Air circuit with venting arrangement for patient interface

Abstract

A conduit is configured to convey pressurized breathable gas from an RPT device to a patient interface The conduit includes a first gas flow path configured to convey the pressurized breathable gas from the RPT device and a second gas flow path that is configured to convey gas washout from the patient interface.

Description

AIR CIRCUIT WITH VENTING ARRANGEMENT FOR PATIENT INTERFACE1 BACKGROUND OF THE TECHNOLOGY1.1 FIELD OF THE TECHNOLOGY

[0001] The present technology relates to one or more of the screening, diagnosis, monitoring, treatment, prevention and amelioration of respiratory-related disorders. The present technology also relates to medical devices or apparatus, and their use. 1.2 DESCRIPTION OF THE RELATED ART1.2.1 Human Respiratory System and its Disorders

[0002] The respiratory system of the body facilitates gas exchange. The nose and mouth form the entrance to the airways of a patient.

[0003] The airways include a series of branching tubes, which become narrower, shorter and more numerous as they penetrate deeper into the lung. The prime function of the lung is gas exchange, allowing oxygen to move from the inhaled air into the venous blood and carbon dioxide to move in the opposite direction. The trachea divides into right and left main bronchi, which further divide eventually into terminal bronchioles. The bronchi make up the conducting airways, and do not take part in gas exchange. Further divisions of the airways lead to the respiratory bronchioles, and eventually to the alveoli. The alveolated region of the lung is where the gas exchange takes place, and is referred to as the respiratory zone. See “ Respiratory Physiology’ ’ , by John B. West, Lippincott Williams & Wilkins, 9th edition published 2012.

[0004] A range of respiratory disorders exist. Certain disorders may be characterised by particular events, e.g. apneas, hypopneas, and hyperpneas.

[0005] Examples of respiratory disorders include Obstructive Sleep Apnea (OSA), Cheyne-Stokes Respiration (CSR), respiratory insufficiency, Obesity Hypoventilation Syndrome (OHS), Chronic Obstructive Pulmonary Disease (COPD), Neuromuscular Disease (NMD) and Chest wall disorders.

[0006] 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 tostop breathing for periods typically of 30 to 120 seconds in duration, sometimes 200 to 300 times per night. It often causes excessive daytime somnolence, and it may cause cardiovascular disease and brain damage. The syndrome is a common disorder, particularly in middle aged overweight males, although a person affected may have no awareness of the problem, e.g. see US Patent No. 4,944,310 (Sullivan).

[0007] 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, e.g. see US Patent No. 6,532,959 (Berthon- Jones).

[0008] Respiratory failure is an umbrella term for respiratory disorders in which the lungs are unable to inspire sufficient oxygen or exhale sufficient CO2 to meet the patient’s needs. Respiratory failure may encompass some or all of the following disorders.

[0009] A patient with respiratory insufficiency (a form of respiratory failure) may experience abnormal shortness of breath on exercise.

[0010] Obesity Hypoventilation 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.1.2.2 Therapies

[0015] Various respiratory therapies, such as Continuous Positive Airway Pressure (CPAP) therapy, Non-invasive ventilation (NIV), Invasive ventilation (IV), and High Flow Therapy (HFT) have been used to treat one or more of the above respiratory disorders.1.2.2.1 Respiratory pressure therapies

[0016] Respiratory pressure therapy is the application of a supply of air to an entrance to the airways at a controlled target pressure that is nominally positive with respect to atmosphere throughout the patient’s breathing cycle (in contrast to negative pressure therapies such as the tank ventilator or cuirass).

[0017] 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.

[0018] 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.1.2.3 Respiratory Therapy Systems

[0019] These respiratory therapies may be provided by a respiratory therapy system or device. Such systems and devices may also be used to screen, diagnose, or monitor a condition without treating it.

[0020] A respiratory therapy system may comprise a Respiratory Pressure Therapy Device (RPT device), an air circuit, a humidifier, a patient interface, an oxygen source, and data management.1.2.3.1 Patient Interface

[0021] 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 10 cmH20 relative to ambient pressure. For other forms of therapy, such as the delivery of oxygen, the patient interface may not include a seal sufficient to facilitate delivery to the airways of a supply of gas at a positive pressure of about 10 cmH20. For flow therapies suchas nasal HFT, the patient interface is configured to insufflate the nares but specifically to avoid a complete seal. One example of such a patient interface is a nasal cannula.

[0022] Certain 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] Certain masks may cause some patients a feeling of claustrophobia, unease and / or may feel overly obtrusive.

[0027] 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.

[0028] Consequently, some masks suffer from being obtrusive, aesthetically undesirable, costly, poorly fitting, difficult to use, and / or uncomfortable especially when worn for long 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, especially if the mask is to be worn during sleep.

[0029] CPAP therapy is highly effective to treat certain respiratory disorders, provided patients comply with therapy. If a mask is uncomfortable, or difficult to usea 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.

[0030] 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.

[0031] For these reasons, patient interfaces for delivery of CPAP during sleep form a distinct field.1.2.3.1.1 Seal-forming structure

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Certain seal-forming structures may be designed for mass manufacture such that one design is able to 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] A range of patient interface seal-forming structure technologies are disclosed in the following patent applications: WO 1998 / 004310; WO 2006 / 074513; WO 2010 / 135785.

[0040] 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 US Patent 4,782,832 (Trimble et al.), assigned to Puri tan -Bennett Corporation.

[0041] ResMed Inc. 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 describe examples ofnasal pillows masks: International Patent Application WO 2004 / 073778 (describing amongst other things aspects of the SWIFT™ nasal pillows mask), US Patent Application 2009 / 0044808 (describing amongst other things aspects of the SWIFT™ LT nasal pillows mask); International Patent Applications WO 2005 / 063328 and WO 2006 / 130903 (describing amongst other things aspects of the MIRAGE LIBERTY™ full-face mask); International Patent Application WO 2009 / 052560 (describing amongst other things aspects of the SWIFT™ FX nasal pillows mask). / .2.3.1.2 Positioning and Stabilising Structure

[0042] 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. Several factors may be considered when comparing different positioning and stabilising techniques. These include: how effective the technique is at maintaining the seal-forming structure in the desired position and in sealed engagement with the face during use of the patient interface; how comfortable the interface is for the patient; whether the patient feels intrusiveness and / or claustrophobia when wearing the patient interface; and aesthetic appeal.

[0043] 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.1.2.3.1.3 Pressurised Air Conduit

[0044] In one type of treatment system, a flow of pressurised air is provided to a patient interface through a conduit in an air circuit that fluidly connects to the patient interface at a location that is in front of the patient’s face when the patient interface is positioned on the patient’s face during use. The conduit may extend from the patient interface forwards away from the patient’s face. / .2.3.1.4 Pressurised Air Conduit used for Positioning / Stabilising the Seal- Forming Structure

[0045] Another type of treatment system comprises a patient interface in which a tube that delivers pressurised air to the patient’s airways also functions as part of the headgear to position and stabilise the seal-forming portion of the patient interface at the appropriate part of the patient’s face. This type of patient interface may be referred to as having “conduit headgear” or “headgear tubing”. Such patient interfacesallow the conduit in the air circuit providing the flow of pressurised air from a respiratory pressure therapy (RPT) device to connect to the patient interface in a position other than in front of the patient’s face. One example of such a treatment system is disclosed in US Patent Publication No. US 2007 / 0246043, the contents of which are incorporated herein by reference, in which the conduit connects to a tube in the patient interface through a port positioned in use on top of the patient’s head.

[0046] It is desirable for patient interfaces incorporating headgear tubing to be comfortable for a patient to wear over a prolonged duration when the patient is asleep, form an air-tight and stable seal with the patient’s face, while also able to fit a range of patient head shapes and sizes.1.2.3.2 Respiratory Pressure Therapy (RPT) Device

[0047] A respiratory pressure therapy (RPT) device may be used individually or as part of a system to deliver one or more of a number of therapies described above, such as by operating the device to generate a flow of air for delivery to an interface to the airways. The flow of air may be pressure-controlled (for respiratory pressure therapies) or flow-controlled (for flow therapies such as HFT). Thus RPT devices may also act as flow therapy devices. Examples of RPT devices include a CPAP device and a ventilator.

[0048] 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.

[0049] An example of the special requirements of certain RPT devices is acoustic noise.

[0050] Table of noise output levels of prior RPT devices (one specimen only, measured using test method specified in ISO 3744 in CPAP mode at 10 cmH20).

[0051] One known RPT device used for treating sleep disordered breathing is the S9 Sleep Therapy System, manufactured by ResMed Inc. 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 nondependent ventilation for a range of patients for treating a number of conditions such as but not limited to NMD, OHS and COPD.

[0052] The ResMed Elisee™ 150 ventilator and ResMed VS III™ ventilator may provide support for invasive and non-invasive dependent ventilation suitable for adult or paediatric patients for treating a number of conditions. These ventilators provide volumetric and barometric ventilation modes with a single or double limb circuit. RPT devices typically comprise a pressure generator, such as a motor-driven blower or a compressed gas reservoir, and are configured to supply a flow of air to the airway of a patient. In some cases, the flow of air may be supplied to the airway of the patient at positive pressure. The outlet of the RPT device is connected via an air circuit to a patient interface such as those described above.

[0053] 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.1.2.3.3 Air circuit

[0054] An air circuit is a conduit or a tube constructed and arranged to allow, in use, a flow of air to travel between two components of a respiratory therapy system such as the RPT device and the patient interface. In some cases, there may be separate limbs of the air circuit for inhalation and exhalation. In other cases, a single limb air circuit is used for both inhalation and exhalation.1.2.3.4 Humidifier

[0055] 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 interfaceioproduces 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.1.2.3.5 Vent technologies

[0056] 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.

[0057] The vent may comprise an orifice and gas may flow through the orifice in use of the mask. Many such vents are noisy. Others may become blocked in use and thus provide insufficient washout. Some vents may be disruptive of the sleep of a bed partner 1100 of the patient 1000, e.g. through noise or focussed airflow.

[0058] ResMed Inc. has developed a number of improved mask vent technologies, e.g. see International Patent Application Publication No. WO 1998 / 034665; International Patent Application Publication No. WO 2000 / 078381; US Patent No. 6,581,594; US Patent Application Publication No. US 2009 / 0050156; US Patent Application Publication No. 2009 / 0044808.

[0059] Table of noise of prior masks (ISO 17510-2:2007, 10 cmH20 pressure at Im)

[0060] (* one specimen only, measured using test method specified in ISO 3744 in CPAP mode at 10 cmH20)

[0061] Sound pressure values of a variety of objects are listed below2 BRIEF SUMMARY OF THE TECHNOLOGY

[0062] The present technology is directed towards providing medical devices used in the screening, diagnosis, monitoring, amelioration, treatment, or prevention of respiratory disorders having one or more of improved comfort, cost, efficacy, ease of use and manufacturability.

[0063] A first aspect of the present technology relates to apparatus used in the screening, diagnosis, monitoring, amelioration, treatment or prevention of a respiratory disorder.

[0064] Another aspect of the present technology relates to methods used in the screening, diagnosis, monitoring, amelioration, treatment or prevention of a respiratory disorder.

[0065] 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.

[0066] One form of the present technology comprises a positioning and stabilising structure configured to provide a force to hold the seal-forming structure in a therapeutically effective position on the patient’s head. The positioning and stabilising structure includes at least one strap.

[0067] One form of the present technology comprises a patient interface comprising a plenum chamber, a seal-forming structure, and a positioning and stabilising structure.

[0068] One form of the present technology comprises patient interface comprising a plenum chamber pressurisable to a therapeutic pressure of at least 4 cmH20 above ambient air pressure. The plenum chamber includes at least one plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient. The patient interface also comprises a seal-forming structure that is constructed and arranged to form a seal with a region of the patient’s face surrounding an entrance to the patient’s airways. The seal-forming structure has a hole therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient’s nares. The seal -forming structure is constructed and arranged to maintain said therapeutic pressure in the plenum chamber throughout the patient’s respiratory cycle in use. The patient interface also comprises a positioning and stabilising structure to provide a force to hold the seal-forming structure in a therapeutically effective position on the patient’s head.

[0069] Another aspect of one form of the present technology is a series of modular elements that may be interconnected in order to form different styles of patient interfaces.

[0070] In one form, there are at least two versions or styles of each modular element. The versions or styles may be interchangeably used with one another in order to form different modular assemblies.

[0071] One form of the present technology comprises a conduit configured to convey pressurized breathable gas from an RPT device to a patient interface, the conduit comprising: a first gas flow path configured to convey the pressurized breathable gas from the RPT device, the first gas flow path having a first length; and a second gas flow path that is configured to convey gas washout from the patient interface, the second gas flow path having a second length that is different from the first length.

[0072] The first and second gas flow paths are concentric, wherein the first gas flow path is located inside the second gas flow path, wherein the first length is greater than the second length or vice versa, wherein the first and second gas flow paths are side by side, wherein the first and second gas flow paths are separated by a semi-permeable membrane or wall that is permeable to moisture but is not permeable to carbon dioxide, wherein one or more spacers separate the semi-permeable membrane from an outer wall of the conduit, wherein the conduit comprises an opening on a radial wall that is in communication with the second gas flow path, the opening being positioned to direct gas washout flowing through the second gas flow path to vent to atmosphere through the radial wall of the conduit, wherein the second gas flow path is configured to freely move within the first gas flow path, or the second gas flow path is fixed in place relative to the first gas flow path,

[0073] The conduit may further include a first cuff at a first end of the conduit; and a second cuff at a second end of the conduit. The first cuff is configured to connect to an outlet of the RPT device and the second cuff is configured to connect to a patient interface connector or to an inlet of the patient interface. The conduit may further comprise an adaptor with a first end configured to connect to the first cuff, a second end configured to connect to an outlet of the RPT device, and a vent opening in a radial wall of the conduit between the first and second ends. The vent opening is pneumatically connected to the second gas flow path. The conduit may furthercomprising one or more heating wires configured to heat gas flowing through the conduit; and further comprising one or more sensing wires.

[0074] Another aspect of one form of the present technology is a conduit configured to convey pressurized breathable gas from an RPT device to a patient interface, the conduit comprising: an outer wall that encloses a first lumen configured to convey the pressurized breathable gas from the RPT device; and a venting tube located inside the first lumen and configured to convey gas washout from the patient interface, wherein the venting tube extends beyond the first lumen.

[0075] The venting tube may comprise a second lumen bound by a semi-permeable wall that is permeable to moisture but is not permeable to carbon dioxide, wherein the venting tube is configured to freely move within the first lumen, wherein the venting tube is fixed in place within the first lumen. The conduit further comprises a first cuff at a first end of the conduit; and a second cuff at a second end of the conduit, wherein the first cuff is configured to connect to an outlet of the RPT device and the second cuff is configured to connect to a patient interface connector or to an inlet of the patient interface.

[0076] The venting tube is configured to extend beyond the second cuff. The conduit further comprises one or more heating wires configured to heat gas flowing through the conduit; and further comprising one or more sensing wires, wherein the conduit is flexible and retractable, wherein the venting tube is movable relative to the outer wall of the conduit in an axial direction, wherein the venting tube is attached to the outer wall of the conduit by one or more arms.

[0077] Another aspect of one form of the present technology is an air delivery system comprising the conduit according to any of the aspects discussed above, and the RPT device, wherein the RPT device comprises a vent path configured to pneumatically connect the venting tube to atmosphere when the conduit is attached to the RPT device. The air delivery system further comprise a filter positioned to filter gas washout flowing through the vent path of the RPT device. The venting tube is axially movable relative to the outer wall of the conduit so that when the venting tube is in a first position relative to the outer wall of the conduit, the second lumen is blocked at the RPT device end so that gas washout cannot exit from the venting tube to the RPT device, wherein the venting tube is axially movable relative to the outer wall of the conduit so that when the venting tube is axially moved to a second position, gas washout is allowed to flow into the RPT device from the venting tube,wherein the venting tube is biased to the first position and is configured to be moved to the second position in response to a threshold pressure in the venting tube.

[0078] Another aspect of one form of the present technology is a conduit configured to convey pressurized breathable gas from an RPT device to a patient interface, the conduit comprising: a first gas flow path configured to convey the pressurized breathable gas from the RPT device; and a second gas flow path that is configured to convey gas washout from the patient interface, wherein the first gas flow path is inside the second gas flow path.

[0079] The first and second gas flow paths are concentric, wherein the first and second gas flow paths are separated by a semi-permeable membrane or wall that is permeable to moisture but is not permeable to carbon dioxide, wherein one or more spacers separate the semi-permeable membrane from an outer wall of the conduit, wherein the conduit comprises an opening on a radial wall that is in communication with the second gas flow path, the opening being positioned to direct gas washout flowing through the second gas flow path to vent to atmosphere through the radial wall of the conduit.

[0080] The conduit according to any of the aspects above further comprises: a first cuff at a first end of the conduit; and a second cuff at a second end of the conduit, wherein the first cuff is configured to connect to an outlet of the RPT device and the second cuff is configured to connect to a patient interface connector or to an inlet of the patient interface. The conduit further comprises an adaptor with a first end configured to connect to the first cuff, a second end configured to connect to an outlet of the RPT device, and a vent opening in a radial wall of the conduit between the first and second end, wherein the vent opening is pneumatically connected to the second gas flow path. The conduit further comprises one or more heating wires configured to heat gas flowing through the conduit; and further comprising one or more sensing wires.

[0081] Another aspect of one form of the present technology is a conduit configured to convey pressurized breathable gas from an RPT device to a patient interface, the conduit comprising: an outer wall that encloses a first lumen configured to convey gas washout from the patient interface; and a supply tube located inside the first lumen and configured to convey the pressurized breathable gas from the RPT device.

[0082] The supply tube comprises a second lumen bound by a semi-permeable wall that is permeable to moisture but is not permeable to carbon dioxide, wherein the supply tube is configured to freely move within the first lumen, wherein the supply tube is fixed in place within the first lumen. The conduit further comprises a first cuff at a first end of the conduit; and a second cuff at a second end of the conduit, wherein the first cuff is configured to connect to an outlet of the RPT device and the second cuff is configured to connect to a patient interface connector or to an inlet of the patient interface.

[0083] The conduit further comprises one or more heating wires configured to heat gas flowing through the conduit; and further comprising one or more sensing wires, wherein the conduit is flexible and retractable, wherein the supply tube is movable relative to the outer wall of the conduit in an axial direction, wherein the supply tube is attached to the outer wall of the conduit by one or more arms.

[0084] Another aspect of one form of the present technology is an air delivery system comprising a conduit according to any of the aspects discussed above; and the RPT device, wherein the RPT device comprises a vent path configured to convey gas washout from the conduit to atmosphere when the conduit is attached to the RPT device.

[0085] The air delivery system further comprises a filter positioned to filter gas washout flowing through the vent path of the RPT device, wherein the supply tube is axially movable relative to the outer wall of the conduit so that when the supply tube is in a first position relative to the outer wall of the conduit, the first lumen is blocked at the RPT device end so that gas washout cannot exit from the venting tube to the RPT device, wherein the supply tube is axially movable relative to the outer wall of the conduit so that when the supply tube is axially moved to a second position, gas washout is allowed to flow into the RPT device from the first lumen, wherein the supply tube is biased to the first position and is configured to be moved to the second position in response to a threshold pressure in the supply tube.

[0086] Another aspect of one form of the present technology is a connector configured to convey pressurized breathable gas from conduit to a patient interface and to convey gas washout from a patient interface to the conduit, the connector comprising: a first end configured to connect to an inlet of a patient interface; a second end configured to connect to an air delivery tube; a lumen extending from the first end to the second end, the lumen being configured to convey the pressurized gasfrom conduit to the patient interface; and a venting tube configured to convey gas washout from the patient interface to the conduit, wherein the venting tube extends beyond the lumen and through the first end, wherein the connector is in the form of an elbow.

[0087] Another aspect of one form of the present technology is a patient interface configured to deliver pressurized breathable gas to a patient’s airways, the patient interface comprising: a cushion configured to sealingly engage the patient’s face a plenum chamber; and a positioning and stabilizing structure comprising: one or more headgear straps; and one or more air delivery tubes attached to the one or more headgear straps and connected to an inlet of the plenum chamber, wherein the one or more air delivery tubes is configured to extend along a patient’s face, wherein each of the one or more air delivery tubes comprises an internal wall that forms a first lumen and a second lumen within the air delivery tube, wherein the first lumen is configured to convey the pressurized breathable gas to the plenum chamber, and wherein the second lumen is configured to convey gas washout from the plenum chamber, wherein the internal wall is permeable to moisture but not carbon dioxide.

[0088] Another aspect of one form of the present technology is a conduit configured to convey pressurized breathable gas from a first end to a second end and configured to convey gas washout from the second end to the first end.

[0089] Another aspect of one form of the present technology is a respiratory therapy device configured to measure a level of carbon dioxide in gas washout flowing through a conduit, the respiratory therapy device comprising: an RPT device configured to pressurize a flow of breathable gas; a conduit configured to convey the pressurized breathable gas to a patient interface and configured to convey gas washout from the patient interface to the RPT device; a sensor configured to measure an amount of carbon dioxide flowing through the conduit; and a controller configured to determine a condition of a patient based on the measured level of carbon dioxide in the gas washout, wherein the condition of the patient corresponds to a patient’s metabolism, and / or cardiac output, wherein the controller is configured to determine a volume of a dead space in the patient interface based on the measured amount of carbon dioxide, wherein the controller is configured to increase an amount of carbon dioxide in a patient interface in response to the measured amount of carbon dioxide.

[0090] Another aspect of one form of the present technology is a respiratory therapy device configured to deliver pressurized breathable gas to a patient’s airways,the respiratory therapy device comprising: an RPT device configured to pressurize a flow of breathable gas; a conduit configured to convey the pressurized breathable gas to a patient interface and configured to convey gas washout from the patient interface to the RPT device; a sensor configured to measure a characteristic of the gas washout received by the RPT device from the conduit; and a controller configured to adjust a flow rate and / or a pressure of the pressurized flow of breathable gas generated by the RPT device.

[0091] The characteristic of the gas washout is pressure and / or flow rate. The respiratory system further comprise the patient interface, wherein the patient interface is configured to receive the pressurized breathable gas from the conduit and is configured to discharge gas washout into the conduit.

[0092] Another aspect of one form of the present technology is a connector configured to convey pressurized breathable gas from conduit to a patient interface and to convey gas washout from a patient interface to the conduit, the connector comprising: a first portion attachable or attached to an inlet of a patient interface; and a second portion configured to connect to an air delivery tube, wherein the first portion comprises a plurality of vent openings and has a larger diameter than the second portion.

[0093] The connector further comprises a transition from the first portion to the second portion in the form of a shoulder, wherein the outer surface of the second portion is tapered so that the outer diameter of the second portion increases toward the first portion.

[0094] Another aspect of one form of the present technology is a patient interface assembly comprising: a patient interface configured to sealingly engage a patient’s face, the patient interface comprising an air inlet; the connector disclosed above; and a conduit comprising a cuff configured to be secured to the connector.

[0095] The cuff comprises a first portion with a first diameter and a second portion with a second diameter smaller than the first diameter, wherein the first portion is configured to occlude the vent openings in the connector when the cuff is secured to the connector, wherein the cuff further comprises a should that forms a transition from the first portion to the second portion, wherein the conduit further comprises a venting tube within the lumen of the conduit, the venting tube being configured to extend into the connector when the cuff of the conduit is secured to the connector.

[0096] Another aspect of one form of the present technology is a conduit configured to convey pressurized breathable gas from an RPT device to a patient interface, the conduit comprising: a first gas flow path configured to convey the pressurized breathable gas from the RPT device; a second gas flow path that is configured to convey gas washout from the patient interface; and a cuff configured to secure the conduit to the patient interface, the cuff comprising a first portion and a second portion that has a smaller diameter than the first portion.

[0097] The first gas flow path is inside the second gas flow path, wherein the diameter of the second gas flow path is equal to the inner diameter of the second portion of the cuff.

[0098] Another aspect of one form of the present technology is a patient interface that is moulded or otherwise constructed with a perimeter shape which is complementary to that of an intended wearer.

[0099] An aspect of one form of the present technology is a method of manufacturing apparatus.

[0100] Another aspect of one form of the present technology is a method of assembling a modular system comprising selecting a positioning and stabilising structure, and connecting the positioning and stabilising structure to either a first cushion or a second cushion.

[0101] An aspect of certain forms of the present technology is a medical device that is easy to use, e.g. by a person who does not have medical training, by a person who has limited dexterity, vision or by a person with limited experience in using this type of medical device.

[0102] An aspect of one form of the present technology is a portable RPT device that may be carried by a person, e.g., around the home of the person.

[0103] An aspect of one form of the present technology is a patient interface that may be washed in a home of a patient, e.g., in soapy water, without requiring specialised cleaning equipment. An aspect of one form of the present technology is a humidifier tank that may be washed in a home of a patient, e.g., in soapy water, without requiring specialised cleaning equipment.

[0104] The methods, systems, devices and apparatus described may be implemented so as to improve the functionality of a processor, such as a processor of a specific purpose computer, respiratory monitor and / or a respiratory therapy apparatus. Moreover, the described methods, systems, devices and apparatus canprovide improvements in the technological field of automated management, monitoring and / or treatment of respiratory conditions, including, for example, sleep disordered breathing.

[0105] Of course, portions of the aspects may form sub -aspects of the present technology. Also, various ones of the sub-aspects and / or aspects may be combined in various manners and also constitute additional aspects or sub-aspects of the present technology.

[0106] Other features of the technology will be apparent from consideration of the information contained in the following detailed description, abstract, drawings and claims.3 BRIEF DESCRIPTION OF THE DRAWINGS

[0107] The present technology is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements including:3.1 RESPIRATORY THERAPY SYSTEMS

[0108] Fig. 1 A shows a system including a patient 1000 wearing a patient interface 3000, in the form of nasal pillows, receiving a supply of air at positive pressure from an RPT device 4000. Air from the RPT device 4000 is humidified in a humidifier 5000, and passes along an air circuit 4170 to the patient 1000. A bed partner 1100 is also shown. The patient is sleeping in a supine sleeping position.

