Mixed positive airway pressure

Abstract

A respiratory therapy device is configured to supply pressurized respiratory gas to a patient's airways The respiratory therapy device includes a blower configured to pressurize a flow of respiratory gas. A controller is configured to determine a current breathing phase of the patient and control the blower based on the breathing phase of the patient. The controller is configured to cause the blower to discharge the respiratory gas at a base pressure during the patient's inspiratory phase of the patient's breathing cycle. The controller is configured to cause the blower to increase the pressure of the respiratory gas at least during the beginning of the patient's expiratory phase of the patient's breathing cycle.

Description

MIXED POSITIVE AIRWAY PRESSURE1 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 to stop breathing for periods typically of 30 to 120 seconds in duration, sometimes 200 to 300 times per night. It often causes excessive daytime somnolence, and it maycause 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 dividedinto 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 airwayocclusion, 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 such as nasal HFT, the patient interface is configured to insufflate the nares but specifically to avoid a complete seal. One example of such a patient interface is a nasal cannula.

[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 use a patient may not comply with therapy. Since it is often recommended that a patient regularly wash their mask, if a mask is difficult to clean (e.g., difficult to assemble ordisassemble), 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 betweenthe 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 of nasal 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.1.2.3.1.4 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 interfaces allow 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 treatmentsystem 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 interface produces humidified gas that minimizes drying of the nasal mucosa and increases patient airway comfort. In addition, in cooler climates, warm air applied generally to the face area in and about the patient interface is more comfortable than cold air.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 ofrespiratory 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 method and / or a device for supplying positive pressure air to a patient during at least part of the inspiration and expiration stages of the respiratory cycle, wherein at least during a portion of the expiration stage, the pressure of the positive pressure air is more than the pressure of the positive pressure air supplied during the inspiration stage.

[0072] Another aspect of one form of the present technology comprises a respiratory therapy device configured to supply pressurized respiratory gas to a patient’s airways, the respiratory therapy device comprising: a blower configured to pressurize a flow of respiratory gas; and a controller configured to determine a current breathing phase of the patient and control the blower based on the breathing phase of the patient, wherein the controller is configured to cause the blower to discharge the respiratory gas at a base pressure during the patient’s inspiratory phase of the patient’s breathing cycle, and wherein the controller is configured to cause the blower to increase the pressure of the respiratory gas during the patient’s expiratory phase of the patient’s breathing cycle.

[0073] The base pressure may be a minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face, the base pressure may be a minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration, the base pressure may be the lower one of: a minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face, or a minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration. A transition from the base pressure to the increased pressure may be abrupt or gradual.

[0074] Another aspect of one form of the present technology is a respiratory therapy system comprising: a patient interface configured to sealingly engage a patient’s face; the respiratory therapy device according to any one of the configurations discussed above; and an air delivery tube configured to convey the pressurized respiratory gas from the respiratory therapy device to the patient interface.

[0075] Another aspect of one form of the present technology is a respiratory therapy device configured to supply pressurized respiratory gas to a patient’s airways, the respiratory therapy device comprising: a blower configured to pressurize a flow ofrespiratory gas; and a controller configured to determine a current breathing phase of the patient and control the blower based on the breathing phase of the patient, wherein the controller is configured to control the blower in three stages, and wherein in the first stage, the controller controls the blower to discharge the respiratory gas at a base pressure for a first predetermined amount of time, in the second stage, the controller controls the blower to discharge the respiratory gas at an increased pressure for a second predetermined amount of time, and in the third stage, the controller controls the blower to ramp down the pressure of the respiratory gas for a third predetermined amount of time.

[0076] The controller is configured to operate in the first stage during the patient’s inspiration phase, the controller is configured to operate in the second and third stages during the patient’s expiratory phase, and the third predetermined period of time may be greater than the first and second predetermined periods of time. The second predetermined period of time may be greater than the first predetermined period of time and the third predetermined period of time may be twice as long as the first predetermined period of time. The first predetermined period of time may be four seconds, the second predetermined period of time may be seven seconds, and the third predetermined period of time may be eight seconds.

[0077] Another aspect of one form of the present technology is a respiratory therapy system comprising: a patient interface configured to sealingly engage a patient’s face; the respiratory therapy device according to any one of the configurations discussed above; and an air delivery tube configured to convey the pressurized respiratory gas from the respiratory therapy device to the patient interface.

[0078] Another aspect of one form of the present technology is ta patient interface configured to deliver positively pressurized respiratory gas to a patient’s airways, the patient interface comprising: a sealing surface configured to sealingly engage the patient’s face; a plenum chamber with an air inlet configured to receive the pressurized respiratory gas; and a variable vent arrangement configured to discharge gas washout from the plenum chamber, wherein the variable vent arrangement is configured to vary the amount of gas washout discharged from the plenum chamber depending on the patient’s breathing phase, and wherein the variable vent arrangement is configured to discharge a greater volume of gas washout during the patient’s inspiratory phase and discharge less or no gas washout during the patient’s expiratory phase.

[0079] The variable vent arrangement includes an array of vent openings and a membrane configured to move between a first position that completely covers the vent openings and a second position that leaves the vent openings completely unobstructed. The membrane is configured to be positioned at intermediate positions between the first and second position. There may be a finite number of intermediate positions or an infinite number of intermediate positions. The sealing surface is in the form of nasal pillows, a nasal cushion, or a full face cushion.

[0080] A respiratory therapy system comprising: the patient interface according to any of the configurations disclosed above; a respiratory therapy device configured to pressurize a flow of respiratory gas; and an air delivery tube configured to convey the pressurized respiratory gas from the respiratory therapy device to the patient interface.

[0081] Another aspect of one form of the present technology is a patient interface configured to deliver pressurized respiratory gas to a patient’s airways, the patient interface comprising: a sealing surface configured to sealingly engage the patient’s face; a plenum chamber with an air inlet configured to receive the pressurized respiratory gas; and a variable vent arrangement configured to discharge gas washout from the plenum chamber, the variable vent arrangement being configured to vary the amount of gas washout discharged from the plenum chamber depending on the patient’s breathing phase, and the variable vent arrangement being configured discharge a greater volume of gas washout during the patient’s inspiratory phase; and discharge less or no gas washout during the patient’s expiratory phase; a respiratory therapy device configured to pressurize a flow of respiratory gas, the respiratory therapy device comprising: a blower configured to pressurize a flow of respiratory gas; and a controller configured to determine a current breathing phase of the patient and control the blower based on the breathing phase of the patient, the controller being configured to cause the blower to discharge the respiratory gas at a base pressure during the patient’s inspiratory phase of the patient’s breathing cycle, and the controller being configured to cause the blower to increase the pressure of the respiratory gas during the patient’s expiratory phase of the patient’s breathing cycle; and an air delivery tube configured to convey the pressurized respiratory gas from the respiratory therapy device to the patient interface.

[0082] The base pressure may be a minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face. The basepressure may be a minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration. The base pressure may be the lower one of: a minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face, or a minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration. A transition from the base pressure to the increased pressure may be abrupt or gradual.

[0083] The variable vent arrangement comprises an array of vent openings and a membrane configured to move between a first position that completely covers the vent openings and a second position that leaves the vent openings completely unobstructed. The membrane may be configured to be positioned at intermediate positions between the first and second position. There may be a finite number of intermediate positions or an infinite number of intermediate positions. The sealing surface is in the form of nasal pillows, a nasal cushion, or a full face cushion.

[0084] Another aspect of one form of the present technology is a respiratory therapy system comprising: a patient interface configured to deliver pressurized respiratory gas to a patient’s airways, the patient interface comprising: a sealing surface configured to sealingly engage the patient’s face; a plenum chamber with an air inlet configured to receive the pressurized respiratory gas; and a variable vent arrangement configured to discharge gas washout from the plenum chamber, the variable vent arrangement being configured to vary the amount of gas washout discharged from the plenum chamber depending on the patient’s breathing phase, and the variable vent arrangement being configured discharge a greater volume of gas washout during the patient’s inspiratory phase and discharge less or no gas washout during the patient’s expiratory phase; a respiratory therapy device configured to pressurize a flow of respiratory gas, the respiratory therapy device comprising: a blower configured to pressurize a flow of respiratory gas; a controller configured to determine a current breathing phase of the patient and control the blower based on the breathing phase of the patient, the controller being configured to control the blower in three stages, in the first stage, the controller controls the blower to discharge the respiratory gas at a base pressure for a first predetermined amount of time, in the second stage, the controller controls the blower to discharge the respiratory gas at an increased pressure for a second predetermined amount of time, and in the third stage, the controller controls the blower to ramp down the pressure of the respiratory gas for a third predetermined amount of time; and an air delivery tube configured to conveythe pressurized respiratory gas from the respiratory therapy device to the patient interface.

[0085] The controller is configured to operate in the first stage during the patient’s inspiration phase. The controller is configured to operate in the second and third stages during the patient’s expiratory phase. The third predetermined period of time may be greater than the first and second predetermined periods of time. The second predetermined period of time may be greater than the first predetermined period of time. The third predetermined period of time may be twice as long as the first predetermined period of time. The first predetermined period of time may be four seconds, the second predetermined period of time may be seven seconds, and the third predetermined period of time may be eight seconds.

[0086] The variable vent arrangement comprises an array of vent openings and a membrane configured to move between a first position that completely covers the vent openings and a second position that leaves the vent openings completely unobstructed. The membrane is configured to be positioned at intermediate positions between the first and second position. There may be a finite number of intermediate positions or an infinite number of intermediate positions. The sealing surface is in the form of nasal pillows, a nasal cushion, or a full face cushion.

[0087] Another aspect of one form of the present technology is a method for supplying pressurized respiratory gas to a patient’s airways, the method comprising: determining a current breathing phase of the patient; and pressurizing the respiratory gas based on the current breathing phase of the patient, wherein the respiratory gas is pressurized to a base pressure during the patient’s inspiratory phase of the patient’s breathing cycle, and wherein the pressure of the respiratory gas is increased during the patient’s expiratory phase.

[0088] The base pressure may be a minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face. The base pressure may be a minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration. The base pressure may be the lower one of: a minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face, or a minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration. A transition from the base pressure to the increased pressure may be abrupt or gradual.

[0089] Another aspect of one form of the present technology is a method for supplying pressurized respiratory gas to a patient’s airways, the method comprising: determining a current breathing phase of the patient; and pressurizing a flow of respiratory gas based on the breathing phase of the patient, wherein the pressure of the respiratory gas is adjusted in three stages, in a first stage, the respiratory gas is pressurized to a base pressure for a first predetermined amount of time, in the second stage, the respiratory gas is pressurized to an increased pressure for a second predetermined amount of time, and in the third stage, the pressure of the respiratory gas is ramped down for a third predetermined amount of time.

