., 44 GG) may be desirable as this provides greater options for melange materials. However, a finer gauge materials (e.g., 60 GG) may be desirable as this softer materials which may enhance patient comfort. 
     5.3.4.1.2.8 Aesthetic 
     The textile material may have a solid color aesthetic or a melange aesthetic. A melange material may be considered a material that has been made with more than one color of fabric/textile/yarn, either by using different color fabrics/textiles/yarns or made with different fabrics/textiles/yarns which are then individually dyed. A melange material may be desirable as it may have a greater ability to hide dirt or grime thereby more easily improving the sense of cleanliness of the product. A melange material may also provide benefits during manufacturing as it is easier to visually align the textile knit structure correctly during cutting and/or overmolding. 
     However, a solid color material may be desirable as it provides greater options for finer gauge materials (e.g., 55 GG+) which are softer and therefore more comfortable to the patient. 
     5.4 RPT Device 
     An RPT device  4000  in accordance with one aspect of the present technology comprises mechanical, pneumatic, and/or electrical components and is configured to execute one or more algorithms  4300 , such as any of the methods, in whole or in part, described herein. The RPT device  4000  may be configured to generate a flow of air for delivery to a patient&#39;s airways, such as to treat one or more of the respiratory conditions described elsewhere in the present document. 
     In one form, the RPT device  4000  is constructed and arranged to be capable of delivering a flow of air in a range of −20 L/min to +150 L/min while maintaining a positive pressure of at least 6 cmH 2 O, or at least 10cmH 2 O, or at least 20 cmH 2 O. 
     The RPT device may have an external housing  4010 , formed in two parts, an upper portion  4012  and a lower portion  4014 . Furthermore, the external housing  4010  may include one or more panel(s)  4015 . The RPT device  4000  comprises a chassis  4016  that supports one or more internal components of the RPT device  4000 . The RPT device  4000  may include a handle  4018 . 
     The pneumatic path of the RPT device  4000  may comprise one or more air path items, e.g., an inlet air filter  4112 , an inlet muffler  4122 , a pressure generator  4140  capable of supplying air at positive pressure (e.g., a blower  4142 ), an outlet muffler  4124  and one or more transducers  4270 , such as pressure sensors and flow rate sensors. 
     One or more of the air path items may be located within a removable unitary structure which will be referred to as a pneumatic block  4020 . The pneumatic block  4020  may be located within the external housing  4010 . In one form a pneumatic block  4020  is supported by, or formed as part of the chassis  4016 . 
     The RPT device  4000  may have an electrical power supply  4210 , one or more input devices  4220 , a pressure generator  4140 , and transducers  4270 . Electrical components  4200  may be mounted on a single Printed Circuit Board Assembly (PCBA)  4202 . In an alternative form, the RPT device  4000  may include more than one PCBA  4202 . 
     5.4.1 RPT Device Mechanical &amp; Pneumatic Components 
     An RPT device may comprise one or more of the following components in an integral unit. In an alternative form, one or more of the following components may be located as respective separate units. 
     5.4.1.1 Air Filter(s) 
     An RPT device in accordance with one form of the present technology may include an air filter  4110 , or a plurality of air filters  4110 . 
     In one form, an inlet air filter  4112  is located at the beginning of the pneumatic path upstream of a pressure generator  4140 . 
     In one form, an outlet air filter  4114 , for example an antibacterial filter, is located between an outlet of the pneumatic block  4020  and a patient interface  3000 . 
     5.4.1.2 Muffler(s) 
     An RPT device in accordance with one form of the present technology may include a muffler  4120 , or a plurality of mufflers  4120 . 
     In one form of the present technology, an inlet muffler  4122  is located in the pneumatic path upstream of a pressure generator  4140 . 
     In one form of the present technology, an outlet muffler  4124  is located in the pneumatic path between the pressure generator  4140  and a patient interface  3000 . 
     5.4.1.3 Pressure Generator 
     In one form of the present technology, a pressure generator  4140  for producing a flow, or a supply, of air at positive pressure is a controllable blower  4142 . For example the blower  4142  may include a brushless DC motor  4144  with one or more impellers. The impellers may be located in a volute. The blower may be capable of delivering a supply of air, for example at a rate of up to about 120 litres/minute, at a positive pressure in a range from about 4 cmH 2 O to about 20 cmH 2 O, or in other forms up to about 30 cmH 2 O when delivering respiratory pressure therapy. The blower may be as described in any one of the following patents or patent applications the contents of which are incorporated herein by reference in their entirety: U.S. Pat. Nos. 7,866,944; 8,638,014; 8,636,479; and PCT Patent Application Publication No. WO 2013/020167. 
     The pressure generator  4140  may be under the control of the therapy device controller  4240 . 
     In other forms, a pressure generator  4140  may be a piston-driven pump, a pressure regulator connected to a high pressure source (e.g. compressed air reservoir), or a bellows. 
     5.4.1.4 Transducer(s) 
     Transducers may be internal of the RPT device, or external of the RPT device. External transducers may be located for example on or form part of the air circuit, e.g., the patient interface. External transducers may be in the form of non-contact sensors such as a Doppler radar movement sensor that transmit or transfer data to the RPT device. 
     In one form of the present technology, one or more transducers  4270  are located upstream and/or downstream of the pressure generator  4140 . The one or more transducers  4270  may be constructed and arranged to generate signals representing properties of the flow of air such as a flow rate, a pressure or a temperature at that point in the pneumatic path. 
     In one form of the present technology, one or more transducers  4270  may be located proximate to the patient interface  3000 . 
     In one form, a signal from a transducer  4270  may be filtered, such as by low-pass, high-pass or band-pass filtering. 
     5.4.1.5 Anti-Spill Back Valve 
     In one form of the present technology, an anti-spill back valve  4160  is located between the humidifier  5000  and the pneumatic block  4020 . The anti-spill back valve is constructed and arranged to reduce the risk that water will flow upstream from the humidifier  5000 , for example to the motor  4144 . 
     5.4.2 RPT Device Electrical Components 
     5.4.2.1 Power Supply 
     A power supply  4210  may be located internal or external of the external housing  4010  of the RPT device  4000 . 
     In one form of the present technology, power supply  4210  provides electrical power to the RPT device  4000  only. In another form of the present technology, power supply  4210  provides electrical power to both RPT device  4000  and humidifier  5000 . 
     5.4.2.2 Input Devices 
     In one form of the present technology, an RPT device  4000  includes one or more input devices  4220  in the form of buttons, switches or dials to allow a person to interact with the device. The buttons, switches or dials may be physical devices, or software devices accessible via a touch screen. The buttons, switches or dials may, in one form, be physically connected to the external housing  4010 , or may, in another form, be in wireless communication with a receiver that is in electrical connection to a central controller. 
     In one form, the input device  4220  may be constructed and arranged to allow a person to select a value and/or a menu option. 
     5.5 Air Circuit 
     An air circuit  4170  in accordance with an aspect of the present technology is a conduit or a tube constructed and arranged to allow, in use, a flow of air to travel between two components such as RPT device  4000  and the patient interface  3000 . 
     In particular, the air circuit  4170  may be in fluid connection with the outlet of the pneumatic block  4020  and the patient interface. The air circuit may be referred to as an air delivery tube (see e.g.,  6348  in  FIG.  7   ). In some cases there may be separate limbs of the circuit for inhalation and exhalation. In other cases a single limb is used. 
     In some forms, the air circuit  4170  may comprise one or more heating elements configured to heat air in the air circuit, for example to maintain or raise the temperature of the air. The heating element may be in a form of a heated wire circuit, and may comprise one or more transducers, such as temperature sensors. In one form, the heated wire circuit may be helically wound around the axis of the air circuit  4170 . The heating element may be in communication with a controller such as a central controller. One example of an air circuit  4170  comprising a heated wire circuit is described in U.S. Pat. No. 8,733,349, which is incorporated herewithin in its entirety by reference. 
     5.5.1 Supplementary Gas Delivery 
     In one form of the present technology, supplementary gas, e.g. oxygen,  4180  is delivered to one or more points in the pneumatic path, such as upstream of the pneumatic block  4020 , to the air circuit  4170 , and/or to the patient interface  3000 . 
     5.6 Humidifier 
     In one form of the present technology there is provided a humidifier  5000  (e.g. as shown in  FIG.  5 A ) to change the absolute humidity of air or gas for delivery to a patient relative to ambient air. Typically, the humidifier  5000  is used to increase the absolute humidity and increase the temperature of the flow of air (relative to ambient air) before delivery to the patient&#39;s airways. 
     5.7 Breathing Waveforms 
       FIG.  5    shows a model typical breath waveform of a person while sleeping. The horizontal axis is time, and the vertical axis is respiratory flow rate. While the parameter values may vary, a typical breath may have the following approximate values: tidal volume Vt 0.5 L, inhalation time Ti 1.6 s, peak inspiratory flow rate Qpeak 0.4 L/s, exhalation time Te 2.4 s, peak expiratory flow rate Qpeak −0.5 L/s. The total duration of the breath, Ttot, is about 4 s. The person typically breathes at a rate of about 15 breaths per minute (BPM), with Ventilation Vent about 7.5 L/min. A typical duty cycle, the ratio of Ti to Ttot, is about 40%. 
     5.8 Portable Oxygen Concentrator (POC) 