[0109] Fig. IB shows a system including a patient 1000 wearing a patient interface 3000, in the form of a nasal mask, receiving a supply of air at positive pressure from an RPT device 4000. Air from the RPT device is humidified in a humidifier 5000, and passes along an air circuit 4170 to the patient 1000.

[0110] Fig. 1C shows a system including a patient 1000 wearing a patient interface 3000, in the form of a full -face mask, receiving a supply of air at positive pressure from an RPT device 4000. Air from the RPT device is humidified in a humidifier 5000, and passes along an air circuit 4170 to the patient 1000. The patient is sleeping in a side sleeping position.3.2 RESPIRATORY SYSTEM AND FACIAL ANATOMY

[0111] Fig. 2 A shows an overview of a human respiratory system including the nasal and oral cavities, the larynx, vocal folds, oesophagus, trachea, bronchus, lung, alveolar sacs, heart and diaphragm.

[0112] Fig. 2B shows a view of a human upper airway including the nasal cavity, nasal bone, lateral nasal cartilage, greater alar cartilage, nostril, lip superior, lip inferior, larynx, hard palate, soft palate, oropharynx, tongue, epiglottis, vocal folds, oesophagus and trachea.

[0113] Fig. 2C is a front view of a face with several features of surface anatomy identified including the lip superior, upper vermilion, lower vermilion, lip inferior, mouth width, endocanthion, a nasal ala, nasolabial sulcus and cheilion. Also indicated are the directions superior, inferior, radially inward and radially outward.

[0114] Fig. 2D is a side view of a head with several features of surface anatomy identified including glabella, sellion, pronasale, subnasale, lip superior, lip inferior, supramenton, nasal ridge, alar crest point, otobasion superior and otobasion inferior. Also indicated are the directions superior & inferior, and anterior & posterior.

[0115] Fig. 2E is a further side view of a head. The approximate locations of the Frankfort horizontal and nasolabial angle are indicated. The coronal plane is also indicated.

[0116] Fig. 2F shows a base view of a nose with several features identified including naso-labial sulcus, lip inferior, upper Vermilion, naris, subnasale, columella, pronasale, the major axis of a naris and the midsagittal plane.

[0117] Fig. 2G shows a side view of the superficial features of a nose.

[0118] Fig. 2H shows subcutaneal structures of the nose, including lateral cartilage, septum cartilage, greater alar cartilage, lesser alar cartilage, sesamoid cartilage, nasal bone, epidermis, adipose tissue, frontal process of the maxilla and fibrofatty tissue.

[0119] Fig. 21 shows a medial dissection of a nose, approximately several millimeters from the midsagittal plane, amongst other things showing the septum cartilage and medial crus of greater alar cartilage.

[0120] Fig. 2 J shows a front view of the bones of a skull including the frontal, nasal and zygomatic bones. Nasal concha are indicated, as are the maxilla, and mandible.

[0121] Fig. 2K shows a lateral view of a skull with the outline of the surface of a head, as well as several muscles. The following bones are shown: frontal, sphenoid, nasal, zygomatic, maxilla, mandible, parietal, temporal and occipital. The mental protuberance is indicated. The following muscles are shown: digastricus, masseter, sternocleidomastoid and trapezius.

[0122] Fig. 2L shows an anterolateral view of a nose.3.3 PATIENT INTERFACE

[0123] Fig. 3A shows a patient interface in the form of a nasal mask in accordance with one form of the present technology.

[0124] Fig. 3B shows a patient interface in the form of a nasal mask in accordance with another form of the present technology.

[0125] Fig. 3C shows a patient interface in the form of a nasal mask in accordance with another form of the present technology.

[0126] Fig. 3D shows a patient interface in the form of a nasal mask in accordance with another form of the present technology.

[0127] Fig. 3E shows a perspective view of a cushion of a patient interface configured to be worn by a patient and convey pressurized air to the patient’s nose and the patient’s mouth.

[0128] Fig. 3F shows a perspective view of another cushion of a patient interface configured to be worn by a patient and convey pressurized air to the patient’s nose and the patient’s mouth.

[0129] Fig. 3G shows a perspective view of a cushion of a patient interface configured to be worn by a patient and convey pressurized air to the patient’s nose and mouth.

[0130] Fig. 3H shows a perspective view of a cushion of a patient interface configured to be worn by a patient and convey pressurized air to the patient’s nose.

[0131] Fig. 31 shows a perspective view of tubes usable with either the cushion of Fig. 3G.

[0132] Fig. 3 J shows a perspective view of rigi diser arms usable with the cushion of Fig. 3H.

[0133] Fig. 3K shows a perspective view of tubes usable with the cushion of Fig.3G or the cushion of 3H.

[0134] Fig. 3L shows a perspective view of rigidizer arms that are usable with either the cushion of Fig. 3G or the cushion of Fig. 3H.

[0135] Fig. 3M shows a front view of a pair of sleeves that is removably fitted to either the tubes of Fig. 3K or the rigidizer arm of Fig. 3L.

[0136] Fig. 3N shows a front view of a full sleeve that is removably fitted to the rigi diser arms of Fig. 3L.

[0137] Fig. 30 shows a front perspective view of yet another alternate form of a full sleeve that is removably fitted to the rigi diser arms of Fig. 3L.3.4 RPT DEVICE

[0138] Fig. 4 A shows an RPT device in accordance with one form of the present technology.

[0139] Fig. 4B is a schematic diagram of the pneumatic path of an RPT device in accordance with one form of the present technology. The directions of upstream and downstream are indicated with reference to the blower and the patient interface. The blower is defined to be upstream of the patient interface and the patient interface is defined to be downstream of the blower, regardless of the actual flow direction at any particular moment. Items which are located within the pneumatic path between the blower and the patient interface are downstream of the blower and upstream of the patient interface.

[0140] Fig. 4C is a schematic diagram of the electrical components of an RPT device in accordance with one form of the present technology.

[0141] Fig. 4D is a schematic diagram of the algorithms implemented in an RPT device in accordance with one form of the present technology.

[0142] Fig. 4E is a flow chart illustrating a method carried out by the therapy engine module of Fig. 4D in accordance with one form of the present technology.

[0143] Fig. 4F is a chart showing the correlation between pressure in the patient interface and a flow rate of the vent.3.5 HUMIDIFIER

[0144] Fig. 5A shows an isometric view of a humidifier in accordance with one form of the present technology.

[0145] Fig. 5B shows an isometric view of a humidifier in accordance with one form of the present technology, showing a humidifier reservoir 5110 removed from the humidifier reservoir dock 5130.3.6 BREATHING WAVEFORMS

[0146] Fig. 6 A shows a model typical breath waveform of a person while sleeping.

[0147] PATIENT INTERFACE WITH VENTING ARRANGEMENT

[0148] Fig. 7 A shows a schematic diagram of an air circuit with a venting arrangement.

[0149] Fig. 7B shows an exemplary air circuit with the venting arrangement.

[0150] Fig. 7C shows a cross-sectional view of the air circuit of Fig. 7A and Fig.7B.

[0151] Fig. 7D shows a schematic diagram of another air circuit with a venting arrangement.

[0152] Fig. 7E shows a schematic diagram of another air circuit with a venting arrangement.

[0153] Fig. 7F shows a cross-sectional view of the air circuit of Fig. 7E.

[0154] Fig. 7G shows an exemplary air circuit with a venting arrangement in a first position.

[0155] Fig. 7H shows the air circuit of Fig. 7G in a second position.

[0156] Fig. 71 shows another exemplary cross-section of the air circuit with a venting arrangement.

[0157] Fig. 7 J shows another exemplary cross-section of the air circuit with a venting arrangement.

[0158] Fig. 7K shows a schematic diagram of another air circuit with a venting arrangement.

[0159] Fig. 7L shows an adaptor for the air circuit of Fig. 7L.

[0160] Fig. 7M shows an exploded view of an exemplary patient interface with a connector having a venting arrangement.

[0161] Fig. 7N shows another exploded view of the patient interface and connector of Fig. 7M.

[0162] Fig. 70 shows another exploded view of the patient interface and connector of Fig. 7M.

[0163] Fig. 7P shows a perspective view of the connector of Figs. 7M-7O.

[0164] Fig. 7Q shows a side view of the connector of Figs. 7M-7O.

[0165] Fig. 7R shows a perspective view of the patient interface and connector of Fig. 7M.

[0166] Figs. 7S and 7T illustrate schematic diagrams of a universal connector for a patient interface that can be used with venting and non-venting conduits.

[0167] Fig. 7U is a perspective view of a universal connector for a patient interface that can be used with venting and non-venting conduits.

[0168] Fig. 7V shows a perspective view of another patient interface with a venting arrangement.4 DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY

[0169] Before the present technology is described in further detail, it is to be understood that the technology is not limited to the particular examples described herein, which may vary. It is also to be understood that the terminology used in this disclosure is for the purpose of describing only the particular examples discussed herein, and is not intended to be limiting.

[0170] 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.4.1 THERAPY

[0171] In one form, the present technology comprises a method for treating a respiratory disorder comprising applying positive pressure to the entrance of the airways of a patient 1000.

[0172] In certain examples of the present technology, a supply of air at positive pressure is provided to the nasal passages of the patient via one or both nares.

[0173] In certain examples of the present technology, mouth breathing is limited, restricted or prevented.4.2 RESPIRATORY THERAPY SYSTEMS

[0174] In one form, the present technology comprises a respiratory therapy system for treating a respiratory disorder. The respiratory therapy system may comprise an RPT device 4000 for supplying a flow of air to the patient 1000 via an air circuit 4170 and a patient interface 3000.4.3 PATIENT INTERFACE

[0175] A non-invasive patient interface 3000, such as that shown in Fig. 3A, in accordance with one aspect of the present technology comprises the following functional aspects: a seal-forming structure 3100, a plenum chamber 3200, a positioning and stabilising structure 3300, one form of connection port 3600 for connection to air circuit 4170, and a forehead support 3700. In some forms a functional aspect may be provided by one or more physical components. In someforms, one physical component may provide one or more functional aspects. In use the seal -forming structure 3100 is arranged to surround an entrance to the airways of the patient so as to maintain positive pressure at the entrance(s) to the airways of the patient 1000. The sealed patient interface 3000 is therefore suitable for delivery of positive pressure therapy. As shown in Fig. 3B, a non-invasive patient interface 3000 in accordance with another aspect of the present technology comprises the following functional aspects: a seal-forming structure 3100, a plenum chamber 3200, a positioning and stabilising structure 3300, and one form of connection port 3600 for connection to air circuit 4170. In some forms, one physical component may provide one or more functional aspects. In use the seal -forming structure 3100 is arranged to surround an entrance to the airways of the patient so as to maintain positive pressure at the entrance(s) to the airways of the patient 1000. The sealed patient interface 3000 is therefore suitable for delivery of positive pressure therapy.

[0176] As shown in Fig. 3C, a non-invasive patient interface 3000 in accordance with another aspect of the present technology comprises the following functional aspects: a seal-forming structure 3100, a plenum chamber 3200, a positioning and stabilising structure 3300, and one form of connection port 3600 for connection to an air circuit (such as the air circuit 4170 shown in Figs. 1A-1C). The plenum chamber 3200 may be formed of one or more modular components (e.g., a cushion module 3150 together with the seal-forming structure 3100) in the sense that it or they can be replaced with different components, for example components of a different size.

[0177] 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.

[0178] The patient interface 3000 in accordance with one form of the present technology is constructed and arranged to be able to provide a supply of air at a positive pressure above the ambient, for example at least 2, 4, 6, 10, or 20 cmH20 with respect to ambient.4.3.1 Seal-forming structure

[0179] In one form of the present technology, a seal-forming structure 3100 provides a target seal-forming region, and may additionally provide a cushioning function. The target seal-forming region is a region on the seal-forming structure 3100 where sealing may occur. The region where sealing actually occurs- the actual sealingsurface- 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.

[0180] In one form the target seal -forming region is located on an outside surface of the seal-forming structure 3100.

[0181] In certain forms of the present technology, the seal -forming structure 3100 is constructed from a biocompatible material, e.g. silicone rubber.

[0182] A seal -forming structure 3100 in accordance with the present technology may be constructed from a soft, flexible, resilient material such as silicone.

[0183] In certain forms of the present technology, a system is provided comprising more than one a seal-forming structure 3100, each being configured to correspond to a different size and / or shape range. For example the system may comprise one form of a seal-forming structure 3100 suitable for a large sized head, but not a small sized head and another suitable for a small sized head, but not a large sized head.4.3.1.1 Sealing mechanisms

[0184] In one form, the seal -forming structure includes a sealing flange utilizing a pressure assisted sealing mechanism. In use, the sealing flange can readily respond to a system positive pressure in the interior of the plenum chamber 3200 acting on its underside to urge it into tight sealing engagement with the face. The pressure assisted mechanism may act in conjunction with elastic tension in the positioning and stabilising structure.

[0185] In one form, the seal -forming structure 3100 comprises a sealing flange and a support flange. The sealing flange comprises a relatively thin member with a thickness of less than about 1mm, for example about 0.25mm to about 0.45mm, which extends around the perimeter of the plenum chamber 3200. Support flange may be relatively thicker than the sealing flange. The support flange is disposed between the sealing flange and the marginal edge of the plenum chamber 3200, and extends at least part of the way around the perimeter. The support flange is or includes a springlike element and functions to support the sealing flange from buckling in use.

[0186] 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 aresult of elastic tension in the positioning and stabilising structure. It is contemplated that the compression sealing portion may be made of a compressible material such as a foam material.

[0187] 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.

[0188] In one form, the seal -forming structure comprises a region having a tacky or adhesive surface.

[0189] 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.4.3.1.2 Nose bridge or nose ridge region

[0190] In one form, the non-invasive patient interface 3000 comprises a sealforming structure that forms a seal in use on a nose bridge region or on a nose-ridge region of the patient's face.4.3.1.3 Upper lip region

[0191] In one form, the non-invasive patient interface 3000 comprises a sealforming structure that forms a seal in use on an upper lip region (that is, the lip superior) of the patient's face.4.3.1.4 Chin-region

[0192] In one form the non-invasive patient interface 3000 comprises a sealforming structure that forms a seal in use on a chin-region of the patient's face.

[0193] 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.4.3.1.5 Nasal pillows

[0194] In one form the seal-forming structure of the non-invasive patient interface 3000 comprises a pair of nasal puffs, or nasal pillows, each nasal puff or nasal pillow being constructed and arranged to form a seal with a respective naris of the nose of a patient. The patient interface 3000 shown in Fig. 3D has this type of seal-forming structure 3100.

[0195] 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 andconnecting 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.4.3.1.6 Nose-only Masks

[0196] In one form, the patient interface 3000 comprises a seal-forming structure 3100 configured to seal around an entrance to the patient’s nasal airways but not around the patient’s mouth. The seal -forming structure 3100 may be configured to seal to the patient’s lip superior. The patient interface 3000 may leave the patient’s mouth uncovered. This patient interface 3000 may deliver a supply of air or breathable gas to both nares of patient 1000 and not to the mouth. This type of patient interface may be identified as a nose-only mask.

[0197] One form of nose-only mask according to the present technology is what has traditionally been identified as a “nasal mask”, having a seal-forming structure 3100 configured to seal on the patient’s face around the nose and over the bridge of the nose. A nasal mask may be generally triangular in shape. In one form, the non-invasive patient interface 3000 comprises a seal-forming structure 3100 that forms a seal in use to an upper lip region (e.g. the lip superior), to the patient’s nose bridge or at least a portion of the nose ridge above the pronasale, and to the patient's face on each lateral side of the patient’s nose, for example proximate the patient’s nasolabial sulci. The patient interfaces 3000 shown in Figs. 1 A, 3A, and 3B have this type of seal-forming structure 3100. These patient interfaces 3000 may deliver a supply of air or breathable gas to both nares of patient 1000 through a single orifice or multiple orifices.

[0198] Another form of nose-only mask may seal around an inferior periphery of the patient’s nose without engaging the user’s nasal ridge. This type of patient interface 3000 may be identified as a “nasal cradle” mask and the seal-forming structure 3100 may be identified as a “nasal cradle cushion”, for example. In one form, for example as shown in Fig. 3C, the seal-forming structure 3100 is configured to form a seal in use with inferior surfaces of the nose around the nares. The sealforming structure 3100 may be configured to seal around the patient’s nares at aninferior periphery of the patient’s nose including to an inferior and / or anterior surface of a pronasale region of the patient’s nose and to the patient’s nasal alae. The sealforming structure 3100 may seal to the patient’s lip superior. The shape of the sealforming structure 3100 may be configured to match or closely follow the underside of the patient’s nose and may not contact a nasal bridge region of the patient’s nose or any portion of the patient’s nose superior to the pronasale. In one form of nasal cradle cushion, the seal-forming structure 3100 comprises a bridge portion dividing the opening into two orifices, each of which, in use, supplies air or breathable gas to a respective one of the patient’s nares. The bridge portion may be configured to contact or seal against the patient’s columella in use. Alternatively, the seal-forming structure 3100 may comprise a single opening to provide a flow or air or breathable gas to both of the patient’s nares.

[0199] In some forms, a nose-only mask may comprise nasal pillows, described above.4.3.1.7 Nose and Mouth Masks

[0200] In one form, the patient interface 3000 comprises a seal-forming structure 3100 configured to seal around an entrance to the patient’s nasal airways and also around the patient’s mouth. The seal -forming structure 3100 may be configured to seal to the patient’s face proximate a chin region. This patient interface 3000 may deliver a supply of air or breathable gas to both nares and to the mouth of patient 1000. This type of patient interface may be identified as a nose and mouth mask.

[0201] One form of nose-and-mouth mask according to the present technology is what has traditionally been identified as a “full-face mask”, having a seal-forming structure 3100 configured to seal on the patient’s face around the nose, below the mouth and over the bridge of the nose. A nose-and-mouth mask may be generally triangular in shape. In one form the patient interface 3000 comprises a seal-forming structure 3100 that forms a seal in use to a patient’s chin-region (which may include the patient’s lip inferior and / or a region directly inferior to the lip inferior), to the patient’s nose bridge or at least a portion of the nose ridge superior to the pronasale, and to cheek regions of the patient's face. The patient interface 3000 shown in Figs.1C and 3E are of this type. This patient interface 3000 may deliver a supply of air or breathable gas to both nares and mouth of patient 1000 through a single orifice. This type of seal-forming structure 3100 may be referred to as a “nose-and-mouth cushion”.

[0202] In another form the patient interface 3000 comprises a seal-forming structure 3100 that forms a seal in use on a patient’s chin region (which may include the patient’s lip inferior and / or a region directly inferior to the lip inferior), to an inferior and / or an anterior surface of a pronasale portion of the patient’s nose, to the alae of the patient’s nose and to the patient’s face on each lateral side of the patient’s nose, for example proximate the nasolabial sulci. The seal-forming structure 3100 may also form a seal against a patient’s lip superior. A patient interface 3000 having this type of seal-forming structure may have a single opening configured to deliver a flow of air or breathable gas to both nares and mouth of a patient, may have an oral hole configured to provide air or breathable gas to the mouth and a nasal hole configured to provide air or breathable gas to the nares, or may have an oral hole for delivering air to the patient’s mouth and two nasal holes for delivering air to respective nares. This type of patient interface 3000 may have a nasal portion and an oral portion, the nasal portion sealing to the patient’s face at similar locations to a nasal cradle mask. The patient interface 3000 shown in Fig. 3F has this type of sealforming structure 3100.

[0203] In a further form of nose and mouth mask, the patient interface 3000 may comprise a seal -forming structure 3100 having a nasal portion comprising nasal pillows and an oral portion configured to form a seal to the patient’s face around the patient’s mouth.

[0204] In some forms, the seal -forming structure 3100 may have a nasal portion that is separate and distinct from an oral portion. In other forms, a seal-forming structure 3100 may form a contiguous seal around the patient’s nose and mouth.

[0205] It is to be understood that the above examples of different forms of patient interface 3000 do not constitute an exhaustive list of possible configurations. In some forms a patient interface 3000 may comprise a combination of different features of the above described examples of nose-only and nose and mouth masks.4.3.2 Plenum chamber

[0206] The plenum chamber 3200 has a perimeter that is shaped to be complementary to the surface contour of the face of an average person in the region where a seal will form in use. In use, a marginal edge of the plenum chamber 3200 is positioned in close proximity to an adjacent surface of the face. Actual contact with the face is provided by the seal -forming structure 3100. The seal-forming structure3100 may extend in use about the entire perimeter of the plenum chamber 3200. In some forms, the plenum chamber 3200 and the seal -forming structure 3100 are formed from a single homogeneous piece of material.

[0207] In certain forms of the present technology, the plenum chamber 3200 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.

[0208] In certain forms of the present technology, the plenum chamber 3200 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.

[0209] In certain forms of the present technology, the plenum chamber 3200 is constructed from a translucent material. The use of a translucent material can reduce the obtrusiveness of the patient interface, and help improve compliance with therapy.

[0210] In some forms, the plenum chamber 3200 is constructed from a rigid material such as polycarbonate. The rigid material may provide support to the sealforming structure.

[0211] In some forms, the plenum chamber 3200 is constructed from a flexible material (e.g., constructed from a soft, flexible, resilient material like silicone, textile, foam, etc.). For example, in examples then may be formed from a material which has a Young's modulus of 0.4 GPa or lower, for example foam. In some forms of the technology the plenum chamber 3200 may be made from a material having Young's modulus of 0.1 GPa or lower, for example rubber. In other forms of the technology the plenum chamber 3200 may be made from a material having a Young's modulus of 0.7MPa or less, for example between 0.7MPa and 0.3MPa. An example of such a material is silicone.4.3.2.1 Multiple Openings

[0212] As shown in Figs. 3G and 3H, different plenum chambers 3200-1, 3200-2 may be formed as part of a multi -opening cushion 3050-1, 3050-2. In the illustrated examples, the cushions 3050-1, 3050-2 each include two openings, although an alternate cushion may be formed with greater or fewer openings. In the illustratedexamples, at least one opening may serve two different functions. For example, one opening may operate as both an inlet and an outlet during the same breathing cycle.

[0213] The plurality of openings may allow for a variety of configurations of air delivery to the plenum 3200-1. For example, depending on patient need and / or patient comfort, the patient may use a given cushion 3050-1, 3050-2 in a “tube-up” configuration (e.g., using conduit headgear - described below) or a “tube-down” configuration (e.g., using a single conduit in front of the patient’s face).4.3.2.1.1 Nose and Mouth Mask

[0214] As shown in Fig. 3G, the plenum chamber 3200-1 includes a pair of plenum chamber inlet ports 3254-1, which may be used to convey gas into and / or out of the plenum chamber 3200-1. The plenum chamber inlet ports 3254-1 may be disposed on opposite sides (e.g., left and right sides) of the plenum chamber 3200-1.

[0215] In some forms, the plenum chamber 3200-1 may include a pair of grooves 3266-1. Each groove 3266-1 may be disposed proximate to one of the plenum chamber inlet ports 3254-1. Each groove 3266-1 may form a partially recessed surface.4.3.2.1.2 Nose-only Mask

[0216] The plenum chamber 3200-2 of a nasal only cushion 3050-2 may be similar to the plenum chamber 3200-1 of the mouth and nose cushion 3050-1. Only some similarities and differences between the plenum chambers 3200-1, 3200-2 may be described below.

[0217] As shown in Fig. 3H, the plenum chamber 3200-2 includes a pair of plenum chamber inlet ports 3254-2, which may be used to convey gas into and / or out of the plenum chamber 3200-2. The plenum chamber inlet ports 3254-2 may be disposed on opposite sides (e.g., left and right sides) of the plenum chamber 3200-2.

[0218] In some forms, the plenum chamber 3200-2 may include a pair of grooves 3266-2. Each groove 3266-2 may be disposed proximate to one of the plenum chamber inlet ports 3254-2. Each groove 3266-2 may form a partially recessed surface.4.3.3 Positioning and stabilising structure

[0219] The seal-forming structure 3100 of the patient interface 3000 of the present technology may be held in sealing position in use by the positioning and stabilising structure 3300. The positioning and stabilising structure 3300 maycomprise and function as “headgear” since it engages the patient’s head in order to hold the patient interface 3000 in a sealing position. Examples of a positioning and stabilising structure may be shown in Fig. 3 A.

[0220] In one form the positioning and stabilising structure 3300 provides a retention force at least sufficient to overcome the effect of the positive pressure in the plenum chamber 3200 to lift off the face (i.e., Fpienum).

[0221] In one form the positioning and stabilising structure 3300 provides a retention force to overcome the effect of the gravitational force on the patient interface 3000.

[0222] In one form the positioning and stabilising structure 3300 provides a retention force as a safety margin to overcome the potential effect of disrupting forces on the patient interface 3000, such as from tube drag, or accidental interference with the patient interface.

[0223] In one form of the present technology, a positioning and stabilising structure 3300 is provided that is configured in a manner consistent with being worn by a patient while sleeping. In one example the positioning and stabilising structure 3300 has a low profile, or cross-sectional thickness, to reduce the perceived or actual bulk of the apparatus. In one example, the positioning and stabilising structure 3300 comprises at least one strap having a rectangular cross-section. In one example the positioning and stabilising structure 3300 comprises at least one flat strap.

[0224] In one form of the present technology, a positioning and stabilising structure 3300 is provided that is configured so as not to be too large and bulky to prevent the patient from lying in a supine sleeping position with a back region of the patient’s head on a pillow.

[0225] In one form of the present technology, a positioning and stabilising structure 3300 is provided that is configured so as not to be too large and bulky to prevent the patient from lying in a side sleeping position with a side region of the patient’s head on a pillow.