[0090] The first stage occurs during the patient’s inspiration phase. The second and third stages occur during the patient’s expiratory phase. The third predetermined period of time may be greater than the first and second predetermined periods of time. The second predetermined period of time may be greater than the first predetermined period of time. The third predetermined period of time may be twice as long as the first predetermined period of time. The first predetermined period of time may be four seconds, the second predetermined period of time may be seven seconds, and the third predetermined period of time may be eight seconds.

[0091] Another aspect of one form of the present technology is a method for supplying pressurized respiratory gas to a patient’s airways, the method comprising: supplying a pressurized supply of respiratory gas to a patient interface; determining the patient’s breathing phase; adjusting an amount of gas washout discharged from the patient interface based on the patient’s breathing phase, wherein the volume of gas washout discharged during the patient’s inspiratory phase is greater than the volume of gas washout discharged during the patient’s expiratory phase.

[0092] Another aspect of one form of the present technology is a non-transitory computer readable storage medium storing computer executable instructions for use with a central controller of an RPT device, the computer executable instructions being configured to cause the RPT device to perform operations comprising: pressurizing respiratory gas based on the current breathing phase of a patient, wherein the respiratory gas is pressurized to a base pressure during the patient’s inspiratory phase of the patient’s breathing cycle, and wherein the pressure of the respiratory gas is increased during the patient’s expiratory phase.

[0093] Another aspect of one form of the present technology is a non-transitory computer readable storage medium storing computer executable instructions for usewith a central controller of an RPT device, the computer executable instructions being configured to cause the RPT device to perform operations comprising: pressurizing a flow of respiratory gas based on the breathing phase of the patient, wherein the pressure of the respiratory gas is adjusted in three stages, in a first stage, the respiratory gas is pressurized to a base pressure for a first predetermined amount of time, in the second stage, the respiratory gas is pressurized to an increased pressure for a second predetermined amount of time, and in the third stage, the pressure of the respiratory gas is ramped down for a third predetermined amount of time.

[0094] Another aspect of one form of the present technology is a method for retrofitting an RPT device to perform a respiratory therapy according to any one of the configurations disclosed above, the method comprising: creating a communication link between an external communication network or device and the RPT device; transmitting electrical signals from the external communication network or device to the RPT device through the communication link, the electrical signals including instructions for performing the respiratory therapy; and storing the instructions in a memory of the RPT device.

[0095] The electrical signals may be transmitted to the RPT device wirelessly or by wired connection. The instructions included in the electrical signals may replace existing instructions already stored in a memory of the RPT device when the electrical signals are transmitted to the RPT device. Alternatively, the instructions included in the electrical signals may be stored alongside existing instructions already stored in a memory of the RPT device when the electrical signals are transmitted to the RPT device.

[0096] 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.

[0097] An aspect of one form of the present technology is a method of manufacturing apparatus.

[0098] 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.

[0099] 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 personwho has limited dexterity, vision or by a person with limited experience in using this type of medical device.

[0100] 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.

[0101] 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.

[0102] The methods, systems, devices and apparatus described may be implemented so as to improve the functionality of a processor, such as a processor of a specific purpose computer, respiratory monitor and / or a respiratory therapy apparatus. Moreover, the described methods, systems, devices and apparatus can provide improvements in the technological field of automated management, monitoring and / or treatment of respiratory conditions, including, for example, sleep disordered breathing.

[0103] 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.

[0104] 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

[0105] 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

[0106] 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.

[0107] 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.

[0108] 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

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] Fig. 2G shows a side view of the superficial features of a nose.

[0116] Fig. 2H shows subcutaneal structures of the nose, including lateral cartilage, septum cartilage, greater alar cartilage, lesser alar cartilage, sesamoidcartilage, nasal bone, epidermis, adipose tissue, frontal process of the maxilla and fibrofatty tissue.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] Fig. 2L shows an anterolateral view of a nose.3.3 PATIENT INTERFACE

[0121] Fig. 3A shows a patient interface in the form of a nasal mask in accordance with one form of the present technology.

[0122] Fig. 3B shows a patient interface having conduit headgear, in accordance with one form of the present technology.

[0123] Fig. 3C 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.

[0124] Fig. 3D 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.

[0125] Figs. 3E-3F show perspective views of another exemplary patient interface.

[0126] Fig. 3G illustrates an exploded view of the patient interface of Figs. 3E and 3F.

[0127] Fig. 3H illustrates an exploded view of an alternative configuration of the patient interface of Figs. 3E and 3F.3.4 RPT DEVICE

[0128] Fig. 4 A shows an RPT device in accordance with one form of the present technology.

[0129] 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.

[0130] Fig. 4C is a schematic diagram of the electrical components of an RPT device in accordance with one form of the present technology.

[0131] Fig. 4C-1 is a schematic diagram illustrating the interconnection of various electrical components of the RPT device.

[0132] Fig. 4D is a schematic diagram of the algorithms implemented in an RPT device in accordance with one form of the present technology.

[0133] 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! 3.5 HUMIDIFIER

[0134] Fig. 5 A shows an isometric view of a humidifier in accordance with one form of the present technology.

[0135] 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

[0136] Fig. 6A shows a model typical breath waveform of a person while sleeping.

[0137] Fig. 6B shows an exemplary MPAP waveform.

[0138] Fig. 6C shows a comparison of various respiratory therapy waveforms.

[0139] Fig. 6D shows another exemplary MPAP waveform.

[0140] Figs. 6E-6G show block diagrams for retrofitting an RPT device to perform MPAP therapy.4 DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY

[0141] 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.

[0142] 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

[0143] 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.

[0144] 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.

[0145] In certain examples of the present technology, mouth breathing is limited, restricted or prevented.4.2 RESPIRATORY THERAPY SYSTEMS

[0146] 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

[0147] 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, a vent 3400, one form of connection port 3600 for connection to air circuit 4170, and a forehead support 3700. In some forms a functional aspect may be provided by one or more physical components. In 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.

[0148] 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, a vent 3400 and one form of connection port 3600 for connection to an air circuit (such as the air circuit 4170 shown in Figs. 1 A-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.

[0149] 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.

[0150] 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

[0151] In one form of the present technology, a seal-forming structure 3100 provides a target seal-forming region, and may additionally provide a cushioning function. The target seal-forming region is a region on the seal-forming structure 3100 where sealing may occur. The region where sealing actually occurs- the actual sealing surface- may change within a given treatment session, from day to day, and from patient to patient, depending on a range of factors including for example, where the patient interface was placed on the face, tension in the positioning and stabilising structure and the shape of a patient’s face.

[0152] In one form the target seal -forming region is located on an outside surface of the seal-forming structure 3100.

[0153] In certain forms of the present technology, the seal-forming structure 3100 is constructed from a biocompatible material, e.g. silicone rubber.

[0154] A seal -forming structure 3100 in accordance with the present technology may be constructed from a soft, flexible, resilient material such as silicone.

[0155] 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

[0156] 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.

[0157] 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.

[0158] In one form, the seal -forming structure may comprise a compression sealing portion or a gasket sealing portion. In use the compression sealing portion, or the gasket sealing portion is constructed and arranged to be in compression, e.g. as a result of elastic tension in the positioning and stabilising structure.

[0159] 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.

[0160] In one form, the seal -forming structure comprises a region having a tacky or adhesive surface.

[0161] 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

[0162] 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.

[0163] In one form, the seal-forming structure includes a saddle-shaped region constructed to form a seal in use on a nose bridge region or on a nose-ridge region of the patient's face.4.3.1.3 Upper lip region

[0164] 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.

[0165] In one form, the seal -forming structure includes a saddle-shaped region constructed to form a seal in use on an upper lip region of the patient's face.4.3.1.4 Chin-region

[0166] 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.

[0167] 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 Forehead region

[0168] In one form, the seal -forming structure that forms a seal in use on a forehead region of the patient's face. In such a form, the plenum chamber may cover the eyes in use.4.3.1.6 Nasal pillows

[0169] 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.

[0170] 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.4.3.1.7 Nose-only Masks

[0171] 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.

[0172] 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 interface 3000 shown in Fig. IB has this type of seal-forming structure 3100. This patient interface 3000 may deliver a supply of air or breathable gas to both nares of patient 1000 through a single orifice.

[0173] 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. 3B, 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 an inferior periphery of the patient’s nose including to an inferior and / or anterior surfaceof 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.

[0174] In some forms, a nose-only mask may comprise nasal pillows, described above.4.3.1.8 Nose and Mouth Masks

[0175] 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.

[0176] 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 Fig. 1C is 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 sealforming structure 3100 may be referred to as a “nose-and-mouth cushion”.

[0177] 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 includethe 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.

[0178] 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.

[0179] 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.

[0180] 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

[0181] The plenum chamber 3200 has a perimeter that is shaped to be complementary to the surface contour of the face of an average person in the region where a seal will form in use. In use, a marginal edge of the plenum chamber 3200 is positioned in close proximity to an adjacent surface of the face. Actual contact with the face is provided by the seal -forming structure 3100. The seal-forming structure 3100 may extend in use about the entire perimeter of the plenum chamber 3200. In some forms, the plenum chamber 3200 and the seal -forming structure 3100 are formed from a single homogeneous piece of material.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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

[0187] As shown in Figs. 3C and 3D, 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 three openings, although an alternate cushion may be formed with greater or fewer openings.

[0188] In some forms, the different openings may serve different functions. For example, some openings may be exclusively inlet openings, while other openings may be exclusively outlet openings.

[0189] In other forms, 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.

[0190] The plurality of openings may allow for a variety of configurations of air delivery to the plenum chamber 3200-1, 3200-2. 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 “tubedown” configuration (e.g., using a single conduit in front of the patient’s face).4.3.2.1.1 Nose and Mouth Mask

[0191] As shown in Fig. 3C, 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.

[0192] In some forms, the plenum chamber 3200-1 may also include at least one vent opening 3402-1 (see e.g., Fig. 3C). The vent opening 3402-1 may be disposed in a center of the plenum chamber 3200-1. For example, the vent opening 3402-1 may be disposed between the plenum chamber inlet ports 3254-1.

[0193] 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

[0194] 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.

[0195] As shown in Fig. 3D, 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.

[0196] In some forms, the plenum chamber 3200-2 may also include at least one vent opening 3402-2 (see e.g., Fig. 3D). The vent opening 3402-2 may be disposed in a center of the plenum chamber 3200-2. For example, the vent opening 3402-2 may be disposed between the plenum chamber inlet ports 3254-2.

[0197] 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

[0198] 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 may comprise and function as “headgear” since it engages the patient’s head in order to hold the patient interface 3000 in a sealing position. An example of a positioning and stabilising structure may be shown in Fig. 3 A.

