Patent Description:
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 "<NPL>.

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 <NUM> to <NUM> seconds in duration, sometimes <NUM> to <NUM> 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 <CIT>).

Cheyne-Stokes Respiration (CSR) is another form of sleep disordered breathing. CSR is a disorder of a patient'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 <CIT>).

Respiratory failure is an umbrella term for respiratory disorders in which the lungs are unable to inspire sufficient oxygen or exhale sufficient CO<NUM> to meet the patient'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.

Various therapies, such as Continuous Positive Airway Pressure (CPAP) therapy, Non-invasive ventilation (NIV) 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.

These therapies may be provided by a treatment system or device. Such systems and devices may also be used to diagnose 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.

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'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 <NUM> cmH<NUM>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 <NUM> cmH<NUM>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'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.

Patient interfaces may include a seal-forming structure. Since it is in direct contact with the patient's face, the shape and configuration of the seal-forming structure can have a direct impact the effectiveness and comfort of the patient interface.

A patient interface may be partly characterised according to the design intent of where the seal-forming structure is to engage with the face in use. In one form of patient interface, a seal-forming structure may comprise a first sub-portion to form a seal around the left naris and a second sub-portion to form a seal around the right naris. In one form of patient interface, a seal-forming structure may comprise a single element that surrounds both nares in use. Such single element may be designed to for example overlay an upper lip region and a nasal bridge region of a face. In one form of patient interface a seal-forming structure may comprise an element that surrounds a mouth region in use, e.g. by forming a seal on a lower lip region of a face. In one form of patient interface, a seal-forming structure may comprise a single element that surrounds both nares and a mouth region in use. These different types of patient interfaces may be known by a variety of names by their manufacturer including nasal masks, full-face masks, nasal pillows, nasal puffs and oro-nasal masks.

A seal-forming structure that may be effective in one region of a patient's face may be inappropriate in another region, e.g. because of the different shape, structure, variability and sensitivity regions of the patient's face. For example, a seal on swimming goggles that overlays a patient's forehead may not be appropriate to use on a patient'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's face, and the seal-forming structure of the mass-manufactured patient interface, one or both must adapt in order for a seal to form.

One type of seal-forming structure extends around the periphery of the patient interface, and is intended to seal against the patient's face when force is applied to the patient interface with the seal-forming structure in confronting engagement with the patient's face. The seal-forming structure may include an air or fluid filled cushion, or a moulded or formed surface of a resilient seal element made of an elastomer such as a rubber. With this type of seal-forming structure, if the fit is not adequate, there will be gaps between the seal-forming structure and the face, and additional force will be required to force the patient interface against the face in order to achieve a seal.

Another type of seal-forming structure incorporates a flap seal of thin material positioned about the periphery of the mask so as to provide a self-sealing action against the face of the patient when positive pressure is applied within the mask. Like the previous style of seal forming portion, if the match between the face and the mask is not good, additional force may be required to achieve a seal, or the mask may leak. Furthermore, if the shape of the seal-forming structure does not match that of the patient, it may crease or buckle in use, giving rise to leaks.

Another type of seal-forming structure may comprise a friction-fit element, e.g. for insertion into a naris, however some patients find these uncomfortable.

Another form of seal-forming structure may use adhesive to achieve a seal. Some patients may find it inconvenient to constantly apply and remove an adhesive to their face.

A range of patient interface seal-forming structure technologies are disclosed in the following patent applications, assigned to <CIT>; <CIT>; <CIT>.

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 <CIT>.

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 <CIT> (describing amongst other things aspects of the ResMed Limited SWIFT™ nasal pillows), <CIT> (describing amongst other things aspects of the ResMed Limited SWIFT™ LT nasal pillows); International Patent Applications <CIT> and <CIT> (describing amongst other things aspects of the ResMed Limited MIRAGE LIBERTY™ full-face mask); International Patent Application <CIT> (describing amongst other things aspects of the ResMed Limited SWIFT™ FX nasal pillows).

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. <CIT>. 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.

A respiratory pressure therapy (RPT) device may be used to deliver one or more of a number of therapies described above, such as by generating a flow of air for delivery to an entrance 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 <NUM> in CPAP mode at <NUM> cmH<NUM>O).

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™ <NUM> 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.

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'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.

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 <NUM> of the patient <NUM>, e.g. through noise or focussed airflow.

ResMed Limited has developed a number of improved mask vent technologies. See International Patent Application Publication No. <CIT>; International Patent Application Publication No. <CIT>; <CIT>; US Patent Application Publication No. <CIT>; <CIT>.

Table of noise of prior masks (ISO <NUM>-<NUM>:<NUM>, <NUM> cmH<NUM>O pressure at <NUM>).

Sound pressure values of a variety of objects are listed below.

The patent document <CIT> is hereby acknowledged.

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 apparatus that improve the compliance of patients with respiratory therapy.

An aspect of the present technology includes a gas washout vent for a patient interface system, the gas washout vent comprising: a housing comprising a first wall with one or more passages through the first wall, the one or more passages being configured to provide fluid communication with a portion of the patient interface system that is configured to be exposed to the therapy pressure, the housing at least partially defining a second opening that is in communication with ambient atmosphere; and a diffusing material located at least partially within the housing.