[0226] In one form of the present technology, a positioning and stabilising structure 3300 is provided with a decoupling portion located between an anterior portion of the positioning and stabilising structure 3300, and a posterior portion of the positioning and stabilising structure 3300. The decoupling portion does not resist compression and may be, e.g. a flexible or floppy strap. The decoupling portion is constructed and arranged so that when the patient lies with their head on a pillow, thepresence of the decoupling portion prevents a force on the posterior portion from being transmitted along the positioning and stabilising structure 3300 and disrupting the seal.

[0227] In one form of the present technology, a positioning and stabilising structure 3300 comprises a strap constructed from a laminate of a fabric patientcontacting 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.

[0228] In certain forms of the present technology, a positioning and stabilising structure 3300 comprises a strap that is extensible, e.g. resiliently extensible. For example the strap may be configured in use to be in tension, and to direct a force to draw a seal-forming structure into sealing contact with a portion of a patient’s face. In an example the strap may be configured as a tie.

[0229] 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 a parietal bone without overlaying the occipital bone.

[0230] 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.

[0231] 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.

[0232] In certain forms of the present technology, a positioning and stabilising structure 3300 comprises a strap that is bendable and e.g. non-rigid. An advantage of this aspect is that the strap is more comfortable for a patient to lie upon while the patient is sleeping.

[0233] In certain forms of the present technology, a positioning and stabilising structure 3300 comprises a strap constructed to be breathable to allow moisture vapour to be transmitted through the strap.

[0234] In certain forms of the present technology, a system is provided comprising more than one positioning and stabilising structure 3300, each being configured to provide a retaining force to correspond to a different size and / or shape range. For example, the system may comprise one form of positioning and stabilising structure 3300 suitable for a large sized head, but not a small sized head, and another, suitable for a small sized head, but not a large sized head.4.3.3.1 Conduit headgear4.3.3.1.1 Conduit headgear tubes

[0235] In some forms of the present technology, the positioning and stabilising structure 3300 comprises one or more headgear tubes 3350 that deliver pressurised air received from a conduit forming part of the air circuit 4170 from the RPT device to the patient’s airways, for example through the plenum chamber 3200 and sealforming structure 3100. In the form of the present technology illustrated in Fig. 3F, the positioning and stabilising structure 3300 comprises two tubes 3350 that deliver air to the plenum chamber 3200 from the air circuit 4170. The tubes 3350 are configured to position and stabilise the seal-forming structure 3100 of the patient interface 3000 at the appropriate part of the patient’s face (for example, the nose and / or mouth) in use. This allows the conduit of air circuit 4170 providing the flow of pressurised air to connect to a connection port 3600 of the patient interface in a position other than in front of the patient’s face, for example on top of the patient’s head.

[0236] In the form of the present technology illustrated in Fig. 3F, the positioning and stabilising structure 3300 comprises two tubes 3350, each tube 3350 being positioned in use on a different side of the patient’s head and extending across the respective cheek region, above the respective ear (superior to the otobasion superior on the patient’s head) to the connector (or elbow) 3610 on top of the head of the patient 1000. This form of technology may be advantageous because, if a patient sleeps with their head on its side and one of the tubes 3350 is compressed to block or partially block the flow of gas along the tube 3350, the other tube 3350 remains open to supply pressurised gas to the patient. In other examples of the technology, the patient interface 3000 may comprise a different number of tubes, for example one tube, or two or more tubes.

[0237] In one example in which the patient interface has one tube 3350, the single tube 3350 is positioned on one side of the patient’s head in use (e.g. across onecheek region) and a strap forms part of the positioning and stabilising structure 3300 and is positioned on the other side of the patient’s head in use (e.g. across the other region) to assist in securing the patient interface 3000 on the patient’s head. For example, the tube 3350 and the strap may each be under tension in use in order to assist in maintaining the seal-forming structure 3100 in a sealing position.

[0238] In one form, the tube 3350 may be at least partially extensible so that the tube 3350 and the strap may adjust substantially equal lengths when worn by a patient. This may allow for substantially symmetrical adjustments between the tube 3350 and the strap so that the seal-forming structure remains substantially in the middle.

[0239] In the form of the technology shown in Fig. 3F, the two tubes 3350 are fluidly connected at superior ends to each other and to the connection port 3600. In some examples, the two tubes 3350 are integrally formed while in other examples the tubes 3350 are formed separately but are connected in use and may be disconnected, for example for cleaning or storage. Where separate tubes are used, they may be indirectly connected together, for example, each may be connected to a T-shaped connector. The T-shaped connector may have two arms / branches each fluidly connectable to a respective one of the tubes 3350. Additionally, the T-shaped connector may have a third arm or opening providing the connection port 3600 for fluid connection to the air circuit 4170 in use. The opening may be an inlet 3332 (see e.g., 3K) for receiving the flow of pressurized air.

[0240] In some forms, the third arm of the T-shaped connector may be substantially perpendicular to each of the first two arms.

[0241] In some forms, the third arm of the T-shaped connector may be obliquely formed with respect to each of the first two arms.

[0242] In some forms, a Y-shaped connector may be used instead of the T-shaped connector. The first two arms may be oblique with respect to one another, and the third arm may be oblique with respect to the first two arms. The angled formation of the first two arms may be similar to the shape of the patient’s head in order to conform to the shape.

[0243] In some forms, at least one of the arms of the T-shaped connector (or Y-shaped connector) may be flexible. This may allow the connector to bend based on the shape of the patient’s head and / or a force in the positioning and stabilising structure 3300.

[0244] In some forms, at least one of the arms of the T-shaped connector (or Y-shaped connector) may be at least partially rigidised. This may assist in maintaining the shape of the connector so that bending of the connector does not close the airflow path.

[0245] The tubes 3350 may be formed from a flexible material, such as an elastomer, e.g. silicone or TPE, and / or from one or more textile and / or foam materials. The tubes 3350 may have a preformed shape and may be able to be bent or moved into another shape upon application of a force but may return to the original preformed shape in the absence of said force. The tubes 3350 may be generally arcuate or curved in a shape approximating the contours of a patient’s head between the top of the head and the nasal or oral region.

[0246] In some examples, the one or more tubes 3350 are crush resistant to resist being blocked if crushed during use, for example if squashed between a patient’s head and pillow, especially if there is only one tube 3350. The tubes 3350 may be formed with a sufficient structural stiffness to resist crushing or may be as described in US Patent No. 6,044,844, the contents of which are incorporated herein by reference.

[0247] Each tube 3350 may be configured to receive a flow of air from the connection port 3600 on top of the patient’s head and to deliver the flow of air to the seal-forming structure 3100 at the entrance of the patient’s airways. In the example shown in Fig. 3F, each tube 3350 lies in use on a path extending from the plenum chamber 3200 across the patient’s cheek region and superior to the patient’s ear to the elbow 3610. For example, a portion of each tube 3350 proximate the plenum chamber 3200 may overlie a maxilla region of the patient’s head in use. Another portion of each tube 3350 may overlie a region of the patient’s head superior to an otobasion superior of the patient’s head. Each of the tubes 3350 may also lie over the patient’s sphenoid bone and / or temporal bone and either or both of the patient’s frontal bone and parietal bone. The elbow 3610 may be located in use over the patient’s parietal bone, over the frontal bone and / or over the junction therebetween (e.g. the coronal suture).

[0248] In certain forms of the present technology the patient interface 3000 is configured such that the connection port 3600 can be positioned in a range of positions across the top of the patient’s head so that the patient interface 3000 can be positioned as appropriate for the comfort or fit of an individual patient. In some examples, the headgear tubes 3350 are configured to allow movement of an upperportion of the patient interface 3000 (e.g. a connection port 3600) with respect to a lower portion of the patient interface 3000 (e.g. a plenum chamber 3200). That is, the connection port 3600 may be at least partially decoupled from the plenum chamber 3200. In this way, the seal-forming structure 3100 may form an effective seal with the patient’s face irrespective of the position of the connection port 3600 (at least within a predetermined range of positions) on the patient’s head.

[0249] As described above, in some examples of the present technology the patient interface 3000 comprises a seal-forming structure 3100 in the form of a cradle cushion which lies generally under the nose and seals to an inferior periphery of the nose (e.g. an under-the-nose cushion). The positioning and stabilising structure 3300, including the tubes 3350 may be structured and arranged to pull the seal-forming structure 3100 into the patient’s face under the nose with a sealing force in a posterior and superior direction (e.g. a posterosuperior direction). A sealing force with a posterosuperior direction may cause the seal-forming structure 3100 to form a good seal to both the inferior periphery of the patient’s nose and anterior-facing surfaces of the patient’s face, for example on either side of the patient’s nose and the patient’s lip superior.4.3.3.1.2 Extendable and non-extendable tube portions

[0250] In some examples of the present technology, one or both of the tubes 3350 are not extendable in length. However, in some forms, the tubes 3350 may comprise one or more extendable tube sections, for example formed by an extendable concertina structure. In some forms, the patient interface 3000 may comprise a positioning and stabilising structure 3300 including at least one gas delivery tube comprising a tube wall having an extendable concertina structure. The patient interface 3000 shown in Fig. 3F comprises tubes 3350, the superior portions of which comprise extendable tube sections each in the form of an extendable concertina structure 3362.

[0251] In some forms, the extendable concertina structure 3328 may be formed as a series of ridges and grooves on the surface of the tubes 3350. The concertina structure 3328 may be biased toward a retracted position and may move to an expanded position when the patient dons the positioning and stabilising structure 3300. Because portions of the tubes 3350 may be substantially inextensible (e.g., non-extendable tube sections 3363), the concertina structures 3328 permit the positioning and stabilising structure 3300 to stretch in order to fit different sized heads. This mayallow a single sized tube 3350 to be used with multiple sized heads. For example, the positioning and stabilising structure 3300 may be “one-size-fits-all” as a result of the concertina structure 3328. Alternatively, the tubes 3350 may be manufactured in multiple sizes (e.g., small, medium, large). The patient may select a length that most closely conforms to their head, and the concertina structures 3328 may make small adjustments in order to tailor the fit to the individual patient.

[0252] In some forms, the inlet 3332 may be disposed in the middle of the conduit 6320. For example, the tubes 3350 may be symmetric about the inlet 3332 through at least one axis.

[0253] The cross-sectional shape of the non-extendable tube sections 3363 of the tubes 3350 may be circular, elliptical, oval, D-shaped or a rounded rectangle, for example as described in US Patent No. 6,044,844. A cross-sectional shape that presents a flattened surface of tube on the side that faces and contacts the patient’s face or other part of the head may be more comfortable to wear than, for example a tube with a circular cross-section.

[0254] In some examples of the present technology, the non-extendable tube sections 3363 connects to the plenum chamber 3200 from a low angle. The headgear tubes 3350 may extend inferiorly down the sides of the patient’s head and then curve anteriorly and medially to connect to the plenum chamber 3200 in front of the patient’s face. The tubes 3350, before connecting to the plenum chamber 3200, may extend to a location at the same vertical position as (or, in some examples, inferior to) the connection with the plenum chamber 3200. That is, the tubes 3350 may project in an at least partially superior direction before connecting with the plenum chamber 3200. A portion of the tubes 3350 may be located inferior to the plenum chamber 3200 and / or the seal forming structure 3100. The tubes 3350 may contact the patient’s face below the patient’s cheekbones, which may be more comfortable than contact on the patient’s cheekbones and may avoid excessively obscuring the patient’s peripheral vision.4.3.3.1.3 Conduit headgear connection port

[0255] In certain forms of the present technology, the patient interface 3000 may comprise a connection port 3600 located proximal to a superior, lateral or posterior portion of a patient’s head. For example, in the form of the present technology illustrated in Fig 3F, the connection port 3600 is located on top of the patient’s head (e.g. at a superior location with respect to the patient’s head). In this example thepatient interface 3000 comprises an elbow 3610 forming the connection port 3600. The elbow 3610 may be configured to fluidly connect with a conduit of an air circuit 4170. The elbow 3610 may be configured to swivel with respect to the positioning and stabilising structure 3300 to at least partially decouple the conduit from the positioning and stabilising structure 3300. In some examples the elbow 3610 may be configured to swivel by rotation about a substantially vertical axis and, in some particular examples, by rotation about two or more axes. In some examples the elbow may comprise or be connected to the tubes 3350 by a ball-and-socket joint. The connection portion 3600 may be located in the sagittal plane of the patient’s head in use.

[0256] Patient interfaces having a connection port that is not positioned anterior to the patient’s face may be advantageous as some patients may find a conduit that connects to a patient interface anterior to their face to be unsightly and / or obtrusive. For example, a conduit connecting to a patient interface anterior to the patient’s face may be prone to interference with bedclothes or bed linen, particularly if the conduit extends inferiorly from the patient interface in use. Forms of the present technology comprising a patient interface having a connection port positioned superiorly to the patient’s head in use may make it easier or more comfortable for a patient to lie or sleep in one or more of the following positions: a side-sleeping position, a supine position (e.g. on their back, facing generally upwards) or in a prone position (e.g. on their front, facing generally downwards). Moreover, connecting a conduit to an anterior portion of a patient interface may exacerbate a problem known as tube drag in which the conduit exerts an undesired force upon the patient interface during movement of the patient’s head or the conduit, thereby causing dislodgement away from the face. Tube drag may be less of a problem when force is received at a superior location of the patient’s head than anterior to the patient’s face proximate to the seal-forming structure (where tube drag forces may be more likely to disrupt the seal).4.3.3.1.4 Headgear Tube Fluid Connections

[0257] The two tubes 3350 are fluidly connected at their inferior ends to the plenum chamber 3200. In certain forms of the technology, the connection between the tubes 3350 and the plenum chamber 3200 is achieved by connection of two rigid connectors. The tubes 3350 and plenum chamber 3200 may be configured to enable the patient to easily connect the two components together in a reliable manner. Thetubes 3350 and plenum chamber 3200 may be configured to provide tactile and / or audible feedback in the form of a ‘re-assuring click’ or a similar sound, so that the patient may easily know that each tube 3350 has been correctly connected to the plenum chamber 3200. In one form, the tubes 3350 are formed from a silicone or textile material and the inferior end of each of the silicone tubes 3350 is overmolded to a rigid connector made, for example, from polypropylene, polycarbonate, nylon or the like. The rigid connector on each tube 3350 may comprise a female mating feature configured to connect with a male mating feature on the plenum chamber 3200.Alternatively, the rigid connector on each tube 3350 may comprise a male mating feature configured to connect to a female mating feature on the plenum chamber 3200. In other examples the tubes 3350 may each comprise a male or female connector formed from a flexible material, such as silicone or TPE, for example the same material from which the tubes 3350 are formed.

[0258] In other examples a compression seal is used to connect each tube 3350 to the plenum chamber 3200. For example, a resiliently flexible (e.g. silicone) tube 3350 without a rigid connector may be configured to be squeezed to reduce its diameter so that it can be compressed into a port in the plenum chamber 3200 and the inherent resilience of the silicone pushes the tube 3350 outwards to seal the tube 3350 in the port in an air-tight manner. Alternatively, in a hard-to-hard type engagement between the tube 3350 and the plenum chamber 3200, each tube 3350 and / or plenum chamber 3200 may comprise a pressure activated seal, for example a peripheral sealing flange. When pressurised gas is supplied through the tubes 3350 the sealing flange may be urged against the join between the tubes and a circumferential surface around a port or connector of the plenum chamber 3200 to form or enhance a seal between the tube 3350 and plenum chamber 3200.4.3.3.1 Headgear straps

[0259] In some forms, the positioning and stabilising structure 3300 may include headgear 3302 with at least one strap which may be worn by the patient in order to assist in properly orienting the seal -forming structure 3100 against the patient’s face (e.g., in order to limit or prevent leaks).

[0260] As described above, some forms of the headgear 3302 may be constructed from a textile material, which may be comfortable against the patient’s skin. The textile may be flexible in order to conform to a variety of facial contours. Althoughthe textile may include rigidisers along a selected length, which may limit bending, flexing, and / or stretching of the headgear 3302.

[0261] In certain forms, the headgear 3302 may be at least partially extensible. For example, the headgear 3302 may include elastic, or a similar extensible material. For example, the entire headgear 3302 may be extensible or selected portions may be extensible (or more extensible than surrounding portions). This may allow the headgear 3302 to stretch while under tension, which may assist in providing a sealing force for the seal -forming structure 3100.

[0262] Two forms of the headgear, four-point headgear 3302-1 and two-point headgear 3302-2, are discussed in more detail below as illustrative examples.4.3.3.2.1 Four-point connection

[0263] As shown in Fig. 31, some forms of the headgear 3302-1 may be a four-point connection headgear. This means that the headgear 3302-1 may connect to four separate places on the plenum chamber 3200, on a frame connected to the plenum chamber 3200, and / or on arms connected to the plenum chamber 3200. The headgear 3302-1 may include four different straps providing a tensile force to help maintain the seal-forming structure 3100 in a sealing position. The positioning and stabilising structure 3300 of Fig. 3 A may also be considered a four-point connection headgear.

[0264] In some forms, the headgear 3302-1 may include inferior straps 3304-1, which may connect to an inferior portion of the cushion 3050-1. The inferior straps 3304-1 may extend along the patient’s cheek toward a posterior region of the patient’s head. For example, the inferior straps 3304-1 may overlay the masseter muscle on either side of the patient’s face. The inferior straps 3304-1 may therefore contact the patient’s head below the patient’s ears. The inferior straps 3304-1 may meet at the posterior of the patient’s head, and may overlay the occipital bone and / or the trapezius muscle.

[0265] The headgear 3302-1 may also include superior straps 3305-1, which may overlay the temporal bones, parietal bone, and / or occipital bone. The superior straps 3305-1 may also connect to the tubes 3350 (e.g., by interfacing with the tabs 3320).

[0266] A rear strap 3307-1 may extend between the superior straps 3305-1 and between the inferior straps 3304-1. The inferior and superior straps 3304-1, 3305-1 on a given side (e.g., left or right) may also be connected to the rear strap 3307-1 adjacent to one another. The height of the rear strap 3307-1 may therefore be approximately the combined height of the inferior and superior strap 3304-1, 3305-1.The rear strap 3307-1 may overlay the occipital bone and / or the pariental bone in use. This may allow the rear strap 3307-1 to assist in anchoring the headgear 3302-1 to the patient’s head.

[0267] In the illustrated example, the headgear 3302-1 may be formed with a substantially X-shape. The inferior and superior straps 3304-1, 3305-1 may be connected to a rear strap 3307-1 using stitching, ultrasonic welding, or any similar process.

[0268] In some forms, the inferior straps 3304-1 are connected to a magnetic member 3306-1. For example, each inferior straps 3304-1 may be threaded through a magnetic member 3306-1, so that a length of each inferior strap 3304-1 may be adjusted. The magnetic members 3306-1 may removably connect to the magnets 3370-1 (described below), so that the inferior straps 3304-1 may be disconnected from the plenum chamber 3200, but the length of the inferior straps 3304-1 may not be affected.

[0269] In some forms, the superior straps 3305-1 may be connected directly to the tabs 3320 of the tubes 3350. The superior straps 3305-1 may be threaded through the tabs 3320 in order to adjust the length and control the tensile force of each superior strap 3305-1.

[0270] In some forms, the headgear 3302-1 may be used only with the nose and mouth cushion 3050-1 (e.g., because the nose-only cushion 3050-1 does not have four connection points). However, the headgear 3302-1 may be used interchangeably with the tubes 3350 and the rigidiser arms 3340.4.3.3.2.2 Two-point connection

[0271] As shown in Fig. 3J, some forms of the headgear 3302-2 may be a two-point connection headgear. This means that the headgear 3302-2 may connect to two separate places.

[0272] In some forms, the headgear 3302-2 may be formed from a continuous piece of material. In other words, the headgear 3302-2 may not be formed from multiple straps connected (e.g., stitched) together. This may be comfortable for a patient as they will not be in contact with any seams or joints connecting different straps. In other forms, the headgear 3302-2 may be formed from multiple straps (e.g., two superior straps, a rear strap, etc.) that are connected together (e.g., with stitching, ultra-sonic welding, etc.).

[0273] In certain forms of the present technology, the positioning and stabilising structure 3300 comprises at least one headgear strap acting in addition to the tubes 3350 to position and stabilise the seal-forming structure 3100 at the entrance to the patient’s airways. As shown in Fig. 3J, the patient interface 3000 comprises a strap 3307-2 forming part of the positioning and stabilising structure 3300. The strap 3307-2 may be known as a back strap or a rear headgear strap, for example. The rear strap 3307-2 may overlay the temporal bones, parietal bone, and / or occipital bone. In other examples of the present technology, one or more further straps may be provided. For example, patient interfaces 3000 according to examples of the present technology having a nose-and-mouth cushion may have a second, lower, strap configured to lie against the patient’s head proximate the patient’s neck and / or against posterior surfaces of the patient’s neck.

[0274] In the example shown in Fig. 3F, strap 3310 of the positioning and stabilising structure 3300 is connected between the two tubes 3350 positioned on each side of the patient’s head and passing around the back of the patient’s head, for example overlying or lying inferior to the occipital bone of the patient’s head in use. The strap 3310 connects to each tube above the patient’s ears. With reference to Fig.3F, the positioning and stabilising structure 3300 comprises a pair of tabs 3320. In use a strap 3310 may be connected between the tabs 3320. The strap 3310 may be sufficiently flexible to pass around the back of the patient’s head and lie comfortably against the patient’s head, even when under tension in use.

[0275] As shown in Fig. 3J, some forms of the headgear 3302-2 may be at least partially bifurcated. For example, a rear strap 3307-2 of the headgear 3302-2 (e.g., configured to contact the posterior portion of the patient’s head) may be wider than the surrounding portions of the headgear 3302-2. An intermediate section 3308-2 of the rear strap 3307-2 may include a slit 3309-2. A superior section of the rear strap 3307-2 may therefore be movable relative to the inferior section as a result of the slit 3309-2. This may allow the patient to have a larger strap coverage on the posterior region of their head, which may assist in better anchoring the headgear 3302-2 to the patient’s head since there is no inferior strap (e.g., 3304-1).

[0276] In some forms, the headgear 3302-2 may be used only with the nasal cushion 3050-2 (e.g., because the nose and mouth cushion 3050-1 does not have four connection points). However, the headgear 3302-2 may be used interchangeably with the tubes 3350 and the rigidiser arms 3340.4.3.3.3 Rigidiser Arm

[0277] As shown in Fig. 3L, a rigidiser arm 3340 may be an elongated, rigid member that assists in maintaining the cushion (e.g., the nose and mouth cushion 3050-1 or the nasal cushion 3050-2) in an operating position. The rigidiser arm 3340 may contact a side of the patient’s head and provide a force to limit slipping of the seal-forming structure 3100 from the patient’s nose and / or mouth.

[0278] In some forms, the rigidiser arm 3340 is constructed from a rigid material (e.g., plastic). The rigid material may not permit the rigidiser arm 3340 to stretch. Additionally, the rigidiser arm 3340 may be substantially inflexible and may be unable to bend. The rigidiser arm 3340 may be pre-molded into a desired shape in order to fit a patient’s head. For example, the rigidiser arms 3340 may be molded with a curved shape to substantially correspond to the shape of the side of the patient’s head (e.g., overlaying the masseter muscle and / or the temporal bone).

[0279] In certain forms, the rigidiser arm 3340 may be molded in order to conform to a specific patient’s head (e.g., the rigidiser arm 3340 is customized).

[0280] In some forms, the rigidiser arm 3340 may be flexible along at least one direction. For example, the rigidiser arm 3340 may be flexible about its width and may be inflexible along its length. In other words, the rigidiser arm 3340 may be bendable about an axis along the width of the rigidiser arm 3340, but may be unable to bend about an axis perpendicular to the rigidiser arm 3340. This may allow an individual patient to adjust the rigidiser arm 3340 in order to better fit their individual head.

[0281] In certain forms, the rigidiser arm 3340 may remain in the new position after being bent. This may allow a patient adjust the shape of the rigidiser arm 3340 for their specific head and then the rigidiser arm 3340 will keep the desired shape while in use in order to promote patient comfort.

[0282] In some forms, a first end 3342 of the rigidiser arm 3340 may be a free end and a second end 3344 (e.g., opposite of the first end 3342) of the rigidiser arm 3340 may be fixed. The first end 3342 may be curved in order to minimize sharp edges that could cause patient discomfort. The first end 3342 may also overlay the patient’s head proximate to the temporal bone, in use. The second end 3344 may be fixed to an arm connection structure 3504.

[0283] In some forms, the arm connection structure 3504 may be similar to the conduit connection structure 3500. For example, the arm connection structure 3504and the conduit connection structure 3500 may have substantially the same shape. This may allow either the conduit connection structure 3500 or the arm connection structure 3504 to fit into the groove (e.g., 3266-1 or 3266-2) and connect to the plenum chamber inlet port 3254. The arm connection structure 3504 may connect to the nose and mouth cushion 3050-1 or the nose-only cushion 3050-2 in substantially the same way as the conduit connection structure 3500 (e.g., via a snap fit, press fit, friction fit, etc.).

[0284] In some forms, the arm connection structure 3504 may act as a plug for the plenum chamber inlet port 3254 (e.g., either 3254-1 and / or 3254-2). Unlike the tubes 3350, the rigidiser arm 3340 does not convey pressurized air to the plenum chamber 3200. The rigidised arm 3340 may be used with a “tube down” configuration, where a hose is connected to the vent opening 3402 (e.g., either 3402-1 and / or 3402-2), and conveys air into the plenum chamber 3200 through the vent opening 3402. In this example, air does not need to travel into or out of the plenum chamber inlet openings 3254. Thus, the arm connection structure 3504 may form a seal with the plenum chamber inlet opening 3254 in order to limit airflow into or out of the plenum chamber 3200.4.3.3.4 Sleeve

[0285] In some forms, a sleeve may be used with the tubes 3350 and / or the rigidisier arms 3340. The sleeve may at least partially surround the tubes 3350 and / or the rigidiser arms 3340. As shown in Figs. 3M to 30, different shapes of sleeves may be used, which may correspond to different types of positioning and stabilising structures 3300. In some forms, the configuration of the sleeve may be customized to fit a particular user’s face. For instance, the sleeves may be configured in a relatively more posterior region of the patient’s head.