[0199] 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).

[0200] 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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] In one form of the present technology, a positioning and stabilising structure 3300 is provided with a decoupling portion located between an anterior portion of the positioning and stabilising structure 3300, and a posterior portion of the positioning and stabilising structure 3300. The decoupling portion does not resist compression and may be, e.g. a flexible or floppy strap. The decoupling portion is constructed and arranged so that when the patient lies with their head on a pillow, the presence of the decoupling portion prevents a force on the posterior portion from being transmitted along the positioning and stabilising structure 3300 and disrupting the seal.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] 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.

[0212] 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,

[0213] 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

[0214] 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. 3B, 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.

[0215] In the form of the present technology illustrated in Fig. 3B, the positioning and stabilising structure 3300 comprises two tubes 3350, each tube 3350being 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 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.

[0216] 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 one cheek 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.

[0217] 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.

[0218] In the form of the technology shown in Fig. 3B, 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 for receiving the flow of pressurized air.

[0219] In some forms, the third arm of the T-shaped connector may be substantially perpendicular to each of the first two arms.

[0220] In some forms, the third arm of the T-shaped connector may be obliquely formed with respect to each of the first two arms.

[0221] 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.

[0222] 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.

[0223] 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.

[0224] 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.

[0225] 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.

[0226] 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. 3B, 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 ofeach 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).

[0227] 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 upper portion 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.

[0228] 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

[0229] 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 tubecomprising a tube wall having an extendable concertina structure. The patient interface 3000 shown in Fig. 3B comprises tubes 3350, the superior portions of which comprise extendable tube sections each in the form of an extendable concertina structure 3362.

[0230] 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 may allow 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.

[0231] 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.

[0232] 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.

[0233] 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 chamber3200. 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

[0234] 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 3B, 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 the patient 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.

[0235] 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 duringmovement 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

[0236] 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. The tubes 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.

[0237] 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 orconnector 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

[0238] 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).

[0239] 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. Although the textile may include rigidisers along a selected length, which may limit bending, flexing, and / or stretching of the headgear 3302.

[0240] 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 3100.4.3.4 Vent

[0241] In one form, the patient interface 3000 includes a vent 3400 constructed and arranged to allow for the washout of exhaled gases, e.g. carbon dioxide.

[0242] In certain forms the vent 3400 is configured to allow a continuous vent flow from an interior of the plenum chamber 3200 to ambient whilst the pressure within the plenum chamber is positive with respect to ambient. The vent 3400 is configured such that the vent flow rate has a magnitude sufficient to reduce rebreathing of exhaled CO2 by the patient while maintaining the therapeutic pressure in the plenum chamber in use.

[0243] One form of vent 3400 in accordance with the present technology comprises a plurality of holes, for example, about 20 to about 80 holes, or about 40 to about 60 holes, or about 45 to about 55 holes.

[0244] The vent 3400 may be located in the plenum chamber 3200. Alternatively, the vent 3400 is located in a decoupling structure, e.g., a swivel.4.3.4.1 Adjustable Vent

[0245] Figs. 3E-3H show another exemplary patient interface 3000 that has an adjustable vent arrangement. The patient interface 3000 may include a cushion module 3150 with a sealing portion 3152 and a plenum portion 3154. The sealing portion 3152 may be in the form of a pair of nasal pillows or nozzles. Alternatively, the sealing portion 3152 may be a nasal cradle or cushion with one or more openings. It is further contemplated that the sealing portion 3152 may be a full-face cushion configured to engage around the patient’s mouth and nostrils.

[0246] The patient interface 3000 may further include a frame 3205 that is more rigid than the cushion module 3150 and includes vents 3400. The frame 3205 may attach to the cushion module 3150 by way of a clip 3207. Alternatively, the frame 3205 may be directly attached to the cushion module 3150 without the clip 3207. When assembled, the frame 3205 and the plenum portion 3154 may together form a plenum chamber. The frame 3205 may also include a plenum chamber inlet port 3254. One or more flap members or membranes 3406 may be positioned to cover the openings in the vents 3400.

[0247] The flap members or membranes 3406 may be configured to flex or move to one or more positions that cover the openings in the vents 3400 to a predetermined degree. For example, the flap members or membranes 3406 may be movable to a first position in which the openings of the vent 3400 are completely covered to prevent gas washout from flowing through the vent 3400. The flap members or membranes 3406 may also be movable to a second position in which the openings in the vents 3400 are completely open and are uncovered by the flap members or membranes 3406 so that gas washout can flow freely through the vent 3400 without obstruction. In addition, the flap members or membranes 3406 may be positionable in one or more intermediate positions between the first and second positions so that the openings in the vents 3400 are partially covered to varying degrees. The flap members or membranes 3406 may be movable to each intermediate position in discrete steps so that there are a finite number of intermediate positions. Alternatively, the flap members or membranes 3406 may be movable to each intermediate position in a continuous motion so that there are an infinite number of intermediate positions.

[0248] It is contemplated that other structures may be employed (valves, etc.) to vary the amount of gas washout allowed to be discharged through the vents 3400.4.3.5 Decoupling structure(s)

[0249] In one form the patient interface 3000 includes at least one decoupling structure, for example, a swivel or a ball and socket.4.3.6 Connection port

[0250] Connection port 3600 allows for connection to the air circuit 4170.4.3.7 Forehead support

[0251] In one form, the patient interface 3000 includes a forehead support 3700.4.3.8 Anti-asphyxia valve

[0252] In one form, the patient interface 3000 includes an anti-asphyxia valve.4.3.9 Ports

[0253] 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 RPT DEVICE

[0254] 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.

[0255] 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.

[0256] The RPT device may have an external housing 4010, formed in two parts, an upper portion 4012 and a lower portion 4014. Furthermore, the external housing 4010 may include one or more panel(s) 4015. The RPT device 4000 comprises a chassis 4016 that supports one or more internal components of the RPT device 4000. The RPT device 4000 may include a handle 4018.

[0257] 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 generator4140 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.

[0258] 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.

[0259] 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 circuits 4250, 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 4202.4.4.1 RPT device mechanical & pneumatic components

[0260] An RPT device may comprise one or more of the following components in an integral unit. In an alternative form, one or more of the following components may be located as respective separate units.4.4.1.1 Air filter (s)

[0261] 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.

[0262] 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.

[0263] 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 3000.4.4.1.2 Muffler(s)

[0264] An RPT device in accordance with one form of the present technology may include a muffler 4120, or a plurality of mufflers 4120.

[0265] 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.

[0266] 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 3000i4.4.1.3 Pressure generator

[0267] 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.

[0268] The pressure generator 4140 may be under the control of the therapy device controller 4240.

[0269] 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.4.4.1.4 Transducer(s)

[0270] 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.

[0271] 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.

[0272] In one form of the present technology, one or more transducers 4270 may be located proximate to the patient interface 3000.

[0273] In one form, a signal from a transducer 4270 may be filtered, such as by low-pass, high-pass or band-pass filtering.4.4.1.4.1 Flow rate sensor

[0274] 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.

[0275] In one form, a signal generated by the flow rate sensor 4274 and representing a flow rate is received by the central controller 4230.4.4.1.4.2 Pressure sensor

[0276] 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.

[0277] In one form, a signal generated by the pressure sensor 4272 and representing a pressure is received by the central controller 4230.4.4.1.4.3 Motor speed transducer

[0278] 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.4.4.1.5 Anti-spill back valve

[0279] 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 4144.4.4.2 RPT device electrical components4.4.2.1 Power supply

[0280] A power supply 4210 may be located internal or external of the external housing 4010 of the RPT device 4000.

[0281] 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.

[0282] As illustrated in Fig. 4C-1, the power supply 4210 may provide electrical power to the input device 4220, the central controller 4230, the output device 4290, and the pressure generator 4140. The power supply 4210 may also provide electric energy to other components of the RPT device 4000 (or the humidifier 5000, as described above).4.4.2.1 Input devices

[0283] 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.

[0284] 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.4.4.1.3 Central controller

[0285] 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 Figs. 4C and 4C-1.

[0286] 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.

[0287] In one form of the present technology, the central controller 4230 is a dedicated electronic circuit.

[0288] In one form, the central controller 4230 is an application-specific integrated circuit. In another form, the central controller 4230 comprises discrete electronic components.

[0289] 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.

[0290] 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.

[0291] 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.4.4.1.4 Clock

[0292] The RPT device 4000 may include a clock 4232 that is connected to the central controller 4230.4.4.1.5 Therapy device controller

[0293] 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.

[0294] 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.4.4.1.6 Protection circuits

[0295] 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.4.4.1.7 Memory

[0296] 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.

[0297] Memory 4260 may be located on the PCBA 4202. Memory 4260 may be in the form of EEPROM, or NAND flash.

[0298] 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.

[0299] 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 4300.4.4.1.8 Data communication systems

[0300] 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 remote external device 4286. The local external communication network 4284 may be connectable to a local external device 4288.

[0301] 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.

[0302] 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.

[0303] In one form, local external communication network 4284 utilises one or more communication standards, such as Bluetooth, or a consumer infrared protocol.

[0304] 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.

[0305] The local external device 4288 may be a personal computer, mobile phone, tablet or remote control.4.4.1.9 Output devices including optional display, alarms

[0306] 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.4.4.2.9.1 Display driver

[0307] 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.4.4.2.9.2 Display

[0308] 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!4.4.3 RPT device algorithms

[0309] 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.

[0310] 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.

[0311] 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 4330.4.4.3.1 Pre-processing module

[0312] 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.

[0313] 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.

[0314] In various forms of the present technology, the pre-processing module 4310 comprises one or more of the following algorithms: interface pressure estimation 4312, vent flow rate estimation 4314, leak flow rate estimation 4316, and respiratory flow rate estimation 4318.4.4.3.1.1 Interface pressure estimation

[0315] In one form of the present technology, an 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 particular air circuit 4170 by a pressure drop characteristic AP(Q). The interface pressure estimation algorithm, 4312 then provides as an output an estimated pressure, Pm, in the patient interface 3000. The pressure, Pm, in the patient interface 3000 may be estimated as the device pressure Pd minus the air circuit pressure drop AP.4.4.3.1.2 Vent flow rate estimation

[0316] In one form of the present technology, a vent flow rate estimation algorithm 4314 receives as an input an estimated pressure, Pm, in the patient interface 3000 from the interface pressure estimation algorithm 4312 and estimates a vent flow rate of air, Qv, from a vent 3400 in a patient interface 3000. The dependence of the vent flow rate Qv on the interface pressure Pm for the particular vent 3400 in use may be modelled by a vent characteristic Qv(Pm).4.4.3.1.3 Leak flow rate estimation

[0317] In one form of the present technology, a leak flow rate estimation algorithm 4316 receives as an input a total flow rate, Qt, and a vent flow rate Qv, and provides as an output an estimate of the leak flow rate QI. In one form, the leak flow rate estimation algorithm estimates the leak flow rate QI by calculating an average of the difference between total flow rate Qt and vent flow rate Qv over a period sufficiently long to include several breathing cycles, e.g. about 10 seconds.