     Portable oxygen concentrators may take advantage of pressure swing adsorption (PSA). Pressure swing adsorption may involve using one or more compressors to increase gas pressure inside a canister that contains particles of a gas separation adsorbent arranged in a “sieve bed”. As the pressure increases, certain molecules in the gas may become adsorbed onto the gas separation adsorbent. Removal of a portion of the gas in the canister under the pressurized conditions allows separation of the non-adsorbed molecules from the adsorbed molecules. The gas separation adsorbent may be regenerated by reducing the pressure, which reverses the adsorption of molecules from the adsorbent. Further details regarding oxygen concentrators may be found, for example, in U.S. Published Patent Application No. 2009-0065007, published Mar. 12, 2009, and entitled “Oxygen Concentrator Apparatus and Method”, which is incorporated herein by reference. 
     Ambient air usually includes approximately 78% nitrogen and 21% oxygen with the balance comprised of argon, carbon dioxide, water vapor and other trace gases. If a gas mixture such as air, for example, is passed under pressure through a canister containing a gas separation adsorbent bed that attracts nitrogen more strongly than it does oxygen, part or all of the nitrogen will stay in the bed, and the gas coming out of the canister will be enriched in oxygen. When the bed reaches the end of its capacity to adsorb nitrogen, it can be regenerated by reducing the pressure, thereby releasing the adsorbed nitrogen. It is then ready for another cycle of producing oxygen enriched air. By alternating canisters in a two-canister system, one canister can be separating oxygen while the other canister is being purged (resulting in a continuous separation of the oxygen from the nitrogen). In this manner, oxygen enriched air can be accumulated, such as in a storage container or other pressurizable vessel or conduit coupled to the canisters, for a variety of uses including providing supplemental oxygen to patients. 
     5.9 Glossary 
     For the purposes of the present technology disclosure, in certain forms of the present technology, one or more of the following definitions may apply. In other forms of the present technology, alternative definitions may apply. 
     5.9.1 General 
     Air: In certain forms of the present technology, air may be taken to mean atmospheric air, and in other forms of the present technology air may be taken to mean some other combination of breathable gases, e.g. oxygen enriched air. 
     Ambient: In certain forms of the present technology, the term ambient will be taken to mean (i) external of the treatment system or patient, and (ii) immediately surrounding the treatment system or patient. 
     For example, ambient humidity with respect to a humidifier may be the humidity of air immediately surrounding the humidifier, e.g. the humidity in the room where a patient is sleeping. Such ambient humidity may be different to the humidity outside the room where a patient is sleeping. 
     In another example, ambient pressure may be the pressure immediately surrounding or external to the body. 
     In certain forms, ambient (e.g., acoustic) noise may be considered to be the background noise level in the room where a patient is located, other than for example, noise generated by an RPT device or emanating from a mask or patient interface. Ambient noise may be generated by sources outside the room. 
     Automatic Positive Airway Pressure (APAP) therapy: CPAP therapy in which the treatment pressure is automatically adjustable, e.g. from breath to breath, between minimum and maximum limits, depending on the presence or absence of indications of SDB events. 
     Continuous Positive Airway Pressure (CPAP) therapy: Respiratory pressure therapy in which the treatment pressure is approximately constant through a respiratory cycle of a patient. In some forms, the pressure at the entrance to the airways will be slightly higher during exhalation, and slightly lower during inhalation. In some forms, the pressure will vary between different respiratory cycles of the patient, for example, being increased in response to detection of indications of partial upper airway obstruction, and decreased in the absence of indications of partial upper airway obstruction. 
     Flow rate: The volume (or mass) of air delivered per unit time. Flow rate may refer to an instantaneous quantity. In some cases, a reference to flow rate will be a reference to a scalar quantity, namely a quantity having magnitude only. In other cases, a reference to flow rate will be a reference to a vector quantity, namely a quantity having both magnitude and direction. Flow rate may be given the symbol Q. ‘Flow rate’ is sometimes shortened to simply ‘flow’ or ‘airflow’. 
     In the example of patient respiration, a flow rate may be nominally positive for the inspiratory portion of a breathing cycle of a patient, and hence negative for the expiratory portion of the breathing cycle of a patient. Device flow rate, Qd, is the flow rate of air leaving the RPT device. Total flow rate, Qt, is the flow rate of air and any supplementary gas reaching the patient interface via the air circuit. Vent flow rate, Qv, is the flow rate of air leaving a vent to allow washout of exhaled gases. Leak flow rate, Ql, is the flow rate of leak from a patient interface system or elsewhere. Respiratory flow rate, Qr, is the flow rate of air that is received into the patient&#39;s respiratory system. 
     Flow therapy: Respiratory therapy comprising the delivery of a flow of air to an entrance to the airways at a controlled flow rate referred to as the treatment flow rate that is typically positive throughout the patient&#39;s breathing cycle. 
     Humidifier: The word humidifier will be taken to mean a humidifying apparatus constructed and arranged, or configured with a physical structure to be capable of providing a therapeutically beneficial amount of water (H 2 O) vapour to a flow of air to ameliorate a medical respiratory condition of a patient. 
     Leak: The word leak will be taken to be an unintended flow of air. In one example, leak may occur as the result of an incomplete seal between a mask and a patient&#39;s face. In another example leak may occur in a swivel elbow to the ambient. 
     Noise, conducted (acoustic): Conducted noise in the present document refers to noise which is carried to the patient by the pneumatic path, such as the air circuit and the patient interface as well as the air therein. In one form, conducted noise may be quantified by measuring sound pressure levels at the end of an air circuit. 
     Noise, radiated (acoustic): Radiated noise in the present document refers to noise which is carried to the patient by the ambient air. In one form, radiated noise may be quantified by measuring sound power/pressure levels of the object in question according to ISO 3744. 
     Noise, vent (acoustic): Vent noise in the present document refers to noise which is generated by the flow of air through any vents such as vent holes of the patient interface. 
     Oxygen enriched air: Air with a concentration of oxygen greater than that of atmospheric air (21%), for example at least about 50% oxygen, at least about 60% oxygen, at least about 70% oxygen, at least about 80% oxygen, at least about 90% oxygen, at least about 95% oxygen, at least about 98% oxygen, or at least about 99% oxygen. “Oxygen enriched air” is sometimes shortened to “oxygen”. 
     Medical Oxygen: Medical oxygen is defined as oxygen enriched air with an oxygen concentration of 80% or greater. 
     Patient: A person, whether or not they are suffering from a respiratory condition. 
     Pressure: Force per unit area. Pressure may be expressed in a range of units, including cmH 2 O, g-f/cm 2  and hectopascal. 1 cmH 2 O is equal to 1 g-f/cm 2  and is approximately 0.98 hectopascal (1 hectopascal=100 Pa=100 N/m 2 =1 millibar˜0.001 atm). In this specification, unless otherwise stated, pressure is given in units of cmH 2 O. 
     The pressure in the patient interface is given the symbol Pm, while the treatment pressure, which represents a target value to be achieved by the interface pressure Pm at the current instant of time, is given the symbol Pt. 
     Respiratory Pressure Therapy: The application of a supply of air to an entrance to the airways at a treatment pressure that is typically positive with respect to atmosphere. 
     Ventilator: A mechanical device that provides pressure support to a patient to perform some or all of the work of breathing. 
     5.9.1.1 Materials 
     Fiber: A filament (mono or poly), a strand, a yarn, a thread or twine that is significantly longer than it is wide. A fiber may include animal-based material such as wool or silk, plant-based material such as linen and cotton, and synthetic material such as polyester and rayon. A fiber may specifically refer to a material that can be interwoven and/or interlaced (e.g., in a network) with other fibers of the same or different material. 
     Polycarbonate: a thermoplastic polymer of Bisphenol-A Carbonate. 
     Silicone or Silicone Elastomer: A synthetic rubber. In this specification, a reference to silicone is a reference to liquid silicone rubber (LSR) or a compression moulded silicone rubber (CMSR). One form of commercially available LSR is SILASTIC (included in the range of products sold under this trademark), manufactured by Dow Corning. Another manufacturer of LSR is Wacker. Unless otherwise specified to the contrary, an exemplary form of LSR has a Shore A (or Type A) indentation hardness in the range of about 35 to about 45 as measured using ASTM D2240. 
     Textile: A material including at least one natural or artificial fiber. In this specification, a textile may refer to any material that is formed as a network of interwoven and/or interlaced fibers. A type of textile may include a fabric, which is constructed by interlacing the fibers using specific techniques. These include weaving, knitting, crocheting, knotting, tatting, tufting, or braiding. Cloth may be used synonymously with fabric, although may specifically refer to a processed piece of fabric. Other types of textiles may be constructed using bonding (chemical, mechanical, heat, etc.), felting, or other nonwoven processes. Textiles created through one of these processes are fabric-like, and may be considered synonymous with fabric for the purposes of this application. 
     5.9.1.2 Mechanical Properties 
     Resilience: Ability of a material to absorb energy when deformed elastically and to release the energy upon unloading. 
     Resilient: Will release substantially all of the energy when unloaded. Includes e.g. certain silicones, and thermoplastic elastomers. 
     Hardness: The ability of a material per se to resist deformation (e.g. described by a Young&#39;s Modulus, or an indentation hardness scale measured on a standardised sample size).
         ‘Soft’ materials may include silicone or thermo-plastic elastomer (TPE), and may, e.g. readily deform under finger pressure.   ‘Hard’ materials may include polycarbonate, polypropylene, steel or aluminium, and may not e.g. readily deform under finger pressure.       

