Patent Publication Number: US-2023149650-A1

Title: Textile seal with silicone layer

Description:
1 CROSS-REFERENCE TO RELATED APPLICATIONS 
     N/A 
     2 BACKGROUND OF THE TECHNOLOGY 
     2.1 Field of the Technology 
     The present technology relates to one or more of the diagnosis, treatment, prevention and amelioration of respiratory-related disorders. The present technology also relates to medical devices or apparatuses, 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, 9 th  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). 
     Cheyne-Stokes Respiration (CSR) is another form of sleep disordered breathing. CSR is a disorder of a patient&#39;s respiratory controller in which there are rhythmic alternating periods of waxing and waning ventilation known as CSR cycles. CSR is characterised by repetitive de-oxygenation and re-oxygenation of the arterial blood. It is possible that CSR is harmful because of the repetitive hypoxia. In some patients CSR is associated with repetitive arousal from sleep, which causes severe sleep disruption, increased sympathetic activity, and increased afterload. See U.S. Pat. No. 6,532,959 (Berthon-Jones). 
     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. 
     Obesity Hyperventilation Syndrome (OHS) is defined as the combination of severe obesity and awake chronic hypercapnia, in the absence of other known causes for hypoventilation. Symptoms include dyspnea, morning headache and excessive daytime sleepiness. 
     Chronic Obstructive Pulmonary Disease (COPD) encompasses any of a group of lower airway diseases that have certain characteristics in common. These include increased resistance to air movement, extended expiratory phase of respiration, and loss of the normal elasticity of the lung. Examples of COPD are emphysema and chronic bronchitis. COPD is caused by chronic tobacco smoking (primary risk factor), occupational exposures, air pollution and genetic factors. Symptoms include: dyspnea on exertion, chronic cough and sputum production. 
     Neuromuscular Disease (NMD) is a broad term that encompasses many diseases and ailments that impair the functioning of the muscles either directly via intrinsic muscle pathology, or indirectly via nerve pathology. Some NMD patients are characterised by progressive muscular impairment leading to loss of ambulation, being wheelchair-bound, swallowing difficulties, respiratory muscle weakness and, eventually, death from respiratory failure. Neuromuscular disorders can be divided into rapidly progressive and slowly progressive: (i) Rapidly progressive disorders: Characterised by muscle impairment that worsens over months and results in death within a few years (e.g. Amyotrophic lateral sclerosis (ALS) and Duchenne muscular dystrophy (DMD) in teenagers); (ii) Variable or slowly progressive disorders: Characterised by muscle impairment that worsens over years and only mildly reduces life expectancy (e.g. Limb girdle, Facioscapulohumeral and Myotonic muscular dystrophy). Symptoms of respiratory failure in NMD include: increasing generalised weakness, dysphagia, dyspnea on exertion and at rest, fatigue, sleepiness, morning headache, and difficulties with concentration and mood changes. 
     Chest wall disorders are a group of thoracic deformities that result in inefficient coupling between the respiratory muscles and the thoracic cage. The disorders are usually characterised by a restrictive defect and share the potential of long term hypercapnic respiratory failure. Scoliosis and/or kyphoscoliosis may cause severe respiratory failure. Symptoms of respiratory failure include: dyspnea on exertion, peripheral oedema, orthopnea, repeated chest infections, morning headaches, fatigue, poor sleep quality and loss of appetite. 
     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 Therapy 
     Various therapies, such as Continuous Positive Airway Pressure (CPAP) therapy, Non-invasive ventilation (NW) and Invasive ventilation (IV) have been used to treat one or more of the above respiratory disorders. 
     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. 
     Non-invasive ventilation (NIV) provides ventilatory support to a patient through the upper airways to assist the patient breathing and/or maintain adequate oxygen levels in the body by doing some or all of the work of breathing. The ventilatory support is provided via a non-invasive patient interface. NIV has been used to treat CSR and respiratory failure, in forms such as OHS, COPD, NMD and Chest Wall disorders. In some forms, the comfort and effectiveness of these therapies may be improved. 
     Invasive ventilation (IV) provides ventilatory support to patients that are no longer able to effectively breathe themselves and may be provided using a tracheostomy tube. In some forms, the comfort and effectiveness of these therapies may be improved. 
     2.2.3 Treatment Systems 
     These therapies may be provided by a treatment system or device. Such systems and devices may also be used to screen, diagnose, or monitor a condition without treating it. 
     A treatment system may comprise a Respiratory Pressure Therapy Device (RPT device), an air circuit, a humidifier, a patient interface, and data management. 
     Another form of treatment system is a mandibular repositioning device. 
     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. 
     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 on 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 of the 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. This can lead to patient discomfort. 
     A seal-forming structure which fits one person may not fit another person. Furthermore, a design which fits a patient at one pressure, or in one position may not be suitable for other pressures or other positions. Some designs may leak when a patient moves, e.g. whilst asleep. 
     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. 
     Furthermore, some manufacturing processes result in undesirable folds, creases or buckles in the seal-forming structure even when not in use. 
     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 pressurised. 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 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. 
     2.2.3.4 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. 
     2.2.3.5 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 focussed 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 
               
               
                   
                   
                 level dB(A) 
                 dB(A) 
                 Year 
               
               
                 Mask name 
                 Mask 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 pressure 
               
               
                 Object 
                 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), electrooculography (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. 
     Clinical experts may be able to 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 diagnosis, 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 diagnosis, amelioration, treatment or prevention of a respiratory disorder. 
     Another aspect of the present technology relates to methods used in the diagnosis, amelioration, treatment or prevention of a respiratory disorder. 
     An aspect of certain forms of the present technology is to provide methods and/or apparatuses that improve the compliance of patients with respiratory therapy. 
     Another aspect of the present technology relates to a seal-forming structure of a patient interface, the seal-forming structure including a textile membrane. 
     In one form, the textile membrane is air impermeable. 
     Another aspect of the present technology relates to a process of manufacturing a patient interface utilizing a flat textile composite to create a textile membrane having a curved shape. 
     Another aspect of the present technology relates to a seal-forming structure of a patient interface, the seal-forming structure including a textile membrane where the seal-forming structure has no (or few) buckles or creases. 
     Another aspect of the present technology is a patient interface comprising a textile membrane including a knitted textile material. 
     In one form the knitted textile material is warp knitted. 
     In one form the knitted textile material is weft knitted. 
     In one form, the textile membrane is stretchy (e.g., equally stretchy) in both vertical and horizontal directions. 
     In one form, the textile membrane is more stretchy in the horizontal direction than in the vertical direction. 
     Another aspect of the present technology pertains to a patient interface having a wide fit range. 
     Another aspect of the present technology relates to a seal-forming structure of a patient interface, the seal-forming structure including a sealing portion (e.g., comprising a textile material) that is held in tension prior to use. 
     Another aspect of the present technology relates to a seal-forming structure of a patient interface, the seal-forming structure including an untensioned textile membrane that is without creases, folds, wrinkles and/or buckles in an outer surface of the textile membrane 
     Another aspect of the present technology relates to a seal-forming structure of a patient interface, the seal-forming structure including a textile membrane having a bridge portion that is slack and/or buckled with excess material. 
     Another aspect of the present technology relates to a cushion assembly for interfacing with a patient&#39;s airways including at least the patient&#39;s nares, the cushion assembly being configured to maintain a therapy pressure above ambient air pressure in use, throughout a patient&#39;s respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing. The cushion assembly may comprise: 1) a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O 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 2) 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 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. 
     In examples: (a) the textile membrane includes a textile material adapted to contact the patient&#39;s face and an air impermeable silicone layer applied thereto, the textile material comprising 1) nylon and/or polyester, and 2) elastane; (b) a yarn count of the nylon and/or polyester is in a range of 20-80 denier; (c) the textile membrane has stretchability in both a direction of the wales and a direction of the course. 
     In further examples: (a) the yarn count of the nylon and/or polyester is in a range of 20-50 denier; (b) a yarn count of the elastane is in a range of 20-120 D; (c) a coefficient of friction of the textile material is in a range 0.7 to 5.0; (d) a mean deviation of surface roughness is in a range 0.7 to 5.0; (e) the textile membrane has the same or similar stretch characteristics in both a wale direction and a course direction of the textile material; (f) the textile membrane has the same or similar tensile strength in both a wale direction and a course direction of the textile material; (g) a thickness of the textile membrane is in the range of 0.2 mm to 0.46 mm. 
     In further examples: (a) the textile material is an elastic weft-knitted textile; (b) the textile material comprises nylon, polyester, or a nylon/polyester composite; (c) the textile material comprises 1) 75% to 85% nylon, polyester, or nylon/polyester composite, and 2) 15% to 25% elastane; (d) a thickness of the textile material is in the range of 0.18 mm to 0.32 mm; (e) the machine gauge of the textile material is in the range of 30 GG to 60 GG; (f) the textile material has a textile weight in the range of 105 gsm to 160 gsm; (g) the textile membrane has the same or similar surface friction in both a wale direction and a course direction of the textile material; (h) the textile material has four-way elasticity; (i) a thickness of the air impermeable silicone layer is in the range of 0.04 mm to 0.125 mm; (j) the textile material has a melange aesthetic; (k) the textile material has a solid color aesthetic. 
     Another aspect of the present technology relates to 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 the patient&#39;s nares. The patient interface may comprise: 1) the cushion assembly according to any of the aspects above; and 2) a positioning and stabilising structure to provide a force to hold the seal-forming structure in a therapeutically effective position on the patient&#39;s head, the positioning and stabilising structure comprising a tie, the tie being constructed and arranged so that at least a portion overlies a region of the patient&#39;s head superior to an otobasion superior of the patient&#39;s head in use. 
     In examples: (a) the patient interface further comprises a vent structure to allow a continuous flow of gases exhaled by the patient from an interior of the cavity to ambient, the vent structure being sized and shaped to maintain the therapeutic pressure in the cavity in use; (b) the plenum chamber and seal-forming structure form an oro-nasal cushion assembly or a nasal cushion. 
     Another aspect of the present technology relates to a method of forming a cushion assembly for a patient interface, the cushion assembly being configured for interfacing with a patient&#39;s airways including at least the patient&#39;s nares, the cushion assembly being configured to maintain a therapy pressure above ambient air pressure in use, throughout a patient&#39;s respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing, said method comprising: 1) providing a textile material having a first side and a second side, the first side of the textile material being configured to contact the patient&#39;s face in use to facilitate delivery of a flow of air at a therapeutic pressure to the patient&#39;s airways; and 2) applying an air impermeable silicone layer to the textile material thereby forming a textile membrane configured 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 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. 
     In examples: (a) the textile material comprises 1) nylon and/or polyester, and 2) elastane; (b) a yarn count of the nylon and/or polyester is in a range of 20-80 denier; (c) the textile membrane has stretchability in both a direction of the wales and a direction of the course. 
     In further examples: (a) the yarn count of the nylon and/or polyester is in a range of 20-50 denier; (b) a yarn count of the elastane is in a range of 20-120 D; (c) a coefficient of friction of the textile material is in a range 0.7 to 5.0; (d) the textile material comprises 1) 75% to 85% nylon, polyester, or nylon/polyester composite, and 2) 15% to 25% elastane; (d) the textile material is an elastic weft-knitted textile. 
     Another aspect of the present technology relates to 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: 1) 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 being adapted to receive a flow of air at the therapeutic pressure for breathing by a patient; and 2) a seal-forming structure having a textile membrane constructed and arranged to form a seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways, said textile membrane having a 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. 
     In examples: (a) the seal-forming structure includes a support structure to support the textile membrane, the support structure being configured to connect to the plenum chamber; and (b) the textile membrane is attached to the support structure along an outer perimeter of the textile membrane in a manner that causes the textile membrane to be in tension prior to use. 
     Another aspect of the present technology relates to 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: 1) a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O 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 2) a seal-forming structure having a textile membrane constructed and arranged to form a seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways, said textile membrane having a 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. The seal-forming structure may include a flexible support structure to support the textile membrane, the support structure being connected to the plenum chamber, the support structure being stiffer than the textile membrane. In use, the textile membrane may be configured to press against the patient&#39;s face such that the patient&#39;s nose is not received in the cavity. The textile membrane may be attached to the support structure along an outer perimeter of the textile membrane such that textile membrane extends radially inwardly beyond the support structure. 
     In examples: (a) the plenum chamber and the support structure comprise silicone and form a one piece structure having a first lateral support section with a first thickness and a second centrally disposed nose base section with a second thickness that is less than the first thickness, and the nose base section is configured to fold or form a pivot point upon engagement of the textile membrane with the patient&#39;s face thereby allowing left and right lateral sides of the support structure to deform inwardly to cradle the patient&#39;s nose; (b) the support structure includes an underlying cushion; (c) the support structure comprises foam; (d) the support structure comprises silicone and the textile membrane is molded to an inner edge of the support structure; (e) the textile membrane has a dome shape in a corner region of the textile membrane; (f) the textile membrane has a saddle shape in a lower central region of the textile membrane that is configured to seal against the patient&#39;s subnasale in use. 
     In further examples: (a) the textile membrane comprises a membrane layer applied to a textile material to make the textile material substantially air impermeable; (b) the textile membrane has a thickness in the range of 0.3 mm to 0.5 mm; (c) the membrane layer has a thickness in the range of 0.05 mm to 0.1 mm; (d) the textile material is weft knit; (e) the weight of the textile material is in the range of 105 gsm to 120 gsm; (f) the machine gauge of the textile material is in the range of 44 GG to 60 GG; (g) the textile material has a melange aesthetic; (h) the textile material has a solid color aesthetic; (i) the membrane layer comprises silicone; (j) the textile material comprises nylon, spandex, or polyester; (k) in use, the therapeutic pressure in the cavity urges the textile membrane towards the patient&#39;s face; (l) the plenum chamber comprises silicone and is formed in one piece with the support structure. 
     In further examples: (a) the patient interface further comprises a positioning and stabilising structure to provide a force to hold the seal-forming structure in a therapeutically effective position on the patient&#39;s head, the positioning and stabilising structure comprising a tie, the tie being constructed and arranged so that at least a portion overlies a region of the patient&#39;s head superior to an otobasion superior of the patient&#39;s head in use; (b) the patient interface further comprises a vent structure to allow a continuous flow of gases exhaled by the patient from an interior of the cavity to ambient, said vent structure being sized and shaped to maintain the therapeutic pressure in the cavity in use; (c) the plenum chamber and seal-forming structure form an oro-nasal cushion assembly; (d) the plenum chamber and seal-forming structure form a nasal cushion. 
     Another aspect of the present technology relates to 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: 1) a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O 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 2) a seal-forming structure having a textile membrane constructed and arranged to form a seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways, said textile membrane having at least one 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. The seal-forming structure may include a flexible support structure to support the textile membrane, the support structure being stiffer than the textile membrane, the support structure being connected to the plenum chamber. At a transition portion, the textile membrane may be attached to the support structure along an outer edge of the textile membrane and an inner edge of the support structure such that textile membrane extends radially inwardly beyond the support structure. At the transition portion, both the support structure and the textile membrane may extend along a curve in a direction from an anterior side of the seal-forming structure to a posterior patient-facing side of the seal-forming structure. 
     In examples: (a) at the transition portion, the support structure and the textile membrane have substantially the same radius of curvature; (b) the textile membrane extends continuously along the curve from the transition portion to the inner edge of the textile membrane; (c) in use, the textile membrane may be configured to press against the patient&#39;s face such that the patient&#39;s nose is not received in the cavity; (d) the at least one hole in the textile membrane comprises two holes, and a bridge portion is disposed between the two holes in the textile membrane; (e) the support structure comprises silicone and the textile membrane is molded to an inner edge of the support structure; (f) the seal-forming structure has a seamless transition along an outer surface thereof from the support structure to the textile membrane. 
     In further examples: (a) the textile membrane comprises a textile material and a membrane layer applied thereto to make the textile material substantially air impermeable; (b) the textile membrane has a thickness in the range of 0.3 mm to 0.5 mm; (c) the textile material is weft knit; (d) the membrane layer comprises silicone; (e) the textile material comprises polyamides (e.g. nylon), spandex, or polyester; (f) in use the therapeutic pressure in the cavity urges the textile membrane towards the patient&#39;s face; (g) the plenum chamber and seal-forming structure form an oro-nasal cushion assembly; (h) the plenum chamber and seal-forming structure form a nasal cushion. 
     Another aspect of the present technology relates to 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: 1) a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O 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 2) a seal-forming structure having a textile membrane constructed and arranged to form a seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways, said textile membrane having at least one 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. The textile membrane may comprise a textile material and a membrane layer applied thereto to make the textile material substantially air impermeable, the textile material may be a weft knit textile. The seal-forming structure may include a flexible support structure to support the textile membrane, the support structure may be connected to the plenum chamber, and the support structure may be stiffer than the textile membrane. The textile membrane may be attached to the support structure along an outer perimeter of the textile membrane such that textile membrane extends radially inwardly beyond the support structure. In use, the textile membrane may be configured to press against the patient&#39;s face such that the patient&#39;s nose is not received in the cavity. The textile membrane may have a dome shape in a corner region of the textile membrane configured to seal against the patient&#39;s subalare, and a saddle shape at a lower central region of the textile membrane configured to seal against the patient&#39;s subnasale. 
     In examples: (a) in use, the therapeutic pressure in the cavity urges the textile membrane towards the patient&#39;s face to assist the textile membrane in forming a seal with the patient&#39;s face; (b) the at least one hole in the textile membrane comprises two holes, a bridge portion is disposed between the two holes in the textile membrane, and the bridge portion is buckled with excess material to allow the textile membrane to expand to accommodate different size noses; (c) the support structure comprises silicone and the textile membrane is molded to an inner edge of the support structure; (d) the plenum chamber comprises silicone and is formed in one piece with the support structure; (e) the textile membrane is attached to the support structure in a manner that causes the textile membrane to be in tension prior to use; (f) a first region of the textile membrane is in tension prior to use and a second region of the textile membrane is untensioned prior to use. 
     In further examples: (a) the textile membrane has four-way elasticity; (b) the textile membrane has a first elasticity in lateral left-right direction and a second different elasticity in a superior-inferior direction, wherein the elasticity in the first direction is greater than the elasticity in the second direction; (c) the membrane layer comprises silicone; (d) the textile material comprises nylon, spandex, or polyester; (e) the plenum chamber and seal-forming structure form an oro-nasal cushion assembly; (f) the plenum chamber and seal-forming structure form a nasal cushion. 
     Another aspect of the present technology relates to a method of forming a cushion assembly for a patient interface, the cushion assembly being configured 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 cushion assembly 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 method comprising: 1) forming an airtight textile composite by applying an air impermeable material to a textile material, the textile composite having a flat shape; 2) cutting the textile composite to desired dimensions according to a particular cushion assembly type to be used; and 3) overmolding a flexible support structure onto the cut textile composite to form a seal-forming structure having a textile membrane such that the textile membrane is attached to the support structure along an outer edge of the textile membrane and an inner edge of the support structure. In the overmolding step, the textile composite may be held in place by vacuum so as to have a non-flat shape during overmolding thereby imparting a curved non-flat shape to the textile membrane. No wrinkles, creases, folds and/or buckles are formed in the textile membrane. 
     In examples: (a) the seal-forming structure has a seamless transition along an outer surface thereof from the support structure to the textile membrane; (b) at a transition portion, the textile membrane is attached to the support structure along an outer edge of the textile membrane and an inner edge of the support structure such that textile membrane extends radially inwardly beyond the support structure, and at the transition portion, both the support structure and the textile membrane extend along a curve in a direction from an anterior side of the seal-forming structure to a posterior patient-facing side of the seal-forming structure; (c) two holes are formed in the textile membrane, and a bridge portion is disposed between the two holes in the textile membrane, and the bridge portion is buckled with excess material to allow the textile membrane to expand to accommodate different size noses; (d) the support structure comprises silicone. 
     Another aspect of the present technology relates to a seal-forming structure of a patient interface, the seal-forming structure including a support structure and a sealing portion, the support structure supporting the sealing portion, wherein the sealing portion is attached to the support structure along an outer perimeter of the sealing portion such that the sealing portion extends radially inwardly beyond the support structure, and wherein, in use, the sealing portion 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 sealing portion is in tension due to reactive stress of the support structure and/or a resilient stretch characteristic of the textile which thereby causes the sealing portion to exert a force against the patient&#39;s face. 
     According to a further aspect of the present technology, the sealing portion comprises textile. In a further example, the patient interface comprises a plenum chamber and the support structure is configured to connect to the plenum chamber, the plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O above ambient air pressure, the 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. In a further example, the sealing portion is constructed and arranged to form a seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways, the sealing portion having a hole formed therein such that the flow of air at the therapeutic pressure is delivered to at least an entrance to the patient&#39;s nares, the seal-forming structure being constructed and arranged to maintain the therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use. In a further example, the support structure comprise silicone and/or a thermoplastic elastomer. 
     According to a further aspect of the present technology, a wall structure of the support structure between the sealing portion and the plenum chamber has a first section with a first thickness and a second section with a second thickness that is different than the first thickness. 
     Another aspect of the present technology relates to a seal-forming structure of a patient interface, the seal-forming structure including a support structure and a sealing portion, the support structure supporting the sealing portion, wherein the sealing portion is attached to the support structure along an outer perimeter of the sealing portion in a manner that causes the sealing portion to be in tension prior to use. 
     According to a further aspect of the present technology, the sealing portion comprising a textile material. In a further example, the patient interface comprises a plenum chamber and the support structure is configured to connect to the plenum chamber, the plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O above ambient air pressure, the 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. In a further example, the sealing portion is constructed and arranged to form a seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways, the sealing portion having a hole formed therein such that the flow of air at the therapeutic pressure is delivered to at least an entrance to the patient&#39;s nares, the seal-forming structure being constructed and arranged to maintain the therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use. In a further example, the support structure comprise silicone and/or a thermoplastic elastomer. 
     Another aspect of the present technology relates to a seal-forming structure of a patient interface, the seal-forming structure including a support structure and a sealing portion, the support structure supporting the sealing portion, wherein the sealing portion comprises a textile material and is attached to the support structure along an outer perimeter of the sealing portion, wherein the support structure is more rigid than the sealing portion, the support structure having a first section with a first thickness and a second section with a second thickness that is different than the first thickness. 
     According to a further aspect of the present technology, the support structure comprises silicone and/or a thermoplastic elastomer, the patient interface comprises a plenum chamber and the support structure is configured to connect to the plenum chamber, the plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O above ambient air pressure, the 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. In a further example, the sealing portion is constructed and arranged to form a seal with a region of the patient&#39;s face surrounding an entrance to the patient&#39;s airways, the sealing portion having a hole formed therein such that the flow of air at the therapeutic pressure is delivered to at least an entrance to the patient&#39;s nares, the seal-forming structure being constructed and arranged to maintain the therapeutic pressure in the cavity throughout the patient&#39;s respiratory cycle in use. 
     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 the 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 patient interface that may be washed in a home of a patient, e.g., in soapy water, without requiring specialised cleaning equipment. 
     Another aspect of the present technology relates to a treatment system used for treatment of sleep disordered breathing, comprising: 1) the patient interface according to any of the above aspects; 2) a respiratory pressure therapy (RPT) device to supply breathable gas at positive pressure; and 3) an air delivery tube to pass the breathable gas from the RPT device to the patient interface. 
     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 Treatment 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. 
       4.5 Patient Interface According to the Present Technology 
         FIG.  5    is a perspective view of a patient interface according to an example of the present technology worn by a patient. 
         FIG.  6    is a perspective view of a patient interface according to another example of the present technology worn by a patient. 
         FIG.  7    is a cross-sectional view of the positioning and stabilising structure along the line  7 - 7  in  FIG.  6   . 
         FIG.  8    is an enlarged view of a portion of the positioning and stabilising structure of  FIG.  7   . 
         FIG.  9    is an enlarged view of a portion of the positioning and stabilising structure of  FIG.  7   . 
         FIG.  10    is a front view of the cushion assembly of  FIG.  5    positioned on a patient&#39;s face. 
         FIG.  11    is a front view of the cushion assembly of  FIG.  5   . 
         FIG.  12    is a top perspective view of the cushion assembly of  FIG.  5   . 
         FIG.  13    is a top view of the cushion assembly of  FIG.  5   . 
         FIG.  14    is a side view of the cushion assembly of  FIG.  5   . 
         FIG.  15    is a front view of the cushion assembly of  FIG.  5   . 
         FIG.  16    is a side view of the cushion assembly of  FIG.  5   . 
         FIG.  17    is a top view of the cushion assembly of  FIG.  5   . 
         FIG.  18    is a front view of a cushion assembly according to another example of the present technology positioned on a patient&#39;s face. 
         FIG.  19    is a top view of the cushion assembly of  FIG.  18   . 
         FIG.  20    is a front view of the cushion assembly of  FIG.  18   . 
         FIG.  21    is a bottom view of the cushion assembly of  FIG.  18   . 
         FIG.  22    is a side perspective view of the cushion assembly of  FIG.  18   . 
         FIG.  23    is a front view of a cushion assembly according to another example of the present technology. 
         FIG.  24    is a bottom perspective view of the cushion assembly of  FIG.  23   . 
         FIG.  25    is a side perspective view of the cushion assembly of  FIG.  23   . 
         FIG.  26    is a top perspective view of the cushion assembly of  FIG.  23   . 
         FIG.  27    is a rear perspective view of the cushion assembly of  FIG.  23   . 
         FIG.  28    is a top perspective view of a cushion assembly according to another example of the present technology. 
         FIG.  29    is a front view of the cushion assembly of  FIG.  28   . 
         FIG.  30    is a side perspective view of the cushion assembly of  FIG.  28   . 
         FIG.  31    is a rear perspective view of the cushion assembly of  FIG.  28   . 
         FIG.  32    is a bottom view of the cushion assembly of  FIG.  28   . 
         FIG.  33    is a front perspective view of a cushion assembly according to another example of the present technology. 
         FIG.  33 - 1    is a front perspective view of a cushion assembly according to another example of the present technology. 
         FIG.  33 - 2    is a cross-sectional view along the line  33 - 2 - 33 - 2  in  FIG.  33 - 1   . 
         FIG.  33 - 3    is a cross-sectional view along the line  33 - 3 - 33 - 3  in  FIG.  33 - 1   . 
         FIG.  33 - 4    is an enlarged detail taken from  FIG.  33 - 2   . 
         FIG.  34    is a cross-sectional view of the cushion assembly of  FIG.  33   . 
         FIGS.  34 - 37    are front perspective views of cushion assemblies having grip pads disposed on the textile membrane according examples of the present technology. 
         FIG.  38    is a perspective view of a patient interface according to another example of the present technology worn by a patient. 
         FIG.  39    is a perspective view of a patient interface according to another example of the present technology. 
         FIG.  40    is a perspective view of the patient interface of  FIG.  39    worn by a patient. 
         FIG.  41    is a side view of the patient interface of  FIG.  40   . 
         FIG.  42    is a front perspective view of the patient interface of  FIG.  40   . 
         FIG.  43    is a front view of the cushion assembly of the patient interface of  FIG.  39   . 
         FIG.  44    is a top view of the cushion assembly of  FIG.  39   . 
         FIG.  45    is a bottom view of the cushion assembly of  FIG.  39   . 
         FIG.  46    is a front perspective view of the cushion assembly of  FIG.  39   . 
         FIG.  47    is a rear perspective view of the cushion assembly of  FIG.  39   . 
         FIG.  48    is a side perspective view of the cushion assembly of  FIG.  39   . 
         FIG.  49    is a front perspective view of the cushion assembly of  FIG.  39    showing an interior portion of the cushion assembly. 
         FIG.  50    is a front view of the cushion assembly of  FIG.  39    showing an interior portion of the cushion assembly. 
         FIG.  51    is a rear view of a cushion assembly according to an example of the present technology. 
         FIG.  52    is a front view of the cushion assembly of  FIG.  51   . 
         FIG.  53    is a cross-sectional view of the cushion assembly of  FIG.  51   . 
         FIGS.  54 - 56    are front perspective views of cushion assemblies having grip pads disposed on the textile membrane according examples of the present technology. 
         FIG.  57    is a perspective view of a patient interface  30000  according to an example of the present technology. 
         FIG.  58    is a perspective view of the patient interface  30000  of  FIG.  57    while worn by a patient. 
         FIG.  59    is a cross section view of the patient interface  30000  shown in  FIG.  57   . 
         FIG.  60    is a side view of the patient interface  30000  of  FIG.  57    while worn by a patient. 
         FIG.  61    is a front perspective view of the cushion assembly  30105  of  FIG.  57   . 
         FIG.  62    is a rear perspective view of the cushion assembly  30105  of  FIG.  57   . 
         FIG.  63    is a front view of the frame  30350  of  FIG.  57   . 
         FIG.  64    is a back view of the frame  30350  of  FIG.  57   . 
         FIG.  65    is a back view of the patient interface  30000  of  FIG.  57    while worn by a patient. 
         FIG.  66    is view of straps of the positioning and stabilising structure  30300  of the patient interface  30000  of  FIG.  57   . 
         FIG.  67    is a perspective view of a patient interface according to another example of the present technology worn by a patient. 
         FIG.  68    is a side view of the patient interface of  FIG.  67   . 
         FIG.  69    is an exploded view of the patient interface shown in  FIG.  67    showing the cushion assembly, frame assembly, arm covers, and elbow assembly; 
         FIG.  70    is a front exploded view of a cushion assembly according to an example of the present technology. 
         FIG.  71    is a rear exploded view of the cushion assembly of  FIG.  70   . 
         FIG.  72    is a front view of the cushion assembly of the patient interface of  FIG.  67   . 
         FIG.  73    is a front perspective view of the cushion assembly of  FIG.  72   . 
         FIG.  74    is a rear perspective view of the cushion assembly of  FIG.  72   . 
         FIG.  75    is a top perspective view of the cushion assembly of  FIG.  72   . 
         FIG.  76    is a bottom perspective view of the cushion assembly of  FIG.  72   . 
         FIG.  77    is a side perspective view of the cushion assembly of  FIG.  72   . 
         FIG.  78    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.  79    is a schematic illustration depicting a patient&#39;s face being presented to a textile membrane in light tension prior to use. 
         FIG.  80    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.  81    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.  82    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. 
         FIG.  83    is a cutaway cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  84    is a cutaway cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  85    is a cutaway cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  86    is a cutaway cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  87    is a partial cross-sectional view of a sealing portion and support structure of a cushion assembly with an external biasing portion according to an example of the present technology. 
         FIG.  88    is a partial cross-sectional view of a sealing portion and support structure of a cushion assembly with an internal biasing portion according to an example of the present technology. 
         FIG.  89    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  90 A  is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  90 A- 1    is an enlarged view of a section of the sealing portion of the cushion assembly of  FIG.  90 A . 
         FIG.  90 B  is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  91    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  92    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  93    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  94    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  95    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  96    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  97    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  98    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  99    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  100    is a partial cross-sectional view of a cushion assembly according to an example of the present technology. 
         FIG.  101    is cross-sectional view of a sealing portion modular assembly according to an example of the present technology. 
         FIG.  102    is a partial cross-sectional view of a cushion assembly incorporating the sealing portion modular assembly of  FIG.  101    according to an example of the present technology. 
         FIG.  103    is a perspective view of a modular support structure according to an example of the present technology. 
         FIGS.  104  and  105    show a process of molding a sealing portion to a supporting structure according to an example of the present technology. 
         FIG.  106    is a side view of a sealing portion modular assembly formed by the process illustrated in  FIGS.  104  and  105   . 
         FIGS.  107  and  108    illustrate a one size fits all cushion assembly according to an example of the present technology. 
         FIGS.  109  and  110    illustrate a custom made cushion assembly fabricated by utilizing a three-dimensional profile obtained by scanning a patient&#39;s face according to an example of the present technology. 
         FIG.  111    is a front perspective view of a cushion assembly according to another example of the present technology. 
         FIG.  112    is a rear perspective view of the seal-forming structure of the cushion assembly of  FIG.  111   . 
         FIGS.  113  and  114    depict a knitting process. 
         FIG.  115    illustrates a warp knitted textile according to an example of the present technology. 
         FIG.  116    illustrates a weft knitted textile according to an example of the present technology. 
         FIG.  117    is a functional block diagram illustrating a process of overmolding a support structure onto a textile composite to form a seal-forming structure with a textile membrane according to an example of the present technology. 
         FIG.  118    is a schematic illustration of a sealing portion according to another example of the present technology. 
         FIG.  119    is a cross-sectional perspective view of a sealing portion according to an example of the present technology. 
         FIG.  120    is an enlarged cross-sectional view of the sealing portion of FIG. 
     