[0318] In one form, the leak flow rate estimation algorithm 4316 receives as an input a total flow rate Qt, a vent flow rate Qv, and an estimated pressure, Pm, in the patient interface 3000, and provides as an output a leak flow rate QI, by calculating a leak conductance, and determining a leak flow rate QI to be a function of leak conductance and pressure, Pm. Leak conductance is calculated as the quotient of low pass filtered non-vent flow rate equal to the difference between total flow rate Qt and vent flow rate Qv, and low pass filtered square root of pressure Pm, where the low pass filter time constant has a value sufficiently long to include several breathing cycles, e.g. about 10 seconds. The leak flow rate QI may be estimated as the product of leak conductance and a function of pressure, Pm.4.4.3.1.4 Respiratory flow rate estimation

[0319] In one form of the present technology, a 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.4.4.3.1 Therapy Engine Module

[0320] 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.

[0321] In one form of the present technology, a therapy parameter is a treatment pressure Pt.

[0322] 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.

[0323] 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 4329.4.4.3.2.1 Phase determination

[0324] In one form of the present technology, the RPT device 4000 does not determine phase.

[0325] 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.

[0326] 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 Qr has 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.

[0327] Another implementation of discrete phase determination provides a trivalued phase output with a value of one of inhalation, mid-inspiratory pause, and exhalation.

[0328] 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 then is 0.25 revolutions.3. If Qr is zero and falling fast, then is 0.5 revolutions.4. If Qr is large negative and steady then is 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.

[0329] 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.

[0330] 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 haselapsed 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).4.4.3.2.2 Waveform determination

[0331] 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.

[0332] 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 O of a respiratory cycle of a patient according to a waveform template 11( ).

[0333] 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.

[0334] 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.

[0335] In some forms of the present technology, the waveform determination algorithm 4322 selects a waveform template 11( ) from a library of waveform templates, dependent on a setting of the RPT device. Each waveform template 11( ) in the library may be provided as a lookup table of values II against phase values O. In other forms, the waveform determination algorithm 4322 computes a waveform template 11(0) “on the fly” using a predetermined functional form, possiblyparametrised 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.

[0336] In some forms of the present technology, suitable for discrete bi-valued phase of either inhalation ( = 0 revolutions) or exhalation ( = 0.5 revolutions), the waveform determination algorithm 4322 computes a waveform template II “on the fly” as a function of both discrete phase and time t measured since the most recent trigger instant. In one such form, the waveform determination algorithm 4322 computes the waveform template 11( , f) in two portions (inspiratory and expiratory) as follows:0 = 00 = 0.5

[0337] 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.4.4.3.2.3 Ventilation determination

[0338] 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.

[0339] 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.

[0340] 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 Qpeak over 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 ratewaveforms 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.4.4.3.2.4 Determination of Inspiratory Flow Limitation

[0341] 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.

[0342] 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.

[0343] 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 the same 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.

[0344] From the scaled flow rate, two shape factors relating to the determination of partial obstruction may be calculated.

[0345] 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.

[0346] 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.

[0347] 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.4.4.3.2.5 Determination of apneas and hypopneas

[0348] 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.

[0349] 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.

[0350] 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-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 flow rate threshold may be a relatively long-term measure of flow rate.

[0351] 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.4.4.3.2.6 Determination of snore

[0352] 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.

[0353] 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.

[0354] 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.4.4.3.2.7 Determination of airway patency

[0355] 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.

[0356] 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.

[0357] 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 one implementation, the forced oscillation is of frequency 2 Hz with amplitude about 1 cmH20.

[0358] 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 acardiogenic signal. The absence of a cardiogenic signal is taken to be an indication of a closed airway.4.4.3.2.8 Determination of target ventilation

[0359] 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.

[0360] 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.

[0361] 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.

[0362] 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%).

[0363] 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 ITy / ?.

[0364] 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 of central 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.4.4.3.2.9 Determination of therapy parameters

[0365] 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.

[0366] 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 equation

[0367] 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.

[0368] 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.

[0369] 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.4.4.3.3 Therapy Control module

[0370] 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.

[0371] In one form of the present technology, the therapy parameter is a treatment pressure Pt, and the therapy control module 4330 controls the pressuregenerator 4140 to deliver a flow of air whose interface pressure Pm at the patient interface 3000 is equal to the treatment pressure Pt.4.4.3.4 Detection of fault conditions

[0372] 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.

[0373] 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 incident4.5 AIR CIRCUIT

[0374] An air circuit 4170 in accordance with an aspect of the present technology is a conduit or a tube constructed and arranged to allow, in use, a flow of air to travel between two components such as RPT device 4000 and the patient interface 3000.

[0375] In particular, the air circuit 4170 may be in fluid connection with the outlet of the pneumatic block 4020 and the patient interface. The air circuit may be referred to as an air delivery tube. In some cases there may be separate limbs of the circuit for inhalation and exhalation. In other cases a single limb is used.

[0376] In some forms, the air circuit 4170 may comprise one or more heating elements configured to heat air in the air circuit, for example to maintain or raise the temperature of the air. The heating element may be in a form of a heated wire circuit, and may comprise one or more transducers, such as temperature sensors. In one form, the heated wire circuit may be helically wound around the axis of the air circuit 4170. The heating element may be in communication with a controller such as a central controller 4230. One example of an air circuit 4170 comprising a heated wire circuitis described in United States Patent 8,733,349, which is incorporated herewithin in its entirety by reference.4.6 HUMIDIFIER4.6.1 Humidifier overview

[0377] 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.

[0378] 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 and an 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 5240.4.7 BREATHING WAVEFORMS

[0379] Fig. 6 A 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, Ttot, 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%.4.8 RESPIRATORY THERAPY MODES

[0380] Various respiratory therapy modes may be implemented by the disclosed respiratory therapy system.4.8.1 CPAP therapy

[0381] In some implementations of respiratory pressure therapy, the central controller 4230 sets the treatment pressure Pt according to the treatment pressure equation (1) as part of the therapy parameter determination algorithm 4329. In one such implementation, the amplitude A is identically zero, so the treatment pressure Pt(which represents a target value to be achieved by the interface pressure Pm at the current instant of time) is identically equal to the base pressure o throughout the respiratory cycle. Such implementations are generally grouped under the heading of CPAP therapy. In such implementations, there is no need for the therapy engine module 4320 to determine phase or the waveform template 11( ).

[0382] In CPAP therapy, the base pressure Po may be a constant value that is hard-coded or manually entered to the RPT device 4000. Alternatively, the central controller 4230 may repeatedly compute the base pressure Po as a function of indices or measures of sleep disordered breathing returned by the respective algorithms in the therapy engine module 4320, such as one or more of flow limitation, apnea, hypopnea, patency, and snore. This alternative is sometimes referred to as APAP therapy.

[0383] Fig. 4E is a flow chart illustrating a method 4500 carried out by the central controller 4230 to continuously compute the base pressure P as part of an APAP therapy implementation of the therapy parameter determination algorithm 4329, when the pressure support^ is identically zero.

[0384] The method 4500 starts at step 4520, at which the central controller 4230 compares the measure of the presence of apnea / hypopnea with a first threshold, and determines whether the measure of the presence of apnea / hypopnea has exceeded the first threshold for a predetermined period of time, indicating an apnea / hypopnea is occurring. If so, the method 4500 proceeds to step 4540; otherwise, the method 4500 proceeds to step 4530. At step 4540, the central controller 4230 compares the measure of airway patency with a second threshold. If the measure of airway patency exceeds the second threshold, indicating the airway is patent, the detected apnea / hypopnea is deemed central, and the method 4500 proceeds to step 4560; otherwise, the apnea / hypopnea is deemed obstructive, and the method 4500 proceeds to step 4550.

[0385] At step 4530, the central controller 4230 compares the measure of flow limitation with a third threshold. If the measure of flow limitation exceeds the third threshold, indicating inspiratory flow is limited, the method 4500 proceeds to step 4550; otherwise, the method 4500 proceeds to step 4560.

[0386] At step 4550, the central controller 4230 increases the base pressure Po by a predetermined pressure increment AP, provided the resulting treatment pressure Ptwould not exceed a maximum treatment pressure Pmax. In one implementation, the predetermined pressure increment AP and maximum treatment pressure Pmax are 1 cmH20 and 25 cmH20 respectively. In other implementations, the pressure increment AP can be as low as 0.1 cmH2O and as high as 3 cmH2O, or as low as 0.5 cmH2O and as high as 2 cmH2O. In other implementations, the maximum treatment pressure Pmax can be as low as 15 cmH2O and as high as 35 cmH2O, or as low as 20 cmH2O and as high as 30 cmH2O. The method 4500 then returns to step 4520.

[0387] At step 4560, the central controller 4230 decreases the base pressure o by a decrement, provided the decreased base pressure Po would not fall below a minimum treatment pressure Pmin. The method 4500 then returns to step 4520. In one implementation, the decrement is proportional to the value of Po-Pmin, so that the decrease in o to the minimum treatment pressure Pmin in the absence of any detected events is exponential. In one implementation, the constant of proportionality is set such that the time constant rof the exponential decrease of Po is 60 minutes, and the minimum treatment pressure Pmin is 4 cmH20. In other implementations, the time constant T could be as low as 1 minute and as high as 300 minutes, or as low as 5 minutes and as high as 180 minutes. In other implementations, the minimum treatment pressure Pmin can be as low as 0 cmH20 and as high as 8 cmH20, or as low as 2 cmH20 and as high as 6 cmH20. Alternatively, the decrement in Po could be predetermined, so the decrease in Po to the minimum treatment pressure Pmin in the absence of any detected events is linear.4.8.2 Bi-level therapy

[0388] In other implementations of this form of the present technology, the value of amplitude^ in equation (1) may be positive. Such implementations are known as bi-level therapy, because in determining the treatment pressure Pt using equation (1) with positive amplitude^, the therapy parameter determination algorithm 4329 oscillates the treatment pressure Pt between two values or levels in synchrony with the spontaneous respiratory effort of the patient 1000. That is, based on the typical waveform templates 11( , f) described above, the therapy parameter determination algorithm 4329 increases the treatment pressure Pt to Po + A (known as the IPAP) at the start of, or during, or inspiration and decreases the treatment pressure Pt to the base pressure P (known as the EPAP) at the start of, or during, expiration.