     Stiffness (or rigidity) of a structure or component: The ability of the structure or component to resist deformation in response to an applied load. The load may be a force or a moment, e.g. compression, tension, bending or torsion. The structure or component may offer different resistances in different directions. The inverse of stiffness is flexibility. 
     Floppy structure or component. A structure or component that will change shape, e.g. bend, when caused to support its own weight, within a relatively short period of time such as 1 second. 
     Rigid structure or component: A structure or component that will not substantially change shape when subject to the loads typically encountered in use. An example of such a use may be setting up and maintaining a patient interface in sealing relationship with an entrance to a patient&#39;s airways, e.g. at a load of approximately 20 to 30 cmH 2 O pressure. 
     As an example, an I-beam may comprise a different bending stiffness (resistance to a bending load) in a first direction in comparison to a second, orthogonal direction. In another example, a structure or component may be floppy in a first direction and rigid in a second direction. 
     5.9.2 Respiratory Cycle 
     Apnea: According to some definitions, an apnea is said to have occurred when flow falls below a predetermined threshold for a duration, e.g. 10 seconds. An obstructive apnea will be said to have occurred when, despite patient effort, some obstruction of the airway does not allow air to flow. A central apnea will be said to have occurred when an apnea is detected that is due to a reduction in breathing effort, or the absence of breathing effort, despite the airway being patent. A mixed apnea occurs when a reduction or absence of breathing effort coincides with an obstructed airway. 
     Breathing rate: The rate of spontaneous respiration of a patient, usually measured in breaths per minute. 
     Duty cycle: The ratio of inhalation time, Ti to total breath time, Ttot. 
     Effort (breathing): The work done by a spontaneously breathing person attempting to breathe. 
     Expiratory portion of a breathing cycle: The period from the start of expiratory flow to the start of inspiratory flow. 
     Flow limitation: Flow limitation will be taken to be the state of affairs in a patient&#39;s respiration where an increase in effort by the patient does not give rise to a corresponding increase in flow. Where flow limitation occurs during an inspiratory portion of the breathing cycle it may be described as inspiratory flow limitation. Where flow limitation occurs during an expiratory portion of the breathing cycle it may be described as expiratory flow limitation. 
     Types of flow limited inspiratory waveforms: 
     (i) Flattened: Having a rise followed by a relatively flat portion, followed by a fall. 
     (ii) M-shaped: Having two local peaks, one at the leading edge, and one at the trailing edge, and a relatively flat portion between the two peaks. 
     (iii) Chair-shaped: Having a single local peak, the peak being at the leading edge, followed by a relatively flat portion. 
     (iv) Reverse-chair shaped: Having a relatively flat portion followed by single local peak, the peak being at the trailing edge. 
     Hypopnea: According to some definitions, a hypopnea is taken to be a reduction in flow, but not a cessation of flow. In one form, a hypopnea may be said to have occurred when there is a reduction in flow below a threshold rate for a duration. A central hypopnea will be said to have occurred when a hypopnea is detected that is due to a reduction in breathing effort. In one form in adults, either of the following may be regarded as being hypopneas:
         (i) a 30% reduction in patient breathing for at least 10 seconds plus an associated 4% desaturation; or   (ii) a reduction in patient breathing (but less than 50%) for at least 10 seconds, with an associated desaturation of at least 3% or an arousal.       

