Patent Publication Number: US-11389615-B2

Title: Respiratory pressure treatment system

Description:
1 CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/853,812, filed Apr. 21, 2020, which is a continuation of U.S. application Ser. No. 15/104,789, filed Jun. 15, 2016, now abandoned, which is the U.S. national phase of International Application No. PCT/AU2014/050426, filed Dec. 17, 2014, and claims priority to Australian Provisional Patent Application Nos. AU 2013904923, filed Dec. 17, 2013, AU 2014901998, filed May 27, 2014, AU 2014901999, filed May 27, 2014, AU 2014901997, filed May 27, 2014, and AU 2014902071, filed May 30, 2014, and U.S. Provisional Patent Application 61/987,245, filed May 1, 2014, the entire contents of each of which are incorporated herein by reference. 
    
    
     2 BACKGROUND OF THE TECHNOLOGY 
     2.1 Field of the Technology 
     The present technology relates to one or more of the detection, diagnosis, treatment, prevention and amelioration of respiratory-related disorders. In particular, the present technology relates to medical devices or apparatus, and their use. 
     2.2 Description of the Related Art 
     2.2.1 Human Respiratory System and its Disorders 
     The respiratory system of the body facilitates gas exchange. The nose and mouth form the entrance to the airways of a patient. 
     The airways include a series of branching tubes, which become narrower, shorter and more numerous as they penetrate deeper into the lung. The prime function of the lung is gas exchange, allowing oxygen to move from the air into the venous blood and carbon dioxide to move out. The trachea divides into right and left main bronchi, which further divide eventually into terminal bronchioles. The bronchi make up the conducting airways, and do not take part in gas exchange. Further divisions of the airways lead to the respiratory bronchioles, and eventually to the alveoli. The alveolated region of the lung is where the gas exchange takes place, and is referred to as the respiratory zone. See “ Respiratory Physiology ”, by John B. West, Lippincott Williams &amp; Wilkins, 9th edition published 2011. 
     A range of respiratory disorders exist. Certain disorders may be characterised by particular events, e.g. apneas, hypopneas, and hyperpneas. 
     Obstructive Sleep Apnea (OSA), a form of Sleep Disordered Breathing (SDB), is characterized 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 duration, sometimes 200 to 300 times per night. It often causes excessive daytime somnolence, and it may cause cardiovascular disease and brain damage. The syndrome is a common disorder, particularly in middle aged overweight males, although a person affected may have no awareness of the problem. See U.S. Pat. No. 4,944,310 (Sullivan). 
     Cheyne-Stokes Respiration (CSR) is another form of sleep disordered breathing. CSR is a disorder of a patient&#39;s respiratory controller in which there are rhythmic alternating periods of waxing and waning ventilation known as CSR cycles. CSR is characterised by repetitive de-oxygenation and re-oxygenation of the arterial blood. It is possible that CSR is harmful because of the repetitive hypoxia. In some patients CSR is associated with repetitive arousal from sleep, which causes severe sleep disruption, increased sympathetic activity, and increased afterload. See U.S. Pat. No. 6,532,959 (Berthon-Jones). 
     Obesity Hyperventilation Syndrome (OHS) is defined as the combination of severe obesity and awake chronic hypercapnia, in the absence of other known causes for hypoventilation. Symptoms include dyspnea, morning headache and excessive daytime sleepiness. 
     Chronic Obstructive Pulmonary Disease (COPD) encompasses any of a group of lower airway diseases that have certain characteristics in common. These include increased resistance to air movement, extended expiratory phase of respiration, and loss of the normal elasticity of the lung. Examples of COPD are emphysema and chronic bronchitis. COPD is caused by chronic tobacco smoking (primary risk factor), occupational exposures, air pollution and genetic factors. Symptoms include: dyspnea on exertion, chronic cough and sputum production. 
     Neuromuscular Disease (NMD) is a broad term that encompasses many diseases and ailments that impair the functioning of the muscles either directly via intrinsic muscle pathology, or indirectly via nerve pathology. Some NMD patients are characterised by progressive muscular impairment leading to loss of ambulation, being wheelchair-bound, swallowing difficulties, respiratory muscle weakness and, eventually, death from respiratory failure. Neuromuscular disorders can be divided into rapidly progressive and slowly progressive: (i) Rapidly progressive disorders: Characterised by muscle impairment that worsens over months and results in death within a few years (e.g. Amyotrophic lateral sclerosis (ALS) and Duchenne muscular dystrophy (DMD) in teenagers); (ii) Variable or slowly progressive disorders: Characterised by muscle impairment that worsens over years and only mildly reduces life expectancy (e.g. Limb girdle, Facioscapulohumeral and Myotonic muscular dystrophy). Symptoms of respiratory failure in NMD include: increasing generalised weakness, dysphagia, dyspnea on exertion and at rest, fatigue, sleepiness, morning headache, and difficulties with concentration and mood changes. 
     Chest wall disorders are a group of thoracic deformities that result in inefficient coupling between the respiratory muscles and the thoracic cage. The disorders are usually characterised by a restrictive defect and share the potential of long term hypercapnic respiratory failure. Scoliosis and kyphoscoliosis may cause severe respiratory failure. Symptoms of respiratory failure include: dyspnea on exertion, peripheral oedema, orthopnea, repeated chest infections, morning headaches, fatigue, poor sleep quality and loss of appetite. 
     A range of therapies have been used to treat or ameliorate such conditions. Furthermore, otherwise healthy individuals may take advantage of such therapies to prevent respiratory disorders from arising. However, these have a number of shortcomings. 
     2.2.2 Therapy 
     Nasal Continuous Positive Airway Pressure (CPAP) therapy has been used to treat Obstructive Sleep Apnea (OSA). The hypothesis is that continuous positive airway pressure acts as a pneumatic splint and may prevent upper airway occlusion by pushing the soft palate and tongue forward and away from the posterior oropharyngeal wall. Treatment of OSA by nasal 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 or aesthetically unappealing. 
     Non-invasive ventilation (NIV) provides ventilatory support to a patient through the upper airways to assist the patient in taking a full breath and assist to maintain adequate oxygen levels in the body by doing some or all of the work of breathing. The ventilatory support is provided via a patient interface. NIV has been used to treat CSR, OHS, COPD, MD and Chest Wall disorders. 
     Invasive ventilation (IV) provides ventilatory support to patients that are no longer able to effectively breathe themselves and may be provided using a tracheostomy tube. 
     2.2.3 Diagnosis and Treatment Systems 
     These therapies may be provided by a treatment system or device. Systems and devices may also be used to diagnose a condition without treating it. 
     A treatment system may comprise a Respiratory Pressure Therapy Device (RPT device), an air circuit, a humidifier, a patient interface, and data management. 
     2.2.3.1 Patient Interface 
     A patient interface may be used to interface respiratory equipment to its user, for example by providing a flow of air. The flow of air may be provided via a mask to the nose, the mouth or the nose and the mouth, a tube to the mouth or a tracheostomy tube to the trachea of the user. Depending upon the therapy to be applied, the patient interface may form a seal, e.g. with a face region of the patient, to facilitate the delivery of gas at a pressure at sufficient variance with ambient pressure to effect therapy, e.g. a positive pressure of about 10 cmH2O. 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 cmH2O. 
     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 varies considerably between individuals. Since the head includes bone, cartilage and soft tissue, different regions of the face respond differently to mechanical forces. The jaw or mandible may move relative to other bones of the skull. The whole head may move during the course of a period of respiratory therapy. 
     As a consequence of these challenges, some masks suffer from being one or more of obtrusive, aesthetically undesirable, costly, poorly fitting, difficult to use, and uncomfortable especially when worn for long periods of time or when a patient is unfamiliar with a system. For example, masks designed solely for aviators, mask 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 be undesirably uncomfortable to be worn for extended periods of time, e.g. several hours This discomfort may lead to a reduction in patient compliance with therapy. This is even more so if the mask is to be worn during sleep. 
     Nasal CPAP therapy is highly effective to treat certain respiratory disorders, provided patients comply with therapy. If a mask is uncomfortable, or difficult to use a patient may not comply with therapy. Since it is often recommended that a patient regularly wash their mask, if a mask is difficult to clean (e.g. difficult to assemble or disassemble), patients may not clean their mask and this may impact on patient compliance. 
     While a mask for other applications (e.g. aviators) may not be suitable for use in treating sleep disordered breathing, a mask designed for use in treating sleep disordered breathing may be suitable for other applications. 
     For these reasons, patient interfaces for delivery of nasal CPAP during sleep form a distinct field. 
     2.2.3.2 Respiratory Pressure Therapy (RPT) Device 
     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, including one or more of comfort, noise, ease of use, efficacy, size, weight, manufacturability, cost, and reliability. 
     An example of the special requirements of certain RPT devices is acoustic noise. 
     Table of noise output levels of prior RPT devices (one specimen only, measured using test method specified in ISO3744 in CPAP mode at 10cmH 2 O). 
     
       
         
           
               
               
               
             
               
                   
               
               
                   
                 A-weighted sound 
                 Year 
               
               
                 RPT Device name 
                 power level dB(A) 
                 (approx.) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 C-Series Tango 
                 31.9 
                 2007 
               
               
                 C-Series Tango with Humidifier 
                 33.1 
                 2007 
               
               
                 S8 Escape II 
                 30.5 
                 2005 
               
               
                 S8 Escape II with H4i Humidifier 
                 31.1 
                 2005 
               
               
                 S9 AutoSet 
                 26.5 
                 2010 
               
               
                 S9 AutoSet with H5i Humidifier 
                 28.6 
                 2010 
               
               
                   
               
            
           
         
       
     
     One known RPT device used for treating sleep disordered breathing is the S9 Sleep Therapy System, manufactured by ResMed. Another example of an RPT device is a ventilator. Ventilators such as the ResMed Stellar™ Series of Adult and Paediatric Ventilators may provide support for invasive and non-invasive non-dependent ventilation for a range of patients for treating a number of conditions such as but not limited to NMD, OHS and COPD. 
     The ResMed Elisée™ 150 ventilator and ResMed VS III™ ventilator may provide support for invasive and non-invasive dependent ventilation suitable for adult or paediatric patients for treating a number of conditions. These ventilators provide volumetric and barometric ventilation modes with a single or double limb circuit. RPT devices typically comprise a pressure generator, such as a motor-driven blower or a compressed gas reservoir, and are configured to supply a flow of air to the airway of a patient. In some cases, the flow of air may be supplied to the airway of the patient at positive pressure. The outlet of the RPT device is connected via an air circuit to a patient interface such as those described above. 
     2.2.3.3 Humidifier 
     Delivery of a flow of air without humidification may cause drying of airways. The use of a humidifier with an RPT device and the patient interface produces humidified gas that minimizes drying of the nasal mucosa and increases patient airway comfort. In addition in cooler climates, warm air applied generally to the face area in and about the patient interface is more comfortable than cold air. A range of artificial humidification devices and systems are known, however they may not fulfil the specialised requirements of a medical humidifier. 
     Medical humidifiers are used to increase humidity, temperature (or both) of the flow of air in relation to ambient air when required, typically where the patient may be asleep or resting (e.g. at a hospital). As a result, a medical humidifier is preferably small for bedside placement, and it is preferably configured to only humidify, heat or humidify and heat the flow of air delivered to the patient without humidifying, heating or humidifying and heating the patient&#39;s surroundings. Room-based systems (e.g. a sauna, an air conditioner, an evaporative cooler), for example, may also humidify air that is breathed in by the patient, however they would also humidify, heat or humidify and heat the entire room, which may cause discomfort to the occupants. Furthermore medical humidifiers may have more stringent safety constraints than industrial humidifiers 
     While a number of medical humidifiers are known, they can suffer from one or more shortcomings. Some medical humidifiers may provide inadequate humidification, some are difficult or inconvenient to use by patients. 
     3 BRIEF SUMMARY OF THE TECHNOLOGY 
     The present technology is directed towards providing medical devices used in the diagnosis, amelioration, treatment, or prevention of respiratory disorders having one or more of improved comfort, cost, efficacy, ease of use and manufacturability. 
     A first aspect of the present technology relates to an apparatus for use in treating a respiratory disorder comprising a housing, a pressure generator within the housing and configured to supply a flow of air, a device outlet fluidly coupled to the pressure generator and configured to be coupled to an air circuit to deliver the flow of air to a patient interface for treating a respiratory disorder, and a wireless data communication interface integrated with the housing, the wireless data communication interface configured to connect to another device or a network. 
     A further aspect of the present technology relates to an apparatus wherein the wireless data communication interface is configured to connect to one or more of the Internet and a cellular telephone network. 
     A further aspect of the present technology relates to an apparatus wherein the wireless data communication interface uses one or more of CDMA, GSM, LTE, Wi-Fi, Bluetooth, and a consumer infrared protocol. 
     According to a further aspect of the present technology, the wireless data communication interface comprises an antenna within the housing. 
     According to a further aspect of the present technology, the wireless data communication interface further comprises an antenna ground plane. 
     A further aspect of the present technology relates to an apparatus wherein the antenna ground plane is vertically oriented. 
     A further aspect of the present technology relates to an apparatus wherein the antenna ground plane comprises one or more notches. 
     A further aspect of the present technology relates to an apparatus wherein the notches increase an effective total length of the ground plane. 
     A further aspect of the present technology relates to an apparatus wherein the notches increase the effective total length by more than approximately 25%. 
     One aspect of the present technology relates to an apparatus for humidifying a flow of breathable gas, comprising a heater plate, a chamber in fluid communication with the flow of breathable gas and a reservoir comprising a conductive portion in thermal engagement with the heater plate, the apparatus configured so that varying a first pressure of the flow of breathable gas in the chamber varies a level of thermal engagement between the conductive portion and the heater plate. 
     In one form, the reservoir further comprises an inlet and an outlet. 
     In one form, the thermal engagement is in a first direction that is substantially normal to a surface of the conductive portion. 
     In one form, the apparatus is further configured to vary a magnitude of a force between the conductive portion and the heater plate in the first direction as the first pressure is varied. 
     In one form, the chamber is part of the reservoir. 
     In one form, the chamber further comprises a variable portion. 
     In one form, the apparatus further comprises a dock configured to receive the reservoir, and the dock comprises the heater plate. 
     In one form, the dock further comprises a cavity having a top portion and a bottom portion, the bottom portion having the heater plate located thereon, the cavity configured to retain at least a portion of the reservoir therein. 
     In one form, the variable portion is compressed to enable insertion of the reservoir into the cavity of the dock. 
     In one form, the top portion of the cavity is moveable between an open and closed configuration to facilitate insertion of the reservoir into the cavity. 
     In one form, the variable portion is configured to adjust in size as the first pressure is varied to vary the level of thermal engagement between the heater plate and the conductive portion. 
     In one form, the reservoir further includes a base and a lid, the base structured to hold a volume of liquid and including the conducting portion. 
     In one form, the base and lid are pivotably coupled together. 
     In one form, the variable portion forms a seal between the base and lid. 
     In one form, the reservoir further includes a latch to secure the base and lid together. 
     In one form, the reservoir further comprises at least one handle to facilitate coupling of the reservoir to the dock. 
     In one form, the reservoir further includes a retaining clip adapted to engage with a recess on the dock to retain the reservoir in the cavity of the dock. 
     In one form, the reservoir is structured to prevent refilling of the reservoir when the reservoir is coupled to the dock. 
     In one form, at least a portion of the reservoir is prevented from being opened when the reservoir is coupled to the dock. 
     In one form, the reservoir includes a re-filling cap. 
     In one form, the apparatus further comprises an overfill protection element configured to prevent filling the reservoir above a predetermined maximum volume of water. 
     In one form, the overfill protection element comprises at least one orifice formed in a wall of the reservoir, the at least one orifice defines an egress path of water when the predetermined maximum volume of water is exceeded. 
     In one form, the overfill protection element comprises a sloped profile in the side profile of a wall of the reservoir, the sloped profile defines an egress path of water when the predetermined maximum volume of water is exceeded. 
     One aspect of the present technology relates to a method for varying thermal contact between a heater plate and a reservoir in a humidification system for humidifying a flow of breathable gas, the method comprising varying a pressure of the flow of breathable gas in the reservoir that is in fluid communication with the flow of breathable gas to vary a force between the heater plate and the reservoir. 
     Another aspect of the present technology relates to an apparatus for humidifying a flow of breathable gas, comprising a heater plate and a reservoir comprising an inlet to receive the flow of breathable gas, an outlet and a conductive portion in thermal contact with the heater plate, and wherein the apparatus is configured so that varying a pressure of the flow of breathable gas in the reservoir varies a force between the heater plate and the conductive portion in a direction of thermal contact. 
     In one form, the apparatus further comprises a dock connectable with the reservoir. 
     In one form, the dock is configured to constrain the reservoir from opening in the direction of thermal contact. 
     Another aspect of the present technology relates to a reservoir configured to contain a volume of liquid for humidifying a pressurised flow of breathable air, comprising a base portion comprising a conductive portion, a lid portion comprising an inlet and an outlet and a seal portion wherein the base portion and the lid portion are pivotably engaged and configurable in an open configuration and a closed configuration while pivotably engaged, and the seal sealingly engages the base portion and the lid portion when the reservoir is in the closed configuration. 
     In one form, the seal portion comprises an outlet tube, and a baffle, the baffle being configured to connect to the inlet tube. 
     Another aspect of the present technology relates to an apparatus for humidifying a flow of breathable gas, comprising a heater plate and a reservoir comprising an inlet, an outlet, a variable portion and a conductive portion in thermal contact with the heater plate, wherein the apparatus is configured so that varying a height of the variable portion varies a level of thermal engagement between the conductive portion and the heater plate. 
     In one form, the apparatus is configured so that the thermal engagement is in a first direction that is substantially normal to a surface of the conductive portion. 
     Another aspect of the present technology relates to a method of varying a level of thermal engagement in a humidifier apparatus, the method comprising (i) thermally engaging a heater plate with a conductive portion of a reservoir and (ii) varying a height of a variable portion of the reservoir to vary a level of thermal engagement between the conductive portion and the heater plate. 
     A reservoir to hold a predetermined maximum volume of water, comprising a base portion including an overfill protection element, wherein the reservoir is configured to be convertible between an open configuration and a closed configuration and the overfill protection element prevents filling the reservoir above the maximum volume of water when the reservoir is in the open configuration. 
     In one form, the seal portion is configured to sealingly engage the lid portion and the base portion when the reservoir is in the closed configuration. 
     In one form, the overfill protection element is configured so that excess water above the maximum volume of water will spill out via the overfill protection element when a maximum water capacity is exceeded and the base portion is in its normal, working orientation. 
     In one form, the overfill protection element is at least one orifice that defines an egress path of water when the maximum water capacity of the base portion is exceeded when the humidifier reservoir is in an open configuration. 
     In one form, the overfill protection element is a sloped profile in the side profile of the base portion that defines an egress path of water when the maximum water capacity of the base portion is exceeded when the humidifier reservoir is in an open configuration. 
     Another aspect of the present technology relates a method of preventing overfilling in a humidifier reservoir, the method comprising (i) incorporating an overfill protection element in a base portion of the humidifier reservoir and (ii) configuring the overfill protection element so that excess water above a predetermined maximum volume of water will spill out via the overfill protection element when a maximum water capacity is exceeded and the base portion is in its normal, working orientation. 
     In one form, the overfill protection element includes at least one orifice. 
     In one form, the overfill protection element includes a sloped profile. 
     Another aspect of the present technology relates to a reservoir configured to hold a predetermined maximum volume of water, comprising a plurality of walls forming a cavity structured to hold the predetermined maximum volume of water, an inlet tube configured to deliver a supply of breathable gas into the cavity, the inlet tube having an inlet interior end and an inlet exterior end and an outlet tube configured to deliver a humidified supply of breathable gas from the cavity, the outlet tube having an outlet interior end and an outlet exterior end, wherein the inlet interior end and the outlet interior end are located within the cavity and the inlet exterior end and the outlet exterior end are located in one of the plurality of walls of the cavity, a first axis defined by the inlet interior end and the inlet exterior end and a second axis defined by the outlet interior end and the outlet exterior end, wherein when the reservoir is tilted approximately 90° to normal working orientation the first axis is on a first angle such that the inlet interior end and the inlet exterior end are positioned at different heights, such that the predetermined maximum volume of water is below at least one of the inlet interior end or the inlet exterior end to prevent spillback of water through the inlet tube. 
     In one form, the reservoir is further configured so that when the reservoir is tilted approximately 90° to normal working orientation the second axis is on a second angle such that the outlet interior end and the outlet exterior end are positioned at different heights, such that the predetermined maximum volume of water is below at least one of the outlet interior end or the outlet exterior end to prevent spillback of water through the outlet tube. 
     Of course, portions of the aspects may form sub-aspects of the present technology. Also, various ones of the sub-aspects, aspects or both may be combined in various manners and also constitute additional aspects or sub-aspects of the present technology. 
     Other features of the technology will be apparent from consideration of the information contained in the following detailed description, abstract, drawings and claims. 
    
    
     