    
    
     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 the step of 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 Treatment Systems 
     In one form, the present technology comprises an apparatus or device for treating a respiratory disorder. The apparatus or device may comprise an RPT device  4000  for supplying pressurised air to the patient  1000  via an air circuit  4170  to a patient interface  3000 , e.g., see  FIGS.  1 A to  1 C . 
     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 facilitate the supply of air at positive pressure to the airways. 
     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 Plenum Chamber 
     The plenum chamber 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 is positioned in close proximity to an adjacent surface of the face. Actual contact with the face is provided by the seal-forming structure. The seal-forming structure may extend in use about the entire perimeter of the plenum chamber. In some forms, the plenum chamber and the seal-forming structure are formed from a single homogeneous piece of material. In an example, the plenum chamber may be constructed from a flexible material (e.g., silicone) and may be formed as a one-piece structure with the support structure (e.g., from any of the materials described herein as suitable for the support structure and/or plenum chamber). In an example, the seal-forming structure may be an extension of the plenum chamber or formed as a part of the plenum chamber such that the plenum chamber encompasses the seal-forming structure. In such an example, the support structure and textile membrane may be considered part of the plenum chamber. 
     5.3.2 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. liquid silicone rubber (LSR) (or “silicone”). 
     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.  5  to  77   , the seal-forming structure has a sealing portion that comprises a textile material, which may covered the entirety or a portion of the seal-forming structure. In some forms, the textile may comprise a material formed of a network of fibres and being 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 is 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.  78   , in some forms a textile membrane may comprise an air impermeable material  10131  formed on an inner surface of a textile material  10133 . The air impermeable material can in some forms be laminated onto the textile material. The air impermeable material and textile material can in some forms be selected such that the resulting textile membrane can exhibit a predetermined overall elasticity, or a resistance to elasticity, as required. For example, the addition of the air impermeable material (or membrane layer) may add elasticity (or stretchiness) to the textile material such that the resulting textile membrane has increased stretchability. 
     In some forms, the membrane 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 to form an effective seal, the textile material and/or the resulting textile membrane may have a material spring constant and spring length such that the textile membrane is more compliant than the patient&#39;s skin that engages the textile membrane. This may advantageously improve the comfort of the mask, and reduce the formation of localized pressure “hot spots.” 
     In some forms, the surface of the textile material 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 and reduce friction relative to the patient&#39;s face  1300 . The textile material 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 to grip or rub against contacted regions of the patient&#39;s face, in use. Such rubbing or gripping may cause the textile membrane to be distorted or deformed thereby reducing the effectiveness of the seal and allowing air to leak undesirably from the device. 
     In some forms, the textile material of the textile membrane can have an overall thickness of 0.275 mm or less. 
     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  5100 ). 
     5.3.2.1 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 (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 may have properties such that it is capable of elongating in at least one dimension. The textile membrane can be held under a tension force across the support structure prior to and/or during use. Prior to use, the textile membrane can be either permanently attached (e.g., molded) or attached as a removable module to the support structure in such a way that it is pre-tensioned and lightly stretched. 
     Alternatively, the textile 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. Due to manufacturing, the textile polymers can shrink such that the inherent pre-tension in the textile membrane is lost however the textile membrane may remain substantially wrinkle free. 
       FIG.  79    illustrates an example wherein the textile membrane has a light tension in both the X and Y directions through the textile surface. Before the patient&#39;s face  1300  (such as a nose) approaches and depresses the textile membrane  3130 , the textile membrane is adapted to form a constant surface without interruptions such as creases, folds or wrinkles in the textile material prior to the contact between the patient&#39;s face  1300  and the seal-forming structure  3100 . In some forms, this can be accomplished by the application of the light pre-tension, or by moulding the textile membrane such that it is substantially free of any leak causing wrinkles. This can be advantageous in ensuring that the textile membrane forms a smooth and continuous seal on and around the patient&#39;s face  1300 . 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. This can also be advantageous in ensuring the textile membrane remains under a minimum threshold of tension as it is forced against the patient&#39;s face  1300  ( FIG.  80   ). 
     In some forms, regions of the textile membrane can be pre-tensioned and lightly stretched while other regions of the textile membrane can remain slack. For example, in some forms the subnasal region can be pre-tensioned whilst the region that cups the outer sides of the nostrils and/or the patient&#39;s mouth could remain tension-free (e.g., with excess material) so as to form a saddle region or valley shape prior to use. This 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. In another example, the side of nose region and/or the nasal bridge region 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 another example a bridge portion (e.g., bridge portion  3104 ) extending between two naris openings may be untensioned, slack and/or buckled with excess material prior to use, as shown for example in  FIG.  33 - 1   . A bridge portion (e.g.,  3104 ) with excess material may allow the textile membrane to expand (e.g., in the superior-inferior (height) direction to accommodate different size noses. 
     In some forms, instead of having a region that is pre-tensioned, the textile membrane may be formed to be substantially free of leak causing wrinkles. This may be advantageous as it may be difficult to form substantially leak free complex three-dimensional shapes from a slack textile membrane, or from a textile membrane that is provided with excess non-tensioned material. The untensioned textile membrane may be more comfortable is some arrangements as it may apply less pressure on the patient&#39;s face. 
     In some forms, the textile membrane may be in a substantially tension-free state and formed onto the support structure or directly onto the plenum chamber in such a manner so as to remain untensioned and/or slack. In an example, such a textile membrane may still maintain an unwrinkled state so as to avoid leaks in the seal with the patient&#39;s face. An untensioned and/or unwrinkled textile membrane may in some forms utilise a cushion support (e.g., underlying cushion, seal support region (e.g., support structure) and/or air pressure within the cavity to enable an effective seal to be formed with a patient&#39;s face. 
     In some forms, the tensioned and/or unwrinkled state (see  FIGS.  80  and  81   ) in the textile membrane may be maintained so as to maintain sealing contact with the patient&#39;s face  1300  by one or a combination of the following:
         a) the pre-applied tensile stress of the textile membrane and the additional applied tensile stress as the patient&#39;s face  1300  engages the textile membrane;   b) the pre-formed state of the textile membrane formed as a non-tensioned, yet substantially constant surface, without leak causing interruptions such as creases, folds, buckles or wrinkles in the textile membrane.   c) the rigidity of the support structure and/or plenum chamber, and the ability of the support structure and/or plenum chamber to accommodate and react to the applied tensile stress as the patient&#39;s face  1300  engages the textile membrane; and   d) the additional applied loading of the air pressure from within the cavity against the inner surface of the textile membrane. The interior air pressure can apply additional tensile stress against the interior surface of the textile membrane so as to further stretch and stress the textile membrane against the patient&#39;s face  1300  (e.g., creating a pressure-assisted seal).       

