NZ757947B2 - Control for pressure of a patient interface - Google Patents

Abstract

method and/or apparatus to supply breathable gas at positive pressure to a patient through a patient interface. It can be undesirable for exhaled gas from a patient to be continuously vented to the ambient atmosphere and a vent valve may be used with a respiratory device, where the vent valve may selectively block fluid communication between components, such as the flow generator, the patient interface, and/or the vent. In such circumstances known methods of determining the gas pressure in the patient interface may not be accurate. In one form of the technology a controller uses one process for determining gas pressure in the interface when a conduit to a pressure sensor is blocked, and a second process when the conduit to the sensor is unblocked. An expiratory flow model may be used to determine an expiratory characteristic such as an expiratory flow rate or pressure in the patient interface where an indicative measure may not be available. The expiratory flow model may receive inputs based on a measure of the patient's respiration, such as the tidal volume, peak inspiratory flow rate or length of inspiration. The expiratory characteristic may be used by a controller to control a pressure in the patient interface to provide respiratory therapy to a patient at or close to a target pressure. selectively block fluid communication between components, such as the flow generator, the patient interface, and/or the vent. In such circumstances known methods of determining the gas pressure in the patient interface may not be accurate. In one form of the technology a controller uses one process for determining gas pressure in the interface when a conduit to a pressure sensor is blocked, and a second process when the conduit to the sensor is unblocked. An expiratory flow model may be used to determine an expiratory characteristic such as an expiratory flow rate or pressure in the patient interface where an indicative measure may not be available. The expiratory flow model may receive inputs based on a measure of the patient's respiration, such as the tidal volume, peak inspiratory flow rate or length of inspiration. The expiratory characteristic may be used by a controller to control a pressure in the patient interface to provide respiratory therapy to a patient at or close to a target pressure.

Description

WO 61848 CONTROL FOR PRESSURE OF A PATIENT INTERFACE 1 CROSS—REFERENCE TO RELATED APPLICATIONS {1] The present applieet‘lon claims priority from Australian Provisional. Patent Application Number AU 2013904199. filed on 30 Oct. 2013, the entire content of which is incorporated herewilhin by reference. 2 OUND OF THE TECHNOLOGY 2.1 FIELD OF THE TECHNOLOGY {2] The t technology relates to one or more of the detection, diagnosis, treatment. prevention and amelioration of respiratory—related disorders, and to procedures to prevent respiratory disorders. In particular, the present, technology relates to respiratory devices, and their use for ng respiratory disorders and for preventing respiratory disorders. 2.2 DESCRIPTION OF THE RELATED ART {3] The atory system of the body facilitates gas exchange. The nose and mouth form the entrance to the airways of a patient. {4] The airways include a series of branching tubes, which become narrower. shorter and more numerous as they ate deeper into the lung. ”,l‘he prime function of [the lung is gas ge. allowing oxygen to move from the air into the venous blood and carbon dioxide to more out. The trachea divides into right and left main bronchi, which further divide eventually into seminal bronchioles. The i make up the conducting airways. and do not take part in gas exchange. Fun’her divisions of the s lead to the respiratory hronchioles, and eventually to the elveoli. The 211 veolated region of the lung is where the gas exchange takes place, and is referred to as the respiratory zone. See West, Respiratory Physiology— the essentials. {5] A range of respiratory disorders exist. {45] Obstructive Sleep Apnea {GSA}, a form of Sleep Disordered Breathing (SIDE). is characterized by ion or obstruction of the upper air passage during sleep. It, results from a combination, of an abnormally small upper airway and the. {7] normal loss of muscle tone in the region of the , soft palate and posterior orophatyngeal wall during sleep. The condition causes the affeotod patient to stop breathing for periods lly of 30 to 120 seconds duration, mes 200 to 3042) times per night. It. often causes excessive daytime somnolence. and it may cause cardiovascular e and brain darlings. The me is a common disorder, pattioularly in mi ddlo aged overweight males: although a person affcctod may have no awareness of the. problem. See US Patent 4,944.3 l0 (Sullivan). {8] Choync—Stokcs Respiration (CSR) is a disorder of a patients atory controller in which there are rhythmic: alternating periotis of waxing and waning ventilation, causing repetitive gonation and reoxygenatiou 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 causcs servers sloop disruption, increased sympathetic: ty and increased nftcrload. See US Patent 959 (Berthonslones). {9] Obesity Hyperventilation Syndrome (0H8) is defined as the combination of severe obesity and awake chronic hypercapnia, in the absence of other known causes for li‘ypoventilation. Symptoms include dyspnea, morning headache and ive daytime sleepiness. {10} Chronic (lbstructive Pulmonary Disease (COED) encompasses any of a group of lower airway diseases that have certain oh aracteristics in common. These include increased resistance to air movement, extcndcd 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. ms i nclude: a on exertion, chronic cough and sputum production. {l ll Nem‘omuscular e {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 wheelchainbound. swallowing difficulties, respiratory muscle weakness anti. eventually, death from atory failure. Neuromuseular disorders can be divided into rapidly progressive and slowly progressive: (i) Rapidly progressive disorders: Chateeterised by muscle impairment that s over months and results in death within a few years. (Lag. Amyotrophie lateral sclerosis (ALS) and D‘uehenne 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 (eg. Limb girdle, Facioseapulohumeral and Myotonic muscular dystrophy). Symptems of respiratory failure in NMD include: sing generalised weakness, dysphagia. dyspnea on exertion and at rest, fatigue, sleepiness, morning headache, and difficulties with concentration and mood changes. {12} 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 'hypercapnie atory failure. Scoliosis nndfor 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 te. {l3} ise healthy duals may take advantage of systems and devices: to prevent atory disorders from arising. 2.3.1 Systems [14} One known product used for treating sleep disordered ing is the 39 Sleep y System, manufactured by ResMed. Ventilators such as the ResMed Stellm‘l‘M Series ofAdult' and Paediatric Ventilators may provide support for invasive and vasive pendent ventilation, for a range of patients for treating a number of conditions such as but not limited to NMD, OHS and COPE). ll 5} The ResMed Elisee't’M 150 ventilator and RcsMed VS IIITM ventilator may provide support for invasive and non—invasive ent ation 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. 2.2.2 Therapy til 6} Nasal Continuous Positive Airway Pressure (CPA?) therapy has been used to trout Obstructive Sloop Apnea (USA). The hypothesis is that uous positive airway pressure acts as a pneumatic splint and may prevent upper airway occlusion by pushing the soft palate and tongue d and away from. the posterior oropharyngeul wall. it 7] Nonwinvasivn ventiiaticm (NIV) provides ventilator support to a patient through the upper airways to unsist the t in taking :1qu breath and/or maintain nominate oxygen levels in the body The ventilator support is provided by a mask or nasal interface. N [V has been used to treat OHS, C()PD., MD and Chest Wall di sorders. ilS} Invasive ventilation (IV) provides ventilatory support to patients that are no longer able to effectively breathe thetnselvos and is pmvided using a tracheotomy tube. {19} Ventilators also l the timing and pressure of breaths pumped into the patient and monitor the breaths taken by the patient. The s of control and monitoring patients typically include vol.umo«cycled and pressureacycled methods.

The volume—cycled methods may include among othersl Pressure-Regulated Volume Control (PRVCL Volume Ventilation (VVL and Volume Controlled Continuous: Mandatory Ventilation tVC~CMV3 techniquen. The pi‘essnrewycled methods may in volve, among others, Assist Control (AC), Synchronized Intermittent ory Ventilation (SLIMVJ, Controlled Mechanical Ventilation (CMV), re Support Ventilation {PSV}, uous ve Airway Pressure (CPAP), or Positive End Expirutory Pressure (PEEP) tenhniquen. 2.2.3 Patient Interface {20} A patient interface may be used to intefiaco respiratory ent to its- wearer, for example by providing a flow of air to an ce to the uinvays. The [low of air may be provided Via a mask to the nose andior mouth, a tube to the mouth or u tracheostomy tube to tho trachea of a patient. Depending upon the therapy to be d, the patient interface may form a, seal, eg... with at region of the patient‘u face: to facilitate the. delivery of gas at n prensure at, sufficient variance with ambient pressure to el‘lieet therapy, e.g.. at a positive pressure of about it) coil-13C! relative to ambient pressure. For other forms of therapy. such as the delivery of , the patient interface may not include a seal sufficient to faeilitate delivery to the airways of a supply of gas at a positive pressure of about 10 cntllfil {21} The design of a patient interface presents a number of challenges. The face has a complex threedimensional shape. The size and shape of noses varies considerably n individuals. Since the head es 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 atory therapy. {2‘2} As a consequence of these challenges, some masks suffer from being one or more of obtrusive, aesthetically rable. 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. masks designed as part of personal protection equipment (eg. filter masks}, SCUBA masks. or for the administration of anaesthetics may be ble for their original ation, but nevertheless sueh masks may he undesirably uncomfortable to be worn for extended s 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. {2'3} CPAP therapy is highly effective to treat certain. respiratory disorders, provided patients comply with therapy. It a mask is uncomfortable, or difficult to use a t may not comply with therapy. Since it. is often ended that a patient regularly wash their mask. if a mask is difficult to clean (eg. difficult to assemble or disassemble). patients may not clean their mask and this may impact on, patient eomp’lianee. {‘24} While a mask for other applications (eg. aviators) may not be suitable for use in ng sleep disordered breathing, a mask designed for use in treating sleep disordered breathing may be suitable for other applications. {25} For these s. patient interfaces for delivery of CPA? during sleep form a distinct field. 2.2.3.1 Seal-forming portion {26} Patient interfaces may incinde a orming portion. Since it is in direct t with the patient’s face the shape and configuratinn 0f the seal—forming portion can have a direct impact the effectiveness and comfort of the patient interface. {27,} A patient interface may be partly characteiiised according to the design intent of where the sezil-fnnniiig portion is to engage with the face in use. In one form of patient interface, a seahforming pmtinn may cm‘nprise ‘twn subpnrtinns to engage with respective left and. ti ght mares. In one fnrm (if patient interface, a seat-fonning portion may comprise a single eietnent that surrounds hath nines in use. Such single element may be designed to for example Overlay an upper lip reginn and a nasal bridge rcginn (if a face. In nne form (if t. interface a sen'i.-t‘nrming portion may comprise an t that nds a mouth region in use, tag. by fanning a seal on a lower lip reginn of a face. In one farm (if patient interface, a scan—forming portion may comprise a single element, that surrounds both mare-s and a mouth region in use.

These different types nf'patient interfaces may be known by a y of names by their manufacturer including nasal masks, mil—face masks, nasal pilinws, nasal puffs 21nd ore—nasal masks. {28} A seal—forming n that may be effective in one region of a patient’ 5; face may be inappropriate in r rcginni eug bertause of the different shape, structure? ility and sensitivity t‘eginns of the patient‘s face. For e, a seal an swimming goggles that overlays a patient’s forehead may not be appropriate tn use on a patient’s nose. {29} Certain scat—forming pmtinns may be designed for mass manufacture such that one design fit and be comfortable and effective far a wide range of different face shapes and sizes. To the extent to which there is a mismatch between the shape of the patient‘s face, and the seal-forming pottinn of the msgas-manufactured patient interface-t one {31“ bath must adapt in order for a seat to form. {.30} One type of seal—twining portion extends z-n‘nund the ery of the t interface, and is intended to seal. against the user's- fa-ce when force is applind t0 the patient mterfnce with the seal—forming portion in cnnt‘mnting engagement with the user‘s face. The scalinrming portinn may incinde an air. or fluid filled cushinn, or WO 61848 a moulded or formed surface of a resilient seal element made of an elastomer such as a. rubber. With this type of seal-forming portion, if the fit is not te, there will be gaps between the seal—forming portion and the face. and additional force will be required to force the patient interface against the face in order to achieve a seal. {iii} Another type of orming portion ineo-rporatea a flap seal of thin material so positioned about the periphery of the maak no as to provide a selfasealing action against, the face oi" the user when ve pressure is applied within the mask.

Like the previous style of seal forming portion, if the match between the face and the mask is not good, additional force may be required to effect a seal. or the mask may leak. rmore, if the shape of the sealetomiing portion does not match that of the t, it may crease or buckle in use. giving rise to leaks. [32} Another form of orming portion may use adhesive to effect a seal.