       4 BRIEF DESCRIPTION OF THE DRAWINGS 
       The present technology is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements including: 
       4.1 Treatment Systems 
         FIG. 1 a    shows a system including a patient  1000  wearing a patient interface  3000 , in the form of a nasal pillows, receives 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 . A bed partner  1100  is also shown. 
         FIG. 1 b    shows a system including a patient  1000  wearing a patient interface  3000 , in the form of a nasal mask, receives a supply of air at positive pressure from an RPT device  4000 . Air from the RPT device is humidified in a humidifier  5000 , and passes along an air circuit  4170  to the patient  1000 . 
         FIG. 1 c    shows a system including a patient  1000  wearing a patient interface  3000 , in the form of a full-face mask, receives 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 . 
       4.2 Respiratory System and Facial Anatomy 
         FIG. 2 a    shows an overview of a human respiratory system including the nasal and oral cavities, the larynx, vocal folds, oesophagus, trachea, bronchus, lung, alveolar sacs, heart and diaphragm. 
       4.3 Patient Interface 
         FIG. 3 a    shows a patient interface in the form of a nasal mask in accordance with one form of the present technology. 
       4.4 Breathing Waveforms 
         FIG. 4  shows a model typical breath waveform of a person while sleeping. 
       4.5 RPT Device and Humidifier 
         FIG. 5 a    shows an exploded perspective view of an RPT device  4000  in accordance with one form of the present technology. 
         FIG. 5 b    shows a perspective view of an RPT device  4000  comprising an outlet muffler  4124  in accordance with one form of the present technology. 
         FIG. 5 c    shows a perspective view of an RPT device  4000  with an integrated humidifier  5000  comprising a water reservoir  5110  in accordance with one form of the present technology. 
         FIG. 5 d    shows 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. 
         FIG. 5 e    shows a schematic diagram of the electrical components of an RPT device in accordance with one aspect of the present technology. 
         FIG. 5 f    shows a schematic diagram of the algorithms implemented in a PAP device in accordance with an aspect of the present technology. In this figure, arrows with solid lines indicate an actual flow of information, for example via an electronic signal. 
         FIG. 5 g    is a flow chart illustrating a method carried out by the therapy engine of  FIG. 5 f    in accordance with one aspect of the present technology. 
         FIG. 5 h    shows a simplified representation of a humidifier connected to a blower and a patient conduit. 
         FIG. 5 i    shows a schematic of a humidifier. 
         FIG. 6 a    shows a perspective view of a side panel  4014 , showing the inlet air filter cover  4014   fc  and the inlet air filter  4112  in exploded view in accordance with one form of the present technology. 
         FIG. 6 b    shows a perspective view of a side panel  4014  including the RPT device inlet  4002  in accordance with one form of the present technology. 
         FIG. 6 c    shows a perspective view of a side panel  4014  showing the inlet air filter cover  4014   fc  in an open position in accordance with one form of the present technology. 
         FIG. 6 d    shows a perspective view of a side panel  4014 , showing the access covers  4014   ac  in exploded view in accordance with one form of the present technology. 
         FIG. 6 e    shows a perspective view of the access covers  4014   ac  in accordance with one form of the present technology. 
         FIG. 7 a    shows a side perspective view of an RPT device  4000  comprising an outlet muffler  4124  in accordance with one form of the present technology. 
         FIG. 7 b    shows a side perspective view of an RPT device  4000  showing an outlet muffler  4124  in exploded view in accordance with one form of the present technology. 
         FIG. 7 c    shows a perspective view of an outlet muffler  4124  in accordance with one form of the present technology. 
         FIG. 7 d    shows another perspective view of an outlet muffler  4124  in accordance with one form of the present technology. 
         FIG. 7 e    shows an exploded perspective view of an outlet muffler  4124  in accordance with one form of the present technology. 
         FIG. 7 f    shows another exploded perspective view of an outlet muffler  4124  in accordance with one form of the present technology. 
         FIG. 8 a    shows a perspective view of a chassis  4016  in accordance with one form of the present technology. 
         FIG. 8 b    shows a perspective view of a chassis  4016  showing an outlet tube  4006  and an intermediate tube  4008  in exploded view in accordance with one form of the present technology. 
         FIG. 8 c    shows a side perspective view of a chassis  4016  in accordance with one form of the present technology. 
         FIG. 8 d    shows a side perspective view of a chassis  4016  showing an outlet tube  4006  and an intermediate tube  4008  in exploded view in accordance with one form of the present technology. 
         FIG. 8 e    shows a rear perspective view of a chassis  4016  in accordance with one form of the present technology. 
         FIG. 8 f    shows a rear perspective view of a chassis  4016  showing an outlet tube  4006  and an intermediate tube  4008  in exploded view in accordance with one form of the present technology. 
         FIG. 8 g    shows a perspective view of the outlet tube  4006  in accordance with one form of the present technology. 
         FIG. 8 h    shows an exploded perspective view of the outlet tube  4006  in accordance with one form of the present technology. 
         FIG. 9 a    shows a front perspective view of an RPT device  4000  in accordance with one form of the present technology. 
         FIG. 10 a    shows a perspective view of a side panel  4014  including a data communication interface  4280  in accordance with one form of the present technology. 
         FIG. 10 b    shows an exploded perspective view of a side panel  4014  including a data communication interface  4280  in accordance with one form of the present technology. 
         FIG. 11 a    shows a perspective view of a pneumatic block  4020  in accordance with one form of the present technology. 
         FIG. 11 b    shows another perspective view of a pneumatic block  4020  in accordance with one form of the present technology. 
         FIG. 11 c    shows an exploded perspective view of a pneumatic block  4020  in accordance with one form of the present technology. 
         FIG. 11 d    shows another exploded perspective view of a pneumatic block  4020  in accordance with one form of the present technology. 
         FIG. 11 e    shows a perspective view of a pneumatic block  4020  in accordance with one form of the present technology, showing the first PB housing  4020   h   1  and the second PB housing  4020   h   2  in phantom. 
         FIG. 11 f    shows another perspective view of a pneumatic block  4020  in accordance with one form of the present technology, showing the first PB housing  4020   h   1  and the second PB housing  4020   h   2  in phantom. 
         FIG. 11 g    shows an elevation view of a pneumatic block  4020  in accordance with one form of the present technology, showing the cross-section taken in  FIG. 11   h.    
         FIG. 11 h    shows a cross-section view of a pneumatic block  4020  in accordance with one form of the present technology as indicated on  FIG. 11   g.    
         FIG. 11 i    shows an elevation view of a pneumatic block  4020  in accordance with one form of the present technology, showing the cross-section taken in  FIG. 11   j.    
         FIG. 11 j    shows a cross-section view of a pneumatic block  4020  in accordance with one form of the present technology as indicated on  FIG. 11   i.    
         FIG. 11 k    shows a perspective view of a blower sleeve  4020   bs  in accordance with one form of the present technology. 
         FIG. 11 l    shows another perspective view of a blower sleeve  4020   bs  in accordance with one form of the present technology. 
         FIG. 11 m    shows a yet another elevation view of a pneumatic block  4020  in accordance with one form of the present technology, showing the cross-section taken in  FIG. 11   n.    
         FIG. 11 n    shows a cross-section view of a pneumatic block  4020  in accordance with one form of the present technology as indicated on  FIG. 11   m.    
         FIG. 11I  shows a detailed cross-section view of a pneumatic block  4020  in accordance with one form of the present technology as indicated on  FIG. 11   n.    
         FIG. 12 a    shows a front perspective view of a user interface panel  4190  in accordance with one form of the present technology. 
         FIG. 12 b    shows an exploded front perspective view of a user interface panel  4190  in accordance with one form of the present technology. 
         FIG. 12 c    shows a rear perspective view of a user interface panel  4190  in accordance with one form of the present technology. 
         FIG. 12 d    shows an exploded rear perspective view of a user interface panel  4190  in accordance with one form of the present technology. 
         FIG. 13 a    shows a perspective view of an RPT device  4000  with the front panel  4012  hidden in accordance with one form of the present technology. 
         FIG. 13 b    shows another perspective view of an RPT device  4000  with the front panel  4012  hidden in accordance with one form of the present technology. 
         FIG. 14 a    shows a front perspective view of a front panel  4012  in accordance with one form of the present technology. 
         FIG. 14 b    shows a rear perspective view of a front panel  4012  in accordance with one form of the present technology. 
         FIG. 15 a    shows a first menu screen  4295   m   1  in accordance with one form of the present technology. 
         FIG. 15 b    shows another first menu screen  4295   m   1  in accordance with one form of the present technology. 
         FIG. 15 c    shows a first clinical menu screen  4295   m   2  in accordance with one form of the present technology. 
         FIG. 15 d    shows another first clinical menu screen  4295   m   2  in accordance with one form of the present technology. 
         FIG. 15 e    shows a selectable sub-menu list  4295   o   1  in accordance with one form of the present technology. 
         FIG. 15 f    shows a selectable sub-menu list  4295   o   2  in accordance with one form of the present technology. 
         FIG. 15 g    shows a report sub-menu list  4295   r   1  in accordance with one form of the present technology. 
         FIG. 15 h    shows a report sub-menu  4295   r   2  in accordance with one form of the present technology. 
         FIG. 15 i    shows a report sub-menu  4295   r   3  in accordance with one form of the present technology. 
         FIG. 15 j    shows a report sub-menu  4295   r   4  in accordance with one form of the present technology. 
         FIG. 15 k    shows a report sub-menu  4295   a   1  in accordance with one form of the present technology. 
         FIG. 15 l    shows a report sub-menu  4295   a   2  in accordance with one form of the present technology. 
         FIG. 15 m    shows a report sub-menu  4295   a   3  in accordance with one form of the present technology. 
         FIG. 15 n    shows a report sub-menu  4295   a   4  in accordance with one form of the present technology. 
         FIG. 15 o    shows a report sub-menu  4295   a   5  in accordance with one form of the present technology 
         FIG. 15 p    shows a report sub-menu  4295   a   6  in accordance with one form of the present technology. 
         FIG. 15 q    shows a report sub-menu  4295   a   7  in accordance with one form of the present technology. 
         FIG. 15 r    shows a report sub-menu  4295   a   8  in accordance with one form of the present technology. 
         FIG. 15 s    shows a selectable sub-menu  4295   s   1  in accordance with one form of the present technology. 
         FIG. 15 t    shows a selectable sub-menu  4295   s   2  in accordance with one form of the present technology. 
         FIG. 15 u    shows a selectable sub-menu  4295   s   3  in accordance with one form of the present technology. 
         FIG. 15 v    shows a report sub-menu  4295   b   1  in accordance with one form of the present technology. 
         FIG. 15 w    shows a report sub-menu  4295   b   2  in accordance with one form of the present technology. 
         FIG. 15 x    shows a report sub-menu  4295   b   3  in accordance with one form of the present technology. 
         FIG. 15 y    shows a report sub-menu  4295   b   4  in accordance with one form of the present technology. 
         FIG. 16 a    shows a rear perspective view of an RPT device  4000  in accordance with one form of the present technology, showing an air circuit  4170  engaged with the RPT device  4000 . 
         FIG. 16 b    shows a rear perspective view of an RPT device  4000  in accordance with one form of the present technology, showing an air circuit  4170  in exploded view. 
         FIG. 16 c    shows a perspective view of a water reservoir  5110  in accordance with one form of the present technology. 
         FIG. 16 d    shows another perspective view of a water reservoir  5110  in accordance with one form of the present technology. 
         FIG. 16 e    shows a perspective view of a water reservoir lid  5114  and an intermediate portion  5202  in accordance with one form of the present technology. 
         FIG. 16 f    shows a perspective view of a water reservoir base  5112  in accordance with one form of the present technology. 
         FIG. 16 g    shows a perspective view of an RPT device  4000  comprising an integrated humidifier  5000  and a water reservoir  5110  in accordance with one form of the present technology. 
         FIG. 16 h    shows a perspective view of an RPT device  4000  comprising an integrated humidifier  5000  in accordance with one form of the present technology, showing the water reservoir  5110  in exploded view. 
         FIG. 16 i    shows a perspective view of an RPT device  4000  comprising an integrated humidifier  5000  in accordance with one form of the present technology, not showing the water reservoir  5110 . 
         FIG. 16 j    shows a perspective view of a water reservoir  5110  in accordance with one form of the present technology, showing the water reservoir  5110  in a closed configuration. 
         FIG. 16 k    shows a perspective view of a water reservoir  5110  in accordance with one form of the present technology, showing the water reservoir  5110  in an open configuration. 
         FIG. 16 l    shows a perspective view of an intermediate portion  5202  in accordance with one form of the present technology. 
         FIG. 16 m    shows a perspective view of an intermediate portion  5202  in accordance with one form of the present technology. 
         FIG. 17 a    shows a perspective view of a chassis  4016  in accordance with one form of the present technology. 
         FIG. 17 b    shows a perspective view of a chassis  4016  in accordance with one form of the present technology, showing the heating element  5240  in exploded view. 
         FIG. 17 c    shows a bottom perspective view of a chassis  4016  in accordance with one form of the present technology. 
         FIG. 17 d    shows a bottom perspective view of a chassis  4016  in accordance with one form of the present technology, showing the heating element  5240  in exploded view. 
         FIG. 17 e    shows a rear perspective view of a chassis  4016  in accordance with one form of the present technology. 
         FIG. 17 f    shows a rear perspective view of a chassis  4016  in accordance with one form of the present technology, showing the heating element  5240  in exploded view. 
         FIG. 17 g    shows a perspective view of a top of a HE seal  5243  in accordance with one form of the present technology. 
         FIG. 17 h    shows a perspective view of a bottom a HE seal  5243  in accordance with one form of the present technology. 
         FIG. 17 i    shows a perspective view of a top of a HE base cover  5244  in accordance with one form of the present technology. 
         FIG. 17 j    shows a perspective view of a bottom of a HE base cover  5244  in accordance with one form of the present technology. 
         FIG. 18 a    shows a perspective view of an air circuit  4170  in accordance with one form of the present technology. 
         FIG. 18 b    shows an exploded perspective view of an air circuit  4170  in accordance with one form of the present technology. 
         FIG. 18 c    shows a side perspective view of a portion of an air circuit  4170  in accordance with one form of the present technology. 
         FIG. 18 d    shows a bottom perspective view of a portion of an air circuit  4170  in accordance with one form of the present technology. 
         FIG. 18 e    shows a top perspective view of a portion of an air circuit  4170  in accordance with one form of the present technology. 
         FIG. 18 f    shows an exploded perspective view of an air circuit  4170 , an outlet assembly  5004  and an outlet tube  4006  in accordance with one form of the present technology. 
         FIG. 18 g    shows a perspective view of an air circuit  4170 , an outlet assembly  5004  and an outlet tube  4006  in accordance with one form of the present technology. 
         FIG. 18 h    shows a perspective view of an air circuit  4170 , an outlet assembly  5004  and an outlet tube  4006  in accordance with one form of the present technology, showing the air circuit  4170  in exploded view. 
         FIG. 18 i    shows another perspective view of an air circuit  4170 , an outlet assembly  5004  and an outlet tube  4006  in accordance with one form of the present technology. 
         FIG. 18 j    shows another exploded perspective view of an air circuit  4170 , an outlet assembly  5004  and an outlet tube  4006  in accordance with one form of the present technology. 
         FIG. 18 k    shows a bottom perspective view of a portion of an air circuit  4170  and a portion of an outlet tube  4006  in accordance with one form of the present technology. 
         FIG. 18 l    shows a bottom perspective view of a portion of an air circuit  4170  in accordance with one form of the present technology. 
         FIG. 18 m    shows a perspective view of a female electrical connector  5058  in accordance with one form of the present technology. 
         FIG. 18 n    shows a side view of a female electrical connector  5058  in accordance with one form of the present technology. 
         FIG. 18 o    shows a perspective view of an AC electrical connector  4170   ec  in accordance with one form of the present technology. 
         FIG. 18 p    shows a perspective view of an outlet assembly  5004  in accordance with one form of the present technology, showing the swivelling disc  5050  at a first position. 
         FIG. 18 q    shows a perspective view of an outlet assembly  5004  in accordance with one form of the present technology, showing the swivelling disc  5050  at a second position. 
         FIG. 18 r    shows a perspective view of an outlet assembly  5004  in accordance with one form of the present technology, showing the swivelling disc  5050  at a third position. 
         FIG. 18 s    shows a perspective view of a cable housing  5080  in accordance with one form of the present technology. 
         FIG. 18 t    shows a bottom perspective view of a cable housing  5080  in accordance with one form of the present technology. 
         FIG. 18 u    shows a top perspective view of a cable housing  5080  in accordance with one form of the present technology. 
         FIG. 18 v    shows a top perspective view of a swivelling disc  5050  in accordance with one form of the present technology. 
         FIG. 18 w    shows a top perspective view of a cable housing  5080  and a cable  5070  in accordance with one form of the present technology. 
         FIG. 18 x    shows a top perspective view of a cable housing  5080 , swivelling disc  5050  and a cable  5070  in accordance with one form of the present technology. 
         FIG. 18 y    shows a bottom perspective view of a swivelling disc  5050  and a cable  5070  in accordance with one form of the present technology. 
         FIG. 18 z     1  shows a rear view of a female electrical connector according to an example of the present technology. 
         FIG. 18 z     2  shows a perspective view of a female electrical connector according to an example of the present technology. 
         FIG. 18 z     3  shows a front-on view of a female electrical connector according to an example of the present technology, indicating the cross section taken for  FIG. 18 z     4 . 
         FIG. 18 z     4  shows a side cross-sectional view of a female electrical connector according to an example of the present technology. 
         FIG. 18 z     5  shows a rear perspective view of an electrical connector receiver contact element according to an example of the present technology. 
         FIG. 18 z     6  shows a front perspective view of an electrical connector receiver contact element according to an example of the present technology. 
         FIG. 19  shows an example of the present technology, showing a PAP device  4000  and an integrated humidifier  5000 . 
         FIGS. 20-23  show various views of a humidifier reservoir  5110  in accordance with one aspect of present technology, wherein  FIGS. 20-21  show the humidifier reservoir  5110  in a ‘closed’ configuration,  FIG. 22  shows the humidifier reservoir  5110  in an ‘open’ configuration, and  FIG. 23  is an exploded view of the humidifier reservoir  5110 . 
         FIGS. 24-27  show the humidifier  5000  from various perspectives, demonstrating the engagement of the humidifier reservoir  5110  with the reservoir dock  5130  and/or engagement of the humidifier  5000  with the air circuit  4170 . 
         FIGS. 28 a -30 c    show a time-lapse chart of an exemplary flow path of gas as it enters the humidifier reservoir  5110  through the inlet  5118  and exits through the outlet  5122  after traversing through the inside of the humidifier reservoir  5110 . 
         FIGS. 31-32  show exemplary distributions of pressure/force in the humidifier reservoir  5110  in various configurations. 
         FIGS. 33-40  show varying configurations of the reservoir lid  5114 , in particular variations in configurations of the inlet tube  5124  and the outlet tube  5126  according to aspects of the present technology. 
         FIGS. 41 a , 41 b    and  42  show the humidifier reservoir  5110  and in particular they aim to show the orifice  5138 . 
         FIGS. 41 c  and 41 d    show the humidifier base  5112  and in particular they aim to show the sloped profile  5139 . 
         FIGS. 43-44  show the humidifier dock  5130  and the humidifier reservoir  5110 , and in particular show the interaction between the lid retention protrusion  5142  and the dock locking recess  5144  according to one aspect of the present technology. 
         FIG. 45  shows the humidifier reservoir  5110  according to another example of the current technology, wherein it is configured with a re-filling cap  5180  and a base, top and variable portion may be affixed together. 
         FIGS. 46-49  shows other representations of a humidifier reservoir  5110  according to an aspect of the present technology, with particular regard to the arrangement of the inlet tube  5124  and the outlet tube  5126 . 
         FIG. 50  shows a cross-sectional view of a reservoir lid  5114  and a variable portion in the form of a variable portion  5116  according to an aspect of the present technology. 
         FIG. 51  shows an example of the humidifier reservoir  5110  according to another example of the current technology, wherein it is configured with a latch  5186 . 
         FIGS. 52 a   - 53  show a portion of the humidifier reservoir  5110  according to another example of the current technology. In this configuration, the reservoir  5110  comprises a reservoir lid  5114  including an inlet tube  5124 , an intermediate portion  5202  which comprises an outlet tube  5126  and a base portion  5112  (as seen in an exploded view shown in  FIG. 53 ). 
         FIGS. 54 a -54 b    show the intermediate portion  5202  of the reservoir  5110  from various angles. In particular they aim to show the baffle  5192 , the outlet tube  5126  and the support spokes  5194 . 
         FIG. 55  shows a perspective bottom view of the intermediate portion  5202  of the reservoir  5110 . 
         FIGS. 56 a -56 b    show a cross section of the reservoir lid  5114  and the intermediate portion  5202  connected together.  FIG. 56 b    shows the cross section of the baffle  5192  in further detail, in particular the arrangement of the vertical portion of the inlet tube  5124 , the locating portion  5196  of the baffle  5192  and the deflector portion  5198  of the baffle  5192 . 
         FIG. 57  shows an upper portion of the humidifier reservoir  5110  according to another example of the current technology. In this configuration, the reservoir  5110  comprises a reservoir lid portion  5114 , a base portion (not shown), and an intermediate portion  5202  that comprises an outlet tube  5126 , an inlet tube  5124  as well as a wall portion  5206 . 
         FIGS. 58 a -58 b    show a portion of the humidifier reservoir  5110  according to another example of the current technology.  FIGS. 58 a -58 b    show the reservoir lid  5114  connected to the intermediate portion  5202 , and in particular they aim to show the inlet tube  5124 , the outlet tube  5126 , the deflector portion  5198  and the flow director  5195 . 
         FIGS. 59 a -59 b    show the intermediate portion  5202  according to another example of the current technology, and in particular they aim to show the deflector portion  5198 , the flow director  5195 , the locating portion  5196  and the seal  5204 . 
         FIG. 60  shows a portion of the humidifier reservoir  5110  according to another example of the current technology. In particular,  FIG. 60  shows a water level  5184  at which the air locks would be formed to prevent further ingress of liquid into the reservoir  5110  when the predetermined maximum volume of liquid is in the reservoir  5110 . 
         FIGS. 61 a -62 b    show various views of a humidifier reservoir  5110  in accordance with one aspect of present technology, wherein  FIGS. 61 a -62 a    show the humidifier reservoir  5110  in a ‘closed’ configuration,  FIG. 62 b    shows the humidifier reservoir  5110  in an ‘open’ configuration. 
         FIGS. 63 a -63 b    show various views of a humidifier reservoir  5110  in accordance with one aspect of present technology.  FIG. 63 a    shows a plan view of the humidifier reservoir  5110  in an ‘open configuration’, indicating a cross section to be shown in  FIG. 63 b   , and  FIG. 63 b    shows the reservoir  5110  with the cross section taken through line  63   b - 63   b  of  FIG. 63 a    visible. 
         FIGS. 64-65  show various views of a reservoir base  5114  in accordance with one aspect of present technology. 
         FIG. 66  shows an exploded of an RPT device  4000 , humidifier  5000 , and end cap  5300  in accordance with one aspect of the present technology. 
         FIG. 67  shows a side perspective view of an end cap  5300  according to one aspect of the present technology. 
         FIG. 68 a    shows an exploded bottom perspective view of a portion of a RPT device/humidifier and an airflow tube according to an example of the present technology. 
         FIG. 68 b    shows a bottom perspective view of a portion of a RPT device/humidifier and an airflow tube according to an example of the present technology. 
         FIG. 68 c    shows an exploded rear perspective view of a portion of a RPT device/humidifier and an airflow tube according to an example of the present technology. 
         FIG. 68 d    shows a rear perspective view of a portion of a RPT device/humidifier and an airflow tube according to an example of the present technology. 
         FIG. 68 e    shows a rear perspective view of a portion of a RPT device/humidifier, an airflow tube and a cable housing according to an example of the present technology. 
         FIG. 69 a    shows a side view of an airflow tube according to an example of the present technology. 
         FIG. 69 b    shows another side view of an airflow tube according to an example of the present technology. 
         FIG. 69 c    shows another side view of an airflow tube according to an example of the present technology. 
         FIG. 69 d    shows an exploded perspective view of an airflow tube according to an example of the present technology. 
         FIG. 70 a    shows a top view of an outlet assembly according to an example of the present technology. 
         FIG. 70 b    shows a cross-sectional view of the outlet assembly of  FIG. 70 a    taken through line  70   b - 70   b  according to an example of the present technology. 
         FIG. 70 c    shows a cross-sectional view of the outlet assembly of  FIG. 70 a    taken through line  70   c - 70   c  according to an example of the present technology. 
     
    
    