     By retaining the textile membrane under tensile stress and/or in a unwrinkled state continuously prior to and during use, the textile membrane 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 on the patient&#39;s face  1300 . 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 is pulled a small distance away from the patient&#39;s face  1300 , the applied loading of the air pressure from within the plenum chamber can assist the textile membrane in retaining an effective seal. The applied loading of the air pressure can be sufficient so as to elastically stretch the textile membrane 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 may be held under tension by a relatively stiffer support structure. In various forms, the support structure can be formed from for example, any of silicone, PU foam, PU solid material or another suitable materials. In some forms, the support structure may be relatively less stiff than a shell or frame of the plenum chamber. 
     In some forms, the magnitude of the tensile stress can vary across the textile membrane of the seal-forming structure as required. For example, there may be a region of stress concentration proximal to one or more holes in the textile membrane through which treatment is administered or in wider stretches of material. 
     In some forms, the seal-forming structure can utilize a number of different cushion configurations including a single air assisted textile membrane, a double air assisted textile membrane, a textile membrane with compression support, or a textile membrane with TPU/TPE/Si support. In some forms, the cushion configuration of the seal-forming structure may be formed such that it can advantageously provide a “one-size-fits-most” solution. 
     In examples, the seal-forming structure and plenum chamber 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 may be configured to generate an effective seal across the patient&#39;s pronasale, as shown for example in  FIG.  58   . In some forms, the textile membrane may be configured to generate an effective seal against the subnasale portion of the patients nose such that the textile membrane does not engage the pronasale, as shown for example in  FIG.  40   . 
     In some forms, the stretching and/or maintenance of an unwrinkled state of the textile membrane so as to conform to the patient&#39;s face  1300 , in use, may apply stress on the walls of the support structure. This stress can pull the walls of the support structure inwardly towards one another in use. In some forms, the support structure may be adapted to resist the applied stress load so as to prevent an inward deformation. Thus, the rigidity of the support structure may apply further stress to the textile membrane which in turn may cause elastic stretching of the textile membrane, in use. 
     In some forms, such as illustrated in  FIGS.  87  and  88   , the support structure may include a pleat, fold or gusset (e.g., seal biasing portions  10140 ,  10140 ′) that utilizes the internal air pressure to dynamically support the textile membrane. This may advantageously provide further support to the textile membrane when under dynamic loads (e.g. tube drags). In other forms, the pleat, fold or gusset may utilise internal air pressure to decouple dynamic loads (e.g. tube drags) from the seal forming structure. In some forms, the air pressure within the cavity may apply a load against the inside surface of the textile membrane to create further tensile stress such that the textile membrane substantially fills the depressed contours of a patient&#39;s face  1300  (e.g. around the sides of the nose). In some forms, the elasticity of the textile membrane, when combined with the applied load of the internal air pressure, can elastically stretch the textile membrane 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 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.  35 - 37  and  54 - 56   , the textile membrane may have one or more grip pads  29150 ,  31150  arranged thereon. In an example, the grip pads  29150 ,  31150  may be configured to be either substantially flat along the patient facing surface of the textile membrane. In other examples, the grip pads  29150 ,  31150  may be embossed such that the grip pad may form a bead or rim that protrudes slightly above the surface of the textile membrane. In some forms, the grip pads  29150 ,  31150  may have a high coefficient of friction. In some forms, the grip pads may have a determined shape (e.g., ovular (see  FIGS.  35 ,  37 ,  54 , and  56   ), circular, square, etc.). In some forms, the grip pads may be elongate (see  FIGS.  35  and  54   ). In some forms, the grip pads  29150 ,  31150  may be linear. In some forms, the grip pads may be arranged in a pattern across the surface of the seal-forming structure  3100 . In some forms, the grip pads may be arranged sporadically across the surface of the seal-forming structure  3100  (see  FIGS.  37  and  56   ). In some forms, the grip pads may be arranged to form a perimeter proximal to the peripheral edges of the textile membrane (see  FIGS.  34 ,  35 ,  54  and  55   ). In some forms, the grip pads  29150 ,  31150  that form a perimeter can be in the form of a dotted line (see  FIGS.  35  and  54   ). In some forms, the grip pads that form a perimeter can be in the form of a solid line (see  FIGS.  36  and  55   ). In some forms, the grip pads 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 may assist a textile membrane in gripping a patient&#39;s face. In an example, the grip pads are formed as a relatively thin layer of silicone applied to the surface of the textile membrane. 
     In some forms, the textile membrane may be integrated to the support structure by attaching (e.g., molding) an outer edge (e.g., outer perimeter) of the textile membrane around a lip of the curved edges (i.e., inner edge) of the support structure. In an example, the textile membrane may be slightly angled “inwardly” toward the mask interior. In an example, the textile membrane is attached so as to provide a front face of the seal-forming structure. That is, the support structure forms the portion of the seal-forming structure that curves from an anterior side of the seal-forming structure to the posterior face-contacting side (see  FIG.  11   ). In this way, the textile membrane can avoid having portions that curve around from the posterior side to the anterior side. By this arrangement, the textile membrane may be presented only along a front face of the seal-forming structure, as shown for example in  FIGS.  11 - 17   ). This arrangement may be advantageous since the textile membrane may not need to be folded or cut to blend around the corners of the support structure. This may be beneficial in reducing the occurrence of protruding folds or wrinkles in the textile membrane (which may cause leakage) thereby improving the performance of the seal. 
     In some forms, the textile membrane may be attached to an outer edge of the textile membrane such that the textile membrane forms part of the portion of the seal-forming structure that curves from the anterior side of the seal-forming structure to the posterior face-contacting side (see  FIGS.  33 - 1  to  33 - 4 ,  73  and  74    for example). This may present more of the textile membrane surface (as opposed to the support structure) for engagement with the patient&#39;s face, which may improve comfort. In an example, the textile membrane is attached to the support structure 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. As can be seen, in some examples, at a transition portion  36 , the support structure and the textile membrane 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 to the posterior side of the seal-forming structure (see  FIGS.  33 - 1  to  33 - 4   ). The textile membrane may have a predefined curvature imparted thereto such that a portion of the textile membrane not directly supported by the support structure extends along the curve  35  ( FIGS.  33 - 2  to  33 - 4   ). 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 which may help the textile membrane 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.  33 - 1   . The dome shape may help prevent creases, wrinkles, folds, and buckles from forming in the textile membrane which may help avoid the creation of leak paths. Also, the dome shape may help the textile reach into hard to seal areas of the patient&#39;s face, such as the corner of nose regions. The textile membrane  29130  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.  33 - 1   . 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 in the direction of the curve  35  may vary in different regions of the cushion assembly along an outer perimeter of the textile membrane. For example, as shown in  FIG.  33 - 2   , the textile membrane  29130  in the medial pronasale region  3270  may have different curvature in the direction of the curve  35  than the textile membrane in the medial subnasale region  3260 . In the  FIG.  33 - 2    example, the textile membrane in the medial pronasale region  3270  may a relatively larger (e.g., smaller radius) curvature (e.g., negative curvature in an inferior-superior direction along curve  35 ) than the curvature (e.g., negative curvature in an inferior-superior direction along curve  35 ) 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 may be different that the curvature at the medial pronasale region  3270  and/or medial subnasale region  3260 . The nasal portion of the cushion assemblies  14105 ,  30105 ,  31105 , as shown for example in  FIGS.  43 ,  52  and  61   , may have similar dome and saddle shape features. 
     In the  FIG.  73    example, the curvature of the textile membrane  16230  from the connection with the support structure  16220  (e.g., at the transition portion) may continue to the inner edge of the textile membrane. For example, the textile membrane may have a dome shape or saddle shape at the inner edge of the textile membrane in certain regions of the cushion. 
     In some forms, the textile membrane may be slightly angled or curved inwardly toward the mask interior (e.g., positive curvature in a left-right direction), as shown for example in  FIGS.  11 - 17 ,  23 - 26  and  3 - 37   . In some forms, the textile membrane may form a dome shape over the support structure, as shown for example in  FIGS.  19 - 22  and  43 - 50   . It is noted that any of the cushion assemblies disclosed herein may have the textile membrane attached to an outer edge of the textile membrane such that the textile membrane forms part of the portion of the seal-forming structure 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.  33 - 1   , such that, for example, the textile membrane  6130  of cushion assembly  6105  may have more of a dome shape by virtue of a more convex shape from one lateral side to the other lateral side. 
     In some forms where the textile membrane is not under continuous tension (prior to and/or during use) or is non-elastic, the textile membrane 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 being thinner and having a lower structural stiffness than silicone membrane. 
     In some forms, the textile membrane 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 some forms, a pleat or fold section can be formed along a cushion assembly (e.g., in the textile membrane and/or the support structure) that may provide a dynamic force/support or decoupling region. 
     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. 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. 
     5.3.2.2 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. 
     5.3.2.3 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. 
     5.3.2.4 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. 
     5.3.2.5 Forehead Region 
     In one form, the seal-forming structure 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. 
     5.3.2.6 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. 
     5.3.3 Nasal Cushion 
     Referring to  FIGS.  5 - 14   , a patient interface  3000 ,  6000  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.  FIGS.  15 - 17    show a cushion assembly  5105  including a seal-forming structure  5100  and a plenum chamber  3200  in accordance with a second example of the present technology.  FIGS.  18 - 22    show a cushion assembly  6105  including a seal-forming structure  6100  and a plenum chamber  3200  in accordance with a third example of the present technology.  FIGS.  23 - 27    show a cushion assembly  7105  including a seal-forming structure  7100  and a plenum chamber  3200  in accordance with a fourth example of the present technology. Referring to  FIGS.  28 - 32    a cushion assembly  8105  including a seal-forming structure  8100  and a plenum chamber  3200  is shown in accordance with a fifth example of the present technology.  FIG.  3    shows a patient interface  9000  with a cushion assembly  9105  including a seal-forming structure  9100  and frame  9200  in accordance with a sixth example of the present technology. 
       FIGS.  11 - 14    include broken lines demarcating regions of different thickness, and it should be understood that these are only nominal boundaries, not actual structures. 
     The examples of seal-forming structures  3100 ,  5100 ,  6100 ,  7100 ,  8100 ,  9100  described in the preceding paragraphs 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 structures 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 structures may also engage the patient&#39;s face at least above the upper vermillion. Thus, the exemplary seal-forming structures may seal against the patient&#39;s lip superior in use. Furthermore, the patient&#39;s mouth may remain uncovered by the seal-forming structures of the depicted examples such that the patient may breathe freely, i.e., directly to atmosphere, without interference from the seal-forming structure. 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 from an inferior edge of the textile membrane at a medial subnasale region to a superior edge of the textile membrane at a medial pronasale region may be less than a width of the cushion in a left-right direction from a lateral edge of the textile membrane to the other lateral edge of the textile membrane (see  FIGS.  33  and  33 - 1    for example). 
     Examples of a nasal cradle cushion, e.g., the exemplary seal-forming structures disclosed herein, may include a superior saddle or concave region that has positive curvature across the cushion. Also, a nasal cradle cushion 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 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. These two surfaces on the patient&#39;s face may form a nasolabial angle between them (see  FIG.  2 E ). A cradle cushion may be shaped to have a nasolabial angle within the range of 90 degrees to 120 degrees. 
     Furthermore, the exemplary seal-forming structures may also be shaped and dimensioned such that no portion of the seal-forming structure enters into the patient&#39;s nares during use. 
     Plenum Chamber 
     Referring to  FIGS.  5 - 17   , 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 the entire perimeter of the plenum chamber  3200 . 
     In certain forms of the present technology, the plenum chamber  3200  is constructed from a relatively rigid material (e.g., polycarbonate) as compared to the seal-forming structure. Alternatively, 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 (e.g., from any of the materials described herein as suitable for the support structure and/or plenum chamber). In an example, the seal-forming structure may be an extension of the plenum chamber or formed as a part of the plenum chamber such that the plenum chamber encompasses the seal-forming structure. In such an example, the support structure and textile membrane may be considered part of the plenum chamber. In another example, the plenum chamber  3200  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, and help improve compliance with therapy. The use of a transparent material can aid a clinician to observe how the patient interface is located and functioning. 
     In certain forms of the present technology, the plenum chamber  3200  is constructed from a translucent material. The use of a translucent material can reduce the obtrusiveness of the patient interface, and help improve compliance with therapy. 
       FIGS.  5  and  10 - 17    show examples of the seal-forming structure  3100  with the plenum chamber  3200 . The seal-forming structure  3100  may include a plenum chamber 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 . 
     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 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 . 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  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. 
     The plenum chambers  3200  shown in  FIGS.  18 - 32    according to the third, fourth and fifth examples of the present technology may be similar or identical to the plenum chamber of  FIGS.  10 - 17   . It should also be appreciated that one or more aspects of the present technology may be combinable with one or more aspects of: U.S. Provisional Application No. 62/764,992, filed Aug. 20, 2018 and entitled “Patient Interface” or PCT/AU2019/050873, filed Aug. 20, 2019, each of which is hereby incorporated herein by reference in its entirety. For instance, the plenum chamber of the present technology may be identical to the plenum chamber in any of the embodiments of the &#39;992 or &#39;837 application. Additionally, the seal-forming structures disclosed herein may replace any of the seal-forming structures in any of the patient interfaces disclosed in the &#39;992 or &#39;873 application, and the seal-forming structures of the present technology may include any of the features of the seal-forming structures in any of the embodiments of the &#39;992 or &#39;873 application. 
     In the example of  FIGS.  28 - 32   , the plenum chamber  13200  has a plenum chamber lateral end  3202 , plenum chamber connector  3204 , notch  3206 , chamfered edge  3208 , and slot  3209  similar to the plenum chamber  3200  described above. However, the vent  3400  may be provided by a vent insert  13400  that attaches, removably or permanently, to the plenum chamber  13200  (e.g., by insertion into an opening in the plenum chamber). It is noted that any of the other examples may have a vent insert (e.g., the vent  3400  in plenum chamber  3200  of  FIGS.  10 - 27    may be provided by a vent insert  13400  such as shown in  FIGS.  28 - 32   ). 
     In the example of  FIG.  38   , the frame  9200  may include a centrally located connection for an air circuit  4170 . The frame may also include headgear attachment portions  9210  at lateral sides thereof. The seal-forming structure  9100  may be connected to the frame  9200  by spaced-apart connectors  9122 , which may include a clip on the seal-forming structure and a receiving connector on the frame. 
     Seal-Forming Structure of the Present Technology 
     The seal-forming structures  3100 ,  5100 ,  6100 ,  7100 ,  8100 ,  9100 ,  29100  may each include a support structure  3120 ,  6120 ,  7120 ,  8120 ,  9120 ,  29120  that provides support to a sealing portion  3130 ,  5130 ,  6130 ,  7130 ,  8130 ,  9130 ,  29130  (e.g., a textile membrane). The sealing portion is configured to sealingly engage the patient&#39;s face. Also, depending on the size and contours of the patient&#39;s nose, in the examples of  FIGS.  5 - 27   , the support structure may also sealingly engage the patient&#39;s face. 
     The exemplary seal-forming structures  3100 ,  5100 ,  6100 ,  7100 ,  8100 ,  9100 ,  29100  while different in various aspects to be described further below, may each include a support structure having at least two regions (e.g., two, three or four 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  FIG.  59   , portions (d1) of the support structure may be thicker than portions (d2) of the support structure. For example, portions (d1) may be adjacent to or connecting to the plenum chamber and portions (d2) may be adjacent to or connecting to the sealing portion so as to provide structural stability at the connection with the plenum chamber 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 sealing portion has 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 providing a taut textile membrane prior to and/or during use. In an alternative example, a single hole may be used to provide the flow of air to both of the patient&#39;s nares. 
     The seal-forming structure  3100 , as described above, may include a plenum chamber connection opening where the seal-forming structure  3100  is sealingly joined to the plenum chamber  3200 . In the examples of  FIGS.  5 - 38   , the support structure  3120 ,  5120 ,  6120 ,  7120 ,  8120 ,  9120 ,  29120  is connected directly to the plenum chamber or frame. Thus, the support structure may include an opening where the support structure is sealingly joined to the plenum chamber  3200 . 
     The support structure may be less rigid than the plenum chamber  3200  and may be constructed from silicone, foam (e.g., polyurethane foam) (see  FIGS.  28 - 32   ), polyurethane solid material, thermoplastic elastomers (e.g., thermoplastic polyurethane), suitable plastics, or other suitable materials, as will be described later. Further, the sealing portion may be less rigid than the support structure 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 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 material layered, coated or otherwise applied thereon. 
     The support structure may have an aperture formed therein providing an inner edge of the support structure along which the sealing portion (e.g., an outer perimeter of the sealing portion) may be attached to the support structure such that the sealing portion extends radially inwardly of the seal-forming structure beyond or to a further extent than the support structure, as shown for example in  FIGS.  11 - 27  and  33 - 38   . For example, the sealing portion may be molded around the inner edge of the support structure or connected to the support structure in other suitable ways, as will be described later. However, in the alternative example of  FIGS.  28 - 32   , the sealing portion  8130  may be layered onto the support structure  8120  (e.g., foam). 
     Referring to  FIGS.  11 - 14   , 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 lateralmost 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. 
     Additionally, the lateral support regions  3122  may provide sufficient rigidity to ensure adequate sealing (e.g., by the lateral support regions  3122 ) in 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. Thus, sufficient stiffness in the lateral support regions  3122  may ensure that the seal-forming structure  3100  can be urged into the subalare region by tension forces from the positioning and stabilising structure  3300  without collapsing. The lateral support regions  3122  may lie on the patient&#39;s face in a region inferior to the ala of the patient&#39;s nose as well as inferior and laterally outwards of the patient&#39;s nose, for example, between the nasolabial sulcus and the regions of the lip superior located inferior to the ala. 
     The seal-forming structure  5100  in the example of  FIGS.  15 - 17    may have a sealing portion  5130  that is expanded as compared to the sealing portion  3130  in  FIGS.  11 - 14   . That is, the support structure  5120  is reduced and the sealing portion  5130  is expanded in the seal-forming structure  5100  such that the sealing portion  5130  may be configured to engage the subalare region of the patient&#39;s face in use. As a result, the seal-forming structure  5100  may be more flexible and compliant so as to more readily conform to the patient&#39;s facial contours. 
     Turning to  FIGS.  18 - 22   , the seal-forming structure in this example is arranged to provide a larger cavity  3101  such that the sealing portion  6130  protrudes further from the plenum chamber in a direction towards the patient&#39;s face in use by creating more tension in the sealing portion thereby causing the sealing portion to balloon outwards. In use, the patient&#39;s nose is able to press against the sealing portion  6130  in the direction towards the cavity  3101  and the plenum chamber  3200  causing the sealing portion  6130  to stretch and invert such that space created by the cavity  3101  receives the patient&#39;s nose thereby allowing the sealing portion  6130  to seal above the patient&#39;s pronasale, as shown in  FIG.  18   . In contrast, the sealing portions  3130 ,  5130  seal below the patient&#39;s pronasale, as shown in  FIG.  10   . 
     The sealing portion  7130  in the example of  FIGS.  23 - 27    is also configured to seal above the patient&#39;s pronasale due to the height of the cushion. The sealing portion  7130  is configured to seal further in the direction of the sellion along the ridge of the nose as compared to the sealing portion  6130 . 
     In the example cushion assembly of  FIGS.  28 - 32   , the support structure  8120  may be provided by a foam material layered onto the plenum chamber  3200 . The sealing portion  8130  may be layered directly onto the support structure. The support structure  8120  may extend across the plenum chamber connection opening except for a pair of holes formed therein corresponding to the naris opening  3102  in the sealing portion  8130 . This arrangement may provide a compression type seal against the patient&#39;s face wherein the cushion assembly  8105  is pulled towards the patient&#39;s face by headgear causing the seal-forming structure  8100  to conform to the patient&#39;s facial contours through compression of the support structure  8120 . 
     The cushion assembly  8105  is configured to seal against an underside of the patient&#39; nose. The seal-forming structure  8100  includes an end portion  8122  that curves around a posterior portion of the plenum chamber  3200  and is configured to engage the patient&#39;s lip superior in use. 
     Referring to  FIGS.  33 - 37   , cushion assembly  29105  is similar to cushion assembly  3105 , but may extend further in a lateral left-right direction. Cushion assembly  29105  includes seal-forming structure  29100 , support structure  29120  and sealing portion  29130 . Referring to  FIG.  33 - 1   , cushion assembly  29105 - 1  is similar to cushion assembly  29105 , but may have a textile membrane  29105  formed such that the textile membrane forms part of the portion of the seal-forming structure that curves from the anterior side of the seal-forming structure to the posterior face-contacting side, as described earlier. 
     As described earlier,  FIGS.  35 - 37    show grip pads  29150  on the surface of the textile membrane. 
     In the  FIG.  38    example, the sealing portion  9130  is arranged to seal above the patient&#39;s pronasale. 
     5.3.3.1 Positioning and Stabilising Structure 