     Hyperpnea: An increase in flow to a level higher than normal. 
     Inspiratory portion of a breathing cycle: The period from the start of inspiratory flow to the start of expiratory flow will be taken to be the inspiratory portion of a breathing cycle. 
     Patency (airway): The degree of the airway being open, or the extent to which the airway is open. A patent airway is open. Airway patency may be quantified, for example with a value of one (1) being patent, and a value of zero (0), being closed (obstructed). 
     Positive End-Expiratory Pressure (PEEP): The pressure above atmosphere in the lungs that exists at the end of expiration. 
     Peak flow rate (Qpeak): The maximum value of flow rate during the inspiratory portion of the respiratory flow waveform. 
     Respiratory flow rate, patient airflow rate, respiratory airflow rate (Qr): These terms may be understood to refer to the RPT device&#39;s estimate of respiratory flow rate, as opposed to “true respiratory flow rate” or “true respiratory flow rate”, which is the actual respiratory flow rate experienced by the patient, usually expressed in litres per minute. 
     Tidal volume (Vt): The volume of air inhaled or exhaled during normal breathing, when extra effort is not applied. In principle the inspiratory volume Vi (the volume of air inhaled) is equal to the expiratory volume Ve (the volume of air exhaled), and therefore a single tidal volume Vt may be defined as equal to either quantity. In practice the tidal volume Vt is estimated as some combination, e.g. the mean, of the inspiratory volume Vi and the expiratory volume Ve. 
     (inhalation) Time (Ti): The duration of the inspiratory portion of the respiratory flow rate waveform. 
     (exhalation) Time (Te): The duration of the expiratory portion of the respiratory flow rate waveform. 
     (total) Time (Ttot): The total duration between the start of one inspiratory portion of a respiratory flow rate waveform and the start of the following inspiratory portion of the respiratory flow rate waveform. 
     Typical recent ventilation: The value of ventilation around which recent values of ventilation Vent over some predetermined timescale tend to cluster, that is, a measure of the central tendency of the recent values of ventilation. 
     Upper airway obstruction (UAO): includes both partial and total upper airway obstruction. This may be associated with a state of flow limitation, in which the flow rate increases only slightly or may even decrease as the pressure difference across the upper airway increases (Starling resistor behaviour). 
     Ventilation (Vent): A measure of a rate of gas being exchanged by the patient&#39;s respiratory system. Measures of ventilation may include one or both of inspiratory and expiratory flow, per unit time. When expressed as a volume per minute, this quantity is often referred to as “minute ventilation”. Minute ventilation is sometimes given simply as a volume, understood to be the volume per minute. 
     5.9.3 Ventilation 
     Adaptive Servo-Ventilator (ASV): A servo-ventilator that has a changeable, rather than fixed target ventilation. The changeable target ventilation may be learned from some characteristic of the patient, for example, a respiratory characteristic of the patient. 
     Backup rate: A parameter of a ventilator that establishes the minimum breathing rate (typically in number of breaths per minute) that the ventilator will deliver to the patient, if not triggered by spontaneous respiratory effort. 
     Cycled: The termination of a ventilator&#39;s inspiratory phase. When a ventilator delivers a breath to a spontaneously breathing patient, at the end of the inspiratory portion of the breathing cycle, the ventilator is said to be cycled to stop delivering the breath. 
     Expiratory positive airway pressure (EPAP): a base pressure, to which a pressure varying within the breath is added to produce the desired interface pressure which the ventilator will attempt to achieve at a given time. 
     End expiratory pressure (EEP): Desired interface pressure which the ventilator will attempt to achieve at the end of the expiratory portion of the breath. If the pressure waveform template Π(Φ) is zero-valued at the end of expiration, i.e. Π(Φ)=0 when Φ=1, the EEP is equal to the EPAP. 
     Inspiratory positive airway pressure (IPAP): Maximum desired interface pressure which the ventilator will attempt to achieve during the inspiratory portion of the breath. 
     Pressure support: A number that is indicative of the increase in pressure during ventilator inspiration over that during ventilator expiration, and generally means the difference in pressure between the maximum value during inspiration and the base pressure (e.g., PS=IPAP−EPAP). In some contexts pressure support means the difference which the ventilator aims to achieve, rather than what it actually achieves. 
     Servo-ventilator: A ventilator that measures patient ventilation, has a target ventilation, and which adjusts the level of pressure support to bring the patient ventilation towards the target ventilation. 
     Spontaneous/Timed (S/T): A mode of a ventilator or other device that attempts to detect the initiation of a breath of a spontaneously breathing patient. If however, the device is unable to detect a breath within a predetermined period of time, the device will automatically initiate delivery of the breath. 
     Swing: Equivalent term to pressure support. 
     Triggered: When a ventilator, or other respiratory therapy device such as an RPT device or portable oxygen concentrator, delivers a volume of breathable gas to a spontaneously breathing patient, it is said to be triggered to do so. Triggering usually takes place at or near the initiation of the respiratory portion of the breathing cycle by the patient&#39;s efforts. 
     5.9.4 Anatomy 
     5.9.4.1 Anatomy of the Face 
     Ala: the external outer wall or “wing” of each nostril (plural: alar) 
     Alare: The most lateral point on the nasal ala. 
     Alar curvature (or alar crest) point: The most posterior point in the curved base line of each ala, found in the crease formed by the union of the ala with the cheek. 
     Auricle: The whole external visible part of the ear. 
     (nose) Bony framework: The bony framework of the nose comprises the nasal bones, the frontal process of the maxillae and the nasal part of the frontal bone. 
     (nose) Cartilaginous framework: The cartilaginous framework of the nose comprises the septal, lateral, major and minor cartilages. 
     Columella: the strip of skin that separates the nares and which runs from the pronasale to the upper lip. 
     Columella angle: The angle between the line drawn through the midpoint of the nostril aperture and a line drawn perpendicular to the Frankfort horizontal while intersecting subnasale. 
     Frankfort horizontal plane: A line extending from the most inferior point of the orbital margin to the left tragion. The tragion is the deepest point in the notch superior to the tragus of the auricle. 
     Glabella: Located on the soft tissue, the most prominent point in the midsagittal plane of the forehead. 
     Lateral nasal cartilage: A generally triangular plate of cartilage. Its superior margin is attached to the nasal bone and frontal process of the maxilla, and its inferior margin is connected to the greater alar cartilage. 
     Lip, lower (labrale inferius): A point on the face between the mouth and supramenton, lying in the median sagittal plane. 
     Lip, upper (labrale superius): A point on the face between the mouth and nose, lying in the median sagittal plane. 
     Greater alar cartilage: A plate of cartilage lying below the lateral nasal cartilage. It is curved around the anterior part of the naris. Its posterior end is connected to the frontal process of the maxilla by a tough fibrous membrane containing three or four minor cartilages of the ala. 
     Nares (Nostrils): Approximately ellipsoidal apertures forming the entrance to the nasal cavity. The singular form of nares is naris (nostril). The nares are separated by the nasal septum. 
     Naso-labial sulcus or Naso-labial fold: The skin fold or groove that runs from each side of the nose to the corners of the mouth, separating the cheeks from the upper lip. 
     Naso-labial angle: The angle between the columella and the upper lip, while intersecting subnasale. 
     Otobasion inferior: The lowest point of attachment of the auricle to the skin of the face. 
     Otobasion superior: The highest point of attachment of the auricle to the skin of the face. 
     Pronasale: the most protruded point or tip of the nose, which can be identified in lateral view of the rest of the portion of the head. 
     Philtrum: the midline groove that runs from lower border of the nasal septum to the top of the lip in the upper lip region. 
     Pogonion: Located on the soft tissue, the most anterior midpoint of the chin. 
     Ridge (nasal): The nasal ridge is the midline prominence of the nose, extending from the Sellion to the Pronasale. 
     Sagittal plane: A vertical plane that passes from anterior (front) to posterior (rear). The midsagittal plane is a sagittal plane that divides the body into right and left halves. 
     Sellion: Located on the soft tissue, the most concave point overlying the area of the frontonasal suture. 
     Septal cartilage (nasal): The nasal septal cartilage forms part of the septum and divides the front part of the nasal cavity. 
     Subalare: The point at the lower margin of the alar base, where the alar base joins with the skin of the superior (upper) lip. 
     Subnasal point: Located on the soft tissue, the point at which the columella merges with the upper lip in the midsagittal plane. 
     Supramenton: The point of greatest concavity in the midline of the lower lip between labrale inferius and soft tissue pogonion 
     5.9.4.2 Anatomy of the Skull 
     Frontal bone: The frontal bone includes a large vertical portion, the squama frontalis, corresponding to the region known as the forehead. 
     Mandible: The mandible forms the lower jaw. The mental protuberance is the bony protuberance of the jaw that forms the chin. 
     Maxilla: The maxilla forms the upper jaw and is located above the mandible and below the orbits. The frontal process of the maxilla projects upwards by the side of the nose, and forms part of its lateral boundary. 
     Nasal bones: The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, the “bridge” of the nose. 