     5 DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY 
     Before the present technology is described in further detail, it is to be understood that the technology is not limited to the particular examples described herein, which may vary. It is also to be understood that the terminology used in this disclosure is for the purpose of describing only the particular examples discussed herein, and is not intended to be limiting. 
     5.1 Therapy 
     In one form, the present technology comprises a method for treating a respiratory disorder comprising the step of applying positive pressure to the entrance of the airways of a patient  1000 . 
     In certain embodiments of the present technology, a supply of air at positive pressure is provided to the nasal passages of the patient via one or both nares. 
     In certain embodiments of the present technology, mouth breathing is limited, restricted or prevented. 
     5.2 Treatment Systems 
     In one form, the present technology comprises an apparatus or device for treating a respiratory disorder. The apparatus or device may comprise an RPT device  4000  for supplying pressurised respiratory gas, such as air, to the patient  1000  via an air circuit  4170  to a patient interface  3000 . 
     5.3 Patient Interface  3000   
     A non-invasive patient interface  3000  in accordance with one aspect of the present technology comprises the following functional aspects: a seal-forming structure  3100 , a plenum chamber  3200 , a vent  3400 , a positioning and stabilising structure  3300  and one form of connection port  3600  for connection to air circuit  4170 . The patient interface  3000  may optionally include a forehead support structure  3700  that couples with the stabilising structure  3300 . In some forms a functional aspect may be provided by one or more physical components. In some forms, one physical component may provide one or more functional aspects. In use the seal-forming structure  3100  is arranged to surround an entrance to the airways of the patient so as to facilitate the supply of air at positive pressure to the airways. 
     5.4 RPT Device  4000   
     An exploded view of an RPT device  4000  in accordance with one aspect of the present technology is shown in  FIG. 5 a   . An RPT device  4000  may comprise mechanical and pneumatic components, electrical components and be configured to execute one or more algorithms. The RPT device may include one or more panel(s) such as a front panel  4012  and a side panel  4014 . The RPT device  4000  may also comprise an outlet muffler  4124  as shown in  FIGS. 5 a  and 5 b   . The outlet muffler  4124  may be removable and replaced with a water reservoir  5110  (see  FIG. 5 c   ). In such forms, the RPT device  4000  may be considered to include an integrated humidifier  5000 . Thus, the RPT device  4000  may be used with or without humidification depending upon whether the water reservoir  5110  or the outlet muffler  4124  respectively is attached. Preferably the RPT device  4000  comprises a chassis  4016  that supports one or more internal components of the RPT device  4000 . In one form the RPT device  4000  comprises a pressure generator  4140 , which may be housed in a pneumatic block  4020  coupled to the chassis  4016 . 
     The pneumatic path of the RPT device  4000  (e.g. shown in  FIG. 5 d   ) may comprise an inlet air filter  4112 , an inlet muffler  4122 , a pressure generator  4140  capable of supplying air at positive pressure (preferably a blower  4142 ) and an outlet muffler  4124  (or a water reservoir  5110  if humidification is required). One or more transducers  4270 , such as pressure sensors  4272  and flow sensors  4274  may be included in the pneumatic path. The pneumatic path may also include anti-spill back valve  4160  to prevent water from the humidifier  5000  spilling back to the electrical components of the RPT device  4000 . 
     The RPT device  4000  may comprise one or more electrical components which may be mounted on a single Printed Circuit Board Assembly (PCBA) such as the main PCBA  4202 . In an alternative form, the RPT device  4000  may include more than one PCBAs. 
     5.4.1 RPT Device Components 
     An RPT device may comprise one or more of the following components in an integral unit. In an alternative form, one or more of the following components may be located as respective separate units. 
     5.4.1.1 Air Filter(s)  4110   
     An RPT device in accordance with one form of the present technology may include one or more air filters  4110 . 
     In one form the pneumatic path may comprise an inlet air filter  4112  (e.g. upstream of a pressure generator  4140 ) and another air filter  4114  (e.g. downstream of the pressure generator  4140 ) such as an antibacterial filter placed within the pneumatic path at a location between an outlet of the pneumatic block  4020  and a patient interface  3000 . See  FIG. 5   d.    
     5.4.1.2 Side Panel  4014   
     In one form, the RPT device  4000  may comprise a side panel  4014  as shown in  FIGS. 6 a -6 c   . The side panel  4014  may comprise one or more RPT device inlets  4002  configured to receive a flow of air into the RPT device  4000 . As shown in  FIG. 6 a   , the RPT device inlet  4002  may comprise a plurality of apertures configured to allow a flow of air therethrough. 
     The side panel  4014  (see  FIG. 6 a   ) may be configured to house the inlet air filter  4112 , and comprise a side panel frame  4014   f  and an inlet air filter cover  4014   fc  configured to secure the inlet air filter  4112  relative to the side panel frame  4014   f . The inlet air filter cover  4014   fc  may be coupled, preferably removably coupled or pivotably coupled, (as shown in  FIGS. 6 b -6 c   ) to the side panel frame  4014   f  so as to allow replacement of the inlet air filter  4112 . The inlet air filter cover  4014   fc  may further comprise a filter cover handle (e.g. a recess)  4014   ch  for the user to access to open and close the inlet air filter cover  4014   fc , and a retaining feature (e.g. a latch, not shown) to secure the inlet air filter cover  4014   fc  in its closed configuration. 
     The side panel  4014  may comprise an air filter housing  4014   h  configured to locate the inlet air filter  4112  therein, for example as a part of the inlet air filter cover  4014   fc  as shown in  FIG. 6 c   . The air filter housing  4014   h  comprises a plurality of walls  4014   w  configured to locate the inlet air filter  4112 , for example as the inlet air filter cover  4014   fc  is pivoted relative to the side panel frame  4014   f.    
     The RPT device inlet  4002  may be configured with a plurality of apertures as shown in  FIGS. 6 a -6 c   . The plurality of aperture may allow a flow of air therethrough in a direction parallel to an inlet of the pneumatic block  4020  as described in further detail below. 
     The side panel  4014  may further comprise one or more connection ports  4014   cp  (e.g. as shown in  FIG. 6 d   ) to allow access to removable storage media and accessories such as communication devices or USB ports. Accordingly, the side panel  4014  may comprise one or more access covers  4014   ac  (e.g. as shown in  FIGS. 6 a , 6 c  and 6 d   ) for protection of the connection ports  4014   cp , from one or more of: ingress of water/dust/contaminants and accidental removal of the removable storage media or accessories. The access covers  4104   ac  may also be used for aesthetic purposes. 
     The access cover  4014   ac  may comprise one or more access cover anchoring portions  4014   an  which may be used to couple the access cover  4014   ac  to the side panel frame  4014   f  (e.g. by insertion into a slot—not shown). The cover portions  4014   co  may protect the connection ports  4014   cp , for example by including one or more complementary recesses  4014   re  to receive any protruding portions of the connection ports  4014   cp . The access cover  4014   ac  may further comprise one or more access cover hinge portions  4014   hi . In some forms, the access cover hinge portion  4014   hi  may be integrally formed with the cover portions  4014   co  and the anchor portion  4014   an  of the access cover  4014   ac  for improved manufacturability and lower cost. 
     5.4.1.3 Muffler(s)  4120   
     In one form of the present technology, an inlet muffler  4122  is located in the pneumatic path upstream of a pressure generator  4140 . See  FIG. 5   d.    
     In one form of the present technology, an outlet muffler  4124  is located in the pneumatic path between the pressure generator  4140  and a patient interface  3000 . See  FIG. 5   d.    
     The outlet muffler  4124  may be a removable component of the RPT device  4000  as shown in  FIGS. 7 a -7 b   . The RPT device  4000  may comprise a corresponding dock  4130  (described in further detail below) configured to receive the outlet muffler  4124  or a water reservoir  5110 . Such an arrangement may allow a manufacture of the RPT device  4000  and the integrated humidifier  5000  to easily convert between a first configuration, in which no humidification is provided when the outlet muffler  4124  in located in the dock  4130 , to a second configuration that enables humidification, where the water reservoir  5110  is located in the dock  4130  and vice versa. For instance, where humidification is desired, the outlet muffler  4124  may be removed using the muffler lever  41241   e  to allow the RPT device  4000  to receive a water reservoir  5110 . In one form, insertion of the water reservoir  5110  into the dock  4130  would allow humidification of the flow of air from the pneumatic block  4020  before delivery to the patient  1000  as will be described in further detail below. 
     The outlet muffler  4124  may comprise an identification element, to allow a controller, such as the central controller  4230  or the humidity controller  5250 , to detect its presence (or absence), for example in the dock  4130 . The dock  4130  may comprise a complementary detection element, to detect the presence (or absence) of the outlet muffler  4124 . In one form, detection of the presence or absence of the outlet muffler  4124  in the reservoir dock  5130  may cause the controller to perform one more functions including: switch off/on the heating element  5240 , adjust the power output of the heating element  5240 , switch off/on a heating element in the air circuit  4170 , adjust the power output of the heating element in the air circuit  4170 , adjust the pressure drop estimation between the pressure generator  4140  and the patient interface  3000 , disable/enable user interface elements relating to operation of the humidifier  5000 , or disable/enable data logging/data reporting relating to operation of the humidifier  5000 . In one form, the outlet muffler  4124  may comprise an identification element (shown in the form of a magnet  5340 ) disposed thereon, such as in an end cap magnet holder  5345 . The identification element may be used for detection of the outlet muffler  4124  by the controller via the detection element. For example the detection element may include a Hall Effect sensor (not shown) located in or near the dock  4130  such as on the PCBA  4202 . 
     One advantage of an outlet muffler  4124  comprising an identification element, may be to allow reduced power consumption or customised operation of the humidifier  5000  where an outlet muffler  4124  is used. A further advantage of having the heating element on by default and turned off by engagement of the outlet muffler  4124  is in a single step of installing the outlet muffler  4124  both the heating element  5240   is  deactivated and access to the heater plate is prevented. 
     In one form, the outlet muffler  4124  receives a flow of air from the pneumatic block  4020 , and delivers the flow of air to the RPT device outlet  4004 . Thus the outlet muffler  4124  may comprise a muffler entry  4124   in  and a muffler exit  4124   ou . The outlet muffler  4124  may also comprise additional components such as a muffler cap  4124   ca , a muffler body  4124   bo , a muffler damper  4124   da  and a muffler foam  4124   fo  shown in  FIGS. 7 e   - 7   f.    
     The outlet muffler  4124  may comprise a muffler lever  41241   e  for disengaging the outlet muffler  4124  from the rest of the RPT device  4000 , for example by releasing a latch. The muffler lever  41241   e  is configured (in  FIGS. 7 a -7 f   ) to be depressed from above to disengage the outlet muffler  4124 , for example by releasing one or more muffler clips  4124   cl  from the one or more complementary recesses  4130   re  in the dock  4130  (shown in  FIG. 7 b   , and in more detail in  FIG. 16 i   ). It would be understood that the outlet muffler  4124  could comprise one or more of any number of known means to removably couple the outlet muffler  4124  to the RPT device  4000 . The outlet muffler  4124  may further comprise one or more muffler clips  4124   cl  with the RPT device  4000 , for example comprising a muffler hinge  4124   hi . In some forms, the outlet muffler  4124  may comprise a muffler travel limiter  4124   tl  configured to prevent damage to the muffler hinge  4124   hi , which may occur for example due to plastic deformation where the muffler hinge  4124   hi  is of a ‘living hinge’ configuration. Yet further, the muffler travel limiter  4124   tl  may be configured to engage with the muffler lever  41241   e  and deform as the muffler lever  41241   e  is activated (e.g. depressed). In such an arrangement, the travel limiter  4124   tl  may provide feedback to the user upon engagement of the muffler lever  41241   e  with the muffler travel limiter  4124   td , and may provide a varying degree of resistance to indicate the extent of deformation occurred. As shown in  FIGS. 7 e -7 f   , the muffler damper  4124   da  may be integrally formed with the muffler travel limiter  4124   tl . In some forms, the muffler damper  4124  may be configured to engage the muffler cap  4124   ca  and/or the muffler body  4124   bo  by friction. 
     Similarly, the outlet muffler  4124  may be configured so that the muffler lever  41241   e  must be depressed to allow the outlet muffler  4124  to be inserted into the dock  4130 . In one form, the one or more muffler clips  4124   cl  may be configured to interfere with the dock  4130  if the outlet muffler  4124  is inserted without depression of the muffler lever  41241   e . Upon insertion of the outlet muffler  4124  into the dock  4130 , the one or more muffler clips  4124   cl  moves to engage with the dock  4130  (e.g. by upwards motion), thereby securing the outlet muffler  4124  into the dock  4130 . 
     The outlet muffler  4124  may comprise one or more acoustic features to reduce the noise output of the RPT device  4000 , such as muffler foam  4124   fo  and a muffler damper  4124   da  as shown in  FIGS. 7 e -7 f   . The muffler damper  4124   da  may be coupled with the muffler cap  4124   ca  and may be formed of a flexible material, such as silicone, to dampen noise. Furthermore, the outlet muffler  4124  may comprise a muffler expansion chamber  4124   ex  formed therein to reduce noise. In the form shown in  FIG. 7 e   , the muffler expansion chamber  4124   ex  may be a cavity formed in the muffler body  4124   bo.    
     5.4.1.4 Pressure Generator  4140   
     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 housed in a volute. The blower may be preferably capable of delivering a supply of air, for example at a rate of up to about 120 litres/minute, at a positive pressure in a range from about 4 cmH 2 O to about 20 cmH 2 O, or in other forms up to about 30 cmH 2 O. The blower may be as described in any one of the following patents or patent applications the contents of which are incorporated herein in their entirety: U.S. Pat. Nos. 7,866,944; 8,638,014; 8,636,479; and PCT patent application publication number WO 2013/020167. 
     The pressure generator  4140  may be under the control of the therapy device controller  4240 . 
     In other forms, a pressure generator  4140  may be a piston-driven pump, a pressure regulator connected to a high pressure source (e.g. compressed air reservoir), or a bellows. 
     5.4.1.5 Pneumatic Block  4020   
     In one form, a pneumatic block  4020  comprising a pressure generator  4140  (e.g. blower  4142 ) may form a part of the RPT device  4000 . The pneumatic block may for example comprise a configuration described in PCT patent application publication umber WO 2013/020167, the entire contents of which is incorporated herewithin in its entirety by reference. 
     A pneumatic block  4020  according to one aspect of the present technology is shown in  FIGS. 11 a -11 d   . The pneumatic block  4020  may comprise a PB inlet  4020   in , a PB outlet  4020   ou , and house a blower  4142 . According to one aspect of the present technology, the pneumatic block  4020  may provide a compact, enclosed pneumatic path for the air flow while minimising noise and vibration outputs due to the said air flow. Furthermore, such a pneumatic block  4020  may allow the external housing  4010  to be arranged independently thereof for added flexibility in the aesthetics of the RPT device  4000  in relation to the pneumatic block  4020 . 
     The pneumatic block  4020  may also comprise one or more of a flow plate  4020   fp , a blower sleeve  4020   bs , one or more sensor ports such as flow sensor port  4020   sp  and acoustic foam  4020   af . The pneumatic block  4020  may include an outer housing, for example including a first PB housing  4020   h   1  and a second PB housing  4020   h   2 . The PB inlet  4020   in  and the PB outlet  4020   ou  may be arranged on the first PB housing  4020   h   1  and the second PB housing  4020   h   2  respectively. 
     The flow plate  4020   fp  may divide the interior of the pneumatic block  4020  into a first chamber  4020   c   1 , a second chamber  4020   c   2  and the interior of the blower sleeve  4020   bs . In one form, the flow of air would be received into the pneumatic block  4020  through the PB inlet  4020   in , and enter the PB inlet tube  4020   it  (shown in  FIG. 11 d    and  FIG. 11 h   ). The PB inlet tube  4020   it  delivers the flow of air to the first chamber  4020   c   1 , from which the flow of air travels to the second chamber  4020   c   2 . In one form, a plurality of flow tubes  4020   ft  located on the flow plate  4020   fp  (e.g. as shown in  FIGS. 11 d -11 f   ) may deliver the flow of air from the first chamber  4020   c   1  to the second chamber  4020   c   2 . The flow plate  4020   fp  may comprise a cavity through which the PB inlet tube  4020   it  may travel to deliver the flow of air to the first chamber  4020   c   1 . The flow tubes  4020   ft  may additionally be used to determine the rate of flow as will be described in further detail below. The second chamber  4020   c   2  then delivers the flow of air to the blower  4142  through the blower inlet  4142   in  (see  FIG. 11 c   ), wherein the flow of air is pressurised and exits through the blower outlet  4142   ou  before exiting the pneumatic block  4020  through the PB outlet  4020   ou  as shown in  FIG. 11 j   . In one form, the flow plate  4020   fp  may comprise approximately 10-15 flow tubes  4020   ft , such as 11-14, such as 12 flow tubes as shown in  FIG. 11 e   . The flow tube  4020   ft  may be tapered in one form, such as shown in  FIG. 11 j   , in a converging direction from the first chamber  4020   c   1  to the second chamber  4020   c   2 . 
     The PB inlet  4020   in  may comprise a flexible portion, such as the PB inlet insert  4020   ii  as shown in  FIG. 11 h   . The flexible portion may help the PB inlet  4020   in  to be correctly aligned with the RPT device inlet  4002 , by for example resiliently conforming to allow for any axial or radial misalignment therebetween. Yet further, the flexible portion may reduce mechanical load or stress on the pneumatic block  4020  while allowing for the axial or radial misalignment, as the modulus of the flexible portion may be significantly smaller than that of the housing of the pneumatic block such as the first PB housing  4020   h   1  and the second PB housing  4020   h   2 . In one form, the flexible portion may be constructed from flexible materials such as silicone, and the housing of the pneumatic block, including the first PB housing  4020   h   1  and the second PB housing  4020   h   2 , may be constructed from a more rigid material such as polypropylene, although it will be understood that a range of other materials may be suitable for both. 
     The blower sleeve  4020   bs  (as shown in  FIGS. 11 k  and 11 l   ) may be made from a flexible, resilient material such as silicone. In one form, the blower sleeve  4020   bs  may act as a suspension member to reduce noise and vibration output from the blower  4142  which may be transmitted to the patient  1000  (or the bed partner  1100 ). The blower sleeve  4020   bs  may also comprise a chamber configured to receive the flow of air from the blower outlet  4142   ou  and deliver the flow air to the PB outlet  4020   ou  as shown in  FIG. 11 j   . In one form, the blower sleeve  4020   bs  is configured to accept the blower  4142 , and sealingly engage the flow plate  4020   fp , for example, by one or more sleeve tabs  4020   st  located on the blower sleeve  4020   bs.    
     The blower sleeve  4020   bs  may also comprise a sleeve pull tab  4020   pt  configured to assist in assembly of the blower sleeve  4020   bs  with other parts of the pneumatic block such as the second PB housing  4020   h   2 . The sleeve pull tab  4020   pt  may be configured as an elongated tab suitable for manual gripping, such that a person (or automated device) assembling the pneumatic block  4020  may hold the sleeve pull tab  4020   pt , and pull through the PB outlet rim  4020   or  (as shown in  FIG. 11 d   ) to locate the PB outlet  4020   ou  with respect to the second PB housing  4020   h   2 . One advantage of such an arrangement would be reduced assembly time, while another would be accurate location of the PB outlet  4020   ou  while achieving desired suspension characteristics of the blower sleeve  4020   bs.    
     The flow sensor ports  4020   sp  may be accessible from an exterior of the pneumatic block  4020  and fluidly couple to a flow transducer  4274  (not shown). The flow sensor ports  4020   sp  may also be fluidly coupled to the flow path, such as in the pneumatic block  4020  to allow the flow transducer  4274  to measure the rate of flow through the RPT device  4000 . In one form, the flow sensor ports  4020   sp  may be connected to the first chamber  4020   c   1  and the second chamber  4020   c   2  so that the flow sensor would measure the drop in pressure between the first chamber  4020   c   1  and the second chamber  4020   c   2 . The flow sensor ports  4020   sp  may be integrally formed with an enclosure of the pneumatic block  4020  such as the first PB housing  4020   h   1 , or alternatively may be a part of a separate component such as the PB sensor coupler  4020   sc . Some or all of the flow sensor ports  4020   sp  may be flexibly configured to assist in correctly aligning and engaging the flow transducer  4274  with the pneumatic block  4020 . 
     Introduction of any water onto the flow sensor ports  4020   sp  may adversely affect operation of the flow transducer  4274 , for example by at least partially occluding a port for sensing of air pressure. It is also known that there may be a risk of water ingress into the RPT device  4000 , for example when the RPT device  4000  is used with a humidifier  5000 , as the RPT device  4000  may be in close proximity to water, and as the humidifier  5000  may contain water therein. Accordingly, each flow sensor flow path connecting respective flow sensor ports  4020   sp  to the chambers  4020   c   1  and  4020   c   2  may comprise one or more water ingress prevention features, such as a PB water trap  4020   wt , or a PB water shield  4020   ws  (see  FIG. 110 ). According to one form, the PB water trap  4020   wt  may be a recessed portion in the flow sensor flow path configured to hold a predetermined volume of water, while allowing air flow through the flow sensor flow path. A PB water shield  4020   ws  may comprise a port of small cross section area configured to allow a flow of air therethrough, however prevent ingress of water due to the higher surface tension of water. To further discourage any water from interfering with operation of the flow sensor, the port of the PB water shield  4020   ws  may be horizontally oriented and/or be located towards a top portion of the pneumatic block  4020 . In one form, the port of the PB water shield  4020   ws  may be approximately 1 mm, for example at its smallest diameter, although it will be understood that other sizes may be also suitable to prevent ingress of water through the port. In one form the PB water shield  4020   ws  may be located such that the port is arranged to be substantially flat and/or vertical at its outermost surface, at which point its diameter may be the smallest. Furthermore, the flow sensor port  4020   sp  may be arranged perpendicularly to the respective port of the PB water shield  4020   ws  that the flow sensor port  4020   sp  is fluidly connected to. In one form, the flow sensor port  4020   sp  may be configured that any water which does make its way through the port of the PB water shield  4020   ws  (or an equivalent air path) must rotate (e.g. through 90 degrees) to travel to the flow sensor, such as by travelling upwards in the normal, working orientation of the RPT device  4000 . The PB water shield  4020   ws  may be formed integrally with the enclosure of the pneumatic block  4020  (e.g. first PB housing  4020   h   1 ), or alternatively may be formed separately, to be inserted into the enclosure (e.g. by interference fit, as shown in  FIG. 11 n   ) or connected to the enclosure (e.g. by welding, not shown). Yet further, the flow sensor flow path  4020   fp  may be configured so that the flow sensor port  4020   sp  may be located above the height of the corresponding openings of the flow sensor flow path in each chamber  4020   c   1  and  4020   c   2 . This may further prevent ingress of water into the flow sensor  4274 . 
     5.4.1.6 Chassis  4016   
     The RPT device  4000  may comprise a chassis  4016  as shown in  FIGS. 8 a -8 f   , wherein the chassis  4016  may provide a structural frame for the RPT device  4000 . The platform  4016   pl  may comprise an external wall of the RPT device  4000  in some forms as shown in  FIG. 5 a    and  FIG. 8 b   . The chassis  4016  may also locate one or more components such as the external housing  4010 , the pneumatic block  4020 , the PCBA  4202 , and the outlet muffler  4124  as seen in  FIG. 5   a.    
     In one form, the chassis  4016  may comprise a platform  4016   pl  (see  FIGS. 8 a -8 b   ) configured to support the pneumatic block  4020 . The chassis  4016  may comprise a dock  4130  configured to receive the outlet muffler  4124  (or the water reservoir  5110 ), for example into a cavity therein, to connect the outlet muffler  4124  or the water reservoir  5110  to the pneumatic path. The dock  4130  may receive a portion of the outlet muffler  4124  as shown. The dock  4130  may include a dock outlet  4132  configured to deliver a flow of air into the outlet muffler  4124  or the water reservoir  5110  when inserted, and a dock inlet  4134  to receive a flow of air from the outlet muffler  4124  or the water reservoir  5110  when inserted as shown in  FIGS. 8 c -8 d   . The chassis  4016  may also comprise an RPT device outlet  4004  as shown in  FIG. 8 e   , wherein the RPT device outlet  4004  may be removably coupled to the chassis  4016 . The dock outlet  4132  may be configured to fluidly couple with the muffler entry  4124   in  or the water reservoir inlet  5118 . The dock inlet  4134  may be configured to fluidly couple with the muffler exit  4124   ou  or the water reservoir outlet  5122 . 
     In one form, the dock inlet  4134  and the dock outlet  4132  may each comprise a bellows type face seal. The seal may be engaged to abut the complementary portion of the outlet muffler  4124  (e.g.  4124   ou  or  4124   in  as shown in  FIG. 7 e   ) or the water reservoir  5110  (e.g.  5118  or  5222  as shown in  FIG. 16 d   ) or as described in U.S. Pat. No. 8,544,465, the entire contents of which is incorporated herewithin by reference. One advantage of such a bellows type face seal may be that it allows for misalignments in axial and radial directions. As such a seal would abut the complementary portion, this configuration may be radially more tolerant to misalignment than an arrangement where, for example, one male connector is inserted into a female connector. Furthermore, the flexibility of such a seal would allow for axial misalignments to be present without adversely affecting performance of the RPT device  4000  (or the humidifier  5000 ). 
     An outlet tube  4006  may comprise the RPT device outlet  4004  and the dock inlet  4134 , as well as being removably coupled to the dock  4130 . In some forms, a separate intermediate tube  4008  may comprise the dock outlet  4132 . The intermediate tube  4008  may be configured to couple to the pneumatic block  4020  to receive a flow of air from the pneumatic block  4020  for delivery to the dock  4130 . The intermediate tube  4008  may further comprise a dock outlet pressure port  4132   pp  for measuring the air pressure at the dock outlet  4132 . 
     The outlet tube  4006  may comprise an outlet tube latch portion  40061   a  configured to engage with a complementary feature in the dock  4130 , such as the dock outlet slot  4130   sl . The outlet tube  4006  may further comprise one or more outlet tube guide portions  4006   gu , which may assist in correct insertion of the outlet tube  4006  into the dock  4130  by engagement with one or more corresponding dock guide portions  4130   gu . An outlet tube guide portion  4006   gu  may comprise a flat plate in one form as shown in  FIG. 8 g   , configured to be engaged and directed by the dock guide portions  4130   gu , which may be sloped to direct the outlet tube  4006  to its intended position, such as to engage the outlet tube latch portion  40061   a  with the dock outlet slot  4130   sl.    
     The outlet end  4006   oe  may also be formed with an ISO taper, such as a 22 mm outer diameter ISO taper, to allow connection of standard non-heated air circuit. 
     As seen in  FIGS. 8 g  and 8 h    the outlet tube  4006  may comprise a flow bend, having an internal circular or curved cross-section configured to reduce the impedance of the air flow through the outlet tube  4006 . The outlet tube  4006  may be constructed in two-parts as shown in  FIG. 8 h   , wherein a first portion  4006   a  is moulded from rigid material such as Bisphenol A (BPA) free polycarbonate/acrylonitrile butadiene styrene (PC/ABS), and the second portion  4006   b  comprising at least a part of the flow bend is overmoulded from a compliant material such as silicone. Use of a compliant material to form the second portion  4006   b  that comprises a portion of the bend may allow withdrawal of a moulding tool that comprises the internal bend from the internal cavity at the end of the moulding process by deforming the second portion  4006   b.    
     The outlet tube  4006  may also include a retaining flange  4006   fl  to assist in at least one of locating or securing the outlet tube  4006  to the RPT device  4000  or the humidifier  5000 , or a housing or chassis thereof. The retaining flange  4006   fl  may assist in correctly locating or positioning the outlet end  4006   oe  of the outlet tube  4006  within the outlet of the RPT device  4000  or humidifier  5000  as shown in  FIG. 8 e   , for example by abutting a locating flange in the RPT device  4000  and/or humidifier  5000 . It should be understood that the retaining flange  4006   fl  may allow for fixed attachment of the outlet tube  4006 . The retaining flange  4006   fl  may, alternatively, allow for removable attachment of the outlet tube  4006  so that it may be cleaned or replaced. 
     The outlet tube  4006  may include an inlet end  4006   ie  that connects to the humidifier  5000  or the RPT device  4000  as shown in  FIG. 8 b -8 f   . The inlet end  4006   ie  may comprise a pressure activated face seal or bellows seal to provide sealed pneumatic connection from an outlet of the RPT device  4000  and/or the humidifier  5000 , such as the dock outlet  4132  described above. In another example of the present technology, the outlet tube  4006  may be connected at the inlet end  4006   ie  to at least one conduit that is in turn connected to a RPT device  4000  and/or a humidifier  5000 . In any of these scenarios one function of the outlet tube  4006 , and specifically the inlet end  4006   ie , may be to receive the flow of gas from the RPT device  4000  and/or the humidifier  5000  and direct it outside of the device to the air circuit  4170  via the outlet connector  4170   oc . The outlet tube  4006  also facilitates rotation of the outlet connector  4170   oc  of the air circuit  4170  by allowing the outlet connector  4170   oc  to rotate around the outlet end  4006   oe.    
     A portion of the RPT device  4000  is shown in  FIGS. 8 g -8 h  and 18 i -18 j    with the outlet tube  4006  and/or the cable housing  5080 . The outlet tube  4006  may also incorporate a latch portion  40061   a  to connect with a complementary receiving portion (such as the dock outlet slot  4130   sl ) of the RPT device  4000  and/or the humidifier  5000  to locate and/or retain the airflow tube in a correct position within the RPT device  4000  and/or the humidifier  5000  as described above. The engagement of the latch portion  40061   a  with the dock outlet slot  4130   sl  may provide a sensory feedback, such as a click, to indicate correct connection. The latch portion  40061   a  may be further configured so that the outlet tube  4006  would be dislodged from receiving portion as it disengages therefrom. The latch portion  40061   a  may be a different colour to the complementary receiving portion or RPT device  4000  and/or the humidifier  5000  component for improved visibility. In certain circumstances, the outlet tube  4006  and/or the complementary receiving portion may be configured so that a button such as at the end of the latch portion  40061   a  may be used to release the outlet tube  4006  from the complementary receiving portion. A tool may be used to release the outlet tube  4006  from the receiving portion. 
     The outlet tube  4006  may be configured so that engagement of the latch portion  40061   a  with the complementary receiving portion also completes a pneumatic connection between the air circuit  4170  and the RPT device  4000  and/or the humidifier  5000  when the air circuit  4170  is attached to the RPT device  4000  and/or humidifier  5000 . Accordingly, it may be possible to detect the absence or incorrect connection of the outlet tube  4006  or a disengagement thereof by detection of air leak. 
     In a further optional arrangement, when the outlet connector  4170   oc  of the air circuit  4170  is connected to the RPT device  4000  and/or the humidifier  5000  the connection action may be configured to ensure the correct connection of the outlet tube  4006  with the complementary receiving portion. Incorrect connection of the outlet tube  4006  to the complementary receiving portion may prevent the outlet connector  4170   oc  from being able to connect correctly to the outlet tube  4006 , which may be indicated by the RPT device  4000  through detection of a high leak flow, for example. In a further alternative the outlet connector  4170   oc  of the air circuit  4170  may be used to facilitate insertion and/or removal of the outlet tube  4006  from the RPT device  4000  and/or the humidifier  5000 . 
     As discussed above, when the air circuit  4170  is attached to the RPT device  4000  and/or humidifier  5000 , the outlet end  4006  of the outlet tube  4006  may be coupled to the outlet connection region  5056  of the outlet connector  4170   oc.    
     The dock  4130  may comprise one or more features configured to engage a component (e.g. outlet muffler  4124 ) which is inserted therein. For example, the dock  4130  may comprise one or more flanges  4130   fl  as shown in  FIGS. 8 c -8 f   , the flanges being adapted to engage and guide the outlet muffler  4124  or the water reservoir  5110  as they are inserted into the dock  4130 . 
     In one form, the dock  4130  may comprise one or more components of a humidifier  5000 , where the humidifier  5000  is integrally constructed with the RPT device  4000 . For example, a base of the dock  4130  may comprise a heating element  5240  as will be described in greater detail below. 
     5.4.1.7 Transducer(s)  4270   
     Transducers may be internal of the RPT device, or external of the RPT device. External transducers may be located for example on or form part of the air circuit, e.g. the patient interface. External transducers may be in the form of non-contact sensors such as a Doppler radar movement sensor that transmit or transfer data to the RPT device. 
     In one form of the present technology, one or more transducers  4270  may be constructed and arranged to measure properties such as a flow rate, a pressure or a temperature at one or more points in the pneumatic path. 
     In one form of the present technology, one or more transducers  4270  may be located proximate to the patient interface  3000 . 
     In one form, a signal from a transducer  4270  may be filtered, such as by low-pass, high-pass or band-pass filtering. 
     5.4.1.7.1 Flow Transducer  4274   
     A flow transducer  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. 
     In one form, a signal representing a flow rate such as a total flow Qt from the flow transducer  4274  is received by the central controller  4230 . 
     5.4.1.7.2 Pressure Transducer  4272   
     A pressure transducer  4272  in accordance with the present technology is located in fluid communication with the pneumatic path. An example of a suitable pressure transducer is a sensor from the HONEYWELL ASDX series. An alternative suitable pressure transducer is a sensor from the NPA Series from GENERAL ELECTRIC. 
     In one form, a signal from the pressure transducer  4272  is received by the central controller  4230 . 
     5.4.1.7.3 Motor Speed Transducer  4276   
     In one form of the present technology a motor speed transducer  4276  is used to determine a rotational velocity, such as of the motor  4144  or the blower  4142 . A motor speed signal from the motor speed transducer  4276  is preferably 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. 
     5.4.1.7.4 Ambient Light Sensor  4278   
     As the RPT device  4000  is often used in a bedroom environment, for example to be used while the patient  1000  is about to go to sleep, or is asleep, it may be important to ensure that any light-emitting features of the RPT device  4000  is not excessively bright. 
     In one form of the present technology an ambient light sensor  4278  is used to determine the light level in the ambient area around the RPT device  4000 . An ambient light signal from the ambient light sensor  4278  may be provided as an input to the central controller  4230 , for example to adjust a brightness of a display or any other light-emitting features, such as a backlight for input devices  4220  or any notification lights. 
     The ambient light sensor  4278  may be connected to an aperture such as the external housing light port  40101   p  as shown in  FIG. 9 a   . In such a configuration, light level detected by the ambient light sensor  4278  would correspond to the light level at or near the aperture. In one form, the external housing light port  40101   p  may be located adjacent to the display  4294  such that the brightness of the display  4294  may be adjusted according to the detected light level. The ambient light sensor  4278  may be connected to the aperture by a light well (also referred to as a light pipe) to assist in accurately determining the light level at the aperture. 