     The cushion assembly  3105 ,  5105 ,  6105 ,  7105 ,  8105 ,  29105  of the patient interface  3000 ,  6000  of the present technology may be held in sealing position in use by the positioning and stabilising structure  3300 . The cushion assembly  9105  of the patient interface  9000  may be held in sealing position in use by the positioning and stabilising structure  9300 . 
     In one form the positioning and stabilising structure  3300 ,  9300  provides a retention force at least sufficient to overcome the effect of the positive pressure in the cavity  3101  to lift off the face. 
     In one form the positioning and stabilising structure provides a retention force to overcome the effect of the gravitational force on the patient interface. 
     In one form the positioning and stabilising structure provides a retention force as a safety margin to overcome the potential effect of disrupting forces on the patient interface, 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 ,  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 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 comprises at least one strap having a rectangular cross-section. In one example the positioning and stabilising structure comprises at least one flat strap. 
     In one form of the present technology, a positioning and stabilising structure 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 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 ,  9300  is provided with a decoupling portion located between an anterior portion of the positioning and stabilising structure, and a posterior portion of the positioning and stabilising structure. 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 and disrupting the seal. 
     In one form of the present technology, a positioning and stabilising structure 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 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 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 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 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 ,  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 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. 
     5.3.3.1.1 Positioning and Stabilising Structure of the Present Technology 
       FIG.  5    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. 
     In an alternative example shown in  FIG.  6   , patient interface  6000  includes a positioning and stabilizing structure  6300  having at least one tube  6350  that is formed of a textile material (e.g., one or more sheets or layers of textile material) and receives pressurized air from air delivery tube  6348  via connection port  6600 . The tube  6350  includes left arm  6305  and right arm  6307 . 
     In some forms, 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, but faces away from the patient that may be referred to as the outer layer  6354 . The inner layer and the outer layer may each be secured to each other along the edges of the inner layer and the outer layer such that a channel or passageway is formed between the seams of the inner layer and the outer layer. That is, the space between the seams remains unattached and forms an air passage  6372 . The inner layer and the outer layer 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 of tube. For example, in some forms the inner and outer layers may be formed such that no additional material such as glue or stitching, is necessary to join the inner and outer layers together. 
     Each of the inner layer and the outer layer may include an interior surface and an exterior surface. The interior surface of the inner layer is the surface that faces the exterior layer. The interior surface of the exterior layer is the surface that faces the interior layer. Likewise, the exterior surface of the outer layer faces away from the interior layer and the exterior surface of the inner layer faces away from the outer layer. 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.  7   , and in particular  FIG.  8   , 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.  9   , 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 . 
     It should also be appreciated that one or more aspects of the present technology may be combinable with one or more aspects of: U.S. Provisional Application No. 62/821,878, filed Mar. 21, 2019 and entitled “Textile Headgear Tubing for a Patient Interface” or PCT/AU2019/050655, filed Jun. 25, 2019, each of which is hereby incorporated herein by reference in its entirety. For instance, the positioning and stabilizing structure of the present technology may be identical to the positioning and stabilizing structure in any of the embodiments of the &#39;968 or &#39;655 application. Additionally, the cushion assemblies or seal-forming structures disclosed herein may replace any of the cushion assemblies or seal-forming structures in any of the patient interfaces disclosed in the &#39;968 or &#39;655 application. 
     In another example shown in  FIG.  38   , patient interface  9000  includes a positioning and stabilizing structure  9300  having a pair of side portions extending between the patient&#39;s eye and ear on respective sides of the patient&#39;s head. The side portions may include a hole or other connector for connecting with the headgear attachment portions  9210  of the frame  9200 . The positioning and stabilizing structure  9300  also includes a rear strap  9310  extending around a rear portion of the patient&#39;s head, and a crown strap  9312  extending over a crown section of the patient&#39;s head. 
     5.3.3.2 Vent 
     In one form, the patient interface  3000 ,  6000 ,  9000  includes a vent  3400  constructed and arranged to allow for the washout of exhaled gases, e.g. carbon dioxide, as shown for example in  FIG.  5   . 
     In certain forms the vent  3400  is configured to allow a continuous vent flow from an interior of the cavity  3101  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 centre, especially since the cross-section of the plenum chamber  3200  in the depicted examples is smallest at the centre 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. 
       FIGS.  31  and  32    show an alternative example of the vent  3400  in which holes are provided to a vent insert  13400  that attaches, removably or permanently, to the plenum chamber  3200  at a vent insert opening. The vent insert  13400  may be constructed from a material that is more flexible than the material of the plenum chamber  3200 . 
     5.3.3.3 Decoupling Structure(s) 
     In one form the patient interface  3000 ,  6000 ,  9000  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 . 
     5.3.3.4 Connection Port 
     Connection port  3600  allows for connection to the air circuit  4170 . 
     5.3.3.5 Forehead Support 
     In one form, the patient interface includes a forehead support  3700 . 
     5.3.3.6 Anti-Asphyxia Valve 
     In one form, the patient interface includes an anti-asphyxia valve. 
     5.3.3.7 Ports 
     In one form of the present technology, a patient interface  3000 ,  6000 ,  9000  includes one or more ports that allow access to the volume within the cavity  3101 . 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 cavity  3101 , such as the pressure. 
     5.3.4 Full Face Cushion 
     5.3.4.1 First Illustrated Example 
     Referring to  FIGS.  39 - 50   , patient interface  14000  includes cushion assembly  14105  having a seal-forming structure  14100  that is configured to seal separately around the patient&#39;s nares and mouth, i.e., an oro-nasal cushion assembly or ultra-compact full face mask. The cushion assembly  14105  is at least partially formed by a plenum chamber  14200  and a seal-forming structure  14100  that is attached to the plenum chamber in accordance with an example of the present technology. 
     Referring to  FIGS.  51 - 56   , a cushion assembly  31105  is shown. Cushion assembly  31105  is similar to cushion assembly  14105  and has a seal-forming structure  31100  that is configured to seal separately around the patient&#39;s nares and mouth, i.e., an oro-nasal cushion assembly or ultra-compact full face mask. The cushion assembly  31105  is at least partially formed by a plenum chamber  31200  and a seal-forming structure  31100  that is attached to the plenum chamber in accordance with an example of the present technology. 
     The cushion assembly  31105  includes nasal portion  31101 , nasal portion holes  31103 , oral portion  31102 , oral portion hole  31104 , cavity  31001 , support structure  31120 , sealing portion  31130 , and vent  31400  which are similar to the features described in  FIG.  39 - 50    and are not discussed separately. A pair of plenum chamber holes are configured to receive a flow of air. 
     As described earlier,  FIGS.  54 - 56    show grip pads  31150  on the surface of the textile membrane. 
     Plenum Chamber 
     The plenum chamber  14200  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  14200  is positioned in close proximity to an adjacent surface of the face. Actual contact with the face is provided by the seal-forming structure  14100 . The seal-forming structure  14100  may extend in use about the entire perimeter of the plenum chamber  14200 . 
     In certain forms of the present technology, the plenum chamber  14200  is constructed from a relatively rigid material (e.g., polycarbonate) as compared to the seal-forming structure. In another example, the plenum chamber  14200  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, and help improve compliance with therapy. The use of a transparent material can aid a clinician to observe how the patient interface is located and functioning. 
     In certain forms of the present technology, the plenum chamber  14200  is constructed from a translucent material. The use of a translucent material can reduce the obtrusiveness of the patient interface, and help improve compliance with therapy. 
     The plenum chamber  14200  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  14800 , which are described in greater detail below, and the cavity  14001 . 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  14200  may be constructed of a sufficiently rigid material to provide audible and/or tactile feedback to the patient when the conduit connectors  14800  are connected to or removed from the plenum chamber  14200 . 
     The seal-forming structure  14100  may be sealingly connected to the plenum chamber  14200 . The connection may be permanent or the seal-forming structure  14100  may be removable from the plenum chamber  14200 . The seal-forming structure  14100  may be overmoulded to the plenum chamber  14200 . The seal-forming structure  14100  and the plenum chamber  14200  may be joined by a mechanical connection in which no chemical bond is formed between the plenum chamber  14200  and the seal-forming structure  14100 . 
     Seal-Forming Structure 
     Referring to  FIGS.  39 - 50   , the seal-forming structure  14100  may include a nasal portion  14101  having a pair of nasal portion holes  14103  to seal with the patient&#39;s nares. The depicted examples provide two separate holes  14103  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  14106  positioned between the naris openings  14103 . In an alternative example, a single hole may be used to provide the flow of air to both of the patient&#39;s nares. 
     The seal-forming structure  14100  may include an oral portion  14102  having an oral portion hole  14104  to seal with the patient&#39;s mouth. 
     The seal-forming structure  14100  may at least partly form a cavity  14001  that is pressurized by the flow of air. The plenum chamber  14200  may be joined to the seal-forming structure  14100  to further form the cavity  14001 . 
     The seal-forming structure  14100  may include a support structure  14120  that provides support to a sealing portion  14130  (e.g., a textile membrane). The sealing portion is configured to sealingly engage the patient&#39;s face. Also, depending on the size and contours of the patient&#39;s nose, the support structure may also sealingly engage the patient&#39;s face. 
     The support structure  14120  may comprise a wall structure having at least two regions of different thicknesses (e.g., portions of the support structure adjacent to or connecting to the plenum chamber  14200  may be thicker than portions of the support structure adjacent to or connecting to the sealing portion  14130  so as to provide structural stability at the connection with the plenum chamber  14200  and flexibility at the interface with the patient).  FIG.  84    illustrates an example where portions (d1) of the support structure may be thicker than portions (d2) of the support structure. For example, portions (d1) may be adjacent to or connection to the plenum chamber and portions (d2) may be adjacent to or connecting to the sealing portion so as to provide structural stability at the connection with the plenum chamber 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 and/or regions of the oral portion of the seal-forming structure (and e.g., may connect directly to the textile membrane), to ensure adequate sealing in the subalare region and/or mouth region of the patient&#39;s face. 
     As described above, the seal-forming structure  14100  may be sealingly connected to the plenum chamber  14200 . The support structure  14120  may be less rigid than the plenum chamber  14200  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  14130  may be less rigid than the support structure  14120  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 support structure  14120  may have an aperture formed therein providing an inner edge of the support structure along which the sealing portion  14130  (e.g., an outer perimeter of the sealing portion) may be attached to the support structure such that the sealing portion extends radially inwardly of the seal-forming structure beyond or to a further extent than the support structure, as shown for example in  FIGS.  43 - 46   . For example, the sealing portion may be molded around the inner edge of the support structure or connected to the support structure in other suitable ways, as will be described later. 
     In the example of  FIG.  49   , the support structure  14120  may extend into the cavity  14001  forming an underlying cushion  14121  to provide support to the sealing portion  14130 . The underlying cushion  14121  and the sealing portion  14130  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.  49   , the underlying cushion is constructed of a foam material (e.g., polyurethane foam). In an alternative example, the underlying cushion  14122  may be constructed of silicone, as shown in  FIG.  50   . However, it will be recognized that the underlying cushion may be constructed from other suitable materials (e.g., textile). 
     It should also be appreciated that one or more aspects of the present technology may be combinable with one or more aspects of: U.S. Provisional Application No. 62/609,909, filed Dec. 22, 2017 or WO 2019/119058, filed Dec. 21, 2018, both entitled “Conduit Headgear Connector for Patient Interface,” Each of which is hereby incorporated herein by reference in its entirety For instance, the conduits and positioning and stabilizing structures of the present technology may be identical to the conduits and positioning and stabilizing structures in any of the embodiments of the &#39;909 or &#39;058 application. Additionally, the cushion assemblies and seal-forming structures disclosed herein may replace any of the cushion assemblies (seal-forming structures and plenum chamber) and seal-forming structures in any of the patient interfaces disclosed in the &#39;909 or &#39;058 application. 
     5.3.4.1.1 Positioning and Stabilising Structure 
     The seal-forming structure  14100  of the patient interface  14000  of the present technology may be held in sealing position in use by the positioning and stabilising structure  14300 . 
     In one form the positioning and stabilising structure  14300  provides a retention force at least sufficient to overcome the effect of the positive pressure in the cavity  14001  to lift off the face. 
     In one form the positioning and stabilising structure  14300  provides a retention force to overcome the effect of the gravitational force on the patient interface  14000 . 
     In one form the positioning and stabilising structure  14300  provides a retention force as a safety margin to overcome the potential effect of disrupting forces on the patient interface  14000 , such as from tube drag, or accidental interference with the patient interface. 
     In one form of the present technology, a positioning and stabilising structure  14300  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  14300  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  14300  comprises at least one strap having a rectangular cross-section. In one example the positioning and stabilising structure  14300  comprises at least one flat strap. 
     In one form of the present technology, a positioning and stabilising structure  14300  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  14300  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  14300  is provided with a decoupling portion located between an anterior portion of the positioning and stabilising structure  14300 , and a posterior portion of the positioning and stabilising structure  14300 . 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  14300  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  14300  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  14302  ( FIG.  41   )), 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  14303  ( FIG.  41   )), 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  14304  ( FIG.  39   )) 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  14300  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  14300  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  14300 , 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  14300  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  14300  may include a clip  14301  to secure respective ties, e.g., to the conduit connectors  14800  as shown in  FIG.  39   . The clip  14301  and the conduit connector  14800  may each include a magnet arranged with opposing polarities to facilitate a connection therebetween. 
     5.3.4.1.2 Vent 
     In one form, the patient interface  14000  includes a vent  14400  constructed and arranged to allow for the washout of exhaled gases, e.g. carbon dioxide, as shown in  FIG.  39   . 
     In certain forms, the vent  14400  is configured to allow a continuous vent flow from an interior of the plenum chamber  14200  to ambient whilst the pressure within the plenum chamber is positive with respect to ambient. The vent  14400  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  14400  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  3400  may be located in the plenum chamber  14200 , as shown in  FIG.  47   . Alternatively, the vent  14400  is located in a decoupling structure, e.g., a swivel. 
       FIG.  39    shows an example of a vent  14400  provided on the connection port  14600  (e.g., a swivel elbow). Variations of these examples may exclude a vent  14400  from the connection port  14600 . 
     The conduit connectors  14800 , which are described in greater detail below, may also include vent features. 
     5.3.4.1.3 Decoupling Structure(s) 
     In one form, the patient interface  14000  includes at least one decoupling structure, for example, a swivel or a ball and socket. 
     5.3.4.1.4 Connection Port 
     Connection port  14600  allows for connection to the air circuit  4170 . The connection port  14600  according to an example of the present technology may be connected to the connection port housing  14903 . The connection port  14600  may be swivelable relative to the connection port housing  14903  and the connection to the air circuit  4170  may also be swivelable. 
     The connection port  14600  and the connection port housing  14903  may be positioned superior to the patient&#39;s head in use. 
     5.3.4.1.5 Forehead Support 
     Examples of the patient interface of the present technology shown in  FIGS.  39 - 50    do not include a forehead support. Variations of the patient interface of the present technology may include a forehead support. 
     5.3.4.1.6 Conduits 
     The patient interface  14000  according to examples of the present technology may include conduits  14900  to provide the flow of pressurized air from the connection port  14600  to the cavity  14001  in the plenum chamber  14200 . The conduits  14900  may be joined superior to the patient&#39;s head at the connection port housing  14903  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  14900  may be connected to the cushion assembly  14105  (e.g., plenum chamber  14200 ) via conduit connectors  14800 , as described below, to provide the flow of pressurized air to the cavity  14001 . 
     The conduits  14900  may also stabilize and position the seal-forming structure  14100  on the patient&#39;s face. Thus, the conduits  14900  may function similarly to the ties of the positioning and stabilising structure  14300 . Accordingly, the mechanical connection of the conduits  14900  to the conduit connectors  14800  may be sufficient for tension forces in the conduits  3900  to be transmitted to the seal-forming structure  14100  through the conduit connectors  14800 . 
     The conduits  14900  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  14900  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  14900  may also be provided with sleeves  14901  to cushion the patient&#39;s face against the conduits  14900 . The sleeves  14901  may be removable. The sleeves  14901  may be made from a breathable material. 
     The conduits  14900  may also include tie connectors  14902  to facilitate connection with ties of the positioning and stabilising structure  14300 . 
     5.3.4.1.7 Conduit Connectors 
     The patient interface  14000 , according to examples of the present technology, may include conduit connectors  14800  to connect the conduits  14900  to the cushion assembly  14105  to provide the flow of pressurized air to the cavity  14001 . The conduit connectors  14800  may each be formed with a conduit connector housing  14801 . The conduit connectors  14800  may provide other functions, as described below, such as venting of the plenum chamber  14200 , connection to the positioning and stabilising structure  14300 , and asphyxia prevention by inclusion of an anti-asphyxia valve  14850 . 
       FIG.  43 - 50    show several views of the conduit connectors  14800  of the patient interface  14000 , according to examples of the present technology. 
     In  FIGS.  39 - 50   , the conduit connectors  14800  are shown attached to the plenum chamber  14200  at the plenum chamber holes (not shown). As can be seen, there is one conduit connector  14800  on each lateral side of the cushion assembly  14105 , and each conduit connector  14800  is connected to a plenum chamber hole on each corresponding lateral side of the cushion assembly  14105 . The conduit connectors  14800  may each include a conduit connector attachment structure to connect each of the conduit connectors  14800  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  14800  and the material of the plenum chamber  14200  may each be selected to facilitate the desired connection features. For example, the material of the conduit connectors  14800  and the material of the plenum chamber  14200  may each be relatively rigid to permit the audible and/or tactile feedback associated with a snap-fit. The material of the conduit connectors  14800  and the material of the plenum chamber  14200  may be different in at least one aspect or the materials may be the same. The conduit connectors  14800  may also be permanently connected to the plenum chamber at the plenum chamber holes. For example, the conduit connectors  14800  may be ultrasonically welded to the plenum chamber  14200 . The connection between the conduit connectors  14800  and the plenum chamber  14200 , whether removable or permanent, may also be designed to be sufficiently strong such that tension from the conduits  14900  can be transferred to the plenum chamber  14200  without disrupting the connection because, as explained above, the conduit connectors  14800  may facilitate positioning and stabilising of the seal-forming structure  14100  on the patient&#39;s head. 
     The conduit connectors  14800  may also be attached to lateral sides of the plenum chamber  14200  to improve aesthetics of the patient interface  14000 . As explained above, the plenum chamber  14200  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  14800  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  14000 . This contrasts with alternative designs where an elbow and air circuit may be joined to the center of the plenum chamber  14200 , thereby obstructing the view of the patient&#39;s face. 
     The conduit connectors  14800  may also each include a conduit connection end  14802  that connects to a respective conduit  14900 . The connection between the conduits  14900  and the conduit connectors  14800  at the conduit connection ends  14802  may be removable or permanent. A conduit connector inlet hole  14803  may be formed in the conduit connector housing  14801  at the conduit connection end  14802  to receive the flow of pressurized air. The conduit connectors  14800  may include structure, e.g., an undercut, to facilitate a removable, snap-fit connection with corresponding conduits  14900 , and each conduit  14900  may include a relatively rigid structure at the end that connects to the conduit connectors  14800  to facilitate such a connection. The conduit connectors  14800  may also be joined to the conduits  14900  with a friction fit. Again, as explained above, the conduits  14900  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  14900  and the conduit connectors  14800  at the conduit connection ends  14802  may be sufficiently secure to permit tension forces from the conduits  14900  to be transmitted to the conduit connectors  14800  without disrupting the connection between the conduits  14900  and the conduit connectors  14800  at the conduit connection ends  14802 . 
     The conduit connectors  14800  may also provide a venting function for the patient interface  14000 . The conduit connector housing  14801  may include a vent inlet that is in pneumatic communication with the cavity  14001  when the patient interface  14000  is assembled. The conduit connector housing  14801  may also include at least one conduit connector vent hole  14831 . As can be seen in the depicted examples, each conduit connector housing  14801  includes a plurality of conduit connector vent holes  14831 . This ensures adequate mixing of newly introduced air and air already present in the plenum chamber  14200 , which can enhance carbon dioxide washout and increase the amount of fresh air provided to the patient for respiration. 