Some patients may find it inconvenient to constantly apply and remove an adhesive to their face. {33} A range of patient interface seal—forming portion technologies are diaclosed in the following patent appiications, assigned to ResMeti Limited: W0 1 998/0049310; WC) 2006/074513; WO 201 0/1 351785. 2.2.3.2 Vent technologies {34] Some forms of t interface systems may include a vent to allow the washout of exhaled carbon dioxide. The vent: may allow a flow of gas from an interior space of the patient interface, e.g., the plenum chamber. to an exterior oi? the patient interface, e.g., to ambient. The vent may comprise an orifice and gas may flow through the orifice in use of the mask. Many such vents are noisy. Othere may become blocked in nae and thus provide insufficient washout. Some vents may be dismptive of the Sleep of a bed—partner 11.00 of the patient: 1000, eng through noise or foeusaed airflow. [35} ReSMed Limited. has developed a number of improved mask vent technologies. See ‘NCI 34,665; WU ZUUUIUTS.381; US 6.581.594; US Patent Application; US ZODQJDOSMSG; US Patent Application 2009/0044808. [36} Table ofnoise 0f prior masks ([50 17510—2flflfl‘7, N} cmfigf) pressure at Mask name Mask type A—weighied A-weighted Year (a ppmx.) mend pewer sound pressure level d’bA (le. (uncertain!y} (uncertainty) ResCme standard (*) ReSMed Mirage C") Rash/{ed UltraMimge ResMed Mirage Aetiva ResMed Mirage Micro ResMed Mirage SthGel ResMed Mirage FX Mirage Swift ("5) Mirage Swift 11 ResMed Mirage Swift: [37} ("‘3‘ one specimen iny, measured using test method specified in 1503744 in CPA}? mode at IOemHQO‘) {38,} Sound re values of a y of abjeets are listed below Aweighted sound pressure dbA (uncertainty) Vacuum Cleaner: Nilfisk , 1803744 at 1111 W‘aflter Broadly Litter Hog; B+ distance Grade Ccnversaticnal speech int distance Average home Quiet bedroom at night: 30 {39} Many prior art vents are of a. ‘centinuous’ type. That is, there vents are centinueusly in fluid communication with the flew generator and the patient interface allow for gas to flew therethrough regardless of therapy canditicn. in some cases, certain aspects 0f continuous vents may be undesirable. One is that typically? any gas exhausted from the patient: through the vent is ill sed humidity in ison to the ambient air This may lead to additional d1vine of the ts nasal passageways. or require additional water consurnpl’inn tiretn a. humidifier where (me is used . {40} Another undesirable . of a continuum vent may be that as continuous vents are always open. the blower typically needs to work harder to achieve the desired therapy pressure, for instance by operating at a higher onal speed, te compensate for the leakage thmugh, the centinuous vent. This may lead to lowered efficiencies in energy use. which may he impurtant in circumstances where the PAP device is being powered by a battery. Higher blower operating speed may lead to an inertaged noise output which niav increase the level of disturbance to the patient. increased blower rotation speed during uperaticn may also have e etftecta on the life of the hlnwer. In some cases, use of a centinueus vent may require use of a larger blower to meet therapy flow or pressure requirements. as centinuous vents may reduce the t therapy re or flow that is able to be provided to the patient when using the blower. {41} Of course some venting ”enquiredll‘l order to wash out carbon dioxide that is exhaled by the patient. 2.2.4 Air- Circuit 4120 {42} An air circuit: 417D typically comprise at least one conduit or tube constructed and arranged to deliver a supply of air or breathable gas. Typically. an air t may be placed between a PAP device underapatient interface Iii-1 humidifieris present then an air circuit may be placed between the humidifier and a PAP device. and/or between a humidifier and a t interface. In particular the air circuit may he in fluid communication with the outlet of the pneumatic block and the inlet to the patient interface to deliver a supply of in utthable gas from the PAP device to the patient in use. The. air circuit may he referred to us an air delivery tube. In such arrangements the air circuit may comprise a single limb or single conduit. Patient expired gas may be vented via an intentional leak vent or via, a. proximal pneumatic valve {43} In other cases a double limb air circuit may be provided where separate tu or liran are provided for inhalation and exhalation. Such a. double limb circuit comprises two conduits or tubee: an inepiratory tube that delivers air from the PAP device to the patient during inspiration; and an expiratory tube that delivers expired air from. the patient to on expiratory port: of the PAP device and then out an exhaust port. Geometrically the two tubeo may be arranged side—by—side, iii-line or co— y. Air flow between the expiratory port and the exhaust port may be regulated by a pneumatic valve located internally within the PAP device. {44} Heated single limb or double limb air delivery circuits may also he need to prevent rainoul‘. from occurring within the. air delivery circuits. 2.2.5 PAP Device {45} The air at positive pres Sure may be supplied to the airway of a patient by u PAP device such as a motondriven blower. The outlet of the blower is connected via an air circuit to a patient ace as described above. It is to be understood that: a PAP device es any device configured to provide a supply of rized breathable gas for providing CPAP, invasive or vasive atory therapy including but not limited to u CPAP device, Biéievel PAP device and a ventilator. 2.2.6 Humidifier {4'6} atory tuses commonly have the ability to alter the humidity of the breathable gas in order to reduce drying of the patients airway and consequent t discomfort and associated complications. The nee of a humidifier placed between the flow generator or PAP device or ventilator and the patient. interface produces humidified gas that minimizes drying of the nasal mucosa and increases WO 61848 patient airway enmfort. In addition in coeler Climates. warm air applied generally to the face area in and about the patient interface is more comfortable than cold air. {47} Humidity refers tn the quantity of w ater vapour present in the air. It. is commonly measured in two ways: ( l) Abselute Humidity (AH) is the actual content of, water recorded in terms Of weight per volume — usually in grams per cubic: meter (glnfi) or milligrams per liter {mg/L). (2.) Relative Humidity (RH) is a percentage expression of the actual water vapour content of “:1 gas compared to its capacity te entry water at any gi ven, temperature. {48} The capacity of air to hold water vapeur increases as the temperature of the air increases. This means that for air with a stable AH, the RH will e as the temperature of the air is increased. Conversely, for air satnnited with water ( 100% RH): if the temperature is reduced then the excess water will se out. Air breathed by humans is generally naturally heated and humidified by the airway to reach a. temperature of 370C and l. 00% humidity. At this ature the AH humidity is 44 rug/L . {49} Respiratory humidifiers are available in many forum and may he a lone device that, is d to a, respiratory device Via an air delivery tube is integrated with the respiratory device or cnnfignred to be directly coupled to the relevant atory appamtus. While passive humidifiers can provide some relief. generally a heated humidifier is required to provide sufficient humidity and temperature to the air so that the patient will be comfortable. Humidifiers typically comprise a water reservoir or tub having a ty of several hundred milliliters (1111),, a heating element. for heating the water in the reservoin a, central to enable the level of humidifieation to be . a gag inlet to receive gas frt‘im the flow generater or PAP device. and a gas outlet adapted to be connected to an air delivery conduit that. delivers the humidified gas to the patient interlhee, 3 BRIEF SUMMARY OF THE TECHNOLOGY [50} The present technology is ed towards providing, respiratory devices, such 33 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 man ufaeturability. {5.1,} A method of controlling pres sure or determining pressure control values foreontrol of pressure in the patient interface is sed. A vent valve may be used. with a respiratory device, where the vent valve may selectively block fluid communication n components: such as the flow generator, the patient interface, and/or the vent. An expiratory flow model may be. used to determine an expiratory characteristic such as an expiratory flow rate or pres sure in the patient interface where an indicative measure may not be available. 'il‘he expiratory flow model may receive inputs based on a measure of the patient’s respiration, such as the tidal volume, peak inspiratory flow rate or length of inspiration. The expiratory characteristic may be used by a controller to control a re in the patient interface to provide respiratory y to a patient at or close to a target pressure. {52} Some versions of the present. technology may include an apparatus for controlling a supply of breathable gas at a positive pressure for amelioration or treatment of a respiratory disorder. The tus may include a controller adapted to l setting of a y apparatus for providing a. supply of able gas. The therapy apparatus may be adapted to couple with a patient interface to deliver the supply of breathable gas to an airway of a patient. The patient interface may be adapted with (a) a valve configured to selectively block fluid communication between a blower of'the y apparatus and the patient, interface, and (b) :1 vent to exhaust. a flow of exhaust. gas from the patient interface. The ller may be configured to determine an expiratory Characteristic. It may also be configured to adjust a first pressure in the patient interface based on the expiratory characteristic by controlling the valve. {53} in some cases, the apparatus may further include the valve. The valve may include a movable n to selectively block fluid communication between the blower and the patient ace. The movable. portion may be configured to be movable by an or. The movable portion may be configured to be mo stable by a re difference acting on the movable portion. The movable portion may e or be a membrane. Optionally, the expiratory characteristic may he an. estimate of expiratory flow rate? an estimate of pressure in the patient interface or a phase of tion. The expiratory characteristic may be determined hased on an tory flow model. The expiratory flow model may include one or a combination. of a look~ up tnhle or a mathematical relationship or function. in some ceses7 the t; interface may be configured to deliver the supply of breathable gas to an airway of a patient; and the vent may he et'infigured to exhaust a. flow of exhaust gas from the patient interface. The valve may be further configured to selectively block fluid conununieation between the patient interface and the vent. The valve may be further configured to selectively block, fluid communication between the blower and the patient interface or the patient. interface and the vent. The apparatus may further include a lion: generator configured to te the supply of breathable gas at: a. second pressure. The first pressure may be adjusted by changing an output. of the blower. The output of the blower may be the second pressure. Optionally, the expiratory characteristic may be determined based. on one or more of: a ventilation volume. a tidal volume, a peak. inspiratory flow, a length of time in inspiration. 21 lung ance, a lung resistance, an end of ation or a start of expiration. The expiratory characteristic may be determined using a measure of respiration. [34}.fl. Sonic ns of the present: technology may involve a control . in :1 processor for determining a pressure. adjustment in a patient interface that delivers a. supply of air or breathable gas to entrance of a patients airways. The control method may include, in a presence of a. selective blocking of fluid communication between a blower and a patient interface, determining an exploratory characteristic.

The method may include ining an adjustment for a first pressure in the patient interface based on the expiratory characteristic. {55} Some. versions of the present technology may include an apparatus for controlling a. supply of breathable gas at a positive pressure for treatment of a atory disorder. The apparatus may include a controller. such. as including at, least. one processor, d to control setting of a blower of a therapy apps ratios for controlling a supply of breathable gas at a controlled pressure above ambient in. a patient. interface. The controller may he adopted to couple with at. least one sensor for 2014/050315 the therapy apparatus. The at least tine sensor may be configured tn measure pressurc through a t from the thnrapy apparatus to (In: patient ace. The conduit may he in fluid communication with the patient interace configurcd to deliver the Supply of breathable gas to an airway Uf a patient. The controller may" be further cenfigured to determine gar; pres sure in the patient interface in presence. of. far example al, blocking and clring of the conduit tn the sensor. The determination of the gas pressure in the patiant interface may invdlvn a first. unbinckcdcnnduit s and a second 'biocked«ccmd uit prriccss, such. as when: the sensnr may and may unt accurately measure the pressure of the patient interface respectively. {5.6} In some cases, the first process may determine the patient interface gas pressure from. a current measure of pressure from the sen sur in. presence cf unblncking of the cnntiuit to the sensnr. The first process may determine the t interface gas pressure from. a pressure drop ated with a. delivery conduit characteristic and the current measure of pressure. The first prnccss may determine a pressure ment. for preasure in, the patient interface from a encc between the determined patient interface gas pressure and a target. re {57} In some cases, the second prnccss may ninc thc patient interface gas: preasure {mm or based on a, modelled flnw estimate in pmscnce of ng of the- cnnduit tn the sensor. The inctlched flow estimate may be an estimate of expiratory flaw. The determined patient interface gas pressure may he c‘nicuiated. from an, elapsed time and the expiratory flaw estimate. The sccnnd procens may determine the d time by detecting an cud of inspiration, such. as with an analysis 017a measure train the sensor. The second procesn may determine a pressure adjustment for pressure in the patient interface from it difference between the determined t interface gas pressure and a target prcssurc. The crintrnller may be further configured for cyclical selection of the first prncesn and the second prncesa, The controller may select the first process upon determination Of patient, inspiration. The cnnt‘rniier may neiect the secnnd princess upon determination of patient expiratinn. Thc ltcr may be. further confignrnd to determine an unintentional innit flow by Subtracting a magnitude (if patient flow at determined point: of intiectinn fmm a total flow. The therapy apparatus may include the blower and the sensor. The apparatus may inciude the patient ace and the conduit. The tus may include a valve configured to selectively block expiratory gas communication to the sensor. {58} Some versirme of the present technology involve a method of a process nor to control setting of a blower of a therapy apparatue for providing a supply of breathable gas to a patient interface at a controlled pressure. The method may include. with a sensor of the therapy appa 'atus. measuring a pressure through a conduit from the therapy apparatus to the patient interface. the conduit: in. fluid communication with the patient inteifece. The method may further include detennining in a. first unblocked—ounduit process and a second d—conduit s a patient interface gas pressure for control of the blower in presence of blocking and unblocking of the conduit to the sensor. [59} The first process may determine the patient interface gas pressure from a current measure of pressure from the sensor in presence of unbloclting of the conduit to the sensor. The first process may determine the patient interface gas pressure from a presSure drop associated with a delivery conduit characteristic and the current measure of pressure. The first process may determine a pressure adjustment for pres SUITE: in the patient ace from a difference between the ined patient interface gas pressure and a target pressure. {60} The second process may determine the t ace gas pressure from a. modelled flow eetimate in presence of blocking of the conduit to the sensor. The ed flow estimate may be an. estimate of expiratory flow. The determined patient ace gas pressure may be calculated from an elapsed time and the expiratory flow estimate. The second process may determine the elapsed time- by detecting an end of inspiration. The second procesu may determine a re ment for pressure in. the patient interface from a difference between the determined patient interface gas pressure and a, target pressure. The method may include cyclically selecting the first g and the second process. In some cases, the first process may be selected upon determination. of patient inepiration. In Some cases. the second process may be selected upon determination of patient tion.