     The display  4294  may be configured to operate at one of a plurality of predetermined brightness settings. The brightness setting may be chosen according to a signal output of the ambient light sensor  4278 . For instance, the display  4294  may be configured to operate at a lower brightness setting if the light measured by the ambient light sensor  4278  is at or below a threshold (e.g. 10, 15 or 20 lux), and the display  4294  may be configured to operate at a higher brightness setting where the light measured by the ambient light sensor  4278  is above the threshold (e.g. 10, 15 or 20 lux). Thus, in such an arrangement a lower the level of the ambient light may result in a lower brightness setting. 
     5.4.1.8 Anti-Spill Back Valve  4160   
     In one form of the present technology, an anti-spill back valve is located between the humidifier  5000  and the pneumatic block  4020 . The anti-spill back valve is constructed and arranged to reduce the risk that water will flow upstream from the humidifier  5000 , for example to the motor  4144 . 
     5.4.1.9 Air Circuit  4170   
     An air circuit  4170  in accordance with an aspect of the present technology is a conduit or a tube constructed and arranged in use to allow a flow of air to travel between two components such as the pneumatic block  4020  and the patient interface  3000 . 
     In particular, the air circuit  4170  may be in fluid connection with the outlet of the pneumatic block 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. 
     As shown in  FIG. 18 a   , the air circuit  4170  may include an AC tube portion  4170   tp  and an AC outlet connector  4170   oc  at one end of the tube portion  4170   tp  to connect the air circuit to the RPT device  4000  or the humidifier  5000 . In one form, the AC outlet connector  4170   oc  may comprise an AC pre-block  4170   pb , an AC overmould  4170   om  and an AC electrical connector  4170   ec . The electrical connector  4070   ec  may be oriented parallel to a centre axis of the outlet connection region  5056  and extend downward from an underside of the outlet connector  4170   oc  and out from an opening in the AC overmould  4170   om  for protection, such as from water ingress. 
     The AC tube portion  4170   tp  may also include a helical coil  4170   co  to provide support for the AC tube portion  4170   tp . The air circuit  4170  may also incorporate a heating element to prevent rainout (condensation of water vapour, for example, within the AC tube portion  4170   tp  or the patient interface  3000 ), which may be provided within the AC helical coil  4170   co . When a heating element is provided in the AC helical coil  4170   co  electrical power or signalling or both may be necessary if, for example, the heating element is an electrical resistance heater. In some instances, an electrical connection may be required between the patient interface  3000  and the RPT device  4000  or the humidifier  5000  for electrical power or communication therebetween. 
     The air circuit  4170  may require both pneumatic and electrical connections to be formed to the humidifier  5000  (or the RPT device  4000 ), as well as a mechanical connection. These connections may be formed through the AC outlet connector  4170   oc  to allow the pressurized gas to flow to the patient interface  3000 , to provide electrical power and signalling to the heating element in the AC helical coil  4170   co  and to locate and secure the air circuit  4170  relative to the humidifier  5000  (or the RPT device  4000 ). These connections may be formed simultaneously or in series such that one of the mechanical, pneumatic or electrical connections is completed before others. The air circuit  4170  may comprise a patient interface connector  4107  to couple to a patient interface  3000  at the opposite end of the tube portion  4170   tp . In some forms, the patient interface connector  4107  may be different to the AC outlet connector  4170   oc  as shown in  FIG. 18   a.    
       FIGS. 18 b -18 e    depict air circuits or portions thereof according to examples of the present technology.  FIGS. 18 f -18 j    also depict exemplary air circuits that are connected to an outlet assembly  5004 . As can be seen in  FIGS. 18 a -18 b   , an AC tube portion  4170   tp  having an AC helical coil  4170   co  may be connected to an AC outlet connector  4170   oc . The AC helical coil  4170   co , as discussed above, may include a heating element and it may also function as a support structure for the AC tube portion  4170   tp . An electrical connection may be formed by inserting the AC outlet connector  4170   oc  on the outlet assembly  5004  (to be discussed in greater detail below) so that an AC electrical connector  4170   ec  comes into electrical contact with electrical components of the outlet assembly. 
     5.4.1.9.1 Formation of Pneumatic and Electrical Connections 
     The air circuit  4170  may require both pneumatic and electrical connections to be formed to the humidifier  5000  (or the RPT device  4000 ), as well as a mechanical connection. These connections may be formed through the outlet connector  4170   oc  to allow the pressurized gas to flow to the patient interface  3000 , to provide electrical power and signalling to the heating element in the helical coil  4170   co  and to locate and secure the air circuit  4170  relative to the humidifier  5000  (or the RPT device  4000 ). These connections may be formed simultaneously or in series such that one of the mechanical, pneumatic or electrical connections is completed before others. The air circuit  4170  may comprise on another end a patient interface connector  4107  to couple to a patient interface  3000 . 
     The AC outlet connector  4170   oc  may comprise a recess  4170   re  configured to couple to an electrical connector receiver  5052  of a swivelling disc  5050  (see  FIGS. 18 i -18 j    and further discussion below) to aid in releasably securing the AC outlet connector  4170   oc  to the humidifier  5000 , for example at the outlet assembly  5004 . The recess  4170   re  may also provide a visual aid to the patient to locate the outlet connector  4170   oc  in relation to the outlet assembly  5004  by being shaped to correspond to the electrical connector receiver  5052  (see  FIG. 18 j   ). The electrical connector receiver  5052  may house a female electrical connector  5058  such as that shown in  FIGS. 18 m -18 n   . The AC outlet connector  4170   oc  may also include an actuator  4172  that controls a retention feature  4174 . When the AC outlet connector  4170   oc  is inserted onto the outlet assembly  5004 , the retention feature  4174  may engage with a corresponding notch  5054  of the swivelling disc  5050  (see  FIG. 18 i -18 j   ). The actuator  4172  in conjunction with the notch  5054  may produce an audible sound or provide tactile feedback or both at the actuator  4172  upon engagement. The actuator  4172  or the retention feature  4174  may be produced with higher wear characteristics than the swivelling disc  5050  to allow wear to occur on the air circuit  4170 , which may be a consumable component. This may be achieved by use of a material with lower hardness to form the retention feature  4174  compared to the material from which the swivelling disc  5050  is formed. The retention feature  4174  and notch  5054  may engage by a snap-fit and the actuator  4172  may be depressible to bring in the retention feature to release it from the notch  5054 . In some cases, the retention feature  4174  and the notch  5054  may be configured so that when they are not completely engaged, they may be forced into place at commencement of therapy by the therapy pressure, for example by being configured so that the therapy pressure acting on the tab  4176  urges the retention feature  4174  towards the notch  5054 . As shown in  FIGS. 18 c -18 e   , the actuator  4172  and the retention feature  4174  may both be located on an AC tab  4176  such that pushing the actuator inward also causes the retention feature to be moved inward, thereby freeing it from the notch  5054 . In one form, the actuator  4172  may be located further from a pivot of the tab  4176  than the retention feature  4174 , which would impart a mechanical advantage to the user and increase the travel required to depress the actuator  4172  to improve the resolution of movement of the retention feature  4174  to the user. This arrangement may further improve the feedback provided to the user during engagement/disengagement of the outlet connector  4170   oc . An outlet connection region  5056  (as shown in  FIG. 18 a   ) may be shaped to correspond with the shape of the swivelling disc  5050 , as shown in  FIG. 18 f -18 j   , for example. 
     As shown in  FIG. 18 d   , a travel stop  4178  located at the inner ends of the ribs  4177  may be used in some examples of this technology in order to limit the travel, or level of squeezing, of the actuator  4172  during insertion and removal to prevent plastic deformation of the surrounding portions, to prevent tear of the AC outlet connector  4170   oc  in a periphery of the AC tab  4176  or both. The travel stops  4178  extend from the inner ends of the ribs  4177  and are aligned with the inner surface of the AC outlet connector  4170   oc  in the location of the actuator  4172 . When the actuator is squeezed or pushed inwards the inner surface of the AC outlet connector  4170   oc  is correspondingly squeezed or pushed inwards until it contacts the travel stop  4178 . The travel stop prevents further squeezing or pushing of the actuator. 
     In a further example of the technology, the notch may be replaced with a radial slot that is capable of retaining the outlet connector via the retention feature(s) but allowing rotation thereof. In such an example the swivelling disc may be fixed relative to the outlet housing or it may be eliminated completely such that the radial slot is located on the housing. Furthermore, it should be understood that such examples would retain the need for a movable electrical connector within the outlet assembly such that the electrical connection may be maintained while the outlet connector rotates. 
       FIGS. 18 k  and 18 l    show detailed bottom views of examples of the AC outlet connector  4170   oc  and specifically the outlet connection region  5056 .  FIG. 18 k    shows the AC outlet connector  4170   oc  connected at the outlet connection region  5056  to an outlet end  4006   oe  of an outlet tube  4006 . (shown in  FIG. 19   xx  and discussed further below). The outlet tube  4006  may be formed as a multiple patient multiple user (MPMU) tube that is one or more of removable, replaceable and cleanable. It should be noted that for the sake of clarity the outlet end  4006   oe  is shown in this view and reference should be made to  FIGS. 18 f -18 j    for further depiction. The outlet tube  4006  may function as a removable intermediate pneumatic coupling between the AC outlet connector  4170   oc  of the air circuit  4170  and the air outlet of RPT device  4000  or the humidifier  5000 . 
     5.4.1.9.2 Internal Ribs of the Outlet Connector  4170   oc    
       FIG. 18 k    shows a plurality of ribs  4177  disposed around the inner periphery of the outlet connection region  5056  of the AC outlet connector  4170   oc . In the illustrated example four ribs  4177  are shown but a different number of ribs such as two, three, five or more ribs may be utilised. The ribs  4177  may function to support and position the AC outlet connector  4170   oc  relative to the outlet end  4006   oe  of the outlet tube  4006 . The ribs  4177  may function to guide the AC outlet connector  4170   oc  during insertion to couple to the outlet end  4006   oe  of the outlet tube  4006  in the outlet assembly  5004  to form the pneumatic connection. This guidance may also assist in aligning the outlet connection region  5056  to facilitate the electrical connection between the AC electrical connector  4170   ec  and the electrical connector receiver  5052  on the swivelling disc  5050  of the outlet assembly  5004 . In this arrangement, although the insertion or connection of the air circuit AC outlet connector  4170   oc  to the RPT device outlet assembly  5004  may be achieved in one movement by the user, the pneumatic connection is formed first and the electrical connection is formed second. The AC outlet connector  4170   oc , the outlet assembly  5004  and the outlet tube  4006  may be configured such that outlet tube  4006  engages the seal  4170   se  of the AC outlet connector  4170   oc  prior to the electrical connector receiver  5052  forming an electrical connection with the AC electrical connector  4170   ec . Accordingly, during removal or disconnection, the electrical connection is the first to be disconnected and the pneumatic connection is disconnected second. This may be advantageous to ensure that a pneumatic seal is maintained from the RPT device  4000  or the humidifier  5000  to the air circuit  4170  and, more specifically, between the AC outlet connector  4170   oc  and the outlet tube  4006 . Furthermore, this may provide improved safety, for example, if supplemental oxygen is added to the flow of air delivered by the humidifier  5000 , as this arrangement may prevent oxygen from being exposed during connection or disconnection of the electrical connections.  FIG. 18 l    shows a similar view to  FIG. 18 k   , however, the outlet end  4006   oe  of the outlet tube  4006  is not shown to provide a clearer depiction of an example of the ribs  4177 . Both of these views also show the profile of the recess  4170   re.    
     In some cases, a non-heated air circuit  4170  may be used that does not incorporate a heating element. Accordingly, the diameter of the central opening  5092  in the swivelling disc  5050  may be sufficiently large to accept such a non-heated air circuit  4170 . Accordingly, in one example of the current technology, the external diameter of the airflow tube may be approximately 22 mm to allow connection to a standard 22 mm external diameter non-heated air circuit, and the external diameter of the AC outlet connector  4170   oc  may be approximately 36 mm. However, it is recognised that other external diameter sizes may be utilised. 
     Internal ribs  4177  may be used to reduce any radial gaps between the interior of the outlet connection region  5056  and the outlet tube  4006 . Still further, the ribs  4177  and the outlet tube  4006  may be configured so that the gaps therebetween are relatively smaller than the gap between the exterior of the outlet connection region  5056  and the swivelling disc  5050 . This may allow more of the wear from rotation to occur on the outlet tube  4006  in comparison to the swivelling disc  5050 , which may be advantageous as the outlet tube  4006  may be more readily replaced than the swivelling disc  5050 . 
     Another advantage of the ribs  4177  may be to allow a greater portion of any mechanical load that may result from tilting or non-axial movement to be transferred from the AC outlet connector  4170   oc  to the outlet tube  4006 . This may be advantageous in that this may help wear occur on the consumable components such as the air circuit  4170  and/or the outlet tube  4006  than the non-consumable components of the humidifier  5000 , such as the swivelling disc  5050 . Yet another advantage of the ribs  4177  may be to maintain or restrict the deformation of the base seal  4170   se  (as shown in  FIG. 18 a   ) during engagement of the AC outlet connector  4170   oc  with the outlet assembly  5004  by limiting the maximum axial deformation that the base seal  4170   se  can undergo towards the interior of the AC outlet connector  4170   oc.    
     5.4.1.9.3 Electrical Connection 
     The AC electrical connector  4170   ec  may include one or more lead-in features, such as chamfers, or curved radii on its edges on the leading surface in the direction of insertion such as shown in  FIG. 18 o   . This may assist insertion of the AC electrical connector  4170   ec  into the electrical connector receiver  5052  to provide a surface wipe connection and prevents damage to the conductors on the AC electrical connector  4170   ec . The thickness of the electrical leads  41701   e  on the AC electrical connector  4170   ec  may be approximately between 0.2 mm to 1.2 mm, for example 0.4 mm, 0.6 mm, 0.8 mm or 1 mm. The thickness may vary according to a number of parameters such as, the design life of the AC electrical connector  4170   ec , material chosen for the electrical leads  41701   e  and the material chosen for the receiver contact elements  5058   ce . One suitable example of material for the electrical leads  41701   e  may be high temper phosphor bronze, that is nickel plated and then gold plated. In some circumstances, an increased amount of conductive material and/or high conductivity plating (such as gold and/or platinum) may be used on the electrical leads  41701   e . This may have the advantage of improving wear characteristics and/or dissipating heat from the electrical connector  4170   ec . The electrical leads  41701   e  may have exposed conductive surfaces on the lower end of the electrical connector  4170   ec  to ensure full insertion is required to make the electrical connection. 
     Another feature provided by the connection of the AC electrical connector  4170   ec  to the electrical connector receiver  5052  on the swivelling disc  5050  may be that when assembled together, the electrical connector receiver  5052  is covered by the AC outlet connector  4170   oc  as shown in  FIG. 18 i    and  FIG. 18 j   .  FIG. 18 j    shows an exploded view wherein the AC outlet connector  4170   oc  is shown above the swivelling disc  5050 , and  FIG. 18 i    shows the AC outlet connector  4170   oc  in engagement with the swivelling disc  5050 . When the outlet connector  4170   oc  is inserted onto the swivelling disc  5050 , as shown in  FIGS. 18 g  and 18 i   , the region of the outlet connector that surrounds the AC electrical connector  4170   ec  may cover over the opening in the electrical connector receiver  5052  to prevent debris and contaminants (such as liquids) from entering into the electrical connector receiver. 
     As mentioned above, the electrical connector  4170   ec  and the electrical connector receiver  5052  are configured so that the electrical connection between them is to be made after the AC outlet connector  4170   oc  is mechanically engaged with the swivelling disc  5050 . This reduces the proportion of any deformation or load from misalignment between the AC outlet connector  4170   oc  and the swivelling disc  5050  that is supported by the AC electrical connector  4170   ec  and the electrical connector receiver  5052 . In one example, such an arrangement may be achieved by configuring the AC outlet connector  4170   oc  into the swivelling disc  5050  so that during insertion of the AC outlet connector  4170   oc  with the swivelling disc  5050 , the outlet tube  4006  and the ribs  4177  engage prior to engagement of the AC electrical connector  4170   ec  and the electrical connector receiver  5052 . This configuration may also be advantageous in cases where the gas provided via the air circuit  4170  includes supplementary oxygen, as it may prevent occurrence of electrical arcing while the pneumatic circuit is not isolated. 
     A yet another feature of the current technology may be found in the arrangement of the receiver contact elements  5058   ce  on the female electrical connector  5058  in the electrical connector receiver  5052  as shown in  FIG. 18 m -18 n   . The electrical leads  41701   e  may engage the receiver contact elements  5058   ce  as the AC electrical connector  4170   ec  is inserted into the electrical connector receiver  5052  from the top of the connector TS. This engagement may occur via a sliding action in the direction of the arrow ENG shown in  FIG. 18 a -18 b   . The receiver contact elements  5058   ce  may be configured in a sloped, triangular profile as shown in  FIG. 18 n    and/or to be compliant in a perpendicular direction PER to the sliding plane to assist in their engagement with the electrical leads  41701   e.    
     The aforementioned triangular profile and/or compliance may allow improved engagement between the electrical leads  41701   e  on the AC electrical connector  4170   ec  and the receiver contact elements  5058   ce  as the AC electrical connector  4170   ec  is progressively inserted into the electrical connector receiver  5052 . During engagement with the AC electrical connector  4170   ec , as the AC electrical connector  4170   ec  slides along the length of the female electrical connector  5058  the contact elements  5146  may be depressed inwards and maintain contact to the electrical leads  41701   e . This may allow improved accommodation of mechanical tolerances from such sources as manufacturing variance or in-use deformation. 
     Still further, the receiver contact elements  5058   ce  may be biased, so that when deformed from its original configuration (as shown in  FIG. 18 n   ) and depressed inwards, the receiver contact elements  5058   ce  may be biased towards returning to the undeformed position, thereby improving the fidelity of its connection with the electrical leads  41701   e . Another advantage of such an arrangement of the female electrical connector  5058  may be that it is self-cleaning. As the female electrical connector  5058  and the AC electrical connector  4170   ec  may engage each other in a slide-on, slide-off action, it may prevent build-up of contaminants which, if left uncleaned, may affect the fidelity of the electrical connection formed between the two parts. 
     Any contaminants that have been removed by the wiping action may be prevented from entering the air path, for example by a swivel disc seal  5051 . In addition when the female electrical connector  5058  is arranged in a vertical position and the connection is made in a vertical direction any contaminants that are wiped off the electrical contacts will fall down below the connector. A cavity may be formed below the female electrical connector  5058  within the electrical connector receiver  5052  into which the contaminants may collect. This cavity is not in communication with the pneumatic path of the RPT device or the humidifier  5000 . 
       FIG. 18 z     1  shows the surface of the female electrical connector  5058  that may be connected to the cable  5070 . The connector comprises a plurality of weld points  5058   w   1 ,  5058   w   2 ,  5058   w   3 , for example such that there may be two weld points for each of the conductive tracks, which allows for improved mechanical strength against load. The connector may also incorporate one or more pegs, rivets or pins  5058   pe  for alignment during assembly and/or mechanical bonding. Optionally the one or more pegs, rivets or pins  5058   pe  may be heat staked to provide a mechanical restraint. In certain arrangements a washer or plate may be provided between the one or more pegs, rivets or pins  5058   pe  and the cable  5070  to spread the mechanical restraint force over a larger surface of the connector. 
       FIGS. 18 z     2 - 18   z   4  show another example of the female electrical connector  5058 , including another example of receiver contact elements  5146 , shown in further detail in  FIGS. 18 z     5 - 18   z   6 . A feature of this example of the receiver contact element  5058   ce  is that a bifurcated retention feature  5058   rf  is formed from the base portion  5058   bp  rather than the contact portion  5058   co  and/or the curved portion  5058   cu . The receiver contact elements  5058   ce  may be made from a material of high electrical and thermal conductivity with high strength and hardness, such as beryllium copper. 
     Having the exposed electrical connections on the outlet connector  4170   oc  of the air circuit  4170  provides additional electrical safety as the air circuit does not include a power supply but requires connection to swivelling disc  5050  on the RPT device  4000  and/or humidifier  5000  to receive power. Also, the exposed electrical connections that may be exposed to cleaning processes are also on the replaceable air circuit  4170  component. 
     5.4.1.9.4 Elbow Outlet Connector 
     By forming the AC outlet connector  4170   oc  with an elbow, as can be seen in  FIGS. 18 a -18 j   , the patient may be prevented from inadvertently pulling the air circuit  4170  off of the RPT device  4000  or the humidifier  5000 , because the direction of the tension force vector of the air circuit will be located at an angle (e.g., perpendicular) to the direction of engagement of the air circuit  4170  with RPT device  4000  or the humidifier  5000 . Also, as shown in  FIGS. 1 a - c   , the RPT device  4000  or the humidifier  5000  may be located on a nightstand, for example, during treatment such that the patient lying in bed is at substantially the same height as the RPT device or the humidifier. In such a situation, the inclusion of an elbow as part of the AC outlet connector  4170   oc  may allow the air circuit  4170  to be pointed more directly at the patient such that bend angles of the air circuit may be reduced, particularly at or near the elbow, which in turn may reduce stress on the air circuit. In one example of the present technology, the AC outlet connector  4170   oc  may include an elbow having an angle of about 90°. It should be understood, however, that any number of angles may be possible, such as for example between 0° and 120°, including 20°, 40°, 60°, 800 or 100°. The choice of this angle may be affected by any number of design requirements such as flow impedance, convenience, location of the AC outlet connector  4170   oc  or noise implications. 
     5.4.1.9.5 Rotatable Outlet Connector 
     As the patient may move during treatment, thus pulling the air circuit  4170 , it may be advantageous to further reduce the bend angles of the air circuit and reduce stress on the assembly, in particular the air circuit, as well as the connection thereto from the AC outlet connector  4170   oc . This may be accomplished by allowing the AC outlet connector  4170   oc  to rotate relative to the RPT device  4000  or the humidifier  5000  while the mechanical, pneumatic and electrical connections are maintained. The outlet tube  4006  also facilitates rotation of the AC outlet connector  4170   oc  of the air circuit  4170  by allowing the AC outlet connector  4170   oc  to rotate around the outlet end  4006   oe.    
     As described above, the air circuit  4170  may be connected to the RPT device  4000  or the humidifier  5000  by inserting the AC outlet connector  4170   oc  onto the outlet assembly  5004 , as shown in  FIGS. 16 a -16 b  and 18 f -18 j   . Rotatability may be provided by features shown in  FIGS. 18 p -18 r    for example. 
       FIGS. 18 p -18 r , 18 v  and 18 w    show various views of the swivelling disc  5050  according to various examples of the technology. It has been described above that the swivelling disc  5050  may be the component that receives the AC outlet connector  4170   oc  when connecting the air circuit  4170  to the RPT device  4000  or the humidifier  5000 . The swivelling disc  5050  may also provide rotatability relative to the RPT device and/or the humidifier. 
       FIG. 18 y    shows a perspective view of the bottom of the exemplary swivelling disc  5050  and the cable  5070 . In other words, this view depicts features of the swivelling disc  5050  that are located opposite the side to which the AC outlet connector  4170   oc  may connect. A cable  5070 , to be discussed in greater detail below, can be seen extending from an underside of the electrical connector receiver  5052 . The end of the cable  5070  that is inside of the electrical connector receiver  5052  may be in electrical communication with the AC electrical connector  4170   ec  when the AC outlet connector  4170   oc  is inserted onto the swivelling disc  5050 . The free end of the cable  5070  shown may be in electrical communication with at least one component of the RPT device  4000  or the humidifier  5000  (e.g., the central controller  4230 , PCBA  4202  or a power supply  4210 ). It should also be understood that the cable  5070  may be of any sufficient length to perform its connective function, as will be discussed in greater detail below. 
     The swivelling disc  5050  may also incorporate a swivel disc seal  5051  as shown in  FIG. 18 w -18 x -18 y    that may comprise a compliant material such as TPE. The swivel disc seal  5051  may function to maintain a seal between the swivelling disc  5050  and the outlet tube  4006  to prevent any contaminants from entering the air path, for example by extending around a periphery of the top of the swivelling disc  5050  and towards the base of the swivelling disc  5050  as shown in  FIGS. 18 v  and 18 y   . In one form, the swivel disc seal  5051  may be an overmoulded portion of the swivelling disc  5050 . 
     As described above, the AC outlet connector  4170   oc  may be releasably coupled to the swivelling disc  5050  by engagement of the retention features  4174  in corresponding notches  5054  and by engagement of the recess  4170   re  onto the electrical connector receiver  5052 . When connected to the swivelling disc  5050 , the AC outlet connector  4170   oc  may be able to rotate in unison with the swivelling disc and relative to the cable housing  5080 . 
       FIGS. 70 a - c    show views of the swivelling disc  5050  joined to the cable housing  5080 .  FIG. 70 a    shows a top view of an outlet assembly according to an example of the present technology. In  FIGS. 70 a - c    the swivelling disc  5050  may be in an intermediate rotational position relative to the cable housing  5080 . 
       FIG. 70 b    shows a cross-section of the outlet assembly  5004  across the symmetrical plane of the female electrical connector  5058  taken through line  70   b - 70   b  of  FIG. 70 a   . This example of the current technology shows an internal shoulder  5160  that recesses the female electrical connector  5058  from the opening of the electrical connector receiver  5052 , which may improve the electrical safety of the electrical connector receiver  5052  when engaging with and/or disengaging from the connector  4170   ec . Recessed placement of the female electrical connector  5158  from the opening of the electrical connector receiver  5052  may also prevent occurrence of any electrical arcing at or near an exposed area. The current arrangement of the female electrical connector  5058  and the electrical connector receiver  5052  may also prevent any powered components from being touched by a user. 
       FIG. 70 c    shows another cross-sectional view of the outlet assembly  5004  taken through line  70   c - 70   c  of  FIG. 70 a   . Inner wall  5082  of the swivelling disc  5050  can be seen within the outer wall of the cable housing  5280 . The tabs  5094  of the cable housing  5080  can also be seen. The flange  5112  of the swivelling disc  5050  can also be seen above the outer wall  5084  of the cable housing  5080 . 
     5.4.1.9.6 Limited Rotation 
     The disc stop surfaces  5060 ,  5062  (shown in  FIG. 18 y 18 x   ), discussed above, have a pair of complementary housing stop surfaces  5164 ,  5166  (shown in  FIG. 18 w 18 t   ) that may be located on an inner wall  5082  of the cable housing  5080 . By connecting the swivelling disc  5050  (as shown in  FIG. 18 v   ) to and within the inner wall  5082  of the cable housing  5080  (as shown in  FIG. 18 w   ), for example as shown in  FIG. 18 x   , the rotation of the swivelling disc  5050  relative to the cable housing  5080  may be limited by engagement of the disc stop surfaces  5060 ,  5062  to corresponding housing stop surfaces  5164 ,  5166  at or near its extreme positions. Rotation of the swivelling disc  5050 , in one example of the technology, may be limited to less than about 360°. Rotation may also be limited to an amount that is greater than about 180°. In a further example, rotation may be limited to about 270°. The desired range of rotation of the swivelling disc  5050  may be determined by a number of factors, such as the location of the swivelling disc  5050  with respect to the RPT device  4000  and/or humidifier  5000 , the elbow angle of the AC outlet connector  4170   oc , and material properties of the components. 
     The depicted examples show two pairs of complementary stop surfaces, as discussed above, that may represent opposite ends or surfaces of one structure. It may be possible to have multiple stop structures formed on respective components. For example, the stop surfaces on the inner wall of the housing may be provided with two separate protrusions thereon and likewise for the swivelling disc. It is also envisioned that multiple configurations of stop surfaces may be provided on a single combination of housing and swivelling disc such that one combination may include a number of available rotational limits. 
       FIG. 18 p    shows the swivelling disc  5050  rotated into one extreme position in the counter-clockwise direction relative to the cable housing  5080 .  FIG. 18 r    shows the swivelling disc  5050  rotated into another extreme position towards the other limit of travel in the clockwise direction relative to the cable housing  5080 .  FIG. 18 q    shows the swivelling disc  5050  in a position relative to the cable housing  5080  that is between the extreme positions shown in  FIGS. 18 p  and 18 r   . Although the swivelling disc  5050  does not allow the stop surfaces  5060 ,  5062 ,  5164 ,  5166  to be seen in  FIGS. 18 p -18 r   , it should be understood that when the swivelling disc  5050  is in either extreme position shown in  FIGS. 18 p  and 18 r    that one of the disc stop surfaces  5060 ,  5062  is engaged and/or abutted against a corresponding housing stop surface  5164 ,  5166 . 
     It should be understood that each AC tab  4176  of the AC outlet connector  4170   oc  includes a retention feature  4174  that is engaged with a corresponding notch  5054  of the swivelling disc  5050  to releasably connect the substructure to the swivelling disc so that they may rotate in unison relative to the cable housing  5080 . 
     5.4.1.9.7 Electrical Cable Connection 
     As discussed above, the cable  5070  may be provided to electrically connect the AC electrical connector  4170   ec  to at least one component of the RPT device  4000  or the humidifier  5000 . The cable  5070  (e.g. shown in  FIGS. 18 v -18 y , 18 u -18 x   ) may be a flexible circuit board (FCB) or a ribbon cable. The cable  5070  may also include multiple wires to provide multiple electrical connections for powering and signalling functions. The cable  5070  may be oriented such that the major or longer side is oriented in parallel to the axis of rotation of the swivelling disc. If an FCB is used as the cable  5070 , it may be oriented so that the surface of the FCB where the conductive tracks are located is protected from frictional contact with the cable housing  5080  as it rotates with the swivelling disc  5050 , in order to help prolong the life of the cable  5070 . Still further, the contacting surface (away from the conductive tracks) may comprise a low-friction surface so that when it slides relative to the cable housing  5080  the friction force created is minimised. This may have the effect of reducing the amount of wear occurring on the cable  5070 , as well as reducing the load imposed on the solder/mounting joints between the cable  5070  and any electrical connectors connected thereto, such as the female electrical connector  5058 . An example of such a low-friction surface may be a polyamide substrate. 
     5.4.1.9.8 Cable Management 
     In accordance with an example of the present technology, the cable  5070  may be fixed at one end to the electrical connector receiver  5052  of the swivelling disc  5050 . Although not shown, it should be understood that the opposite end of the cable  5070  may be fixedly connected to at least one component of the RPT device  4000  or the humidifier  5000  such as a PCBA  4202  to provide power to the cable. Thus, the cable  5070  may have a fixed length between the connection to the swivelling disc  5050  and the connection to at least one component of the RPT device  4000  or the humidifier  5000 . 
     The cable  5070 , in an example of the present technology shown in  FIGS. 18 p -18 r   , may also include a slack portion that may be contained within either an annular section between the inner wall  5082  and the outer wall  5084 , or a recess or void  5086  defined, at least in part, by the cable housing  5080  depending upon the position of the swivelling disc  5050 . The flange  5112  of the swivelling disc  5050  may also contribute to defining the upper cover of the annular section, however, the flange  5112  does not contact the cable  5070  within the annular section. The cable housing  5080  (see  FIG. 18 s   ) may also include the inner wall  5082  and an outer wall  5084 , both of which may further define the void  5086 . The cable housing  5080  may also include a retainer  5090 , which may help to maintain the cable  5070  in the proper orientation by reducing the chance of entanglement or pinching and to prevent the slack portion from being pushed out of the cable housing  5080 . The outer diameter of the retainer  5090  may be designed to provide a minimum diameter for bend of the cable  5070  without damaging the electrical elements of the cable  5070 , for example an outer diameter of approximately 4 mm, 4.5 mm, 5 mm or some other outer diameter. It is to be understood that the outer diameter size of the retainer  5090  may be varied depending upon the size and type of cable used. As can be seen in  FIG. 18 s   , the exemplary cable housing  5080  depicted may include an opening that may be formed in the shape of a slot and through which the cable  5070  may pass, while maintaining a substantially fixed length of the cable  5070  within the cable housing  5080 . 
     The cable  5070  is at least partially wrapped around the inner wall  5082  within the annular section  5174  when the swivelling disc is rotated towards the extreme position shown in  FIG. 18 r   . The cable  5070  does not wrap around the swivelling disc  5050  but moves with the swivelling disc within the annular section as the swivelling disc  5050  is rotated. 
       FIGS. 18 p -18 r    depict another feature of the depicted examples of the technology. As the swivelling disc  5050  is rotated between extreme positions the cable  5070  may be pushed and pulled between the void  5086  and annular section of the cable housing  5080  due to its connection to the swivelling disc  5050 . For example, when the swivelling disc  5050  is rotated from the position shown in  FIG. 18 p    to the position shown in  FIG. 18 r    it can be seen that a portion of the cable  5070  is pulled out of the void  5086  and into the annular section  5088 . It should be understood that the portion of the cable  5070  shown doubled back in the void  5086  in  FIG. 18 p   , for example, may be considered the slack portion. In other words, the slack portion may be the excess cable that represents a length of the cable beyond what is necessary for direct connection to the swivelling disc  5050 . Thus, as the swivelling disc  5050  is rotated from the position shown in  FIG. 18 p    to the position shown in  FIG. 18 q    the slack portion may be progressively removed from the void  5086  so that the slack portion of the cable  5070  may be progressively pulled into the annular section  5088  and begin to wrap around the inner wall  5082  as the cable is pulled. As the swivelling disc  5050  is rotated further, from the position shown in  FIG. 18 q    to the position shown in  FIG. 18 r   , the portion of the cable  5070  that is pulled into the annular section  5088  increases and the slack portion may be pulled completely or nearly completely from the void  5086 . The recess or void  5086  and the annular section  5088  may be formed on opposing sides of the inner wall  5082 . 
     Rotation of the swivelling disc  5050  in the opposite direction, from the position in  FIG. 18 r    to the position in  FIG. 18 q    to the position in  FIG. 18 p   , may cause the cable  5070  to be progressively pushed from the annular section  5088  and unwrapped from around the inner wall  5082  such that the slack portion in the void  5086  may increase and begin to double back. In an example of the present technology, the maximum slack portion of the cable  5070  may be of a fixed length. In another example, that fixed length may be less than about the circumference of the swivelling disc  5050  and/or about equal to the distance of an arc swept out by the electrical connector receiver  5052  as the swivelling disc rotates between extreme positions. It should also be understood that in an example of the present technology when the swivelling disc  5050  is in the position shown in  FIG. 18 p    the largest amount of the slack portion of the cable  5070  is gathered or contained in the void  5086 . 