     As shown in  FIG.  39 - 41   , the conduit connectors  3800  may also provide a connection to ties of the positioning and stabilising structure  3300 . The inferior ties may be joined to the conduit connectors  3800  with clips  14301 . The clips  14301  and the conduit connectors  14800  may include magnets with opposing polarities to facilitate the connection. The connection between the ties of the positioning and stabilising structure  14300  and the conduit connectors  14800  may be releasable. The tension from the inferior ties of the positioning and stabilising structure  14300  may urge inferior portions of the seal-forming structure  14100  into sealing engagement with the patient&#39;s face, e.g., around the mouth. Alternatively, structure to connect to the clips  14301  may be formed directly on the conduit connector housing  14801 . 
     5.3.4.1.8 Anti-Asphyxia Valve 
     In one form, the patient interface  14000  includes an anti-asphyxia valve. As best shown in  FIGS.  47  and  48   , each of the conduit connectors  14800  may include an anti-asphyxia valve assembly  14850 . Accordingly, the patient interface  14000  may include two anti-asphyxia valve assemblies  14850 . Each of the anti-asphyxia valve assemblies  14850  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  14850  is occluded, e.g., by a pillow, the other of the anti-asphyxia valve assemblies  14850  can function to prevent the patient from being asphyxiated. 
     5.3.4.1.9 Ports 
     In one form of the present technology, a patient interface  14000  includes one or more ports that allow access to the volume within the plenum chamber  4200 . 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  14200 , such as the pressure. 
     5.3.4.2 Second Illustrated Example 
       FIGS.  57  to  66    show a patient interface  30000  according to another example of the present technology. Patient interface  30000  includes cushion assembly  30105  having a seal-forming structure  30100  that is configured to seal separately around the patient&#39;s nares and mouth, i.e., an oro-nasal cushion assembly or ultra-compact full face mask. The cushion assembly  30105  is at least partially formed by a plenum chamber (or shell)  30200  and a seal-forming structure  30100  that is attached to the plenum chamber in accordance with an example of the present technology. 
     The cushion assembly  30105  includes nasal portion  30101 , nasal portion holes  30103 , oral portion  30102 , oral portion hole  30104 , cavity  30001 , support structure  30120 , and sealing portion  30130  which are similar to the features described in  FIGS.  39 - 56    and are not discussed separately. An inlet port  30240  is formed in the plenum chamber and is configured to receive a flow of air for an air circuit. 
     5.3.4.2.1 Positioning and Stabilising Structure 
       FIGS.  57 - 66    show a patient interface  30000  according to one example of the present technology having a positioning and stabilising structure  30300  and a plenum chamber  30200  having a seal forming structure  30100 . The positioning and stabilising structure  30300  in this example comprises a frame  30350  and a plurality of headgear straps connected to the frame  30350 . 
     The plenum chamber  30200  of the patient interface  30000  is connected to the frame  30350 . The plenum chamber  30200  may connect to the frame  30350  via a snap fit connection. In other examples, the plenum chamber may form a different type of removable connection to the frame, snap fit, removable press fit or otherwise, or may be permanently connected to the frame. 
     The positioning and stabilising structure  30300  may comprise a plurality of straps or strap portions connecting to the frame  30350  and passing around the patient&#39;s head in order to support the plenum chamber in sealing position against the patient&#39;s face. It will be understood that a single “strap” may be formed by multiple lengths of material(s) that have been cut or formed separately and then joined together at their ends to create a longer length or single “strap” may be a single length of material(s). 
     In the example illustrated in  FIGS.  57 - 66   , the positioning and stabilising structure  30300  comprises a pair of upper straps  30310 . Each upper strap is configured to pass between a respective eye and ear of the patient. Additionally, the positioning and stabilising structure comprises a pair of lower straps  30320  configured to lie over the patient&#39;s cheeks below the patient&#39;s cheekbones. In this example, the plenum chamber is held in position via a four-point connection to headgear straps via the frame  30350 . 
     The frame is shown in isolation in  FIGS.  63 - 64   . The frame comprises a frame inlet connection port  30354 . The frame inlet connection port  30354  may be configured to connect to a source of pressurised breathable gas, such as air. In one example, the frame inlet connection port  30354  may be configured to enable connection to a swivel elbow assembly  30610  which provides a connection port  30600  for connection with an air circuit  4170 . The frame inlet connection port in this example comprises a connection rim  30355 . The connection rim  30355  may comprise a radially outwardly extending flange. The swivel elbow assembly  30610  may form a releasable snap-fit with the connection rim, creating a fluid connection between the swivel elbow assembly and the frame. The opposite side of the frame inlet connection port  30354  is configured to fluidly connect to the plenum chamber. The frame  30350  therefore enables a fluid connection between the swivel elbow assembly  30610  and the interior of the plenum chamber  30200 . 
     The frame  30350  also comprises a pair of opposed upper strap connection points  30315  to which the upper straps  30310  connect. In this example, each upper strap connection point comprises an aperture formed in the frame. Each upper strap  30310  is able to connect to a respective upper strap connection point  30315  by passing through the aperture, looping back onto itself and securing to itself. Each upper strap may secured to itself via hook and loop materials configured to releasably bind to each other upon contact. In alternative examples, each upper strap  30310  may pass through a respective aperture, loop back onto itself and be secured onto itself with a band, clip or the like. In further alternative examples, the upper straps may connect to the frame via side release buckle connections. 
     The frame  30350  also comprises a pair of opposed lower strap connection points  30325  to which the lower straps  30320  connect. In this example, each lower strap connection point comprises a magnet. Each lower strap comprises a lower strap clip  30326  comprising a magnet or material that is attracted to the magnet at the lower strap connection point  30325 . In this example, each lower strap clip  30326  comprises an aperture through which the end of a respective lower strap is able to pass and then loop back and be secured onto itself, for example with hook and loop material, a band, a clip or the like. In alternative examples, the lower straps may connect to the frame via side release buckle connections, onto hooks or via any other suitable connection. 
     In an example, the frame  30350  and upper strap connection points  30315  are structured and arranged to direct a force/tension provided by the upper straps  30310  into a partially superior and partially posterior force vector applied to the plenum chamber  30200 . The partially superior and partially posterior force vector urges, in particular, the nasal portion  30101  of the seal forming structure  3100  into sealing contact with the lower periphery of the patient&#39;s nose and the patient&#39;s upper lip. 
     The upper straps  30310  may each be selectively adjustable. For example, the effective length of each of the upper straps may be varied by changing how much of the upper strap is passed through the aperture at the respective upper strap connection point  30315  and looped back on itself. Passing more of the upper strap through the aperture effectively reduces the length of the upper strap, allowing the force vectors to be modified and the fit of the patient interface to be adjusted. 
     In an example, the frame  30350  and the lower strap connection points  30325  are structured and arranged to direct a force/tension provided by the lower straps  30320  into a partially posterior and partially inferior force vector applied to the plenum chamber. The partially posterior and partially inferior force vector urges, in particular, the oral portion  30102  into sealing contact with the patient&#39;s face around the periphery of the patient&#39;s mouth. The partially inferior force applied to the frame by the lower straps may balances the partially superior force applied by the upper straps along with any inferiorly directed force that the patient&#39;s nose may apply onto the seal forming structure. 
     The lower straps  30320  may each by selectively adjustable. For example, the effective length of each of the lower straps may be varied by changing how much of each lower strap is passed through the aperture in the respective lower strap clip  30326  and looped back on itself. Passing more of each lower strap through the aperture effectively reduces the length of the lower strap, allowing the force vectors to be modified and the fit of the patient interface to be adjusted. 
     The positioning and stabilising structure  30300  may also comprise one or more of a top crown strap  30330 , a pair of lateral crown straps  30332  and a neck strap  30334 . In the example illustrated in  FIGS.  57 - 66   , the upper straps  30310  and lower straps  30320  are connected to ends of a top crown strap  30330 . The top crown strap is configured to pass around the patient&#39;s head and lie against superiorly and posteriorly facing surfaces. The top crown strap  30330  may be configured to overlie the parietal bone of the patient&#39;s skull. Each end of the top crown strap connects to a respective one of the upper straps  30310  and also to a respective one of a pair of lateral crown straps  30332 . Each one of the lateral crown straps connects between the upper strap and the lower strap on a respective side of the patient&#39;s head. The inferior ends of the lateral crown straps  30332  are connected to each other by a neck strap  30334 . The neck strap may be configured to pass across the sagittal plane and lie against inferior and/or posterior facing surfaces of the patient&#39;s head or lie against the back of the patient&#39;s neck. The neck strap may overlie, or lie inferior to, the occipital bone of the patient&#39;s skull. 
     The length of the top crown strap  30330  may be selectively adjustable. The top crown strap  30330  is formed by two strap portions which are connected by a link having a pair of apertures. Each of the two strap portions forming the top crown strap is able to pass through a respective one of the apertures then loop back and secure to itself, for example via hook and loop material, a further clip, a band or the like. The amount of each top strap portion that passes through the link can be varied to adjust the length of the top crown strap  30330  and in turn adjust the fit of the positioning and stabilising structure. 
     Once all the headgear straps have been adjusted and the desired fit of the patient interface  30000  has been achieved, the magnetic clip connection provided by the lower strap clips  30326  enables the lower straps  30320  to be quickly disengaged from the lower strap connection points  30325  on the frame  30350 , allowing the patient interface  30000  to be removed from the patient without adjustment of straps. Similarly, when the patient dons the patient interface again, the lower strap clips can be quickly engaged at the lower strap connection points to fit the patient interface without the need to adjust straps. Further advantages and features of a positioning and stabilising structure comprising magnetic clips are described in WO 2014/110622, the entire contents of which are incorporated herein by reference. 
     In certain forms of the present technology, a system is provided comprising more than one positioning and stabilizing structure, 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 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. 
     Also, it should be appreciated that one or more aspects of the present technology may be combinable with one or more aspects of: PCT/AU2019/050278, filed Mar. 28, 2019 and entitled “Patient Interface,” the entire contents of which are hereby incorporated herein by reference in their entirety. 
     5.3.4.2.2 Vent 
     In one form, the patient interface  30000  includes a vent  30400  constructed and arranged to allow for the washout of exhaled gases, e.g. carbon dioxide. 
     In certain forms the vent  30400  is configured to allow a continuous vent flow from an interior of the plenum chamber  30200  to ambient whilst the pressure within the plenum chamber is positive with respect to ambient. The vent 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 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  30400  may be located in the plenum chamber. Alternatively, the vent is located in a decoupling structure, e.g., a swivel. 
     In the example illustrated in  FIGS.  57 - 66   , the patient interface  30000  comprises a vent  30400 . The vent in this example comprises passages within the frame and swivel elbow assembly through which air can flow from the interior of the plenum chamber to atmosphere. As shown in  FIG.  59   , air can flow into the swivel elbow assembly  30610  and then out to atmosphere through exterior holes of the swivel elbow assembly forming part of the vent  30400 . The swivel elbow assembly  30610  may be substantially as described in International Publication No. WO 2017/049357 A1, the entire contents of which are incorporated herein by reference. 
     5.3.4.2.3 Decoupling Structure(s) 
     In one form the patient interface  30000  includes at least one decoupling structure, for example, a swivel or a ball and socket. 
     5.3.4.2.4 Connection Port 
     Connection port  30600  allows for connection to the air circuit  4170 . 
     5.3.4.2.5 Forehead Support 
     In one form, the patient interface  30000  includes a forehead support  3700  such as that shown in  FIG.  3 A . In other examples, the patient interface may exclude a forehead support. Furthermore, the patient interface  30000  may be configured not to contact the patient&#39;s forehead at all. 
     5.3.4.2.6 Anti-Asphyxia Valve 
     In one form, the patient interface  30000  includes an anti-asphyxia valve. 
     5.3.4.2.7 Ports 
     In one form of the present technology, a patient interface  30000  includes one or more ports that allow access to the volume within the plenum chamber. 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  302000 , such as the pressure. 
     5.3.4.3 Third Illustrated Example 
       FIGS.  67  to  77    show a patient interface  16000  according to another example of the present technology. The patient interface includes a frame assembly  16100 , a cushion assembly  16175  including a seal-forming structure  16200 , an air delivery connector (e.g., elbow assembly  16600 ), and a positioning and stabilising structure (e.g., headgear  16800  including upper side straps  16802 , lower side straps  16804 , and crown strap  16806 ). In use, one form of the seal-forming structure  16200  is arranged to surround an entrance to the airways of the patient  1000  so as to facilitate the supply of air at positive pressure to the airways. In the example shown in  FIGS.  46 - 56   , the patient interface is a full-face/oro-nasal interface type including a seal-forming structure  16200  structured to form a seal around the patient&#39;s nose and mouth. However, aspects of the present technology may be adapted for use with other suitable interface types, e.g., nasal interface, nasal prongs, pillows, etc. 
     The seal-forming structure  16200  may also be commonly referred to as a cushion.  FIGS.  67  and  68    are exemplary views of the patient interface  16000  with arm covers  16750  for upper arms  16134  of the frame assembly  16100  attached, and  FIG.  69    is an exemplary view of the patient interface  16000  with the headgear  16800  and the arm covers  16750  removed. 
     In this example, the cushion assembly  16175  connects to the frame assembly  16100  (via a first retention feature on the frame assembly) independently of the elbow assembly  16600 , and the elbow assembly  16600  connects to the frame assembly  16100  (via a second retention feature on the frame assembly) independently of the cushion assembly  16175 . That is, the retention connections of the cushion assembly  16175  and the elbow assembly  16600  to the frame assembly  16100  are separate and distinct from one another and allow independent engagement/disengagement. 
     In the example of patient interface  16000 , a first seal for the air flow path is formed between the elbow assembly  16600  and the frame assembly  16100 , and a separate second seal is formed between the frame assembly  16100  and the cushion assembly  16175 . In this example, the frame assembly  16100  is provided in the air flow path. That is, the elbow assembly  16600  is structured to establish a hard-to-hard connection and dynamic seal with the frame assembly  16100 , and the cushion assembly  16175  is structured to establish a separate hard-to-hard connection and static seal with the frame assembly  16100 . 
     Also, in the example of patient interface  16000 , the frame assembly  16100  includes a lockout feature along the opening  16105  that is structured and arranged to prevent direct connection or insertion of the air circuit  4170 , e.g., air delivery tube. This arrangement requires use of the elbow assembly  16600  to interconnect the frame assembly  16100  and the air circuit  4170 , thereby ensuring that the elbow assembly  16600  (and its vent and anti-asphyxia valve (AAV)) are present in the system. 
     Frame Assembly 
     Still referring to  FIGS.  67 - 77   , the frame assembly  16100  includes a shroud or wall member  16110 , a pair (i.e., right and left) of upper headgear connector arms  16134  (each comprising two flexible portions  16140 ,  16145 ) extending from respective sides of an upper portion of the shroud  16110 , and a pair (i.e., right and left) of lower headgear connector arms  16154  extending from respective sides of a lower portion of the shroud  16110 . Each lower headgear connector arm  16154  comprises the magnetic connector  16155  (including encased magnet) structured to locate and connect to the headgear clip  16160  (including encased magnet) provided to the respective lower headgear strap  16804  of the headgear. 
     In the illustrated example, the opening  16105  of the shroud  16110  (e.g., constructed of a relatively hard plastic material such as polycarbonate) is bounded by an outer annular flange and an inner annular flange. 
     Cushion Assembly &amp; Elbow Assembly 
     Referring to  FIGS.  67 - 77   , the cushion assembly  16175  includes a main body, chassis, plenum chamber or shell  16180  that is connected or otherwise provided to the seal-forming structure or cushion  16200  (see  FIGS.  70  and  71   ). The shell  16180  may be permanently (e.g., co-molded, overmolded) or removably (e.g., mechanical connection) connected to the cushion  16200 . In an example, the cushion  16200  is constructed of a relatively flexible or pliable material and the shell  16180  is constructed of a relatively rigid material (e.g., polycarbonate). The shell  16180  and the cushion  16200  cooperate to form the cavity  16500  (e.g., see  FIGS.  70 ,  71  and  73   ). The shell  16180  includes an opening  16305  by which breathable gas is delivered to the cavity  16500 . The opening  16305  is bounded by an annular flange  16310  which is adapted to connect to the frame assembly  16100 . 
     The shell  6180  has multiple functions. For example, it at least partially forms the cavity for delivery of pressurised gases to the entrance of a patient&#39;s airways. The shell  6180  is a rigid structure that directs a force onto the seal-forming structure for sealing to a patients face. The force is provided by tension forces from tightening the headgear straps. These forces are translated from a pair of upper and lower headgear straps to the corresponding upper and lower arms. In an example, the upper and lower arms are provided with the frame assembly, which provides the headgear tension forces to the shell  16180 . 
     The shell  16180  of the cushion assembly  16175  is repeatedly engageable with and removably disengageable from the shroud  16110  of the frame assembly  16100  via a mechanical connection, e.g., snap-fit connection. The inner annular flange of the shroud  16110  extends through the opening  16305  of the shell  16180 , and the tabs or catches of the flange engage or interlock on a posterior side of the annular flange  16310  of the shell  16180  so as to releasably connect the frame assembly  16100  to the cushion assembly  16175 . Such connection maintains ease of use, provides a sealed hard to hard connection, minimizes rattling and rocking movement between components, and reduces impact on stability. Also, such connection stably holds the cushion assembly  16175  in position, while allowing the appropriate force vectors to be imparted onto the cushion assembly  16175  for seal. 
     In the example shown in  FIG.  67   , the elbow assembly  16600  includes a first end portion  16610  with pinch arms  16650  to releasably engage with the frame assembly  16100  (and form a swivel connection therewith) and a second end portion  16620  adapted to connect to the air circuit  4170 , e.g., via a swivel connector  16625 . The elbow assembly  16600  is structured to establish a hard-to-hard connection and seal with the frame assembly  16100 . 
     In this example, the first end portion  16610  includes inner and outer radial walls defining a radial channel leading to a plurality of vent holes  16700  to permit the exit of exhausted gases from the patient interface. 
     Also, it should be appreciated that one or more aspects of the present technology may be combinable with one or more aspects of: U.S. Application Publication No. 2018/0250486, filed Mar. 12, 2018 and entitled “Patient Interface,” the entire contents of which are hereby incorporated herein by reference in their entirety. For instance, the cushion assembly  16175  disclosed herein may replace the cushion assembly in any of the patient interface embodiments disclosed in the &#39;486 publication. Furthermore, the seal-forming structure  16200  disclosed herein made replace the seal-forming structure in any of the patient interface embodiments disclosed in the &#39;486 publication. 
     Seal-Forming Structure 
     As described above, the shell  16180  is sealingly connected or otherwise provided to the seal-forming structure or cushion  16200 , and the shell  16180  and the cushion  16200  cooperate to form the cavity  16500 . 
     The cushion  16200  may include a support structure  16220  that provides support to a sealing portion  16230  (e.g., a textile membrane). The sealing portion is configured to sealingly engage the patient&#39;s face. 
     The support structure  16220  may comprise a wall structure having at least two regions of different thickness (e.g., portions of the support structure adjacent to or connecting to the shell  16180  may be thicker than portions of the support structure adjacent to or connecting to the sealing portion  16230  so as to provide structural stability at the connection with the shell  16180  and flexibility at the interface with the patient).  FIG.  84    illustrates an example where portions (d1) of the support structure may be thicker than portions (d2) of the support structure. For example, portions (d!) may be adjacent to or connection to the plenum chamber and portions (d2) may be adjacent to or connecting to the sealing portion so as to provide structural stability at the connection with the frame and flexibility at the interface with the patient. Alternatively, the thicker lateral support regions  3122  may be located, for example, at the lower cheek region of the seal-forming structure (and e.g., may connect directly to the textile membrane), to ensure adequate sealing in the lower cheek region of the patient&#39;s face. 
     The support structure  16220  may be less rigid than the shell  16180  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  16230  may be less rigid than the support structure  16220  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 support structure  16220  may have an aperture formed therein providing an inner edge of the support structure along which the sealing portion  16230  (e.g., an outer perimeter of the sealing portion) may be attached to the support structure such that the sealing portion extends radially inwardly of the seal-forming structure beyond or to a further extent than the support structure, as shown for example in  FIGS.  71  and  73 - 77   . For example, the sealing portion may be molded around the inner edge of the support structure or connected to the support structure in other suitable ways, as will be described later. 
     The support structure  16220  may extend into the cavity  16500  forming an underlying cushion  16221  to provide support to the sealing portion  16230 , as shown in  FIGS.  73  and  77   . The underlying cushion  16221  and the sealing portion  16230  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. The underlying cushion may be constructed of the same materials as the support structure and may also be constructed of other suitable materials (e.g., textile). 
     5.3.4.3.1 Positioning and Stabilising Structure 
     The seal-forming structure of the patient interface of the present technology may be held in sealing position in use by the positioning and stabilising structure. 
     In one form of the present technology, a positioning and stabilising structure 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 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 comprises at least one strap having a rectangular cross-section. In one example the positioning and stabilising structure comprises at least one flat strap. 
     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 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 cushion into sealing contact with a portion of a patient&#39;s face. In an example the strap may be configured as a tie. 
     In certain forms of the present technology, a positioning and stabilising structure 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 stabilizing structure provides a retaining force configured to correspond to a particular size of head and/or shape of face. For example one form of positioning and stabilizing structure provides a retaining force suitable for a large sized head, but not a small sized head. In another example, a form of positioning and stabilizing structure provides a retaining force suitable for a small sized head, but not a large sized head. 
     5.3.4.3.2 Vent 