[0389] In some forms of bi-level therapy, the IPAP is a treatment pressure that has the same purpose as the treatment pressure in CPAP therapy modes, and the EPAP is the IPAP minus the amplitude A, which has a “small” value (a few cmH20) sometimes referred to as the Expiratory Pressure Relief (EPR). Such forms are sometimes referred to as CPAP therapy with EPR, which is generally thought to be more comfortable than straight CPAP therapy. In CPAP therapy with EPR, either or both of the IPAP and the EPAP may be constant values that are hard-coded or manually entered to the RPT device 4000. Alternatively, the therapy parameter determination algorithm 4329 may repeatedly compute the IPAP and / or the EPAP during CPAP with EPR. In this alternative, the therapy parameter determination algorithm 4329 repeatedly computes the EPAP and / or the IPAP as a function of indices or measures of sleep disordered breathing returned by the respective algorithms in the therapy engine module 4320 in analogous fashion to the computation of the base pressure o in APAP therapy described above.

[0390] In other forms of bi-level therapy, the amplitude A is large enough that the RPT device 4000 does some or all of the work of breathing of the patient 1000. In such forms, known as pressure support ventilation therapy, the amplitude A is referred to as the pressure support, or swing. In pressure support ventilation therapy, the IPAP is the base pressure o plus the pressure support^, and the EPAP is the base pressure Po.

[0391] In some forms of pressure support ventilation therapy, known as fixed pressure support ventilation therapy, the pressure support A is fixed at a predetermined value, e.g. 10 cmH20. The predetermined pressure support value is a setting of the RPT device 4000, and may be set for example by hard-coding during configuration of the RPT device 4000 or by manual entry through the input device 4220.

[0392] In other forms of pressure support ventilation therapy, broadly known as servo-ventilation, the therapy parameter determination algorithm 4329 takes as input some currently measured or estimated parameter of the respiratory cycle (e.g. the current measure Vent of ventilation) and a target value of that respiratory parameter (e.g. a target value Vtgt of ventilation) and repeatedly adjusts the parameters of equation (1) to bring the current measure of the respiratory parameter towards the target value. In a form of servo-ventilation known as adaptive servo-ventilation (ASV), which has been used to treat CSR, the respiratory parameter is ventilation, andthe target ventilation value Vtgt is computed by the target ventilation determination algorithm 4328 from the typical recent ventilation Vtyp, as described above.

[0393] In some forms of servo-ventilation, the therapy parameter determination algorithm 4329 applies a control methodology to repeatedly compute the pressure support^ so as to bring the current measure of the respiratory parameter towards the target value. One such control methodology is Proportional-Integral (PI) control. In one implementation of PI control, suitable for ASV modes in which a target ventilation Vtgt is set to slightly less than the typical recent ventilation Vtyp, the pressure support^ is repeatedly computed as:

[0394] where G is the gain of the PI control. Larger values of gain G can result in positive feedback in the therapy engine module 4320. Smaller values of gain G may permit some residual untreated CSR or central sleep apnea. In some implementations, the gain G is fixed at a predetermined value, suchas -0.4 cmH2O / (L / min) / sec. Alternatively, the gain G may be varied between therapy sessions, starting small and increasing from session to session until a value that substantially eliminates CSR is reached. Conventional means for retrospectively analysing the parameters of a therapy session to assess the severity of CSR during the therapy session may be employed in such implementations. In yet other implementations, the gain G may vary depending on the difference between the current measure Vent of ventilation and the target ventilation Vtgt.

[0395] Other servo-ventilation control methodologies that may be applied by the therapy parameter determination algorithm 4329 include proportional (P), proportional-differential (PD), and proportional-integral-differential (PID).

[0396] The value of the pressure support A computed via equation (2) may be clipped to a range defined as [Amin, Amax], In this implementation, the pressure support A sits by default at the minimum pressure support Amin until the measure of current ventilation Vent falls below the target ventilation Vtgt, at which points starts increasing, only falling back to Amin when Vent exceeds Vtgt once again.

[0397] The pressure support limits Amin and Amax are settings of the RPT device 4000, set for example by hard-coding during configuration of the RPT device 4000 or by manual entry through the input device 4220.

[0398] In pressure support ventilation therapy modes, the EPAP is the base pressure Po. As with the base pressure Po in CPAP therapy, the EPAP may be a constant value that is prescribed or determined during titration. Such a constant EPAP may be set for example by hard-coding during configuration of the RPT device 4000 or by manual entry through the input device 4220. This alternative is sometimes referred to as fixed-EPAP pressure support ventilation therapy. Titration of the EPAP for a given patient may be performed by a clinician during a titration session with the aid of PSG, with the aim of preventing obstructive apneas, thereby maintaining an open airway for the pressure support ventilation therapy, in similar fashion to titration of the base pressure Po in constant CPAP therapy.

[0399] Alternatively, the therapy parameter determination algorithm 4329 may repeatedly compute the base pressure P during pressure support ventilation therapy. In such implementations, the therapy parameter determination algorithm 4329 repeatedly computes the EPAP as a function of indices or measures of sleep disordered breathing returned by the respective algorithms in the therapy engine module 4320, such as one or more of flow limitation, apnea, hypopnea, patency, and snore. Because the continuous computation of the EPAP resembles the manual adjustment of the EPAP by a clinician during titration of the EPAP, this process is also sometimes referred to as auto-titration of the EPAP, and the therapy mode is known as auto-titrating EPAP pressure support ventilation therapy, or auto-EPAP pressure support ventilation therapy.4.8.3 MPAP therapy

[0400] In most CPAP (Continuous Positive Airway Pressure) and BiPAP (Bilevel Positive Airway Pressure) therapies, the inspiratory pressure is set to be the same as or greater than the expiratory pressure. However, some users find it difficult to tolerate the delivery of higher-pressure gas during inhalation. For those users, CPAP and BiPAP therapies might cause the patient to feel that they are not in control of their own breathing. This is because inhalation is an active process in which the patient’s diaphragm and external intercostal muscles contract to expand the rib cage and encourage air flow into the lungs. Forcing air into the lungs during the active process of inhalation can make the patient feel uncomfortable and not in control of their own breathing, which can lead to noncompliance.

[0401] Exhalation is a passive process that does not require the patient to actively exert energy. During exhalation, the patient’s diaphragm and internal intercostal muscles relax to allow the rib cage to return to its contracted state and push the air out of the patient’s lungs. Pressure buildup in the patient’s lungs during exhalation is a natural result of the relaxation of the muscles discussed above. In addition, positive end-expiratory pressure (PEEP) may improve gas exchange within the patient’s lungs, and increased expiratory positive air pressure (EPAP) may help improve oxygenation. Accordingly, increasing the pressure of gas supplied to the patient during exhalation might feel more natural to the patient and may increase the oxygenation of the patient’s blood.

[0402] EPAP therapy is sometimes employed as an alternative to CPAP and BiPAP therapies. Rather than supply positively pressurized gas to the patient, EPAP therapy relies on the actuation of valves in a nasal insert to allow natural breathing during inhalation and to build up pressure in the patient’s airways during exhalation.

[0403] EPAP therapy nasal devices are typically in the form of nasal inserts that are sealingly inserted into the patient’s nostrils. The nasal inserts are not connected to any source of pressurized gas. Instead, the nasal inserts include valves that open during inhalation to allow ambient air into the patient’s lungs during inhalation so that there is minimal resistance during inhalation. During exhalation, valves in the nasal inserts limit the amount of gas discharged to atmosphere, thereby creating more resistance and increasing the pressure in the patient’s airways during exhalation. The pressure generated during exhalation maintains the patency of the patient’s airways.

[0404] However, EPAP therapy is susceptible to airway collapse, at least during inhalation, and is not compatible with any humidification system that could humidify the air supplied to the patient’s airways. Another type of therapy, MPAP (mixed positive airway pressure) therapy has been developed to overcome the shortcomings discussed above.

[0405] MPAP therapy provides positive air pressure to the patient’s airways during both inspiratory and expiratory phases. However, unlike the CPAP and BiPAP therapies discussed above, the pressure of gas supplied to the patient interface during inspiration is less than the pressure supplied to patient interface during exhalation.

[0406] Fig. 6B illustrates an exemplary MPAP pressure profile during one breathing cycle. During a therapy session, the central controller 4230 may execute an MPAP algorithm in which the treatment pressure Pt is set to a base pressure Po duringan inspiration phase 4355 of the breathing cycle 4360. The base pressure Po may be set to be the lowest pressure sufficient to flush CO2 out of the plenum 3200 and, the minimum pressure required to maintain the patency of the patient’s airways, or whichever of the two pressure values is higher.

[0407] During a transition period 4365 between inspiration and expiration, the treatment pressure Pt is increased from the base pressure Po to second pressure Pi that is greater than the base pressure Po so that the respiratory gas is supplied to the patient interface 3000 at the second pressure Pi during the expiration phase 4370 of the breathing cycle 4360. The transition may be gradual or abrupt. This way, unlike in EPAP therapy, the pressure in the patient’s airways never falls below a minimal pressure required to maintain the patency of the patient’s airways.

[0408] It is contemplated that MPAP therapy may be performed according to equation (1) with a positive amplitude A. As discussed above with respect to Bi-PAP therapy, the therapy parameter determination algorithm 4329 oscillates the treatment pressure Pt between two values or levels in synchrony with the spontaneous respiratory effort of the patient 1000 based on the typical waveform templates 11( , f) described above. However, unlike BiPAP therapy, the therapy parameter determination algorithm 4329 decreases the treatment pressure Pt to the base pressure Po (known as the IPAP) at the start of, or during, or inspiration and increases the treatment pressure Pt to P + A (known as the EPAP) at the start of, or during, expiration.

[0409] Fig. 6C provides a comparison between the pressure waveforms for MPAP, CPAP, BiPAP, and CPAP with EPR. For each of the respiratory therapies (except for CPAP), the pressure changes depending on whether the breathing phase is inspiratory or expiratory.

[0410] The waveform shown on the bottom of the chart is the rate of airflow in the patient’s airways during the breathing cycle. The remaining waveforms show the pressure of respiratory gas supplied to the patient’s airways during various respiratory therapies. As can be seen, the airflow rate of respiratory gas in the patient’s airways is greatest during inhalation and is lowest at the beginning of exhalation. However, the airflow rate increases during the course of the exhalation phase.

[0411] During inspiration, when the airflow rate in the patient’s lungs is greatest, the pressure of the respiratory gas supplied to the patient is also greatest for BiPAPand CPAP with EPR therapies. In CPAP with EPR (expiratory pressure relief) therapy, respiratory gas is supplied at a set pressure, and during expiration, a pressure relief valve is opened to allow pressure in the patient interface to be temporarily reduced and then equalized. For CPAP therapy, the pressure remains the same regardless of whether the breathing phase is inspiratory or expiratory.