     Nasion: The intersection of the frontal bone and the two nasal bones, a depressed area directly between the eyes and superior to the bridge of the nose. 
     Occipital bone: The occipital bone is situated at the back and lower part of the cranium. It includes an oval aperture, the foramen magnum, through which the cranial cavity communicates with the vertebral canal. The curved plate behind the foramen magnum is the squama occipitalis. 
     Orbit: The bony cavity in the skull to contain the eyeball. 
     Parietal bones: The parietal bones are the bones that, when joined together, form the roof and sides of the cranium. 
     Temporal bones: The temporal bones are situated on the bases and sides of the skull, and support that part of the face known as the temple. 
     Zygomatic bones: The face includes two zygomatic bones, located in the upper and lateral parts of the face and forming the prominence of the cheek. 
     5.9.4.3 Anatomy of the Respiratory System 
     Diaphragm: A sheet of muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity, containing the heart, lungs and ribs, from the abdominal cavity. As the diaphragm contracts the volume of the thoracic cavity increases and air is drawn into the lungs. 
     Larynx: The larynx, or voice box houses the vocal folds and connects the inferior part of the pharynx (hypopharynx) with the trachea. 
     Lungs: The organs of respiration in humans. The conducting zone of the lungs contains the trachea, the bronchi, the bronchioles, and the terminal bronchioles. The respiratory zone contains the respiratory bronchioles, the alveolar ducts, and the alveoli. 
     Nasal cavity: The nasal cavity (or nasal fossa) is a large air filled space above and behind the nose in the middle of the face. The nasal cavity is divided in two by a vertical fin called the nasal septum. On the sides of the nasal cavity are three horizontal outgrowths called nasal conchae (singular “concha”) or turbinates. To the front of the nasal cavity is the nose, while the back blends, via the choanae, into the nasopharynx. 
     Pharynx: The part of the throat situated immediately inferior to (below) the nasal cavity, and superior to the oesophagus and larynx. The pharynx is conventionally divided into three sections: the nasopharynx (epipharynx) (the nasal part of the pharynx), the oropharynx (mesopharynx) (the oral part of the pharynx), and the laryngopharynx (hypopharynx). 
     5.9.5 Patient Interface 
     Anti-asphyxia valve (AAV): The component or sub-assembly of a mask system that, by opening to atmosphere in a failsafe manner, reduces the risk of excessive CO 2  rebreathing by a patient. 
     Elbow: An elbow is an example of a structure that directs an axis of flow of air travelling therethrough to change direction through an angle. In one form, the angle may be approximately 90 degrees. In another form, the angle may be more, or less than 90 degrees. The elbow may have an approximately circular cross-section. In another form the elbow may have an oval or a rectangular cross-section. In certain forms an elbow may be rotatable with respect to a mating component, e.g. about 360 degrees. In certain forms an elbow may be removable from a mating component, e.g. via a snap connection. In certain forms, an elbow may be assembled to a mating component via a one-time snap during manufacture, but not removable by a patient. 
     Frame: Frame will be taken to mean a mask structure that bears the load of tension between two or more points of connection with a headgear. A mask frame may be a non-airtight load bearing structure in the mask. However, some forms of mask frame may also be airtight. 
     Headgear: Headgear will be taken to mean a form of positioning and stabilizing structure designed for use on a head. For example the headgear may comprise a collection of one or more struts, ties and stiffeners configured to locate and retain a patient interface in position on a patient&#39;s face for delivery of respiratory therapy. Some ties are formed of a soft, flexible, elastic material such as a laminated composite of foam and fabric. 
     Membrane: Membrane will be taken to mean a typically thin element that has, preferably, substantially no resistance to bending, but has resistance to being stretched. 
     Plenum chamber: a mask plenum chamber will be taken to mean a portion of a patient interface having walls at least partially enclosing a volume of space, the volume having air therein pressurised above atmospheric pressure in use. A shell may form part of the walls of a mask plenum chamber. 
     Seal: May be a noun form (“a seal”) which refers to a structure, or a verb form (“to seal”) which refers to the effect. Two elements may be constructed and/or arranged to ‘seal’ or to effect ‘sealing’ therebetween without requiring a separate ‘seal’ element per se. 
     Shell: A shell will be taken to mean a curved, relatively thin structure having bending, tensile and compressive stiffness. For example, a curved structural wall of a mask may be a shell. In some forms, a shell may be faceted. In some forms a shell may be airtight. In some forms a shell may not be airtight. 
     Stiffener: A stiffener will be taken to mean a structural component designed to increase the bending resistance of another component in at least one direction. 
     Strut: A strut will be taken to be a structural component designed to increase the compression resistance of another component in at least one direction. 
     Swivel (noun): A subassembly of components configured to rotate about a common axis, preferably independently, preferably under low torque. In one form, the swivel may be constructed to rotate through an angle of at least 360 degrees. In another form, the swivel may be constructed to rotate through an angle less than 360 degrees. When used in the context of an air delivery conduit, the sub-assembly of components preferably comprises a matched pair of cylindrical conduits. There may be little or no leak flow of air from the swivel in use. 
     Tie (noun): A structure designed to resist tension. 
     Vent: (noun): A structure that allows a flow of air from an interior of the mask, or conduit, to ambient air for clinically effective washout of exhaled gases. For example, a clinically effective washout may involve a flow rate of about 10 litres per minute to about 100 litres per minute, depending on the mask design and treatment pressure. 
     5.9.6 Shape of Structures 
     Products in accordance with the present technology may comprise one or more three-dimensional mechanical structures, for example a mask cushion or an impeller. The three-dimensional structures may be bounded by two-dimensional surfaces. These surfaces may be distinguished using a label to describe an associated surface orientation, location, function, or some other characteristic. For example a structure may comprise one or more of an anterior surface, a posterior surface, an interior surface and an exterior surface. In another example, a seal-forming structure may comprise a face-contacting (e.g. outer) surface, and a separate non-face-contacting (e.g. underside or inner) surface. In another example, a structure may comprise a first surface and a second surface. 
     To facilitate describing the shape of the three-dimensional structures and the surfaces, we first consider a cross-section through a surface of the structure at a point, p. See  FIG.  3 B  to  FIG.  3 F , which illustrate examples of cross-sections at point p on a surface, and the resulting plane curves.  FIGS.  3 B to  3 F  also illustrate an outward normal vector at p. The outward normal vector at p points away from the surface. In some examples we describe the surface from the point of view of an imaginary small person standing upright on the surface. 
     5.9.6.1 Curvature in One Dimension 
     The curvature of a plane curve at p may be described as having a sign (e.g. positive, negative) and a magnitude (e.g. 1/radius of a circle that just touches the curve at p). 
     Positive curvature: If the curve at p turns towards the outward normal, the curvature at that point will be taken to be positive (if the imaginary small person leaves the point p they must walk uphill). See  FIG.  3 B  (relatively large positive curvature compared to  FIG.  3 C ) and  FIG.  3 C  (relatively small positive curvature compared to  FIG.  3 B ). Such curves are often referred to as concave. 
     Zero curvature: If the curve at p is a straight line, the curvature will be taken to be zero (if the imaginary small person leaves the point p, they can walk on a level, neither up nor down). See  FIG.  3 D . 
     Negative curvature: If the curve at p turns away from the outward normal, the curvature in that direction at that point will be taken to be negative (if the imaginary small person leaves the point p they must walk downhill). See  FIG.  3 E  (relatively small negative curvature compared to  FIG.  3 F ) and  FIG.  3 F  (relatively large negative curvature compared to  FIG.  3 E ). Such curves are often referred to as convex. 
     5.9.6.2 Curvature of Two Dimensional Surfaces 
     A description of the shape at a given point on a two-dimensional surface in accordance with the present technology may include multiple normal cross-sections. The multiple cross-sections may cut the surface in a plane that includes the outward normal (a “normal plane”), and each cross-section may be taken in a different direction. Each cross-section results in a plane curve with a corresponding curvature. The different curvatures at that point may have the same sign, or a different sign. Each of the curvatures at that point has a magnitude, e.g. relatively small. The plane curves in  FIGS.  3 B to  3 F  could be examples of such multiple cross-sections at a particular point. 
     Principal curvatures and directions: The directions of the normal planes where the curvature of the curve takes its maximum and minimum values are called the principal directions. In the examples of  FIG.  3 B  to  FIG.  3 F , the maximum curvature occurs in  FIG.  3 B , and the minimum occurs in  FIG.  3 F , hence  FIG.  3 B  and  FIG.  3 F  are cross sections in the principal directions. The principal curvatures at p are the curvatures in the principal directions. 
     Region of a surface: A connected set of points on a surface. The set of points in a region may have similar characteristics, e.g. curvatures or signs. 