An aspect of the present technology includes a gas washout vent for a patient interface system configured to maintain a therapy pressure in a range of about <NUM> cmH<NUM>O to about <NUM> cmH<NUM>O above ambient air pressure in use, throughout a patient's respiratory cycle, while the patient is sleeping, to ameliorate a respiratory or a sleep disordered breathing condition, the gas washout vent comprising: a housing comprising a first wall with one or more passages through the first wall, the one or more passages being configured to provide fluid communication with a portion of the patient interface system that is configured to be exposed to the therapy pressure, the passages including respective first openings on a first surface of the first wall, the housing at least partially defining a second opening that is in communication with ambient atmosphere; and a diffusing material located at least partially within the housing to be adjacent the first surface, a surface of the diffusing material facing the first surface being spaced away from the first surface by a gap that extends to provide a fluid communication between all of the first openings, as well as between all of the first openings and the second opening; wherein the housing is configured so that air is prevented from flowing out of the housing at all areas directly opposite each of the first openings.

In examples, (a) the housing further comprises a third opening in communication with ambient atmosphere, wherein the third opening does not overlap with an area of an outlet of any of the passages that is projected along a central axis of the respective passages, and is located so that at least part of the diffusing material is between each first opening and the third opening; (b) the third opening is oriented so that a central axis through the third opening is angled with respect to the central axis of any of the passages; (c) he third opening is sized so that completely blocking the third opening does not substantially decrease the air flow through the gas washout vent when the portion of the patient interface is exposed to the therapy pressure; (d) the air flow through the gas washout vent does not decrease by more than three percent; (e) the third opening is one of a plurality of third openings; (f) the third opening is configured for water removal; (g) the second opening comprises a plurality of second openings; (h) at least one of the one or more passages is sized so that at least a portion of air exiting the respective first opening penetrates into the diffusing material when the portion of the patient interface is exposed to the therapy pressure. ; (i) the gas washout vent is configured so that the portion of the air penetrating the diffusing material exits the diffusing material and re-enters the gap before flowing out of the second opening; (j) the gas washout vent is configured so that the portion of the air exiting the respective first opening penetrates and exits the diffusing material via the surface; (k) no more than <NUM> dB(A) noise is generated when air exits the second opening as a result of the portion of the patient interface being exposed to the therapy pressure; (<NUM>) the diffusing material comprises uncompressed fibers; (m) he diffusing material comprises moisture wicking material; (n) the moisture wicking material is sintered plastic; (o) the diffusing material comprises hydrophobic material; (p) the diffusing material possesses antibacterial properties; (q) the first wall is fixed in the housing in a non-releasable manner; (r) the gap is at least partially bounded by the first wall from the first openings to the second opening; (s) the gap is formed by the surface from a location opposed to the first openings to a portion of the diffusing material that is closest to the second opening; (t) the gap is tapered in a radial direction; (u) the gap tapers off in a radially outward direction; (v) the surface of the diffusing material and the first surface are parallel; (x) the surface of the diffusing material and the first surface are inclined with respect to one another; (z) a portion of the housing is removable to allow replacement of the diffusing material; (aa) the second opening and the gap are sized so that a majority of pressure drop during the flow of air through the passages, the gap and the second opening, occurs prior to exiting the passages; and/or (bb) he gas washout vent comprises a separate apparatus arranged for engaging with a patient interface or an air circuit.

Another aspect of the present technology includes a system for treating a respiratory disorder in a patient that comprises a respiratory pressure therapy device; a humidifier; an air circuit; and a patient interface, and at least one of the air circuit and the patient interface comprises the gas washout vent according to any preceding aspect or example.

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.

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 <NUM> for supplying pressurised air to the patient <NUM> via an air circuit <NUM> to a patient interface <NUM>.

A non-invasive patient interface <NUM> in accordance with one aspect of the present technology comprises the following functional aspects: a seal-forming structure <NUM>, a plenum chamber <NUM>, a positioning and stabilising structure <NUM>, a vent <NUM>, one form of connection port <NUM> for connection to air circuit <NUM>, and a forehead support <NUM>. 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 <NUM> 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 <NUM> 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 <NUM> cmH<NUM>O with respect to ambient.

In one form of the present technology, a seal-forming structure <NUM> 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 <NUM> 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's face.

In one form the target seal-forming region is located on an outside surface of the seal-forming structure <NUM>.

In certain forms of the present technology, the seal-forming structure <NUM> is constructed from a biocompatible material, e.g. silicone rubber.

A seal-forming structure <NUM> in accordance with the present technology may be constructed from a soft, flexible, resilient material such as silicone.

In certain forms of the present technology, a system is provided comprising more than one a seal-forming structure <NUM>, 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 <NUM> 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.

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 <NUM> 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 <NUM> comprises a sealing flange and a support flange. The sealing flange comprises a relatively thin member with a thickness of less than about <NUM>, for example about <NUM> to about <NUM>, which extends around the perimeter of the plenum chamber <NUM>. 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 <NUM>, and extends at least part of the way around the perimeter. The support flange is or includes a springlike element and functions to support the sealing flange from buckling in use.

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.

In one form, the non-invasive patient interface <NUM> 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'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's face.

In one form, the non-invasive patient interface <NUM> comprises a seal-forming structure that forms a seal in use on an upper lip region (that is, the lip superior) of the patient'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's face.

In one form the non-invasive patient interface <NUM> comprises a seal-forming structure that forms a seal in use on a chin-region of the patient'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's face.

In one form, the seal-forming structure that forms a seal in use on a forehead region of the patient's face. In such a form, the plenum chamber may cover the eyes in use.

In one form the seal-forming structure of the non-invasive patient interface <NUM> 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'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.