     5.4.1.9.9 Cable Housing 
       FIGS. 18 s -18 t    depict features of the cable housing  5080  according to examples of the present technology. As described above, the cable housing  5080  may include the inner wall  5082  and the outer wall  5084  that together may define the void  5086  and the annular section  5088 . The inner wall  5082  may define an opening  5092  through which the outlet tube  4006  may extend when the outlet assembly  5004  is assembled onto the RPT device  4000  or the humidifier  5000 . Further facilitating this assembly, housing tabs  5094  (see  FIG. 18 t   ) may be located on the cable housing  5080  to attach the cable housing to the RPT device  4000  or the humidifier  5000 . This may improve the manufacturability and serviceability of the cable housing  5080 . The housing tabs  5094  may be configured so that they are, by themselves and/or as a set, able to support the weight of the humidifier  5000  and the RPT device  4000 . This may prevent damage from occurring to the humidifier  5000 , the RPT device  4000  or the cable housing  5080  when the assembly is accidentally lifted by the air circuit  4170  or the AC outlet connector  4170   oc . In some instances, the air circuit  4170  or the AC outlet connector  4170   oc  may be configured to mechanically fail if the humidifier  5000  and/or the RPT device  4000  is held in place and a force is imposed onto the air circuit  4170  and/or the AC outlet connector  4170   oc  in the upwards direction. 
     Returning to the inner wall  5082  and the outer wall  5084 , in an example of the present technology, the slack portion of the cable  5070  can be seen (for example, in  FIG. 18 p   ) to form a radius in the void  5086 . This radius may affect the stress imposed on the cable  5070  (and therefore potentially its operating life) and is defined in part by the distance (VO_W in  FIG. 18 s   ) between the inner wall  5082  and the outer wall  5084  in the void  5086 . Therefore, these walls may be separated by a distance in the range of 2 mm to 5 mm across the void  5086  based on a desired minimum radius of the cable  5070 . In one example, the distance is in the range of 4 mm to 5 mm. It should be understood that the desired minimum radius of the cable may change as a function of the properties of the cable  5070  and its design parameters such as design life, or usage cases. Similarly, the length (VOL in  FIG. 18 s   ) of the void  5086  may be lengthened or shortened according to the maximum slack length of the cable  5070 , which may be driven by the maximum rotation of the swivelling disc  5050 . 
     The width (AN_W in  FIG. 18 s   ) of the annular section  5088  between the inner wall  5082  and the outer wall  5084  may be minimised as the cable  5070  travels therein as the swivelling disc  5050  rotates from one extreme position to the other. This may have the benefit of reducing noise produced by the cable and preventing buckling of the cable in the annular section. The width of the annular section may be between approximately 1 mm and 4 mm, such as 2 mm or 3 mm, and it should be understood that the width may depend on various characteristics and/or properties of the assembly, such as the characteristics of the cable chosen or the radius of the inner wall  5082 . In some arrangements the inner wall  5082  of the annular section  5088  and/or the outer wall  5084  of the annular section  5088  may include dampening material to help improve sound performance when the swivelling disc is rotated. A dampening material may also ensure the cable moves around the inner wall  5082  rather than the outer wall  5084  or vice versa. 
     In an example of the present technology, the cable housing  5080  may be formed from polypropylene, or polycarbonate/acrylonitrile butadiene styrene (PC/ABS). The swivelling disc  5050  may be formed from a combination of polycarbonate/acrylonitrile butadiene styrene (PC/ABS) and a thermoplastic elastomer (TPE). 
     5.4.1.10 Oxygen Delivery Port  4180   
     In one form of the present technology, one or more oxygen delivery ports  4180  may be used to deliver supplementary oxygen to one or more points in the pneumatic path, such as upstream of the pneumatic block  4020 , to the air circuit  4170  or to the patient interface  3000 . 
     5.4.1.11 Power Supply  4210   
     A power supply  4210  may be located internal or external of the external housing  4010  of the RPT device  4000 . 
     In one form of the present technology power supply  4210  provides electrical power to the RPT device  4000  only. In another form of the present technology, power supply  4210  provides electrical power to both RPT device  4000  and humidifier  5000 . 
     5.4.1.12 Central Controller  4230   
     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 . 
     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. 
     In one form of the present technology, the central controller  4230  is a dedicated electronic circuit. 
     In one form, the central controller  4230  is an application-specific integrated circuit. In another form, the central controller  4230  comprises discrete electronic components. 
     The central controller  4230  may be configured to receive input signal(s) from one or more transducers  4270 , and one or more input devices  4220 . 
     The central controller  4230  may be configured to provide output signal(s) to one or more of an output device  4290 , a therapy device controller  4240 , a data communication interface  4280  and humidifier controller  5250 . 
     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 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. 
     5.4.1.13 Clock  4232   
     Preferably RPT device  4000  includes a clock  4232  that is connected to the central controller  4230 . 
     5.4.1.14 Therapy Device Controller  4240   
     In one form of the present technology, therapy device controller  4240  is a control module  4330  that forms part of the algorithms executed by the central controller  4230 . 
     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. 
     5.4.1.15 Protection Circuits  4250   
     The one or more protection circuits  4250  in accordance with the present technology may comprise an electrical protection circuit, a temperature and pressure safety circuit. 
     5.4.1.16 Memory  4260   
     In accordance with one form of the present technology the RPT device  4000  includes memory  4260 , preferably non-volatile memory. In some forms, memory  4260  may include battery powered static RAM. In some forms, memory  4260  may include volatile RAM. 
     Preferably memory  4260  is located on the PCBA  4202 . Memory  4260  may be in the form of EEPROM, or NAND flash. 
     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. 
     In one form of the present technology, the memory  4260  acts as a non-transitory computer readable storage medium on which are stored computer program instructions expressing the one or more methodologies described herein, such as the one or more algorithms. 
     5.4.1.17 Data Communication Interface  4280   
     In one preferred form of the present technology, a data communication interface  4280  is provided, and is connected to the central controller  4230 . The data communication interface  4280  may allow the RPT device  4000  to connect to another device or a network, such as a remote external communication network  4282 , a local external communication network  4284 , remote external device  4286  or a local external device  4288 . The data communication interface  4280  may communicate data with the other device/network that it is connected to, for example transmitting data from the RPT device  4000  regarding the patient&#39;s  1000  previous night&#39;s sleep, or receiving a message. 
     The remote external communication network  4282  or the local external communication network  4284  may be further connectable to another network or device, such as a remote external device  4286  or a local external device  4288  respectively as shown in  FIG. 5   d.    
     Examples of the remote external communication network  4282  may include the Internet and cellular telephone networks. The data communication interface  4280  may connect to the remote external communication network  4282  using one or more communication methods (wired or wireless) such as Ethernet, USB, optical fibre, CDMA, GSM, LTE. In some forms, the data communication interface  4280  may connect to a network via another network or device (not shown). 
     Examples of the local external communication network  4284  may include a home computer network and a hospital computer network. In one form, the local external communication network  4284  utilises one or more communication standards, such as Wi-Fi, Bluetooth, or a consumer infrared protocol. 
     In one form, the data communication interface  4280  may communicate with one or more servers containing one or more processors, memory and incorporating with other components typically present in general purpose computing devices. The data communication interface  4280  may communicate with a server as disclosed in the Australian provisional patent applications AU 2014901998, AU 2014901999 and AU 2014901997 the entire contents of which is incorporated herewithin by reference. 
     In one form, the remote external device  4286  is one or more computers. Such a remote external device  4286  may be accessible to an appropriately authorised person such as a clinician. Examples of local external device  4288  may include a personal computer, mobile phone, tablet or remote control. 
     In one form (shown in  FIGS. 10 a -10 b   ), the data communication interface  4280  may be a wireless communication module located on a separate PCBA to the main PCBA. The data communication interface  4280  may comprise an antenna  4280   an , and an antenna ground plane  4280   gp . The antenna ground plane  4280   gp  in this form may comprise the PCB, and may improve performance of the antenna  4280   an  (and thus performance of the data communication interface  4280 ). 
     The antenna  4280   an  may receive and transmit signal to allow the data communication interface  4280  to communicate, for example with a server as described above. The antenna  4280   an  may be an elongate member engaged with the antenna ground plane  4280   gp  (described in further detail below). The antenna  4280   gp  may be located towards an outer periphery of the RPT device  4000  so as to improve fidelity and strength of any signal to and from the antenna  4280   gp , for example adjacent to an edge of the side panel  4014  as shown in  FIG. 10 a   . In one form, the antenna  4280   gp  may be arranged so that its major axis is substantially oriented vertically for improved efficiency. 
     The geometry (e.g. a length) of the antenna ground plane  4280   gp , particularly in a direction perpendicular to the long axis of the antenna  4280   an , may affect a performance level of the ground plane  4280   gp  (and in turn the antenna  4280   an ). Typically, an increase to the length of the antenna ground plane  4280   gp  may be beneficial to its performance. Preferably, an antenna ground plane is arranged in a rectangular shape (not shown), extending in a direction perpendicular to a major axis of the antenna. The length of the antenna ground plane  4280   gp  is preferably such that a minimum performance requirement of the antenna ground plane  4280   gp  is met. Similarly to the antenna  4280   an  described above, the antenna ground plane  4280   gp  may be arranged substantially vertically, and located toward a periphery of the RPT device  4000 , for example engaged with the side panel  4014  as shown in  FIG. 10   a.    
     However, in some cases, the configuration of the RPT device  4000  (such as its overall size and arrangement of components therein) may prevent the antenna ground plane  4280   gp  from comprising (or exceeding) the length required to meet the minimum performance requirements without an accompanying increase to a size of the RPT device  4000 . Yet further, in some cases the RPT device  4000  may comprise one or more sources of radiation (such as a motor or others) which may raise the performance level required for the data communication interface  4280  to perform adequately. 
     According to one aspect of the present technology, the antenna ground plane  4280   gp  comprises one or more notches configured to increase the effective length of the ground plane  4280   gp . In such forms, the effective length of the ground plane  4280   gp  may be increased by the lengths of each side of the one or more notches. The one or more notches may allow a ground plane  4280   gp  to be arranged as a more complex geometric shape than a rectangle, such as that shown in  FIG. 10 b   , while improving the performance of the ground plane  4280   gp.    
     The effective total length (L eff ) of the ground plane  4280   gp  may be determined from the length of the antenna ground plate and the length of each side wall of each notch within the antenna ground plane  4280   gp . For example as shown in  FIG. 10 b   , the antenna ground plane  4280   gp  may comprise a notch having a first side  4280   n   1  and a second side  4280   n   2 . In this configuration, the effective total length (L eff ) of the antenna ground plane  4280   gp  is the sum of: the length of the antenna ground plane  4280   gp  (L 1 ), the length of the first side (L n1 ), and the length of the second side (L n2 ). Thus the effective length (L eff ) of the antenna ground plane  4280   gp  would be L eff =L 1 +L n1 +L n2 . 
     The notches may improve a performance of the wireless data communication interface, for example by more than 25% (e.g. by 35%, 50%, 65%, 80%), which may otherwise be achieved through an increase in a size of the antenna ground plane  4280   gp . As discussed above, inclusion of notches may thus beneficially allow a reduction in a size of the RPT device  4000  which may not be otherwise possible. 
     5.4.1.18 Input Devices  4220   
     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 . 
     In one form the input device  4220  may be constructed and arranged to allow a person to select a value or a menu option. 
     In one form as shown in  FIG. 9 a   , the RPT device  4000  may comprise a first button  4222 , for example to start or stop therapy, a second button  4224 , and a first dial  4226 . The first dial  4226  in some forms may be depressible to function as a button. 
     5.4.1.19 Output Devices Including Optional Display, Alarms  4290   
     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  4294  may include a Liquid Crystal Display (LCD) or Light Emitting Diode (LED) display. 
     5.4.1.19.1 Display Driver  4292   
     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. 
     5.4.1.19.2 Display  4294   
     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 LCD screen which is located on the front of the RPT device  4000  as shown in  FIG. 9 a   . In another 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. 
     In some forms, the display  4294  may be provided separately to the RPT device  4000 , or another device such as a smartphone may be used as the display  4294 . In such forms, the display  4294  may be in communication with the RPT device  4000  via the data communication interface  4280 . 
     5.4.1.20 User Interface Panel  4190   
     In one form, the RPT device  4000  may comprise a user interface panel  4190 , for example as shown in  FIGS. 12 a -12 d   . The user interface panel  4190  may include one or more of: a shield for the display  4294 , actuating mechanisms for the buttons  4222  and  4224 , an external housing light port  40101   p  (and a light well  41901   w ) for the ambient light sensor  4278  and one or more seals to prevent water ingress into an interior the RPT device  4000 . 
     The user interface panel  4190  may comprise a display cover  4294   co . The display cover  4294   co  may be configured to protect the display  4294  from damage while allowing an unobstructed view of the display  4294 , for example by being formed from a rigid, transparent material. In one form, the display cover  4294   co  may be formed with a curvature to act as a lens to assist viewing of the display  4294 . The user interface panel  4190  may further comprise a resilient material such as thermoplastic elastomer (TPE) or silicone, for example to perform as a seal. 
     The user interface panel  4190  may provide a dial aperture  4226   ap  to accept an encoder shaft  4226   sh  for the dial  4226  (see  FIGS. 13 a -13 b   ) therethrough. The user interface panel  4190  may comprise one or both of a dial seal  4226   se  and a dial cover  4226   co  to prevent ingress of water into the interior of the RPT device  4000  (as shown in  FIGS. 12 a -12 d   ). In one form, the dial cover  4226   co  is configured with a greater height at or near a top of the dial  4226  to encourage any water incident in the area to run downwards without ingress into the RPT device  4000  or even towards the dial seal  4226   se . The dial seal  4226   se  may further prevent water ingress by sealing around the encoder shaft  4226   sh  for the dial  4226 , while allowing rotation thereof. 
     According to one aspect, the user interface panel  4190  may comprise a UI base  4190   ba  and a UI seal  4190   se  as shown in  FIG. 12 b    and  FIG. 12 d   . The UI base  4190   ba  may perform one or more of the functions described above, for example as a shield for the display  4294 , actuating mechanisms for the buttons  4222  and  4224  and an external housing light port  40101   p  for the ambient light sensor  4278 . Accordingly, the UI base  4190   ba  may be constructed from a transparent material such as acrylonitrile butadiene styrene (ABS) or polycarbonate material. Such a construction may allow the UI base  4190   ba  to integrally comprise a light well  41901   w  (or a light pipe) configured as described above, in one form as a prism or a protrusion extending from under a first surface of the UI base  4190   ba  proximate to the ambient light sensor  4278  to above another, opposite surface facing the exterior of the RPT device  4000  as shown in  FIGS. 12 a -12 d   . In one form, one end of the light well  41901   w  may terminate to form the external housing light port  4010   lp.    
     The UI seal  4190   se  may seal one or more areas such as between the UI base  4190   ba  and the external housing  4010 , between the encoder shaft  4226   sh  and the UI base  4190   ba , between the display  4294  and the UI base  4190   ba , or between the UI base  4190   ba  and the buttons  4222  and  4224 . The UI seal  4190   se   4  may be engaged with the UI base  4190   ba  as an overmould, resulting in one integral user interface panel  4190  as shown in  FIG. 12 a    and  FIG. 12 c    for example, onto which buttons  4222  and  4224  may be coupled. The user interface panel  4190  may be then coupled with the main PCBA  4202  as for example shown in  FIG. 5   a.    
     As the RPT device  4000  may be used with a humidifier  5000  (discrete or integrated), the patient  1000  may often be interacting with the humidifier and the user interface sequentially, for example by filling up a water reservoir and then starting the RPT device  4000  or navigating a user menu. Accordingly, it may be advantageous for the user interface panel  4190  to effectively prevent or discourage water ingress into the RPT device  4000 . Furthermore, constructing the UI base  4190   ba  from one material, and to perform multiple functions as described above may lead to reduced manufacturing costs. 
     5.4.1.21 Front Panel  4012   
     One example of the front panel  4012  may be configured as shown in  FIGS. 14 a -14 b   . The front panel  4012  may be removable from the RPT device  4000 , for instance to allow the patient  1000  to customise the visual look of the RPT device  4000 , or to differentiate one model of the RPT device  4000  from another, where a plurality of models are available for example. In one form, the front panel  4012  may communicate with the central controller  4230  to customise an aspect of the RPT device  4000 , for example to provide one of a plurality of different modes of operation as described in U.S. patent application Ser. No. 14/204,041, the entire contents of which is incorporated herewithin by reference. 
     The front panel  4012  may comprise one or more retention features to allow the front panel  4012  to be secured onto the RPT device, such as by engagement with the external housing  4010 . In one form, the front panel  4012  may comprise one or more internal shoulders  4012   sh  (as shown in  FIG. 14 b   ) configured to engage with one or more complementary features on the external housing  4010 , such as the protrusions  4010   pr  (as shown in  FIGS. 13 a -13 b   ). The external housing  4010  may comprise an access point such as a front panel cutout  4010   co , configured to accept a finger of the patient  1000  for example to allow the patient  1000  to remove the front panel  4012 , such as by levering the front panel  4012  up from the external housing  4010 . The front panel  4012  may further comprise a cavity to allow access to light by the external housing light port  4010   lp.    
     5.4.2 RPT Device User Interface 
     The RPT device  4000  may comprise a user interface, for example comprising a visual interface shown through the display  4294 . The user (e.g. the patient  1000 ) may interact with the RPT device  4000  using the input devices  4220  as described above. 
     5.4.2.1 Visual Interface 
     The visual interface may comprise a menu of user-selectable items. The user may interact with the menu by selecting one of a plurality of items presented on the menu using the input devices  4220  such as a dial or by touching areas of a touchscreen. The user may confirm a selection by depressing a button or touching a touchscreen for example. 
     5.4.2.1.1 First Menu Screens 
     According to one aspect, a first menu screen  4295   m   1  presented to the user may be configured as shown in  FIGS. 15 a -15 b   . The first menu screen  4295   m   1  may present a limited number of sub-menu options to the user, for example two sub-menu options. According to another aspect, the sub-menu options may be arranged by a particular type of an interaction the user may have with the RPT device  4000 . For example, the first menu screen  4295   m   1  may comprise a selectable menu  4295   se  and a report menu  4295   re . The selectable menu  4295   se  may substantially comprise menu items with which a user may interact, and the report menu  4295   re  may substantially comprise menu items which may report information to a user. By substantially dividing the user interface into categories based on interactivity with the user, the user may be able to more effectively interact with the user interface and navigate through the sub-menu items. 
     In some instances, the first menu screen  4295   m   1  may be the very top level of a menu hierarchy or structure. Accordingly, the first menu screen  4295   m   1  may advantageously present the user with sub-menu options which are arranged by the particular type of interaction possible. 
       FIGS. 15 c -15 d    show another example of a first clinical menu screen  4295   m   2 , showing a ‘clinical’ menu comprising a selectable menu  4295   se  and a report menu  4295   re . The clinical menu may be activated by a predetermined operation, such as pressing particular user interface buttons in a particular sequence. Similarly to the first menu screen  4295   m   1 , first clinical menu screen  4295   m   2  may be the very top level of a menu hierarchy or structure for an alternative set of menu items (and sub-menu options). Although the first clinical menu screen  4295   m   2  presents different visual icons (and titles) to the first menu screen  4295   m   1 , arrangement of the two sub-menu options may be advantageously arranged by the particular type of interaction possible therewith, so that the layout of the user interface would remain consistent for improved usability. 
     Thus, in one form, the top level menu, regardless of whether it is a first menu screen  4295   m   1  or a first clinical menu screen  4295   m   2  may comprise a predetermined, consistent, number of sub-menu items, such as two, as shown in  FIGS. 15 a -15 d   . For instance, by arranging the very top level menu hierarchy to comprise a predetermined sub-menu items that are arranged by the type of interaction possible, the user may be able to advantageously maintain familiarity with the interface. This may be particularly advantageous as a significant percentage of users of medical devices such as RPT devices may not be proficient with high-technology gadgets or devices. 
     The selectable menu  4295   se  may comprise items which may be individually selected by the user, for example to make changes to a behaviour or a functionality of the RPT device  4000  (or the humidifier  5000 ), or to enter a sub-menu item. For example, the selectable menu  4295   se  may be displayed as shown in  FIGS. 15 a -15 d   , and once entered may comprise one or more configurable items such as therapy mode, ramp time, humidity level, language, date, units, mask type or pressure levels. In one example, the user may navigate to the sub-menu of the selectable menu  4295   se , and arrive at a selectable sub-menu  4295   o   1  or  4295   o   2 , depending on whether the navigation was from the first menu screen  4295   m   1  or the first clinical menu screen  4295   m   2  respectively as shown in  FIG. 15 e    or  FIG. 15 f   . In both cases, however, the user would have arrived at a series of selectable items. 
     The report menu  4295   re  may comprise items which relate to reporting of data. For example, the report menu  4295   re  (e.g. as shown in  FIG. 15 a    or  15   c ) once entered may comprise one or more report items such as total usage hours, events per hour, report of mask seal or report of humidifier performance. In another example, while the device is operating, the report menu  4295   re  (e.g. as shown in  FIG. 15 b    or  15   d ) once entered may comprise one or more statuses such as current pressure levels, leak level, remaining ramp time or humidifier status. In one example, the user may navigate to the sub-menu of the report menu  4295   re , and arrive at a report sub-menu  4295   r   1  or  4295   r   2 , depending on whether the navigation was from the first menu screen  4295   m   1  or the first clinical menu screen  4295   m   2  respectively as shown in  FIG. 15 g    and  FIG. 15 h   . In both cases, however, the user would have arrived at a series of selectable items as shown. 
     According to another aspect, the visual interface  4295  may be configured so that the items displayed on the first menu screen  4295   m   1  (or the first clinical menu screen  4295   c   1 ) may vary according to the context of the operation of the device, while the layout remains consistent, as seen in  FIGS. 15 a -15 d   . The first menu screen  4295   m   1  shown in  FIG. 15 a    may change to that shown in  FIG. 15 b    (and from  FIG. 15 c    to  FIG. 15 d   ) if the RPT device  4000  is in operation, changing the image displayed for the report menu  4295   re.    
     Similarly, the selectable menu  4295   se  appear at substantially same location in  FIGS. 15 a  and 15 c   , although the image displayed may vary depending on whether the first menu screen  4295   m   1  or the first clinical menu screen  4295   c   1  is displayed on the visual interface  4295 . 
     A composition of the first menu screen  4295   m   1  (or the first clinical menu screen  4295   c   1 ) which includes one sub-menu item comprising configurables, and another sub-menu item comprising reports may be beneficial in one or more respects. In one respect, the user may be able to navigate through the menu items with greater ease, as the structure of the menu would remain consistent despite any variations to the menu according to its operating conditions (e.g. operation of the RPT device  4000 , or differences between a clinical menu and a patient menu). Still further, maintaining a consistency of layout while varying images displayed thereon may effectively indicate a change in one or more operating conditions of the RPT device to the user without potentially causing confusion by a change in a menu structure. 
     5.4.2.1.2 Subsequent Menu Screens 
     Examples of sub-menus for the selectable menu  4295   se  are shown in  FIGS. 15 e  and 15 f   . It can be seen here that the contents of the selectable sub-menu  4295   o   1  and  4295   o   2  are selectable items, which may be actionable by the user, save for headings. For example, the user may scroll down to contents such as ‘Mask’ as shown in  FIG. 15 e    to change a type of mask that the RPT device  4000  is coupled to, or to ‘Humidity Level’ as shown in  FIG. 15 f    to change a level of desired humidity output of the humidifier  5000 . 
     Examples of sub-menus for the report menu  4295   re  are shown in  FIGS. 15 g  and 15 h   . The report sub-menus  4295   r   1  and  4295   r   2  may be configured so as to display information, in contrast to the contents of the selectable sub-menu  4295   o   1  or  4295   o   2  described above. 
     In one form, the sub-menus such as selectable sub-menu  4295   o   1  or  4295   o   2  or the report sub-menu  4295   r   1  or  4295   r   2  may comprise a greater number of items than can be displayed on the screen of the RPT device  4000  (or the humidifier  5000 ). The sub-menus may be thus configured so that a movable portion of the sub-menu (e.g. window portion  4295   w  in  FIGS. 15 e -15 g   ) is displayed on the screen by scrolling. Such an arrangement may be particularly useful in an arrangement wherein the user interface may comprise a relatively small screen, to reduce the amount of backwards and forwards navigation between different levels of sub-menus. 
     In one form, the report sub-menus  4295   r   3  or  4295   r   4  may display one or more aspects of an operation of the RPT device  4000  and the humidifier  5000  as for example shown in  FIGS. 15 i -15 j   . The one or more aspects may include, for example, a status of the humidifier  5000 , a fidelity of connection between the data communication interface  4280  and the other device/network that it is connected to, a quantity of leak or one or more settings of the RPT device  4000  and the humidifier  5000 . 
     In one form, the report sub-menus  4295   a   1 - 4295   a   8  may display one or more sequential images such as an animated arcuate portion shown in  FIGS. 15 k -15 p   . In one form, the report sub-menu may change to indicate a change of a status to the user. For example, the animated arcuate portion shown in  FIGS. 15 k -15 p    may be displayed to the user to indicate that the RPT device  4000  is in a ‘ramp’ period. Subsequently, at an end of the ramp period, the report sub-menu may change to one shown in  FIG. 15 q    to indicate an end of the ramp period to the user. 
     5.5 Humidifier  5000   
     5.5.1 Humidifier Overview 
     In one form of the present technology there is provided a humidifier  5000  to change the absolute humidity of air or gas for delivery to a patient relative to ambient air. Typically, the humidifier  5000  is used to increase the absolute humidity and increase the temperature of the flow of air (relative to ambient air) before delivery to the patient&#39;s airways. In one form, the humidifier  5000  may be a discrete unit that is connectable to an RPT device  4000 . In another form, the humidifier  5000  may be integrated with the RPT device  4000 , for example as shown in  FIG. 5 c    and as described in further detail below. 
     A humidifier  5000  may comprise a water reservoir  5110 , heating element  5240  and one or more transducers. The humidifier  5000  may be configured to receive a flow of air from a RPT device  4000  and deliver a flow of humidified air to a patient interface  3000  for example via an air circuit  4170 . 
     5.5.2 Humidifier Components 
     5.5.2.1 Water Reservoir  5110   
     According to one arrangement, the humidifier  5000  may comprise a water reservoir  5110  configured to hold, or retain, a volume of liquid (e.g. water) to be used for humidification of the flow of air.  FIGS. 16 c -16 d    show one form of a water reservoir  5110 , which comprises a reservoir base  5112 , a reservoir lid  5114 , and an intermediate portion  5202  including a compliant portion  5116 . The water reservoir  5110  is configured to hold a predetermined maximum volume of water in order to provide adequate humidification for at least the duration of respiratory therapy, such as one evening of sleep. Typically, the reservoir  5110  is configured to hold several hundred millilitres of water, e.g. 300 millilitres (ml), 325 ml, 350 ml or 400 ml. In other forms, the humidifier  5000  may be configured to receive a supply of water from an external water source such as a building&#39;s water supply system. 
     According to one aspect, the water reservoir  5110  is configured to add humidity to a flow of air from the RPT device  4000  as the flow of air travels therethrough. In one form, the water reservoir  5110  may be configured to encourage the flow of air to travel in a tortuous path through the reservoir  5110  while in contact with the volume of water therein. 
     The reservoir  5110  may also be configured to discourage egress of liquid therefrom, such as when the reservoir  5110  is displaced or rotated from its normal, working orientation, such as through any apertures or in between its sub-components. As the flow of air to be humidified by the humidifier  5000  is typically pressurised, the reservoir  5110  may also be configured to prevent losses in pneumatic pressure through leak or flow impedance. 
     The water reservoir  5110  may comprise an inlet  5118  for receiving the flow of air into the reservoir  5110 , and an outlet  5122  for delivering a flow of air from the reservoir  5110 . The reservoir  5110  may include to an reservoir inlet tube  5124  and an reservoir outlet tube  5126  (e.g., see  FIG. 16 e   ). In one configuration, the inlet  5118  and reservoir inlet tube  5124  are integrally formed as one inlet component and the outlet  5122  and the reservoir outlet tube  5126  are integrally formed as one outlet component. 
       FIG. 20-23  show one form of a water reservoir  5110 , which comprises a reservoir base  5112 , a reservoir lid  5114 , and a variable portion  5116 . The reservoir  5110  is configured to hold a given, maximum volume of liquid (e.g. water), typically several hundred millilitres, e.g. 300 millilitres (ml), 325 ml, 350 ml or 400 ml, although it is to be understood that other volumes of liquid may be utilised such as 100 ml, 200 ml, 250 ml, 500 ml or more or less. In one form, the reservoir  5110 , may comprise a cavity formed by a plurality of walls to hold the given, maximum volume of liquid as shown in  FIG. 22-23 . 
     5.5.2.2 Water Reservoir Dock  5130   
     A humidifier  5000  may comprise a water reservoir dock  5130  to receive a water reservoir  5110 . As shown in  FIG. 25 , the water reservoir dock  5130  may form a cavity  5160  to receive the water reservoir  5110 . In one form, the water reservoir dock  5130  may be integrated with the humidifier  5000  as shown in  FIG. 24-27 . The water reservoir dock  5130  may also connect the water reservoir  5110  to the pneumatic path. In this arrangement, the reservoir dock  5130  comprises a dock gas outlet  5168  to output a flow of breathable gases to a water reservoir  5110 , a dock gas inlet  5170  to receive the flow of breathable gases that has been humidified in the water reservoir  5110 , and a humidifier outlet  5172  to transfer the flow of humidified breathable gases to the air circuit  4170 . The cavity  5160  may include a top portion configured to cover at least a portion of the lid of the reservoir  5110  and a bottom portion including the heater plate  5120 . 
     It should be understood that the reservoir dock  5130  may be provided separately to a humidifier  5000  in an alternate arrangement. In such an arrangement, additional interfaces may be used to connect the reservoir dock  5130  to the humidifier  5000 . 
     In another arrangement, a water reservoir dock  5130  may comprise an opening in a substantially horizontal plane, so that the water reservoir  5110  may be inserted from above or below the water reservoir dock  5130 . 
     5.5.2.3 Water Reservoir Lid  5114   
     In one form, the water reservoir lid  5114  is pivotably connected to the base  5112  (e.g. by hinges  5158  as shown in  FIG. 16 e   ) to allow the reservoir  5110  to be converted between an open configuration and a closed configuration (see  FIGS. 16 k  and 16 k   ). When the water reservoir  5110  is in its closed configuration, the compliant portion  5116  is put into sealing engagement between the base  5112  and the lid  5114  to seal the base  5112  and the lid  5114 . The hinges  5158  may couple to complementary hinge recess portions  5159  (shown in  FIG. 16 f   ) located in the reservoir base  5112 . In one form, the lid  5114  may be constructed from a bio-compatible material, such as a plastic or thermoplastic polymer, for example, acrylonitrile butadiene styrene (ABS) or polycarbonate material. The pivotable connection may further allow the water reservoir lid  5114  and the base  5112  to be compressed towards each other in comparison to their normal operating configuration, for example for insertion of the reservoir  5110  into the dock  4130  as will be described in further detail below. 
     Another aspect of the present technology relates to the operation of the pivoting action in the lid  5114  in relation to the base  5112 . As the lid  5114  rotates about the hinges  5158 , a range of rotation may be defined as shown in  FIG. 62 a    and  FIG. 62 b   . In one form, two ends of the range of rotation may be defined by closure of the lid  5114  with respect to the base  5112 , where one of the two ends may be a fully open position defined by a rotation guide  5220 , which may interfere with a rotation stop  5222  at the fully open position. 
     According to another aspect, the lid  5114  may configured so that when a user attempts to open the lid  5114  further than the rotation stop  5222  and the rotation guide  5220 , the lid  5114  would disconnect from the base  5112 . As shown in  FIG. 62 b    and  FIG. 63 b   , at the fully open position the rotation guide  5220  may be in contact with the rotation stop  5222 . In this form, attempts to further open the lid  5114  with respect to the base  5112  would cause the rotation stop  5222  to act as a pivot of a cantilever, and cause the lid  5114  to separate from the base  5112  at the hinges  5158 , whereby damage to the reservoir  5110 , for example from application of excessive force thereto, may be avoided. In one form, the hinges  5158  may be configured to allow disconnection more easily at one orientation of the lid  5114  with respect to the base  5112  (e.g. then the reservoir  5110  is in the fully open position) than at another orientation. This may be achieved by, for example, introduction of a taper to the hinges  5158  on the lid  5114  as shown in  FIGS. 58 a    and  58   b.    
     The water reservoir lid  5114  may comprise the inlet  5118 , the reservoir inlet tube  5124 , the outlet  5122  and the reservoir outlet tube  5126  in one form as shown in  FIG. 16 e   . The reservoir  5110  may further comprise flow elements, such as a baffle (e.g. inlet cap  5125  shown in  FIG. 16 e    and  FIG. 16 k    and/or a plate  5123  as shown in  FIG. 16 e    and  FIG. 16 k   ), configured to increase the length of the tortuous flow path and/or to prevent ingress of water into the inlet tube  5124  and/or the outlet tube  5126 . In one example, the water reservoir lid  5114  may further comprise one or more baffles configured to direct the air through a tortuous path in the water reservoir  5110 . In one form, the baffle may be coupled to an end of the reservoir inlet tube  5124  as an inlet cap  5125  (as shown in  FIG. 16 e    and  FIG. 16 k   ), and in another form, the baffle may be arranged as a plate  5123  (as shown in  FIGS. 16 e  and 16 k   ). 