[0412] As discussed above, the inhalation process is an active process and supplying respiratory gas at the greatest pressure (or full therapy pressure) during the phase of breathing in which the airflow rate is greatest may be uncomfortable for the patient. This may make it more difficult for the patient to fall asleep during therapy or fall back asleep during therapy. Accordingly, BiPAP and CPAP therapies might require a ramp up phase to help the patient fall asleep during therapy.

[0413] In contrast, MPAP therapy increases the pressure of the gas supplied to the patient during expiration (i.e., the phase of breathing with the lowest flowrate) and reduces the pressure provided to the patient during inspiration (i.e., the phase of breathing with the greatest flow rate). Because the airflow rate is lowest during exhalation and the maximum volume of gas is achieved at the beginning of or just prior to the expiration phase, pressure in the patient’s lungs is greater during exhalation than inhalation. Thus, the reversal of the waveform pattern in MPAP therapy (i.e., greater pressure during expiration than inspiration) mimics the natural breathing process and is more comfortable for the patient. In addition, because MPAP therapy is more comfortable, it may be easier for a patient to fall asleep under MPAP therapy, which may eliminate the need for a ramp up period in which pressure supplied to the patient interface is kept low until the patient falls asleep before being ramped up to the target therapy pressure.

[0414] Because the increased pressure is delivered during exhalation in MPAP therapy, the maximum pressure required for therapy may be lower than in other respiratory therapies. Accordingly, the size of the RPT device 4000 and the air circuit 4170 can be reduced. The lower pressure in the plenum 3200 may also allow for less headgear tension, which would further improve comfort.

[0415] In addition, due to the nature of MPAP therapy, MPAP therapy can be used to modify expiratory flow profiles. Rather than adjust the timing of the respiratory therapy to the patient’s breathing phase, the timing of the respiratory therapy can be used to modify the patient’s breathing pattern.

[0416] For example, the RPT device 4000 may provide respiratory gas at a base pressure po (inspiratory pressure) for a first predetermined amount of time, an increased therapy pressure pt for a second predetermined amount of time, and then ramp the pressure back down to the base pressure po for a third predetermined period of time . Because the pressure po is the lower pressure, the patient may adjust their breathing pattern to inhale during the first predetermined amount of time, hold their breathing during the second predetermined amount of time (when the pressure is at the highest level), and then exhale during the third predetermined amount of time as the pressure ramps down.

[0417] Fig. 6D illustrates an exemplary waveform generated by MPAP therapy that regulates the timing of the patient’s breathing. In the example illustrated in Fig.6D, the first predetermined amount of time is the shortest amount of time in the breathing pattern and is associated with inhalation. The second predetermined amount of time is longer than the first predetermined amount of time and is associated with the patient holding their breath between inspiration and exhalation. The third predetermined amount of time may be the longest of the three predetermined amounts of time (may be twice as long as the first predetermined amount of time) and may be associated with the patient’s exhalation.

[0418] In the waveform pattern of Fig. 6D, respiratory gas is provided at the base pressure po (or inspiratory pressure or IPAP) for the first predetermined amount of time. For example, the RPT device 4000 may supply the respiratory gas at the base pressure po for four seconds. After the first predetermined amount of time elapses, the pressure may be abruptly (or gradually) increased to an elevated therapy pressure pt (or expiratory pressure or EPAP), which may be held for a second predetermined amount of time. For example, the RPT device 4000 may supply the respiratory gas at the elevated therapy pressure pt for seven seconds. After the second amount of time elapses, the pressure of the respiratory gas may be ramped down for a third predetermined amount of time. For example, the RPT device 4000 may ramp down the pressure of the respiratory gas for eight seconds. The pattern may then repeat.

[0419] The timing of the different phases can set the pace of the patient’s breathing. For example, the pace of inhalation may be quick, while the pace of exhalation may be longer relative to the other two phases of breathing. The waveform shown in Fig. 6D may induce the patient to breathe according to the 4-7-8 technique, which is a technique that can reduce anxiety and help people fall asleep. In the 4-7-8technique, the patient breathes in for four seconds, holds their breath for seven seconds, and then slowly exhales for eight seconds. It is contemplated that the patient’s rate of inhalation and exhalation may follow the rate of increase and decrease in pressure of the respiratory gas supplied to the plenum 3200.

[0420] The MPAP therapy may be driven by one or more algorithms in the RPT device 4000 and the adjustment of the blower 4142 to increase or decrease the pressure. However, MPAP therapy can also be generated by manipulating the venting arrangement in the patient interface 3000.

[0421] For example, the patient interface illustrated in Figs. 3E-3H includes one or more membranes 3406 that are positioned to cover the vents 3400. The one or more membranes 3406 may be manipulated during the therapy session to open and close the openings in the vents 3400. For example, the one or more membranes 3406 may be manipulated so that the openings in the vent are completely uncovered during inspiration. Fully opened vents may allow the pressure in the patient interface 3000 to be at the base pressure po. At the end of inspiration or at the beginning of expiration, the one or more membranes 3406 may completely cover the vents 3400 so that no gas is discharged through the vents 3400. Because the vents 3400 are completely closed, the pressure in the plenum chamber 3200 is allowed to increase. At some point in the expiration process, the vents 3400 may be gradually opened to ramp down the pressure in the patient interface back to the base pressure po for the next inspiratory process. Because the pressure in the patient interface 3000 is manipulated by adjusting the gas washout through the vents 3400, the pressure of the respiratory gas supplied by the RPT device 4000 may remain constant throughout the therapy session. It is contemplated that the MPAP therapy may be performed by manipulating the pressure of gas discharged from the RPT device 4000, by manipulating the amount of gas washout discharged through the vents 3400, or a combination of RPT device 4000 and vent manipulation.

[0422] New RPT devices 4000 may be manufactured with the MPAP therapy installed in the memory 4260. However, for existing RPT devices 4000 with CPAP and / or BiPAP algorithms already installed, the RPT device 4000 may be retrofitted for MPAP therapy by uploading a new algorithm with instructions for performing MPAP therapy. The uploaded MPAP therapy algorithm may replace or be stored alongside existing therapy algorithms already stored in the memory 4260.

[0423] For example, an existing RPT device 4000 may be programmed to carry out CPAP and / or BiPAP therapies (or any other therapy where the expiratory pressure (EPAP) is the same or less than the inspiratory pressure (IPAP)). In addition, the RPT device 4000 may include programmable circuitry (e.g., a circuit board of a programmable motor) that allows the blower 4142 to be operated according to different algorithms.

[0424] An algorithm containing instructions for performing MPAP therapy may be stored in the memory of one or more remote devices 4600 and / or networks 4602. The remote device 4600 may include one or more remote external devices 4286 and / or one or more local external devices 4288. The remote network 4602 may include the remote external communications network 4282 and / or the local external communication network 4284.

[0425] To upload the MPAP therapy algorithm to the RPT device 4000, a communication link may be established between the RPT device 4000 and the one or more remote devices 4600 or networks 4610. The communication link may be a wireless link (Fig. 6E) over which electrical signals carrying instructions for the MPAP therapy algorithm are transmitted. The wireless communication may be made by way of, for example, near field (Bluetooth), radio frequency, cellular, or Wi-Fi communication. The RPT device 4000 may include a wireless receiver that is connected to the memory 4260 and / or central controller 4230 by way of internal circuitry. Accordingly, once the wireless receiver of the RPT device 4000 receives the electrical signals from the remote devices 4600 or networks 4602, the wireless receiver may transmit new electrical signals or the same electrical signals (that carry the instructions for performing the MPAP therapy algorithm) by way of the internal circuitry to the memory 4260 and / or central controller 4230.

[0426] The MPAP therapy algorithm may also be uploaded to the RPT device 4000 by way of a wired link (Fig. 6F). In this configuration, the one or more remote devices 4600 are directly connected to the RPT device 4000 by way of a wire 4620. The wired connection may be in the form of a twisted-pair, coaxial, and / or fiber-optic cable. Similar to the wireless communication discussed above, the RPT device 4000 may receive electrical signals from the one or more remote devices 4600 by way of a receiver (in this case, a receptacle for an electrical connector at an end of the wire 4620) and may transmit new or the same electrical signals (that carry the instructionsfor performing the MPAP therapy algorithm) by way of the internal circuitry to the memory 4260 and / or central controller 4230.

[0427] The remote device 4600 may also be in the form of a portable memory device 4630 such as a flash drive or other solid state memory device (Fig. 6G). In this configuration, the MPAP algorithms may be uploaded to the RPT device 4000 by inserting an interface portion 4640 of the portable memory device 4630 into an input port 4650 in the RPT device 4000. The input port 4650 may be directly connected to the central controller 4230 and / or the memory 4260 by way of the internal circuitry of the RPT device 4000. Accordingly, electronic signals carrying instructions for performing MPAP therapy may be transmitted from the remote device 4630 to the memory 4260 and / or the central controller 4230 by way of the internal circuitry.

[0428] Upon being stored in the memory 4260 or being received by the central controller 4230, the instructions for performing MPAP therapy may be stored alongside existing instructions for performing other respiratory therapy algorithms (e.g., CPAP and BiPAP therapies) so that the RPT device 4000 may be capable of performing different types of respiratory therapy including MPAP therapy.Alternatively, upon being stored in the memory 4260 or being received by the central controller 4230, the instructions for performing MPAP therapy may replace the existing instructions for performing other respiratory therapy algorithms (e.g., CPAP and BiPAP therapies) so that the RPT device 4000 is only capable of performing MPAP therapy.4.9 GLOSSARY

[0429] 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

[0430] 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.

[0431] 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.

[0432] 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.

[0433] In another example, ambient pressure may be the pressure immediately surrounding or external to the body.

[0434] In certain forms, ambient (e.g., acoustic) noise may be considered to be the background noise level in the room where a patient is located, other than for example, noise generated by an RPT device or emanating from a mask or patient interface. Ambient noise may be generated by sources outside the room.

[0435] 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.

[0436] 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.

[0437] 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’.

[0438] 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, Qc 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, Qy, is the flow rate of air leaving a vent to allow washout of exhaledgases. 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.

[0439] 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.

[0440] Humidifier'. The word humidifier will be taken to mean a humidifying apparatus constructed and arranged, or configured with a physical structure to be capable of providing a therapeutically beneficial amount of water (H2O) vapour to a flow of air to ameliorate a medical respiratory condition of a patient.

[0441] 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.

[0442] 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.

[0443] 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.

[0444] 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.

[0445] 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”.

[0446] Medical Oxygen'. Medical oxygen is defined as oxygen enriched air with an oxygen concentration of 80% or greater.

[0447] Patient'. A person, whether or not they are suffering from a respiratory condition.