[0286] In some forms, the sleeve may be constructed from a comfortable material. For example, the sleeve may be constructed from a textile material, a foam material, or a combination of the two. The comfortable material may contact the patient in use, and may feel soft against the patient’s skin in order to improve patient compliance.

[0287] The material may also be flexible in order to assist in donning or doffing the sleeve from the tube 3350 or the rigidiser arms 3340. For example, the material may allow the sleeve to bend in order to conform to the shape of the tubes or conduitheadgear 3350 or the rigidiser arms 3340, which may change depending on the shape of an individual patient’s head.

[0288] In some forms, the sleeve may also be at least partially elastic (e.g., the material may allow the sleeve to stretch). The elastic material may help the sleeve stretch in order to fit around the tubes 3350 or the rigidiser arms 3340. The elastic material may then return to an initial position that is snug against the tubes 3350 or the rigidiser arms 3340 in order to limit the sleeve from sliding while in use.

[0289] 4.3.4 Decoupling structure(s)

[0290] In one form the patient interface 3000 includes at least one decoupling structure, for example, a swivel or a ball and socket.4.3.5 Connection port

[0291] Connection port 3600 allows for connection to the air circuit 4170.4.3.6 Forehead support

[0292] In one form, the patient interface 3000 includes a forehead support 3700.4.3.7 Anti-asphyxia valve

[0293] In one form, the patient interface 3000 includes an anti-asphyxia valve.4.3.8 Ports

[0294] In one form of the present technology, a patient interface 3000 includes one or more ports that allow access to the volume within the plenum chamber 3200. In one form this allows a clinician to supply supplementary oxygen. In one form, this allows for the direct measurement of a property of gases within the plenum chamber 3200, such as the pressure.4.4 AIR CIRCUIT WITH VENTING ARRANGEMENT

[0295] An air circuit 4170 in accordance with an aspect of the present technology includes a conduit or a tube constructed and arranged to allow, in use, a flow of air to travel between two components such as RPT device 4000 and the patient interface 3000.

[0296] In particular, the air circuit 4170 may be in fluid connection with the outlet of the pneumatic block 4020 of the RPT device and the patient interface 3000. The air circuit 4170 may be referred to as an air delivery tube.

[0297] In some forms, the air circuit 4170 may comprise one or more heating elements configured to heat air in the air circuit, for example to maintain or raise thetemperature of the air. The heating element may be in a form of a heated wire circuit, and may comprise one or more transducers, such as temperature sensors. In one form, the heated wire circuit may be helically wound around the axis of the air circuit 4170. The heating element may be in communication with a controller such as a central controller 4230. One example of an air circuit 4170 comprising a heated wire circuit is described in United States Patent 8,733,349, which is incorporated herewith in its entirety by reference.

[0298] Typically venting arrangements for the washout of exhaled gases (e.g., carbon dioxide) are located in a wall of the plenum chamber of the patient interface. In other words, venting of exhaled gases typically occurs at the patient interface. However, venting in such close proximity to a patient’s face or the patient’s bed partner can produce undesirable results. For example, the venting of gas washout can be noisy, and the exhausted air flow can be physically disruptive.

[0299] Accordingly, the air circuit 4170 may include a venting arrangement that allows for the washout of exhaled gases, e.g. carbon dioxide, at a location that is adjacent to or at the RPT device 4000 and is distal to the patient interface 3000. In certain forms the air circuit 4170 may be configured to allow a continuous vent flow from an interior of the plenum chamber 3200 to ambient whilst the pressure within the plenum chamber 3200 is positive with respect to ambient. The air circuit 4170 may be configured such that the vent flow rate has a magnitude sufficient to reduce rebreathing of exhaled CO2 by the patient while maintaining the therapeutic pressure in the plenum chamber in use.

[0300] It is contemplated that the air circuit 4170 with the venting arrangement is used with patient interfaces 3000 that lack their own venting arrangement.4.4.1 Tube in tube configuration4.4.1.1 Venting through the RPT device

[0301] Fig. 7A illustrates an exemplary air circuit 4170 in which a conduit 6002 has a double tube configuration. In other words, the conduit 6002 of the air circuit 4170 may include more than one gas flow path. In the configuration illustrated in Fig.7A, a venting tube 6004 may be positioned within the conduit 6002 so that the conduit 6002 and the venting tube 6004 are concentric. The space between the venting tube 6004 and the wall of the conduit 6002 may form a first gas flow path 6006 through which a supply of pressurized gas generated by the pressure generator 4140 may beconveyed to the patient interface 3000. The lumen in the venting tube 6004 may form a second gas flow path 6008 through which gas washout may be conveyed from the patient interface 3000 to a vent outlet 6024 of the RPT device 4000.

[0302] The conduit 6002 may be in the form of a flexible tube. In addition, the conduit 6002 may be axially extendible and / or retractable. The extensibility and retractability of the conduit 6002 may be independent of the venting tube 6004 so that the extending or retracting of the conduit 6002 does not change the length of the venting tube 6004. Alternatively, the venting tube 6004 may retract and extend with the conduit 6002.

[0303] One end of the conduit 6002 may connect to an outlet 6010 of the RPT device 4000 and an opposite end of the conduit 6002 may connect to an inlet or connection port 3600 of the patient interface 3000. It is contemplated that the conduit 6002 may be releasably connected to both the patient interface 3000 and the RPT device 4000. Alternatively, the conduit 6002 may be permanently connected to the patient interface 3000 and / or the RPT device 4000. In addition, the connection between the conduit 6002 and the connection portion 3600 may be a swivel connection.

[0304] It is contemplated that both the venting tube 6004 and the conduit 6004 may swivel relative to the connection portion 3600 to create a double swivel action between the air circuit 4170 and the patient interface 3000. The connection between the air circuit 4170 and the patient interface 3000 may be such that the venting tube 6004 and the conduit 6002 are radially locked relative to each other so that they swivel together. That is, the swivel actions of the venting tube 6004 and the conduit 6002 are not independent of each other. Alternatively, the swivel connection may be such that the venting tube 6004 does not rotate with the conduit 6002 or vice versa. Either the venting tube 6004 or the conduit 6002 may be rotatably locked with the swivel connection so that the venting tube 6004 or the conduit 6002 does not swivel relative to the patient interface 3000 while the other of the venting tube 6004 or the conduit 6002 is allowed to rotate. It is further contemplated that the swivel connection may be such that both the venting tube 6004 and the conduit 6002 are allowed to rotate but the swivel actions of the venting tube 6004 and the conduit 6002 are independent of each other.

[0305] The length of the conduit 6002 (when not extended or retracted) may be about 1.5 m to about 3.0 m (e.g., 1.8 m or 2 m). In addition, the inner diameter of theconduit 6002 may be consistent throughout its length. The inner diameter may be about 10 mm to about 25 mm (e.g., 12 mm, 14 mm, 19 mm, 20 mm, 22 mm).

[0306] Alternatively, the conduit 6002 may be tapered so that the inner diameter of the conduit 6002 decreases from one end to the other end. For example, the inner diameter of the conduit 6002 may taper toward the patient interface 3000 so that the inner diameter of the patient interface end of the conduit 6002 is smaller than the inner diameter of the flow generator end of the conduit 6002.

[0307] In the tapered configuration, the inner diameter of the conduit 6002 may be reduced at a rate that is a function of length. The inner diameter of the conduit 6002 at the flow generator connection end may be about 18 mm to about 25 mm (e.g., 19 mm, 20 mm, 22 mm), and the inner diameter of the conduit 6002 at the patient interface end may be about 10 mm to about 15 mm (e.g., 10 mm, 12 mm, 14 mm). It is contemplated that rather than a smooth, tapered transition to the smaller inner diameter, the transition to the smaller inner diameter may be made abruptly in one or more steps.

[0308] In addition, the inner diameter of the conduit 6002 and / or the rate of change of the inner diameter may be chosen to achieve a desired circuit impedance. Reducing the inner diameter of the conduit 6002 toward the patient interface 3000 may allow for a lower pressure drop across the conduit 6002 for any particular flow rate, while still reducing the overall diameter (including outer diameter) of the conduit 6002 at the patient interface end. This may be desirable for aesthetics as well as comfort.

[0309] Fig. 7B illustrates an exemplary conduit 6002 with a first cuff 6014 configured to connect to an elbow, connector, and / or an inlet of the patient interface 3000, a second cuff 6016 configured to connect to an outlet of a humidifier or an outlet of the RPT device 4000, and a main body 6018 that extends from the first cuff 6014 to the second cuff 6016. The conduit 6002 may be heatable and may include a plurality of heating and sensing wires 6020 that are helically wound around the surface of the conduit (either on the outer surface or an inner surface of the conduit 6002).

[0310] Referring back to Fig. 7A, the venting tube 6004 may extend through the conduit 6002 so that the first gas flow path 6006 and the second gas flow path 6008 are concentric. In addition, the length of the venting tube 6004 may be greater than or less than the length of the conduit 6002 regardless of whether the conduit 6002 isextended, retracted, or in a neutral state. Fig. 7B shows that the venting tube 6004 may extend beyond the first cuff 6014. Although Fig. 7B shows the venting tube 6004 terminating at the connecting end of the second cuff 6016, it is contemplated that the venting tube 6004 may also extend beyond the second cuff 6016 of the conduit 6002. Alternatively, the venting tube 6004 may terminate prior to reaching the second cuff 6016.

[0311] Also, a transducer 4274 may be positioned adjacent to or within the second gas flow path 6008 inside the RPT device 4000. The transducer 4274 may include one or more sensors configured to measure the flow rate and / or pressure of the gas flowing through the second gas flow path 6008. It is contemplated that the flow rate and / or pressure of gas flowing through the first gas flow path 6006 may be adjusted based at least in part on the measurements taken by the transducer 4274 in or adjacent to the second gas flow path 6008.

[0312] At the patient interface end of the venting tube 6004, the venting tube 6004 may extend into the plenum chamber 3200 so that the venting tube 6004 is adjacent to the patient’s airways during use. Placing the end of the venting tube 6004 adjacent to the patient’s face may minimize dead space inside the plenum chamber 3200. In addition, the patient interface end of the venting tube 6004 may be flared to reduce velocity near the patient’s face, which allows the end of the venting tube 6004 to be positioned near the patient’s face without sacrificing patient comfort.

[0313] The flow generator end of the venting tube 6004 may connect to a venting conduit 6022 that is inside the RPT housing. It is contemplated that one end of the venting conduit 6022 may terminate at the outlet 6010 of the RPT device 4000 so that connecting the conduit 6002 to the RPT device 4000 also connects the venting tube 6004 to the venting conduit 6022 inside the RPT device 4000. It is contemplated that the venting tube 6004 may extend beyond the second cuff 6016, may terminate at the connection end of the second cuff 6016, or may terminate inside the second cuff 6016. For configurations in which the conduit 6002 is permanently attached to the RPT device 4000, the venting conduit 6022 may be an integrally formed extension of the venting tube 6004.

[0314] The venting conduit 6022 may extend through the RPT device 4000 to a vent outlet 6024 that is separate and distinct from the outlet 6010 so that the gas washout from the patient interface 3000 is vented to atmosphere at a location distal to the patient (i.e., at the vent outlet 6024 of the RPT housing). The vent outlet 6024 maybe an opening in a wall of the RPT housing or may extend beyond the walls of the RPT housing to a location outside of the RPT device 4000. In addition, the vent outlet 6024 may comprise a plurality of holes, for example, about 20 to about 80 holes, or about 40 to about 60 holes, or about 45 to about 55 holes.

[0315] In some forms, a diffuser may be provided at the vent outlet 6024. The diffuser may assist with limiting the decibel output from any of the patient interface 3000 (or any other patient interface). Specifically, the diffuser may assist in limiting the decibel level associated with air output from the patient interface 3000 (e.g., exhaled air), although the diffuser may limit the decibel level of at any point in the patient interface.

[0316] In certain forms, the diffuser may diffuse, and therefore slow, the exhaust gas exiting the plenum chamber 3200 and passing through the venting tube 6004 (or second gas flow path 6008). The diffuser may assist in avoiding jetting and associated discomfort to the patient and / or bed partner (e.g., noise caused by jetting against a pillow, sheets, bedclothes, etc.).

[0317] Venting the gas washout to atmosphere at the RPT device 4000 may reduce the volume of noise experienced by the patient and the patient’s bed partner due to the venting of the gas washout. Also, by venting the gas washout to atmosphere at a location distal to the patient interface 3000, the amount of dead space in the patient interface 3000 and in the vent system may be reduced or eliminated.

[0318] The venting tube 6004 may be made of a semi-permeable material that is permeable to moisture (e.g., water vapor) but not permeable to carbon dioxide. For example, the walls of the venting tube 6004 may be made of polydimethylsiloxane (PDMS), silicone hydrogels, other types of a hydrophilic silicone, or any other type of material with micropores that are larger than water molecules but smaller than carbon dioxide molecules. Such pores allow for water vapor to cross over from the second gas flow path 6008 into the first gas flow path 6006 without changing its state in order to humidify the pressurized supply gas flowing through the first gas flow path 6006. At the same time, the semi-permeable wall of the venting tube 6004 may be impermeable (or at least substantially impermeable) to carbon dioxide so that little or no carbon dioxide leaks from the second gas flow path 6008 into the first gas flow path 6006. In other words, the venting tube 6004 may function as a heat moister exchanger (HME) by collecting moisture from the vented gas washout and returning the collected moisture to the inspiratory gas flow path.

[0319] In addition, heat from the gas washout flowing through the second gas flow path 6008 may contribute to the heating of the pressurized supply gas flowing through the first gas flow path 6006. Thus, the double tube configuration may reduce the amount of power needed to heat the pressurized gas being supplied to the patient and may also reduce or eliminate the need for a humidifier to humidify the pressurized gas being supplied to the patient.

[0320] The venting tube 6004 may have a consistent inner diameter along its entire length. In addition, the inner diameter of the venting tube 6004 may be substantially smaller than the inner diameter of the conduit 6002. For example, the inner diameter of the venting tube 6004 may be about 4 mm to about 6 mm (e.g., about 5 mm). The large difference between inner diameters reduces the impact the venting tube 6004 may have on the pressure drop in the first gas flow path 6006.

[0321] Alternatively, the venting tube 6004 may be tapered so that the inner diameter decreases from the RPT end to the patient interface end. The rate of decrease in the inner diameter of the venting tube 6004 may match the rate of decrease of the inner diameter of the conduit 6002. Also, rather than a smooth, tapered transition to the smaller inner diameter, the transition to the smaller inner diameter may be made abruptly in one or more steps. Accordingly, the inner diameter of the conduit 6002 and / or the inner diameter of the venting tube 6004 may decrease from the RPT end toward the patient interface end. Although the smaller inner diameters toward the patient interface 3000 may increase impedance at that end, the lower impedance at the RPT end due to the larger inner diameters at that end may offset the increased impedance at the patient interface end.

[0322] The venting tube 6004 may be unsupported within the conduit 6002 so that the venting tube 6004 is allowed to freely move within the conduit 6002.Alternatively, the venting tube 6004 may be supported within the conduit 6002 by one or more supports 6026. Fig. 7C shows a cross-section of the air circuit 4170 in which the venting tube 6004 is supported by a set of three supports 6026 positioned radially around the venting tube 6004. The conduit 6002 may include one or more sets of supports 6026 positioned along the length of the conduit 6002. In addition, the supports 6026 may be in the form of an arm or other shape that extends from an inner surface of the conduit 6002 to an outer surface of the venting tube 6006. Thus, the one or more supports 6026 may traverse the first gas flow path 6006 in a direction substantially transverse to the direction of flow through the first gas flow path 6006. Itis contemplated that the supports 6026 may be angled toward the patient interface side or the RPT side of the conduit 6002. In addition, the supports 6026 may be rigid so that the venting tube 6004 and the wall of the conduit 6002 are positionally fixed relative to each other. Alternatively, the supports 6026 may be semi-rigid or flexible to allow for at least some movement of the venting tube 6004 relative to the wall of the conduit 6002.

[0323] It is contemplated that the venting tube 6004 may be allowed to rotate within the conduit 6002. For example, the supports 6026 may be positioned on a rotatable sleeve that is positioned on an inner surface of the conduit 6002 so that the sleeve may be rotatable relative to the conduit 6002. Alternatively, the supports 6026 may only engage the venting tube 6004 instead of being fixed to the venting tube 6004 (or may be fixed to the venting tube 6004 and not fixed to the inner surface of the radial wall of the conduit 6002). In this configuration, the venting tube 6004 may be rotatable relative to the supports 6026 (or the supports 6026 with the venting tube 6004 may be rotatable relative to the conduit 6002), and the supports 6026 may be positioned merely to maintain the space between the radial wall of the conduit 6002 and the radial wall of the venting tube 6004. Of course, in the configuration lacking supports 6026 (i.e., the configuration in which the venting tube 6004 is unsupported and is allowed to freely move within the conduit 6002), the venting tube 6004 may rotate, move in an axial direction, and / or move in a radial direction relative to the radial wall of the conduit 6002.

[0324] Fig. 7D illustrates a configuration in which the vent outlet 6024 includes a filter 6028. The filter may be configured to trap pathogens such as, for example, bacteria or viruses so that the amount of pathogens being expelled to atmosphere from the gas washout may be minimized (e.g., to a safe level) or eliminated.

[0325] Figs. 7E and 7F illustrate a configuration in which the first and second flow paths 6006 and 6008 are switched so that the first flow path 6006 is inside the second flow path 6006. In this configuration, the conduit 6002 may be replaced with a conduit 6030 and the venting tube 6004 may be replaced with a supply tube 6032.

[0326] Similar to the conduit 6002, the conduit 6030 may be in the form of a flexible tube. In addition, the conduit 6030 may be axially extendible and / or retractable. The extensibility and retractability of the conduit 6030 may be independent of the supply tube 6032 so that the extending or retracting of the conduit6030 does not change the length of the supply tube 6032. Alternatively, the supply tube 6032 may retract and extend with the conduit 6030.

[0327] One end of the conduit 6030 may connect to the outlet 6010 of the RPT device 4000 and an opposite end of the conduit 6030 may connect to the inlet or connection port 3600 of the patient interface 3000. It is contemplated that the conduit 6030 may be releasably connected to both the patient interface 3000 and the RPT device 4000. Alternatively, the conduit 6030 may be permanently connected to the patient interface 3000 and / or the RPT device 4000. In addition, the connection between the conduit 6030 and the connection portion 3600 may be a swivel connection.

[0328] It is contemplated that both the supply tube 6032 and the conduit 6030 may swivel relative to the connection portion 3600 to create a double swivel action between the air circuit 4170 and the patient interface 3000. The connection between the air circuit 4170 and the patient interface 3000 may be such that the supply tube 6032 and the conduit 6030 are radially locked relative to each other so that they swivel together. That is, the swivel actions of the supply tube 6032 and the conduit 6030 are not independent of each other. Alternatively, the swivel connection may be such that the supply tube 6032 does not rotate with the conduit 6030 or vice versa. Either the supply tube 6032 or the conduit 6030 may be rotatably locked with the swivel connection so that the supply tube 6032 or the conduit 6030 does not swivel relative to the patient interface 3000 while the other of the supply tube 6032 or the conduit 6030 is allowed to rotate. It is further contemplated that the swivel connection may be such that both the supply tube 6032 and the conduit 6030 are allowed to rotate but the swivel actions of the supply tube 6032 and the conduit 6030 are independent of each other.

[0329] The length of the conduit 6030 (when not extended or retracted) may be about 1.5 m to about 3.0 m (e.g., 1.8 m or 2 m). In addition, the inner diameter of the conduit 6030 may be consistent throughout its length. The inner diameter may be about 10 mm to about 25 mm (e.g., 12 mm, 14 mm, 19 mm, 20 mm, 22 mm).

[0330] Alternatively, the conduit 6030 may be tapered so that the inner diameter of the conduit 6030 decreases from one end to the other end. For example, the inner diameter of the conduit 6030 may taper toward the patient interface 3000 so that the inner diameter of the patient interface end of the conduit 6030 is smaller than the inner diameter of the flow generator end of the conduit 6030.

[0331] In the tapered configuration, the inner diameter of the conduit 6030 may be reduced at a rate that is a function of length. The inner diameter of the conduit 6030 at the flow generator connection end may be about 18 mm to about 25 mm (e.g., 19 mm, 20 mm, 22 mm), and the inner diameter of the conduit 6030 at the patient interface end may be about 10 mm to about 15 mm (e.g., 10 mm, 12 mm, 14 mm). It is contemplated that rather than a smooth, tapered transition to the smaller inner diameter, the transition to the smaller inner diameter may be made abruptly in one or more steps.

[0332] In addition, the inner diameter of the conduit 6030 and / or the rate of change of the inner diameter may be chosen to achieve a desired circuit impedance. Reducing the inner diameter of the conduit 6030 toward the patient interface 3000 may allow for a lower pressure drop across the conduit 6030 for any particular flow rate, while still reducing the overall diameter (including outer diameter) of the conduit 6030 at the patient interface end. This may be desirable for aesthetics as well as comfort.

[0333] The supply tube 6032 may extend through the conduit 6030 so that the first gas flow path 6006 and the second gas flow path 6008 are concentric. The supply tube 6032 may be made of a semi-permeable material that is permeable to moisture (e.g., water vapor) but not permeable to carbon dioxide. For example, the wall of the supply tube 6032 may be made of polydimethylsiloxane (PDMS), silicone hydrogels, other types of a hydrophilic silicone, or any other type of material with micropores that are larger than water molecules but smaller than carbon dioxide molecules. Such pores allow for water vapor to cross over from the second gas flow path 6008 into the first gas flow path 6006 without changing its state in order to humidify the pressurized supply gas flowing through the first gas flow path 6006. At the same time, the semi-permeable wall of the supply tube 6032 may be impermeable (or at least substantially impermeable) to carbon dioxide so that little or no carbon dioxide leaks from the second gas flow path 6008 into the first gas flow path 6006. In other words, the supply tube 6032 may function as a heat moister exchanger (HME) by collecting moisture from the vented gas washout and returning the collected moisture to the inspiratory gas flow path.

[0334] In addition, heat from the gas washout flowing through the second gas flow path 6008 may contribute to the heating of the pressurized supply gas flowing through the first gas flow path 6006. Thus, the double tube configuration may reducethe amount of power needed to heat the pressurized gas being supplied to the patient and may also reduce or eliminate the need for a humidifier to humidify the pressurized gas being supplied to the patient.

[0335] It is contemplated that in the configuration in which the first gas flow path 6006 is positioned inside the second gas flow path 6008, the outer wall of the conduit 6030 may also be permeable or semi-permeable to all for the selective transport of CO2 to atmosphere through the outer wall of the conduit 6030, while retaining nitrogen and / or water vapour (or moisture) inside the conduit 6030. In this configuration, the concentration of CO2 may diminish along the second gas flow path 6008 toward the RPT device 4000 as CO2 is lost to atmosphere. At a distance along the conduit 6030, the CO2 concentration in the second gas flow path (vent gas flow path) 6008 may be sufficiently low so that the gas mixture flowing through the second gas flow path 6008 may be fed back into the first gas flow path 6006 at or adjacent to the RPT device 4000. The gas mixture in the second gas flow path 6008 may be fed back into the first gas flow path 6006 at a higher than atmospheric pressure and higher than atmospheric humidity to increase the efficiency of the blower and humidification system. Air from atmosphere may still be provided to the first gas flow path 6006 by way of the inlet and blower 4142 of the RPT device 4000. The mixture of fresh air and recycled air from the second gas flow path 6008 may maintain a sufficient concentration of oxygen in the first gas flow path 6006. In some situations, the recycling system described above may be used to provide hypoxic therapy.

[0336] The permeable or semi-permeable outer wall of the conduit 6030 may be made of materials such as, for example, polymeric membranes (e.g., PDMS, polyimides), zeolites, mixed-matrix membranes, facilitated transport membranes, and graphene oxide membranes. Such materials can selectively allow CO2 to pass through while blocking water vapor and N2.

[0337] The supply tube 6032 may have a consistent inner diameter along its entire length. In addition, the inner diameter of the supply tube 6032 may be larger than the inner diameter of the venting tube 6004. That is the size of the inner diameter of the supply tube 6032 relative to the inner diameter of the conduit 6030 may be larger than the size of the inner diameter of the venting tube 6004 relative to the inner diameter of the conduit 6002. For example, the inner diameter of the supply tube 6032 may be about 8 mm to about 9 mm (e.g., about 8.5 mm).

[0338] Alternatively, the supply tube 6032 may be tapered so that the inner diameter decreases from the RPT end to the patient interface end. The rate of decrease in the inner diameter of the supply tube 6032 may match the rate of decrease of the inner diameter of the conduit 6030. Also, rather than a smooth, tapered transition to the smaller inner diameter, the transition to the smaller inner diameter may be made abruptly in one or more steps. Accordingly, the inner diameter of the conduit 6030 and / or the inner diameter of the supply tube 6032 may decrease from the RPT end toward the patient interface end. Although the smaller inner diameters toward the patient interface 3000 may increase impedance at that end, the lower impedance at the RPT end due to the larger inner diameters at that end may offset the increased impedance at the patient interface end.