The plenum chamber <NUM> 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 <NUM> is positioned in close proximity to an adjacent surface of the face. Actual contact with the face is provided by the seal-forming structure <NUM>. The seal-forming structure <NUM> may extend in use about the entire perimeter of the plenum chamber <NUM>. In some forms, the plenum chamber <NUM> and the seal-forming structure <NUM> are formed from a single homogeneous piece of material.

In certain forms of the present technology, the plenum chamber <NUM> does not cover the eyes of the patient in use. In other words, the eyes are outside the pressurised volume defined by the plenum chamber. Such forms tend to be less obtrusive and / or more comfortable for the wearer, which can improve compliance with therapy.

In certain forms of the present technology, the plenum chamber <NUM> is 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 <NUM> 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 seal-forming structure <NUM> of the patient interface <NUM> of the present technology may be held in sealing position in use by the positioning and stabilising structure <NUM>.

In one form the positioning and stabilising structure <NUM> provides a retention force at least sufficient to overcome the effect of the positive pressure in the plenum chamber <NUM> to lift off the face.

In one form the positioning and stabilising structure <NUM> provides a retention force to overcome the effect of the gravitational force on the patient interface <NUM>.

In one form the positioning and stabilising structure <NUM> provides a retention force as a safety margin to overcome the potential effect of disrupting forces on the patient interface <NUM>, such as from tube drag, or accidental interference with the patient interface.

In one form of the present technology, a positioning and stabilising structure <NUM> 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 <NUM> 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 <NUM> comprises at least one strap having a rectangular cross-section. In one example the positioning and stabilising structure <NUM> comprises at least one flat strap.

In one form of the present technology, a positioning and stabilising structure <NUM> 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's head on a pillow.

In one form of the present technology, a positioning and stabilising structure <NUM> 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's head on a pillow.

In one form of the present technology, a positioning and stabilising structure <NUM> is provided with a decoupling portion located between an anterior portion of the positioning and stabilising structure <NUM>, and a posterior portion of the positioning and stabilising structure <NUM>. 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 <NUM> and disrupting the seal.

In one form of the present technology, a positioning and stabilising structure <NUM> 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 <NUM> 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'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's head and overlays a portion of the 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's head and overlays or lies inferior to the occipital bone of the patient'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 <NUM> 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 <NUM> 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 <NUM>, 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 <NUM> 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.

In one form, the patient interface <NUM> includes a vent <NUM> constructed and arranged to allow for the washout of exhaled gases, e.g. carbon dioxide.

In certain forms the vent <NUM> is configured to allow a continuous vent flow from an interior of the plenum chamber <NUM> to ambient whilst the pressure within the plenum chamber is positive with respect to ambient. The vent <NUM> is configured such that the vent flow rate has a magnitude sufficient to reduce rebreathing of exhaled CO<NUM> by the patient while maintaining the therapeutic pressure in the plenum chamber in use.

The vent <NUM> may take various forms. In one form, vent <NUM>, in accordance with the present technology, comprises a plurality of holes, for example, about <NUM> to about <NUM> holes, or about <NUM> to about <NUM> holes, or about <NUM> to about <NUM> holes. The size of each hole may be between <NUM> and <NUM>, preferably between <NUM> and <NUM> and more preferably between <NUM> and <NUM>. Whilst the holes are usually formed with circular openings, other shapes are also possible. A number of smaller holes may be replaced by one or more larger holes. Some of the larger holes may have the form of slits.

The vent <NUM> may be located on and integrated within the plenum chamber <NUM> or within the elbow <NUM>. Alternatively, the vent <NUM> may be formed separately as a decoupling structure, e.g., a swivel, that can be located as part of the air circuit <NUM> or between the air circuit <NUM> and the plenum chamber <NUM>.

<FIG> illustrates an implementation of a vent <NUM> (e.g., a gas washout vent). <FIG> is a cross-section through passages <NUM>, a wall <NUM>, a diffusing material <NUM>, and a housing <NUM>, each of which are around a central air passage <NUM>. The air passage <NUM> may be part of an inlet to the plenum chamber <NUM> (e.g., part of a decoupling structure) or may be part of the air circuit <NUM>. The illustrated cross-section includes some amount of symmetry about the central air passage <NUM>, but symmetry is not required.

The diffusing material <NUM> is spaced away from the wall <NUM> by a gap <NUM> and thus provides a passage with uninterrupted fluid communication between the passages <NUM> and an opening <NUM>. This is provided by locating the diffusing material at least partially in the housing so that a surface <NUM> of the diffusing material <NUM> faces the surface of openings <NUM>. The surface <NUM> of the diffusing material is a substantially planar surface and is spaced away from the surface of openings <NUM> by the gap <NUM>. The configuration is such that the gap extends to provide fluid communication between all of the openings <NUM>, as well as between all of the openings <NUM> and the opening <NUM>.

The opening <NUM> provides communication with ambient atmosphere. The size of the gap should be such that it would allow any dust accumulated in the gap to be cleaned and any accumulated water to be dried out. Thus the gap <NUM> can be between <NUM> and <NUM> deep, preferably between <NUM> and <NUM> and even more preferably, about <NUM>. As it would be discussed later in the text, the arrangement is such that during the standard operation of the patient interface, at least some pressurised air exiting the passages <NUM> (for example, a jet or pressure wave) bridges the gap <NUM> and enters the diffusing material <NUM>. Once the airflow enters the diffusing material, the nature of the material forces the airflow onto a tortuous path. The air may enter the diffusing material <NUM>, even though a path of lower resistance exists via the gap <NUM>, if a jet of air, which may be at or approaching sonic velocity, imparts sufficient momentum on the air that at least some molecules enter the diffusing material.