[0448] Pressure: Force per unit area. Pressure may be expressed in a range of units, including cmFFO, g-f / cm2and hectopascal. 1 cmFbO 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 cmFLO.

[0449] 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.

[0450] 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.

[0451] Ventilator '. A mechanical device that provides pressure support to a patient to perform some or all of the work of breathing.

[0452] 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.

[0453] Polycarbonate', a thermoplastic polymer of Bisphenol-A Carbonate.

[0454] 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.

[0455] 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 framemay be a non-airtight load bearing structure in the mask. However, some forms of mask frame may also be air-tight.

[0456] 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.

[0457] Tie (noun)'. A structure designed to resist tension.

[0458] 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 dimensionb. 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.

[0459] Thick structures: Solids

[0460] 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.

[0461] 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.

[0462] 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.

[0463] 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.

[0464] 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

[0465] 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.

[0466] Breathing rate -. The rate of spontaneous respiration of a patient, usually measured in breaths per minute.

[0467] Duty cycle '. The ratio of inhalation time, Ti to total breath time, Ttot.

[0468] Expiratory portion of a breathing cycle: The period from the start of expiratory flow to the start of inspiratory flow.

[0469] 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.

[0470] 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).

[0471] Positive End-Expiratory Pressure (PEEP) '. The pressure above atmosphere in the lungs that exists at the end of expiration.

[0472] Peak flow rate (Qpeakf. The maximum value of flow rate during the inspiratory portion of the respiratory flow waveform.

[0473] 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.

[0474] 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.

[0475] Inhalation Time (Ti): The duration of the inspiratory portion of the respiratory flow rate waveform.

[0476] Exhalation Time (Te) The duration of the expiratory portion of the respiratory flow rate waveform.

[0477] 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.

[0478] 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.

[0479] 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).

[0480] 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

[0481] Adaptive Servo-Ventilator (ASV): A servo-ventilator that has a changeable, rather than fixed target ventilation. The changeable target ventilation maybe learned from some characteristic of the patient, for example, a respiratory characteristic of the patient.

[0482] 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.

[0483] 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.

[0484] 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.

[0485] 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.

[0486] Inspiratory positive airway pressure (IPAP): Maximum desired interface pressure which the ventilator will attempt to achieve during the inspiratory portion of the breath.

[0487] 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.

[0488] 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.

[0489] Spontaneous / Timed (S / T): A mode of a ventilator or other device that attempts to detect the initiation of a breath of a spontaneously breathing patient. If however, the device is unable to detect a breath within a predetermined period of time, the device will automatically initiate delivery of the breath.

[0490] Swing: Equivalent term to pressure support.

[0491] 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

[0492] Ala: the external outer wall or "wing" of each nostril (plural: alar)

[0493] Alar angle: An angle formed between the ala of each nostril.

[0494] Alare: The most lateral point on the nasal ala.

[0495] 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.

[0496] Auricle: The whole external visible part of the ear.

[0497] (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.

[0498] (nose) Cartilaginous framework: The cartilaginous framework of the nose comprises the septal, lateral, major and minor cartilages.

[0499] Columella: the strip of skin that separates the nares and which runs from the pronasale to the upper lip.

[0500] 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.

[0501] 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.

[0502] Glabella: Located on the soft tissue, the most prominent point in the midsagittal plane of the forehead.

[0503] 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.

[0504] Lip, lower (labrale inferius): The lip extending between the subnasale and the mouth.

[0505] Lip, upper (labrale superius): The lip extending between the mouth and the supramenton.

[0506] 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.

[0507] 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.

[0508] 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.

[0509] Naso-labial angle: The angle between the columella and the upper lip, while intersecting subnasale.

[0510] Otobasion inferior: The lowest point of attachment of the auricle to the skin of the face.

[0511] Otobasion superior: The highest point of attachment of the auricle to the skin of the face.

[0512] 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.

[0513] Philtrum: the midline groove that runs from lower border of the nasal septum to the top of the lip in the upper lip region.

[0514] Pogonion: Located on the soft tissue, the most anterior midpoint of the chin.

[0515] Ridge (nasal): The nasal ridge is the midline prominence of the nose, extending from the Sellion to the Pronasale.

[0516] 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.

[0517] Sellion: Located on the soft tissue, the most concave point overlying the area of the frontonasal suture.

[0518] Septal cartilage (nasal): The nasal septal cartilage forms part of the septum and divides the front part of the nasal cavity.

[0519] Subalare: The point at the lower margin of the alar base, where the alar base joins with the skin of the superior (upper) lip.

[0520] Subnasal point: Located on the soft tissue, the point at which the columella merges with the upper lip in the midsagittal plane.

[0521] Supramenton: The point of greatest concavity in the midline of the lower lip between labrale inferius and soft tissue pogonion

[0522] Anatomy of the skull

[0523] Frontal bone: The frontal bone includes a large vertical portion, the squama frontalis, corresponding to the region known as the forehead.

[0524] Mandible: The mandible forms the lower jaw. The mental protuberance is the bony protuberance of the jaw that forms the chin.

[0525] 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.

[0526] 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.

[0527] 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.

[0528] 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.

[0529] Orbit: The bony cavity in the skull to contain the eyeball.

[0530] Parietal bones: The parietal bones are the bones that, when joined together, form the roof and sides of the cranium.

[0531] 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.

[0532] 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

[0533] Diaphragm: A sheet of muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity, containing the heart, lungs andribs, from the abdominal cavity. As the diaphragm contracts the volume of the thoracic cavity increases and air is drawn into the lungs.

[0534] Larynx: The larynx, or voice box houses the vocal folds and connects the inferior part of the pharynx (hypopharynx) with the trachea.

[0535] 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.

[0536] 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.

[0537] 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

[0538] 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.

[0539] 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.

[0540] 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.

[0541] 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.

[0542] 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

[0543] 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.

[0544] 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.

[0545] 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.

[0546] Furthermore, “approximately”, “substantially”, “about”, or any similar term used herein means + / - 5-10% of the recited value.

[0547] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this technology belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present technology, a limited number of the exemplary methods and materials are described herein.

[0548] 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.

[0549] 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.

[0550] 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.

[0551] 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.

[0552] 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.

[0553] Although the technology herein has been described with reference to particular examples, it is to be understood that these examples are merely illustrative of the principles and applications of the technology. In some instances, the terminology and symbols may imply specific details that are not required to practice the technology. For example, although the terms "first" and "second" may be used, unless otherwise specified, they are not intended to indicate any order but may be utilised to distinguish between distinct elements. Furthermore, although process steps in the methodologies may be described or illustrated in an order, such an ordering is not required. Those skilled in the art will recognize that such ordering may bemodified and / or aspects thereof may be conducted concurrently or even synchronously.

[0554] 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

5 CLAIMS1. A respiratory therapy device configured to supply pressurized respiratory gas to a patient’s airways, the respiratory therapy device comprising:a blower configured to pressurize a flow of respiratory gas; and a controller configured to determine a current breathing phase of the patient and control the blower based on the breathing phase of the patient,wherein the controller is configured to cause the blower to discharge the respiratory gas at a base pressure during the patient’s inspiratory phase of the patient’s breathing cycle, andwherein the controller is configured to cause the blower to increase the pressure of the respiratory gas during at least the beginning of the patient’s expiratory phase of the patient’s breathing cycle.

2. The respiratory therapy device of claim 1, wherein the base pressure is a minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face.

3. The respiratory therapy device of claim 1, wherein the base pressure is a minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration.

4. The respiratory therapy device of claim 1, wherein the base pressure is the lower one ofa minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face, ora minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration.

5. The respiratory therapy device of any one of claims 1 to 4, wherein a transition from the base pressure to the increased pressure is abrupt.

6. The respiratory therapy device of any one of claims 1 to 4, wherein a transition from the base pressure to the increased pressure is gradual.

7. A respiratory therapy system comprising:a patient interface configured to sealingly engage a patient’s face; the respiratory therapy device of any one of claims 1 to 6; and an air delivery tube configured to convey the pressurized respiratory gas from the respiratory therapy device to the patient interface.

8. A respiratory therapy device configured to supply pressurized respiratory gas to a patient’s airways, the respiratory therapy device comprising:a blower configured to pressurize a flow of respiratory gas; and a controller configured to determine a current breathing phase of the patient and control the blower based on the breathing phase of the patient,wherein the controller is configured to control the blower in three stages, wherein in the first stage, the controller controls the blower to discharge the respiratory gas at a base pressure for a first predetermined amount of time, in the second stage, the controller controls the blower to discharge the respiratory gas at an increased pressure for a second predetermined amount of time, and in the third stage, the controller controls the blower to ramp down the pressure of the respiratory gas for a third predetermined amount of time.

9. The respiratory therapy device of claim 8, wherein the controller is configured to operate in the first stage during the patient’s inspiration phase.

10. The respiratory therapy device of any one of claims 8 to 9, wherein the controller is configured to operate in the second and third stages during the patient’s expiratory phase.

11. The respiratory therapy device of any one of claims 8 to 10, wherein the third predetermined period of time is greater than the first and second predetermined periods of time.

12. The respiratory therapy device of any one of claims 8 to 11, wherein the second predetermined period of time is greater than the first predetermined period of time.

13. The respiratory therapy device of any one of claims 8 to 12, wherein the third predetermined period of time is twice as long as the first predetermined period of time.

14. The respiratory therapy device of any one of claims 8 to 13, wherein the first predetermined period of time is four seconds, the second predetermined period of time is seven seconds, and the third predetermined period of time is eight seconds.

15. A respiratory therapy system comprising:a patient interface configured to sealingly engage a patient’s face; the respiratory therapy device of any one of claims 8 to 14; and an air delivery tube configured to convey the pressurized respiratory gas from the respiratory therapy device to the patient interface.

16. A patient interface configured to deliver positively pressurized respiratory gas to a patient’s airways, the patient interface comprising:a sealing surface configured to sealingly engage the patient’s face;a plenum chamber with an air inlet configured to receive the pressurized respiratory gas; anda variable vent arrangement configured to discharge gas washout from the plenum chamber,wherein the variable vent arrangement is configured to vary the amount of gas washout discharged from the plenum chamber depending on the patient’s breathing phase, andwherein the variable vent arrangement is configured to discharge a greater volume of gas washout during the patient’s inspiratory phase and discharge less or no gas washout at least during the beginning of the patient’s expiratory phase.

17. The patient interface of claim 16, wherein the variable vent arrangement comprises an array of vent openings and a membrane configured to move between a first position that completely covers the vent openings and a second position that leaves the vent openings completely unobstructed.

18. The patient interface of claim 17, wherein the membrane is configured to be positioned at intermediate positions between the first and second position.