     5.5.2.4 Compliant/Variable Portion  5116   
     In one form, when the water reservoir  5110  is in use, the compliant portion  5116  may act as a seal between the reservoir base  5112  and the reservoir lid  5114 . The compliant portion  5116  may be provided as part of the reservoir lid  5114  or as part of the reservoir base  5112 , or independently of both, for example as part of an intermediate portion  5202  (see  FIGS. 16 l -16 m   ). The compliant portion  5116  may be engaged with the reservoir lid  5114  or the reservoir base  5112  by any number of means including, and not limited to, ultrasonic welding, friction fitting, gluing or by using an intermediate component. 
     The compliant portion  5116  preferably includes a sufficiently resilient construction so as to be able to resist forces and/or pressures generated in the reservoir  5110 , such as those generated by the user, the reservoir dock  5130  and/or the flow of air flowing through the reservoir  5110 . The compliant portion  5116  is also preferably compliant to be able couple to the lid  5114  and/or the base  5112 , and conform to its shape to form a seal. In one form, a rigid portion of the intermediate portion may be constructed from a nylon material of approximately 2 mm thickness (such as 1 mm, 1.5 mm, 2.5 mm or 3 mm), and a silicone material may be used to overmould onto the rigid portion to form the compliant portion  5116 . 
     In some arrangements, the compliant portion  5116  may couple to the lid  5114  and/or the base  5112 , and the base  5112  and/or the lid  5114  may be formed as two separate parts that are able to be assembled with the compliant portion  5116  coupled therebetween. 
     In an alternative arrangement, the compliant portion  5116  may be located within a wall of the reservoir base  5112  and/or a wall of the reservoir lid  5114 , for example integrally by overmoulding or as a separate component connected as a sub-assembly. In such an arrangement the compliant portion would not be located between the reservoir base  5112  and the reservoir lid  5114  but within the reservoir base  5112  and/or the reservoir lid  5114 . There may be more than one compliant portion  5116  or the compliant portion may be formed in multiple parts to provide more compliance in movement of the reservoir  5110 . 
     In one form, when the water reservoir  5110  is in use, the variable portion  5116  may act as a seal between the reservoir base  5112  and the reservoir lid  5114 . The variable portion  5116  may also perform other functions, such as to improve thermal contact between the reservoir  5110  and the heater plate  5120 , as will be described in further detail below. 
     The variable portion  5116  may be provided as part of the reservoir lid  5114  or as part of the reservoir base  5112 , or independently of both. The variable portion  5116  may be engaged with the reservoir lid  5114  or the reservoir base  5112  by any number of means including, and not limited to, ultrasonic welding, friction fitting, gluing or by using an intermediate component. The variable portion  5116  may comprise a carrier  5117  (as shown in  FIG. 23 ). 
     The variable portion  5116  is preferably constructed sufficiently resiliently so as to be able to resist compressive forces and/or pressures generated in the reservoir  5110 , such as by the user, the reservoir dock  5130  and/or the flow of breathable gas flowing through the reservoir  5110 . It is also preferably compliant in the planar direction to be able couple to the lid  5114  and/or the base  5112 , and conform to its shape. In one form, the carrier  5117  may be constructed from a nylon material of approximately 2 mm thickness (such as 1 mm, 1.5 mm, 2.5 mm or 3 mm), and a silicone material may be used to overmould onto the carrier  5117  to form the variable portion. 
     In some arrangements, the variable portion  5116  may couple to the lid  5114  and/or the base  5112 , and the base  5112  and/or the lid  5114  may be formed as two separate parts that are able to be assembled with the variable portion  5116  coupled therebetween. 
     In an alternative arrangement the variable portion  5116  may be located within a wall of the reservoir base  5112  and/or a wall of the reservoir lid  5114 , for example integrally by overmoulding or as a separate component connected as a sub-assembly. In such an arrangement the variable portion would not be located between the reservoir base  5112  and the reservoir lid  5114  but within the reservoir base  5112  and/or the reservoir lid  5114 . There may be more than one variable portion  5116  to provide more compliance in movement of the reservoir  5110 . 
     5.5.2.5 Water Reservoir Base  5112   
     According to one arrangement, the reservoir base  5112  comprises a conductive portion  5120  (such as the base conductor plate  5152 , e.g., see  FIG. 16 f   ) configured to thermally couple with a heating element  5240  of the humidifier  5000 . The conductive portion  5152  improves efficiency of heat transfer from the heating element  5240  to the volume of liquid in the reservoir  5110 . All or a part of the base conductor plate  5152  may be made of a heat conducting material such as aluminium (e.g. approximately 2 mm thick, such as 1 mm, 1.5 mm, 2.5 mm or 3 mm) or another heat conducting material such as metal. In some cases, suitable heat conductivity may be achieved with less conductive materials of suitable thickness. 
     The reservoir base  5112  may also be configured as a receptacle to retain the given, maximum volume of liquid that the reservoir  5110  is configured to hold. In one form, the base  5112  may comprise further features such as an overfill prevention feature. 
     In one form, the reservoir base  5112  may further comprise an inner lip  5224  and/or an outer lip  5226 , for example as shown in  FIG. 64  and  FIG. 65 . According to one aspect, the inner lip  5224  and/or outer lip  5226  may prevent egress of liquid from the reservoir  5110  through the interface between an intermediate portion  5202  (e.g. the compliant portion  5116 ) and the base  5112 , for example when the intermediate portion  5202  is compressed, or when the intermediate portion  5202  is under vibration. 
     It should be appreciated that the reservoir base  5112  may be constructed in any number of parts. The reservoir base  5112  may be constructed as a single part made of, for example, aluminium or another heat conducting material such as metal. In another arrangement, the reservoir base  5112  may be constructed in two parts, for example comprising a lower component and an upper component. 
     According to one arrangement, the reservoir base  5112  comprises a conducting portion (such as the base conductor plate  5152 ) configured to thermally couple with a heater plate  5120  of the humidifier  5000 . The conducting portion improves efficiency of heat transfer from the heater plate  5120  to the volume of liquid in the reservoir  5110 . All or a part of the base conductor plate  5152  may be made of a heat conducting material such as aluminium (e.g. approximately 2 mm thick, such as 1 mm, 1.5 mm, 2.5 mm or 3 mm) or another heat conducting metal. In some cases, suitable heat conductivity may be achieved with less conductive materials of suitable thickness. 
     The reservoir base  5112  may also be configured as a receptacle to retain the given, maximum volume of liquid that the reservoir  5110  is configured to hold. In one form, the base  5112  may comprise further features such as an overfill prevention feature as will be described in further detail below. The reservoir base  5112  may also comprise a base upper body  5146  and a base bottom plate  5148 , which together with the base conductor plate  5152  may form a receptacle. 
     The base upper body  5146  and/or the base bottom plate  5148  may be constructed from a bio-compatible material suitable for retaining the body of liquid, such as a plastic or thermoplastic polymer, for example, ABS or polycarbonate material. The base conductor plate  5152  may comprise of a sealing element  5150 , which may be integrated to, and/or sealingly connected to both the base upper body  5146  and the base bottom plate  5148  to prevent egress of water from the water reservoir  5110 , particularly from the base  5112 . For example, the sealing element  5150  may be overmoulded onto the base conductor plate  5152 , and the resulting component may be secured between the base upper body  5146  and the base bottom plate  5148 . 
     In one form as shown in  FIG. 23 , the base  5112  may comprise a base upper body  5146 , a base bottom plate  5148 , and a base conductor plate  5152 . However, it should be appreciated that the reservoir base  5112  may be constructed in any number of parts. The reservoir base  5112  may be constructed as a single part made of, for example, aluminium or another heat conducting material such as metal. In another arrangement, the reservoir base  5112  may be constructed in two parts, for example comprising a lower component and an upper component. In such an arrangement, the lower component may be constructed from a heat conducted material and perform the roles of the base conductor plate  5152 , sealing element  5150  and base bottom plate  5148 , and the upper component may be equivalent to the base upper body  5146 , and be constructed a polycarbonate material. 
     In one form, the reservoir base  5114  may further comprise an inner lip  5224  and/or an outer lip  5226 , for example as shown in  FIG. 65 - FIG. 65 . According to one aspect, the inner lip  5224  and/or outer lip  5226  may prevent egress of liquid from the reservoir  5110  through the interface between an intermediate portion  5202  (e.g. the seal  5204 ) and the base  5114 , for example when the intermediate portion  5202  is compressed, or when the intermediate portion  5202  is under vibration. 
     5.5.2.6 Reservoir Handles  5154   5156   
       FIG. 24-27  show an upper handle  5154  that is located on the reservoir lid  5114 , and a lower handle  5156  that is located on the reservoir base  5112 . These handles are intended to assist the patient (or user)  1000  to grip and hold the water reservoir  5110 . In the shown arrangement, the handles  5154 ,  5156  are located away from the hinges  5158  such that by holding the reservoir  5110  by the handles  5154   5156  the patient  1000  imparts forces onto the reservoir  5110  compressing the variable portion  5116 , which pushes the lid  5114  and the base  5112  towards each other. A compression force may also help maintain the variable portion  5116  in sealing engagement between the reservoir base  5112  and the reservoir lid  5114 , such as during transport to/from re-filling the reservoir  5110  with liquid. It is to be understood that the handles  5154  and  5156  may be placed on other components or areas of the water reservoir  5110 . 
     A friction grip  5166  may be provided on a surface of either or both of the handles  5154   5156  as shown in  FIG. 25 . The friction grip  5166  may be constructed to assist the patient  1000  to hold the reservoir  5110 , such as by being made from a higher friction material, made in a higher friction texture and/or made into an easier- to hold shape than the surrounding areas of the reservoir  5110 . For example, the friction grip  5166  may be constructed from an elastomeric material such as silicone whereas the water reservoir  5110  may primarily be constructed from a polycarbonate material. 
     5.5.2.7 Air Flow Path 
     It is one of the aims of the present technology to force the flow of breathable gas to travel through the reservoir  5110  in a tortuous path between the inlet  5118  and the outlet  5122 . This prevents any ‘short-circuiting’ of the flow of breathable gas, which may lead to inadequate humidity in the flow of breathable gas which is delivered to the patient  1000 . 
       FIG. 28 a -30 c    show an exemplary path of the flow of breathable gas through the reservoir  5110  as it enters through the inlet  5118  and exits through the outlet  5122 . The figures are arranged chronologically in three distinct orthogonal views per figure to visually demonstrate the exemplary flow path. In this arrangement the flow of breathable gas received through the inlet  5118  passes through the inlet tube  5124  ( FIGS. 28 a -28 c   ), into the internal volume of the water reservoir  5110  ( FIG. 29 a -29 c   ). The flow of breathable gas then passes through the outlet tube  5126  to exit the water reservoir  5110  at the outlet  5122  ( FIG. 30 a -30 c   ) as humidified breathable gas.  FIG. 28 a -30 c    show the reservoir  5110  with the lid  5114  and the base  5112  in exploded view orientation for clarity, and any flow of gas that occurs in the internal volume of the reservoir  5110  is shown in dotted lines. The dotted arrows shown indicate the general direction of the exemplary flow of breathable air, although it is noted that the nature of gas or air flow means that any gas flow path includes swirling (e.g. turbulence) of the gas rather than a straight and direct air flow path. 
     In some forms of the present technology, the reservoir  5110  may comprise flow elements, or a baffle  5192 , configured to increase the length of the tortuous flow path and/or to prevent ingress of water into the inlet tube  5124  and/or the outlet tube  5126 . For instance, the reservoir  5110  may comprise a deflector portion  5198  as shown in  FIG. 52 a   - 55 , or a deflector portion  5198  or a flow director  5195   FIG. 58 a -58 b   . In some arrangements, the baffle  5192  may further comprise a locating portion  5196  as will be described in further detail below. 
     In the arrangement shown in  FIG. 52 a   - 55 , the deflector portion  5198  is configured to prevent the flow of breathable gas from entering the outlet tube  5126  immediately after exiting the inlet tube  5124  through the inlet tube outlet  5125  (i.e. short-circuiting). When assembled together as seen in  FIG. 52 a   , the deflector portion  5198  may be located close to the inlet tube inner end  5125 , such as by abutting it. In this arrangement, the deflector portion  5198  forms a cover between the inlet tube outlet  5125  and a base of the outlet tube inner end  5127 . This cover may be further advantageous in that it forces the flow of breathable gas to travel in a channel created by the cover and the volume of water for improved humidity pickup. 
     In the arrangement shown in  FIG. 58 a -58 b   , the reservoir  5110  includes a flow director  5195  as well as a deflector portion  5198 . The deflector portion  5198  is configured to prevent short-circuiting of the flow of breathable gas, and the flow director  5195  is further configured to direct the flow of breathable gas that exits the inlet tube  5124  in a direction approximately parallel with the volume of liquid in the reservoir  5110 . This may ameliorate occurrence of ‘spitting’, which can occur when the flow of breathable gas exits the inlet tube  5124  in a direction normal to the surface of the volume of liquid. 
     As shown in  FIG. 33-34 , the reservoir  5110  may include an end wall  5128  that is near and opposed to an interior end  5125  of the inlet tube  5124 . The inner end wall  5128  of the reservoir  5110  directs air exiting the inlet tube  5124  to flow across the water surface before it reaches an interior end  5127  of the outlet tube  5126  and flows out of the outlet  5122  through the outlet tube  5126 .  FIG. 35-38  show examples of other arrangements of flow elements, wherein the reservoir  5110  may include a turning vane  5136  which is placed near the interior end  5125  of the inlet tube  5124 . The turning vane  5136  may be formed as an extension of the inlet tube  5124  as shown in  FIG. 37-38 , or the turning vane  5136  may be a separate component located adjacent to or coupled with the inlet tube  5124 . The turning vane may also be profiled as shown in  FIG. 37-38 . 
     The path of the flow of breathable air demonstrated in  FIG. 28 a -30 c    is exemplary only, and is aimed to demonstrate one of many paths that the flow of breathable gas may traverse through, namely that it enters the water reservoir  5110  through the inlet  5118  and exits through the outlet  5122  after experiencing some degree of swirling within the volume of the water reservoir  5110 . A person skilled in the art would understand that the particles or molecules that form the flow of breathable air may not follow a single path within the water reservoir  5110  due to a number of factors, including, for example, localised turbulence (eddies) or pressure gradients within the water reservoir  5110 . As a result the cumulative path of the flow of breathable air may comprise any number of paths wherein it experiences various degrees of ‘swirling’ within the water reservoir  5110  prior to exiting via the outlet tube  5126  at the outlet  5122 . It is also possible that some small portion of the flow of breathable air may escape the water reservoir  5110  as a leak. 
     5.5.2.8 Reservoir Inlet/Outlet 
     As described above, the reservoir inlet  5118  is configured to receive the flow of breathable gas into the reservoir  5110 , and the reservoir outlet  5122  is configured to output the humidified flow of breathable gas. The inlet  5118  and/or the outlet  5122  are preferably further configured to prevent egress of liquid from the reservoir  5110  when the reservoir  5110  is displaced and/or rotated from its normal, working orientation. Still further, the inlet  5118  and/or the outlet are preferably configured to prevent short-circuiting of the flow of breathable gas as described above. In one form, the inlet  5118  may be configured to prevent ‘spitting’, or splashing, of liquid which may be caused by a jet of air impinging on the volume of liquid in the reservoir  5110 . 
     In one arrangement as shown in  FIG. 33 , the reservoir inlet  5118  includes an inlet tube  5124  to provide a flow path for the inlet flow of breathable gas into the reservoir  5110 , and the reservoir outlet  5122  includes an outlet tube  5126  to provide a flow path for the outlet flow of humidified breathable gas from the reservoir  5110 . 
     In one configuration as shown in  FIGS. 37-38 , it may be advantageous to configure the turning vane  5136  so that the lowest portion of the turning vane  5136  extends below the lowest portion of the outlet tube  5126 . This may further prevent ingress of water into the inlet tube  5124  from any ‘spitting’ of water. 
     The water reservoir  5110  is preferably configured to provide tilt spillback protection from the water flowing back through the outlet tube  5126  or the inlet tube  5124 . Water egress through the inlet tube  5124  may be particularly undesirable as it may introduce water into the PAP device  4000  and damage electronic components (such as an electric motor, a flow sensor or a printed circuit board) from exposure to water. 
     In one arrangement of the present technology, the reservoir  5110  achieves spillback protection by arranging the inlet tube outlet  5125  so that when the reservoir  5110  is rotated by 90 degrees in any direction from its working, horizontal orientation the given maximum volume of water is able to be stored in the reservoir  5110  without reaching the inlet tube inner end  5125 . 
     In another arrangement of the reservoir  5110 , the axes of inlet tube  5124  and the outlet tube  5126  may intersect when viewed from above as shown in  FIG. 39-40 . The inlet tube  5124  and outlet tube  5126  may not be connected to each other as one of the tubes passes below the other tube, such as the inlet tube  5124  passes below the outlet tube  5126 . 
     This configuration may improve the tilt spillback protection by arranging the inlet tube  5124  and the outlet tube  5126  such that when the reservoir  5110  is tilted away from its working orientation, water must reach the higher end of the inlet tube  5124  or the outlet tube  5126  to exit the reservoir  5110 . For example, if the reservoir  5110  was tilted such that the water reaches the lower of the interior end  5125  of the inlet tube  5124 , the water must still rise higher to reach the exterior end of the inlet tube  5124  to exit the reservoir  5110  as shown in  FIG. 40 . 
     Simplified representations of the effects created by crossed inlet and outlet tubing are shown in  FIG. 46-49 , wherein the internal surfaces are shown by dotted lines. These figures show alternate arrangements of a water reservoir  5110 , with an inlet  5118  and an outlet  5122  that respectively include an inlet tube  5124  and an outlet tube  5126 .  FIG. 46-47  show a configuration wherein the axes of the tubing intersect when viewed from the side (as shown in  FIG. 47 ), and  FIG. 48-49  show an alternate configuration wherein the axes of the tubing are substantially parallel when viewed from the side (as shown in  FIG. 49 ). In  FIG. 46-49 , a volume of water  5182  is assumed to fill approximately half of the volume of the reservoir  5110 , and the water level  5184  is indicated by the dotted lines extending horizontally. 
     When the water reservoir  5110  is oriented as shown in  FIG. 46-47 , the arrangement of the inlet tube  5124  and the outlet tube  5126  requires the water level  5184  to rise above the higher end of the inlet tube  5124  or the higher end of the outlet tube  5126  if any water  5182  is to exit the water reservoir  5110 . On the other hand, in the arrangement shown in  FIG. 47-48  the water level  5184  only needs to rise as high as a lower end of the inlet tube  5124  or the outlet tube  5126  in order to exit the water reservoir  5110 . 
     As the water level  5184  will change as a function of the orientation of the water reservoir  5110 , this effect of crossing the inlet tube  5124  and the outlet tube  5126  may be re-created at any orientation as required by re-orienting the inlet tube  5124  and the outlet tube  5126  to suit the shape of the water reservoir  5110 . In some forms, the inlet tube  5124  and the outlet tube  5126  may be crossed when viewed from multiple angles orthogonal to each other. 
     In the forms shown in  FIG. 39-40  and  FIG. 46-49 , inlet interior end and the outlet interior end are located within the cavity and the inlet exterior end and the outlet exterior end are located in one of the plurality of walls of the cavity. A first axis (inlet tube axis) is defined by the inlet interior end and the inlet exterior end and a second axis (outlet tube axis) is defined by the outlet interior end and the outlet exterior end. When the reservoir is tilted (for example by approximately 90° to normal working orientation) the first axis is on a first angle such that the inlet interior end and the inlet exterior end are positioned at different heights, such that the predetermined maximum volume of water is below at least one of the inlet interior end or the inlet exterior end to prevent spillback of water through the inlet tube. Furthermore, when the reservoir is tilted (for example by approximately 90° to normal working orientation) the second axis is on a second angle such that the outlet interior end and the outlet exterior end are positioned at different heights, such that the predetermined maximum volume of water is below at least one of the outlet interior end or the outlet exterior end to prevent spillback of water through the outlet tube. This effect may be also created wherein the reservoir is tilted at any other angles, to suit the design and/or tilt conditions of the humidifier  5000  and/or reservoir  5110 . 
     5.5.2.9 Reservoir Arrangement with Removable Inlet/Outlet Tubes 
     In a yet further example of the current technology, the reservoir  5110  may be configured as shown in  FIG. 52 a   - 53 . In this example, the reservoir  5110  comprises a lid portion  5114 , an intermediate portion  5202  and a base portion  5112  (base portion not shown in  FIG. 52 a -52 b    for clarity). The lid portion  5114  and the intermediate portion  5202  may be configured to be releasably engaged to each other. They may be further configured to comprise a number of features when engaged to each other, such as an inlet  5118 , an outlet  5122 , an inlet tube  5124  and an outlet tube  5126 , while being releasably engaged to each other. For example, the lid portion  5114  may comprise an inlet  5118 , an outlet  5122  and an inlet tube  5124 , and the intermediate portion  5202  may comprise an outlet tube  5126  as shown in  FIG. 52   b.    
     As shown the intermediate portion  5202  may also comprise a baffle  5192  and at least one support spoke  5194 . The support spokes  5194  may be provided for structural support and/or to position the outlet tube  5126  and/or the baffle  5192  on the intermediate portion. The baffle  5192  is arranged to block a direct air path (or short-circuiting as described above) between the inlet tube inner end  5125  and the outlet tube inner end  5127  to encourage movement of the airflow within the reservoir to improve humidity uptake by the airflow within the reservoir  5110 . In addition a seal  5204  may be either integrated with the intermediate portion  5202  as shown or may be formed as separate component to the intermediate portion. 
     An advantage of this arrangement may be improved cleanability of the reservoir  5110  by separating some of the components from the reservoir, such as the inlet tube  5124  and/or the outlet tube  5126 . This arrangement may be particularly advantageous in such situations as when at least one of the inlet tube  5124  or the outlet tube  5126  extends into the internal volume of the reservoir  5110 , as such features may hinder access the interior of the reservoir  5110 . It can be seen in  FIG. 52 a -52 b    that the intermediate portion  5202  is engaged with the lid portion  5114  in its normal working orientation. However, as the intermediate portion  5202  is separable from the lid portion  5114 , the inlet tube  5124  and the outlet tube  5126  may be separated to improve access to the interior of the lid portion  5114 . 
     By using two separable portions  5114 ,  5202  to construct the upper portion of the reservoir and/or configuring the inlet/outlet tubes  5124 ,  5126  to be releasably engaged to the reservoir  5110 , the number of small, difficult-to-access areas may be reduced, which may improve cleanability of the reservoir  5110 . Furthermore, the removable inlet tube  5124  and/or the removable outlet tube  5126  may be themselves more easily accessible for cleaning as well. 
     In another example of the current technology (not shown), the lid portion  5114  and the intermediate portion  5202  may each comprise parts of a feature, wherein they would combine to form a complete feature. For instance, the lid portion  5114  may comprise a part of the inlet tube  5124  and a part of the outlet tube  5126 , and the intermediate portion  5202  may comprise another part of the inlet tube  5124  and another part of the outlet tube  5126 . Those skilled in the art will understand that the reservoir may be further sub-divided into any number of separable portions, and separable features such as the inlet tube  5124  and/or the outlet tube  5126  may be located in any number of arrangements in relation to the separable portions. 
     Another advantage of the current arrangement may be to improve spillback performance (prevention of liquid egress through the inlet tube  5124  and/or outlet tube  5126 ) of the reservoir  5110 . Spillback performance may be improved by increase of the internal volume of the reservoir  5110 , which may be achieved by introduction of a void above the inlet tube  5124  and/or the outlet tube  5126 . Another method of improving spillback performance is to arrange the inlet tube inner end  5125  and/or the outlet tube inner end  5127  proximal to the center of the reservoir  5110 . As a reservoir  5110  is typically produced by injection molding, forming an inlet tube  5124  and/or an outlet tube  5126  as a part of the lid  5114  prohibits introduction of a void above the inlet tube  5124  and/or the outlet tube  5126 . In such a configuration, a molding tool comprising the internal volume of the lid  5114  would be pinned in place by the inlet tube  5124  and/or the outlet tube  5126  and thus molding would not be possible, or require a complex and costly tooling arrangement. In such a case, the ability to separate the inlet tube  5124  and the outlet tube  5126  may be further advantageous. 
     It will be understood that the lid portion  5114 , the intermediate portion  5202  and the base portion  5112  may be configured in any number of ways. For instance, the relative sizes of the lid portion  5114  and the base portion  5112  may vary, and the lid portion  5114  and/or the base portion  5112  may further comprise multiple materials or components in its construction. One or more of the inlet tube  5124  and the outlet tube  5126  may be removably or releasably coupled to the lid portion  5114  or the base portion  5112 , for example as a part of the intermediate portion. The intermediate portion may also be configured to initially engage the lid portion  5114  and/or the base portion  5112 , for example by being configured to be inserted into the lid portion  5114  or the base portion  5112 . 
     Another feature of this arrangement is the use of support spokes  5194  in order to provide structural rigidity to the intermediate portion  5202  of the lid  5114 . The spokes  5194 , by themselves or in combination with the baffle  5192 , may provide a handle for disassembly of the lid  5114  from the intermediate portion  5202 . This may improve usability of the lid  5114  as the user may grip the baffle  5192  and/or the spokes  5194  to separate the intermediate portion  5202  from the lid portion  5114 . It should be understood that a number of other configurations may be possible wherein the support spokes  5194  are arranged alternatively to the exemplary arrangement as shown in  FIG. 54 a   - 55 . 
     In an example of the current technology, the baffle  5192  may comprise a locating portion  5196  and a deflector portion  5198  as seen in  FIG. 54 a   - 55 . The locating portion  5196  may be in the form of a cylinder to assist in accurately locating the baffle  5192  in relation to the inlet tube  5124  by fitting around the outside of the vertical portion of the inlet tube  5124 . In some forms, the baffle  5192  may further comprise a baffle seal  5197  to seal between the baffle  5192  and the inlet tube  5124 , for example as shown in  FIG. 59 b   . The baffle  5192  may also be configured in combination with the spokes  5194  so that at least some portions of the baffle  5192  may act as a spoke  5194  or vice versa. 
     An exemplary cross-section of the assembled lid  5114  is shown in  FIG. 56 a -56 b   . The diameter of the inlet tube  5124  or the locating portion  5196  may be varied along its length, for example in a frustro-conical arrangement, so as to progressively engage with each other. The two components  5124 ,  5196  may also incorporate a complementary retaining mechanism such as a protrusion/slot combination  5205  as shown in  FIG. 56 a   - 56   b.    
     It is also to be understood that the seal  5204  may be located at an alternative location to the exemplary arrangements shown in  FIG. 52 a   - 55 . For example, the seal  5204  may be formed as a part of the lid portion  5114 , as a part of the reservoir base portion  5112 , or as a separate component by itself that is not integrally formed to any of the lid portion  5114 , the intermediate portion  5202  and the base  5112 . One exemplary method of forming the seal  5204  with the lid portion  5114  or the base  5112  may be by overmoulding or use of a chemical adhesive. 
       FIG. 57  shows an exploded view of another example of the current technology. In this arrangement, the reservoir  5110  comprises a lid portion  5114 , an intermediate portion  5202  and a base portion  5112  (not shown in  FIG. 57  for clarity). The intermediate portion  5202  comprises the inlet tube  5124  and the outlet tube  5126  as well as a wall portion  5206  that is configured to be coupled with the lid portion. Alternatively the intermediate portion  5202  may engage the base portion  5112 , and may comprise one or both of the inlet tube  5124  and the outlet tube  5126 . In some cases, the wall portion  5206  that is configured to couple with the lid portion may connected with one or more of the inlet tube  5124  and the outlet tube  5126 . 
     This configuration may allow removal of the inlet tube  5124  and/or the outlet tube  5126  for improved cleanability of the reservoir  5110 . Furthermore, this configuration may improve spillback performance of the reservoir  5110  by increasing the internal volume of the reservoir  5110 . 
     In some cases, the inlet tube  5124  and the outlet tube  5126  may be arranged so that removal of either or both of the tubes  5124 ,  5126  from the reservoir  5110  does not affect the predetermined maximum volume of water that the reservoir  5110  may retain. Such a configuration may allow cleaning of the tubes  5124 ,  5126  without removing any water from the reservoir  5110 . 
     5.5.2.10 Overfill Prevention 
     In some prior art humidifier water reservoirs, overfilling of the water reservoir  5110  may reduce effectiveness of a spill prevention feature. For example, overfilling may allow the liquid in the reservoir  5110  to reach the inlet  5118  at a lower angle of tilt than if the reservoir  5110  had not been over-filled. As a result, some prior art humidifier water reservoirs have included a water filling indication mark to reduce occurrence of such overfilling, however this may only go some way towards ameliorating this risk. 
     Another aspect of this technology is the inclusion of one or more overfill protection features configured to prevent filling the reservoir above the maximum volume of water when filling the humidifier reservoir in its open configuration and/or the closed configuration. 
     In one arrangement as seen in  FIGS. 41 a  and 41 b   , an overfill protection feature may include at least one orifice  5138  in the water reservoir  5110  to indicate over-filling. According to this aspect of the technology, when the water reservoir  5110  is being re-filled with the reservoir lid  5114  open, over-filling beyond a predetermined maximum volume of the reservoir  5110  would cause water to spill out from the orifice  5138 . This would indicate to the user that the reservoir  5110  is full, as well as preventing such overfilling. Advantageously water would spill out only through the at least one orifice  5138  rather than from all areas of the water reservoir resulting in less overflow spillage for the user to clean up. Thus, the at least one orifice defines an egress path of water when the predetermined maximum volume of water is exceeded.  FIG. 41 a    show the water reservoir  5110  in its open configuration, wherein an upper flange of the base  5112  does not span the perimeter of the entire opening, creating an orifice  5138 .  FIG. 41 b    shows a portion of the base  5112  indicating the at least one orifice  5138 . The at least one orifice  5138  may be in the form of one or more apertures, holes, slits or slots, or any other form that allows communication of fluid into and out of the water reservoir  5110 . The at least one orifice  5138  may be formed in one or more positions around the upper flange of the base  5112 . 
     In an alternate arrangement, the overfill protection feature may include a sloped profile  5139 . As shown in  FIGS. 41 c  and 41 d   , the reservoir base  5112  may be arranged so that its side profile has a sloped profile  5139  in one or more directions. This arrangement may also indicate over-filling when the reservoir base  5112  is re-filled with liquid or water. In this arrangement, when the reservoir lid  5114  is in its open configuration, water may spill out at the base of the sloped profile  5139  rather than from all areas of the reservoir. Thus, the sloped profile defines an egress path of water when the predetermined maximum volume of water is exceeded. Advantages of the above methods may be that over-filling may become more difficult than has been in the prior art, and presents another advantage that in response to attempted over-filling, spillage may occur at more predictable locations. 
     Another aspect of this technology is that when the water reservoir  5110  is in its closed position, a seal  5204  sealingly engages the base  5112  and the reservoir lid  5114  and blocks or seals the orifice  5138  or sloped profile  5139  preventing fluid communication into and out of the water reservoir  5110 . One arrangement of this feature is shown in  FIG. 42 , which shows that when the reservoir lid  5114  is closed (lid not shown in this image), the seal  5204  sealingly engages with the base  5112  on the outside of the orifice  5138  and no longer allows communication of liquid or air into and out of the water reservoir  5110  through the orifice  5138 . Similarly the seal  5204  would engage with the base  5112  to surround the edges of the sloped profile preventing communication of liquid or air into and out of the water reservoir  5110  through the sloped profile  5139 . In some arrangements the seal  5204  may be integrated with the variable portion  5116  as described above. Alternatively the seal  5204  may be a separate seal that may be used in a reservoir with or without a variable portion. 
     According to another aspect of the present invention, an overfill prevention feature may be configured to prevent overfilling when a user is attempting to fill the reservoir  5110  while in its closed configuration. 
     In one form (shown in  FIG. 60  without the reservoir base  5112 ), the overfill prevention feature may form one or more air locks to prevent further ingress of liquid into the reservoir  5110  when the predetermined maximum volume of liquid is in the reservoir  5110 . In this form, when filling the reservoir  5110  in its closed configuration, the one or more air locks would form an enclosure of gas in the reservoir  5110  that is not displaced by the volume of liquid in the reservoir  5110 . In an example shown in  FIG. 60 , the reservoir  5110  is in an orientation such that the normal to the inlet  5118  and the outlet  5122  are oriented vertically, as a user would orient the reservoir  5110  while filling it with water. The water level  5184  would rise, and reach the level shown on  FIG. 60 , whereupon the remaining volume of gas in the reservoir  5110  is no longer able to access the inlet tube  5124  or the outlet tube  5126 , therefore would no longer be able to escape from the reservoir  5110 . The reservoir  5110  would thus not be able to receive any further volume of water into its interior volume. 
     Preferably, the volume of water in the reservoir  5110  when any further ingress of water into the reservoir  5110  is prevented by formation of the one or more air locks is substantially equal to the predetermined maximum volume of liquid to be retained in the reservoir  5110 . In some cases, the reservoir  5110  may allow further filling of the inlet tube  5124  and/or the outlet tube  5126  although further ingress of water into the interior volume is prevented by the air locks. In such cases, the volume of liquid in the reservoir  5110  when the air locks are formed, as well as the volume of the inlet tube  5124  and/or the outlet tube  5126  may be configured so that when added together, they are substantially equal to the predetermined maximum volume of liquid to be retained in the reservoir  5110 . 
     In some cases, for example where the normal to the inlet  5118  and the outlet  5122  may not be parallel, a user may fill the reservoir  5110  in one of a multiple orientations while closed. In such cases, the reservoir  5110  may be configured such that the appropriate air locks are formable at one of, or a plurality of the multiple orientations. The air locks need not be formed solely by occlusion of the inlet tube  5124  and/or the outlet tube  5126 . In some forms (not shown), one or more air locks may be formed by occlusion of any cavities or ports which may allow fluid communication between the interior and the exterior of the reservoir  5110 . Furthermore, the occlusion need not be performed by the volume of liquid in the reservoir  5110 . In some forms, the volume of liquid, as it is increased, may deform or move another component to form a seal (and thus an air lock) in the reservoir. 