The method may further include determining an, unintentional leak flow by subtracting a ude of patient flow at ined point of inflection from a total flaw. In some CflSBS, the patient interface may include a. valve cnnfiguted to selectively black expiratnry gas communication to the. sansnt. {61} Of course, portions of the aspects may farm suhvaspects (if the t technolngy. Alsng various ones of the sub—anpefls and/0r aspects may be combined in QuS s and alga constitute additional impacts or sub-aspects 0f the pi‘ascnt te-chnnlngy. [62} Other {natures of the tnnhnnlugy will be apparent from cnnsidetatinn Of the information containcd in that following detailed description, abnlmct, drawings and claimsi 4 BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS {63} The prescnt technology is illustrated by way of examplet and 71011 by way of limitation in the figures of the accompanying drawings, in which like reference numerals refer tn similar elements ing: 4.1 TREATMENT SYSTEMS {64} Fig. 1A shows a system. in acmt’dance with, the present technology. A patient 1000 wearing a patient interface, 3000, shown in the farm at nasal pillows mask, receives a supply of air at positive pmsaure fmm a PAP device 4000. Air from the PAP device is fied in a humidifier 5000, and passes along an air circuit 4 l '?0 to the patient 1 000, {65} Fig. 13 shown an example PAP device 4000 coupled to a. fier 5000 in usr: (in a patient 1000 with palicnt facn 3000 in. Illt': form nf a nasal. mask. {60} Fig. 1C showa an example PAP device 4000 led to a humidifier 5000 in use on a patient 1000 with a patient ll’ltfll‘fflce 3000 in the form nf fullsface mask. 4.2 THERAPY 4.2.1 Respiratory syatem {67} Fig. 2A shows; an overview of a human respiratory System including the nasal and. oral es. the larynx, vocal folds. oesophagus, a, hl‘Dl’lChU-S, lung. alvet'ilar sacs, heart and diaphragm. {68} Fig. 2B Shows a View of a human upper airway including the nasal cavity, naaal bone, lateral nasal cartilage, greater alar caitilaga. l, lip Superior, flip interior. larynx, hard palate, soft palate. a_rynx,, tongue, cpiglottis, vocal folrla. oesophagus and trachea. 4.3- PATIENT INTERFACE {69} Fig. 3A shows a patient intiefiface in accordance with one form of the. present technology. 4.4 PAP DEVICE {70} Fig. 4A showa an exploded View of a PAP device in accordance with one form of the present technology.

{I’ll Fig. 413 Shows a schematic diagram of the pneumatic circuit of a PAP device in ance with one form of the present logy. The directions of upstream and downstream are indicated. {72} Fig. 4C shows a schematic diagram of the electrical components of a PAP device in accordance with one aspect of the present technology. {'73} Fig. 41) 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 SDlld lines indicate an actual flow of information. for example via an electronic . {74} Fig. 4B is a flow chart illustrating an example method d out by the therapy engine of Fig. 4D in accordance with one aspect of the present technology. 4.5 HUMIDIFIER {7‘5} Fig. 5A xiiows a humidifier in accordance with. one aepeei of the present logy. [76} Fig SB shows a schematic of a humidifier i1: accordance with one aspect of the present tech'nolog 3:. {7'7} Fig. 5C Shows a tic diagram of a humidifier control circuit according to one aspect of the present technology 4.6 BREATHING WAVEFORMS {'78} Fig. 5A ehows a model typical breath waveform of a pawn while. sleeping. The horizontal axis is lime, and the vertical axis is respiratory flow. {79] Fig. 7B shows an example of a sewn-continued vent valve, wherein the variable flow path is open to allow the exhaust of gas therethrough. {80} Fig. 7B shows an example of a sewn-controlled vent valve. wherein the variable flow path is closed to prevent the exhaust of gas thereihmugh. {81} Fig. 8A shows an example {if a flexible divider vent valve comprising a movable membrane, wherein the movable membrane is in a first on. {8‘2} Fig. SB Shows an example of a flexible divider vent valve sing a movable membrane, n the movable membrane is in a second position [83} Fig. 8C shows an example of a flexible divider vent valve comprising a movable membrane, wherein the movable membrane 18 in a. third position. {84‘} Fig. 9 shows an example of a breath flow wavefoim, n a. measure of the respiratory flow is not available during the atmy portion of the breath cycle. {85} Fig. 10 Shows: an e of a model of an expiratm'y portion of a breath flow waveform. {86} Fig. l. I. shows an example of 21 breath flow waveform, wherein an inspiratory portion of the breath cycle is measured and an tory portion of the breath cycle is ined by a model. {87} Fig. 11A shows another esnmple of 21 breath flow wavefonn. wherein no inspiratory portion of the breath Cycle is measured and an expiratory portion of the breath cycle is determined by a model. [88} Fig. 11B shows a further example of a breath flow rm. wherein an inspiratory n of the breath cycle is measured and an lm’y portion of the breath cycle is determined by a model. {89} Fig. 12A shows a model of a lung represented as a mechanical model. {90} Fig. 12B shows a model of a lung represented as an electrical Circuit.

I91} Fig. 13 shows a flow chart representation of one aspect of the present technology with a. process for implementing control of a therapy apparatus with. a sensor subjected to ic. ng and unbloeking. {92} Fig. 14A shows- a longer form of a model typical breath waveform as shown in Fig. 6A. {93} Fig. 14A shows a longer ferm of a model typieal breath waveform as shown in Fig. 6A, wherein fluid commnnieation between the flow sensor and the patient interface is blocked during expiration. {94} Fig. 15 shows a flow chant representation of one aspect of the present technology.

DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY {95} Before the present technology is described in further detail, it is to. be understood that the technology is not. d to the particular examples. described herein, which may vary. It is also to be understood that the terminology used in. this disclosm‘e is. for the purpose of describing only the panicnlnr examples discussed herein, and is not intended to be limiting. {96‘} The ihllnwing description is provided in en to various examples which may share one or mere n characteristics ander features; it is to he understeed that one or more features of any one example may be enrnbinable with one or more features of another example or other examples. In addition, any single feature er combination of features in any of the examples may itute a further example. .1 SYSTEMS {9?} In One. form, the present technology comprises apparatus for treating a respiratory disnrder. The apparatus may enmprise a flew generator or ’blnwer for supplying rised respiratory gas, such as an; to the t 10063 via an air delivery tube g tn a patient interfa ‘e 3008. i818} s described in the present snre may be applicable fer medical devices such as a, PAP device, but, also other types 01’ atory s not described in the present document. For example, aspects of the present technology may be applicable in respiratory s where it flew of, air is provided to a user.

More specifically, aspects ef the present technelegy may be applicable where the flow of air is provided to the. user at a pnsitive pressure relative to atmospheric pressures. ‘2 THERAPY {99} In one forum the present technnlngy comprises a methed for treating a respiratery disorder cempri sing the step of applying positive. pressure to the entrance of the airways (if a patient 10m). .2.1 Nasai CRAP for OSA {100] In one {Grim the present technnldgy cemprises a ntetlled of treating Obstructive Sleep Apnea in. a patient by applying nasal continuous positive airway pressure in the patient. {101] In certain embodiments of the present. teehnolngy, a supply of air at pesitive pressure is presided tn the nasal passages 0f the patient via one nr both nares. .3 PATIENT INTERFACE 3000 {102] A non—invasive patient interface 3000 in accordance with one aspect of the present technology comprises the following functional aspects: a seal-tormjng structure 3100, a plenum chamber 3200, a positioning and stabilising structure 3300 and a connection port 3600 for comiection to air circuit. 4170. In some fonns a onal aspect may he provided by one or more physical components. In some forms, one physical ent may provide one or more functional aspects. In use the sealaforming structure 3100 is amtnged to surround an entrance to the always of the patient so as to facilitate the supply of air at positive pressure to the airways. .3.1 orming structure 310‘} {103] In one form of the present technology, a seal—forming structure 3100 provides a sealingfot‘ming e, and may additionally provide a n‘iing function. {104] A Seat-forming structure 3.109 in ance with the t logy may be constructed from a soft, flexible. resilient. material, such as silicone.

HOS] In one form the seal—forming portion of the non—invasive patient interface 3000 comprises a. pair of nasal puffs, or nasal pillows, each nasal puff or nasal pillow being constmcted and arranged to form a seal with a respective nails of the nose of a patient (see Fig. la). {lilo} In one form the vasive patient interface 3000 comprises a seal.» forming portion that forms a seal in use on an upper lip region (that is the lip superior) of the patients face (see fig. lb). {107] In one form the nvaaive t interface 3000 comprises a seal“ forming portion. that forms a seal in. use on a Chin—region of the patients face (set: Fig. 14:). .3.2. Continuous Vent 3400 {108] In one fomi, the patient interface 3000 include a continuous vent 340i) constructed and arranged to allow for the washout of exhaled carbon dioxide. To achieve washout, of exhaled carbon dioxide, the continuous vent 3400 may be configured to exhaust a flow of exhaust. gas from. the patient interface. 2014/050315 {109] One form of continuous "vent 3400 in accortianee with the present. logy ses a plurality of holes; for example, about Bil to about 80 helesi or about 40 to about 60 holes, or about 45 to about 55 holes. {11m According to some au‘angements, the continuous vent 3400 may be d in the plenum, chamber 3208. or in a decoupling StI‘LICtui’B 3500, eg, a swivel 3510. In some cases, the continuous vent may be fixed. such as to have a fixed set, of holes for venting, although in other cat-see, the uous vent may be variably continuous to se variable venting eflun‘aeteneties while continuously ting a. flow of exhaust gas from the patient interface. .3.3 Decoupling structure(s) 3500 {l '1 13 In one lhnn the patient interface 30le includes at least one decoupling Stinctnre 3500i for example a swivel or n ball and socket. .3.4 Connection port 3600 {1112] Connection port 3690 allows for eonnetttion to the air circuit 417D. .3.5 Forehead support 3700 {l 1.3] In one form, the patient interface 30% includes a forehead support 37m). .3.6 Anti-asphyxia {11.43 In one form, the patient face 3000 includes an anti-asphyxia valve. .3.7 Ports [1151 in one tom of the present. technology, a patient. internist: 3000 includes one or more ports (not shown), that allow access to the volume within the plenum chamber 3200. In one form this allows a. clinician to supply supplemental oxygen. In one form this allows for the direct, measurement of a property of genes within the. plenum r 3200, Such as the pres sure. .4 Air Circuit 417(1 {316] An air circuit 4170 in aecordnnee with an. aspect of the present technology is constructed and arranged to allow a flow of air or breathable gases between various. eompnnents, such as between. the pneumatic block 4020 and the patient interface 3000‘ In one airnngement, a first air circuit, 4170 may extend between an outlet. of the PAP device 4000 and an, inlet of the humidifier 5000, and 21 second air circuit: 417() may extend between an outlet of humidifier 5000 and the patient interface 3000. In another arrangement the inlet of lmrnidifier 5000 may be directly coupled to the outlet of the PAP device 4000 without the need for an intervening air circuit. 4.170.

However, in Such an arrangement an air circuit 4170 may he provided n the outlet of the humidifier 5000 and the t interface 3000. .4.1 Variable Vth 4400 [l 17] According to one form of the present technology. a respiratory treatment system (eg. as a part of an air circuit. 4170 or a conneetor) may se a variable root 4400 configured to t’ a, flow of exhaust gas from the patient interface 3000.

A variable vent 4400 may be located away from the patient interface While being in fluid ication with the t interface 30th). Suitable locations for the variable vent. 4400 may include in the air circuit 4170. in the PAP device 4000. or in a separate connector connected to the air circuit 4170 between the patient interface 30th} and the PAP device 4000. The variable vent 4490 may also be provided within the patient interface 3000 in a similar manner to and instead of. or in addition to the continuous vent 34th:) described above. in some cases. the volume of air path present for example of the air circuit 4 HO, between the le vent 4400 and the patient interface 30001113y affect how much of the exhaled air is redireathed by the patient.