The properties of the diffusing material <NUM>, such as thickness or density, as well as the size of openings <NUM>, are chosen so that the openings <NUM> have a negligible effect on the overall airflow. Also, a second wall <NUM> is directly opposite the passages <NUM> with respect to the diffusing material <NUM>. Thus the housing <NUM> is essentially closed for the airflow on that opposite side. Because of that, the airflow that enters the diffusing material <NUM> is forced to eventually return back into the gap <NUM> and out to the ambient air via the opening <NUM>. The tortuous path forced on the airflow by the above described configuration of the vent substantially reduces the jetting effect and/or noise generated by the jetting effect associated with the vent. Alternatively or additionally, because the diffusing material <NUM> defines at least one side of the gap <NUM>, any sound waves propagating through the gap will be able to expand into the diffusing material <NUM> and reduce the sound level, even if there is little or no net flow of air through the diffusing material <NUM> itself.

As illustrated, the gap <NUM> extends all along a surface <NUM> of the diffusing material <NUM> to the opening <NUM>, but the gap <NUM> need not extend along this entire length. For example, there could be no gap at a portion <NUM> (e.g., interior to a passage <NUM> closest to the air passage <NUM>, which is radially inward in the illustrated implementation). Other configurations of the gap <NUM> that provide an uninterrupted path from the passages <NUM> to the opening <NUM> may also be provided.

With the gap <NUM>, the performance characteristics of the vent <NUM> may be improved compared to a vent without the gap. For example, some materials suitable for the diffusing material <NUM> may be difficult to manufacture with consistent density and air permeability. This may cause an unwanted variation in the washout airflow through the vents of different patient interfaces. The introduction of the gap offers a permanent escape path and results in a more consistent and/or predictable washout flow. The gap offers a further advantage when the airflow through the diffusing material <NUM> is reduced or prevented for any reason, such as if the material <NUM> has become wet. In this case the gap <NUM> offers an escape path for the air to the ambient atmosphere.

The wall <NUM> separates the diffusing material <NUM> from an interior portion of the patient interface <NUM> that is exposed to therapy pressure during use. The passages <NUM> are illustrated as being through the wall <NUM> and include respective openings <NUM> adjacent to and facing toward the diffusing material <NUM>. The passages <NUM> may be any number and of any geometric configuration that provides the desired flow characteristics of the vent <NUM>. For example, the passages could be cylindrical passages, frusto-conical passages and/or any other three-dimensional shape (such as a slot) that provides desired performance characteristics of the vent <NUM>. Whilst in <FIG> the passages are of a frusto-conical shape with a tapered down opening oriented towards the diffused material, this does not have to be the case and the tapered down opening of the frusto-conical shape may be oriented in the opposite direction. Any or all of these configurations may provide fluid communication with an interior portion of the patient interface <NUM> that is configured to be exposed to the therapy pressure. A single passage <NUM> may be provided, or a plurality may be provided, but providing a plurality may reduce any audible sound generated. The passages <NUM> may be passive or part of a valve system (not shown) that regulates flow through the passage based on conditions such as therapy pressure. The openings <NUM> and/or the passages <NUM> are sized, and the openings <NUM> and the diffusing material <NUM> are oriented, so that air exiting the openings <NUM> may impinge on the diffusing material <NUM> at the surface <NUM> when an interior portion of the patient interface <NUM> is exposed to the therapy pressure. Air exiting the openings <NUM> may also impinge when the interior portion is exposed to pressures lower than the therapy pressure. With this configuration, at least a portion of air exiting an opening <NUM> may penetrate into the diffusing material <NUM> when the interior portion of the patient interface <NUM> is exposed to the therapy pressure, and then exit from the surface <NUM> before exiting the vent via the opening <NUM>. Any portion of air that penetrates the diffusing material <NUM> but that does not exit the surface <NUM> may exit the diffusing material <NUM> elsewhere due to leaks in the housing <NUM>. This flow configuration may result in the overall flow path for gas exiting the vent <NUM> being more tortious, and therefore more likely to dampen or eliminate noise generated. Air may impinge but not penetrate if the velocity is sufficiently low and the porosity of the surface <NUM> is such that surface effects prevent the air from penetrating. In this scenario, the diffusing material <NUM> may still provide reduction in the jetting effect, as well as a noise reduction by allowing sound waves to propagate into the diffusing material <NUM> and dissipate.

The diffusing material <NUM> may cause diffusion of air as the air passes through the material, which may absorb the energy and/or reduce the air velocity. Reducing the velocity of flow reduces the associated noise, which is often due to turbulence of flow or air jets colliding with hard surfaces. The diffusing material <NUM> may be fibrous material similar to that used in filter media (e.g., uncompressed fibres, such as polyester fibres) or open-celled foam. Any material that allows at least partial penetration by the air flow and that provides a tortious path for air flowing through the material may be used for the diffusing material <NUM>. The diffusing material can be a moisture wicking material such as sintered plastic. The diffusing material may also be hydrophobic and may be processed to have antibacterial properties. One or more of these configurations may aid with removal of moisture, which may be beneficial during cleaning.