     In one form, the patient interface includes a vent constructed and arranged to allow for the washout of exhaled gases, e.g. carbon dioxide. 
     One form of vent 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 may be located in the plenum chamber or shell. Alternatively, the vent is located in a decoupling structure, e.g., a swivel. 
     5.3.4.3.3 Decoupling Structure(s) 
     In one form the patient interface includes at least one decoupling structure, for example, a swivel or a ball and socket. 
     5.3.4.3.4 Connection Port 
     Connection port allows for connection to the air circuit. 
     5.3.4.3.5 Forehead Support 
     In the illustrated example, the frame assembly  6100  is provided without a forehead support. 
     In another form, the patient interface may include a forehead support, e.g., the frame assembly may include a forehead support. 
     5.3.4.3.6 Anti-Asphyxia Valve 
     In one form, the patient interface includes an anti-asphyxia valve. 
     5.3.4.3.7 Ports 
     In one form of the present technology, a patient interface includes one or more ports that allow access to the volume within the cavity. 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 cavity, such as the pressure. 
     5.3.5 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 (e.g., textile membrane) may be maintained in sealing contact with the patient&#39;s face by 1) tension (e.g., a light tension) in the textile membrane and/or a resilient stretch characteristic (e.g., elasticity) of the material (e.g., the textile material, the air impermeable layer material and/or the composite material of the textile membrane) of the sealing portion; 2) a reactive stress of the support structure; 3) a pre-formed state of the textile membrane formed as a non-tensioned, yet substantially constant surface, without leak causing interruptions such as creases, folds, buckles or wrinkles in the textile membrane; and/or 4) air pressure within the cavity against an inside surface of the sealing portion. Each of these factors may contribute to the sealing portion being under constant tension such that the sealing portion complies to the anthropometric contours of the patient&#39;s face, thereby minimizing wrinkles or blow-out and maximizing the contact area of the sealing portion. 
     In some examples, the sealing portion 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 may be held taut and in tension by the support structure prior to and during use. The sealing portion may be molded or otherwise attached (e.g., adhered, glued) to the support structure so that the sealing portion is pre-tensioned (slightly stretched) so that there are no wrinkles in the material of the sealing portion. 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 may be shaped or have curvature imparted thereto, e.g., by thermoforming, so that the sealing portion holds its own shape. The support structure may also impart curvature to the sealing portion. 
     For example, as shown in  FIGS.  11 - 17  and  23 - 37    the sealing portion may have a concave curved profile from one lateral side (right) to an opposing lateral side (left) (e.g., positive curvature in a left-right direction) to cradle the patient&#39;s nose. 
     In some forms, as shown for example in  FIGS.  10 - 66   , the patient&#39;s nose is not intended to be received in the cavity formed by the plenum chamber and the seal-forming structure. Instead, unlike conventional masks, the patient&#39;s nose is intended to press against the textile membrane which in turn accommodates the contours of the patient&#39;s face to comfortably form a reliable seal with the patient&#39;s airways. In the way, the textile membrane may stretch to accommodate the patient&#39;s face. The bridge portion  3104 ,  1406  extending between the naris openings may assist maintaining the textile membrane in a taut manner prior to and/or during use. The bridge portion may also function to help provide, by eliminating a central opening in the textile membrane, a sealing portion that presses against the patient&#39;s nose rather than receives the patient&#39;s nose in the cavity. This 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 rather than the more rigid materials of conventional masks or conventional sealing arrangements where the sealing portion has a smaller contact area around a perimeter of the nose and/or mouth. 
     The sealing portion may be constructed from a single or a plurality of layers of material (e.g., textile material). The textile membrane (and/or the textile material of the textile membrane) may exhibit a low spring constant (i.e., highly compliant) in both warp and weft. Unlike conventional masks (e.g., silicone sealing membrane), where a fixed cushion may cause a patient&#39;s skin to distort to form an effective seal, the textile membrane may have a material spring constant and spring length (i.e., the amount of material available to stretch) such that the textile membrane is more compliant than the patient&#39;s skin so as to more readily conform to the patient&#39;s facial features. This may improve comfort of the mask and reduce formation of localized pressure “hot spots.” 
     Compared to conventional silicone membranes and compression foam seals, the sealing portion of the present technology has a more flexible structural stiffness and therefore has a dynamic spring back characteristic that enables the sealing portion 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 to be more comfortable and create less facial marks during use. 
     The textile membrane may exhibit variable tension forces across the material (e.g., less tension forces proximal to holes or in wider stretches of material). In some forms, the surface of the material of the sealing portion 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 may also comprise at least one layer that exhibits substantially air-impermeable characteristics, while maintaining the resilient stretch characteristics necessary for comfort and minimal pressure points. That is, a membrane layer or laminate film layer (e.g., a polymer such as silicone, polyurethane, thermoplastic polyurethane (TPU), polyester, nylon, etc.) may be applied to the textile material to provide a substantially air-tight material. In an alternative example, the fibers of a textile may be tightly weaved to create a substantially air impermeable material. 
     In some forms, the textile material of the sealing portion may have a thickness in the range of 0.275 or less (e.g., 0.275 to 0.075 mm, 0.275 to 0.175 mm, 0.25 mm or less, 0.225 mm or less, 0.225 to 0.09 mm, 0.225 to 0.095 mm, 0.225 mm, or 0.25 mm). The membrane layer may have a thickness in the range of 0.03 to 0.01 mm (e.g., 0.015, 0.02 mm, or 0.025 mm). The textile material of the sealing portion with the membrane layer may have an overall composite material thickness in the range of 0.305 mm or less (e.g., 0.305 to 0.085 mm, 0.305 to 0.185 mm, 0.28 mm or less, 0.255 mm or less, 0.255 to 0.10 mm, 0.255 to 0.105 mm, 0.25 mm, or 0.275 mm). In an example, a textile composite including a microfiber textile and a polyurethane film layer may have these dimensions. 
     In another example, the textile material of the sealing portion may have a thickness in the range of 0.15 mm to 0.5 mm (e.g., 0.2 mm to 0.4 mm, or 0.3 mm to 0.4 mm, or 0.25 mm, or 0.3 mm, or 0.4 mm). The membrane layer may have a thickness in the range of 0.03 mm to 0.125 mm (e.g., 0.05 mm to 0.1 mm, or 0.075 mm to 0.1 mm, or 0.05 mm to 0.075 mm, or 0.05 mm, or 0.075 mm, or 0.1 mm). The textile material of the sealing portion with the membrane layer may have an overall composite material thickness in the range of 0.18 mm to 0.625 mm (e.g., 0.25 mm to 0.6 mm, or 0.25 mm to 0.5 mm, or 0.3 mm to 0.5 mm, or 0.35 mm to 0.45 mm, or 0.3 mm, or 0.35 mm, or 0.4 mm, or 0.45 mm, or 0.5 mm). In an example, a textile composite including a nylon or nylon and polyester mix textile and a silicone film layer may have these dimensions. 
     Tensile forces may also be transferred to the sealing portion as a result of the stiffness and resilient properties of the support structure. The support structure may be formed from a variety of materials, including silicone, foam (e.g., polyurethane foam), polyurethane solid material, thermoplastic elastomers (TPE) (e.g., thermoplastic polyurethane (TPU)), and suitable plastic materials. The support structure may be configured so as to create a number of different cushion configurations, including a single air assisted sealing portion (e.g., textile membrane) and a sealing portion with underlying cushion support layer(s) such as a double air assisted sealing portion (e.g., dual textile membranes), a sealing portion with compression support (e.g., open cell foam, polyurethane foam, gel), a sealing portion with TPU, TPE or silicone support, or a double air assisted sealing portion with additional support (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). 
     The underlying cushion layer(s) may assist in optimizing the sealing portion contact surface area with the patient&#39;s face. Further, in examples where the sealing portion 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. 
     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.  81   . 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. 
     In some examples, the support structure may comprise a biasing portion that utilizes the internal air pressure to dynamically support the support structure and sealing portion. This may advantageously provide further support of the sealing portion when under dynamic loads (e.g., tube drag). 
     The air pressure within the cavity and acting against the inside surface of the sealing portion may also ensure that a surface of the textile membrane without wrinkles, creases, buckles or folds (e.g., by creating tension in the sealing portion) in presented to the patient&#39;s face such that the sealing portion may substantially fill depressed contours of a patient&#39;s face (e.g., around the sides of the nose). This may enable the compliant sealing portion to form a larger seal contact area on the patient&#39;s face. The tension in the sealing portion created by the air pressure within the cavity may also be advantageous in providing a continuous seal even when the mask is partially displaced with an optimal positioning on the patient&#39;s face, as the sealing portion may partially inflate (i.e., a “hovercraft effect”) due to the counter-force from the internal air pressure. 
     In examples where the textile membrane is not under constant tension (and e.g., also non-elastic), the sealing portion may still be maintained in sealing contact with the patient&#39;s face by the air pressure within the cavity and form an improved air assisted seal with the patient&#39;s face that conforms dynamically to alterations/movements (i.e., “hovercraft effect”) due to the sealing portion being thinner and having a lower structural stiffness than the support structure. 
     The sealing portion may be integrated with the support structure by molding or otherwise attaching the sealing portion to the inner edge of the support structure. Thus, for example, an outer perimeter of the sealing portion may be attached to the inner edge of the support structure such that the sealing portion extends radially inwardly of the seal-forming structure beyond or to a further extent than the support structure. The inner edge of the support structure may be curved such that the sealing portion may be slightly angled inwardly toward the mask interior. By attaching the sealing portion along the inner edge of the support structure, the sealing portion does not need to be folded or cut to blend around the corners of the support structure. This may advantageously reduce the occurrence of protruding folds or wrinkles in the sealing portion, which may cause leakage, thereby improving the performance of the seal. 
     As described earlier, the seal-forming structure may be removably connected or fixedly attached to the plenum chamber. In some forms, the sealing portion may have a removable or modular structure. For example, the sealing portion may be attached to a supporting frame structure along its perimeter. The supporting frame may be removably attached as a module to the support structure. The sealing portion may be attached to the supporting frame so as to reduce the occurrence of protruding folds or wrinkles in the textile surface. The modular arrangement may also substantially simplify the manufacturing of the sealing portion (e.g., textile sealing portion) as all the complex bonding can be done in a simple unstressed state. While the sealing portion may be treated to have substantially self-cleaning properties, the use of a modular sealing portion may also provide a cheaper and more hygienic alternative. 
     The supporting frame may be pre-formed to have a flat or three-dimensional shape such as an arc so as to impart a curved shape to the sealing portion. The supporting frame may form an air-tight seal with the support structure. In some examples, the supporting frame may engage the support structure by connectors (e.g., male/female location pins/holes, tongue and groove). 
     The sealing portion may have underlying cushion support layer(s) (e.g., second, third or more cushion layers) incorporated therein. 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 some examples, the support layers may be supported by a rigid structure such as plastic, e.g., polypropylene (PP), polycarbonate (PC), polyamide (PA), or polyethylene terephthalate (PET). 
     In some examples, 3D printing of the sealing portion, support layers and/or support structure as a “skeleton” may reduce the thickness of the structure and thus the weight of the mask. Also, different layers of the mask could be printed with different rigidity, hardness, or thickness. For example, “skeleton” sections may be formed using silicone, foam (e.g., polyurethane foam), polyurethane (e.g., polyurethane solid material), or any suitable plastic material. In some examples, a biasing portion may be formed that may provide dynamic support in use. 
     5.3.5.1 Textile Membrane 
     In accordance with an example of the disclosed technology, the sealing-forming structure may include a textile membrane comprising a textile material. 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. The resulting textile sealing portion (or textile membrane) may be attached to the support structure (e.g., silicone, TPE), for example, by overmolding or injection molding. In another example, the textile sealing portion may be thermo-welded at its edges (outer perimeter) onto the support structure material (e.g., silicone, TPE). 
     A textile is a material including at least one natural or artificial fiber (e.g., yarn or thread). The fiber may be a filament (mono or poly), a strand, a thread or twine. The fiber(s) 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. Textiles may be formed by various techniques, such as weaving, knitting, crocheting, knotting, tatting, bonding, felting, tufting, or braiding, and may include, for example, woven and nonwoven materials, e.g., by intertwining or interlacing one or more of the fibers. 
     In an example, the textile material is a knitted 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. 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.  113    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.  114   .  FIG.  115    illustrates a basic closed loop warp knit  90  in which the wales and courses running parallel to one another.  FIG.  116    illustrates a weft knit  100  in which the wales  70  run perpendicular to the course  80 . 
     5.3.5.1.1 Manufacturing 
     In an example, an overmolding process may be used to construct a seal-forming structure having a, e.g., flexible, support structure (e.g., silicone) attached to a textile membrane. 
     As shown in  FIG.  117   , in step  10 , an airtight textile composite may be formed by combining a textile material with an impermeable material. A heat process may be used to attach the impermeable layer to the textile material, as shown in  FIG.  78    for example. The textile composite may have a flat shape (e.g., sheet-shaped). 
     In step  12 , the textile composite may be cut to a desired shape according to a particular cushion assembly to be used. 
     In step  14 , the support structure (e.g., silicone) may be overmolded onto the textile composite to form a seal-forming structure with a textile membrane. The textile composite may be held in place by a vacuum so as to have a non-flat predefined shape during the overmolding process. That is, the flat textile composite may be overmolded with the support structure so as to impart curvature to the textile composite thereby forming a textile membrane that may have curvature without wrinkles, folds, creases and/or buckles being formed in the textile membrane. As can be seen in  FIG.  33 - 1   , the textile membrane may extend along the curve  35  from the anterior side of the seal-forming structure to the posterior side of the seal-forming structure. In an example, as shown in  FIG.  33 - 1   , the support structure and textile membrane may both have a radius of curvature (e.g., the same or similar radius of curvature) along the curve  35 . The textile membrane may have a predefined curvature imparted thereto such that a portion of the textile membrane not directly supported by the support structure extends along the curve  35  ( FIGS.  33 - 2  to  33 - 4   ). As discussed earlier, the textile membrane may also have, for example, curvature in the way of dome and saddle shapes in other regions of the textile membrane. The textile membrane may have a concave curved profile from one lateral side (right) to an opposing lateral side (left) (e.g., positive curvature in a left-right direction) that may be imparted during the overmolding process and maintained by connection to the support structure (see  FIGS.  11 - 17 ,  23 - 27 , and  33 - 37    for example). In another example, the textile membrane may have negative curvature in an inferior-superior direction that may be imparted during the overmolding process and maintained by connection to the support structure (see  FIGS.  18 - 22    for example). 
     The support structure may be molded onto the textile composite such that the outer surface of the seal-forming structure is smooth and seamless in the transition from the support structure to the textile membrane (see  FIG.  33 - 4   ). The support structure may bond to the impermeable material of the textile membrane. While the outer surface of the seal-forming structure may be smooth and seamless, a step may be present on the inner surface of the seal-forming structure where the thickness of the support structure is different (e.g., greater) than the thickness of the impermeable layer. 
     The overmolding process forms the seal-forming structure without creating any wrinkles, folds, creases and/or buckles in the textile membrane while also imparting curvature to the textile membrane. 
     5.3.5.1.2 Textile Membrane Examples 
     Below are example properties and structural arrangements of the textile composite used as the material for the textile membrane. 
     5.3.5.1.2.1 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. 
     5.3.5.1.2.2 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. 
     5.3.5.1.2.3 Textile Material Thickness 
     In an example, the textile material of the sealing portion may have a thickness in the range of 0.15 mm to 0.5 mm (e.g., 0.2 mm to 0.4 mm, or 0.3 mm to 0.4 mm, or 0.25 mm, or 0.3 mm, or 0.4 mm). Such a thickness may be suitable for a nylon material or nylon and polyester mix material. 
     In another example, the textile material of the sealing portion may have a thickness in the range of 0.275 or less (e.g., 0.275 to 0.075 mm, 0.275 to 0.175 mm, 0.25 mm or less, 0.225 mm or less, 0.225 to 0.09 mm, 0.225 to 0.095 mm, 0.225 mm, or 0.25 mm). Such a thickness may be suitable for a microfiber textile material or a polyurethane textile material. 
     5.3.5.1.2.4 Air Impermeable Layer Thickness 
     In examples where silicone is used as the membrane/film layer, the silicone may have a thickness in the range of 0.03 mm to 0.125 mm (e.g., 0.05 mm, 0.05 mm to 0.1 mm, or 0.05 mm to 0.075 mm, or 0.075 mm to 0.1 mm, or 0.1 mm). A thinner silicone layer (e.g., 0.05 mm) may be more desirable as it provides a lighter weight product and also provides more stretch than thicker silicone layers (e.g., 0.1 mm). Thicker silicone layers (e.g., 0.1 mm), however, are more durable than thinner layers (e.g., 0.05 mm). 
     In another example, where a polyurethane film is used as the membrane layer, the polyurethane film may have a thickness in the range of 0.03 to 0.01 mm (e.g., 0.015, 0.02 mm, or 0.025 mm). 
     5.3.5.1.2.5 Textile Composite Total Thickness 
     In examples where a textile material is coated with a silicone membrane/film layer, the overall composite material may have a thickness in the range of 0.18 mm to 0.625 mm (e.g., 0.25 mm to 0.6 mm, or 0.25 mm to 0.5 mm, or 0.3 mm to 0.5 mm, or 0.35 mm to 0.45 mm, or 0.3 mm, or 0.35 mm, or 0.4 mm, or 0.45 mm, or 0.5 mm). 
     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. 
     In examples where a textile material is coated with polyurethane film, the overall composite material may have a thickness in the range of 0.305 mm or less (e.g., 0.305 to 0.085 mm, 0.305 to 0.185 mm, 0.28 mm or less, 0.255 mm or less, 0.255 to 0.10 mm, 0.255 to 0.105 mm, 0.25 mm, or 0.275 mm). 
     5.3.5.1.2.6 Knit Structure 
     The textile material of the textile membrane may have a weft knit structure or, alternatively, a warp knit structure, for example. 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. 
     5.3.5.1.2.7 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 another example, the fabric may be an interlock knit. 
     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. 
     5.3.5.1.2.8 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. 
     5.3.5.1.2.9 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). It is noted that machine gauge may also be indicated by the letter “E”, such as E35 to E70. 
     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 provides softer materials which may enhance patient comfort. 
     5.3.5.1.2.10 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. 
     5.3.5.1.3 Textile Membrane Having Air Impermeable Silicone Layer 
     In another example, the sealing portion  32130  (or textile membrane) may include an air impermeable silicone layer  32130 - 2  provided to (e.g., coated onto) the textile material  32130 - 1 , as shown in  FIGS.  118 - 120   . 
     The silicone layer  32130  may provide the sealing portion  32130  with flexibility and stretchability, while also providing an outer surface of the silicone layer that has a smooth feel with excellent durability and wear resistance. 
     The sealing portion  32130  may have the same or similar stretch/elasticity properties and tensile strength properties in both the wale direction and the course direction, in order to conform to a variety of facial features to achieve an effective and robust seal with the patient&#39;s face. 
     The sealing portion  32130  may have a total thickness in the range of 0.2 mm to 0.46 mm (e.g., 0.25 mm to 0.425 mm, 0.275 mm to 0.375 mm, 0.3 mm to 0.38 mm, 0.3 mm to 0.35 mm, 0.25 mm to 0.33 mm, or 0.275 mm to 0.3 mm). 
     It is noted that any material properties or material property values mentioned elsewhere in this disclosure may be applicable here to this textile membrane example (e.g., in addition to any properties or values described in this section). 
     5.3.5.1.3.1 Textile Material 
     The textile material  32130 - 1  to which the silicone layer  32130 - 2  is applied may be an elastic knitted (e.g., weft knitted) textile material. 
     The textile material may have a single jersey knit structure with a machine gauge in the range of 30-60 GG (e.g., 35 GG to 55 GG, or 44 GG to 60 GG, or 40 GG to 50 GG, or 55 GG to 60 GG, or 44 GG, or 50 GG, or 55 GG, or 60 GG). The single jersey knit structure provides a technical face and a technical back that have different appearances. As described above, 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 that contacts the patient&#39;s skin and the silicone layer  32130 - 2  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 silicone layer applied thereto. In another example, the textile material may have an interlock knit structure. 
     The textile material may be created by dope dyeing, piece dyeing, or yarn dyeing to provide a solid color or melange textile. 
     The textile material  32130 - 1  may comprise nylon (e.g., nylon 6), polyester, spandex, Roica, and/or Lycra. For example, the textile material may comprise nylon (or polyester or a nylon/polyester composite) and elastane such as spandex (or Roica or Lycra). In an example, the textile material may comprise 75-95% (e.g., 80%, 85%, 90%, or 95%) nylon (or polyester or a nylon/polyester composite) and 5-25% (e.g., 5%, 10%, 15%, or 20%) elastane (e.g., spandex (or Roica or Lycra)). In other examples, spandex (or Roica or Lycra) may be greater than 25% and nylon (or polyester or a nylon/polyester composite) may be less than 75%. 
     The yarn count of nylon may be FDY (or DTY) 20-80 D/17-144 F, where FDY is fully drawn yarn, DTY is drawn textured yarn, D is denier (i.e., linear mass density of the yarn), and F is the number of filaments per yarn as those skilled in the art will understand. The polyester yarn may be FDY (or DTY) 20-80 D/17-144 F. The nylon/polyester composite may have a yarn count that is FDY (or DTY) 20-80 D/17-144 F. In other examples, the denier for the nylon, polyester and/or nylon/polyester composite may be, for example, 30-70 D, 40-60 D, 20-30 D, 20-50 D, 50-70 D, 20 D, 40 D, 60 D, or 80 D. Additionally, in other examples, the number of filaments for the nylon, polyester and/or nylon/polyester composite may be, for example 20-130 F, 40-110 F, 60-90 F, or 70-80 F. The yarns may be multifilament yarns, as indicated by the number of filaments noted above. The spandex (or Roica or Lycra) may be 20-120 D (e.g., 40-100 D, 60-80 D, 20-40 D, 80-120 D, 20 D, 40 D, 80 D, or 120 D). Yarn count (or denier) may, at least in part, determine the textile thickness, density, elasticity and/or hand feel. 
     The textile material may have a textile weight in the range of 95 grams per square meter (gsm) to 170 gsm (e.g., 105 gsm to 160 gsm, 110 gsm to 150 gsm, 120 gsm to 140 gsm, 105 gsm, 110 gsm, 120 gsm, 130 gsm, 140 gsm, 150 gsm, or 160 gsm), which provides a relatively light weight material to facilitate patient comfort. 
     As mentioned above, the textile material may have elasticity in all directions (e.g., four-way stretch/elasticity, e.g., substantially equal elasticity in all directions, i.e., substantially equal stretchability/elasticity in the direction of the wales and the direction of the course), and at least in the lateral left-right direction of the textile membrane. The textile material is stretchable without curling at the selvedges. The stretchability/elasticity of the textile material facilitates the textile membrane in having stretchability/elasticity in all directions, thereby conforming to (e.g., stretching to accommodate) the contours of the patient&#39;s face without creating folds or creases and without causing discomfort to the patient. 