The variable vent 44l§l0111£1y be located nearer to the patient interface 3000 than to the PAP device 400001“ blower 4142 in order to reduce any athing of CO; by the patient. Such a variable vent may, for example, he 21 vent assembly described in US- Patent Application Publication No. US~2tll4a0283831aAl_, the entire disclosure of which is incorporated herein by reference. .4.2 Vent Valve 4450 [HS] in one form, the. variable tv"e11t44th may se n vent valve 4450 to overcome some of the disadvantages associated with use of a continuous vent 3400.

As described above. some of the known disindvnntages associated with use of a continuous vent may include increased loss of humidity. lowered energy efficiency, increased noise output and lowered m therapy pressure level. These disadvantages may he more significzmt during an expiration phase of a patient’s breath. {119] A vent valve 4450 may overcome the above disadvantages by aeleetively blocking fluid communication between components as required. Preferably, the vent valve 4450 may block fluid communication between the patient interface 3000 and the variable vent 4400 during ation, and allow fluid ication between the patient ace 3000 and the variable vent 4400 during expiration The vent valve 4450 may also allow fluid communication between the blower 4t 42 and the. patient interface 3000 during inspiration and block fluid eonnnunication between the blower 4142 and the patient interface. 3800 during expiration. {120] In some cases, the vent valve 4450 may be. configured to Simultaneously block, or simultaneously allow, fluid communication n two sets of components. For instance, the vent valve 4450 may be configured to simultaneously block or simultaneoualy allow fluid communication, between the patient interface 3000 and the variable vent 4400 as well as fluid communication between the patient ace .3000 and the blower 4142. Alternatively, or additionally, the vent. valve 4450 may be configured so that“ at any onetime, it blocks fluid communication between one set of components and allows fluid communication between another set of components. For imitationa the vent valve 4450 may be ured to block fluid communication between the patient interface 3300 and the blower 4l42 while ng fluid communication between the patient interface 3800 and the variable vent 440.0.

It, should be understood that in some an‘angementa, the vent valve 4450 may not completely block fluid communication between two components. Many of the advantages bed above in relation to using a, vent valve 4450 may be achieved, for,“ example, by reducing the amount of gas flow between components, without completely blocking fluid ication therebetween. It should be also understood that, although according to some arrangements the vent valve 4450 selectively blocks fluid ication between components based on indicators such as. an enph‘atory chamcteristie or a model of a respiratory eircuitsi the vent valve 4450 may also selectively block fluid communication n components based on other indicators. One suitable indicator may he the presence of Chemo—Stokes Respiration, a or fitment for which. may be use of a vent valve 4450‘ to increase the amount of CO; that is rebroathed by the patient, {122] As described above. a vent valve 4450 may be able to selectively block fluid cemmunicntion between ents Such as the blower 41,42, the patient interface 3000 and the variable vent 4400. Accordingly, at least some portion of the vent valve 4450 may be located closer to the patient, interface 3000 than the blower 41423 in order in Selectively bleak fluid communication n the variable vent 440i} and other components. {123] The vent valve 4450 may be eenstrueled in nne er more of multiple forms suitable to provide a variable venting function. One Stumble form may use a servo- controllerl vent valve 4452, for example as ehown in Figs. Vat—“7b or as disclosed in co— owned PCT applieatien publication number WC) 2013;040198. Another suitable form may use a flexible (livider vent valve 4460, for example as shown in Fig. Sir-8b or as disclosed in eo-owned PCT application atinn number Wt) 2013ft)67592. The entire contents, {if both PCT patent npplicatinns W0 20131040198 and WO 2013/067592 are incorporated herein in their entiret}r by ernssereference. {124] in seine arrangements of the present technology. the use of a vent valve 4450 may . the way in which a pressure in the patient interface 3000 (Le, gee presenre) is adjusted. In some prior systems, the pressure in the patient interface 3000 is edby controlling the operation of the blower 4142,. such as by increasing or sing a rotational speed of the blewer 4142 to increase or decrease a pres tune in the patient interface respectively. When the blnwer 4142 in in fluid communication with the patient interface 3000., the pressure in the patient ace 3000 may be correlated to the pres sure. at the outlet: of the blnwer 4142. The correlation may be chametcrised as a pressure drop, which may be dependent: en a number of factors such as blower speed, length and profile of the air circuit; stilt), er teristics of the patient interface including Size of the plenum chamber 32.00 or arrangement of the variable vent 440i). [125} An adjustment of the preesure in the t interface 3000 may affect the pressiure of the flow of breathable gas at. nnnther location or component which is in fluid ication with the patient interface 3008. As a ary. it would be understood that instead of aiming tn . the pressure in the patient. interface 3000, pressure at another location or component such as the pressure in the air circuit 4170 may be used as an adjustable target: re while taking advantage of the present teelnteingy. {126] it is nntetl that aapeeta nt‘ the present teehnntngy in relation tn adjustments of pressure andfer change of flew impedance may be le fer medical devices and other types of respiratory devices, Such at; these wherein an air flow is prev-idea in a user at. a positive pressure. For example, an y of a respiratory device tn enntml a pressure delivered to its user may improve cernt‘nrt of the user, which may provide. usability ts. {127] One known prior methnd of determining prez‘ssure in the patient interface 3000 is to meaanre a pressure near the outlet of the blower 414?. and to apply a preasure drop cerreetinn tn compensate fer less in re as air flows therethmugh.

The. ability tn determine the pressure in the patient interface 3000 has been used to compensate for any changes caused. by the t” 3 inspiration or expiratien.

Typically. inapiratinn may decrease the pressure in the patient ace 30th and expiralien may se the pressure in the patient interface 300%). Some prior devices have regulated pressure in the patient interface 3000 during inspiration and during expiration by measuring a change in pressure, and changing the speed of the blower 414,2 accordingly. {128] In the present technningyi various methnds may be used to adjuat a pressure in the patient interface 3000, for example thrt'tngh a variable property of a vent; valve 445%. In one form. flow impedance of the vent valve 4450 may be changed t0 adjust re in the patient interface 3000. in the case at" a continued vent valve 445?. as ShDWI‘t in Fig. 7A and Fig. 713‘, its flow impedance may be changed by varying the opening of an eXhaust area 4410 at the variable vent 4400 to vary the amount at? venting thmngh the variable vent 4400. One suitable form of varying the ripening Of a variable flow path 4415 to the exhaust area 4410 of the variable vent 440i) is shown in Fig. 7A and Fig. YB. where an actuator 4456 moves a movable pardon, such as a valve body 4458. to adjust the level at" opening of the variable flow path 4415 tn the exhaust area 4418 of the reliable vent ill—tilt"). Fig. 7A shows an example where the. variable flow path 4415 to the exhaust area 4&0 of the variable vent 4400 is at least partially open to aliew the t of gas as indicated by the atTQWS. Fig. 7B shows an example wherein. the variable flew path 4415' to the exhaust: area. 4410 ml" the variable vent 4480 is substantially closed by pesitiening the valve bndy 445.8 is a ntially closed or "blocked position. In seine ammgements, the variable vent 4400 may be configured to block fluid enrnmunicatinn entirely between a. first. side 4464 and a second eppnsing side 4466. {129] atively, in one form as shown in Fig. 8A and Fig. 813, the e divider vent valve 4460 may comprise a movable n... such as a membrane 4462.

In some cases the membrane 4462 may be defnrtnable. The nt, and/0r deflectinn of the membrane 4462 may affect the flow impedance through the exhaust area 4410 anther between the first side 4464 and a second side 4466 cf the membrane 4462.. The membrane 4462, may be configured (eg. deflected andr‘er rewpositinncd) by changing a pressure difference between a first side 4464 of the membrane 446?. and a second opposing side 4466 of the membrane 4462, thereby having a resulting force act on the znie. In some arrangements. the blower 4142 may be used, to change a. pressure on the first side 4464 of the membrane 4462, thereby changing the net pressure applied therein (between the first side 4464 and the second side 4466) and thus reconfiguring the membrane. Fig. 8B shows an example wherein the membrane 446213 ammged 30 that the impedance of the variable vent 4400 is higher than in the configuration shown in Fig. 8A. This is caused by a greater increase. in the pressure on the first side 4464 Of the membrane than the pressure on the second side 4466 (if the membrane resulting in the deflection of the membrane tnwards the secnnd. side 4466.

In contrast the impedance of the variable vent 4400 as strewn in Fig. 8A may be substantially balanced between the first side 4464 and the second side 4466 (if the membrane, resulting in a lower impedance configuratien {If the variable vent 4400.

Either, or both: of the cnnfiguratinns shown in Figs. 8A or SB {er any configurations therebetween) may be desired during an expiration phase of the respiratory cycle tn allnw expired gas to be exhausted through the exhaust area 4410. For example, the centiguratien shown in Fig. 8A may he desired where the tnry flow rate is reiatively high, whereas the configuratinn shown in Fig. 813 may he d when the tory flow has subsequently decreased. The pressure of the variable vent 4400 may be increased on the first side 4464 cf the membrane to funher deflect the membrane to at least. partially or tely block the exhaust area 4410 and consequently open up the path between the first side 4464 and the second side 4466 of the variable vent 4400 as shown in Fig. 8C. Such an arrangement may he desired during an inspiration phase of the respiratory eyelet {130] According to one aspect of the vent valve 445.0, the blower 4.142 may not. be in fluid communication with the t interface 3009 during some ns of therapy, such as during expiration. In this entent, a. pressure meaSured near the outlet of the blower 4142 may not have ient. eotrelation to a pressure in the patient interface 3000 in order to determine the pressure in the t interface 300i). {131] In some instances, it may be le to measure a gas property, such as pressure or flow rate in the t interface 3000 side of the vent valve 4450. This may he achieved by introduction of a sensor on the patient interface 3000 side of the vent valve 4450, or by uction of a fluid. communication such as a sensing lumen or a pressure port between the two sides of the vent. valve 4450. However, the uction of a sensor may add cost to manufacturing and/or odd complexities in order for a controller 42-30 to communicate with a sensor located away trout the blower 4142;. introduction of a pressure port or a sensing lumen may also introduce additional compiesities and cost. In some cases, introduction of a pressure port or a sensing lumen may also increase CO; re«hreathing as at. least some of the t gas may he stored in the pressure port!sensing lumen, which may be also undesirable. Still furthere introduction of such additional components anchor eomplexi ties may adversely if feet robustness of the system, or make it more onerous to achieve the equivalent level of robustness.

According to one aspect of the present technology an expiratory ehaneteristie may be determined while the vent valve 4450 blocks fluid communication between components, such as between the blower 4142 and the patient intert‘aee 3000. In, some cases, the expiratory characteristic may be determined without a. measurement of a gas property on the patient interface 3000 side of the vent vaive 4450 while fluid communication is blocked thereto. For ce, a. model of the pati.ent“s respiratory circuit and various ents connected to the patient.’s respiratory circuit may be used to determine an expiratory eharacteristic such as the expiratory flow item the patient’ s lungs. The expiratory characteristic may then he used as an input parameter to a, controller 4230g for example to adjust the pressure in the patient interface 3000. {133] Although in the above discussion of the variable vent 4400 a single vent valve 4450- is described to selectively block fluid communication between components such as the blower 4142, the patient interface 3900 and the variable vent 4400, it should he understood that multiple, te vent valves 445011121}; he used to achieve the same effect, A person skilled, in the art would also understand that in some cases, the vent valve 4450 may he displaced from the exhaust area, 4410, while- retnining benefits from the t technology. {1343 Modelling methods to detennine expiratory characteristics while the vent valve 4450 blocks eonununieution, between ents, and use of the determined expiratory characteristic will be described in further detail below. .5 PAP DEVICE 4000 il35] A preferred PAP device 413th in accordance with one aspect of the present technology comprises mechanical and pneumatic components 4100, electrical components 42.00 and is programmed to execute one or more algorithms 4300. The PAP device preferably has an external, housing 401 1), preferably formed in two parts? an upper portion 4012 of the external housing 401i), and a lower portion 4014 of the external housing 4010. In alternative forrnsl the external g 4010 may e one or more panellis) 4015. Preferably the PAP device 4000 comprises a chassis 4016 that supports one or more internal components of the PAP device 4000. In one form 21 pneumatic blocl: 4020 is supported by, or formed as part of the Chansis 4016. The PAP device 4000 may include a handle 4018‘ {136] The pneumatic path of the PAP device 4000 preferably comprises an inlet air filter 4112, an inlet muffler 4122, a controllable pressure device 4140 capable of ing air at positive pressure rably a hflower 4142), and an outlet muffler 4124. One or more preasure sensors 4272 and flow s 4234 may be included in the pneumatic path. {137 l The preferred pneumatic block 4(120 ses a portion of the pneumatic path that is located within the al housing 4tl10, {138] The PAP device- 4090 preferably has an electrical. power eupply 4210. one or more input devices 42 20, u central controller 4230. a therapy device crmtroller 4240, a pressure device 4140, one or more protection ts 425.11, memory 4260: WO 61848 transducers 4270. data communication interface 4280 and one or more output devices 4290-. Electrical components 4200 may be mounted on a single Printed t Board Assembly (PCBA) 420:2. In an alternative form, the PAP device 4000 may include. more than one PCBA 4202. {139] The. l controller 4230 of the PAP device clfltltl is programmed to execute one or more algorithm modules 430E}, preferably including a. pre~processing module 4310, a therapy engine module 432th a pressure control module 4330, and further preferably a fault condition module 4340. .5.] PAP device mechanical 8; pneumatic components 410i) .5.1.1 ,Air fillet-(s) 4110 [1401 A PAP device in accordance with one form of the present technology may include an air filter 41105 or a plurality of air filters 4l. 10. {141] In one form, an inlet air filter 4112 is located at the beginning of the pneumatic path upstream of a blower 4142.. See Fig. 4b {142.} In one term” an Outlet air filter 4114, for examnle an antibacterial filten is located between an outlet of the pneumatic block 4020 and a t lntert‘ on 3000.