     5.5.2.11 Retaining Clip 
     The reservoir lid  5114  may include a feature by which the water reservoir  5110  is to be retained in the water reservoir dock  5130  once the two members are engaged with each other. In one arrangement a retaining feature may be a protrusion, or a clip,  5142  on the reservoir lid  5114  as shown in  FIGS. 43-44 .  FIGS. 43-44  show a water reservoir  5110  and the reservoir dock  5130 . Here, a protrusion, or a clip,  5142  on the reservoir lid  5114  removably engages with a corresponding dock locking recess  5144  in the water reservoir dock  5130  when the water reservoir  5110  is inserted into the water reservoir dock  5130 . This connection secures the water reservoir  5110  relative to the water reservoir dock  5130 . 
     As described above the variable portion  5116  of the reservoir is compressed to enable insertion of the reservoir into the dock  5130 . The compression of the variable portion  5116  allows a portion of the reservoir  5110  to slide into the dock  5130  and allows the protrusion or clip  5142  to slide initially under the outer edge surface of the dock  5130  to reach the dock locking recess  5144 . The compression force applied to the reservoir for insertion may then be released to allow the protrusion or clip  5142  to engage with the dock locking recess  5144  and securing of the reservoir  5110  within the dock  5130 . When the reservoir  5110  is secured within the dock  5130  the variable portion  5116  is no longer in or in a reduced compressed state. Similarly, in order to be able to remove the water reservoir  5110  from the water reservoir dock  5130 , the variable portion  5116  must be compressed as to disengage the lid retention protrusion  5142  from the dock locking recess  5144 . 
     The retention protrusion  5142  may be further configured with a taper as shown in  FIG. 44 . The taper may be directed to increase in height away from the direction of insertion, to increase the amount of interference between the retention protrusion  5142  and the dock  5130  progressively during insertion. It would be clear to those skilled in the art that in an alternative arrangement the lid retention protrusion  5142  may be a recess, and the dock locking recess  5144  may be a corresponding protrusion. Alternatively one of any number of retaining features that are known in the art may be used to achieve the same outcomes as described above. 
     5.5.2.12 Water Reservoir-to-Humidifier Connection 
     In one form, the water reservoir  5110  in use receives a flow of air output by the RPT device  4000  at the dock outlet  4132 . The water reservoir  5110  is removably coupled with the humidifier  5000 , for example configured (as shown in  FIGS. 16 g -16 h   ) to be insertable into the dock  4130 . When the water reservoir  5110  is engaged with the dock  4130 , the reservoir inlet  5118  may receive the flow of air output by the RPT device  4000 , and direct the flow of air into the water reservoir  5110 . Humidity (i.e. water vapour) is added to the flow of air as the air travels through the reservoir  5110 , and the humidified flow of air exits the reservoir  5110  through the reservoir outlet tube  5126  and to the reservoir outlet  5122 . The reservoir outlet  5122  is connectable to an air circuit  4170  to deliver the flow of humidified air to the patient  1000 . 
     The double-ended arrows in  FIG. 16 h    show the direction of relative motion, i.e. generally horizontal movement, between the humidifier  5000  and the water reservoir  5110  in connection and disconnection with each other in this arrangement. In the arrangement shown in  FIGS. 16 g -16 h   , the water reservoir  5110  is connected with the humidifier  5000  by placing the water reservoir  5110  in the dock  4130 . In this arrangement, the heights and shapes of the cavity in the dock  4130  and the water reservoir  5110  are such that to engage the water reservoir  5110  with the dock  4130  the compliant portion  5116  is compressed, for example by between about 1 mm and about 5 mm, for example by about 2 mm, about 3 mm or about 4 mm. Thus, the shape of the portion of the water reservoir  5110  that is inserted into the dock  4130  is complementary to the shape of the dock cavity  5160  and the height of the water reservoir  5110  when compliant portion  5116  is compressed is slightly less than the height of the dock cavity  5160  to enable the insertion of the water reservoir  5110  into the dock cavity  5160 . 
     In one form, a compressive force is required to sufficiently compress the compliant portion  5116  and allow relative movement (i.e. sliding) between the water reservoir  5110  and the dock  4130 . For example a compression force as measured at the handle recesses  5154 ,  5156  of between about 10 N and about 30 N, or about 20 N, or some other compression force is required to allow insertion of the water reservoir  5110  into the dock  4130 . The vertical gap achieved between the water reservoir  5110  and the cavity of the dock  4130  during insertion (or removal) may be between about 1 mm and about 5 mm, for example about 2 mm, 3 mm or 4 mm, when this compressive force is applied at the handle recesses  5154 ,  5156  and the water reservoir  5110  is inserted into the dock  4130 . The water reservoir  5110  and the dock  4130  may be arranged so that the amount of compression in the compliant portion  5116  is reduced once the water reservoir  5110  is connected with the dock  4130  and the patient  1000  is no longer applying a compressive force. The reduction in compression may be between about 0.5 mm and about 2.5 mm, for example about 1 mm, 1.5 mm or 2 mm. 
     In the illustrated arrangement (see  FIGS. 16 a -16 b   ) the reservoir outlet  5122  is connectable to the dock inlet  4134 , through which the humidified flow of air travels to the humidifier outlet  5172 . The humidifier outlet  5172  is connectable to the air circuit  4170  as indicated in  FIG. 13  by the double-ended dotted arrow (see  FIG. 13 ). An advantage of such an arrangement is that the water reservoir  5110  can be removed from the dock  4130  while the air circuit  4170  remains attached to the device outlet  4004 . Thus the insertion and removal of the water reservoir  5110  is independent of the connection of the air circuit  4170 . A further advantage is that the water reservoir  5110  must be removed from the dock  4130  to fill the water reservoir  5110  with liquid. In this form, neither of the inlet  5118  and the outlet  5122  of the reservoir  5110  are exposed while the reservoir  5110  is inserted in the humidifier  5000  in an operating configuration, while the reservoir  5110  itself remains accessible to the patient  1000 , for example to allow easy removal from the humidifier  5000 . This arrangement may reduce the likelihood of the user over-filling the water reservoir  5110  over the predetermined, maximum volume of liquid, as the water reservoir  5110  incorporates features to prevent over-filling. Still further, as the user is encouraged to remove the water reservoir  5110  to fill the reservoir  5110  with liquid, the likelihood of spillage of water onto, or into, the humidifier  5000  and/or the RPT device  4000  is reduced. 
     The compliant portion  5116  may be constructed from an elastomeric material such as silicone, thermoplastic elastomer (TPE), TPE polyester, TPE polyurethane or natural rubber. In choosing the material to be used for the compliant portion  5116  it may be advantageous to choose one that does not experience mechanical relaxation across the range of storage and operational temperatures that the compliant portion  5116  may be exposed to. One example of a material for the compliant portion  5116  which meets these requirements may be silicone. 
     A reservoir latch  5186  may be provided on the water reservoir  5110 , as shown in  FIG. 40 , so that when the reservoir latch  5186  is engaged, it secures the reservoir lid  5114  and reservoir base  5112  together. The latch  5186  may prevent the reservoir lid  5114  and the reservoir base  5112  from separating and maintain the compliant portion  5116  in sealing engagement between the lid  5114  and the base  5112 , for example by compression. In one form, the latch  5186  may be configured to restrict relative movement of the lid  5114  in relation to the base  5112  in one direction only, thus allow further compression of the compliant portion  5116  while preventing separation of the lid  5114  and the base  5112 . This may allow insertion of the water reservoir  5110  into the dock  4130 , and/or allow the compliant portion  5116  to assist thermal engagement between the reservoir  5110  and the heating element  5240  as described elsewhere in this disclosure. 
     When in use, the water reservoir  5110  receives the flow of breathable air for example output by the PAP device  4000 . In one form, the water reservoir  5110  is removably coupled with the humidifier  5000  as shown in  FIG. 24-27  by inserting the water reservoir into the water reservoir dock  5130 , for example by sliding. The inlet  5118  of the water reservoir  5110  is configured to receive the flow of breathable gas that is output by the PAP device  4000 , and to direct the flow of breathable gas into the water reservoir  5110 . Humidity (i.e. water vapour) is added to the flow of breathable gas as the breathable gas travels through the reservoir  5110 , and the humidified flow of breathable gas exits the reservoir  5110  through the outlet tube  5126  and to the reservoir outlet  5122 . The reservoir outlet  5122  is connectable to an air circuit  4170  to deliver the flow of humidified breathable gas to the patient  1000 . 
     The double-ended arrows in  FIG. 25  and  FIG. 27  show the direction of relative motion, i.e. generally horizontal movement, between the humidifier  5000  and the water reservoir  5110  in connection and disconnection with each other in this arrangement. However, the water reservoir  5110  may be coupled to the humidifier  5000  by other methods such as insertion in a generally vertical direction, connection by one or more intermediate components (e.g. tubes) or being integrally formed with a humidifier. 
     In an alternative arrangement, not shown, the water reservoir  5110 , may be inserted into the dock cavity  5160  from a vertical direction rather than using a sliding motion. In such an arrangement the dock cavity of the humidifier  5000  may comprise a moveable cover portion, such as a lid or top portion, which is at least partially opened to allow insertion of the water reservoir  5110  and closed following insertion to secure the water reservoir  5110  within the dock cavity  5160 . 
     In the illustrated arrangement (see  FIG. 27 ) the reservoir outlet  5122  is connectable to the reservoir dock gas inlet  5170 , through which the humidified flow of breathable air travels to the humidifier outlet  5172 . The humidifier outlet  5172  is connectable to the air delivery circuit or air circuit  4170  as indicated in  FIG. 13  by the double-ended dotted arrow (see  FIG. 24 ). One advantage of such an arrangement is that the humidifier reservoir  5110  must be removed from the reservoir dock  5130  to fill the humidifier reservoir  5110  with liquid. This arrangement generally prevents access to any openings in the humidifier reservoir  5110  while it is connected to the humidifier  5000 , and may reduce the likelihood of the user over-filling the water reservoir  5110  over the given, maximum volume of liquid, as the humidifier reservoir  5110  incorporates features to prevent over-filling as described further below. Still further, as the user is encouraged to remove the water reservoir  5110  to fill the reservoir  5110  with liquid, the likelihood of spillage of water onto, or into, the humidifier  5000  and/or the PAP device  4000  is reduced. 
     As shown in  FIG. 27 , first and second dock seals  5132 ,  5134  may be provided to help seal the connection between the reservoir inlet  5118  and the dock  5130  and the connection between the reservoir outlet  5122  and the dock  5130 . 
     In the arrangement shown in  FIG. 26-27 , the water reservoir  5110  is connected with the humidifier  5000  by placing the water reservoir  5110  in the water reservoir dock  5130 . In this arrangement, the heights and shapes of the dock internal cavity  5160  and the water reservoir  5110  are such that to engage the water reservoir  5110  with the water reservoir dock  5130  the variable portion  5116  is compressed, for example by between about 1 mm and about 5 mm, for example by about 2 mm, about 3 mm or about 4 mm. Thus, the shape of the portion of the water reservoir  5110  that is inserted into the dock  5130  is complementary to the shape of the dock cavity  5160  and the height of the water reservoir  5110  when variable portion  5116  is compressed is slightly less than the height of the dock cavity  5160  to enable the insertion of the water reservoir  5110  into the dock cavity  5160 . 
     The variable portion  5116  may be constructed with a cross-section shape such as one shown in  FIG. 50 . A compressive force is required to sufficiently compress the variable portion  5116  and allow relative movement (i.e. sliding) between the water reservoir  5110  and the water reservoir dock  5130 . For example a compression force as measured at the handle recesses  5154 ,  5156  of between about 10 N and about 30 N, or about 20 N, or some other compression force is required to allow insertion of the water reservoir  5110  into the dock cavity  5160 . The vertical gap achieved between the water reservoir  5110  and the dock internal cavity  5160  during insertion (or removal) may be between about 1 mm and about 5 mm, for example about 2 mm, 3 mm or 4 mm, when this compressive force is applied at the handle recesses and the water reservoir  5110  is inserted into the reservoir dock  5130 . The water reservoir  5110  and the reservoir dock  5130  may be arranged so that the amount of compression in the variable portion  5116  is reduced once the water reservoir  5110  is connected with the reservoir dock  5130  and the patient  1000  is no longer applying a compressive force. The reduction in compression may be between about 0.5 mm and about 2.5 mm, for example about 1 mm, 1.5 mm or 2 mm. 
     The variable portion  5116  may be constructed from an elastomeric material such as silicone, TPE, TPE polyester, TPE polyurethane or natural rubber. In choosing the material to be used for the variable portion  5116  it may be advantageous to choose one that does not experience mechanical relaxation across the range of storage and operational temperatures that the variable portion  5116  may be exposed to. One example of a material for the variable portion  5116  which meets these requirements may be silicone. 
     A reservoir latch  5186  may be provided on the water reservoir  5110 , as shown in  FIG. 40 , so that when the reservoir latch  5186  is engaged, it secures the reservoir lid  5114  and reservoir base  5112  together. The latch  5186  may prevent the reservoir lid  5114  and the reservoir base  5112  from separating and maintain the variable portion  5116  in sealing engagement between the lid  5114  and the base  5112 , for example by compression. In one form, the latch  5186  may be configured to restrict relative movement of the lid  5114  in relation to the base  5112  in one direction only, thus allow further compression of the variable portion  5116  while preventing separation of the lid  5114  and the base  5112 . This may allow insertion of the water reservoir  5110  into the reservoir dock  5130 , and/or allow the variable portion  5116  to assist thermal engagement between the reservoir  5110  and the heater plate  5120  as described elsewhere in this disclosure. 
     5.5.2.12.1 Pre-Compression for Improved Thermal Contact 
     According to one aspect of this technology, the water reservoir  5110  and the heater plate  5120  of the humidifier are in thermal contact, or thermal engagement, as described above. A degree of thermal contact, for example measured in thermal conductivity or thermal contact resistance, between two components may vary according to a number of parameters. 
     In the prior art, additional components have been used to improve thermal contact between a water reservoir and a heater plate by increasing the contact pressure therebetween. One example is the use of spring elements, which are used to connect the heater plate to the humidifier body, as described in U.S. Pat. No. 4,203,027, thereby pushing the heater plate towards the water reservoir. Another example is a humidifier with a lid wherein a compressible elastomer seal is provided on the lid, as described in WO2010/031126. In this example, when the lid is in its closed position the seal engages against the water reservoir and pushes it against the heater plate. 
     In the present technology, pre-compression of the water reservoir  5110 , for example in engagement with the water reservoir dock  4130 , may be used to help improve thermal contact between the reservoir  5110  and the heating element  5240 . 
     In one arrangement, the water reservoir  5110  may be configured so that in its operating configuration, such as when it is placed in the water reservoir dock  41305130 , the compliant portion  5116  is compressed as described above. The reservoir  5110  and the reservoir dock  4130  may be further configured so that a reaction force to the compression of the compliant portion  5116  pushes the base  5112  of the water reservoir  5110  against the heating element  5240  to improve the thermal contact therebetween. 
     Thus, the compliant portion  5116  may act as a spring that is biased to push the reservoir base  5112  and/or the reservoir lid  5114  in a direction perpendicular to the heating element  5240 . As the reservoir  5110  is secured externally, such as confined within the reservoir dock  4130 , the compression of the compliant portion  5116  is reacted by a force that encourages improved thermal engagement with the heating element  5240 . 
     The force required for compression of the compliant portion  5116  when the water reservoir  5110  is connected with the humidifier  5000  is preferably in the same direction as the normal to a surface of the conductive portion. The direction may be also preferably in the same direction as the direction of thermal engagement. This force is reacted by the water reservoir dock  4130  at its contacting points and/or surfaces, thereby pushing the base  5112  of the water reservoir  5110  and the heating element  5240  together. 
     The magnitude of compression force may be between about 5 N and about 15 N when measured at the heating element  5240  when the water reservoir  5110  is placed in the water reservoir dock  4130 . However, it should be understood that different configurations of the water reservoir  5110  may require different magnitudes of compression force. The magnitude of this force may be altered by modifying the design of any or all of the compliant portion  5116 , the lid  5114 , the base  5112 , or the reservoir dock  4130 . For instance, if the compliant portion  5116  was constructed of a material with higher Young&#39;s modulus, it would correspondingly increase the magnitude of the force. It should be noted that  FIG. 20  only shows forces and pressures in the vertical direction. 
     In some cases, the amount of compression of the compliant portion  5116  in the reservoir  5110  may be used to vary a level of thermal engagement between the conductive portion and the heating element  5240 . 
     5.5.2.13 Conductive Portion  5120   
     According to one arrangement, the reservoir  5110  comprises a conductive portion  5120  configured to allow efficient transfer of heat from the heating element  5240  to the volume of liquid in the reservoir  5110 . In one form, the conductive portion  5120  may be arranged as a plate, although other shapes may also be suitable. All or a part of the conductive portion  5120  may be made of a thermally conductive material such as aluminium (e.g. approximately 2 mm thick, such as 1 mm, 1.5 mm, 2.5 mm or 3 mm), another heat conducting metal or some plastics. In some cases, suitable heat conductivity may be achieved with less conductive materials of suitable geometry. 
     5.5.2.13.1 Thermal Contact/Engagement 
     According to one aspect of this technology, the water reservoir  5110  and the heater plate  5120  of the humidifier are in thermal contact, or thermal engagement, as described above. A degree of thermal contact, for example measured in thermal conductivity or thermal contact resistance, between two components may vary according to a number of parameters. 
     In the prior art, additional components have been used to improve thermal contact between a water reservoir and a heater plate by increasing the contact pressure therebetween. One example is the use of spring elements, which are used to connect the heater plate to the humidifier body, as described in U.S. Pat. No. 4,203,027, thereby pushing the heater plate towards the water reservoir. Another example is a humidifier with a lid wherein a compressible elastomer seal is provided on the lid, as described in WO2010/031126. In this example, when the lid is in its closed position the seal engages against the water reservoir and pushes it against the heater plate. 
     5.5.2.13.1.1 Use of Pressurised Gas for Improved Thermal Contact 
     According to another aspect, when the water reservoir  5110  is connected with the humidifier  5000 , the flow of breathable gas received from the PAP device may pressurise a chamber such as the interior of the reservoir  5110 . The pressurisation of the chamber may be used to increase a level of thermal engagement (i.e. thermal contact) between the reservoir  5110  and the heater plate  5120 . The reservoir  5110  may be further configured so that by varying the level of pressure in the chamber may vary the level of thermal contact between the reservoir  5110  and the heater plate  5120 . 
     In one form, the variable portion  5116  may be configured to be expandable in the direction of thermal contact, and the reservoir  5110  may be confined by the reservoir dock  5130  in the same direction. In this form, the internal pressure pushes the base  5112  of the water reservoir  5110  against the heater plate  5120  to improve the level of thermal engagement between the heater plate  5120  and the base  5112 . 
       FIG. 32  illustrates this effect by indicating the distributed forces or pressures that are applied to the lid  5114  and the base  5112  by the arrows shown.  FIG. 32  shows forces and pressures in the vertical direction only, as in this form the thermal engagement occurs in the vertical direction. The presence of above-atmospheric pressure within the water reservoir  5110  results in forces in the direction of thermal engagement, and is reacted by the water reservoir dock  5130  at its contacting surfaces, thereby pushing the base  5112  of the water reservoir  5110  and the heater plate  5120  towards each other in the direction of thermal engagement. The magnitude of this force may be between about 5 N and about 15 N when measured at the heater plate  5120  at 20 cm H 2 O of pressure. 
     It should be understood that different configurations of the water reservoir  5110  may require different magnitudes of force, which may be achieved by varying the surface area that the pressure acts on, or the effective pressure that acts on the surface. Such changes may be achieved, for example, by a pressure regulating valve. 
     In another arrangement, substantially the same effects as those described above may be achieved with a non-opening variable portion of a water reservoir  5110 . The water reservoir  5110  and the reservoir dock  5130  may be arranged so that elasticity or flexibility is provided by an elastomeric material or a joint that allows freedom of movement (e.g. a sliding connection, or a concertina section of pliable plastic or a flexible portion in the water reservoir) in the direction of the heat transfer. In this configuration the lid  5114  and the base  5112  may be unconstrained relative to each other in the direction of thermal contact. The reservoir  5110  may then be constrained in the direction of the heat transfer in another manner (e.g. by a water reservoir dock or a similar housing) to create a force that reacts to balance the pressure created in the interior of the reservoir  5110  by the pressurized flow of breathable air, wherein some of the reaction force may occur at the heater plate  5120  to improve thermal contact. In such arrangements, another opening to re-fill the water reservoir  5110  may be introduced on the reservoir  5110 , such as on the lid  5114 , and it may comprise a separate seal. 
       FIG. 45  shows an example of such an arrangement, including a base  5174 , a top  5176 , a variable portion  5178  and a re-filling cap  5180 . The base, the top and the variable portion may be affixed together in another arrangement, wherein re-filling of the reservoir would be accommodated by the re-filling cap,  5180 . The re-filling cap  5180  may be placed such that when the humidifier reservoir  5110  is engaged with the reservoir dock  5130  the re-filling cap  5180  is not accessible. Such an arrangement may preserve the advantage described above, namely that the reservoir  5110  is not able to be re-filled while it is engaged with the reservoir dock  5130 . Furthermore, the variable portion  5178  may be replaced by any mechanism known in the art that is able to accommodate a change in vertical length within a reservoir. 
     In a yet another alternate arrangement, the flow of breathable air may be used to improve the level of thermal contact between the humidifier reservoir  5110  and the heater plate  5120  by pressurisation or inflation of a secondary component. The secondary component may be a chamber, body or surface that acts on the humidifier reservoir  5110 , which in turn pushes the water reservoir  5110  and the heater plate  5120  together in the direction of thermal engagement. Similarly, the secondary component may act upon the heater plate  5120  to push the heater plate  5120  and water reservoir  5110  together in the direction of thermal engagement. 
     The secondary component may be arranged externally to the reservoir  5110  and/or the heater plate  5120 . Furthermore, the secondary component may be configured to vary the area in contact with the reservoir  5110  and/or the heater plate  5120 , to further profile the change to thermal contact as pressure of the flow of breathable gas changes. 
     In an alternate arrangement, the water reservoir dock  5130  may include a retaining mechanism (for example, a lid that closes around the water reservoir  5110 ) to hold the water reservoir  5110  in its intended position. In such an arrangement, a reservoir dock lid may be configured to compress and/or confine the variable portion  5116  in order to improve the level of thermal contact. 
     The level of thermal contact may also be further improved using a spring loaded or sprung heater plate as is known in the prior art. The heater plate may be constructed with a convex or domed shape towards the humidifier reservoir  5110  so that when the humidifier  5110  is engaged with the reservoir dock  5130  the convex heater plate is flattened, which generates a clamping force pushing the heater plate  5120  to the water reservoir  5110 . Similarly, the conductor plate  5152  of the water reservoir  5110  may be domed or convex shaped and be configured to be flattened towards to the heater plate when the water reservoir  5110  is engaged in the dock cavity  5160  of the humidifier  5000 . 
     Any one of the above means of improving thermal contact may be used independently of each other, or in any combination thereof, including in combination with any prior art means of achieving or improving thermal engagement between the humidifier reservoir and the heater plate. 
     5.5.2.14 Humidifier Transducer(s)  5210   
     The humidifier  5000  may comprise one or more humidifier transducers (sensors)  5210  instead of, or in addition to, transducers  4270  described above. Humidifier transducers  5210  may include one or more of an air pressure sensor, an air flow sensor, a temperature sensor or a humidity sensor as shown in  FIG. 5 c   . A humidifier transducer  5210  may produce one or more output signals which may be communicated to a controller such as the central controller  4230  or the humidifier controller  5250 . In some forms, a humidifier transducer may be located externally to the humidifier  5000  (such as in the air circuit  4170 ) while communicating the output signal to the controller. 
     5.5.2.14.1 Pressure Transducer  5212   
     One or more pressure transducers  5212  may be provided to the humidifier  5000  in addition to, or instead of, a pressure transducer  4272  provided in the RPT device  4000 . 
     5.5.2.14.2 Flow Transducer  5214   
     One or more flow transducers  5214  may be provided to the humidifier  5000  in addition to, or instead of, a flow transducer  4274  provided in the RPT device  4000 . 
     5.5.2.14.3 Temperature Transducer  5216   
     The humidifier  5000  may comprise one or more temperature transducers  5216 . The one or more temperature transducers  5216  may be configured to measure one or more temperatures such as of the heating element  5240  or of the flow of air downstream of the water reservoir outlet  5122 . In some forms, the humidifier  5000  may further comprise a temperature sensor  5216  to detect the temperature of the ambient air. 
     5.5.2.14.4 Humidity Transducer  5218   
     In one form, the humidifier  5000  may comprise one or more humidity sensors  5218  to detect a humidity of a gas, such as the ambient air. The humidity sensor  5218  may be placed towards an outlet of the humidifier  5000  in some forms to measure a humidity of the gas delivered from the humidifier  5000 . The humidity sensor may be an absolute humidity sensor or a relative humidity sensor. 
     5.5.2.15 Heating Element  5240   
     A heating element  5240  may be provided to the humidifier  5000  in some cases to provide a heat input to one or more of the volume of water in the water reservoir  5110  or to the flow of air. The heating element  5240  may comprise a heat generating component  5242  (see  FIG. 17 b   ) such as an electrically resistive heating track. One suitable example of a heating element  5240  is a layered heating element such as one described in the PCT Patent Application Publication Number WO 2012/171072, the entire document of which is incorporated herewithin by reference. 
     In some forms, the heating element  5240  may be provided in the chassis  4016  where heat may be provided to the water reservoir  5110  primarily by conduction, for example through a HE cover plate  5241  (see  FIG. 17 b   ) which may be composed of a conductive material such as a metal (e.g. stainless steel or aluminium).) 
     The heating element  5240  may be supported by a HE seal  5243  as shown in  FIG. 17 b   , configured to prevent or discourage ingress of any water from the water reservoir  5110  or the dock  4130  into the heating element  5240 . In one form, the HE seal  5243  (shown in greater detail in  FIGS. 17 g -17 h   ) may seal around the periphery of the heating element  5240 , and elevate the heating element  5240  from the base of the RPT device  4000 . The HE seal  5243  may comprise one or more resilient portions such as the HE cones  5245  as shown in  FIGS. 17 d  and 17 h   , configured to provide a compressive force to help engage the heating element  5240  with the conductive portion  5120  of the water reservoir  5110 . In one form, the HE seal  5243  and the heating element  5240  may be configured so that when the water reservoir  5110  is inserted into and engaged with the dock  4130 , the HE cones  5245  are compressed axially to provide an upward force, thereby pushing the heating element  5240  toward the conductive portion  5120  of the water reservoir  5110  and improving the thermal contact therebetween. 
     The HE seal  5243  may further comprise one or more HE cable ports  5246  to allow a cable (e.g. for electrical power) to travel therethrough, for example from another portion of the chassis  4016  such as outside of the dock  4130  and near the pneumatic block  4020 . The one or more HE cable ports  5246  may sealingly engage around a periphery of the cable travelling therethrough to prevent ingress of water into the heating element  5240 . In one form, the HE seal  5243  may be constructed from a resilient material such as silicone, and comprise integrally formed HE cones  5245  and HE cable ports  5246 . The HE cable port  5246  may comprise a cavity for the cable to travel therethrough, and may be configured to engage with another cavity for location and/or retention, such as by being shaped as a protrusion to be inserted into a cavity in the chassis  4016 . 
     The humidifier  5000  may comprise a HE base cover  5244  as shown in  FIG. 17 b    and in further detail in  FIGS. 17 i  and 17 j   . The HE base cover  5244  may be removably coupled to the chassis  4016  (e.g. by screws) to allow access to the heating element  5240 , and comprise one or more features configured to support and locate the HE seal  5243 . In one form, the HE base cover  5244  may further comprise HE cone slots  52475246  configured to receive HE cones  5245  while allowing a compression thereof. 
     5.5.2.15.1 Humidifier Controller  5250   
     According to one arrangement of the present technology, a humidifier  5000  may comprise a humidifier controller  5250  as shown in  FIG. 5 c   . In one form, the humidifier controller  5250  may be a part of the central controller  4230 . In another form, the humidifier controller  5250  may be a separate controller, which may be in communication with the central controller  4230 . 
     In one form, the humidifier controller  5250  may receive as inputs measures of characteristics (such as temperature, humidity, pressure or flow rate), for example of the flow of air, the water in the reservoir  5110  or the humidifier  5000 . The humidifier controller  5250  may also be configured to execute or implement humidifier algorithms or deliver one or more output signals. 
     As shown in  FIG. 5 c   , the humidifier controller may comprise one or more controllers, such as a central humidifier controller  5251 , a heated air circuit controller  5254  configured to control the temperature of a heated air circuit or a heating element controller  5252  configured to control the temperature of a hot plate. 
     5.6 Glossary 
     For the purposes of the present technology disclosure, in certain forms of the present technology, one or more of the following definitions may apply. In other forms of the present technology, alternative definitions may apply. 
     5.6.1 General 
     Air: In certain forms of the present technology, air may be taken to mean atmospheric air, and in other forms of the present technology air may be taken to mean some other combination of breathable gases, e.g. atmospheric air enriched with oxygen. 
     Ambient: In certain forms of the present technology, the term ambient will be taken to mean (i) external of the treatment system or patient, and (ii) immediately surrounding the treatment system or patient. 
     For example, ambient humidity with respect to a humidifier may be the humidity of air immediately surrounding the humidifier, e.g. the humidity in the room where a patient is sleeping. Such ambient humidity may be different to the humidity outside the room where a patient is sleeping. 
     In another example, ambient pressure may be the pressure immediately surrounding or external to the body. 
     In certain forms, ambient (e.g. acoustic) noise may be considered to be the background noise level in the room where a patient is located, other than for example, noise generated by an RPT device or emanating from a mask or patient interface. Ambient noise may be generated by sources outside the room. 
     Continuous Positive Airway Pressure (CPAP): CPAP treatment will be taken to mean the application of a supply of air to the entrance to the airways at a pressure that is continuously positive with respect to atmosphere, and preferably 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. 
     CDMA: is an abbreviation for Code division multiple access. 
     GSM: is an abbreviation for Global System for Mobile. 
     LTE: is an abbreviation for Long Term Evolution. 
     USB: is an abbreviation for Universal Serial Bus. 
     5.6.2 Materials 
     Silicone or Silicone Elastomer: A synthetic rubber. In this specification, a reference to silicone is a reference to liquid silicone rubber (LSR) or a compression moulded silicone rubber (CMSR). One form of commercially available LSR is SILASTIC (included in the range of products sold under this trademark), manufactured by Dow Corning. Another manufacturer of LSR is Wacker. Unless otherwise specified to the contrary, a preferred form of LSR has a Shore A (or Type A) indentation hardness in the range of about 35 to about 45 as measured using ASTM D2240. 
     Polycarbonate: a typically transparent thermoplastic polymer of Bisphenol-A Carbonate. 
     5.7 Other Remarks 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     Unless the context clearly dictates otherwise and where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit, between the upper and lower limit of that range, and any other stated or intervening value in that stated range is encompassed within the technology. The upper and lower limits of these intervening ranges, which may be independently included in the intervening ranges, are also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the technology. 
     Furthermore, where a value or values are stated herein as being implemented as part of the technology, it is understood that such values may be approximated, unless otherwise stated, and such values may be utilized to any suitable significant digit to the extent that a practical technical implementation may permit or require it. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this technology belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present technology, a limited number of the exemplary methods and materials are described herein. 
     When a particular material is identified as being preferably used to construct a component, obvious alternative materials with similar properties may be used as a substitute. Furthermore, unless specified to the contrary, any and all components herein described are understood to be capable of being manufactured and, as such, may be manufactured together or separately. 
     It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include their plural equivalents, unless the context clearly dictates otherwise. 
     All publications mentioned herein are incorporated by reference to disclose and describe the methods, materials (or both) 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. 
     Moreover, in interpreting the disclosure, all terms should be interpreted in the broadest reasonable manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. 
     The subject headings used in the detailed description are included only for the ease of reference of the reader and should not be used to limit the subject matter found throughout the disclosure or the claims. The subject headings should not be used in construing the scope of the claims or the claim limitations. 
     Although the technology herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the technology. In some instances, the terminology and symbols may imply specific details that are not required to practice the technology. For example, although the terms “first” and “second” may be used, unless otherwise specified, they are not intended to indicate any order but may be utilised to distinguish between distinct elements. Furthermore, although process steps in the methodologies may be described or illustrated in an order, such an ordering is not required. Those skilled in the art will recognize that such ordering may be modified. Additionally, or alternatively, aspects thereof may be conducted concurrently or even synchronously. 
     It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the technology. 
     