     The textile material is prepared for silicone coating, molding or lamination without silicone softener agents applied to the surface of the textile, as such agents could delaminate and affect the bonding strength of the textile. 
     It is noted that the surface texture or roughness of the yarn affects the strength of the bond between the textile material  32130 - 1  and the silicone layer  32130 - 2 . A relatively rougher surface is easier to bind to and therefore provides a stronger bond. Further, multifilament yarns have greater surface area as opposed to monofilament yarns and therefore provide a stronger bond between the textile material and the silicone layer. 
     It is noted that a cross-linker may be used to provide a chemical bond. However, in an example, no cross-linker is present, thereby providing only a physical bond. 
     The textile material  32130 - 1  forming the patient-contacting side of the sealing portion  32130  may have the same or similar surface friction and roughness in both the wale direction and the course direction, so that the bonding force of the silicone layer  32130 - 2  with the textile material is substantially uniform in all directions (i.e., across the entire surface of the textile material). This serves to prevent delamination of the silicone layer  32130 - 2  from the textile material. The same or similar surface friction and roughness in the directions of the wales and the course also provide a soft and smooth surface on the patient contacting side that is comfortable to the patient. In an example, the mean value of the coefficient of friction (MIU) in the direction of the wales and in the direction of the course may be 0.7 to 5.0 (e.g., 1.0 to 4.0, 1.5 to 3.5, 2.0 to 3.0, 1.0, 1.5, 2.5, 3.5, or 5.0). Additionally, the mean deviation of surface roughness (SMD) in the direction of the wales and in the direction of the course may be 0.7 to 5.0 (e.g., 1.0 to 4.0, 1.5 to 3.5, 2.0 to 3.0, 1.0, 1.5, 2.5, 3.5, or 5.0). 
     In one embodiment, the mean value of the coefficient of friction (MIU) in the direction of the wales and in the direction of the course may be 0.3-2.0 (e.g., 0.5 to 1.8, 0.8 to 1.5 or 1.0 to 1.5, 0.5, 1.0, 1.5, or 2.0) based on the surface testing method KES-FB4 on a sample with a dimension of 200 mm×200 mm. Additionally, the mean deviation of surface roughness (SMD) in the direction of the wales and in the direction of the course may be 0.3 to 2.0 (e.g., 0.5 to 1.8, 0.8 to 1.5, 1.0 to 1.5, 0.5, 1.0, 1.5, or 2.0). 
     The textile material may have good pilling resistance and excellent snagging resistance (e.g., both grade 5, i.e., no or very weak formation of pills, and no or insignificant snagging). 
     The sealing portion  32130  may be stronger in the direction of the wales, while being highly extensible in the direction of the course, which provides good dimensional stability when the sealing portion is stretched. 
     The textile material  32130 - 1  may have a thickness in the range of 0.18 mm to 0.32 mm (e.g., 0.2 mm to 0.3 mm, 0.2 m to 0.28 mm, or 0.225 mm to 0.275 mm). 
     5.3.5.1.3.2 Air Impermeable Silicone Layer 
     The silicone layer  32130 - 2  may have a clear or transparent appearance. 
     The thickness of the silicone layer  32130 - 2  may be in the range of 0.04 mm to 0.125 mm (e.g., 0.05 mm to 0.1 mm, 0.06 mm to 0.09 mm, 0.07 mm to 0.08 mm, 0.05 mm, 0.075 mm, 0.1 mm or 0.125 mm). This creates a robust air impermeable layer that is durable. It is noted, however, that since the silicone layer penetrates into the textile material during curing, the thickness of the silicone layer  32130 - 2  may not be uniform across the sealing portion  32130 . 
     5.3.5.2 Illustrated Examples of Support Structure and Sealing Portion Arrangements 
       FIGS.  81 - 112    show a number of different cushion assembly configurations including various support structure and sealing portion arrangements and/or processes. It is noted that these examples can be applied to any of the patient interfaces and/or cushion assemblies described in the disclosure. Further, any feature of any example may be applied to a different example and/or used with different features. The plenum chambers, support structures and sealing portions shown in these figures may be constructed from any of the suitable materials described earlier. It should also be noted that components, for example the support structure, may comprise more than one material. For example, an underlying cushion of a support structure may comprise a different material than other portions of the support structure. 
     Referring to  FIG.  83   , support structure  10120  is removably connected to plenum chamber  10200  via clip  10126  on the support structure and connector  10210  on the plenum chamber to form cavity  10001 . In some examples, the clip  10126  may be formed from polyurethane, polypropylene (PP) or polyethylene terephthalate (PET). Plenum chamber  10200  may be constructed from a material that is more rigid than the clip, such as polycarbonate or polyurethane having a higher Shore A hardness than the clip. The support structure  10120  and sealing portion  10130  are configured into a cushion arrangement having a single air assisted sealing portion  10130  (e.g., textile membrane). 
     The connection between the outer perimeter (or outer edge) of the textile membrane and the inner edge of the support structure may be formed in a number of different ways. As shown in  FIGS.  83  and  85   , the connection may form a lap joint where an edge portion of the textile membrane overlaps with an edge portion of the support structure. In an example, an attachment portion  10122  of the support structure may form a recessed portion to receive the sealing portion  10130  so that the support structure and sealing portion form a smooth outer surface, as shown in  FIG.  83   . The overlap may be minimal and provided only for manufacturing purposes (i.e., necessary in order to attach the sealing portion and the support structure) by for example, overmolding and/or injection molding. This is in contrast to conventional arrangements in which the overlapping region may be arranged to provide additional support (e.g., stiffness) to the sealing portion due to the presence of the support structure (in such arrangements, the overlap may vary around the perimeter of the seal-forming structure to vary the level of support or stiffness (e.g., less overlap, less support, more flexibility, less tension in sensitive nasal bridge region). 
     In contrast to the above described lap joint, the connection between the textile membrane and the support structure may form an end-to-end joint (e.g., butt joint), as shown in  FIG.  84   . Due to manufacturing techniques (e.g., overmolding, injection molding), the end-to-end joint may have some overlap, however such overlap is negligible and constant around the perimeter of the sealing portion at the connection with the support structure. In other words, as described above, any overlap of the support structure and the textile membrane is not designed to adjust the stiffness, tension, flexibility or support in different regions of the face (e.g., less overlap, less support, more flexible, less tension in sensitive nasal bridge region). 
     Instead, whether a lap joint or end-to-end joint is provided, the present arrangement allows the compliant textile membrane to appropriately accommodate the patient&#39;s facial features. That is, the seal-forming structure is designed to allow the patient&#39;s facial features (e.g., nose) to sink into the textile membrane which compliantly receives the patient&#39;s face. 
     The sealing portion may be glued, molded (e.g., overmolded or injection molded) or otherwise attached to the support structure. In an alternative example, the recessed portion may be removed and the attachment portion  10122  may be used to attach the sealing portion  10130  and the support structure  10120  end to end, as shown in  FIG.  84   . Further,  FIG.  84    also illustrates that portions (d1) of the support structure  10120  adjacent to or connecting to the plenum chamber  10200  may be thicker than portions (d2) of the support structure  10120  adjacent to or connecting to the sealing portion  10130  so as to provide structural stability at the connection with the plenum chamber and flexibility at the interface with the patient. 
     In  FIG.  85   , the support structure  10120  includes an underlying cushion  10121 . The support structure also includes a sealing lip  10124  to seal the interface between the plenum chamber  10200  and the support structure  10120 . The attachment portion  10122  of the support structure may be configured so as sandwich an end portion of the sealing portion between opposing sections of the attachment portion  10122 . 
     In another example, plenum chamber  11200  may have an underlying cushion  11121  attached to an inner portion thereof, as shown in  FIG.  86   . As such, the underlying cushion  11121  may be permanently attached to the plenum chamber  11200 , whereas the support structure  10120  and sealing portion  10130  may be removably connected to the plenum chamber via clip  10126  and connector  10210 . 
     Referring to  FIGS.  87  and  88   , support structure  10120  may have an external biasing portion  10140  or an internal biasing portion  10140 ′ which may utilize the internal air pressure in the cavity to dynamically support the support structure and sealing portion  10130 . The support structure  10120  may include an inwardly curved end portion  10142  thus forming an air-assisted support region  10144  which may optimize the force, due to air pressure within the cavity, acting on the support structure and sealing portion to urge the sealing portion into sealing contact with the patient&#39;s face. 
     Turning to  FIG.  89   , support structure  12120  includes an underlying cushion  12121 . The support structure and/or underlying cushion may be formed, for example, of molded polyurethane. In this example, the sealing portion  10130  is adhered to the support structure with an adhesive  10150  (e.g., heat-activated polyurethane, tape, glue). 
     In  FIG.  90 A , support structure  15120  is removably connected to plenum chamber  10200 . The support structure includes an underlying cushion  15121 . In this example, the support structure is formed of foam (e.g., polyurethane foam molding), but may also be formed of TPE, TPU or any other suitable material. The sealing portion  10130  may have a membrane layer or film laminate layer  10131  to provide a substantially air-tight material, as shown in  FIG.  90 A- 1   . Alternatively, the support structure  15120  may be glued, bonded, or otherwise attached to the plenum chamber  10200 . 
       FIG.  90 B  shows an example similar to that of  FIG.  90 A , however the sealing portion  10130  in  FIG.  90 B  is connected directly to the plenum chamber  10200  and may form a seamless cover over the underlying cushion  15121 . The sealing portion  10130  and underlying cushion  15121  may be glued or otherwise bonded to the plenum chamber  10200 . Alternatively, the sealing portion  10130  and/or the underlying cushion  15121  may be removably connected to the plenum chamber. 
     Referring to  FIG.  91   , support structure  17120  includes a first portion  17123  and an underlying cushion  17121 . The first portion  17123 , which may connect to the plenum chamber, may be constructed from a material that is more rigid than a material of the underlying cushion  17121 . For example, the first portion  17123  and the underlying cushion may both be constructed of polyurethane, but the polyurethane material of the first portion may have a higher hardness than the material of the underlying cushion. A reinforcing member  17125  may extend along an outer perimeter of the cushion bridging the intersection between the first portion  17123  and the underlying cushion  17121  to provide structural support. 
     As shown in  FIG.  92   , support structure  23120  may include an underlying cushion  23121  (e.g., constructed of TPU) having a U-shape or hook shape. The underlying cushion may include a clip  23126  for removable connection to the cushion (e.g., the frame, plenum chamber, or other portion of the support structure). Alternatively, the sealing portion  10130  may be attached to the support structure  23120  as a removable module that as a unit may be removably connected to the cushion (e.g., the frame, plenum chamber, or other portion of the support structure). The sealing portion  10130  may be attached to the underlying cushion  23121 , for example, by thermoforming. The underlying cushion also may be shaped by thermoforming. 
     Support structure  24120  may include a rigid clip  24126  that supports an underlying cushion  24121 , as shown in  FIG.  93   . The underlying cushion  24121  may include an outer textile layer  10132  and an inner layer (e.g., constructed of foam) enclosed by the textile layer and the clip. The support structure  24120  may be removably connectable to the cushion (e.g., the frame, plenum chamber, or other portion of the support structure). Alternatively, the sealing portion  10130  may be attached to the support structure  24120  as a removable module that as a unit may be removably connected to the cushion (e.g., the frame, plenum chamber, or other portion of the support structure). The sealing portion  10130  may be attached to the underlying cushion  24121 , for example, by thermoforming. The underlying cushion also may be shaped by thermoforming. 
     Referring to  FIG.  94   , support structure  18120  may include a rigid clip  18126  that supports an underlying cushion  18121  (e.g., constructed of foam). The support structure  18120  may be removably connectable to the cushion (e.g., the frame, plenum chamber, or other portion of the support structure). Alternatively, the sealing portion  10130  may be attached to the support structure  18120  as a removable module that as a unit may be removably connected to the cushion (e.g., the frame, plenum chamber, or other portion of the support structure). The sealing portion  10130  may be attached to the underlying cushion  18121 , for example, by thermoforming. The underlying cushion also may be shaped by thermoforming. 
     Turning to  FIG.  95   , support structure  19120  includes a first portion  19123  and an underlying cushion  19121 . The first portion  19123 , which may connect to the plenum chamber, may be constructed of a material that is more rigid than a material of the underlying cushion  19121 . For example, the first portion may be constructed from polyurethane and the underlying cushion may be constructed from foam. 
     Referring to  FIG.  96   , support structure  20120  includes a first portion  20123  and an underlying cushion  20121 . The first portion  20123 , which may connect to the plenum chamber, may be constructed from a material that has different rigidity or Shore A hardness than a material of the underlying cushion. For example, the first portion  20123  and the underlying cushion  20121  may both be constructed of polyurethane, whereas the first portion  20123  may be less or more rigid or have higher or lower Shore A hardness than the underlying cushion  20121 . In an alternative example, the first portion  20123  and the underlying cushion  20121  may be constructed of the same material and may have the same rigidity or Shore A hardness. 
     The support structure  21120  of  FIG.  97    includes a first portion  21123  and an underlying cushion  21121  and is similar to support structure  20120  discussed above, except that the cushion includes a second sealing portion layer (e.g., textile layer  10132 ) forming dual textile membranes. The underlying cushion  21121  may be molded or otherwise attached to an underside of the textile layer  10132 . 
     Referring to  FIG.  98   , support structure  22120  includes a first portion  22123  and an underlying cushion  22121  and is similar to support structure  21120  discussed above, except that the underlying cushion  22121  is a foam layer laminated or otherwise attached to the underside of the textile layer  10132 . 
     Turning to  FIG.  99   , the illustrated cushion assembly includes a dual sealing portion structure without underlying cushion support. The cushion assembly includes a first textile layer  10130  and second textile layer  10132  connected to support structure  10120 . 
     The cushion assembly in  FIG.  100    is similar to the cushion assembly in  FIG.  99   , except that the sealing portion includes a support section  10135  from which the first textile layer  10130  and the second textile layer  10132  extend. Support section  10135  may be constructed of TPU or foam (e.g., polyurethane foam molding), for example. The support section  10135  may add resilience to the sealing portion and allow the textile layers to spring back more quickly from external forces. The support section  10135  may be removably connected, as a modular unit with the textile layers, to support structure  10120 . In an alternative example, the support section  10135  is removably connected to the plenum chamber. 
     Turning to  FIGS.  101  and  102   , sealing portion modular assembly  26400  may be permanently or removably connected (e.g., with a mechanical clip) to support structure  26120  (or alternatively to plenum chamber  10200 ). The sealing portion modular assembly may include a skeleton supporting frame  26450  having the sealing portion  10130  attached thereto. The sealing portion  10130  may be thermoformed or insert molded, for example, to attach the sealing portion to the supporting frame  26450 . The thermoforming or molding process and/or the supporting frame itself may form and hold the sealing portion in a curved or three-dimensional shape. Support structure  26120  may be constructed from insert molded polyurethane, for example. 
     In the example of  FIG.  103   , the textile membrane  10130  and/or support structure may be configured to be removable or modular. As illustrated in  FIG.  103   , the textile membrane  10130  may be attached to a modular support structure  26480  around its perimeter. The modular support structure  26480  may then be removably engaged as a module to the plenum chamber. A modular form may advantageously reduce the occurrence of protruding folds or wrinkles in the textile membrane surface. 
     In some forms, the textile membrane may be a sleeve or sock that is adapted to cover and be retained above the plenum chamber or support structure. 
     A modular textile membrane seal may also substantially simplify the manufacturing as all the complex bonding may be done in a simple unstressed state. While some textiles may be treated to have substantially self-cleaning properties, the use of a modular textile membrane may also advantageously provide a cheaper and more hygienic alternative. In some forms, the textile membrane or support structure can be a removable and/or replaceable sub-assembly that attaches to the plenum chamber, support structure or frame assembly. 
     In forms where the textile membrane is attached to a supporting frame of the modular supporting structure  26480 , the supporting frame can be pre-formed to be either flat (as shown in  FIG.  103   ) or as a 3-D structure such as an arc. 
     In some forms, the modular supporting structure  26480  can engage the plenum chamber through corresponding male/female location pins/holes. In some forms, the modular supporting structure may utilize a tongue and groove arrangement around the peripheral sides of the structure to form an effective air-tight seal with the plenum chamber. The modular supporting structure  26480  may be formed, for example, from a plastic material, polyurethane, or similar materials. 
     Turning to  FIGS.  104 - 106   , a process of insert molding the sealing portion (e.g., a textile material) as an In Mold Decoration (IMD) is illustrated. As shown in  FIGS.  104  and  105   , a first mold  26500  may be brought into contact with a second mold  26550  to attach the sealing portion  10130  to the supporting frame  26450  while also imparting curvature to the sealing portion. The molding process may also stretch the sealing portion  10130  so that attachment of the sealing portion to the supporting frame  26450  maintains the sealing portion in tension prior to use. 
     Referring to  FIGS.  107  and  108   , a one size fits all cushion assembly  27105  is shown. Cushion assembly  27105  may include a sealing portion  10130  attached to an upper supporting frame portion  27202  and a lower supporting frame portion  27204 . The upper supporting frame portion  27202  may be spaced from the lower supporting frame portion  27204  thereby forming an elastic region  27108  in which the sealing portion may stretch to distance the upper supporting frame portion  27202  and the lower supporting frame portion  27204  to accommodate a range of patient face sizes. 
     A patient&#39;s face may be scanned to create a custom mask, as shown in  FIGS.  109  and  110   . A three-dimensional profile may be obtained by facial scan to create a cushion assembly  28105  including a sealing portion  10130  attached to a supporting frame  28200 . Supporting frame  28200  may include a relatively rigid support element (e.g., a polyurethane molded piece) and a cushioning element (e.g., foam) between the support element and the sealing portion. As shown in  FIG.  84   , the cushion assembly may be arranged to stretch to accommodate different patient face sizes. 
     In some examples of the nasal cushion, such as shown for example in  FIGS.  111  and  112   , the support structure  3120  may actually be configured to deform inwardly at certain fold or pivot points. For example, thinner regions of the support structure may be designed to created fold or pivot points. In an example, a bottom central portion (e.g., nose base region  3112 ) of the support structure  3120  may have a relatively reduced thickness such that when stress is applied to the walls of the support structure due to engagement by the patient&#39;s face, the bottom central portion of the support structure may create a pivot point thus allowing the left and right lateral sides of the support structure to deform inwardly to cradle the patient&#39;s face (e.g., nose) thereby accommodating engagement of the patient&#39;. An upper anterior region  3109  may also have a reduced thickness as compared to lateral support regions  3122  so as to create a fold or pivot point. 
     Thus, in the example of  FIGS.  111  and  112   , the support structure  3120  may have three regions of different stiffness (e.g., by having different thicknesses). The upper anterior region  3109  may have a thickness that is the same as or greater than the thickness of the nose base region  3112 . The lateral support regions  3122  may have a thickness that is greater than the thickness of the upper anterior region  3109  and the nose base region  3112 . Thus, the lateral support region may be stiffer than the upper anterior region  3109  which may be stiffer than the nose base region  3112 . It is noted that the plenum chamber and the support structure may both be formed of a flexible material (e.g., silicone) and may form a one-piece structure (e.g., molded together). This may assist the bending/folding/pivoting of the cushion assembly to accommodate the patient&#39;s facial features. In an example, the seal-forming structure may be an extension of the plenum chamber or formed as a part of the plenum chamber such that the plenum chamber encompasses the seal-forming structure. In such an example, the support structure and textile membrane may be considered part of the plenum chamber. 
     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 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  4272  and flow rate sensors  4274 . 
     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 central controller, a therapy device controller, a pressure generator, one or more protection circuits, memory, transducers, data communication interface and one or more output devices. 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 . 
     5.5 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. 
     5.5.1 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. atmospheric air enriched with oxygen. 
     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. Total flow rate, Qt, is the flow rate of air leaving the RPT device. 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. 
     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. 
     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. 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 mask pressure Pm at the current instant of time, is given the symbol Pt. 
     Respiratory Pressure Therapy (RPT): 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. 
     5.5.1.1 Materials 
     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. 
     Polycarbonate: a thermoplastic polymer of Bisphenol-A Carbonate. 
     5.5.1.2 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 129hermos-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. 
     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. 
     5.5.2 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:
         (ii) 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.   (ii) Chair-shaped: Having a single local peak, the peak being at the leading edge, followed by a relatively flat portion.   (ii) 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:
         (ii) 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. 
     5.5.3 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 mask pressure which the ventilator will attempt to achieve at a given time. 
     End expiratory pressure (EEP): Desired mask 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 mask 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 delivers a breath of air to a spontaneously breathing patient, it is said to be triggered to do so at the initiation of the respiratory portion of the breathing cycle by the patient&#39;s efforts. 
     5.5.4 Anatomy 
     5.5.4.1 Anatomy of the Face 
     Ala: the external outer wall or “wing” of each nostril (plural: alar) 
     Alar angle: 
     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): 
     Lip, upper (labrale superius): 
     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 
     5.5.4.2 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. 
     5.5.4.3 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). 
     5.5.5 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 air-tight. 
     Functional dead space: 
     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 thin structural element that has:
         resistance to being stretched; and   substantially no resistance to bending.       