The housing <NUM> may have any shape that facilitates the retention of the diffusing material <NUM> in place while also providing the desired flow characteristics of the vent <NUM>. The housing <NUM> is illustrated to include a wall configuration that prevents air from flowing out of the housing at all areas directly opposite each of the openings <NUM>. The housing <NUM> may include all of the structural components that surround the diffusing material <NUM> such as the wall <NUM> and the wall <NUM>. A center line <NUM> is illustrated along a central axis of each of the passages <NUM> and extends to the second wall <NUM>. If the passages are sufficiently long relative to inlet flow conditions, a fully developed flow will occur and the arrows <NUM> will be approximations of flow vectors through and exiting from the passages <NUM>. The chaotic nature of fluid flow may result in the actual flow diverging and dissipating as the flow moves away from the passages <NUM>. However a vector, e.g., a magnitude and direction, may be used to characterize the flow at a given point. If these vectors are extended they will eventually intersect a portion of the housing <NUM> that is devoid of openings. However, it is not only the flow vectors that generally extend along the central axes of the respective openings, which if extended in the direction of the flow will encounter a solid wall. If the cross-sectional area of each of the openings <NUM> is projected along the respective center line <NUM>, the image of the area will be projected over a solid portion of the wall <NUM> instead of an opening in the wall <NUM>. Thus no opening (e.g., the second opening <NUM>) in the housing <NUM>, or vent <NUM>, is in-line with an exit vector or overlaps with a projected area from any of the passages <NUM> and air exiting the passages <NUM> cannot exit the vent <NUM> from a portion of the second wall <NUM> that is directly opposite the passages <NUM>. Instead, the exit opening <NUM> extends in a direction that is at an angle with respect to the passage <NUM> flow vectors. The angle could be acute, but in some examples it is straight (e.g., a right angle to the exit vectors) or even obtuse. Such a configuration increases the likelihood that air exiting the passages <NUM> will follow a tortious path through the diffusing material <NUM> to exit the vent <NUM> through openings <NUM>. As was mentioned before, the exit opening <NUM> may be defined by one or more of the following: walls of the housing <NUM>, a surface of the diffusing material or a surface of another component. The exit opening <NUM> could be oriented in any direction, as long as it releases the air into the ambient environment along a path that does not pass through the diffusing material <NUM>. In one alternative example, the flow out of the exit opening <NUM> can be parallel to, but offset from, the arrows <NUM>.

As illustrated, the housing <NUM> partly bounds the opening <NUM> and the wall <NUM> also partly bounds the opening <NUM>, but the opening <NUM> can be bounded completely by the housing <NUM> or not bounded at all by the housing <NUM>. In the latter case, the opening <NUM> can, for example, be defined by a component other than the housing <NUM>. Any configuration and location of the opening <NUM> that provides the appropriate flow path, including the gap <NUM>, may be utilized. As illustrated, the opening <NUM> is an annular gap all around the periphery of the vent <NUM>, but the opening <NUM> may be any number of openings. For example, it may be desirable to divide the opening <NUM> into a plurality of openings to increase the stability of the resultant openings. As illustrated, the opening <NUM> may be described as a direct exit to ambient, but the opening <NUM> could be a less direct, or more tortious, path to ambient. For example, there could be additional structural elements that result in the flow path including one or more turns before exiting to ambient. Also, the opening <NUM> could be at a different orientation with respect to the gap <NUM> or wall <NUM> than illustrated. As illustrated the flow path through the opening <NUM> is substantially a right angle to the passages <NUM> and/or arrows <NUM>, but the opening may be at other angles or orientations. For example, the flow path through the opening could be at an obtuse or acute angle to the passages <NUM> or could be parallel to and offset from the passages <NUM>.

The housing <NUM> may also include openings <NUM> that are not in-line with the passages <NUM>. The openings <NUM> are illustrated with a center line <NUM> on the central axis of the openings <NUM> to visually clarify the orientation of the openings <NUM>. The center lines <NUM> of the passages <NUM> are not aligned with the center lines <NUM> of the openings <NUM>. The openings <NUM> may be optionally included (zero, one or more may be included) to allow for water removal after cleaning the vent <NUM>. The openings <NUM> may allow water to be shaken out of the vent <NUM> and/or allow greater opportunity for water to evaporate and exit the vent <NUM>, where both shaking and evaporation contribute to drying the vent <NUM>. If the openings <NUM> are included, they are preferably located and sized so that, in conjunction with the diffusing material <NUM>, opening <NUM> and gap <NUM>, substantially no air exits the openings <NUM> when therapy pressure is applied to the patient interface <NUM>. In order to determine flow out of the openings <NUM>, pressure may be applied to the patient interface <NUM> and the flow rate through the vent <NUM> is measured. Then, the openings <NUM> may be completely blocked and the flow rate re-measured. If the flow rate decreases by less than a predetermined percentage, then there is substantially no decrease in air flow through the vent <NUM>. Preferably, the flow rate decreases by no more than <NUM>%, and more preferably the flow rate decreases by no more than <NUM>%. In fact, blocking the openings <NUM> may cause no change in the flow rate through the vent <NUM>. By designing the vent <NUM> so that completely blocking the openings <NUM> results in substantially no change in flow through the vent <NUM>, the vent <NUM> should provide sufficient gas-washout even if the diffusing material <NUM> becomes completely clogged, which could occur due to water or mucous build-up.