19. The patient interface of claim 18, wherein there are a finite number of intermediate positions.

20. The patient interface of claim 18, wherein there are an infinite number of intermediate positions.

21. The patient interface of any one of claims 16 to 20, wherein the sealing surface is in the form of nasal pillows, a nasal cushion, or a full face cushion.

22. A respiratory therapy system comprising:the patient interface according to any one of claims 16 to 21; a respiratory therapy device configured to pressurize a flow of respiratory gas; andan air delivery tube configured to convey the pressurized respiratory gas from the respiratory therapy device to the patient interface.

23. A respiratory therapy system comprising:a patient interface configured to deliver pressurized respiratory gas to a patient’s airways, the patient interface comprising:a sealing surface configured to sealingly engage the patient’s face; a plenum chamber with an air inlet configured to receive the pressurized respiratory gas;a variable vent arrangement configured to discharge gas washout from the plenum chamber, the variable vent arrangement being configured to vary the amount of gas washout discharged from the plenum chamber depending on the patient’s breathing phase, and the variable vent arrangement being configured to discharge a greater volume of gas washout during the patient’s inspiratory phase and discharge less or no gas washout during the patient’s expiratory phase;a respiratory therapy device configured to pressurize a flow of respiratory gas, the respiratory therapy device comprising:a blower configured to pressurize a flow of respiratory gas; anda controller configured to determine a current breathing phase of the patient and control the blower based on the breathing phase of the patient, the controller being configured to cause the blower to discharge the respiratory gas at a base pressure during the patient’s inspiratory phase of the patient’s breathing cycle, and the controller being configured to cause the blower to increase the pressure of the respiratory gas during the patient’s expiratory phase of the patient’s breathing cycle; andan air delivery tube configured to convey the pressurized respiratory gas from the respiratory therapy device to the patient interface.

24. The respiratory therapy system of claim 23, wherein the base pressure is a minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face.

25. The respiratory therapy system of claim 23, wherein the base pressure is a minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration.

26. The respiratory therapy system of claim 23, wherein the base pressure is the lower one ofa minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face, ora minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration.

27. The respiratory therapy system of any one of claims 23 to 26, wherein a transition from the base pressure to the increased pressure is abrupt.

28. The respiratory therapy system of any one of claims 23 to 26, wherein a transition from the base pressure to the increased pressure is gradual.

29. The respiratory therapy system of any one of claims 23 to 28, wherein the variable vent arrangement comprises an array of vent openings and a membraneconfigured to move between a first position that completely covers the vent openings and a second position that leaves the vent openings completely unobstructed.

30. The respiratory therapy system of claim 29, wherein the membrane is configured to be positioned at intermediate positions between the first and second position.

31. The respiratory therapy system of claim 30, wherein there are a finite number of intermediate positions.

32. The respiratory therapy system of claim 30, wherein there are an infinite number of intermediate positions.

33. The respiratory therapy system of any one of claims 23 to 32, wherein the sealing surface is in the form of nasal pillows, a nasal cushion, or a full face cushion.

34. A respiratory therapy system comprising:a patient interface configured to deliver pressurized respiratory gas to a patient’s airways, the patient interface comprising:a sealing surface configured to sealingly engage the patient’s face; a plenum chamber with an air inlet configured to receive the pressurized respiratory gas;a variable vent arrangement configured to discharge gas washout from the plenum chamber, the variable vent arrangement being configured to vary the amount of gas washout discharged from the plenum chamber depending on the patient’s breathing phase, and the variable vent arrangement being configured to discharge a greater volume of gas washout during the patient’s inspiratory phase and discharge less or no gas washout during the patient’s expiratory phase;a respiratory therapy device configured to pressurize a flow of respiratory gas, the respiratory therapy device comprising:a blower configured to pressurize a flow of respiratory gas; and a controller configured to determine a current breathing phase of the patient and control the blower based on the breathing phase of the patient,the controller being configured to control the blower in three stages, in the first stage, the controller controls the blower to discharge the respiratory gas at a base pressure for a first predetermined amount of time, in the second stage, the controller controls the blower to discharge the respiratory gas at an increased pressure for a second predetermined amount of time, and in the third stage, the controller controls the blower to ramp down the pressure of the respiratory gas for a third predetermined amount of time; andan air delivery tube configured to convey the pressurized respiratory gas from the respiratory therapy device to the patient interface.

35. The respiratory therapy system of claim 34, wherein the controller is configured to operate in the first stage during the patient’s inspiration phase.

36. The respiratory therapy system of any one of claims 34 to 35, wherein the controller is configured to operate in the second and third stages during the patient’s expiratory phase.

37. The respiratory therapy system of any one of claims 34 to 36, wherein the third predetermined period of time is greater than the first and second predetermined periods of time.

38. The respiratory therapy system of any one of claims 34 to 37, wherein the second predetermined period of time is greater than the first predetermined period of time.

39. The respiratory therapy system of any one of claims 34 to 38, wherein the third predetermined period of time is twice as long as the first predetermined period of time.

40. The respiratory therapy system of any one of claims 34 to 39, wherein the first predetermined period of time is four seconds, the second predetermined period of time is seven seconds, and the third predetermined period of time is eight seconds.

41. The respiratory therapy system of any one of claims 34 to 40, wherein the variable vent arrangement comprises an array of vent openings and a membrane configured to move between a first position that completely covers the vent openings and a second position that leaves the vent openings completely unobstructed.

42. The respiratory therapy system of claim 41, wherein the membrane is configured to be positioned at intermediate positions between the first and second position.

43. The respiratory therapy system of claim 42, wherein there are a finite number of intermediate positions.

44. The respiratory therapy system of claim 42, wherein there are an infinite number of intermediate positions.

45. The respiratory therapy system of any one of claims 34 to 44, wherein the sealing surface is in the form of nasal pillows, a nasal cushion, or a full face cushion.

46. A method for performing a respiratory therapy that supplies pressurized respiratory gas to a patient’s airways, the method comprising:determining a current breathing phase of the patient; and pressurizing the respiratory gas based on the current breathing phase of the patient,wherein the respiratory gas is pressurized to a base pressure during the patient’s inspiratory phase of the patient’s breathing cycle, andwherein the pressure of the respiratory gas is increased during at least the beginning of the patient’ s expiratory phase.

47. The method of claim 46, wherein the base pressure is a minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face.

48. The method of claim 46, wherein the base pressure is a minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration.

49. The method of claim 46, wherein the base pressure is the lower one of: a minimum pressure sufficient to washout carbon dioxide from a patient interface mounted on the patient’s face, ora minimum pressure sufficient to maintain a patency of the patient’s airways during inspiration.

50. The method of any one of claims 46 to 49, wherein a transition from the base pressure to the increased pressure is abrupt.

51. The method of any one of claims 46 to 49, wherein a transition from the base pressure to the increased pressure is gradual.

52. A method for performing a respiratory therapy that supplies pressurized respiratory gas to a patient’s airways, the method comprising:determining a current breathing phase of the patient; andpressurizing a flow of respiratory gas based on the breathing phase of the patient,wherein the pressure of the respiratory gas is adjusted in three stages, in a first stage, the respiratory gas is pressurized to a base pressure for a first predetermined amount of time, in the second stage, the respiratory gas is pressurized to an increased pressure for a second predetermined amount of time, and in the third stage, the pressure of the respiratory gas is ramped down for a third predetermined amount of time.

53. The method of claim 52, wherein the first stage occurs during the patient’s inspiration phase.

54. The method of any one of claims 52 to 53, wherein the second and third stages occur during the patient’s expiratory phase.

55. The method of any one of claims 52 to 54, wherein the third predetermined period of time is greater than the first and second predetermined periods of time.

56. The method of any one of claims 52 to 55, wherein the second predetermined period of time is greater than the first predetermined period of time.

57. The method of any one of claims 52 to 56, wherein the third predetermined period of time is twice as long as the first predetermined period of time.

58. The method of any one of claims 52 to 57, wherein the first predetermined period of time is four seconds, the second predetermined period of time is seven seconds, and the third predetermined period of time is eight seconds.

59. A method for supplying pressurized respiratory gas to a patient’s airways, the method comprising:supplying a pressurized supply of respiratory gas to a patient interface; determining the patient’s breathing phase;adjusting an amount of gas washout discharged from the patient interface based on the patient’s breathing phase,wherein the volume of gas washout discharged during the patient’s inspiratory phase is greater than the volume of gas washout discharged during the patient’s expiratory phase.

60. A method that supplies positive pressure air to a patient, wherein during at least part of the inspiration and expiration stages of the respiratory cycle, and wherein at least during a portion of the expiration stage, the pressure of the positive pressure air is more than the pressure of the positive pressure air supplied during the inspiration stage.

61. A respiratory therapy system comprising: a device configured to supply positive pressure air to a patient during at least part of the inspiration and expiration stages of the respiratory cycle, and wherein at least during a portion of the expiration stage, the pressure of the positive pressure air is more than the pressure of the positive pressure air supplied during the inspiration stage.

62. A non-transitory computer readable storage medium storing computer executable instructions for use with a central controller of an RPT device, the computer executable instructions being configured to cause the RPT device to perform operations comprising:pressurizing respiratory gas based on the current breathing phase of a patient, wherein the respiratory gas is pressurized to a base pressure during the patient’s inspiratory phase of the patient’s breathing cycle, andwherein the pressure of the respiratory gas is increased during the patient’s expiratory phase.

63. A non-transitory computer readable storage medium storing computer executable instructions for use with a central controller of an RPT device, the computer executable instructions being configured to cause the RPT device to perform operations comprising:pressurizing a flow of respiratory gas based on the breathing phase of the patient,wherein the pressure of the respiratory gas is adjusted in three stages, in a first stage, the respiratory gas is pressurized to a base pressure for a first predetermined amount of time, in the second stage, the respiratory gas is pressurized to an increased pressure for a second predetermined amount of time, and in the third stage, the pressure of the respiratory gas is ramped down for a third predetermined amount of time.

64. A method for retrofitting an RPT device to perform a respiratory therapy according to any one of claims 46 to 60, the method comprising:creating a communication link between an external communication network or device and the RPT device;transmitting electrical signals from the external communication network or device to the RPT device through the communication link, the electrical signals including instructions for performing the respiratory therapy; andstoring the instructions in a memory of the RPT device.

65. The method of claim 64, wherein the electrical signals are transmitted to the RPT device wirelessly.

66. The method of claim 64, wherein the electrical signals are transmitted by wired connection.

67. The method of any one of claims 64 to 66, wherein the instructions included in the electrical signals replace existing instructions already stored in a memory of the RPT device when the electrical signals are transmitted to the RPT device.

68. The method of any one of claims 64 to 66, wherein the instructions included in the electrical signals are stored alongside existing instructions already stored in a memory of the RPT device when the electrical signals are transmitted to the RPT device.

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