[0339] The supply tube 6032 may be unsupported within the conduit 6030 so that the supply tube 6032 is allowed to freely move within the conduit 6030. Alternatively, the supply tube 6032 may be supported within the conduit 6030 by one or more supports 6026. Fig. 7F shows a cross-section of the air circuit 4170 in which the supply tube 6032 is supported by a set of three supports 6026 positioned radially around the supply tube 6032. The conduit 6030 may include one or more sets of supports 6026 positioned along the length of the conduit 6030. In addition, the supports 6026 may be in the form of an arm or other shape that extends from an inner surface of the conduit 6030 to an outer surface of the supply tube 6032. Thus, the one or more supports 6026 may traverse the second gas flow path 6008 in a direction substantially transverse to the direction of flow through the second gas flow path 6008. It is contemplated that the supports 6026 may be angled toward the patient interface side or the RPT side of the conduit 6030. In addition, the supports 6026 may be rigid so that the supply tube 6032 and the wall of the conduit 6030 are positionally fixed relative to each other. Alternatively, the supports 6026 may be semi-rigid or flexible to allow for at least some movement of the supply tube 6032 relative to the wall of the conduit 6030. It is contemplated that the supply tube 6032 may be allowed to rotate within the conduit 6030. For example, the supports 6026 may be positioned on a rotatable sleeve that is positioned on an inner surface of the conduit 6030 so that the sleeve may be rotatable relative to the conduit 6030. Alternatively, the supports 6026 may only engage the supply tube 6032 instead of being fixed to the supply tube 6032 (or may be fixed to the supply tube 6032 and not fixed to the inner surface of the radial wall of the conduit 6030). In this configuration, the supply tube 6032 may berotatable relative to the supports 6026 (or the supports 6026 with the supply tube 6032 may be rotatable relative to the conduit 6030), and the supports 6026 may be positioned merely to maintain the space between the radial wall of the conduit 6030 and the radial wall of the supply tube 6032. Of course, in the configuration lacking supports 6026 (i.e., the configuration in which the supply tube 6032 is unsupported and is allowed to freely move within the conduit 6030), the supply tube 6032 may rotate, move in an axial direction, and / or move in a radial direction relative to the radial wall of the conduit 6030.

[0340] Figs. 7G and 7H show an RPT end of the conduit 6030 that is configured to connect to the outlet 6010 of the RPT device 4000. In this configuration, the supply tube 6032 and the conduit 6030 are movable relative to each other in an axial direction.

[0341] Fig. 7G shows a condition of the conduit 6030 during the patient’s inspiration phase of breathing in which there is no carbon dioxide being delivered to the system. During this phase, the RPT end of the supply tube 6034 may be aligned with the terminal end of the second cuff 6016. In addition, the second cuff 6016 may include an end wall 6036 that covers an end of the second gas flow path 6008. In this configuration, the end of the second gas flow path 6008 may be sealed off by the supply tube 6032 and the end wall 6036 so that gas flow through the gas flow path 6008 is prevented. At the same time, the pressurized gas is allowed to flow through the supply tube 6032 to the patient interface 3000. It is contemplated that the supply tube 6032 may project beyond the end wall 6036.

[0342] Fig. 7H shows a condition of the conduit 6030 during the patient’s expiration phase of breathing. During this phase, the RPT end of the supply tube 6032 is axially moved away from the terminal end of the conduit (i.e., away from the RPT device 4000). The axial movement of the supply tube 6032 may create or increase a distance between the end of the supply tube 6032 and the end wall 6036, thereby leaving a gap 6040 between the end of the supply tube 6032 and the end wall 6036. Gas washout in the second gas flow path 6008 may flow through the gap 6040.

[0343] It is contemplated that axial movement of the supply tube 6032 may be actuated mechanically, electrically, or pneumatically. It is further contemplated that the size of the gap 6040 and the distance travelled by the supply tube 6032 may vary depending on the pressure in the patient interface 3000 during expiration. In addition, the supply tube 6032 may be positioned relative to the end wall 6036 so that the gap6040 exists regardless of the patient’s breathing phase. In this configuration, the gap 6040 would be smallest during inspiration and largest during expiration.

[0344] It is further contemplated that one or more springs may be positioned between the radial wall of the conduit 6030 and the radial wall of the supply tube 6032. Alternatively, one or more springs may be positioned at the end wall of the supply tube 6032 and the end wall 6036 of the second cuff 6016. The pressure difference between the first flow path 6006 and the second flow path 6008 may work against the retracting force of the one or more springs to allow the supply tube 6032 to automatically react to inspiratory and expiratory gas flows. For example, as the patient inhales, the RPT device 4000 may increase pressure to maintain pressure in the plenum chamber 3200 so that the pressure in the first gas flow path 6006 increases, thereby forcing the supply tube 6032 to move axially toward the end wall 6036 of the second cuff 6016 and reduce or terminate vent flow. As the patient breathes out, the pressure in the system may drop, and the one or more springs may push the supply tube 6032 away from the end wall 6036 of the second cuff 6016, thereby opening up or increasing the gap 6040 and opening or increasing the second gas flow path 6008. It is contemplated that the structure described above may be located at the first cuff 6014 or at both cuffs 6014, 6016.

[0345] Figs. 7I-7J illustrate alternative conduit cross-sections. Rather than contain a separate tubular structure inside the conduit, the configurations illustrated in Figs. 71 and 7J comprise one single conduit with an internal wall that creates two separate gas flow passages that are located in a side-by-side configuration. The structure of the conduit 6042 is similar to the conduit 6002 except, the conduit 6042 contains an internal wall 6044 that divides the lumen in the conduit 6042 into the first gas flow path 6006 and the second gas flow path 6008.

[0346] Similar to the previously disclosed conduits, the conduit 6042 may have a consistent inner diameter or a tapered structure in which the inner diameter decreases toward the patient interface 3000. In addition, the internal wall 6044 may be straight or curved. The internal wall 6044 may be positioned so that the cross-sectional area of the second gas flow path 6008 is substantially smaller than the cross-sectional area of the first gas flow path 6006 similar to the configuration in the previously disclosed conduits 6002, 6030. In addition, similar to the walls of the venting tube 6004 and the supply tube 6032, the internal wall 6044 may be formed from a semi-permeable material that is permeable to moisture (e.g., water vapor) but not permeable to carbondioxide. For example, the internal wall 6044 may be made of polydimethyl siloxane (PDMS), silicone hydrogels, other types of a hydrophilic silicone, or any other type of material with micropores that are larger than water molecules but smaller than carbon dioxide molecules. Such pores allow for water vapor to cross over from the second gas flow path 6008 into the first gas flow path 6006 without changing its state in order to humidify the pressurized supply gas flowing through the first gas flow path 6006. At the same time, the semi-permeable internal wall 6044 may be impermeable (or at least substantially impermeable) to carbon dioxide so that little or no carbon dioxide leaks from the second gas flow path 6008 into the first gas flow path 6006.

[0347] It should be understood that other structural features described above for the conduits 6002 and 6030 may be incorporated into the conduit 6042 (e.g., heating and sensing wires and retractability).4.4.1.2 Venting adjacent to the RPT device

[0348] It is contemplated that all of the above disclosed conduits can be used with RPT devices 4000 with the venting structure illustrated in Fig. 7A. Figs. 7K and 7L illustrate a conduit 6046 that can be used with conventional RPT devices 4000 that lack the venting structure illustrated in Fig. 7A.

[0349] Similar to the conduit 6002, the conduit 6046 may be in the form of a flexible tube. In addition, the conduit 6046 may be axially extendible and / or retractable. One end of the conduit 6046 may connect to an outlet 6010 of the RPT device 4000 and an opposite end of the conduit 6046 may connect to an inlet or connection port 3600 of the patient interface 3000. It is contemplated that the conduit 6046 may be releasably connected to both the patient interface 3000 and the RPT device 4000. Alternatively, the conduit 6002 may be permanently connected to the patient interface 3000. In addition, the connection between the conduit 6046 and the connection portion 3600 may be a swivel connection.

[0350] The length of the conduit 6046 (when not extended or retracted) may be about 1.5 m to about 3.0 m (e.g., 1.8 m or 2 m). In addition, the inner diameter of the conduit 6046 may be consistent throughout its length. The inner diameter may be about 10 mm to about 25 mm (e.g., 12 mm, 14 mm, 19 mm, 20 mm, 22 mm).Alternatively, the conduit 6046 may be tapered or have a varied inner diameter in a manner similar to what is discussed above for the conduit 6002. Also, the conduit 6046 may include heating and sensing wires as well as first and second cuffs 6014 and 6016.

[0351] The venting tube 6048 may extend through the conduit 6046 so that the first gas flow path 6006 and the second gas flow path 6008 are concentric. In addition, the length of the venting tube 6048 may be greater than the length of the conduit 6046 regardless of whether the conduit 6046 is extended, retracted, or in a neutral state. Fig.7K shows that the patient interface end of the venting tube 6048 may extend beyond the first cuff 6014 and into the plenum chamber 3200.

[0352] Similar to the venting tube 6004, the venting tube 6048 may be made of a semi-permeable material that is permeable to moisture (e.g., water vapor) but not permeable to carbon dioxide. For example, the wall of the venting tube 6048 may be made of polydimethylsiloxane (PDMS), silicone hydrogels, other types of a hydrophilic silicone, or any other type of material with micropores that are larger than water molecules but smaller than carbon dioxide molecules. Such pores allow for water vapor to cross over from the second gas flow path 6008 into the first gas flow path 6006 without changing its state in order to humidify the pressurized supply gas flowing through the first gas flow path 6006. At the same time, the semi-permeable wall of the venting tube 6048 may be impermeable (or at least substantially impermeable) to carbon dioxide so that little or no carbon dioxide leaks from the second gas flow path 6008 into the first gas flow path 6006. In other words, the venting tube 6048 may function as a heat moister exchanger (HME) by collecting moisture from the vented gas washout and returning the collected moisture to the inspiratory gas flow path.

[0353] In addition, heat from the gas washout flowing through the second gas flow path 6008 may contribute to the heating of the pressurized supply gas flowing through the first gas flow path 6006. Thus, the double tube configuration may reduce the amount of power needed to heat the pressurized gas being supplied to the patient and may also reduce or eliminate the need for a humidifier to humidify the pressurized gas being supplied to the patient.

[0354] The dimensions of the venting tube 6048 may be similar to the dimensions discussed above for the venting tube 6004. In addition, similar to the venting 6004, the venting tube 6048 may have a consistent or varied inner diameter.

[0355] The conduit 6046 may also include an adaptor 6050 positioned at the RPT end of the conduit 6046. The adaptor 6050 may be connected to the second cuff 6016 and may replace the second cuff 6016 as the component that connects to the outlet 6010 of the RPT device 4000. The adaptor 6050 may be configured to connect to thesecond cuff 6016 in a similar manner as the outlet 6010 of the RPT device 4000 would connect to the second cuff 6016. For example, the adaptor 6050 may connect to the second cuff 6016 by way of an interlocking mechanism, or by way of an interference fit.

[0356] The adaptor 6050 may include an inlet 6052 configured to connect to the outlet 6010 of the RPT device 4000 and an outlet 6054 configured to exhaust the gas washout to atmosphere. The inlet 6052 may be part of the first gas flow path 6006. The outlet 6054 may be fluidly connected to the venting tube 6048 and may be part of the second gas flow path 6008. It is contemplated that the venting tube 6048 may terminate within the adaptor 6050 or may extend beyond the outlet 6054 to ensure that the gas washout does not flow back into the adaptor 6050. This configuration allows existing masks to be retrofit so that venting of the gas washout occurs distal to the patient interface 3000. In this case, the venting of the gas washout occurs adjacent to the RPT device 4000 but does not flow through the RPT device 4000.4.5 PATIENT INTERFACE WITH VENTING TUBE

[0357] Figs. 7M-7S illustrate exemplary patient interfaces 3000 with a connector 6056. Similar to the patient interface 3000 illustrated in Fig. 3E, the patient interface 3000 may convey pressurized air to the patient’s nose and the patient’s mouth. The patient interface 3000 may include a seal-forming structure attached to a plenum chamber 3200. A shroud 3210 may be removably attachable to the walls of the plenum chamber 3200. The point of connection between the plenum chamber 3200 and the shroud 3210 may be at the inlets 3220, 3230. The shroud 3210 may be secured to the walls of the plenum chamber 3200 to the walls of the plenum chamber 3200 by a snap fit connection or any other arrangement capable of retaining the shroud 3210 to the plenum chamber 3200 during use. It is contemplated that the shroud 3210 may be as rigid as the walls of the plenum chamber 3200 or more rigid than the walls of the plenum chamber 3200.

[0358] The positioning and stabilizing structure 3300 may be secured to the plenum chamber 3200 and seal-forming structure 3100. For example, the shroud 3210 may include rigidizers 3340 and headgear connectors 3341 that are attachable to headgear straps of the positioning and stabilizing structure 3300. In addition, sleeves 3351 may be wrapped around the rigidizers 3340.

[0359] A connector 6056 configured to connect any of the conduits 6002, 6030, 6042, or 6046 to the patient interface 3000. Although the connector 6056 is shown asan elbow, the connector 6056 can be in any form capable of connecting the air circuit 4170 to the patient interface 3000. In addition, the connector 6056 may be secured to the inlet portion 3230 of the shroud 3210 prior to being secured to the inlet port 3220 of the plenum chamber 3200 (Fig. 7N) or may be secured to the inlet port 3230 of the shroud 3210 and / or the inlet port 3220 of the plenum chamber 3200 after the shroud 3210 is secured to the plenum chamber 3200 (Fig. 70)

[0360] As illustrated in Figs. 7P and 7Q, the connector 6056 has a conduit connecting end 6058 configured to connect to a conduit and a patient interface connecting end 6060 configured to connect to the patient interface 3000. The patient interface connecting end 6060 may include a clip 6062 or other locking device to secure the connector 6056 to the patient interface 3000. A lumen extending through the connector 6056 from the conduit connecting end 6058 to the patient interface connecting end 6060 may form part of the first gas flow path 6006.

[0361] A venting tube 6064 may extend through the lumen of the connector 6056 and may be part of the second gas flow path 6008. Similar to the venting tube 6004, the venting tube 6064 may be flexible, and may be made of a semi-permeable material that is permeable to moisture (e.g., water vapor) but not permeable to carbon dioxide. For example, the walls of the venting tube 6064 may be made of polydimethylsiloxane (PDMS), silicone hydrogels, other types of a hydrophilic silicone, or any other type of material with micropores that are larger than water molecules but smaller than carbon dioxide molecules. Such pores allow for water vapor to cross over from the second gas flow path 6008 into the first gas flow path 6006 without changing its state in order to humidify the pressurized supply gas flowing through the first gas flow path 6006. At the same time, the semi-permeable wall of the venting tube 6004 may be impermeable (or at least substantially impermeable) to carbon dioxide so that little or no carbon dioxide leaks from the second gas flow path 6008 into the first gas flow path 6006. In other words, the venting tube 6064 may function as a heat moister exchanger (HME) by collecting moisture from the vented gas washout and returning the collected moisture to the inspiratory gas flow path.

[0362] In addition, the venting tube 6064 may extend beyond the patient interface connecting end 6060 of the connector 6056 so that the venting tube 6064 extends into the plenum chamber 3200 and an end of the venting tube 6064 is adjacent to an entrance of the patient’s airways (see Fig. 7R). In addition, the end of the venting tube6064 may be flared to allow the venting tube 6064 to be positioned close to the patient’s airways with minimal discomfort to the patient. The venting tube 6064 may also extend beyond the conduit connecting end 6058 of the connector 6056 and may connect to the venting tube in the conduit 6002, 6030, 6042, or 6046. Accordingly, the length of the venting tube 6064 may be greater than the length of the lumen in the connector 6056.

[0363] Also, the venting tube 6064 may be allowed to freely move within the lumen of the connector 6056. Alternatively, the venting tube 6064 may be held in place within the connector 6056 by one or more supports extending from the inner wall of the connector 6056. It is further contemplated that the venting tube 6064 may be rigid or semi-rigid instead of flexible.

[0364] It should be understood that although the connector 6056 is shown being used with a nose and mouth cushion, it should be understood that the connector 6056 may also be used with a nose only cushion such as the ones illustrated in Figs. 3 A and 3B. In addition, it is contemplated that the plenum chamber 3200 and the connector 6056 lack a vent outlet, vent openings, or any other feature that would vent gas washout to atmosphere. Instead, the gas washout is routed through the connector 6056 and through the air circuit 4170 to a feature adjacent to or within the RPT device 4000 that vents the gas washout to atmosphere so that the gas washout is vented to atmosphere at a location distal to the patient interface 3000 and the connector 6056 (i.e., at or adjacent to the RPT device 4000).

[0365] In some embodiments, an inlet connection of the patient interface 3000 or the connector 3610 may be compatible with CPAP tubing that connects to the patient interface according to an industry standard connection, such as the conical connector (22 mm / 15 mm) meeting ISO 5356-1:2015 specifications. However, connecting a non-vented patient interface to a standard non-vented CPAP tube may be undesirable due to the possibility of high, and unsatisfactory CO2 levels building up in the respiratory circuit.

[0366] Accordingly, as shown in Figs. 7S-7U, a patient interface connector 6074 may be provided that may be adapted to function with vented and non-vented air circuits 4170. The connector 6074 may be integrally formed with the patient interface 3000 or may be removably connected to the patient interface. It is contemplated that the connector 6074 may be configured to connect to the elbow 3610 or the swivel connector 3600. In addition, the connector 6074 may itself be in the form of an elbow.

[0367] The connector 6074 may comprise a non-standard portion 6076 and a standard portion 6078. The non-standard portion 6076 may be the part of the connector 6074 that connects to the patient interface 3000. The non-standard portion 6076 may be configured to connect to conventional vented and non-vented patient interfaces and / or patient interfaces designed to be used with vented air circuits. The non-standard portion 6076 may include one or more vent holes 6080. Figs. 7S-7U show the vent holes 6080 being arranged in a single row around the circumference of the non-standard portion 6076. However, the vent holes 6080 may be arranged in any configuration sufficient to vent gas washout from the patient interface 3000 when a non-vented conduit is attached to the connector 6074.

[0368] The standard portion 6078 may be positioned upstream from the nonstandard portion 6076 (with respect to direction in which pressurized gas is being supplied to the patient interface 3000) (downstream from the non-standard portion 6076 with respect to the direction in which the gas washout is vented from the patient interface 3000). In addition, the standard portion 6078 and the non-standard portion 6076 may be axially aligned so that they share the same central longitudinal axis. The diameter of the standard portion 6078 may be smaller than the diameter of the nonstandard portion 6076. This may create a shoulder or ledge 6082 between the standard portion 6078 and the non-standard portion 6076. In addition, the standard portion 6078 may have a conical or tapered shape with a larger diameter at the standard portion end and a smaller diameter at the conduit connector end.

[0369] As shown in Fig. 7S, a non-vented conduit 6084 (i.e., a conduit without a venting arrangement or vent flow path) connects to the standard portion 6078 so that when the non-vented conduit 6084 is fully secured to the connector 6074, the vent holes 6080 remain uncovered, thereby allowing the gas washout to be expelled to atmosphere through the connector 6074. The conical shape of the standard portion 6078 may allow the standard portion 6078 to be received within a cuff 6086 of the conduit 6084. The increasing diameter of the standard portion 6078 may allow the cuff 6086 to easily slide over the outside of the standard portion 6078 until the cuff 6086 is secured to the standard portion 6078 by friction. As can be seen, the cuff 6086 may not reach the nonstandard portion 6076, which leaves the vent holes 6080 uncovered. It is contemplated that the cuff 6086 may abut against the shoulder 6082 when the cuff 6086 is fully secured to the connector 6074. This way the shoulder 6082 and / or friction may limit movement of the cuff 6086 toward the non-standardportion 6076. It is further contemplated that the diameter of the standard portion 6078 may be sized relative to the inner diameter of the conduit 6084 so that the diameter increases (toward the non-standard portion side) to a size that is larger than the inner diameter of the conduit 6084 and prevents the cuff 6086 from reaching the shoulder 6082.

[0370] Figs. 7T and 7U illustrate the connector 6074 being connected to a venting conduit 6088. The venting conduit 6088 may be configured to engage both the standard portion 6078 and the non-standard portion 6076 so that when the venting conduit 6088 is secured to the connector 6074, the vent holes 6080 are covered by the cuff 6090 of the conduit 6088.

[0371] The cuff 6090 may include a vent occluding section 6092 and a standard portion engaging section 6094. The inner diameter of the vent occluding section 6092 may be larger than the inner diameter of the standard portion engaging section 6094 to mirror the relationship between the diameters of the non-standard portion 6076 and the standard portion 6078. When secured to the connector 6074, the vent occluding section 6092 of the cuff 6090 covers the vent holes 6080 so that the gas washout flows through the cuff 6090 and into the venting conduit 6088 instead of being vented to atmosphere through the connector 6074. The cuff 6090 may also include a shoulder 6096 that acts as a transition from the standard portion engaging section 6094 to the vent occluding section 6092. The cuff 6090 may be configured so that the shoulder 6096 abuts the shoulder 6082 of the connector 6074 when the cuff 6090 is secured to the connector 6074.

[0372] The cuff 6090 may also include a venting tube 6098 that extends into the connector 6074 when the cuff 6090 is connected and secured to the connector 6074. The venting tube 6098 may extend through the venting conduit 6088 or may be connected to a larger venting tube that extends through the venting conduit 6088. In addition, the venting tube 6098 may be long enough to extend beyond the nonstandard portion 6076 of the connector 6074 when the cuff 6090 is secured to the connector 6074. The venting tube 6098 may have the same properties and may be made from the same materials as the venting tubes previously disclosed. Also, the venting tube 6098 may be allowed to freely move within the cuff 6090. Alternatively, the venting tube 6098 may be fixed in place within the cuff 6090 in a manner similar to the way the previously disclosed venting tubes are fixed in place within their respective conduits.

[0373] Fig. 7V illustrates another configuration that utilizes one or more headgear tubes 3350 that deliver pressurised air received from a conduit forming part of the air circuit 4170 from the RPT device 4000 to the patient’s airways through the plenum chamber 3200 and seal -forming structure 3100. In the form of the present technology illustrated in Fig. 7S, the positioning and stabilising structure 3300 comprises the two tubes 3350 that deliver air to the plenum chamber 3200 from the air circuit 4170. The tubes 3350 are configured to position and stabilise the sealforming structure 3100 of the patient interface 3000 at the appropriate part of the patient’s face (for example, the nose and / or mouth) in use. This allows the conduit of air circuit 4170 providing the flow of pressurised air to connect to a connection port 3600 of the patient interface in a position other than in front of the patient’s face, for example on top of the patient’s head.

[0374] Each headgear tube 3350 may include an interior wall 6066 that divides the corresponding headgear tube 3350 and forms a first gas flow path 6068 and a second gas flow path 6070. Similar to the first and second gas flow paths 6006 and 6008, the first gas flow path 6068 may have a substantially larger cross-section than the second gas flow path 6070. In addition, the first gas flow path 6068 may supply pressurized gas from the RPT device 4000 to the plenum chamber 3200. In addition, the second gas flow path 6070 may convey gas washout from the plenum chamber 3200 to the connector 6072. Although the connector 6072 is shown as an elbow, the connector 6072 may be any structure capable of connecting to an air delivery tube or conduit.

[0375] In one configuration, the gas washout in the second gas flow path 6070 may be vented to atmosphere through one or more vent openings in the connector 6072. Alternatively, the connector 6072 may include a pair of gas flow paths that respectively connect to the first and second gas flow paths 6068 and 6070 and may connect to any one of the conduits disclosed above. It is contemplated that the connector 6072 may lack vent openings and the gas washout is conveyed toward the RPT 4000 in a manner similar to that discussed above for the other air circuits with venting arrangements. That is, the gas washout may be vented to atmosphere only at the connector 6072, vented to atmosphere at both the connector 6072 and the RPT device 4000, or vented to atmosphere only at or adjacent to the RPT device 4000. It should be understood that the plenum chamber 3200 lacks any venting feature that would allow gas washout to be vented to atmosphere at the plenum chamber 3200.

[0376] The dividing wall 6066 may be made of a semi-permeable material that is permeable to moisture (e.g., water vapor) but not permeable to carbon dioxide. For example, the dividing wall 6066 may be made of polydimethylsiloxane (PDMS), silicone hydrogels, other types of a hydrophilic silicone, or any other type of material with micropores that are larger than water molecules but smaller than carbon dioxide molecules. Such pores allow for water vapor to cross over from the second gas flow path 6070 into the first gas flow path 6068 without changing its state in order to humidify the pressurized supply gas flowing through the first gas flow path 6068. At the same time, the semi-permeable dividing wall 6066 may be impermeable (or at least substantially impermeable) to carbon dioxide so that little or no carbon dioxide leaks from the second gas flow path 6070 into the first gas flow path 6068. In other words, the dividing wall 6066 may function as a heat moister exchanger (HME) by collecting moisture from the vented gas washout and returning the collected moisture to the inspiratory gas flow path.

[0377] In addition, heat from the gas washout flowing through the second gas flow path 6070 may contribute to the heating of the pressurized supply gas flowing through the first gas flow path 6068. Thus, the double tube configuration may reduce the amount of power needed to heat the pressurized gas being supplied to the patient and may also reduce or eliminate the need for a humidifier to humidify the pressurized gas being supplied to the patient.

[0378] It should be understood that although the dividing wall 6066 and the connector 6072 are shown being used with a nose only cushion, it should be understood that the dividing wall 6066 and the connector 6072 may also be used with a nose and mouth cushion such as the ones illustrated in Figs. 3F and 3G.

[0379] In some embodiments, the patient interface 3000 and the air circuit 4170 may form a hybrid venting system in which the walls of the plenum chamber 3200 and / or the walls of the connector 3610 include vent openings in addition to the air circuit 4170 including a conduit with a gas washout flow path that conveys gas washout toward the RPT device 4000 so that gas washout is vented to atmosphere at the patient interface 3000 and at or adjacent to the RPT device 4000 (i.e., fully proximal and fully distal venting relative to the patient interface 3000). In this configuration, venting at the mask may be supplemented by in-tube venting in the air circuit 4170. This may allow for reduced venting at the patient interface 3000, whichwould reduce the level of disturbance caused by venting at the mask and would allow for a reduced conduit diameter and impedance within the air circuit 4170.4.6 RPT DEVICE

[0380] An RPT device 4000 in accordance with one aspect of the present technology comprises mechanical, pneumatic, and / or electrical components and is configured to execute one or more algorithms 4300, such as any of the methods, in whole or in part, described herein. The RPT device 4000 may be configured to generate a flow of air for delivery to a patient’s airways, such as to treat one or more of the respiratory conditions described elsewhere in the present document.