The openings <NUM> may be formed in an area adjacent the side of the diffusing material <NUM> that is opposite to the side facing the openings <NUM>. However, the size and the location of the openings <NUM> can vary. The openings <NUM> may have at least two purposes - to allow the vent to be washed and dried. First, the openings <NUM> may allow the diffusing material <NUM> to be washed by a user by way of placing the entire vent <NUM> under water from a faucet. For washing to be effective, the openings <NUM> are preferably sufficiently large to allow liquid water (e.g., droplets) to enter the housing. Second, the openings <NUM> may allow, after a wash or after an inadvertent accumulation of liquid (e.g., mucous, water, etc.) during use of the vent, for the removal of the accumulated liquid. The size of each single opening <NUM> is related to the ability to allow liquid such as water to move in and out of the event. The combined size of all of the openings may determine how efficiently the vent is washed and dried. A combined area of between <NUM><NUM> and <NUM><NUM> is believed to be able to allow adequate washing and drying. In some examples, the total opening areas is preferably between <NUM> and <NUM><NUM>, and even more preferably around <NUM><NUM>. The location of the openings may also be significant. It is preferable that openings <NUM> are spaced from and located, at least to an extent, opposite to the openings <NUM> with respect to the diffusing material <NUM>. This provides a water or liquid flow path between openings <NUM> and <NUM>, which improves the ability to clean and dry the diffusing material <NUM>. With at least the embodiment illustrated in <FIG>, water may be removed at least through the second opening <NUM> by shaking, or applying centripetal force to, the vent <NUM>.

The housing <NUM> may hold the diffusing material <NUM> is place by any suitable method. For example, the housing <NUM> and diffusing material <NUM> may be bonded together (e.g., glued or melted together) or mechanically fastened (e.g., friction, interference, detent, etc.).

The housing <NUM> may be a single integral piece or multiple pieces or multiple pieces joined together into a single piece. The wall <NUM> may be permanently joined to, or integrally formed with, the housing <NUM>. The housing may be attached to the vent <NUM> in a non-releasable manner, which is attachment that is not intended to be detached without breaking. Non-releasable attachment may include glue, ultrasonic welding, melting with a hot iron, one-time snap fit (e.g., snap fit that is designed to break upon separation), originally formed as one piece, etc. If the housing <NUM> is formed such that the housing <NUM> and/or the diffusing material <NUM> cannot be removed, some benefits may be achieved. For example, if the housing <NUM> and/or the diffusing material <NUM> cannot be removed, incorrect user installation or inadvertent detachment of the vent can be avoided.

<FIG> illustrates another configuration of the vent <NUM>. The descriptions associated with the reference numbers of <FIG> are also applicable here, and thus not repeated. This configuration of the vent <NUM> is similar to that illustrated in <FIG> except that the air passage <NUM> is omitted. Thus the gap <NUM> extends from one side of the vent <NUM> to the other.

<FIG> illustrates another configuration of the vent <NUM>. The descriptions associated with the reference numbers of <FIG> are also applicable here, and thus not repeated. Here, the air passage <NUM> is omitted and instead a member <NUM> is illustrated, which may secure the diffusing material <NUM> and/or housing <NUM>.

<FIG> illustrates another configuration of the vent <NUM>. The descriptions associated with the reference numbers of <FIG> are also applicable here, and thus not repeated. This figure differs from <FIG> in that the locations of the openings <NUM> are different. This figure also illustrates that the opening <NUM> may be a continuous opening all around a periphery of the vent <NUM>. The openings <NUM> may also be continuous, however are preferably discontinuous from each other and/or from the opening <NUM>.

<FIG> illustrates another configuration of the vent <NUM>. The descriptions associated with the reference numbers of <FIG> are also applicable here, and thus not repeated. In this configuration, the passages <NUM> are in communication with and arrayed around the air passage <NUM>, resulting in the vent <NUM> having an overall annular configuration compared to the planar configuration of <FIG>. In other words, the passages <NUM> in <FIG> are in one planar or near-planar wall <NUM>, whereas the wall <NUM> in <FIG> is cylindrical and the gas exiting the vent <NUM> exits along the cylinder axis indicated with an interrupted line.

<FIG> illustrates another configuration of the vent <NUM>. The descriptions associated with the reference numbers of <FIG> are also applicable here, and thus not repeated. <FIG> is similar to <FIG> except that opening <NUM> is provided at two ends of the diffusing material <NUM> in <FIG>, but only at one end in <FIG>.

In each of <FIG>, the arrows illustrated through the diffusing material <NUM> are conceptual illustrations of air flow through the diffusing material <NUM> and may not be representative of actual air flow through the diffusing material <NUM>. In general, each of these arrows shows the concept of air exiting the passages <NUM>, entering the diffusing material <NUM> via the surface <NUM>, exiting the diffusing material via the surface <NUM>, flowing through the gap <NUM> and then to ambient via the opening <NUM>.

<FIG> illustrate another configuration of the vent <NUM>. The descriptions associated with the reference numbers of <FIG> are also applicable here, and thus not repeated except as noted. <FIG> illustrates an example of the vent <NUM> in a perspective view, where the vent <NUM> is an insertable and/or removable assembly. <FIG> is a top view where a top cover <NUM> has been omitted so that the interior structure is visible. <FIG> is a cross-sectional view of <FIG>, but with the top cover included. This configuration of the vent <NUM> is similar to that illustrated in <FIG> in that the air passage <NUM> is omitted (but could be included if desired). As best seen in <FIG>, a support <NUM> contacts the surface <NUM> to support the diffusing material <NUM>. As illustrated in <FIG> and <FIG>, the support <NUM> is illustrated as a contiguous wall that bisects the gap <NUM>, extending uninterrupted from one side to another. However, the support <NUM> need not be contiguous and could be a formed by one or more non-contiguous supports (one or more gaps could be provided in the support <NUM>).