See Fig. 4b. .5.1.2- lVIu.ft.'ler(s) 4120 {143] In one 'lform of the present technology, an inlet muffler 4122-3 is located in the pneumatic path upstream of a blower 41-42. See Fig, 4b.

{M4} In one form of the present technology, an outlet: muffler 40.24 is located in the pneumatic path between the blower 4142, and 21 patient intexface 3000. See Fig. 4b. .5.1.3 Pressure device 4140 {145] In a profound form of the present. technology, a re device 4140 for producing a flow, or a , of air at positive re is a. controllable blower 4142.

For exmnple the blower may include a hrushlese DC motor 4144 with one or more impellers housed in a volule. The blower may be preferably e of delivering a supply of air, for example about 120 iilresfminute at a positive pressure in a range from a’beut 4 Cang'D to about '30 (>anqu or in other forms up to atheut 30 cniH;(}-. {146] The re device 4140' is under the centre}. of the therapy device controller 4340. 55.1.4 Transducerts) 42-70 {147] In one form of the present logy, one or more transducers 42,70 are located upstream of the pressure device 4140. The one or more transducers 4270 are constructed and arranged to measure preperties of the air at that point in the pneumatic path. {7148] In one term of the present technology, one or more transducers 4270 are lecated downstream 0f the pressure device 414102 and upstream of the air circuit 41'70.

The one or mme transducers 4270 are constructed and arranged to e properties of the air at that point in the pneumatic path. {149] In one form of the present technology, one or mere transducers 42.70 are located proximate to the t interface 3000. {150] Transducers may be internal 0f the device, or external tit" the PAP . internal transducers may include for example preSSur-e, flow speed or Oxygen sensers.

Externai ucers may be located for example on or form part Of the air delivery circuit, e.g. the patient interface. External. transducers may be in the form of non- contact sensors such as a Doppier radar movement sensor that transmit er transfer data to the PAP device. .5.1.4.} Flow 4274 {151] A flow transducer 4274 in accordance with the present technology may be based on a differential pressure transducen for example, an SDP600 Series. differential pressure transducer from SENSIRION. The differentist pressure ucer is in fluid cornmunicatien with the pneumatic Circuit, with one of each 01‘? the re transducers eenneeted to tive first and second points in a flow restricting element. {152} In use, a signal. representing total flow Qt from the flow transducer 4274 is received by the processor 4230. .5.1.4.}: Pressure 4272 [1531 A pressure transducer 4272. in accordance with the present technology is located in. fluid communication with the pneumatic circuit. An example of a suitable pressure transducer is a sensor from the ELL ASDX series. An altemetix-‘e suitable pressure transducer is a sensor from the NPA. Series from GENERAL ELECTRIC, [l 54] In use, a signal from the pressure transfiaeer 4272, is received by the processor 4230. In one form. the signal from the pressure transducer 4272 is filtered prior to being received by the processor 4330. 55.1.4.3 Motor speed 42?6 In one form of the present logy a motor speed. signal 4‘2?6 is ted. A motor speed signal 4276 is preferably provided by therapy device controller 4240. Motor speed may. for example, be generated by a speed sensor, such as a Hall , sensor. .5.1.5 Anti-spill hack valve 41m llfiél In one form of the present technology. an pill back; valve is located between the humidifier 5000 and the pneumatic hloelt. 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. .5.1.6 Oxygen delivery 4180 {l 57] In one form of the present technology, supplemental oxygen 41.80 is delivered to a point in the tie path.

{J58} In one form of the present technology, supplemental oxygen 4180 is delivered upstream of the pneumatic block 4020. [159} In one form of the t lrogy, supplemental esygen 4180 is delivered to the air cite all 41 70. {168] In one "term of the present technology? supplemental exygen 41.80 in delivered to the patient interface 3000. .5.2» PAP device electrical cumpenents 420i.) .5.2.1 Power supply 42110 In cnc form at the present technelogy power Supply 4210 is internal. of the external g 4010 Of the PAP device 4000. In another form of the present technnlogy, power supply 4210 is extemnl of the external housing 4010 of the PAP device 4000. {162] In one form, of the present technology power supply 42,10 prnvideu electrical power to the PAP device 4000 nnly. In annther form of the preeent technelogyi power supply 4210 provides electrical power to both PAP device 4000 and humidifier 5000. .5.2.2 Input devices 4220 {163] In one form of the present logy, a PAP device 4000 includes cue or mere input. devices 4220 in the form of buttens, switches or dials to al'lcw a persnn to ct with the device. The buttons, Switches or dials may be physical devices, or scl’tware devices accessible via a tench screen. The bnl‘tnns, switches or dials may, in one form, be physically connected. t0 the external housing 401G, or may? in another fermi be in wireless cnmmunicatinn with a receiver that is in electrical counecticn to the central controller 4230. {164] In one form the input device 4220 may be constructed and arranged to allnw a permit to select a value andfor a menu . .5.13 l oller 4230 In one form (3f the t technology, the central controller 4230 is a sor suitable to control a PAP (levies: 4000 such as, an X86 INTEL pi‘ocessnr. {166} A pmcceser 4230 suitable In control n PAP device MW) in accordance with amether form of the present technolegy includes a, processor based on ARM Cnrteng pmceegm‘ from ARM Holdings. For example, an STD/{3‘2 series microcontmller from ST MICRDEL‘ECTRONICS may be used. 2014/050315 {167] Another proceasor 4230 suitable to control 21 PAP device 4000 in accordance with a further alternative form of the present technology includes a member selected from the family ARMQ—based 32—bit RISC CPUS. For example, an STR9 series microcontro‘ller from ST MICROELECTRONICS may be used. l: l 68] In certain alternative forms of the present technology, a 16-bit RISC CPU may be used as the processor 4230 for the PAP device 4000. For e a processor from the MSP430 family of tn‘ieroeontrollere, manufactured by TEXAS- INS'I‘RUMENTS. may he used.

H69] The processor 4230 is configured to e input signalts) from one or more ucers 42-70, and one or more input devices 4220, {NO} The processor 4230 is configured to provide output signalte) to one or mrn‘e of an output device 4290, a therapy device controller 4240, a data communication ace 4280 and humidifier controller 5250. [1‘71] In some forms of the present logy, the processor 4230, or multiple such ors, is configured to implement: the one or more methodologies described herein such as; the one or more algorithms 43th) expreseed as computer programs Stored in a non—transitory computer readable storage medium such as memory 4261').

In some cases an previously discussed! such pr‘oeessorts) may be integrated with a, PAP device 4000. However, in some forms of the present technology the s sorts) may be implemented discretely from the flow generation components of the PAP device 4000, such as for purpose of performing any of the methodologies described herein without directly controlling delivery of a respiratory ent. For example. such a proeees'or may perfonn any of the methodologies described herein for purposes of determining control settings for a ventilator or other respiratory related events by analysis of stored data such as from any of’ the sensors described herein. {172] In one form of the present technology, the l controller: 4230 is a dedicated, electronic circuit configured to receive input. signelts} from the input device 4220, and to provide output Signziltsl to the output. device 4290 and,"or the therapy device controller 4240. 2014/050315 {173] In one form, the central controller 4230 is an applicalionne'specit‘ic integrated circuit ll’l another form, the l controller 4230 comprises discrete electronic components. .5.2.4 Clock 4232 {174} ably PAP device 4060 incl odes a clock 4232 that: is ted to processor 4230. .5.2.5 Therapy device controller 424i} [175} In one form of the present; technology, therapy device ller 4240 it: a preseure control module 4330 that forms part of the algorithms 4300 executed by the processor 4230.

U76] In one 'lTorm of the present teelmology, therapy device controller 42340 is a dedicated motor control integrated circuit. For example in one form a. MC3 3035 ’brushless DC motor controller, manufactured lay QNSEMI is used. 6 Protection circuits 4250 {17?} Preferably a. PAP device 4000 in accordzmce with the present technology Ct‘JITlpl‘lBES one or more protection circuits 42581. {178] One form of protection circuit 425C} in aecordance with, the present technology is an electrical protection circuit. {179] One form of protection circuit 4250 in accordance with the present technology is a temperature or pressure safety circuit. .5.2.7 Memory 4260 {189] In ance with one form of the t technology the PAP device 4000 includes memory 4260, preferably non—volatile memory. In some forum memory 4260 may include battery powered static RAM. In some fennel memory 4260- may include volatile RAM. {181] Preferably memory 42.6015 located on FCBA .4203. Memory 4260 may be in the form of Eli-PROM, or NAND flash. (a: U] H.823 Additionally or alternatively, PAP device 400(3 includes removable form of memory 426a for example a memory card made in accordtmce with the Secure Digital {SD} standard. {183] In one form of the present technolong the memory 4260 note tlS a non— transitory computer readable storage medium on which is stored computer program instructions cxpreosing the one or more methodologies described herein, such as the one or more thms 4300. .5.2.8 Data communication systems 4280 ll 84] In one preferred form of the t technology, a data communication interface 4380 is provided, and is connected to processor 4230. Data communication interface 428i) is preferably conncctnble to remote extremal ication network 4282., Data communication interface 4280 is preferably connectnble to local external communication. network 4284. ably remote external communication network 4283 is table to remote external device 4286. Preferably local external communication network 4'284 is connecteble to local external device 4288. {l85} In one form, data communication interface 4280 is part, of processor 4230.

In another form, data communication interface 428() is an integrated circuit. that is te from. processor 4230. {i 86] In one form, remote external. communication k 4282, is the lnternet.

The data communication interface 4280 may use wired communication. (eg. via Ethernet, or optical fibre) or a wireless protocol. to connect to the Internet. {l 87] In one form, local al. communication network 4284 utilises one or more connnunicntion standards, such as Bluetooth, or a consumer infrared protocol.