[0381] In one form, the RPT device 4000 is constructed and arranged to be capable of delivering a flow of air in a range of -20 L / min to +150 L / min while maintaining a positive pressure of at least 4 cmH20, or at least 10cmH2O, or at least 20 cmH20.

[0382] The RPT device 4000 may have an external housing 4010, formed in two parts, an upper portion 4012 and a lower portion 4014. Furthermore, the external housing 4010 may include one or more panel(s) 4015. The RPT device 4000 comprises a chassis 4016 that supports one or more internal components of the RPT device 4000. The RPT device 4000 may include a handle 4018.

[0383] The pneumatic path of the RPT device 4000 may comprise one or more air path items, e.g., an inlet air filter 4112, an inlet muffler 4122, a pressure generator 4140 capable of supplying air at positive pressure (e.g., a blower 4142), an outlet muffler 4124 and one or more transducers 4270, such as pressure sensors 4272 and flow rate sensors 4274.

[0384] One or more of the air path items may be located within a removable unitary structure which will be referred to as a pneumatic block 4020. The pneumatic block 4020 may be located within the external housing 4010. In one form a pneumatic block 4020 is supported by, or formed, as part of the chassis 4016.

[0385] The pneumatic block 4020 may include a gas flow path that is an extension of or is a part of the first gas flow path 6006 disclosed above. In addition, the external housing 4010 and / or the chassis 4016 may enclose a part of or an extension of the second gas flow path 6008 as disclosed above.

[0386] As shown in Fig. 4C, the RPT device 4000 may have an electrical power supply 4210, one or more input devices 4220, a central controller 4230, a therapy device controller 4240, a pressure generator 4140, one or more protection circuits4250, memory 4260, transducers 4270, data communication interface 4280 and one or more output devices 4290. Electrical components 4200 may be mounted on a single Printed Circuit Board Assembly (PCBA) 4202. In an alternative form, the RPT device 4000 may include more than one PCBA 4202.4.6.1 RPT device mechanical & pneumatic components

[0387] An RPT device 4000 may comprise one or more of the following components in an integral unit. In an alternative form, one or more of the following components may be located as respective separate units.4.6.1.1 Air filter (s)

[0388] An RPT device in accordance with one form of the present technology may include an air filter 4110, or a plurality of air filters 4110.

[0389] In one form illustrated in Fig. 4B, an inlet air filter 4112 is located at the beginning of the pneumatic path upstream of a pressure generator 4140.

[0390] In one form illustrated in Fig. 4B, an outlet air filter 4114, for example an antibacterial filter, is located between an outlet of the pneumatic block 4020 and a patient interface 3000.4.6.1.2 Muffler(s)

[0391] An RPT device in accordance with one form of the present technology may include a muffler 4120, or a plurality of mufflers 4120.

[0392] In one form of the present technology (see e.g., Fig. 4B), an inlet muffler 4122 is located in the pneumatic path upstream of a pressure generator 4140.

[0393] In one form of the present technology, an outlet muffler 4124 is located in the pneumatic path between the pressure generator 4140 and a patient interface 3000.4.6.1.3 Pressure generator

[0394] In one form of the present technology, a pressure generator 4140 for producing a flow, or a supply, of air at positive pressure is a controllable blower 4142. For example, the blower 4142 may include a brushless DC motor 4144 with one or more impellers. The impellers may be located in a volute. The blower may be capable of delivering a supply of air, for example at a rate of up to about 120 litres / minute, at a positive pressure in a range from about 4 cmH20 to about 20 cmH20, or in other forms up to about 30 cmH20 when delivering respiratory pressure therapy. The blower may be as described in any one of the following patents or patent applications the contents of which are incorporated herein by reference in their entirety: U.S.Patent No. 7,866,944; U.S. Patent No. 8,638,014; U.S. Patent No. 8,636,479; and PCT Patent Application Publication No. WO 2013 / 020167.

[0395] The pressure generator 4140 may be under the control of the therapy device controller 4240.

[0396] In other forms, a pressure generator 4140 may be a piston-driven pump, a pressure regulator connected to a high pressure source (e.g. compressed air reservoir), or a bellows.4.6.1.4 Transducer(s)

[0397] Transducers may be internal of the RPT device, or external of the RPT device. External transducers may be located for example on or form part of the air circuit, e.g., the patient interface. External transducers may be in the form of noncontact sensors such as a Doppler radar movement sensor that transmit or transfer data to the RPT device.

[0398] In one form of the present technology (see e.g., Fig. 4B), one or more transducers 4270 are located upstream and / or downstream of the pressure generator 4140. The one or more transducers 4270 may be constructed and arranged to generate signals representing properties of the flow of air such as a flow rate, a pressure or a temperature at that point in the pneumatic path.

[0399] In one form of the present technology, one or more transducers 4270 may be located proximate to the patient interface 3000.

[0400] In one form, a signal from a transducer 4270 may be filtered, such as by low-pass, high-pass or band-pass filtering.4.6.1.4.1 Flow rate sensor

[0401] A flow rate sensor 4274 in accordance with the present technology may be based on a differential pressure transducer, for example, an SDP600 Series differential pressure transducer from SENSIRION.

[0402] In one form, a signal generated by the flow rate sensor 4274 and representing a flow rate is received by the central controller 4230.4.6.1.4.2 Pressure sensor

[0403] A pressure sensor 4272 in accordance with the present technology is located in fluid communication with the pneumatic path. An example of a suitable pressure sensor is a transducer from the HONEYWELL ASDX series. An alternative suitable pressure sensor is a transducer from the NPA Series from GENERAL ELECTRIC.

[0404] In one form, a signal generated by the pressure sensor 4272 and representing a pressure is received by the central controller 4230.4.6.1.4.3 Motor speed transducer

[0405] In one form of the present technology a motor speed transducer 4276 is used to determine a rotational velocity of the motor 4144 and / or the blower 4142. A motor speed signal from the motor speed transducer 4276 may be provided to the therapy device controller 4240. The motor speed transducer 4276 may, for example, be a speed sensor, such as a Hall effect sensor.4.6.1.5 Anti-spill back valve

[0406] As shown in Fig. 4B, one form of the present technology, an anti-spill back valve 4160 is located between the humidifier 5000 and the pneumatic block 4020. The anti-spill back valve is constructed and arranged to reduce the risk that water will flow upstream from the humidifier 5000, for example to the motor 4144.4.6.2 RPT device electrical components4.6.2.1 Power supply

[0407] A power supply 4210 may be located internal or external of the external housing 4010 of the RPT device 4000.

[0408] In one form of the present technology, power supply 4210 provides electrical power to the RPT device 4000 only. In another form of the present technology, power supply 4210 provides electrical power to both RPT device 4000 and humidifier 5000.4.6.2.1 Input devices

[0409] In one form of the present technology, an RPT device 4000 includes one or more input devices 4220 in the form of buttons, switches or dials to allow a person to interact with the device. The buttons, switches or dials may be physical devices, or software devices accessible via a touch screen. The buttons, switches or dials may, in one form, be physically connected to the external housing 4010, or may, in another form, be in wireless communication with a receiver that is in electrical connection to the central controller 4230.

[0410] In one form, the input device 4220 may be constructed and arranged to allow a person to select a value and / or a menu option.4.6.1.3 Central controller

[0411] In one form of the present technology, the central controller 4230 is one or a plurality of processors suitable to control an RPT device 4000. The central controller 4230 is show in Fig. 4C.

[0412] Suitable processors may include an x86 INTEL processor, a processor based on ARM® Cortex®-M processor from ARM Holdings such as an STM32 series microcontroller from ST MICROELECTRONIC. In certain alternative forms of the present technology, a 32-bit RISC CPU, such as an STR9 series microcontroller from ST MICROELECTRONICS or a 16-bit RISC CPU such as a processor from the MSP430 family of microcontrollers, manufactured by TEXAS INSTRUMENTS may also be suitable.

[0413] In one form of the present technology, the central controller 4230 is a dedicated electronic circuit.

[0414] In one form, the central controller 4230 is an application-specific integrated circuit. In another form, the central controller 4230 comprises discrete electronic components.

[0415] The central controller 4230 may be configured to receive input signal(s) from one or more transducers 4270, one or more input devices 4220, and / or the humidifier 5000.

[0416] The central controller 4230 may be configured to provide output signal(s) to one or more of an output device 4290, a pressure generator 4140, a therapy device controller 4240, a data communication interface 4280, and / or the humidifier 5000.

[0417] In some forms of the present technology, the central controller 4230 is configured to implement the one or more methodologies described herein, such as the one or more algorithms 4300 which may be implemented with processor-control instructions, expressed as computer programs stored in a non-transitory computer readable storage medium, such as memory 4260. In some forms of the present technology, the central controller 4230 may be integrated with an RPT device 4000. However, in some forms of the present technology, some methodologies may be performed by a remotely located device. For example, the remotely located device may determine control settings for a ventilator or detect respiratory related events by analysis of stored data such as from any of the sensors described herein.4.6.1.4 Clock

[0418] The RPT device 4000 may include a clock 4232 that is connected to the central controller 4230.4.6.1.5 Therapy device controller

[0419] In one form of the present technology, therapy device controller 4240 is a therapy control module 4330 that forms part of the algorithms 4300 executed by the central controller 4230.

[0420] In one form of the present technology, therapy device controller 4240 is a dedicated motor control integrated circuit. For example, in one form a MC33035 brushless DC motor controller, manufactured by ONSEMI is used.4.6.1.6 Protection circuits

[0421] The one or more protection circuits 4250 in accordance with the present technology may comprise an electrical protection circuit, a temperature and / or pressure safety circuit.4.6.1.7 Memory

[0422] In accordance with one form of the present technology the RPT device 4000 includes memory 4260, e.g., non-volatile memory. In some forms, memory 4260 may include battery powered static RAM. In some forms, memory 4260 may include volatile RAM.

[0423] Memory 4260 may be located on the PCBA 4202. Memory 4260 may be in the form of EEPROM, or NAND flash.

[0424] Additionally, or alternatively, RPT device 4000 includes a removable form of memory 4260, for example a memory card made in accordance with the Secure Digital (SD) standard.

[0425] In one form of the present technology, the memory 4260 acts as a non-transitory computer readable storage medium on which is stored computer program instructions expressing the one or more methodologies described herein, such as the one or more algorithms 4300.4.6.1.8 Data communication systems

[0426] In one form of the present technology, a data communication interface 4280 is provided, and is connected to the central controller 4230 (see e.g., Fig. 4C). Data communication interface 4280 may be connectable to a remote external communication network 4282 and / or a local external communication network 4284. The remote external communication network 4282 may be connectable to a remoteexternal device 4286. The local external communication network 4284 may be connectable to a local external device 4288.

[0427] In one form, data communication interface 4280 is part of the central controller 4230. In another form, data communication interface 4280 is separate from the central controller 4230, and may comprise an integrated circuit or a processor.

[0428] In one form, remote external communication network 4282 is the Internet. The data communication interface 4280 may use wired communication (e.g. via Ethernet, or optical fibre) or a wireless protocol (e.g. CDMA, GSM, LTE) to connect to the Internet.

[0429] In one form, local external communication network 4284 utilises one or more communication standards, such as Bluetooth, or a consumer infrared protocol.

[0430] In one form, remote external device 4286 is one or more computers, for example a cluster of networked computers. In one form, remote external device 4286 may be virtual computers, rather than physical computers. In either case, such a remote external device 4286 may be accessible to an appropriately authorised person such as a clinician.

[0431] The local external device 4288 may be a personal computer, mobile phone, tablet or remote control.4.6.1.9 Output devices including optional display, alarms

[0432] An output device 4290 in accordance with the present technology may take the form of one or more of a visual, audio and haptic unit. A visual display may be a Liquid Crystal Display (LCD) or Light Emitting Diode (LED) display.4.6.2.9.1 Display driver

[0433] A display driver 4292 receives as an input the characters, symbols, or images intended for display on the display 4294, and converts them to commands that cause the display 4294 to display those characters, symbols, or images.4.6.2.9.2 Display

[0434] A display 4294 is configured to visually display characters, symbols, or images in response to commands received from the display driver 4292. For example, the display 4294 may be an eight-segment display, in which case the display driver 4292 converts each character or symbol, such as the figure “0”, to eight logical signals indicating whether the eight respective segments are to be activated to display a particular character or symbol.4.6.3 RPT device algorithms

[0435] As mentioned above, in some forms of the present technology, the central controller 4230 may be configured to implement one or more algorithms 4300 expressed as computer programs stored in a non-transitory computer readable storage medium, such as memory 4260. The algorithms 4300 are generally grouped into groups referred to as modules.

[0436] In other forms of the present technology, some portion or all of the algorithms 4300 may be implemented by a controller of an external device such as the local external device 4288 or the remote external device 4286. In such forms, data representing the input signals and / or intermediate algorithm outputs necessary for the portion of the algorithms 4300 to be executed at the external device may be communicated to the external device via the local external communication network 4284 or the remote external communication network 4282. In such forms, the portion of the algorithms 4300 to be executed at the external device may be expressed as computer programs, such as with processor control instructions to be executed by one or more processor(s), stored in a non-transitory computer readable storage medium accessible to the controller of the external device. Such programs configure the controller of the external device to execute the portion of the algorithms 4300.

[0437] In such forms, the therapy parameters generated by the external device via the therapy engine module 4320 (if such forms part of the portion of the algorithms 4300 executed by the external device) may be communicated to the central controller 4230 to be passed to the therapy control module 4330.4.6.3.1 Pre-processing module

[0438] A pre-processing module 4310 in accordance with one form of the present technology receives as an input a signal from a transducer 4270, for example a flow rate sensor 4274 or pressure sensor 4272, and performs one or more process steps to calculate one or more output values that will be used as an input to another module, for example a therapy engine module 4320.

[0439] In one form of the present technology, the output values include the interface pressure Pm, the vent flow rate Qv, the respiratory flow rate Qr, and the leak flow rate QI.

[0440] In various forms of the present technology, the pre-processing module 4310 comprises one or more of the following algorithms: interface pressure and leakflow rate estimation 4312, CO2 estimation 4316, and respiratory flow rate estimation 4318.4.6.3.1.1 Interface pressure and leak flow rate estimation

[0441] In one form of the present technology, the interface pressure estimation algorithm 4312 receives as inputs a signal from the pressure sensor 4272 indicative of the pressure in the pneumatic path proximal to an outlet of the pneumatic block (the device pressure Pd) and a signal from the flow rate sensor 4274 representative of the flow rate of the airflow leaving the RPT device 4000 (the device flow rate Qd). The device flow rate Qd, absent any supplementary gas 4180, may be used as the total flow rate Qt. The interface pressure algorithm 4312 estimates the pressure drop AP through the air circuit 4170. The dependence of the pressure drop AP on the total flow rate Qt may be modelled for the air circuit 4170 by a pressure drop characteristic ^(2).

[0442] The pressure drop and impedance of the gas flow path between the RPT device 4000 and the patient interface 3000 can vary over time and may be different for each type of patient interface 3000 and air circuit 4170. These variations are typically addressed by having the patient enter a patient interface profile into the central controller 4230 that corresponds to the particular patient interface 3000 and air circuit 4170 being used. Not only does this add complexity to the system, tolerances in the stored lookup tables associated with the patient interface profiles can compound inherent errors in the estimated interface pressure. Such errors can introduce as much as a 12 L / min variance. If the patient selects the wrong patient interface profile, the errors can be even greater.

[0443] However, locating the vent outlet within or near the RPT device 4000 and running the second gas flow path 6008 (i.e., the vent flow path) through the conduit 6002 can allow for a more simplified approach to determining the pressure drop characteristic AP Q) while also reducing or eliminating such errors.

[0444] In particular, as is shown in Fig. 4F, the patient interface pressure (or mask pressure) 4600 is proportional to the vent flow 4610. Accordingly, rather than relying on predetermined values in a look up table to determine the pressure drop characteristic AP Q), the pressure drop characteristic may be determined based on measured values for the device pressure Pd and the pressure drop across the vented branch (i.e., the second gas flow path or vented path 6008). Because the vent flow isproportional to the pressure in the patient interface 3000, variances in the impedance due to changes within the gas flow path and the structure of the patient interface 3000 and air circuit 4170 are automatically accounted for in the vent flow data. Thus, using the vent flow data measured at the RPT device 4000 improves the accuracy of the pressure drop characteristic AP(O) and eliminates the need to enter a patient interface profile into the central controller 4230.

[0445] The initial step to determine the pressure drop characteristic is to compute the mask leak QI (e.g., according to the leak flow rate estimation 4316). The computation may be performed according to the following formula:Qi = Qd ~ Qp ~ Qvwhere Qd is the flow rate measured in the pneumatic path proximal to the outlet of the pneumatic block in the RPT device 4000, Qp is the flow rate at the patient’s airways, and Qv is the flow rate measured in the second gas flow path (vent branch or path) 6008. Over time, the patient flow Qp will become zero and can be eliminated from the above formula to produce the new formula:Ql = Qd - Qvin which the average leak is equivalent to the average of measured RPT device flow minus the average of the measured vent flow.

[0446] Next, the pressure loss between the RPT device 4000 and the patient interface 3000 (i.e., the effective pressure Pf) may be calculated. The effective pressure Pt may be calculated according to the following formula:Pt = Pd ~ Pv

[0447] In addition, the pressure drop characteristic may be represented by KI and K2 in the following formula:Pt= KrQd2+ K2Qd

[0448] The above formula may be used to formulate a system of equations constructed from:A ■ x = b

[0449] where:A= [Qd2, Qd]x = [Ki; K2]b = [Pt]

[0450] The pressure loss from the blower to the mask may be considered as a function of blower flow.Pd~ Pm= K1.Qb2+ K2.Qd

[0451] In addition, the pressure drop across the vent to atmosphere may be considered as a function of vent flow

[0452] Pm may be initially unknown and it may be desired to control Pm to be constant, so by combining the two equationsPa - [C1. Qv2+ C2.Qv] = K1.Qd2+ K2.QdPa = [Ki. Qd2+ K2. Qd] + [C2. Qv2+ C2.QV]

[0453] Pd, Qd, and Qv may all be measured time signals, so with perturbations to the system with variation in Qp and QI, utilizing different points in time, an overdetermined set of simultaneous equations may be generated and solved using a method such as least squares estimates, which is robust to noise.b = A • x

[0454] where:

[0455] For n measurements (at different times or flow conditions), the equations may be stacked:

[0456] Finally, the solutions may be computed according to the Least Squares method:x = (ArA)'~1Arb

[0457] In some embodiments, Qn, Pn may represent the most recent time samples, or a recent time sample of the measured signals, and n will be a fixed or a variable number, determining how far back in time samples will be included in the calculation to estimate the coefficients. In some embodiments, the samples may not beconsecutive, but chosen to include a range of pressures and flows, to ensure a more generalisable solution for the estimate of the coefficients.

[0458] Once the coefficients KI and K2 have been estimated they can then be used in the control system to control pressure in the mask, for example, by using a PID controller to control the RPT device pressure according to the equation:Pd~ Pm= K1.Qd2+ K2.Qd4.6.3.1.2 where the target mask pressure may be substituted for Pm.Respiratory flow rate estimation

[0459] In one form of the present technology, the respiratory flow rate estimation algorithm 4318 receives as an input a total flow rate, Qt, a vent flow rate, Qv, and a leak flow rate, QI, and estimates a respiratory flow rate of air, Qr, to the patient, by subtracting the vent flow rate Qv and the leak flow rate QI from the total flow rate Qt.4.6.3.1.3 CO 2 estimation

[0460] In one form of the present technology, the CO2 estimation algorithm 4316 may receive a CO2 measurement. The CO2 measurement may be taken from an RPT device end of the conduit 6002 (or within the RPT device 4000 in the second gas flow path 6008) at the same location indicated in Figs. 7A, 7D, and 7F as the transducer 4274. The measurement may be taken via a mainstream or side stream sensor, such as an infrared sensor or acoustic sensor. In some embodiments, the venting tube 6004 itself could be incorporated into a CO2 sensing system. For example, the venting tube 6004 may have an acoustic sensor, that is configured with hardware and algorithms to determine the speed of sound within the conduit. This may be achieved by determining the resonant frequency of the conduit 6002 and the venting tube 6004, being a peak in the spectrum within a predicted range, determined by the length of the conduit 6002 and the venting tube 6004, and the gas composition and properties expected in the venting tube 6004.

[0461] Vent flow CO2 concentration may in turn be used to estimate expired CO2, by using flow measurements to determine the expiratory to ambient concentration of air in the venting tube 6004, and hence how much ambient air dilutes the CO2 concentration in the venting tube 6004.

[0462] In some embodiments, vent flow CO2 concentration may be used to identify therapy issues like excessive dead space due to a blockage in the vent conduit.

[0463] In some embodiments, vent flow CO2 concentration may be used in a feedback loop to control dead space for therapeutic purposes, such as dosing CO2 to promote respiratory drive, for example for patients with central apnea of hypopnea, or to increase CO2 prior to sleep to promote sleep in patients with insomnia tendencies.

[0464] In some embodiments, vent flow CO2 concentration may be used to estimate metabolism or cardiac output, which may be used as a marker for many other clinical decisions

[0465] In one aspect the speed of sound may be measured in the venting tube 6004. The algorithm is designed to account for background noise, reflections, and variations in gas conditions.

[0466] As an initial setup for determining CO2 concentration based on the speed of sound, a conduit (e.g., venting tube 6004) may be selected that has a fixed length (Ad), and the length of the conduit may be measured or otherwise known. For calibration, a controlled gas mixture (e.g., ambient air and exhaled gas) may be prepared with known volume fractions, and the composition of the gas mixture may be recorded for analysis.

[0467] A microphone may then be positioned at one end of the venting tube 6004 to capture both the direct sound and echoes within the venting tube 6004. Naturally occurring system noise (e.g., airflow noise or mechanical vibrations) or controlled sounds (e.g., a sharp pulse or chirp) may be used as a signal input for calibration.

[0468] Once the parameters and the microphone are setup, sound waves and echoes may be recorded in a high-resolution data acquisition system. It may be desired to ensure that the sampling frequency is high enough (e.g., 44.1 kHz or higher) to capture fine details in the signal. A band-pass filter centered around the frequency of interest may be applied to remove extraneous noise. Then, the signal may be normalized to amplify weaker components without saturating the recorded data. Autocorrelation analysis may be performed on the recorded signal to identify peaks corresponding to the time delay of echoes. The first peak after zero lag may represent the round-trip echo delay (At).

[0469] Once the signal has been detected and processed, the speed of sound may be calculated. The calculation may be performed according to the following formula:v = 2 x Ad / Atwhere: At is the round-trip time of the sound wave, determined from the autocorrelation analysis. The calculation may be automated using software or a microcontroller to process real-time data.

[0470] After the speed of sound has been calculated, the calculation may be validated and the gas mixture may be adjusted. The known volume fractions of the gas mixture may be used to calculate the molar mass (M) and adiabatic index (y) according to the following formulas:M = £(voli x Mi + vohxM2)y = weighted sum of specific heat ratios based on gas fractions

[0471] The measured speed of sound may be compared with theoretical values using the equation:v = (y x R x T / M)where: R is the Universal gas constant (8.314 J / mol K)T is Temperature (Kelvin)M is Molar mass of the mixture

[0472] Environmental factors such as temperature and humidity should be accounted for to improve accuracy. In addition, the microphone, signal processing, and speed of sound calculation may be integrated into an automated system controlled by software or a microcontroller. In addition, environmental sensors (temperature, humidity, CO2 concentration) may be included for real-time gas condition monitoring.

[0473] Raw signals, filtered data, echo delays, and calculated speeds of sound may be stored. In addition, metadata such as gas composition, temperature, and humidity may be maintained for each measurement. Also, the calculated speed of sound may be displayed along with environmental conditions on a user interface.

[0474] In order to ensure minimal external interference the conduit should be acoustically isolating. In addition, a high-dynamic-range microphone may be used to capture weak signals effectively. Also, the system may be tested with known conditions (e.g., pure ambient air) to validate accuracy. Algorithms may be implemented to handle and reject noisy or ambiguous data, such as echoes with overlapping delay.

[0475] In one aspect, the rate of CO2 elimination may be used to determine cardiac output. According to the Fick principle, the rate of uptake or release of a substance (such as oxygen or CO2) by an organ or the body is related to the blood flow through the organ and the arterial-venous concentration difference of the substance. For CO2, the principle can be expressed as: Rate of CO2 elimination = Cardiac Output x (Venous CO2 content - Arterial CO2 content). Where: Rate of CO2 elimination is measured from expired gas (in mL / min), arterial CO2 content is CO2 content in arterial blood (in mL CO2 / IOO mL blood), venous CO2 content is CO2 content in venous blood (in mL CO2 / IOO mL blood), and cardiac Output is volume of blood pumped by the heart per minute (in mL / min).

[0476] To measure expired CO2 (i.e., rate of CO2 elimination), a metabolic cart or capnography may be used to measure the volume of CO2 expired per minute during steady-state breathing. This provides the rate of CO2 elimination. Arterial CO2 content may be determined by estimating from arterial blood gas (ABG) analysis or use end-tidal CO2 (PetCO2) as a surrogate for arterial CO2 partial pressure (PaCO2). The arterial content may be calculated using the CO2 dissociation curve: Arterial CO2 content = 0.003 x PaCCL + CO2 bound to hemoglobin. This incorporates dissolved CO2 and CO2 bound to hemoglobin (based on saturation and hematocrit).

[0477] Venous CO2 content may be determined by using a CO2 dissociation curve to estimate and assume a fixed arteriovenous difference or measure directly from mixed venous blood (if invasive sampling is available).

[0478] To calculate the cardiac output (CO), the Fick equation (as discussed above) may be rearranged to solve for cardiac output: Cardiac Output = Rate of CO2 elimination / (Venous CO2 content - Arterial CO2 content). Once the cardiac output is calculated, the metabolism may be estimated. In particular, the rate of CO2 elimination is directly proportional to metabolic rate, reflecting the body’s aerobic metabolism. This measurement provides insight into metabolic CO2 production.