     Saddle region: A region where at each point, the principal curvatures have opposite signs, that is, one is positive, and the other is negative (depending on the direction to which the imaginary person turns, they may walk uphill or downhill). 
     Dome region: A region where at each point the principal curvatures have the same sign, e.g. both positive (a “concave dome”) or both negative (a “convex dome”). 
     Cylindrical region: A region where one principal curvature is zero (or, for example, zero within manufacturing tolerances) and the other principal curvature is non-zero. 
     Planar region: A region of a surface where both of the principal curvatures are zero (or, for example, zero within manufacturing tolerances). 
     Edge of a surface: A boundary or limit of a surface or region. 
     Path: In certain forms of the present technology, ‘path’ will be taken to mean a path in the mathematical—topological sense, e.g. a continuous space curve from f(0) to f(1) on a surface. In certain forms of the present technology, a ‘path’ may be described as a route or course, including e.g. a set of points on a surface. (The path for the imaginary person is where they walk on the surface, and is analogous to a garden path). 
     Path length: In certain forms of the present technology, ‘path length’ will be taken to mean the distance along the surface from f(0) to f(1), that is, the distance along the path on the surface. There may be more than one path between two points on a surface and such paths may have different path lengths. (The path length for the imaginary person would be the distance they have to walk on the surface along the path). 
     Straight-line distance: The straight-line distance is the distance between two points on a surface, but without regard to the surface. On planar regions, there would be a path on the surface having the same path length as the straight-line distance between two points on the surface. On non-planar surfaces, there may be no paths having the same path length as the straight-line distance between two points. (For the imaginary person, the straight-line distance would correspond to the distance ‘as the crow flies’.) 
     5.9.6.3 Space Curves 
     Space curves: Unlike a plane curve, a space curve does not necessarily lie in any particular plane. A space curve may be closed, that is, having no endpoints. A space curve may be considered to be a one-dimensional piece of three-dimensional space. An imaginary person walking on a strand of the DNA helix walks along a space curve. A typical human left ear comprises a helix, which is a left-hand helix, see  FIG.  3 Q . A typical human right ear comprises a helix, which is a right-hand helix, see  FIG.  3 R .  FIG.  3 S  shows a right-hand helix. The edge of a structure, e.g. the edge of a membrane or impeller, may follow a space curve. In general, a space curve may be described by a curvature and a torsion at each point on the space curve. Torsion is a measure of how the curve turns out of a plane. Torsion has a sign and a magnitude. The torsion at a point on a space curve may be characterised with reference to the tangent, normal and binormal vectors at that point. 
     Tangent unit vector (or unit tangent vector): For each point on a curve, a vector at the point specifies a direction from that point, as well as a magnitude. A tangent unit vector is a unit vector pointing in the same direction as the curve at that point. If an imaginary person were flying along the curve and fell off her vehicle at a particular point, the direction of the tangent vector is the direction she would be travelling. 
     Unit normal vector: As the imaginary person moves along the curve, this tangent vector itself changes. The unit vector pointing in the same direction that the tangent vector is changing is called the unit principal normal vector. It is perpendicular to the tangent vector. 
     Binormal unit vector: The binormal unit vector is perpendicular to both the tangent vector and the principal normal vector. Its direction may be determined by a right-hand rule (see e.g.  FIG.  3 P ), or alternatively by a left-hand rule ( FIG.  3 O ). 
     Osculating plane: The plane containing the unit tangent vector and the unit principal normal vector. See  FIGS.  3 O and  3 P . 
     Torsion of a space curve: The torsion at a point of a space curve is the magnitude of the rate of change of the binormal unit vector at that point. It measures how much the curve deviates from the osculating plane. A space curve which lies in a plane has zero torsion. A space curve which deviates a relatively small amount from the osculating plane will have a relatively small magnitude of torsion (e.g. a gently sloping helical path). A space curve which deviates a relatively large amount from the osculating plane will have a relatively large magnitude of torsion (e.g. a steeply sloping helical path). With reference to  FIG.  3 S , since T 2 &gt;T 1 , the magnitude of the torsion near the top coils of the helix of  FIG.  3 S  is greater than the magnitude of the torsion of the bottom coils of the helix of  FIG.  3 S   
     With reference to the right-hand rule of  FIG.  3 P , a space curve turning towards the direction of the right-hand binormal may be considered as having a right-hand positive torsion (e.g. a right-hand helix as shown in  FIG.  3 S ). A space curve turning away from the direction of the right-hand binormal may be considered as having a right-hand negative torsion (e.g. a left-hand helix). 
     Equivalently, and with reference to a left-hand rule (see  FIG.  3 O ), a space curve turning towards the direction of the left-hand binormal may be considered as having a left-hand positive torsion (e.g. a left-hand helix). Hence left-hand positive is equivalent to right-hand negative. See  FIG.  3 T . 
     5.9.6.4 Holes 
     A surface may have a one-dimensional hole, e.g. a hole bounded by a plane curve or by a space curve. Thin structures (e.g. a membrane) with a hole, may be described as having a one-dimensional hole. See for example the one dimensional hole in the surface of structure shown in  FIG.  3 I , bounded by a plane curve. 
     A structure may have a two-dimensional hole, e.g. a hole bounded by a surface. For example, an inflatable tyre has a two dimensional hole bounded by the interior surface of the tyre. In another example, a bladder with a cavity for air or gel could have a two-dimensional hole. See for example the cushion of  FIG.  3 L  and the example cross-sections therethrough in  FIG.  3 M  and  FIG.  3 N , with the interior surface bounding a two dimensional hole indicated. In a yet another example, a conduit may comprise a one-dimension hole (e.g. at its entrance or at its exit), and a two-dimension hole bounded by the inside surface of the conduit. See also the two dimensional hole through the structure shown in  FIG.  3 K , bounded by a surface as shown. 
     5.10 Other Remarks 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in Patent Office patent files or records, but otherwise reserves all copyright rights whatsoever. 
     Unless the context clearly dictates otherwise and where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit, between the upper and lower limit of that range, and any other stated or intervening value in that stated range is encompassed within the technology. The upper and lower limits of these intervening ranges, which may be independently included in the intervening ranges, are also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the technology. 
     Furthermore, where a value or values are stated herein as being implemented as part of the technology, it is understood that such values may be approximated, unless otherwise stated, and such values may be utilized to any suitable significant digit to the extent that a practical technical implementation may permit or require it. 
     Furthermore, “approximately”, “substantially”, “about”, or any similar term as used herein means+/−5 to +/−10% of the recited value. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this technology belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present technology, a limited number of the exemplary methods and materials are described herein. 
     When a particular material is identified as being used to construct a component, obvious alternative materials with similar properties may be used as a substitute. Furthermore, unless specified to the contrary, any and all components herein described are understood to be capable of being manufactured and, as such, may be manufactured together or separately. 
     It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include their plural equivalents, unless the context clearly dictates otherwise. 
     All publications mentioned herein are incorporated herein by reference in their entirety to disclose and describe the methods and/or materials which are the subject of those publications. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present technology is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates, which may need to be independently confirmed. 
     The terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. 
     The subject headings used in the detailed description are included only for the ease of reference of the reader and should not be used to limit the subject matter found throughout the disclosure or the claims. The subject headings should not be used in construing the scope of the claims or the claim limitations. 
     Although the technology herein has been described with reference to particular examples, it is to be understood that these examples are merely illustrative of the principles and applications of the technology. In some instances, the terminology and symbols may imply specific details that are not required to practice the technology. For example, although the terms “first” and “second” may be used, unless otherwise specified, they are not intended to indicate any order but may be utilised to distinguish between distinct elements. Furthermore, although process steps in the methodologies may be described or illustrated in an order, such an ordering is not required. Those skilled in the art will recognize that such ordering may be modified and/or aspects thereof may be conducted concurrently or even synchronously. 
     It is therefore to be understood that numerous modifications may be made to the illustrative examples and that other arrangements may be devised without departing from the spirit and scope of the technology. 
     5.11 Reference Signs List 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 curve 
                  35 
               