B88] In one form, remote external device 4286 is one or more computers, for e a r of networked computere. In one form, remote external device 4286 may be virtual computers, rather than al computers. in either case, such remote external device 4236 may be accessible to an appropriately author-inert person such as a clinician. 2014/050315 {189] Preferably local external device 4238 is a perennal er, tnnhile phone, tablet or remote l. .5.2.9 Output: s including optional display. alarms 4290 [190} An output device 42% in accordance with the present. technology may take the form of one or more 01" a . audio and haptic unit. A visual display may be 3 Liquid Crystal Dieplay (LCD) or Light Emitting Dinde (LED) display. .5.2.91 Display driver 4292 {191] A display driver 4292 receives as an, input the Characters. symbels, or images intended for display on the display 4294. and converts them to commandt; that. cause the display 4294 to display these terg, symbelg, or images .2 y 4294 H92] A display 429413 configured to visually y characters, Symbols, or images in response to commands received from the display driver 41292. For example. the display 4294 may be an eight—segment: display. in which. case the display driver 4292 converts each character or symbol. such as the figure “0”,, to eight. logical signals. indicating whether the eight respective segments are to be activated to display a particular character or symbol. .5.3 PAP device algorithms 4300 .5.3.1 I’m-processing module 4310 [1931 A pre—procegsing module 43101111 accordance with the present. technology receives as an input, raw data from a transducer. for example a1 flow or preseure transducer. and preferably perfemu; one or more s steps to calculate one or more output values that will be urged as an input to another mednle, for example a, therapy engine module 4320. {l 94] In ene form of the present technology. the output values include the interface or musk pressure Pm, the respiratory flow Qr. and the leak flow Q5. [1953 In various forms of the present technology, the rue-processing module 4310 comprises one or more 0f the 'l‘nllowing algorilhmaz Pl pressure estimation 4412. vent. llow 4414.. leak flow 41316, respiratory flew 4318., and jatnmhlg detection . .5.3.1.}. Respiratoryflow 4318 {196] As Shown in a model typical breath waveform in Fig. 6A, the magnitude of expiratory flow may not be constant: within a breath butter-1y vary over time. As; the magnitude of expiratory flow in as}; not be constant within a , determination of the expiratory flow rate as it varies may be desirable. In one form of the preeent technology, a atory flow tion algorithm 4318 receives as an input. a flow generator flow rater, QR}, a vent flow rate, Qvi and. a leak flow rate, QL and estimates a respiratory flow rate of air, Qt“, of the patient, by subtracting the vent flow rate Q15 and the leak flow rate Q! from the flow generator flow rate, Qm. {197] In some cases, such as when a vent valve 4450 blocks fluid communication. between the patient interface 3000 and the blower 4142, some or all of the above inputs such as the vent flow rate, Qt; leak, flow rate, Q1, or the flow generator flow rate, QR}, may not be available or do not correlate adequately to the respiratory flow rate3 Qr. In one form of the present technology, the atory flow estimation algorithm 4318 may comprise an expiratory flow model. EXPWGJ, to determine an expiratory characteristic Such as the respiratory flow rate, without direct measurement. The expiratory flow model, EXPm-lcr and/or the tory Characteristics ined using the expiratory flow model may also be used to determine the pressure in the patient interface 3000 as will be described in further detail below. {198] Fig. 9 shows one term of a typical breath flow wevefonn profile, wherein a e of the respiratory flow is not available during, the expiratory portion of the breath cycle. In such a case the expiratory flow rate may vary over the time of expiration, but may not be directly measured. In one form of the preeent technology, on expiratory flow model, EXPrmrgl. a5 shown in Fig. 10 may be used to estimate the expiratory flow rate and its variation across the time of expiration. {199] Using this form of the expiratory flow model, EKancg. an expiratory flow rate, Qexp, at a time T1 may be determined without a direct measurement. For example the expiratory flow rate, gem at the time T} may be determined based on its relationship to a reference time, such as a time olistart of tion Try, using the d time AT. Another suitable referenee time may be a time of end of inspiration; for example detected by falling of a atory flow rate to below a threshold level.

Alternatively: where the treatment system comprises allow Sensor 4274 and the variable vent 4400 compriaea a flexible divider vent valve 4460, ion of a decrease in the measured flow generator flow rate gm to below a threshold level for longer than a threshold period of time may determine a Suitable nce time. Levels of suitable threahold levels author the threshold period of time may vary according to each, ment of the technology. In another arrangement wherein the. treatment system ses a flow sensor 42.74 and the variable vent 4400 comprises a servo- controlled vent. valve 4452,.1‘eeeipt of a vent valve configuration signal. indicating a. configuration of the vent valve 4452, may ine a suitable reference time. For example, the vent valve configuration. signal may indicate that the vent valve 4452 is red to block flow between the blower 4142 and the variable vent 4000:. As a further alternative, inspiratory effort and/or expiratory effort may be detected, and the reference time may be determined based on the detection of an end of inspiration! effort andfor commencement of expiratory effort. Methods of detecting inappiratory effort andfor expiratory effort, as well as characteristics of inspiration and/or expiration deacribed in PCT application publications number Wt) 20061079152, W0 2010/1233 13 and/or W0 20] 21024733, all of which are inco'qiorated herewithin by reference? may also be used to detorniine a. suitable refer nice time. {200] In one form of the expiratory flow model, EXPmdal 213 shown in Fig. 11, the expiratory flow rate, QM. at a time, Tan may be estimated based on how much time has passed since the start of expiration of the current breath, TEMP The time between Tm and TESW may ha referred to as the change in time, AT 1. The corresponding change in flow- rate, AQ], at time AT; may be obtained from the expiratory flow model, L and used to estimate Qm. Similarity, the ponding flow rate an at a time Tm may be estimated by the change in flow rate AQQ. at a change in time ATg from the expiratory flow model EXP1M131.. {201] The expiratory flow model, EXPSEEML may comprise efifecta of or be d with some or all of the following parameters of the respiratory system andi’or the pneumatic path of the treatment ayatem: parts of the patient’ a respiratory system, leak flow, the t interface 30.00, the air circuit 4170, the. vent 4400 and/or the vent valve, 4450. For oxamplei the ancei inertance artdlor compliance of the patient‘s reapiratory system, as well as a, ventilation volume, a tidal volume (ego the 2014/050315 measured inspired vnlume from the immediately ing inapiratory port‘ic‘n of the particular rcspiratcry cycle for which the tory model will be applied), a peak inspiratory How, an average length of time in inspiration, 21 length of previmis inspiration, 51 lung ance and/’ur a lung ance may be included in the expiratory I‘lleCl, as may be flew impedance of the air Circuit 4WD. the: flew impedance of the variable vent 451L063 author the flaw impedance of the vent valve 4450-. The expiratory flow modeL EXPHMA, may comprise a sub—ritodel such as a model of the respiratt‘uy system of the patient 1000, which may comprise Due 0r more at the parameters of the re spiratory system. Another term (if a suitable sub—model may be 21 model of the pneumatic path. of the treatment system including such components 213 the patient, interface 3000, the air circuit 4170, the variable vent 4400 antifm‘ the vent val we 4450. Any single or ccmbinaticn Of the preceding parametem may be included to modify the expiratory flew model, g. It would be understand by those skilled in the art that the expiratory flow model may alsn be built or calculated based on other pm‘ttmetcra r characteristics. {2012] It shuuld he noted that the term, impedance in the context of this ication in on to the treatment system, and in particular in relation to: the le vent 4400, is used to primarily refer to resistance unless stated otherwise. In the art, the term impedance may be used as a combination of rcaistance, cmupliance and inerlance. However, in the context of this specification-t nce is primarily used :0 refer to resistance. Furthermore, as will be described below, the term nce is primarily used in cannection with the treatment. syatemr Where the effect of system. compliance and inenance may be neglected in some modelling methods. {203] Accordingly, the expiratory flow model, EXPdeL may be used in determine ether expiratory chm‘actcristiea than the cxpiratcry flow rate. For example. the expiratory flow model, EXPHMCJ, may be used to determine the pressure in the patient: interface 3000, such as fur controlling expiratury pressure based On the determined re or determining :1 target, setting for expiratnry pressure baSEd on the determined pressure, or the phase of expiration. flu acute cases, one or more aspects of the expiratory flew model may be determined based on a measure of the patient’s respiration, such, as a. e of inspiralinn, For example, a measure of ventilation velume, tidal volume, peak inspiratcry flew andfer a, length of time in inspiration. Also measures of lung compliance and/0r lung resistance may be used in the model. {2043 Figs. 11A and MB illnetrate additional models that may he detennined/eelculated anti/0r applied in same versinne 0f the present technology. In this regard, the previnusly diseussed model of Fig. it ie calculated to more closely mndel a flow verse time curve of typical patient expiration. in Figs. 1 1A and: 1 118. a sloped and/0r stepped model is applied such, as in a linear fashion. In some cases, the model may he formed based en values sensed during the inspiratory pertinn 0f the breath (erg, inspiratory volume and time) when the distally located sen anr (e.g, at or near the blower) represents cenditiens of the patient interface. Fer example, the slepe and amplitude of the model of Fig. 11A may be determined such that the expiratory volume of the ed sawtooth equals the measured inspiratery velume and the tory time (if the ed sawtenth is a prepnrtinn of the measured inspiratory time. Similarly, the inverted step function of the model Of Fig. ll B may be determined Sthil that the expiratory volume of the step equals the ineaeured inspiratnry volume and the expiratory time for the step is a ti 011 of the measured inspiratery time. {205] .Aeeenlingly, in the example of Fig. 11A,, the expiratory flow rate, light. at a. time, Tm, may be estimated based 011 how mueh time Tm has passed since the start of expiration of the current breath, TEng—L according re a desired slope Such as determined from a maximum expiratnry flew rate A necurring at Tmm and a desired expiratory flow rate decrease angle (ll (egg elnpe). Similarly, the ceneepending flow rate QM at a time T5; may be estimated from. the maximum expiratnry flow rate A by the flew rate decrease angle and a time change each as a change in time AT; ing to the tory flow mettle! EXngdEg. {206] By way of further example in Fig. 118, the tory flow rate at a time, T515 may be estimated based an a square wave given how much time Tm. has passed since the start of expiration of the current , Trim“ according to a desired time and amplitude characteristic: of the Square wave such as determined from it maximum expiratnjry flew rate A occurring at, Tfism. Similarly, the een‘espending flow rate at a time T53 before inspiratien may be estimated frem the square wave expiratery flow medel cl so as it} have for ex ample, a nominal or here flow rate. .5.3.1.} Respiratory circuit model {207] The prior art ture donorihos numerous methods of varying complexity to model the respiration system. The choice of one particular model. over another may depend on each model's properties such as its perceivod strengths and weaknesses. In one form. Lorino at al. discuss three: ly used Vince—elastic models: the Monti, Otis and Mount models. Rodurte. and Render suggest that a lung model based on the Mead modal may be suitable for uso in u control algorithm. As discussed by Loriuo ot a}... visco—olastic models are Ct'lmfllt'fl'lly used to model systems involving mechanical ventilation. Common models, such as tho Mead. Otis and Mount models involve the combination of Maxwell and Kolvin bodies in different arrangements. One advantage. of visoo—ulastic models. from a control systems. perspective, is said to he that it. may be readily characterized by a lineor tiltlorontiul equation. A. visco—olustic model may he usod in one form of the atory circuit model; however a. person skilled in the art would undnrstnnd that other forms of the respiratory circuit models would be suitable for use. with tho prosunt technology. {208] In one. form. Rodurtu and Rohdor model the properties of a lung as an electrical circuit. Fig. 12a shows a simplified entation of a lung whore tho lung is reprosontod as a Single compartment. mechanical model. Using this model. airway resistance: (RAIRWAYJ is analogous to an Electrical or. lung compliance (C1‘1_1Ng)ls analogous. to oupucitunce and airway inortanco ) is analogous to inductance.

Patient. oft’tu‘t, that is. the action of the muscles to chungu lung volumu can he. modollod as a pressur‘t source acting on the passive elements in the system- The model can then be ented as an electrical circuit as shown in Fig. 1217. {209] Thu Ct‘mtribution of airway inertia it; d to the density of air and no this value may be assumed to be a constant. Under this assumption. the remaining variable parameters for each t 1000 under steady state ions are lung compliance (CLuml and airway resistance (RAJRWAY). In one form. values of lung compliance (CLUNG) and airway ance (Rumour) inod for tho spottific potiont. 1000 may be used, for example haunt] on measures of respiration. or by providing input values unique to each patient 1000, such as their height, woighl andior modicul conditionn. In another form. lung, compliance (CmNg) and airway resistance (Kimmy) may be modelled as generic: values. for example based on median values across a population of interest. Cine exemplary set of suitable values of above parameters may he hung compliance NG) of 30 ml/emHgO, airway resistanee (RARE/7M) of 2.5 cmH-gOfl-I‘s, and airway ineitanee {LAIRwAy) of 0.014 cmHgOflfS/s. {21m According to one aspect, the respiratory circuit model may comprise effects of the inepiratory muecie activation, ably only during a part of expiration such as the first third of expiration where its effect is not negligible. Mueeie activation may act as a limiting force on the development of the peak expiratory flow by Slowing the initial expiratory flow from the lungs. This muscular contribution may be included in the respiratory circuit model as a time—variant non—linearity in, one term. In some forms, effects of the inepiratory muscle activation may be omitted from the respiratory circuit model. [2111 in one form the following model may be formulated to determine the pressure at the entrance of the atory circuit (P) based on the lung compliance {Cwmx aima); ance (RAmwpfli, airway ineltia (LAIRWW), volume of the respiratory t (VRggp). rate of change (first derivative) of the respiratory eireuit volume (93%;!) and the rate of change of the rate of change (second derivative) of the atory circuit volume (VRESP :1.

P = VR135}?n + RAIRWAY,V.are? i- I'wmrArVRESPt (HQ-1} CLWG The above differential equation may be then solved to eontroi the pressure in respiratory circuit, and in turn eontmi the pI‘CSSHI‘E in the patient interface, as they are in. fluid communication with each other. The above ation neglects the effect of muscle activity such as inspiratory muscle activation, and it may be modified to incorporate the effect of muscle ty in Some cases. For example, pressure due to muscle ty E’Mm may he inefiuded by modifying the above formulation as follows.