[0479] By combining expired CO2 measurements with estimates of arterial and venous CO2 content, cardiac output can be inferred without invasive techniques. Measuring the rate of CO2 elimination provides a quantitative measure of whole-body metabolism during rest or exercise. CCL-based Fick measurements are valuable for assessing cardiac output and metabolism in ventilated or critically ill patients4.6.3.1 Therapy Engine Module

[0480] In one form of the present technology, a therapy engine module 4320 receives as inputs one or more of a pressure, Pm, in a patient interface 3000, and a respiratory flow rate of air to a patient, Qr, and provides as an output one or more therapy parameters.

[0481] In one form of the present technology, a therapy parameter is a treatment pressure Pt.

[0482] In one form of the present technology, therapy parameters are one or more of an amplitude of a pressure variation, a base pressure, and a target ventilation.

[0483] In various forms, the therapy engine module 4320 comprises one or more of the following algorithms: phase determination 4321, waveform determination 4322, ventilation determination 4323, inspiratory flow limitation determination 4324, apnea / hypopnea determination 4325, snore determination 4326, airway patency determination 4327, target ventilation determination 4328, and therapy parameter determination 4329.4.6.3.2.1 Phase determination

[0484] In one form of the present technology, the RPT device 4000 does not determine phase.

[0485] In one form of the present technology, a phase determination algorithm 4321 receives as an input a signal indicative of respiratory flow rate, Qr, and provides as an output a phase of a current breathing cycle of a patient 1000.

[0486] In some forms, known as discrete phase determination, the phase output is a discrete variable. One implementation of discrete phase determination provides a bi-valued phase output with values of either inhalation or exhalation, for example represented as values of 0 and 0.5 revolutions respectively, upon detecting the start of spontaneous inhalation and exhalation respectively. RPT devices 4000 that “trigger” and “cycle” effectively perform discrete phase determination, since the trigger and cycle points are the instants at which the phase changes from exhalation to inhalation and from inhalation to exhalation, respectively. In one implementation of bi-valued phase determination, the phase output is determined to have a discrete value of 0 (thereby “triggering” the RPT device 4000) when the respiratory flow rate Qr has a value that exceeds a positive threshold, and a discrete value of 0.5 revolutions (thereby “cycling” the RPT device 4000) when a respiratory flow rate Qrhas a value that is more negative than a negative threshold. The inhalation time Ti and the exhalation time Te may be estimated as typical values over many respiratory cycles of the time spent with phase equal to 0 (indicating inspiration) and 0.5 (indicating expiration) respectively.

[0487] Another implementation of discrete phase determination provides a trivalued phase output with a value of one of inhalation, mid-inspiratory pause, and exhalation.

[0488] In other forms, known as continuous phase determination, the phase output is a continuous variable, for example varying from 0 to 1 revolutions, or 0 to 2 ;r radians. RPT devices 4000 that perform continuous phase determination may trigger and cycle when the continuous phase reaches 0 and 0.5 revolutions, respectively. In one implementation of continuous phase determination, a continuous value of phase is determined using a fuzzy logic analysis of the respiratory flow rate Qr. A continuous value of phase determined in this implementation is often referred to as “fuzzy phase”. In one implementation of a fuzzy phase determination algorithm 4321, the following rules are applied to the respiratory flow rate Qr1. If Qr is zero and increasing fast then is 0 revolutions.2. If Qr is large positive and steady thenis 0.25 revolutions.3. is zero and falling fast, then is 0.5 revolutions.4. If Qr is large negative and steady thenis 0.75 revolutions.5. If Qr is zero and steady and the 5-second low-pass filtered absolute value of Qr is large thenis 0.9 revolutions.6. If Qr is positive and the phase is expiratory, then is 0 revolutions.7. If Qr is negative and the phase is inspiratory, then is 0.5 revolutions. 8. If the 5-second low-pass filtered absolute value of Qr is large,is increasing at a steady rate equal to the patient’s breathing rate, low-pass filtered with a time constant of 20 seconds.

[0489] The output of each rule may be represented as a vector whose phase is the result of the rule and whose magnitude is the fuzzy extent to which the rule is true. The fuzzy extent to which the respiratory flow rate is “large”, “steady”, etc. is determined with suitable membership functions. The results of the rules, represented as vectors, are then combined by some function such as taking the centroid. In such a combination, the rules may be equally weighted, or differently weighted.

[0490] In another implementation of continuous phase determination, the phase is first discretely estimated from the respiratory flow rate Qr as described above, as are the inhalation time Ti and the exhalation time Te. The continuous phase at any instant may be determined as the half the proportion of the inhalation time Ti that has elapsed since the previous trigger instant, or 0.5 revolutions plus half the proportion of the exhalation time Te that has elapsed since the previous cycle instant (whichever instant was more recent).4.6.3.2.2 Waveform determination

[0491] In one form of the present technology, the therapy parameter determination algorithm 4329 provides an approximately constant treatment pressure throughout a respiratory cycle of a patient.

[0492] In other forms of the present technology, the therapy control module 4330 controls the pressure generator 4140 to provide a treatment pressure Pt that varies as a function of phase of a respiratory cycle of a patient according to a waveform template 11( ).

[0493] In one form of the present technology, a waveform determination algorithm 4322 provides a waveform template 11( ) with values in the range [0, 1] on the domain of phase values O provided by the phase determination algorithm 4321 to be used by the therapy parameter determination algorithm 4329.

[0494] In one form, suitable for either discrete or continuously-valued phase, the waveform template 11(0) is a square-wave template, having a value of 1 for values of phase up to and including 0.5 revolutions, and a value of 0 for values of phase above 0.5 revolutions. In one form, suitable for continuously-valued phase, the waveform template 11(0) comprises two smoothly curved portions, namely a smoothly curved (e.g. raised cosine) rise from 0 to 1 for values of phase up to 0.5 revolutions, and a smoothly curved (e.g. exponential) decay from 1 to 0 for values of phase above 0.5 revolutions. In one form, suitable for continuously-valued phase, the waveform template 11( ) is based on a square wave, but with a smooth rise from 0 to 1 for values of phase up to a “rise time” that is less than 0.5 revolutions, and a smooth fall from 1 to 0 for values of phase within a “fall time” after 0.5 revolutions, with a “fall time” that is less than 0.5 revolutions.

[0495] In some forms of the present technology, the waveform determination algorithm 4322 selects a waveform template 11( ) from a library of waveformtemplates, dependent on a setting of the RPT device. Each waveform template 11(0) in the library may be provided as a lookup table of values II against phase values . In other forms, the waveform determination algorithm 4322 computes a waveform template 11(0) “on the fly” using a predetermined functional form, possibly parametrised by one or more parameters (e.g. time constant of an exponentially curved portion). The parameters of the functional form may be predetermined or dependent on a current state of the patient 1000.

[0496] In some forms of the present technology, suitable for discrete bi-valued phase of either inhalation (0 = 0 revolutions) or exhalation (0 = 0.5 revolutions), the waveform determination algorithm 4322 computes a waveform template II “on the fly” as a function of both discrete phase 0 and time t measured since the most recent trigger instant. In one such form, the waveform determination algorithm 4322 computes the waveform template 11(0, f) in two portions (inspiratory and expiratory) as follows:0 = 00 = 0.5

[0497] where Hi(t) and ne( / ) are inspiratory and expiratory portions of the waveform template 11(0, f). In one such form, the inspiratory portion H i(Z) of the waveform template is a smooth rise from 0 to 1 parametrised by a rise time, and the expiratory portion He( / ) of the waveform template is a smooth fall from 1 to 0 parametrised by a fall time.4.6.3.2.3 Ventilation determination

[0498] In one form of the present technology, a ventilation determination algorithm 4323 receives an input a respiratory flow rate Qr, and determines a measure indicative of current patient ventilation, Vent.

[0499] In some implementations, the ventilation determination algorithm 4323 determines a measure of ventilation Vent that is an estimate of actual patient ventilation. One such implementation is to take half the absolute value of respiratory flow rate, Qr, optionally filtered by low-pass filter such as a second order Bessel low-pass filter with a comer frequency of 0.11 Hz.

[0500] In other implementations, the ventilation determination algorithm 4323 determines a measure of ventilation Vent that is broadly proportional to actual patient ventilation. One such implementation estimates peak respiratory flow rate Qpeakover the inspiratory portion of the cycle. This and many other procedures involving sampling the respiratory flow rate Qr produce measures which are broadly proportional to ventilation, provided the flow rate waveform shape does not vary very much (here, the shape of two breaths is taken to be similar when the flow rate waveforms of the breaths normalised in time and amplitude are similar). Some simple examples include the median positive respiratory flow rate, the median of the absolute value of respiratory flow rate, and the standard deviation of flow rate. Arbitrary linear combinations of arbitrary order statistics of the absolute value of respiratory flow rate using positive coefficients, and even some using both positive and negative coefficients, are approximately proportional to ventilation. Another example is the mean of the respiratory flow rate in the middle K proportion (by time) of the inspiratory portion, where 0 < K< 1. There is an arbitrarily large number of measures that are exactly proportional to ventilation if the flow rate shape is constant.4.6.3.2.4 Determination of Inspiratory Flow Limitation

[0501] In one form of the present technology, the central controller 4230 executes an inspiratory flow limitation determination algorithm 4324 for the determination of the extent of inspiratory flow limitation.

[0502] In one form, the inspiratory flow limitation determination algorithm 4324 receives as an input a respiratory flow rate signal Qr and provides as an output a metric of the extent to which the inspiratory portion of the breath exhibits inspiratory flow limitation.

[0503] In one form of the present technology, the inspiratory portion of each breath is identified by a zero-crossing detector. A number of evenly spaced points (for example, sixty-five), representing points in time, are interpolated by an interpolator along the inspiratory flow rate-time curve for each breath. The curve described by the points is then scaled by a scalar to have unity length (duration / period) and unity area to remove the effects of changing breathing rate and depth. The scaled breaths are then compared in a comparator with a pre-stored template representing a normal unobstructed breath, similar to the inspiratory portion of the breath shown in Fig. 6A. Breaths deviating by more than a specified threshold (typically 1 scaled unit) at any time during the inspiration from this template, such as those due to coughs, sighs, swallows and hiccups, as determined by a test element, are rejected. For non -rejected data, a moving average of the first such scaled point is calculated by the central controller 4230 for the preceding several inspiratory events. This is repeated over thesame inspiratory events for the second such point, and so on. Thus, for example, sixty-five scaled data points are generated by the central controller 4230, and represent a moving average of the preceding several inspiratory events, e.g., three events. The moving average of continuously updated values of the (e.g., sixty-five) points are hereinafter called the "scaled flow rate ", designated as Qs(t). Alternatively, a single inspiratory event can be utilised rather than a moving average.

[0504] From the scaled flow rate, two shape factors relating to the determination of partial obstruction may be calculated.

[0505] Shape factor 1 is the ratio of the mean of the middle (e.g. thirty-two) scaled flow rate points to the mean overall (e.g. sixty-five) scaled flow rate points. Where this ratio is in excess of unity, the breath will be taken to be normal. Where the ratio is unity or less, the breath will be taken to be obstructed. A ratio of about 1.17 is taken as a threshold between partially obstructed and unobstructed breathing, and equates to a degree of obstruction that would permit maintenance of adequate oxygenation in a typical patient.

[0506] Shape factor 2 is calculated as the RMS deviation from unit scaled flow rate, taken over the middle (e.g. thirty-two) points. An RMS deviation of about 0.2 units is taken to be normal. An RMS deviation of zero is taken to be a totally flowlimited breath. The closer the RMS deviation to zero, the breath will be taken to be more flow limited.

[0507] Shape factors 1 and 2 may be used as alternatives, or in combination. In other forms of the present technology, the number of sampled points, breaths and middle points may differ from those described above. Furthermore, the threshold values can be other than those described.4.6.3.2.5 Determination of apneas and hypopneas

[0508] In one form of the present technology, the central controller 4230 executes an apnea / hypopnea determination algorithm 4325 for the determination of the presence of apneas and / or hypopneas.

[0509] In one form, the apnea / hypopnea determination algorithm 4325 receives as an input a respiratory flow rate signal Qr and provides as an output a flag that indicates that an apnea or a hypopnea has been detected.

[0510] In one form, an apnea will be said to have been detected when a function of respiratory flow rate Qr falls below a flow rate threshold for a predetermined period of time. The function may determine a peak flow rate, a relatively short-termmean flow rate, or a flow rate intermediate of relatively short-term mean and peak flow rate, for example an RMS flow rate. The flow rate threshold may be a relatively long-term measure of flow rate.

[0511] In one form, a hypopnea will be said to have been detected when a function of respiratory flow rate Qr falls below a second flow rate threshold for a predetermined period of time. The function may determine a peak flow, a relatively short-term mean flow rate, or a flow rate intermediate of relatively short-term mean and peak flow rate, for example an RMS flow rate. The second flow rate threshold may be a relatively long-term measure of flow rate. The second flow rate threshold is greater than the flow rate threshold used to detect apneas.4.6.3.2.6 Determination of snore

[0512] In one form of the present technology, the central controller 4230 executes one or more snore determination algorithms 4326 for the determination of the extent of snore.

[0513] In one form, the snore determination algorithm 4326 receives as an input a respiratory flow rate signal Qr and provides as an output a metric of the extent to which snoring is present.

[0514] The snore determination algorithm 4326 may comprise the step of determining the intensity of the flow rate signal in the range of 30-300 Hz. Further, the snore determination algorithm 4326 may comprise a step of filtering the respiratory flow rate signal Qr to reduce background noise, e.g., the sound of airflow in the system from the blower.4.6.3.2.7 Determination of airway patency

[0515] In one form of the present technology, the central controller 4230 executes one or more airway patency determination algorithms 4327 for the determination of the extent of airway patency.

[0516] In one form, the airway patency determination algorithm 4327 receives as an input a respiratory flow rate signal Qr, and determines the power of the signal in the frequency range of about 0.75 Hz and about 3 Hz. The presence of a peak in this frequency range is taken to indicate an open airway. The absence of a peak is taken to be an indication of a closed airway.

[0517] In one form, the frequency range within which the peak is sought is the frequency of a small forced oscillation in the treatment pressure Pt. In oneimplementation, the forced oscillation is of frequency 2 Hz with amplitude about 1 cndHhO.

[0518] In one form, airway patency determination algorithm 4327 receives as an input a respiratory flow rate signal Qr, and determines the presence or absence of a cardiogenic signal. The absence of a cardiogenic signal is taken to be an indication of a closed airway.4.6.3.2.8 Determination of target ventilation

[0519] In one form of the present technology, the central controller 4230 takes as input the measure of current ventilation, Vent, and executes one or more target ventilation determination algorithms 4328 for the determination of a target value Vtgt for the measure of ventilation.

[0520] In some forms of the present technology, there is no target ventilation determination algorithm 4328, and the target value Vtgt is predetermined, for example by hard-coding during configuration of the RPT device 4000 or by manual entry through the input device 4220.

[0521] In other forms of the present technology, such as adaptive servoventilation (ASV), the target ventilation determination algorithm 4328 computes a target value Vtgt from a value Vtyp indicative of the typical recent ventilation of the patient.

[0522] In some forms of adaptive servo-ventilation, the target ventilation Vtgt is computed as a high proportion of, but less than, the typical recent ventilation Vtyp. The high proportion in such forms may be in the range (80%, 100%), or (85%, 95%), or (87%, 92%).

[0523] In other forms of adaptive servo-ventilation, the target ventilation Vtgt is computed as a slightly greater than unity multiple of the typical recent ventilation f -

[0524] The typical recent ventilation Vtyp is the value around which the distribution of the measure of current ventilation Vent over multiple time instants over some predetermined timescale tends to cluster, that is, a measure of the central tendency of the measure of current ventilation over recent history. In one implementation of the target ventilation determination algorithm 4328, the recent history is of the order of several minutes, but in any case should be longer than the timescale of Cheyne-Stokes waxing and waning cycles. The target ventilation determination algorithm 4328 may use any of the variety of well-known measures ofcentral tendency to determine the typical recent ventilation Vtyp from the measure of current ventilation, Vent. One such measure is the output of a low-pass filter on the measure of current ventilation Vent, with time constant equal to one hundred seconds.4.6.3.2.9 Determination of therapy parameters

[0525] In some forms of the present technology, the central controller 4230 executes one or more therapy parameter determination algorithms 4329 for the determination of one or more therapy parameters using the values returned by one or more of the other algorithms in the therapy engine module 4320.

[0526] In one form of the present technology, the therapy parameter is an instantaneous treatment pressure Pt. In one implementation of this form, the therapy parameter determination algorithm 4329 determines the treatment pressure Pt using the equationft= n(<P,r)+ / >(1)

[0527] where:• A is the amplitude,• H(<t>, f) is the waveform template value (in the range 0 to 1) at the current value of phase and t of time, and• P is a base pressure.

[0528] If the waveform determination algorithm 4322 provides the waveform template 11( , f) as a lookup table of values II indexed by phase , the therapy parameter determination algorithm 4329 applies equation (1) by locating the nearest lookup table entry to the current value of phase returned by the phase determination algorithm 4321, or by interpolation between the two entries straddling the current value of phase.

[0529] The values of the amplitude A and the base pressure Po may be set by the therapy parameter determination algorithm 4329 depending on the chosen respiratory pressure therapy mode in the manner described below.4.6.3.3 Therapy Control module

[0530] The therapy control module 4330 in accordance with one aspect of the present technology receives as inputs the therapy parameters from the therapy parameter determination algorithm 4329 of the therapy engine module 4320, and controls the pressure generator 4140 to deliver a flow of air in accordance with the therapy parameters.

[0531] In one form of the present technology, the therapy parameter is a treatment pressure Pt, and the therapy control module 4330 controls the pressure generator 4140 to deliver a flow of air whose interface pressure Pm at the patient interface 3000 is equal to the treatment pressure Pt.4.6.3.4 Detection of fault conditions

[0532] In one form of the present technology, the central controller 4230 executes one or more methods 4340 for the detection of fault conditions. The fault conditions detected by the one or more methods 4340 may include at least one of the following:• Power failure (no power, or insufficient power)• Transducer fault detection• Failure to detect the presence of a component• Operating parameters outside recommended ranges (e.g. pressure, flow rate, temperature, PaO2)• Failure of a test alarm to generate a detectable alarm signal.

[0533] Upon detection of the fault condition, the corresponding algorithm 4340 signals the presence of the fault by one or more of the following:• Initiation of an audible, visual & / or kinetic (e.g. vibrating) alarm• Sending a message to an external device• Logging of the incident4.6.4 Supplementary gas delivery

[0534] In one form of the present technology, supplementary gas, e.g. oxygen, 4180 is delivered to one or more points in the pneumatic path, such as upstream of the pneumatic block 4020, to the air circuit 4170, and / or to the patient interface 3000. 4.7 HUMIDIFIER4.7.1 Humidifier overview

[0535] In one form of the present technology there is provided a humidifier 5000 (e.g. as shown in Fig. 5A) to change the absolute humidity of air or gas for delivery to a patient relative to ambient air. Typically, the humidifier 5000 is used to increase the absolute humidity and increase the temperature of the flow of air (relative to ambient air) before delivery to the patient’s airways.

[0536] The humidifier 5000 may comprise a humidifier reservoir 5110, a humidifier inlet 5002 to receive a flow of air, and a humidifier outlet 5004 to deliver a humidified flow of air. In some forms, as shown in Fig. 5A and Fig. 5B, an inlet andan outlet of the humidifier reservoir 5110 may be the humidifier inlet 5002 and the humidifier outlet 5004 respectively. The humidifier 5000 may further comprise a humidifier base 5006, which may be adapted to receive the humidifier reservoir 5110 and comprise a heating element 5240.4.8 BREATHING WAVEFORMS

[0537] Fig. 6A shows a model typical breath waveform of a person while sleeping. The horizontal axis is time, and the vertical axis is respiratory flow rate. While the parameter values may vary, a typical breath may have the following approximate values: tidal volume Vt 0.5L, inhalation time Ti 1.6s, peak inspiratory flow rate Qpeak 0.4 L / s, exhalation time Te 2.4s, peak expiratory flow rate Qpeak -0.5 L / s. The total duration of the breath, Tlol. is about 4s. The person typically breathes at a rate of about 15 breaths per minute (BPM), with Ventilation Vent about 7.5 L / min. A typical duty cycle, the ratio of Ti to Ttot, is about 40%.4.9 GLOSSARY

[0538] For the purposes of the present technology disclosure, in certain forms of the present technology, one or more of the following definitions may apply. In other forms of the present technology, alternative definitions may apply.4.9.1 General

[0539] Air '. In certain forms of the present technology, air may be taken to mean atmospheric air, and in other forms of the present technology air may be taken to mean some other combination of breathable gases, e.g. oxygen enriched air.

[0540] 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.

[0541] 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.

[0542] In another example, ambient pressure may be the pressure immediately surrounding or external to the body.

[0543] 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 forexample, noise generated by an RPT device or emanating from a mask or patient interface. Ambient noise may be generated by sources outside the room.

[0544] 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.

[0545] 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.

[0546] 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’.

[0547] In the example of patient respiration, a flow rate may be nominally positive for the inspiratory portion of a breathing cycle of a patient, and hence negative for the expiratory portion of the breathing cycle of a patient. Device flow rate, Qd, is the flow rate of air leaving the RPT device. Total flow rate, Qt, is the flow rate of air and any supplementary gas reaching the patient interface via the air circuit. Vent flow rate, Qv, is the flow rate of air leaving a vent to allow washout of exhaled gases. Leak flow rate, QI, 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.

[0548] Flow therapy. Respiratory therapy comprising the delivery of a flow of air to an entrance to the airways at a controlled flow rate referred to as the treatment flow rate that is typically positive throughout the patient’s breathing cycle.

[0549] Humidifier'. The word humidifier will be taken to mean a humidifying apparatus constructed and arranged, or configured with a physical structure to becapable of providing a therapeutically beneficial amount of water (H2O) vapour to a flow of air to ameliorate a medical respiratory condition of a patient.

[0550] 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.

[0551] 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.

[0552] Noise, radiated (acoustic) '. Radiated noise in the present document refers to noise which is carried to the patient by the ambient air. In one form, radiated noise may be quantified by measuring sound power / pressure levels of the object in question according to ISO 3744.

[0553] 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.

[0554] Oxygen enriched air '. Air with a concentration of oxygen greater than that of atmospheric air (21%), for example at least about 50% oxygen, at least about 60% oxygen, at least about 70% oxygen, at least about 80% oxygen, at least about 90% oxygen, at least about 95% oxygen, at least about 98% oxygen, or at least about 99% oxygen. “Oxygen enriched air” is sometimes shortened to “oxygen”.

[0555] Medical Oxygen'. Medical oxygen is defined as oxygen enriched air with an oxygen concentration of 80% or greater.

[0556] Patient'. A person, whether or not they are suffering from a respiratory condition.

[0557] Pressure: Force per unit area. Pressure may be expressed in a range of units, including cmFFO, g-f / cm2and hectopascal. 1 cmFFO is equal to 1 g-f / cm2and is approximately 0.98 hectopascal (1 hectopascal = 100 Pa = 100 N / m2= 1 millibar ~ 0.001 atm). In this specification, unless otherwise stated, pressure is given in units of cmkhO.

[0558] The pressure in the patient interface is given the symbol Pm, while the treatment pressure, which represents a target value to be achieved by the interface pressure Pm at the current instant of time, is given the symbol Pt.

[0559] Respiratory Pressure Therapy. The application of a supply of air to an entrance to the airways at a treatment pressure that is typically positive with respect to atmosphere.

[0560] Ventilator'. A mechanical device that provides pressure support to a patient to perform some or all of the work of breathing.4.9.1.1 Materials & their properties

[0561] Hardness'. Refers to durometer or indentation hardness, which is a material property measured by indentation of an indentor (e.g., as measured in accordance with ASTM D2240).• ‘Soft’ materials may include silicone or thermo-plastic elastomer (TPE), and may, e.g. readily deform under finger pressure.• ‘Hard’ materials may include polycarbonate, polypropylene, and may not e.g.readily deform under finger pressure.

[0562] Silicone or Silicone Elastomer'. A synthetic rubber. In this specification, a reference to silicone is a reference to liquid silicone rubber (LSR) or a compression moulded silicone rubber (CMSR). One form of commercially available LSR is SILASTIC (included in the range of products sold under this trademark), manufactured by Dow Corning. Another manufacturer of LSR is Wacker. Unless otherwise specified to the contrary, an exemplary form of LSR has a Shore A (or Type A) indentation hardness in the range of about 35 to about 45 as measured using ASTM D2240.

[0563] Polycarbonate', a thermoplastic polymer of Bisphenol-A Carbonate.4.9.1.2 Mechanics

[0564] Axes:a. Neutral axis'. An axis in the cross-section of a beam or plate along which there are no longitudinal stresses or strains.b. Longitudinal axis'. An axis extending along the length of a shape. The axis generally passes through a center of the shape.c. Circumferential axis'. An axis oriented perpendicularly with respect to the longitudinal axis. The axis may be specifically present in pipes, tubes, cylinders, or similar shapes with a circular and / or elliptical cross section.

[0565] Deformation'. The process where the original geometry of a member changes when subjected to forces, e.g. a force in a direction with respect to an axis. The process may include stretching or compressing, bending and, twisting.

[0566] Elasticity '. The ability of a material to return to its original geometry after deformation.

[0567] Floppy structure or component: A structure or component that will change shape, e.g. bend, when caused to support its own weight, within a relatively short period of time such as 1 second.

[0568] Resilience'. Ability of a material to absorb energy when deformed elastically and to release the energy upon unloading.

[0569] Resilient'. Will release substantially all of the energy when unloaded. Includes e.g. certain silicones, and thermoplastic elastomers.

[0570] 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 20 to 30 cmH20 pressure.

[0571] 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.