               
                   
                 transition portion 
                  36 
               
               
                   
                 wale 
                  70 
               
               
                   
                 course 
                  80 
               
               
                   
                 basic closed loop warp knit 
                  90 
               
               
                   
                 weft knit 
                  100 
               
               
                   
                 patient 
                 1000 
               
               
                   
                 bed partner 
                 1100 
               
               
                   
                 face 
                 1300 
               
               
                   
                 patient interface 
                 3000 
               
               
                   
                 seal - forming structure 
                 3100 
               
               
                   
                 cavity 
                 3101 
               
               
                   
                 naris openings 
                 3102 
               
               
                   
                 bridge portion 
                 3104 
               
               
                   
                 cushion assembly 
                 3105 
               
               
                   
                 plenum chamber connection opening 
                 3106 
               
               
                   
                 support structure 
                 3120 
               
               
                   
                 lateral support region 
                 3122 
               
               
                   
                 proximate end 
                 3124 
               
               
                   
                 second wall 
                 3126 
               
               
                   
                 textile membrane 
                 3130 
               
               
                   
                 grip pad 
                 3150 
               
               
                   
                 space 
                 3180 
               
               
                   
                 non - usable portion 
                 3184 
               
               
                   
                 area 
                 3188 
               
               
                   
                 area 
                 3190 
               
               
                   
                 inner surface 
                 3194 
               
               
                   
                 outer surface 
                 3195 
               
               
                   
                 outer surface 
                 3196 
               
               
                   
                 inner surface 
                 3197 
               
               
                   
                 plenum chamber 
                 3200 
               
               
                   
                 plenum chamber lateral ends 
                 3202 
               
               
                   
                 plenum chamber connector 
                 3204 
               
               
                   
                 notch 
                 3206 
               
               
                   
                 edge 
                 3208 
               
               
                   
                 slot 
                 3209 
               
               
                   
                 chord 
                 3210 
               
               
                   
                 superior point 
                 3220 
               
               
                   
                 inferior point 
                 3230 
               
               
                   
                 lateral side 
                 3250 
               
               
                   
                 corner regions 
                 3252 
               
               
                   
                 medial subnasale region 
                 3260 
               
               
                   
                 pronasale region 
                 3270 
               
               
                   
                 positioning and stabilizing structure 
                 3300 
               
               
                   
                 lateral portions 
                 3302 
               
               
                   
                 superior portions 
                 3304 
               
               
                   
                 hub 
                 3306 
               
               
                   
                 tab 
                 3308 
               
               
                   
                 posterior strap 
                 3310 
               
               
                   
                 end portion 
                 3311 
               
               
                   
                 sleeves 
                 3312 
               
               
                   
                 lateral end 
                 3314 
               
               
                   
                 headgear tubes 
                 3350 
               
               
                   
                 vent 
                 3400 
               
               
                   
                 structure vent 
                 3402 
               
               
                   
                 structure 
                 3500 
               
               
                   
                 swivel 
                 3502 
               
               
                   
                 depressing buttons 
                 3504 
               
               
                   
                 connection port 
                 3600 
               
               
                   
                 forehead support 
                 3700 
               
               
                   
                 ISO 
                 3744 
               
               
                   
                 RPT device 
                 4000 
               
               
                   
                 external housing 
                 4010 
               
               
                   
                 upper portion 
                 4012 
               
               
                   
                 portion 
                 4014 
               
               
                   
                 panel 
                 4015 
               
               
                   
                 chassis 
                 4016 
               
               
                   
                 handle 
                 4018 
               
               
                   
                 pneumatic block 
                 4020 
               
               
                   
                 air filter 
                 4110 
               
               
                   
                 inlet air filter 
                 4112 
               
               
                   
                 outlet air filter 
                 4114 
               
               
                   
                 muffler 
                 4120 
               
               
                   
                 inlet muffler 
                 4122 
               
               
                   
                 outlet muffler 
                 4124 
               
               
                   
                 pressure generator 
                 4140 
               
               
                   
                 blower 
                 4142 
               
               
                   
                 motor 
                 4144 
               
               
                   
                 anti - spill back valve 
                 4160 
               
               
                   
                 air circuit 
                 4170 
               
               
                   
                 air circuit 
                 4171 
               
               
                   
                 supplementary gas 
                 4180 
               
               
                   
                 electrical components 
                 4200 
               
               
                   
                 single Printed Circuit Board Assembly 
                 4202 
               
               
                   
                 power supply 
                 4210 
               
               
                   
                 input device 
                 4220 
               
               
                   
                 transducer 
                 4270 
               
               
                   
                 humidifier 
                 5000 
               
               
                   
                 patient interface 
                 6000 
               
               
                   
                 cavity 
                 6001 
               
               
                   
                 seal - forming structure 
                 6100 
               
               
                   
                 nasal portion 
                 6101 
               
               
                   