ID “—“ VRESP + RAIRWAYVRESP + LAIRWAYVRESP + PMu‘s (HQ-2} CLUNE The rate of change of the respiratory circuit volume (VRESP) may be the same 215 the respiratory flow rate Qr in. some cases. {212'} In the above model the terms airway resistance and lung compliance may be taken to mean the total lent values of resistance and emnpliance for the entire respiratory system, Hewever. in some cases the values may be derived l’rem a mine complex model in which the impedance is broken up inte a finer resolution.

The upper respiratnry tract. including the mouth. nose and larynx may else contribute tn the resistance and cemplinnee affecting the air path and may change depending on the breathing route utilized by the persen. In some cases it may be desirable te- separately model the upper and lewer airway resistances, and/er tn made] them. differently according tn the direction of the alory flew. Accordingly. their effects may be further included in the respiratory circuit model in. same cases. {213] In some cases, the expiratory portion of a breath may not follow a predictable pattern. Airway obstructions such as those caused by asthma, C(IIPD or anxiety may result in a. ing pattern that may not be passive and so fellow a different expiratory pattern. The prior art literature indicates that there may he a number of measures such as inspiratien time and peak ,iuspiratnry flow which can be indicative of different: breathing patterns. The expiratnry flow model may include the above measures for ed performance where such irregular tory patterns occur. The Phyxinlrigy Handbook ~— The primmry System is an example of prior art that details how breath patterns change in different clinical ions and exemplary indi ‘ators of these conditions. .5.31.3 Ventflow algorithm 4414 {214] In one fenn of the t technology a. vent flew estimation n1gnrithm 4414 receives as an input. an estimated pressure. Pm. in the patient interface 3000 and estimates a vent flow of air. Qv, frrnn a continuous vent 3400. such as a fixed continuous vent. {215] In annther term (if the preeent techunflogy. the vent flew estimation thm 4414 receive; as an input an estimated patient respiratory flow rate, and estimates a vent flow of air. Qv. The vent. flew estimation algorithm 4414 may also receive further inputs in estimating the vent flow of air, such as a, flow impedance of the variable vent 4400. the vent valve 4450., and/or an estimate re in the. patient interface 3000. The flow impedance of the vent valve 4450 may have a. significant effect on the total impedance t0 the flow of exhaust. gas. In. te terms of the present technology as described above, the flow impedance of the vent valve 4450 may be variable, in arrangements that use a servo-centrelled vent valve 4452 or a flexible divider vent valve 4460. In sueh eases, the effects of vent valve flew impedance may also be included in the vent: flew tinn algorithm 4414., {216] The vent flow may be also determined in some cases using the expiratory flow , EXPWXM, such as when the vent valve 4450 blocks fluid communication n the. blower 4 l 42 and the variable vent 4400, while allowing fluid communication between the variable vent 440i) and the patient ace 3000. In this case, as shown in Fig. 15, the vent flow, Q‘V, may be determined by subtracting the leak flew, Qt, from the expiratery flew rate! Qem which may he determined frem the expiratory flow estimation algorithm 4318. .5.31.4 Patient interface (PI) pressure estimatinn. 4412 {217] A PI pressure estimatinn algorithm. 4412 estimates the pressure in the patient interface 3000, and provides as an output an estimated pressure, Pm, in the patient interface 3000. {218'} in one term of the present technology the PI re estimatien algorithm 51412 receives as an input :1 Signal indicative of the re in the pneumatic path proximal to an outlet of the pneumatic black 4020. The PI re estimation algnrithm 4412, may determine the pres 51er in the patient interface 3000 based en a enn'elatinn between the pressure in the pneumatic path proximal to an Outlet of the pneumatic block 4020 and the pressure in the patient interface 3000. in, one arrangement. (if the present teehnningy, the cen‘elntien between the preesure in the tic path proximal tn an eutlet 0f the pneumatic blnclt 402i) and. the re in the patient interface 3000 may be ted in the form of a pressure drop in the air circuit 41’20. In Some. eases the combination, 0f the flow through the variable rent 44th and the leak flow may aeeeunt. for all of the impedance from the patient interface 3000 to atmnsphere, and in such cases the prensnre in. the patient. interfaee may be represented as a functien of the respiratory flew, the leak flewg and the variable vent 4400 impedance In this situatinn ltnnwletlge of the le vent 4400 impedance along with a good estimate of the atory flow and the leak flew may be adequately used to determine the pressure in the patient interface 3000. {219'} In another arrangement according to the present technology. a vent valve 4450- may selectively block fluid communication between the pneumatic block 4020 and the patient interface 3000. 'In such an arrangement, the pressure in the pneumatic path proximal. to an outlet of the pneumatic block 40201113}; not have a correlation to the pressaie in the tsinterface 30th). The PI pressure estimation algorithm 4412 may use correlations to other parameters to determine the pressure in the patient interface 3000. In some forms, the Pi pressure tion tflgorithm 4412 may meive as inputs outputs produced by the expiratory flow model andfor the respiratory circuit model. In other forms, the PI pie saute estimation algorithm 4412111213 se parts or the entirety of the empire;tori»r flow model, andfor the respiratory circuit model... {2120] Examples of parameters or characteristics that may affect the pressure in the patient interface 3000 include total nce to the flow of exhaust gas and the magnitude of expiratory flow. There may also '13 > any number of other parameters andfor characteristics which may he used to determine the pressure in. the patient interface 30%, such as. but not limited to, those used above in the expiratory flow model andfor the respiratory circuit model. Namely, lung ance (Cornet airway resistance (RMRWAYL airway inertia (Laggwgy), volume of the atory circuit.

(VRESP), rate of change of the respiratory circuit volume (Vans? ), the rate of change- of rate of change. of the respiratory circuit volume (VRESP) and effect of muscle activity. ance and compliance of other parts of the respiratory circuit. such as the upper respiratory tract, including the moo 11h, nose and larynx may also be included, Any other components of the treatment system such as the air circuit 4170, t interface 3000 and/or the variable vent 440011121}? also be characterised based on its own resistance, ance and inertia: and added to the model as required. {221] One form of the PI pressure tion thm 4412 may be as follows: Pm : 5%;er + RTUTV’I’OT + Lrorih'cr (EQ- 3) lathe shove equation, RTCIT ents the combined resistance of the following components: the respiratory system, the patient interface 3000, the air circuit 4170 and the variable vent 4400. Gym represents the. combined resistance of the following components: the respiratory system, the patient ace 3060, the air circuit. #170 and the variable vent 4400. LTOT ents the combined inertance of air in the following components: the respiratory system, the patient interface 3000, the air en‘cuit 4170 and the. variable vent 4400: VTOT represents the combined volume of the. following components: the respiratory system. the patient. interface 3000, the air t 4170 and the variable vent 4400. V703“ and V797 ent first. and second derivatives of Vror- The terms R'}_‘(}r‘[‘, 01m nndfor L<[‘()v;\n1aybe constants in some forms of the t technology; r they may be. variable in other forms‘ For instance, the term Run may vary to indicate the varying nce of the variable vent as will be described in further detail below, In some forms of the present. technology, the terms RTQT, CTQT and/or Iii-my may be predetermined, however they may alto be determined. for each patient, for example uning a measure of respiration of the patient; or during a calibration phase. In some arrangements of the present technology, the compliance and/or inertanee of components of the treatment, system. such as the patient. interface 3000, the air eireuit 4170 and the variable vent 4400 may be relatively small in relation to the compliance andi’or inertanee of the atory Circuit. Accordingly the. values of compliance ttndior nee of the respiratory circuit may be suitable representative values for combined ance r inertunce. One e set of le values of above parameters may be combined compliance (Cm-I) of 30 nil/enngD, combined resistance (Rm-11] of 5 cnngOXl/n and combined inertance (her) of 0.014 (:th 2.0.1113}s. {222] In one. ffll‘m, the P]: pressure estimation algorithm 4412 may operate based on the above equation (Eq. 3) by implementing an iterative solution with constant values of Crop Rim, LmT, Vror: providing an initial estimate of Viv)? and solving for Wm to determine an updated value of life-r. One suitable initial entimate of Vror may be a product of the pressure of the [low of breathable gas and the combined compliance. The updated value of WOT may be fed back into the control nystem to update the value of VT” by the integral, of VTOT» such as the product of frequency of the iterative on and the VTQT. Similarly, er may be updated by the integral of Vror: such as the product of frequency of the iterative solution and the VFW. li‘223] According to one arrangement of the present technology, the majority of the expiratory flow may be exhausted as a, flow of exhaust gas through the variable vent 4400. Also: the total impedance to the flow of t gas may correlate strongly to the flow nce of the variable vent 4400. In such an arrangement, a suitable PI pressure estimation algorithm 44.12 may comprise the. effects of the flow impedance of the variable vent 4400 andi’or the effects of the magnitude of exhaust flow h the le vent 4400 to determine the pressure in the patient interface 3000.. for example by knowing leg, by determining the patient. interface pleasure (PD) the value of Rwy. in. this arrangement it follows that the pressure. in the patient. interface 3000 may be controlled by naming R1931. {224] In amtngements where a servomontrolled vent valve 4452 is used, the Pl pressure estimation algmithm 4412 may comprise an indicator of the impedance of the sewn-controlled vent valve 4452.. Some of the suitable indicators of the impedance of the controlled vent valve 445?.- may comprise a on of a. movable component of the servoweontrolled vent valve 4452 or a position of an actuator configured to drive. the servrncontrnlled vent valve 4452. [2251 in one form the flexible divider vent valve 4460 may comprise a membrane 4462 as Shi‘in‘l in Fig. 8A and Fig. 8B, whose deflection may affect the flow impedance. In some airangernents, the blower 414:2 may be used to change a presSure en a first side of the membrane 446:2 thereby changing the pressure ential and thus deflection of the membrane as deselibed in further detail abnve.

According to this form, it may be appropriate for the PI pl‘SSS are estimation algorithm, 4412 to comprise the s of pressure on the blower side of the membrane. One suitable signal that. is indicative of pressure on the blnwer Side of the membrane may be a signal of a oual speed of the blower. Others may include a signal of pres sure measured between the blower and the membrane 4462, a signal of deflection of the membrane 4462, or a signal. indicating the ical current that: is drawn by the blower, although any number of other signals may be possible. The PI. pressure tion algorithm 4412 may also se a signal that is tive of the differential pressure between the first side and the second side of the membrane 4462., such as a strain on the membrane 44625 or an optical 'rneasurement of the deflection of the membrane 4462.. {226] it should he understood that a ‘model’, in the present context, as. in ‘expiratory model’ or ”expiratory flow tnntlel’, may be implemented in one or more of a variety of forms known to those skilled in the art. For example, a model may be based on a single or imensional look-up table, such as one with pie—calculated or predetermined values of the above relationships or equation-s, wherein one or more input parameters are used to find, or ‘iook~np’ an output value. Alternatively, a model may be. based on a mathematical relationship such as, but not limited to a single or mnlti—vuriable equatinn, which may inelude linear, polynomial, exponential, logarithmic, nr an 3; number of other former .5.3.1.4J Variable flow impedance vent {22?} ing to some arrangements of the present teehnology, the flow impedance of the variable vent 4400 auditor the vent valve 4450 may be variable as described. in greater detail previously. In such arramgementsi the effects of variable flew impedance may be incorporated into the expiratory flow model andfor the Pl preseure estimation algorithm 4412i .53.1.5 Leak flow algorithm #316 {228] In one form of the present technology, a. leak flow algorithm 4316 receives as an input: a total flow, Q1, and a vent: flow Q13, and provides as an. output a leak flow Qt by calculating an average of Qr—Qv over a period Stiffieiently long to include several breathing cycles, eg about 10 s. {229] In one form. the leak flow algorithm 43,16 receives as an input a total flow, Q1, :1 rent flow Qv, and an estimated pressure Pm, in the patient. ace 300i), and provides as an output a leak flow Q! by calculating a leak conductance, and ining a leak flow Ql to he a function of leak tance and pressure, Pm.