[0572] Stiffness (or rigidity) of a structure or component: The ability of the structure or component to resist deformation in response to an applied load. The load may be a force or a moment, e.g. compression, tension, bending or torsion. The structure or component may offer different resistances in different directions. The inverse of stiffness is flexibility.

[0573] Viscous'. The ability of a material to resist flow.

[0574] Visco-elasticity : The ability of a material to display both elastic and viscous behaviour in deformation.

[0575] Yield: The situation when a material can no longer return back to its original geometry after deformation.4.9.1.3 Structural Elements

[0576] Compression member: A structural element that resists compression forces.

[0577] Elbow. An elbow is an example of a structure that directs an axis of flow of air travelling therethrough to change direction through an angle. In one form, the angle may be approximately 90 degrees. In another form, the angle may be more, or less than 90 degrees. The elbow may have an approximately circular cross-section. In another form the elbow may have an oval or a rectangular cross-section. In certain forms an elbow may be rotatable with respect to a mating component, e.g. about 360 degrees. In certain forms an elbow may be removable from a mating component, e.g. via a snap connection. In certain forms, an elbow may be assembled to a mating component via a one-time snap during manufacture, but not removable by a patient.

[0578] 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.

[0579] 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.

[0580] Thin structures:a. Beams,i. A beam may be relatively long in one dimension compared to the other two dimensions such that the smaller dimensions are comparatively thin compared to the long dimension b. Membranes,i. Relatively long in two dimensions, with one thin dimension.Readily deforms in response to bending forces. Resists being stretched, (might also resist compression).c. Plates & Shellsi. These may be relatively long in two directions, with one thin dimension. They may have bending, tensile, and / or compressive stiffness.

[0581] Thick structures: Solids

[0582] 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.

[0583] 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.

[0584] Stiffener. A stiffener will be taken to mean a structural component designed to increase the bending resistance of another component in at least one direction.

[0585] 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.

[0586] Swivel (noun) '. A subassembly of components configured to rotate about a common axis, preferably independently, preferably under low torque. In one form, the swivel may be constructed to rotate through an angle of at least 360 degrees. In another form, the swivel may be constructed to rotate through an angle less than 360 degrees. When used in the context of an air delivery conduit, the sub-assembly of components preferably comprises a matched pair of cylindrical conduits. There may be little or no leak flow of air from the swivel in use.4.9.2 Respiratory cycle

[0587] Apnea. According to some definitions, an apnea is said to have occurred when flow falls below a predetermined threshold for a duration, e.g. 10 seconds. An obstructive apnea will be said to have occurred when, despite patient effort, some obstruction of the airway does not allow air to flow. A central apnea will be said to have occurred when an apnea is detected that is due to a reduction in breathing effort, or the absence of breathing effort, despite the airway being patent. A mixed apnea occurs when a reduction or absence of breathing effort coincides with an obstructed airway.

[0588] Breathing rate '. The rate of spontaneous respiration of a patient, usually measured in breaths per minute.

[0589] Duty cycle '. The ratio of inhalation time, Ti to total breath time, Ttot.

[0590] Effort (breathing): The work done by a spontaneously breathing person attempting to breathe.

[0591] Expiratory portion of a breathing cycle: The period from the start of expiratory flow to the start of inspiratory flow.

[0592] 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.

[0593] Types of flow limited inspiratory waveforms:(i) Flattened: Having a rise followed by a relatively flat portion, followed by a fall.(ii) M-shaped: Having two local peaks, one at the leading edge, and one at the trailing edge, and a relatively flat portion between the two peaks.(iii) Chair-shaped: Having a single local peak, the peak being at the leading edge, followed by a relatively flat portion.(iv) Reverse-chair shaped: Having a relatively flat portion followed by single local peak, the peak being at the trailing edge.

[0594] Hypopnea'. According to some definitions, a hypopnea is taken to be a reduction in flow, but not a cessation of flow. In one form, a hypopnea may be said to have occurred when there is a reduction in flow below a threshold rate for a duration. A central hypopnea will be said to have occurred when a hypopnea is detected that is due to a reduction in breathing effort. In one form in adults, either of the following may be regarded as being hypopneas:(i) a 30% reduction in patient breathing for at least 10 seconds plus an associated 4% desaturation; or(ii) a reduction in patient breathing (but less than 50%) for at least 10 seconds, with an associated desaturation of at least 3% or an arousal.

[0595] Hyperpnea'. An increase in flow to a level higher than normal.

[0596] 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.

[0597] Patency (airway): The degree of the airway being open, or the extent to which the airway is open. A patent airway is open. Airway patency may be quantified, for example with a value of one (1) being patent, and a value of zero (0), being closed (obstructed).

[0598] Positive End-Expiratory Pressure (PEEP) '. The pressure above atmosphere in the lungs that exists at the end of expiration.

[0599] Peak flow rate (Qpeak): The maximum value of flow rate during the inspiratory portion of the respiratory flow waveform.

[0600] 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.

[0601] Tidal volume (Vt): The volume of air inhaled or exhaled during normal breathing, when extra effort is not applied. In principle the inspiratory volume Vi (the volume of air inhaled) is equal to the expiratory volume Ve (the volume of air exhaled), and therefore a single tidal volume Vt may be defined as equal to either quantity. In practice the tidal volume Vt is estimated as some combination, e.g. the mean, of the inspiratory volume Vi and the expiratory volume Ve.

[0602] Inhalation Time (Ti): The duration of the inspiratory portion of the respiratory flow rate waveform.

[0603] Exhalation Time (Te) The duration of the expiratory portion of the respiratory flow rate waveform.

[0604] 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.

[0605] 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.

[0606] 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).

[0607] 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.4.9.3 Ventilation

[0608] 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.

[0609] 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.

[0610] 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.

[0611] Expiratory positive airway pressure (EPAP): a base pressure, to which a pressure varying within the breath is added to produce the desired interface pressure which the ventilator will attempt to achieve at a given time.

[0612] End expiratory pressure (EEP): Desired interface pressure which the ventilator will attempt to achieve at the end of the expiratory portion of the breath. If the pressure waveform template 11( ) is zero-valued at the end of expiration, i.e. n( ) = 0 when = 1, the EEP is equal to the EPAP.

[0613] Inspiratory positive airway pressure (IPAP): Maximum desired interface pressure which the ventilator will attempt to achieve during the inspiratory portion of the breath.

[0614] 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.

[0615] 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.

[0616] 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. Ifhowever, the device is unable to detect a breath within a predetermined period of time, the device will automatically initiate delivery of the breath.

[0617] Swing: Equivalent term to pressure support.

[0618] Triggered: When a ventilator, or other respiratory therapy device such as an RPT device or portable oxygen concentrator, delivers a volume of breathable gas to a spontaneously breathing patient, it is said to be triggered to do so. Triggering usually takes place at or near the initiation of the respiratory portion of the breathing cycle by the patient's efforts.4.9.4 Anatomy4.9.4.1 Anatomy of the face

[0619] Ala: the external outer wall or "wing" of each nostril (plural: alar)

[0620] Alar angle: An angle formed between the ala of each nostril.

[0621] Alare: The most lateral point on the nasal ala.

[0622] 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.

[0623] Auricle: The whole external visible part of the ear.

[0624] (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.

[0625] (nose) Cartilaginous framework: The cartilaginous framework of the nose comprises the septal, lateral, major and minor cartilages.

[0626] Columella: the strip of skin that separates the nares and which runs from the pronasale to the upper lip.

[0627] 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.

[0628] Frankfort horizontal plane: A line extending from the most inferior point of the orbital margin to the left tragion. The tragi on is the deepest point in the notch superior to the tragus of the auricle.

[0629] Glabella: Located on the soft tissue, the most prominent point in the midsagittal plane of the forehead.

[0630] 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.

[0631] Lip, lower (labrale inferius): The lip extending between the subnasale and the mouth.

[0632] Lip, upper (labrale superius): The lip extending between the mouth and the supramenton.

[0633] 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.

[0634] 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.

[0635] Naso-labial sulcus or Naso-labial fold: The skin fold or groove that runs from each side of the nose to the comers of the mouth, separating the cheeks from the upper lip.

[0636] Naso-labial angle: The angle between the columella and the upper lip, while intersecting subnasale.

[0637] Otobasion inferior: The lowest point of attachment of the auricle to the skin of the face.

[0638] Otobasion superior: The highest point of attachment of the auricle to the skin of the face.

[0639] 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.

[0640] Philtrum: the midline groove that runs from lower border of the nasal septum to the top of the lip in the upper lip region.

[0641] Pogonion: Located on the soft tissue, the most anterior midpoint of the chin.

[0642] Ridge (nasal): The nasal ridge is the midline prominence of the nose, extending from the Sellion to the Pronasale.

[0643] Sagittal plane: A vertical plane that passes from anterior (front) to posterior (rear). The midsagittal plane is a sagittal plane that divides the body into right and left halves.

[0644] Sellion: Located on the soft tissue, the most concave point overlying the area of the frontonasal suture.

[0645] Septal cartilage (nasal): The nasal septal cartilage forms part of the septum and divides the front part of the nasal cavity.

[0646] Subalare: The point at the lower margin of the alar base, where the alar base joins with the skin of the superior (upper) lip.

[0647] Subnasal point: Located on the soft tissue, the point at which the columella merges with the upper lip in the midsagittal plane.

[0648] Supramenton: The point of greatest concavity in the midline of the lower lip between labrale inferius and soft tissue pogonion

[0649] Anatomy of the skull

[0650] Frontal bone: The frontal bone includes a large vertical portion, the squama frontalis, corresponding to the region known as the forehead.

[0651] Mandible: The mandible forms the lower jaw. The mental protuberance is the bony protuberance of the jaw that forms the chin.

[0652] 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.

[0653] 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.

[0654] 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.

[0655] 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.

[0656] Orbit: The bony cavity in the skull to contain the eyeball.

[0657] Parietal bones: The parietal bones are the bones that, when joined together, form the roof and sides of the cranium.

[0658] 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.

[0659] 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.4.9.4.1 Anatomy of the respiratory system

[0660] 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.

[0661] Larynx: The larynx, or voice box houses the vocal folds and connects the inferior part of the pharynx (hypopharynx) with the trachea.

[0662] 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.

[0663] 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.

[0664] 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).4.9.5 Patient interface

[0665] 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 CO2 rebreathing by a patient.

[0666] Headgear: Headgear will be taken to mean a form of positioning and stabilising structure designed to hold a device, e.g., a mask, on a head.

[0667] 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.

[0668] 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.

[0669] Vent: (noun): A structure that allows a flow of air from an interior of the mask, or conduit, to ambient air for clinically effective washout of exhaled gases. For example, a clinically effective washout may involve a flow rate of about 10 litres per minute to about 100 litres per minute, depending on the mask design and treatment pressure.4.10 OTHER REMARKS

[0670] A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in Patent Office patent files or records, but otherwise reserves all copyright rights whatsoever.

[0671] Unless the context clearly dictates otherwise and where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit, between the upper and lower limit of that range, and any other stated or intervening value in that stated range is encompassed within the technology. The upper and lower limits of these intervening ranges, which may be independently included in the intervening ranges, are also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the technology.

[0672] Furthermore, where a value or values are stated herein as being implemented as part of the technology, it is understood that such values may be approximated, unless otherwise stated, and such values may be utilized to any suitable significant digit to the extent that a practical technical implementation may permit or require it.

[0673] Furthermore, “approximately”, “substantially”, “about”, or any similar term used herein means + / - 5-10% of the recited value.

[0674] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this technology belongs. Although any methods and materials similar orIllequivalent to those described herein can also be used in the practice or testing of the present technology, a limited number of the exemplary methods and materials are described herein.

[0675] When a particular material is identified as being used to construct a component, obvious alternative materials with similar properties may be used as a substitute. Furthermore, unless specified to the contrary, any and all components herein described are understood to be capable of being manufactured and, as such, may be manufactured together or separately.

[0676] It must be noted that as used herein and in the appended claims, the singular forms "a", "an", and "the" include their plural equivalents, unless the context clearly dictates otherwise.

[0677] All publications mentioned herein are incorporated herein by reference in their entirety to disclose and describe the methods and / or materials which are the subject of those publications. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present technology is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates, which may need to be independently confirmed.

[0678] 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.

[0679] The subject headings used in the detailed description are included only for the ease of reference of the reader and should not be used to limit the subject matter found throughout the disclosure or the claims. The subject headings should not be used in construing the scope of the claims or the claim limitations.

[0680] 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 stepsin 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.

[0681] It is therefore to be understood that numerous modifications may be made to the illustrative examples and that other arrangements may be devised without departing from the spirit and scope of the technology.4.11 REFERENCE SIGNS LIST

Claims

1. 5 CLAIMS1. A conduit configured to convey pressurized breathable gas from an RPT device to a patient interface, the conduit comprising:a first gas flow path configured to convey the pressurized breathable gas from the RPT device, the first gas flow path having a first length; anda second gas flow path that is configured to convey gas washout from the patient interface, the second gas flow path having a second length that is different from the first length.

2. The conduit of claim 1, wherein the first and second gas flow paths are concentric.

3. The conduit of any one of claims 1 to 2, wherein the first gas flow path is located inside the second gas flow path.

4. The conduit of claim 1, wherein the first and second gas flow paths are side by side.

5. The conduit of any one of claims 1 to 4, wherein the first and second gas flow paths are separated by a semi-permeable membrane or wall that is permeable to moisture but is not permeable to carbon dioxide.

6. The conduit of claim 5, wherein one or more spacers separate the semi-permeable membrane from an outer wall of the conduit.

7. The conduit of any one of claims 1 to 6, wherein the conduit comprises an opening on a radial wall that is in communication with the second gas flow path, the opening being positioned to direct gas washout flowing through the second gas flow path to vent to atmosphere through the radial wall of the conduit.

8. The conduit of any one of claims 1 to 7, wherein the second gas flow path is configured to freely move within the first gas flow path.

9. The conduit of any one of claims 1 to 7, wherein the second gas flow path is fixed in place relative to the first gas flow path.

10. The conduit of any one of claims 1 to 8, further comprising:a first cuff at a first end of the conduit; anda second cuff at a second end of the conduit.

11. The conduit of claim 10, wherein the first cuff is configured to connect to an outlet of the RPT device and the second cuff is configured to connect to a patient interface connector or to an inlet of the patient interface.

12. The conduit of claim 10, further comprising an adaptor with a first end configured to connect to the first cuff, a second end configured to connect to an outlet of the RPT device, and a vent opening in a radial wall of the conduit between the first and second ends.

13. The conduit of claim 12, wherein the vent opening is pneumatically connected to the second gas flow path.

14. The conduit of any one of claims 1 to 13, further comprising one or more heating wires configured to heat gas flowing through the conduit; and further comprising one or more sensing wires.

15. A conduit configured to convey pressurized breathable gas from an RPT device to a patient interface, the conduit comprising:an outer wall that encloses a first lumen configured to convey the pressurized breathable gas from the RPT device; anda venting tube located inside the first lumen and configured to convey gas washout from the patient interface,wherein the venting tube extends beyond the first lumen.

16. The conduit of claim 15, wherein the venting tube comprises a second lumen bound by a semi-permeable wall that is permeable to moisture but is not permeable to carbon dioxide.

17. The conduit of any one of claims 15 to 16, wherein the venting tube is configured to freely move within the first lumen.

18. The conduit of any one of claims 15 to 16, wherein the venting tube is fixed in place within the first lumen.

19. The conduit of any one of claims 15 to 18, further comprising:a first cuff at a first end of the conduit; anda second cuff at a second end of the conduit,wherein the first cuff is configured to connect to an outlet of the RPT device and the second cuff is configured to connect to a patient interface connector or to an inlet of the patient interface.

20. The conduit of claim 19, wherein the venting tube is configured to extend beyond the second cuff.

21. The conduit of any one of claims 15 to 20, further comprising one or more heating wires configured to heat gas flowing through the conduit; and further comprising one or more sensing wires.

22. The conduit of any one of claims 15 to 21, wherein the conduit is flexible and retractable.

23. The conduit of any one of claims 15 to 22, wherein the venting tube is movable relative to the outer wall of the conduit in an axial direction.

24. The conduit of any one of claims 15 to 23, wherein the venting tube is attached to the outer wall of the conduit by one or more arms.

25. An air delivery system comprising:the conduit of any one of claims 15 to 24; andthe RPT device,wherein the RPT device comprises a vent path configured to pneumatically connect the venting tube to atmosphere when the conduit is attached to the RPT device.

26. The air delivery system of claim 25, further comprising a filter positioned to filter gas washout flowing through the vent path of the RPT device.

27. The air delivery system of any one of claims 25 to 26, wherein the venting tube is axially movable relative to the outer wall of the conduit so that when the venting tube is in a first position relative to the outer wall of the conduit, the second lumen is blocked at the RPT device end so that gas washout cannot exit from the venting tube to the RPT device.

28. The air delivery system of claim 27, wherein the venting tube is axially movable relative to the outer wall of the conduit so that when the venting tube is axially moved to a second position, gas washout is allowed to flow into the RPT device from the venting tube.

29. The air delivery system of any one of claims 27 to 28, wherein the venting tube is biased to the first position and is configured to be moved to the second position in response to a threshold pressure in the venting tube.

30. A conduit configured to convey pressurized breathable gas from an RPT device to a patient interface, the conduit comprising:a first gas flow path configured to convey the pressurized breathable gas from the RPT device; anda second gas flow path that is configured to convey gas washout from the patient interface,wherein the first gas flow path is inside the second gas flow path.

31. The conduit of claim 30, wherein the first and second gas flow paths are concentric.

32. The conduit of any one of claims 30 to 31, wherein the first and second gas flow paths are separated by a semi-permeable membrane or wall that is permeable to moisture but is not permeable to carbon dioxide.

33. The conduit of claim 32, wherein one or more spacers separate the semi-permeable membrane from an outer wall of the conduit.

34. The conduit of any one of claims 30 to 33, wherein the conduit comprises an opening on a radial wall that is in communication with the second gas flow path, the opening being positioned to direct gas washout flowing through the second gas flow path to vent to atmosphere through the radial wall of the conduit.

35. The conduit of any one of claims 30 to 34, further comprising:a first cuff at a first end of the conduit; anda second cuff at a second end of the conduit.

36. The conduit of claim 35, wherein the first cuff is configured to connect to an outlet of the RPT device and the second cuff is configured to connect to a patient interface connector or to an inlet of the patient interface.

37. The conduit of claim 36, further comprising an adaptor with a first end configured to connect to the first cuff, a second end configured to connect to an outlet of the RPT device, and a vent opening in a radial wall of the conduit between the first and second ends.

38. The conduit of claim 37, wherein the vent opening is pneumatically connected to the second gas flow path.

39. The conduit of any one of claims 30 to 38, further comprising one or more heating wires configured to heat gas flowing through the conduit; and further comprising one or more sensing wires.

40. A conduit configured to convey pressurized breathable gas from an RPT device to a patient interface, the conduit comprising:an outer wall that encloses a first lumen configured to convey gas washout from the patient interface; anda supply tube located inside the first lumen and configured to convey the pressurized breathable gas from the RPT device.

41. The conduit of claim 40, wherein the supply tube comprises a second lumen bound by a semi-permeable wall that is permeable to moisture but is not permeable to carbon dioxide.

42. The conduit of any one of claims 40 to 41, wherein the supply tube is configured to freely move within the first lumen.

43. The conduit of any one of claims 40 to 41, wherein the supply tube is fixed in place within the first lumen.

44. The conduit of any one of claims 40 to 43, further comprising:a first cuff at a first end of the conduit; anda second cuff at a second end of the conduit,wherein the first cuff is configured to connect to an outlet of the RPT device and the second cuff is configured to connect to a patient interface connector or to an inlet of the patient interface.

45. The conduit of any one of claims 40 to 44, further comprising one or more heating wires configured to heat gas flowing through the conduit; and further comprising one or more sensing wires.

46. The conduit of any one of claims 40 to 45, wherein the conduit is flexible and retractable.

47. The conduit of any one of claims 40 to 46, wherein the supply tube is movable relative to the outer wall of the conduit in an axial direction.

48. The conduit of any one of claims 40 to 47, wherein the supply tube is attached to the outer wall of the conduit by one or more arms.

49. An air delivery system comprising:the conduit of any one of claims 40 to 48; andthe RPT device,wherein the RPT device comprises a vent path configured to convey gas washout from the conduit to atmosphere when the conduit is attached to the RPT device.

50. The air delivery system of claim 49, further comprising a filter positioned to filter gas washout flowing through the vent path of the RPT device.

51. The air delivery system of any one of claims 49 to 50, wherein the supply tube is axially movable relative to the outer wall of the conduit so that when the supply tube is in a first position relative to the outer wall of the conduit, the first lumen is blocked at the RPT device end so that gas washout cannot exit from the venting tube to the RPT device.

52. The air delivery system of claim 51, wherein the supply tube is axially movable relative to the outer wall of the conduit so that when the supply tube is axially moved to a second position, gas washout is allowed to flow into the RPT device from the first lumen.

53. The air delivery system of any one of claims 49 to 52, wherein the supply tube is biased to the first position and is configured to be moved to the second position in response to a threshold pressure in the supply tube.

54. A connector configured to convey pressurized breathable gas from conduit to a patient interface and to convey gas washout from a patient interface to the conduit, the connector comprising:a first end configured to connect to an inlet of a patient interface;a second end configured to connect to an air delivery tube;a lumen extending from the first end to the second end, the lumen being configured to convey the pressurized gas from conduit to the patient interface; anda venting tube configured to convey gas washout from the patient interface to the conduit,wherein the venting tube extends beyond the lumen and through the first end.

55. The connector of claim 54, wherein the connector is in the form of an elbow.

55. A patient interface configured to deliver pressurized breathable gas to a patient’s airways, the patient interface comprising:a cushion configured to sealingly engage the patient’s face;a plenum chamber; anda positioning and stabilizing structure comprising:one or more headgear straps; andone or more air delivery tubes attached to the one or more headgear straps and connected to an inlet of the plenum chamber,wherein the one or more air delivery tubes is configured to extend along a patient’s face,wherein each of the one or more air delivery tubes comprises an internal wall that forms a first lumen and a second lumen within the air delivery tube,wherein the first lumen is configured to convey the pressurized breathable gas to the plenum chamber, andwherein the second lumen is configured to convey gas washout from the plenum chamber.

56. The patient interface of claim 55, wherein the internal wall is permeable to moisture but not carbon dioxide.

57. A conduit configured to convey pressurized breathable gas from a first end to a second end and configured to convey gas washout from the second end to the first end.

58. A respiratory therapy device configured to measure a level of carbon dioxide in gas washout flowing through a conduit, the respiratory therapy device comprising:an RPT device configured to pressurize a flow of breathable gas;a conduit configured to convey the pressurized breathable gas to a patient interface and configured to convey gas washout from the patient interface to the RPT device;a sensor configured to measure an amount of carbon dioxide flowing through the conduit; anda controller configured to determine a condition of a patient based on the measured level of carbon dioxide in the gas washout.

59. The respiratory system of claim 58, wherein the condition of the patient corresponds to a patient’s metabolism, and / or cardiac output.

60. The respiratory system of any one of claims 58 to 59, wherein the controller is configured to determine a volume of a dead space in the patient interface based on the measured amount of carbon dioxide.

61. The respiratory system of claim 60, wherein the controller is configured to increase an amount of carbon dioxide in a patient interface in response to the measured amount of carbon dioxide.

62. A respiratory therapy device configured to deliver pressurized breathable gas to a patient’s airways, the respiratory therapy device comprising:an RPT device configured to pressurize a flow of breathable gas;a conduit configured to convey the pressurized breathable gas to a patient interface and configured to convey gas washout from the patient interface to the RPT device;a sensor configured to measure a characteristic of the gas washout received by the RPT device from the conduit; anda controller configured to adjust a flow rate and / or a pressure of the pressurized flow of breathable gas generated by the RPT device.

63. The respiratory system of claim 62, wherein the characteristic of the gas washout is pressure.

64. The respiratory system of any one of claims 62 to 63, wherein the characteristic is flow rate.

65. The respiratory system of any one of claims 61 to 64, further comprising the patient interface, wherein the patient interface is configured to receive the pressurized breathable gas from the conduit and is configured to discharge gas washout into the conduit.

66. A connector configured to convey pressurized breathable gas from conduit to a patient interface and to convey gas washout from a patient interface to the conduit, the connector comprising:a first portion attachable or attached to an inlet of a patient interface; and a second portion configured to connect to an air delivery tube,wherein the first portion comprises a plurality of vent openings and has a larger diameter than the second portion.

67. The connector of claim 66, further comprising a transition from the first portion to the second portion in the form of a shoulder.

68. The connector of any one of claims 66 to 67, wherein the outer surface of the second portion is tapered so that the outer diameter of the second portion increases toward the first portion.

69. A patient interface assembly comprising:a patient interface configured to sealingly engage a patient’s face, the patient interface comprising an air inlet;the connector of any one of claims 66 to 68; anda conduit comprising a cuff configured to be secured to the connector.

70. The patient interface assembly of claim 69, wherein the cuff comprises a first portion with a first diameter and a second portion with a second diameter smaller than the first diameter, wherein the first portion is configured to occlude the vent openings in the connector when the cuff is secured to the connector.

71. The patient interface assembly of claim 70, wherein the cuff further comprises a should that forms a transition from the first portion to the second portion.

72. The patient interface assembly of any one of claims 69 to 71, wherein the conduit further comprises a venting tube within the lumen of the conduit, the venting tube being configured to extend into the connector when the cuff of the conduit is secured to the connector.

73. A conduit configured to convey pressurized breathable gas from an RPT device to a patient interface, the conduit comprising:a first gas flow path configured to convey the pressurized breathable gas from the RPT device;a second gas flow path that is configured to convey gas washout from the patient interface;and a cuff configured to secure the conduit to the patient interface, the cuff comprising a first portion and a second portion that has a smaller diameter than the first portion,wherein the first gas flow path is inside the second gas flow path, wherein the diameter of the second gas flow path is equal to the inner diameter of the second portion of the cuff.

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