Another difference is the position of the openings <NUM>. Instead of being substantially in line with the gap <NUM>, the openings <NUM> are offset in a direction away from the surface that includes openings <NUM>, resulting in a second portion 3412A of the gap <NUM> around a periphery of the diffusing material <NUM>. With this arrangement, the air can flow into the surface <NUM> and out of a lateral surface <NUM> of the diffusing material <NUM> before flowing out through the openings <NUM>. The air can also flow through the gap <NUM> and the second portion 3412A without passing through the diffusing material <NUM>. With the chaotic and unpredictable nature of the flow of individual molecules, the actual air flow may be a combination of both flow paths. However, by providing both flow paths, the vent <NUM> may provide adequate flow even if the diffusing material <NUM> becomes clogged.

<FIG> and <FIG> illustrate a groove <NUM> around a perimeter of the vent <NUM>. Such a groove may allow for the vent <NUM> to be retained in a mating hole, preferably in a replaceable manner. If, for example, the hole is made in a relatively flexible material such as silicone, the vent <NUM> may be readily removed so that actions such as cleaning or replacement can be performed in a simple manner.

<FIG> and <FIG> illustrate aspects similar to <FIG> but with the addition of a deflector <NUM>. In <FIG>, the deflector <NUM> is illustrated as a solid, flat obstruction that prevents air flowing straight through the diffusing material <NUM> to the wall <NUM> (e.g., out an opposite side from the surface <NUM>). In <FIG>, the deflector <NUM> is curved in a manner that may generate a more smooth transition out of the sides of the diffusing material <NUM> than the flat deflector illustrated in <FIG>. Although multiple pieces of the deflector <NUM> are illustrated in <FIG>, any number of pieces, including a single piece, may be utilized as necessary for achieving desired flow characteristics. For both versions of the deflector <NUM>, any suitable method for producing the deflector <NUM> within the diffusing material <NUM> may be used. For example, an appropriately shaped cut in the side of the diffusing material <NUM> may allow for insertion of the deflector <NUM>. Alternatively, the diffusing material <NUM> may be made from multiple pieces that are then joined around the diffusing material <NUM>.

In one aspect, the diffusing material <NUM> may be removable. For example, if the cover <NUM> is attached in a releasable manner, the diffusing material <NUM> may be retained through mechanical retention by way of the cover <NUM>. If the cover <NUM> is removed, the diffusing material <NUM> could also be removed. However, the diffusing material <NUM> may not be removable in another aspect. For example, if the cover <NUM> is attached to the vent <NUM> such that the cover can only be removed by damage to the vent <NUM>, the diffusing material <NUM> may be considered not removable. Alternatively, the diffusing material <NUM> could be attached within the vent <NUM> in a permanent manner, such as by adhesive, so that the diffusing material <NUM> would be damaged during removal. Even if the cover <NUM> is removable without causing damage, the diffusing material <NUM> could be fixed in a manner that would damage or destroy the diffusing material <NUM>, thus making the diffusing material <NUM> not removable.

Although a boundary of the diffusing material <NUM> is described as a surface <NUM>, it may be different from a surface as of a solid body. The diffusing material <NUM> may have many openings or gaps to allow tortious flow through the diffusing material. Thus the surface <NUM> may also be considered a boundary of the diffusing material <NUM>.

The vent <NUM> may produce relatively low volume of noise or suppress noise generated before the sound waves propagate to a user. Preferably, the sound generated is less than <NUM> dB(A). For example, the sound may be <NUM> - <NUM> dB(A), <NUM> - <NUM> dB(A), or about <NUM> dB(A). These sound levels may be sufficiently low that neither the user nor a bed partner is disturbed.

In one form the patient interface <NUM> includes at least one decoupling structure, for example, a swivel or a ball and socket.

Connection port <NUM> allows for connection to the air circuit <NUM>.

In one form, the patient interface <NUM> includes a forehead support <NUM>.

In one form, the patient interface <NUM> includes an anti-asphyxia valve.

In one form of the present technology, a patient interface <NUM> includes one or more ports that allow access to the volume within the plenum chamber <NUM>. 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 <NUM>, such as the pressure.

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'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<NUM>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'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 <NUM>.

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<NUM>O, g-f/cm<NUM> and hectopascal. <NUM> cmH<NUM>O is equal to <NUM>-f/cm<NUM> and is approximately <NUM> hectopascal. In this specification, unless otherwise stated, pressure is given in units of cmH<NUM>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.

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 <NUM> to about <NUM> as measured using ASTM D2240.

Polycarbonate: a thermoplastic polymer of Bisphenol-A Carbonate.

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's Modulus, or an indentation hardness scale measured on a standardised sample size).

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 <NUM> 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's airways, e.g. at a load of approximately <NUM> to <NUM> cmH<NUM>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.

Apnea: According to some definitions, an apnea is said to have occurred when flow falls below a predetermined threshold for a duration, e.g. <NUM> 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'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:.

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:.

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 (<NUM>) being patent, and a value of zero (<NUM>), 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'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.

(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'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.

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'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) = <NUM> when Φ = <NUM>, 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's efforts.

Typical recent ventilation: The typical recent ventilation Vtyp is the value around which recent measures of ventilation over some predetermined timescale tend to cluster. For example, a measure of the central tendency of the measures of ventilation over recent history may be a suitable value of a typical recent ventilation.

Ala: the external outer wall or "wing" of each nostril (plural: alar).