     A membrane may be curved. 
     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 structural element 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. 
     5.5.6 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. 
     5.5.6.1 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. 
     5.5.6.2 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’.) 
     5.5.6.3 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 T2&gt;T1, 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 . 
     5.5.6.4 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. 
     5.6 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. 
     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. 
     5.7 Reference Signs List 
       
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Step 
                   10 
               
               
                   
                 Step 
                   12 
               
               
                   
                 Step 
                   14 
               
               
                   
                 Curve 
                   35 
               
               
                   
                 Transition portion 
                   36 
               
               
                   
                 Wale 
                   70 
               
               
                   
                 Course 
                   80 
               
               
                   
                 Warp knit 
                   90 
               
               
                   
                 Weft knit 
                  100 
               
               
                   
                 Patient 
                  1000 
               
               
                   
                 Bed partner 
                  1100 
               
               
                   
                 Patient interface 
                  3000 
               
               
                   
                 Seal - forming structure 
                  3100 
               
               
                   
                 Cavity 
                  3101 
               
               
                   
                 Naris opening 
                  3102 
               
               
                   
                 Bridge portion 
                  3104 
               
               
                   
                 Cushion assembly 
                  3105 
               
               
                   
                 Frame connection opening 
                  3106 
               
               
                   
                 Upper anterior region 
                  3109 
               
               
                   
                 Nose base region 
                  3112 
               
               
                   
                 Support structure 
                  3120 
               
               
                   
                 Lateral support region 
                  3122 
               
               
                   
                 Sealing portion 
                  3130 
               
               
                   
                 Plenum chamber 
                  3200 
               
               
                   
                 Plenum chamber lateral end 
                  3202 
               
               
                   
                 Plenum chamber connector 
                  3204 
               
               
                   
                 Notch 
                  3206 
               
               
                   
                 Chamfered edge 
                  3208 
               
               
                   
                 Slot 
                  3209 
               
               
                   
                 Chord 
                  3210 
               
               
                   
                 Superior point 
                  3220 
               
               
                   
                 Inferior point 
                  3230 
               
               
                   
                 Lateral sides 
                  3250 
               
               
                   
                 Comer region 
                  3252 
               
               
                   
                 Medial subnasale region 
                  3260 
               
               
                   
                 Medial pronasale region 
                  3270 
               
               
                   
                 Positioning and stabilising structure 
                  3300 
               
               
                   
                 Lateral portion 
                  3302 
               
               
                   
                 Superior portion 
                  3304 
               
               
                   
                 Hub 
                  3306 
               
               
                   
                 Tab 
                  3308 
               
               
                   
                 Posterior strap 
                  3310 
               
               
                   
                 Posterior strap end portion 
                  3311 
               
               
                   
                 Sleeve 
                  3312 
               
               
                   
                 End 
                  3314 
               
               
                   
                 Vent 
                  3400 
               
               
                   
                 Decoupling structure vent 
                  3402 
               
               
                   
                 Decoupling structure 
                  3500 
               
               
                   
                 Swivel connector 
                  3502 
               
               
                   
                 Button 
                  3504 
               
               
                   
                 Connection port 
                  3600 
               
               
                   
                 Forehead support 
                  3700 
               
               
                   
                 RPT device 
                  4000 
               
               
                   
                 External housing 
                  4010 
               
               
                   
                 Upper portion 
                  4012 
               
               
                   
                 Lower portion 
                  4014 
               
               
                   
                 Panel 
                  4015 
               
               
                   
                 Chassis 
                  4016 
               
               
                   
                 Handle 
                  4018 
               
               
                   
                 Pneumatic block 
                  4020 
               
               
                   
                 Inlet air filter 
                  4112 
               
               
                   
                 Inlet muffler 
                  4122 
               
               
                   
                 Outlet muffler 
                  4124 
               
               
                   
                 Blower 
                  4142 
               
               
                   
                 Air circuit 
                  4170 
               
               
                   
                 Electrical components 
                  4200 
               
               
                   
                 Printed Circuit Board Assembly (PCBA) 
                  4202 
               
               
                   
                 Power supply 
                  4210 
               
               
                   
                 Input device 
                  4220 
               
               
                   
                 Pressure sensor 
                  4272 
               
               
                   
                 Flow rate sensor 
                  4274 
               
               
                   
                 Algorithms 
                  4300 
               
               
                   
                 Humidifier 
                  5000 
               
               
                   
                 Seal-forming structure 
                  5100 
               
               
                   
                 Cushion assembly 
                  5105 
               
               
                   
                 Support structure 
                  5120 
               
               
                   
                 Sealing portion 
                  5130 
               
               
                   
                 Patient interface 
                  6000 
               
               
                   
                 Seal-forming structure 
                  6100 
               
               
                   
                 Cushion assembly 
                  6105 
               
               
                   
                 Support structure 
                  6120 
               
               
                   
                 Sealing portion 
                  6130 
               
               
                   
                 Positioning and stabilizing structure 
                  6300 
               
               
                   
                 Left arm 
                  6305 
               
               
                   
                 Right arm 
                  6307 
               
               
                   
                 Joint 
                  6312 
               
               
                   
                 Air delivery 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 
               
               
                   
                 Connection port 
                  6600 
               
               
                   
                 Seal-forming structure 
                  7100 
               
               
                   
                 Cushion assembly 
                  7105 
               
               
                   
                 Support structure 
                  7120 
               
               
                   
                 Sealing portion 
                  7130 
               
               
                   
                 Seal-forming structure 
                  8100 
               
               
                   
                 Cushion assembly 
                  8105 
               
               
                   
                 Support structure 
                  8120 
               
               
                   
                 End portion 
                  8122 
               
               
                   
                 Sealing portion 
                  8130 
               
               
                   
                 Sealing portion 
                  8130 
               
               
                   
                 Patient interface 
                  9000 
               
               
                   
                 Seal-forming structure 
                  9100 
               
               
                   
                 Cushion assembly 
                  9105 
               
               
                   
                 Support structure 
                  9120 
               
               
                   
                 Connector 
                  9122 
               
               
                   
                 Sealing portion 
                  9130 
               
               
                   
                 Frame 
                  9200 
               
               
                   
                 Headgear attachment portions 
                  9210 
               
               
                   
                 Positioning and stabilising structure 
                  9300 
               
               
                   
                 Rear strap 
                  9310 
               
               
                   
                 Crown strap 
                  9312 
               
               
                   
                 Cavity 
                 10001 
               
               
                   
                 Support structure 
                 10120 
               
               
                   
                 Underlying cushion 
                 10121 
               
               
                   
                 Attachment portion 
                 10122 
               
               
                   
                 Sealing lip 
                 10124 
               
               
                   
                 Clip 
                 10126 
               
               
                   
                 Sealing portion 
                 10130 
               
               
                   
                 Membrane layer 
                 10131 
               
               
                   
                 Sealing portion 
                 10132 
               
               
                   
                 Textile material 
                 10133 
               
               
                   
                 Support section 
                 10135 
               
               
                   
                 Biasing portion 
                 10140 
               
               
                   
                 Biasing portion 
                 10140′ 
               
               
                   
                 Inwardly curved end portion 
                 10142 
               
               
                   
                 Air-assisted support region 
                 10144 
               
               
                   
                 Adhesive 
                 10150 
               
               
                   
                 Plenum chamber 
                 10200 
               
               
                   
                 Connector 
                 10210 
               
               
                   
                 Underlying cushion 
                 11121 
               
               
                   
                 Plenum chamber 
                 11200 
               
               
                   
                 Support structure 
                 12120 
               
               
                   
                 Underlying cushion 
                 12121 
               
               
                   
                 Plenum chamber 
                 13200 
               
               
                   
                 Patient interface 
                 14000 
               
               
                   
                 Cavity 
                 14001 
               
               
                   
                 Seal-forming structure 
                 14100 
               
               
                   
                 Nasal portion 
                 14101 
               
               
                   
                 Oral portion 
                 14102 
               
               
                   
                 Nasal portion holes 
                 14103 
               
               
                   
                 Oral portion hole 
                 14104 
               
               
                   
                 Cushion assembly 
                 14105 
               
               
                   
                 Bridge portion 
                 14106 
               
               
                   
                 Support structure 
                 14120 
               
               
                   
                 Underlying cushion 
                 14121 
               
               
                   
                 Underlying cushion 
                 14122 
               
               
                   
                 Sealing portion 
                 14130 
               
               
                   
                 Plenum chamber 
                 14200 
               
               
                   
                 Positioning and stabilising structure 
                 14300 
               
               
                   
                 Clip 
                 14301 
               
               
                   
                 Upper strap 
                 14302 
               
               
                   
                 Lower strap 
                 14303 
               
               
                   
                 Strap connector 
                 14304 
               
               
                   
                 Vent 
                 14400 
               
               
                   
                 Connection port 
                 14600 
               
               
                   
                 Conduit connector 
                 14800 
               
               
                   
                 Conduit connector housing 
                 14801 
               
               
                   
                 Conduit connection end 
                 14802 
               
               
                   
                 Conduit connector inlet hole 
                 14803 
               
               
                   
                 Conduit connector vent hole 
                 14831 
               
               
                   
                 Anti-asphyxia valve assembly 
                 14850 
               
               
                   
                 Conduit 
                 14900 
               
               
                   
                 Sleeve 
                 14901 
               
               
                   
                 Tie connector 
                 14902 
               
               
                   
                 Connection port housing 
                 14903 
               
               
                   
                 Support structure 
                 15120 
               
               
                   
                 Underlying cushion 
                 15121 
               
               
                   
                 Patient interface 
                 16000 
               
               
                   
                 Frame assembly 
                 16100 
               
               
                   
                 Opening 
                 16105 
               
               
                   
                 Shroud 
                 16110 
               
               
                   
                 Upper headgear connector arm 
                 16134 
               
               
                   
                 Central flexible portion 
                 16140 
               
               
                   
                 Peripheral flexible portion 
                 16145 
               
               
                   
                 Lower headgear connector arm 
                 16154 
               
               
                   
                 Magnetic connector 
                 16155 
               
               
                   
                 Headgear clip 
                 16160 
               
               
                   
                 Cushion assembly 
                 16175 
               
               
                   
                 Shell 
                 16180 
               
               
                   
                 Seal - forming structure 
                 16200 
               
               
                   
                 Support structure 
                 16220 
               
               
                   
                 Underlying cushion 
                 16221 
               
               
                   
                 Sealing portion 
                 16230 
               
               
                   
                 Opening 
                 16305 
               
               
                   
                 Flange 
                 16310 
               
               
                   
                 Cavity 
                 16500 
               
               
                   
                 Elbow assembly 
                 16600 
               
               
                   
                 First end portion 
                 16610 
               
               
                   
                 Second end portion 
                 16620 
               
               
                   
                 Swivel connector 
                 16625 
               
               
                   
                 Channel 
                 16645 
               
               
                   
                 Pinch arm 
                 16650 
               
               
                   
                 Vent holes 
                 16700 
               
               
                   
                 Arm cover 
                 16750 
               
               
                   
                 Headgear 
                 16800 
               
               
                   
                 Upper side strap 
                 16802 
               
               
                   
                 Lower side strap 
                 16804 
               
               
                   
                 Crown strap 
                 16806 
               
               
                   
                 Support structure 
                 17120 
               
               
                   
                 Underlying cushion 
                 17121 
               
               
                   
                 First portion 
                 17123 
               
               
                   
                 Reinforcing member 
                 17125 
               
               
                   
                 Support structure 
                 18120 
               
               
                   
                 Underlying cushion 
                 18121 
               
               
                   
                 Clip 
                 18126 
               
               
                   
                 Support structure 
                 19120 
               
               
                   
                 Underlying cushion 
                 19121 
               
               
                   
                 First portion 
                 19123 
               
               
                   
                 Support structure 
                 20120 
               
               
                   
                 Underlying cushion 
                 20121 
               
               
                   
                 First portion 
                 20123 
               
               
                   
                 Support structure 
                 21120 
               
               
                   
                 Underlying cushion 
                 21121 
               
               
                   
                 First portion 
                 21123 
               
               
                   
                 Support structure 
                 22120 
               
               
                   
                 Underlying cushion 
                 22121 
               
               
                   
                 First portion 
                 22123 
               
               
                   
                 Support structure 
                 23120 
               
               
                   
                 Underlying cushion 
                 23121 
               
               
                   
                 Clip 
                 23126 
               
               
                   
                 Support structure 
                 24120 
               
               
                   
                 Underlying cushion 
                 24121 
               
               
                   
                 Inner layer 
                 24124 
               
               
                   
                 Clip 
                 24126 
               
               
                   
                 Support structure 
                 26120 
               
               
                   
                 Sealing portion modular assembly 
                 26400 
               
               
                   
                 Supporting frame 
                 26450 
               
               
                   
                 Modular supporting structure 
                 26480 
               
               
                   
                 First mold 
                 26500 
               
               
                   
                 Second mold 
                 26550 
               
               
                   
                 Cushion assembly 
                 27105 
               
               
                   
                 Upper supporting frame portion 
                 27202 
               
               
                   
                 Lower supporting frame portion 
                 27204 
               
               
                   
                 Elastic region 
                 27108 
               
               
                   
                 Cushion assembly 
                 28105 
               
               
                   
                 Supporting frame 
                 28200 
               
               
                   
                 Seal-forming structure 
                 29100 
               
               
                   
                 Cushion assembly 
                 29105 
               
               
                   
                 Support structure 
                 29120 
               
               
                   
                 Sealing portion 
                 29130 
               
               
                   
                 Grip pad 
                 29150 
               
               
                   
                 Patient interface 
                 30000 
               
               
                   
                 Cavity 
                 30001 
               
               
                   
                 Seal-forming structure 
                 30100 
               
               
                   
                 Nasal portion 
                 30101 
               
               
                   
                 Oral portion 
                 30102 
               
               
                   
                 Nasal portion holes 
                 30103 
               
               
                   
                 Oral portion hole 
                 30104 
               
               
                   
                 Cushion assembly 
                 30105 
               
               
                   
                 Support structure 
                 30120 
               
               
                   
                 Sealing portion 
                 30130 
               
               
                   
                 Plenum chamber or shell 
                 30200 
               
               
                   
                 Inlet port 
                 30240 
               
               
                   
                 Positioning and stabilising structure 
                 30300 
               
               
                   
                 Upper straps 
                 30310 
               
               
                   
                 Upper strap connection points 
                 30315 
               
               
                   
                 Lower straps 
                 30320 
               
               
                   
                 Lower strap connection point 
                 30325 
               
               
                   
                 Lower strap clip 
                 30326 
               
               
                   
                 Top crown strap 
                 30330 
               
               
                   
                 Lateral crown straps 
                 30332 
               
               
                   
                 Neck strap 
                 30334 
               
               
                   
                 Frame 
                 30350 
               
               
                   
                 Frame inlet connection port 
                 30354 
               
               
                   
                 Connection rim 
                 30355 
               
               
                   
                 Vent 
                 30400 
               
               
                   
                 Swivel elbow assembly 
                 30610 
               
               
                   
                 Connection port 
                 30600 
               
               
                   
                 Cavity 
                 31001 
               
               
                   
                 Seal-forming structure 
                 31100 
               
               
                   
                 Nasal portion 
                 31101 
               
               
                   
                 Oral portion 
                 31102 
               
               
                   
                 Nasal portion holes 
                 31103 
               
               
                   
                 Oral portion hole 
                 31104 
               
               
                   
                 Cushion assembly 
                 31105 
               
               
                   
                 Support structure 
                 31120 
               
               
                   
                 Sealing portion 
                 31130 
               
               
                   
                 Grip pad 
                 31150 
               
               
                   
                 Plenum chamber 
                 31200 
               
               
                   
                 Plenum chamber holes 
                 31210 
               
               
                   
                 Vent 
                 31400 
               
               
                   
                 Sealing portion 
                 32130 
               
               
                   
                 Textile material 
                 32130-1 
               
               
                   
                 Silicone Layer 
                 32130-2