                 oral portion 
                 6102 
               
               
                   
                 naris openings 
                 6103 
               
               
                   
                 oral portion hole 
                 6104 
               
               
                   
                 cushion assembly 
                 6105 
               
               
                   
                 bridge portion 
                 6106 
               
               
                   
                 support structure 
                 6120 
               
               
                   
                 cushion 
                 6121 
               
               
                   
                 cushion 
                 6122 
               
               
                   
                 textile membrane 
                 6130 
               
               
                   
                 sealing portion 
                 6130 
               
               
                   
                 first sealing portion 
                 6131 
               
               
                   
                 second sealing portion 
                 6132 
               
               
                   
                 plenum chamber 
                 6200 
               
               
                   
                 positioning and stabilizing structure 
                 6300 
               
               
                   
                 left arm 
                 6305 
               
               
                   
                 right arm 
                 6307 
               
               
                   
                 joints 
                 6312 
               
               
                   
                 tube 
                 6348 
               
               
                   
                 tube 
                 6350 
               
               
                   
                 inner layer 
                 6352 
               
               
                   
                 outer layer 
                 6354 
               
               
                   
                 textile sheet 
                 6360 
               
               
                   
                 membrane 
                 6362 
               
               
                   
                 tube sheet 
                 6364 
               
               
                   
                 outer covering 
                 6366 
               
               
                   
                 membrane 
                 6368 
               
               
                   
                 membrane 
                 6370 
               
               
                   
                 air passage 
                 6372 
               
               
                   
                 vent 
                 6400 
               
               
                   
                 connection port 
                 6600 
               
               
                   
                 conduit connector 
                 6800 
               
               
                   
                 conduit connector housing 
                 6801 
               
               
                   
                 conduit connection end 
                 6802 
               
               
                   
                 conduit connector inlet hole 
                 6803 
               
               
                   
                 one conduit connector vent hole 
                 6831 
               
               
                   
                 anti - asphyxia valve 
                 6850 
               
               
                   
                 cavity 
                 9001 
               
               
                   
                 seal - forming structure 
                 9100 
               
               
                   
                 nasal portion 
                 9101 
               
               
                   
                 oral portion 
                 9102 
               
               
                   
                 nasal portion holes 
                 9103 
               
               
                   
                 oral portion hole 
                 9104 
               
               
                   
                 cushion assembly 
                 9105 
               
               
                   
                 bridge portion 
                 9106 
               
               
                   
                 support structure 
                 9120 
               
               
                   
                 textile membrane 
                 9130 
               
               
                   
                 first sealing portion 
                 9131 
               
               
                   
                 second sealing portion 
                 9132 
               
               
                   
                 grip pad 
                 9150 
               
               
                   
                 plenum chamber 
                 9200 
               
               
                   
                 plenum chamber hole 
                 9210 
               
               
                   
                 positioning and stabilizing structure 
                 9300 
               
               
                   
                 clip 
                 9301 
               
               
                   
                 upper strap 
                 9302 
               
               
                   
                 lower strap 
                 9303 
               
               
                   
                 connector 
                 9304 
               
               
                   
                 vent 
                 9400 
               
               
                   
                 vent 
                 9404 
               
               
                   
                 connection port 
                 9600 
               
               
                   
                 conduit connector 
                 9800 
               
               
                   
                 conduit 
                 9900 
               
               
                   
                 sleeve 
                 9901 
               
               
                   
                 tie connectors 
                 9902 
               
               
                   
                 connection port housing 
                 9903 
               
               
                   
                 first curvature 
                 10000  
               
               
                   
                 support structure 
                 10120  
               
               
                   
                 sealing portion 
                 10130  
               
               
                   
                 air impermeable material 
                 10131  
               
               
                   
                 textile material 
                 10133  
               
               
                   
                 first layer 
                 10133a 
               
               
                   
                 second layer 
                 10133b 
               
               
                   
                 third layer 
                 10133c 
               
               
                   
                 textile membrane 
                 10135  
               
               
                   
                 first axis 
                 11000  
               
               
                   
                 axis 
                 11500  
               
               
                   
                 second axis 
                 12000  
               
               
                   
                 third axis 
                 13000  
               
               
                   
                 fourth axis 
                 14000  
               
               
                   
                 fifth axis 
                 15000  
               
               
                   
                 second curvature 
                 20000  
               
               
                   
                 patient interface 
                 21000  
               
               
                   
                 cavity 
                 21001  
               
               
                   
                 seal - forming structure 
                 21100  
               
               
                   
                 nasal portion 
                 21101  
               
               
                   
                 oral portion 
                 21102  
               
               
                   
                 naris openings 
                 21103  
               
               
                   
                 oral portion hole 
                 21104  
               
               
                   
                 cushion assembly 
                 21105  
               
               
                   
                 bridge portion 
                 21106  
               
               
                   
                 support structure 
                 21120  
               
               
                   
                 sealing portion 
                 21130  
               
               
                   
                 first sealing portion 
                 21131  
               
               
                   
                 second sealing portion 
                 21132  
               
               
                   
                 plenum chamber 
                 21200  
               
               
                   
                 gap 
                 21190  
               
               
                   
                 patient interface 
                 23000  
               
               
                   
                 cavity 
                 23001  
               
               
                   
                 seal - forming structure 
                 23100  
               
               
                   
                 nasal portion 
                 23101  
               
               
                   
                 oral portion 
                 23102  
               
               
                   
                 naris openings 
                 23103  
               
               
                   
                 oral portion hole 
                 23104  
               
               
                   
                 cushion assembly 
                 23105  
               
               
                   
                 bridge portion 
                 23106  
               
               
                   
                 support structure 
                 23120  
               
               
                   
                 sealing portion 
                 23130  
               
               
                   
                 first sealing portion 
                 23131  
               
               
                   
                 second sealing portion 
                 23132  
               
               
                   
                 inner edge 
                 23182  
               
               
                   
                 lower edge 
                 23184  
               
               
                   
                 gap 
                 23190  
               
               
                   
                 plenum chamber 
                 23200  
               
               
                   
                 patient interface 
                 25000  
               
               
                   
                 cavity 
                 25001  
               
               
                   
                 seal - forming structure 
                 25001  
               
               
                   
                 nasal portion 
                 25101  
               
               
                   
                 oral portion 
                 25102  
               
               
                   
                 naris openings 
                 25103  
               
               
                   
                 oral portion hole 
                 25104  
               
               
                   
                 cushion assembly 
                 25105  
               
               
                   
                 bridge portion 
                 25106  
               
               
                   
                 support structure 
                 25120  
               
               
                   
                 sealing portion 
                 25130  
               
               
                   
                 sealing portion 
                  25130-1 
               
               
                   
                 first sealing portion 
                 25131  
               
               
                   
                 second sealing portion 
                 25132  
               
               
                   
                 support rib 
                 25186  
               
               
                   
                 secondary rib 
                 25188  
               
               
                   
                 insert 
                 25194  
               
               
                   
                 plenum chamber 
                 25200  
               
               
                   
                 lateral side 
                 25250  
               
               
                   
                 corner region 
                 25252  
               
               
                   
                 third curvature 
                 30000  
               
               
                   
                 fourth curvature 
                 40000  
               
               
                   
                 fifth curvature 
                 50000  
               
               
                   
                 arch 
                 60000  
               
               
                   
                 first height 
                 H 1   
               
               
                   
                 second height 
                 H 2   
               
               
                   
                 first impermeable thickness 
                 T I1   
               
               
                   
                 second impermeable thickness 
                 T I2