Alare: The most lateral point on the nasal ala.

Alar curvature (or alar crest) point The most posterior point in the curved base line of each ala, found in the crease formed by the union of the ala with the cheek.

Auricle: The whole external visible part of the ear.

(nose) Bony framework: The bony framework of the nose comprises the nasal bones, the frontal process of the maxillae and the nasal part of the frontal bone.

(nose) Cartilaginous framework The cartilaginous framework of the nose comprises the septal, lateral, major and minor cartilages.

Columella: the strip of skin that separates the nares and which runs from the pronasale to the upper lip.

Columella angle: The angle between the line drawn through the midpoint of the nostril aperture and a line drawn perpendicular to the Frankfort horizontal while intersecting subnasale.

Frankfort horizontal plane: A line extending from the most inferior point of the orbital margin to the left tragion. The tragion is the deepest point in the notch superior to the tragus of the auricle.

Glabella: Located on the soft tissue, the most prominent point in the midsagittal plane of the forehead.

Lateral nasal cartilage: A generally triangular plate of cartilage. Its superior margin is attached to the nasal bone and frontal process of the maxilla, and its inferior margin is connected to the greater alar cartilage.

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) dividing 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.

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.

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).

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<NUM> 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 <NUM> degrees. In another form, the angle may be more, or less than <NUM> 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 <NUM> 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.

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's face for delivery of respiratory therapy. Some ties are formed of a soft, flexible, elastic material such as a laminated composite of foam and fabric.

Membrane: Membrane will be taken to mean a typically thin element that has, preferably, substantially no resistance to bending, but has resistance to being stretched.

Plenum chamber: a mask plenum chamber will be taken to mean a portion of a patient interface having walls at least partially enclosing a volume of space, the volume having air therein pressurised above atmospheric pressure in use. A shell may form part of the walls of a mask plenum chamber.

Seal: May be a noun form ("a seal") which refers to a structure, or a verb form ("to seal") which refers to the effect. Two elements may be constructed and/or arranged to 'seal' or to effect 'sealing' therebetween without requiring a separate 'seal' element per se.

Shell: A shell will be taken to mean a curved, relatively thin structure having bending, tensile and compressive stiffness. For example, a curved structural wall of a mask may be a shell. In some forms, a shell may be faceted. In some forms a shell may be airtight. In some forms a shell may not be airtight.

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 <NUM> degrees. In another form, the swivel may be constructed to rotate through an angle less than <NUM> 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 <NUM> litres per minute to about <NUM> litres per minute, depending on the mask design and treatment pressure.

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>, which illustrate examples of cross-sections at point p on a surface, and the resulting plane curves. <FIG> 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.

The curvature of a plane curve at p may be described as having a sign (e.g. positive, negative) and a magnitude (e.g. <NUM>/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> (relatively large positive curvature compared to <FIG> (relatively small positive curvature compared to <FIG>). 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).

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> (relatively small negative curvature compared to <FIG> (relatively large negative curvature compared to <FIG>). Such curves are often referred to as convex.

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 <FIG> 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>, the maximum curvature occurs in <FIG>, and the minimum occurs in <FIG>, hence <FIG> 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(<NUM>) to f(<NUM>) 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(<NUM>) to f(<NUM>), 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'.

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>. A typical human right ear comprises a helix, which is a right-hand helix, see <FIG> 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>), or alternatively by a left-hand rule (<FIG>).

Osculating plane: The plane containing the unit tangent vector and the unit principal normal vector.

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>, since T2>T1, the magnitude of the torsion near the top coils of the helix of <FIG> is greater than the magnitude of the torsion of the bottom coils of the helix of <FIG>.

With reference to the right-hand rule of <FIG>, 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>). 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>), 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.

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>, 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> and the example cross-sections therethrough in <FIG>, 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>, bounded by a surface as shown.

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.

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 scope of the technology.

Claim 1:
A gas washout vent (<NUM>) for a patient interface system configured to maintain a therapy pressure in a range of about <NUM> cmH2O to about <NUM> cmH2O above ambient air pressure in use, throughout a patient's respiratory cycle, while the patient is sleeping, to ameliorate a respiratory or a sleep disordered breathing condition, the gas washout vent comprising:
a housing (<NUM>) comprising a first wall with one or more passages through the first wall, the one or more passages (<NUM>) being configured to provide fluid communication with a portion of the patient interface system that is configured to be exposed to the therapy pressure, the one or more passages each including a respective first opening on a first surface of the first wall, the housing at least partially defining a second opening that is in communication with ambient atmosphere; and
a diffusing material (<NUM>) located at least partially within the housing to be adjacent the first surface, wherein the diffusing material is spaced away from the first wall by a gap (<NUM>) that extends to provide fluid communication between all of the first openings, as well as between all of the first openings and the second opening,
wherein the housing is configured so that air is prevented from flowing out of the housing at all areas directly opposite each of the first openings,
characterized in that
the second opening is spaced away from the first surface in a direction perpendicular to the first surface,
wherein the diffusing material is a material allowing at least partial penetration by an air flow and providing a tortious path for the air flow,
wherein a surface of the diffusing material facing the first surface is spaced away from the first surface by a first portion of the gap,
wherein the gap comprises a second portion (3412A) around a periphery of the diffusing material, so that air can flow into the surface of the diffusing material facing the first surface and out of a lateral surface of the diffusing material before flowing out through the second opening, and
wherein air can also flow through the first portion of the gap and the second portion of the gap without passing through the diffusing material.