       
         
           
               
            
               
                   
               
               
                 5.8 REFERENCE SIGNS LIST 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 Reference 
               
               
                   
                   
               
               
                   
                 patient 
                 1000 
               
               
                   
                 bed partner 
                 1100 
               
               
                   
                 patient interface 
                 3000 
               
               
                   
                 seal-forming structure 
                 3100 
               
               
                   
                 plenum chamber 
                 3200 
               
               
                   
                 structure 
                 3300 
               
               
                   
                 connection port 
                 3600 
               
               
                   
                 rpt device 
                 4000 
               
               
                   
                 rpt device inlet 
                 4002 
               
               
                   
                 rpt device outlet 
                 4004 
               
               
                   
                 outlet tube 
                 4006 
               
               
                   
                 first portion 
                 4006a 
               
               
                   
                 second portion 
                 4006b 
               
               
                   
                 flange 
                 4006fl 
               
               
                   
                 outlet tube guide portion 
                 4006gu 
               
               
                   
                 outlet tube latch portion 
                 4006la 
               
               
                   
                 outlet end 
                 4006oe 
               
               
                   
                 intermediate tube 
                 4008 
               
               
                   
                 external housing 
                 4010 
               
               
                   
                 front panel cutout 
                 4010co 
               
               
                   
                 external housing light port 
                 4010lp 
               
               
                   
                 protrusion 
                 4010pr 
               
               
                   
                 front panel 
                 4012 
               
               
                   
                 internal shoulder 
                 4012sh 
               
               
                   
                 side panel 
                 4014 
               
               
                   
                 access cover 
                 4014ac 
               
               
                   
                 access cover anchoring portion 
                 4014an 
               
               
                   
                 recess 
                 4014ch 
               
               
                   
                 cover portion 
                 4014co 
               
               
                   
                 connection port 
                 4014cp 
               
               
                   
                 side panel frame 
                 4014f 
               
               
                   
                 inlet air filter cover 
                 4014fc 
               
               
                   
                 air filter housing 
                 4014h 
               
               
                   
                 access cover hinge portion 
                 4014hi 
               
               
                   
                 complementary recess 
                 4014re 
               
               
                   
                 wall 
                 4014w 
               
               
                   
                 chassis 
                 4016 
               
               
                   
                 platform 
                 4016pl 
               
               
                   
                 pneumatic block 
                 4020 
               
               
                   
                 acoustic foam 
                 4020af 
               
               
                   
                 blower sleeve 
                 4020bs 
               
               
                   
                 first chamber 
                 4020c1 
               
               
                   
                 second chamber 
                 4020c2 
               
               
                   
                 flow plate 
                 4020fp 
               
               
                   
                 flow tube 
                 4020ft 
               
               
                   
                 first PB housing 
                 4020h1 
               
               
                   
                 second PB housing 
                 4020h2 
               
               
                   
                 pb inlet 
                 4020in 
               
               
                   
                 pb inlet tube 
                 4020it 
               
               
                   
                 pb outlet rim 
                 4020or 
               
               
                   
                 pb outlet 
                 4020ou 
               
               
                   
                 sleeve pull tab 
                 4020pt 
               
               
                   
                 pb sensor coupler 
                 4020sc 
               
               
                   
                 flow sensor port 
                 4020sp 
               
               
                   
                 sleeve tab 
                 4020st 
               
               
                   
                 pb water shield 
                 4020ws 
               
               
                   
                 pb water trap 
                 4020wt 
               
               
                   
                 patient interface connector 
                 4107 
               
               
                   
                 air filter 
                 4110 
               
               
                   
                 inlet air filter 
                 4112 
               
               
                   
                 outlet air filter 
                 4114 
               
               
                   
                 muffler 
                 4120 
               
               
                   
                 inlet muffler 
                 4122 
               
               
                   
                 outlet muffler 
                 4124 
               
               
                   
                 muffler body 
                 4124bo 
               
               
                   
                 muffler cap 
                 4124ca 
               
               
                   
                 muffler clip 
                 4124cl 
               
               
                   
                 muffler damper 
                 4124da 
               
               
                   
                 muffler expansion chamber 
                 4124ex 
               
               
                   
                 muffler foam 
                 4124fo 
               
               
                   
                 muffler hinge 
                 4124hi 
               
               
                   
                 muffler entry 
                 4124in 
               
               
                   
                 muffler lever 
                 4124le 
               
               
                   
                 muffler exit 
                 4124ou 
               
               
                   
                 muffler travel limiter 
                 4124tl 
               
               
                   
                 dock 
                 4130 
               
               
                   
                 corresponding dock guide portion 
                 4130gu 
               
               
                   
                 complementary recess 
                 4130re 
               
               
                   
                 dock outlet slot 
                 4130sl 
               
               
                   
                 dock outlet 
                 4132 
               
               
                   
                 dock outlet pressure port 
                 4132pp 
               
               
                   
                 dock inlet 
                 4134 
               
               
                   
                 pressure generator 
                 4140 
               
               
                   
                 blower 
                 4142 
               
               
                   
                 blower inlet 
                 4142in 
               
               
                   
                 blower outlet 
                 4142ou 
               
               
                   
                 motor 
                 4144 
               
               
                   
                 tab 
                 4148 
               
               
                   
                 back valve 
                 4160 
               
               
                   
                 air circuit 
                 4170 
               
               
                   
                 ac helical coil 
                 4170co 
               
               
                   
                 ac electrical connector 
                 4170ec 
               
               
                   
                 electrical lead 
                 4170le 
               
               
                   
                 ac outlet connector 
                 4170oc 
               
               
                   
                 ac overmould 
                 4170om 
               
               
                   
                 block 
                 4170pb 
               
               
                   
                 recess 
                 4170re 
               
               
                   
                 base seal 
                 4170se 
               
               
                   
                 ac tube portion 
                 4170tp 
               
               
                   
                 actuator 
                 4172 
               
               
                   
                 retention feature 
                 4174 
               
               
                   
                 AC tab 
                 4176 
               
               
                   
                 internal rib 
                 4177 
               
               
                   
                 travel stop 
                 4178 
               
               
                   
                 oxygen delivery port 
                 4180 
               
               
                   
                 user interface panel 
                 4190 
               
               
                   
                 ui base 
                 4190ba 
               
               
                   
                 light well 
                 4190lw 
               
               
                   
                 ui seal 
                 4190se 
               
               
                   
                 pcba 
                 4202 
               
               
                   
                 power supply 
                 4210 
               
               
                   
                 input device 
                 4220 
               
               
                   
                 first button 
                 4222 
               
               
                   
                 second button 
                 4224 
               
               
                   
                 dial 
                 4226 
               
               
                   
                 dial aperture 
                 4226ap 
               
               
                   
                 dial cover 
                 4226co 
               
               
                   
                 dial seal 
                 4226se 
               
               
                   
                 encoder shaft 
                 4226sh 
               
               
                   
                 central controller 
                 4230 
               
               
                   
                 clock 
                 4232 
               
               
                   
                 therapy device controller 
                 4240 
               
               
                   
                 protection circuit 
                 4250 
               
               
                   
                 memory 
                 4260 
               
               
                   
                 transducer 
                 4270 
               
               
                   
                 pressure transducer 
                 4272 
               
               
                   
                 flow transducer 
                 4274 
               
               
                   
                 motor speed transducer 
                 4276 
               
               
                   
                 ambient light sensor 
                 4278 
               
               
                   
                 data communication interface 
                 4280 
               
               
                   
                 antenna 
                 4280an 
               
               
                   
                 antenna ground plane 
                 4280gp 
               
               
                   
                 first side 
                 4280n1 
               
               
                   
                 second side 
                 4280n2 
               
               
                   
                 remote external communication network 
                 4282 
               
               
                   
                 local external communication network 
                 4284 
               
               
                   
                 remote external device 
                 4286 
               
               
                   
                 local external device 
                 4288 
               
               
                   
                 output device 
                 4290 
               
               
                   
                 display driver 
                 4292 
               
               
                   
                 display 
                 4294 
               
               
                   
                 display cover 
                 4294co 
               
               
                   
                 visual interface 
                 4295 
               
               
                   
                 report sub-menu 
                 4295a1 
               
               
                   
                 report sub-menu 
                 4295a2 
               
               
                   
                 report sub-menu 
                 4295a3 
               
               
                   
                 report sub-menu 
                 4295a4 
               
               
                   
                 report sub-menu 
                 4295a5 
               
               
                   
                 report sub-menu 
                 4295a6 
               
               
                   
                 report sub-menu 
                 4295a7 
               
               
                   
                 report sub-menu 
                 4295a8 
               
               
                   
                 report sub-menu 
                 4295b1 
               
               
                   
                 report sub-menu 
                 4295b2 
               
               
                   
                 report sub-menu 
                 4295b3 
               
               
                   
                 report sub-menu 
                 4295b4 
               
               
                   
                 first clinical menu screen 
                 4295c1 
               
               
                   
                 first menu screen 
                 4295m1 
               
               
                   
                 first clinical menu screen 
                 4295m2 
               
               
                   
                 selectable sub-menu 
                 4295o1 
               
               
                   
                 selectable sub-menu 
                 4295o2 
               
               
                   
                 report sub-menu 
                 4295r1 
               
               
                   
                 report sub-menu 
                 4295r2 
               
               
                   
                 report sub-menu 
                 4295r3 
               
               
                   
                 report sub-menu 
                 4295r4 
               
               
                   
                 report menu 
                 4295re 
               
               
                   
                 selectable sub-menu 
                 4295s1 
               
               
                   
                 selectable sub-menu 
                 4295s2 
               
               
                   
                 selectable sub-menu 
                 4295s3 
               
               
                   
                 selectable menu 
                 4295se 
               
               
                   
                 window portion 
                 4295w 
               
               
                   
                 control module 
                 4330 
               
               
                   
                 humidifier 
                 5000 
               
               
                   
                 outlet assembly 
                 5004 
               
               
                   
                 swivelling disc 
                 5050 
               
               
                   
                 swivel disc seal 
                 5051 
               
               
                   
                 electrical connector receiver 
                 5052 
               
               
                   
                 notch 
                 5054 
               
               
                   
                 outlet connection region 
                 5056 
               
               
                   
                 female electrical connector 
                 5058 
               
               
                   
                 receiver contact element 
                 5058ce 
               
               
                   
                 disc stop surface 
                 5060 
               
               
                   
                 disc stop surface 
                 5062 
               
               
                   
                 housing stop surface 
                 5064 
               
               
                   
                 housing stop surface 
                 5066 
               
               
                   
                 cable 
                 5070 
               
               
                   
                 cable housing 
                 5080 
               
               
                   
                 inner wall 
                 5082 
               
               
                   
                 outer wall 
                 5084 
               
               
                   
                 void 
                 5086 
               
               
                   
                 annular section 
                 5088 
               
               
                   
                 retainer 
                 5090 
               
               
                   
                 opening 
                 5092 
               
               
                   
                 housing tab 
                 5094 
               
               
                   
                 water reservoir 
                 5110 
               
               
                   
                 water reservoir base 
                 5112 
               
               
                   
                 water reservoir lid 
                 5114 
               
               
                   
                 compliant portion 
                 5116 
               
               
                   
                 water reservoir inlet 
                 5118 
               
               
                   
                 conductive portion 
                 5120 
               
               
                   
                 water reservoir outlet 
                 5122 
               
               
                   
                 plate 
                 5123 
               
               
                   
                 reservoir inlet tube 
                 5124 
               
               
                   
                 inlet cap 
                 5125 
               
               
                   
                 reservoir outlet tube 
                 5126 
               
               
                   
                 contact element 
                 5146 
               
               
                   
                 base conductor plate 
                 5152 
               
               
                   
                 handle recess 
                 5154 
               
               
                   
                 handle recess 
                 5156 
               
               
                   
                 hinge 
                 5158 
               
               
                   
                 complementary hinge recess portion 
                 5159 
               
               
                   
                 dock cavity 
                 5160 
               
               
                   
                 humidifier outlet 
                 5172 
               
               
                   
                 latch 
                 5186 
               
               
                   
                 intermediate portion 
                 5202 
               
               
                   
                 humidifier transducer 
                 5210 
               
               
                   
                 pressure transducer 
                 5212 
               
               
                   
                 flow transducer 
                 5214 
               
               
                   
                 temperature transducer 
                 5216 
               
               
                   
                 humidity transducer 
                 5218 
               
               
                   
                 heating element 
                 5240 
               
               
                   
                 he cover plate 
                 5241 
               
               
                   
                 heat generating component 
                 5242 
               
               
                   
                 he seal 
                 5243 
               
               
                   
                 he base cover 
                 5244 
               
               
                   
                 he cone 
                 5245 
               
               
                   
                 he cable port 
                 5246 
               
               
                   
                 he cone slot 
                 5247 
               
               
                   
                 humidifier controller 
                 5250 
               
               
                   
                 central humidifier controller 
                 5251 
               
               
                   
                 heating element controller 
                 5252 
               
               
                   
                 air circuit controller 
                 5254 
               
               
                   
                 humidifier end cap 
                 5300 
               
               
                   
                 magnet 
                 5340 
               
               
                   
                 end cap magnet holder 
                 5345