Preferably leak conductance is calculated as the quotient of lnw pass filtered non-vent flow Qr-Qu, and low pass filtered square root of ure Pm, Where the low paras filter time constant has a. value sufficiently long to include several ing cycles, eg. about, if) seconds. {230] In another fonni the leak flow algnrithm 11416 receives as an input a respiratory flow Qr during expiration (nine referred herein as patient expiratory flow Qerp), and an estimated re, Pm, in the patient interface 3000, and provides as an output: a leak flow Q1. The leak flow algorithm 4416 may determine the .leak flow Q! by calculating a leak mndnetance, and determining a, leak flew Q] to be a funetinn of leak conductance and e, Pm as shown in Fig. 15. ing tn some arrangements {if the present logy; the leak flow algorithm 4416 may calculate leak conductance during an inspiratory portion, of the brfiath cycle. {231'} A basis of nnnther ‘i‘nrtn of“ a ieuk flow algorithm 4316 is shown in Fig. 14A—Fig. 143 Fig. MA shuws a ionger form (if a model typical breath wavefnnn as shuwn in Fig. 6A, shewing twn breath cyeies. The breath waveform shown in Fig. 14A; includes a nt leak; flow with magnitude Qmfl tn indicate a total flew rate QM, Que untemne nf such a ennstnnt leak is that the breath wuvefunn is shifted upwards by an offset with magnitude QM“. As described above, the variable vent vaive 4450- may be configured to block fluid cunnnunicatinn between the variable vent 4400 and the patient interface 3000 during inspiration. In the absence ui’ intrinsic PEEP ive End tury Pressure), which is a panticuiar patient eunditiun where the expiratory flow doesn’t approach zero at the end of expiration? at time Tuned-mm the patient respiratory flow Qr weuid be zere, and thus the total flow would be equal to the nt leak flow QM“. Thus the sensed flow at time gn would equal the leak flew QM“. in one faring the total flow rate at time Tinflgfljgn may be sensed by the flow transducer as total flew is positive and, thus the r 4142 would he in fluid centununicatinn with the patient interface 3000. The measured flow rate chas may appear as shown in Fig. MB. in this example. the time Tgnflmm may be determined by munittn'i 11g the rate tn“ ehange of the total flew QM, and finding the point of inflection (such as based on calculation of a second derivative and determining if it is zere, etci) where the uur 0f the respirutury system switches from expiration to inspiration and s an inflection point. In the presence of intrinsic PEEP. an estimate of the ntional leek, Qkfflk} may be determined by Subtracting an estimate of the magnitude ut‘ patient. flew at the paint of inflection Timmm from the total flow. .5.3.2 Therapy Engine Module 4320 {232] In one form Of the present teehnniugy, a therapy engine module 432() receives as inputs one or more hi" :1 pressure Pm, in. a patient, interface 300i}, and a respiratory flow rate of a patient, Qr, and pruvides as an uutput, une 01‘ more therapy parameters. {233] In one form uf the present technology, a therapy parameter is a CPAP treatment pres sure Ft, {234] In une form of the present technniogyt a y parameter is one er more of a level at pressure support, and 21 target ventilation. .5.3.2.} Phase determination 4321 {235] In ene form Of the present technelogy, the PAP device 4000 does- not determine phase.

In one form ef the present technology a phase determination algorithm 4321 receives :13 an input a signal indicative of atory flew rate. Qt». and providea as an (Jutput a phage of a breathing cycle of a patient. 1000. 237] In one farm, the phage Output is a discrete variable with values of either inhalation 01' exhalation. {238] In one farm, the phase output is a discrete variable with values of one of inhalation, midsinspimtnry pause, and exhalation. {239] In one form, the phase output is a continueus vm‘iable, fer example varying from 0 to 1, 0r 0 to 213i. [240} In one term, the phase output is determined In have :1 te value of inhalation when 21 respiratery flow rate Qr has a poeitive value that. exceeds a ve threslmld. In one form, a phase is determined to have a iiiserete value of exhalation when a respiratnry flew rate Qr has a negative value that, is more negative than a negative thresheld. {241] In seine forms, such a, process may be implemented for detennining whether 01’ not a sensor for sensing a gas Characteristic of the patient interface is; d such that the sensor may not get a measure indicative of the gas characteristic. This may occur when the blocking is cyclical or has phases, such as when the conduit to the sensor is subject to expiratory blocking with example venting apparatun described her‘tin (eg. any hi the valves of Figs. T’A-Tf‘B and SA—SC). Such a s may then serve as legie fer chnosing different see for system control given the cyclical nature of the citation 0f the sensor with respect [0 its ability to sense the. patient ace gas terinlie. Detection of such presence or absence of'hleeliing or expiratery blocking may be implemented with detention (if. for example, end Of inspiration or beginning of inspiration, such as lay evaluatinn of a measure of flow or pressure from, a signal from a. sensor and a, threshold. Other Similar detection precesses may 3130 be implemented. .5.3.3 Pressure control module 4330 {242] A pressure control module 4330 in accordance with. one aspect. of the present logy receives as an input a, target patient interface (Pl) pressure Pi; and controls a pressure device 4140 to deliver that re to the patient 1000. {243'} A pressure control. module 4330 in accordance with one aspect of the present technology receives as an input a target EPAP pressure and a target {PAP pressure, and controls a re device 4140 to deliver those respective preseurest {244] A flow chart. with, processes according to one form of the present technology is shown in. Fig. 13. In this example, a processor may be implemented with programming logic to select between different pressure detection andfor control proresses (6.01, second process 4412—A of Fig. l3 and first prncess 4412—8 of Fig. l3) depending on blocking and unblecking of a sensor's ability in detect a gas teristic of the patient ace. That is, when the sensor is blocked, the system is in a state where the sensor (eg. blowenproximate sensor) is able to measure pressure but the measured pressure no longer indicates conditions at the patient end of the therapy system. These ses may be cyclically selected such as in the case of cyclical blocking and unblocking (eigq inspirntory tin-blocking and expiratory blocking.) Thus, a re control of a controller, such as closed loop pressure centre}, may operate with different 0r alternating ons in conjunction with the selection of the multiple (”eg first and second) preces ses when the current measure of pressure, due to blocking, does not accurately reflect the system being controlled at all times. Such a system may central. pressure in the patient interface without a pressure sensor at or in the patient interface such as where the pressure sensor is located at or near the blower or flow generator, across a ry conduit and away from the patient ace when some system ent or variable condition may interfere tog. block) the detection of the patient interface condition te.g., presume) with the sensor. {245] For example, interface gas pressure in the t interface prcxitnate a patient airway may be determined in the first r 4412~B from a current measure of pressure from the sensor if the ccnduit to the sensor is unblocked (erg, at or during inspiration). Such. a determination of ace gas re may be made from a pressure drop associated with a delivery conduit characteristic and the current measure {if pressure. The first process may optionally determine a pressure ment for pressure in the patient intertaee than a difference between the in ee gas pleasure and a target pressure. {246] Similarly, interface gas pressure in. the patient interface proximate a patient airway may be determined in the second process , such as without a.

Current e of pressure from the sensor or a sensor near the patient interface, if the conduit to the sensor is blocked log, at or during expiration). In each a process, ace gas re in the patient interface proximate a patient airway may be determined from a modelled flow estimate in presence of bleaching of the conduit to the sensor tog, from. a respiratory flow estimation 4318 s} The modelled flow estimate may he an estimate of expiratory flow as discussed in more detail herein.

The detenninerl interface gas pressure may be ated from an elapsed time, such as by detecting an end of inspiration and from the expiratory flow estimate. The second proceSs may determine a pressure adjustment for pressure in the patient interface from a difference between the determined interface gas pressure and a target; {HESSUI‘E . {247] ally a common pressure control module 4330 may receive as an input a value of P] pressure from the Pl pressure estimation module 4412, {e.g., 441.2 A and/0144,1213). The pressure control module 43301112133 then compare the value of PI pressure to the target Pl pressure to determine a pressure error value and accordingly adjust. the PI pressure based on the pressare error value. {248] In one arrangement of the present technology, the pressure control module 4330 may Change the impedance of the vent valve 4450 to control the pressure in the patient interface 3000 as described in further detail above. {249} According to one fomi, the pressnr'i control module 4330 may receive as inputs signals indicating one or all of the following: flow impedance of the vent valve 4450, flow impedance of the le vent 4400 ancllor pressure in. the patient interface 300(1. .5.3.4 ion of fault conditions 434% {250] In one form of the present technology. a processor es one or more methods for the detection of fault conditions. Preferably the fault conditions detected by the one or more methods includes at least one of the following: 9 Power fail-tire {no power, or insufficient, power} -‘ Trttnadueer fault. detection ¢ Failure to detect: the ee of a, component ti Opemtitig parameters outside ended ranges (egg. pressure, flow, temperature. P2102) 0 e of a test alarm to generate a detectable alarm signal. {251] Upon detection of the fault ion, the coireeponding algorithm signals; the presen ee of the fault by one or more of the following: 0 Initiation of an, audible, vieual cider kinetic tog. vibrating) alarm * Sending a meseuge to an external device 0 Logging of the incident .6 HUMIDIFIER 5000 .6.1 Humidifier overview {252] In one town. of the present technology there is provided a humidifier SOGO comprising a water reservoir .5 l 10 and a heating plate 5120. The humidifier 50th may be a separable component to the PAP device 4001}. or alternatively may be integrally constructed with the PAP device 4000. .6.2 Humidifier mechanical components 511)!) .6.2.1 Water reservoir 5110 [.253] ing to one aspect of the present technology the humidifier 5000 comprises a water reservoir 51 It) as shown in Fig. 5b. The water reservoir 5 1 it) may be configured so that the flow of breathable gas would be further humidified as it. pauses through the interior of the water reservoir 5110'. {254] The oir 51 10 may be configured to hold, or retain, a body of iiq‘uid, such as water. The body of liquid is ated to add humidity to the flow of breathable gas, typically in, the reservoir 51,10. In some cases, the humidifier 5000 may he in continuous use fora period of up to several. houre. such as between four to ten hours. The oir may be configured to hold a predetermined maximum voiume of liquid of several hundred millilitres to provide humidificaiion for the duration of this period. {255] ing to one. aspect, the water reservoir 5.1 it) may provide an internal path for the flow of breathable gas to travel. between a reservoir inlet and a reservoir Outlet. In Some instances, the internal path for the flow of breathable gas may be arranged torment-11y to increase the time that the flow of breathable gas spends within the reservoir 5110 to increase humidity added to the flow of breathable gas. {256] The internal volume of the water reservoir 5110 may be arranged to reduce likelihood of any water being epiljled in the reverse direction, upstream. of the humidifier 5000. This may be done in one of a number of ways such as providing additional. internal volume, an elongated. intet tube, a native or a divider, so that any water contained within the humidifier 5000 would not reach the oir inlet at any orientation. {257] In some arrangements, the water oir 511.0 may comprise a conductive n configured to introduce heat to the oir 51 it). The conductive portion may be coupled with, a heating element 5240 to introduce heat to the interior of the water reservoir 5 l 1.0. Suitable materials for construction of the tive portion may include aluminium or another heat conducting material. In some forms, the water renervoir 5110 may comprise a heating element 5240. According to one arrangement, the g element 5240 may be moulded into a resin forming a. tub, as sed in the PCT patent application WC) EGGS/148154, the contents of which is incorporated herein by reference. .63.2.2 Heating plate 5120 {258] According to another aspect of the present technology, the humidifier 5000 may comprise a heating plate 51.20 which is used to transfer heat to the water reservoir 5110 an shown in Fig. 5b. The heating pinto 5120 may comprise a heating t 5240 located on or near the base of the humidifier 5000. The heating plate 5120 may he formed, for exarnptm of a nickel chrome alloy. stainless steel or ed aluminium.

U! U] .6.3 Humidifier Electrical 8; thermal components 5200 {259] A humidifier 5000 may comprise a number of electrical, andfor thermal. eotnponente such as those lieted below. .6.3.1 Sensors {250] A. humidifier 5000 may comprise one or more seusnra. such as an air pressure ts) 5210, an air flow sensort all a temperature sensorts) 5220 and/or a relative humidity sensorts). .6.3.2 Heating element(s) 5240 {261] The heating element 524D maybe a heat generating component. 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 ation Number Wt] 201.2/171072, the entire document of which is incorporated thin by reference. .6.3.3 Humidifier controller 5250 {262] ing to one arrangement of the present logy, a. humidifier 5000 may comprise a humidifier ller as shown in Fig. fat. The humidifier controller may be a part of the central ller, or may be a te llen which may be in ication with the central eontrnller. The humidifier controller may be configured to receive input signals from one or more sensors such as measures of characteristics of the flaw of breathable gas, measures of ehameteriatie of the water in the reservoir 5110, measures of characteristics of the reservoir 511001- measures of characteriatica (if the humidifier 5000. The humidifier controller may also be configured tn execute or implement humidifier algorithms andior deliver one or more output signals. The humidifier eentmller may comprise a heated tube controller configured to control the temperature of a heated tube andi’or a hot plate controller configured to 60:11:01)] the temperature of a hot plate. .7 HUMIDITY EXCHANGER {263] In one form of the t technology there a humidity eachanger may be implemented such at: described in Patent Cooperation Treat3' Patent Application Public-alien Number ‘WO 057592, which may be located n a variable vent 4.100 and the patient interface 3000. The humidity exchanger may serve to extract moisture from [he expiratory flow and return some of that. moisture to the inspiraiory flow. In one form the humidity exchanger may present significant impedance that. may be included in the above model for the purpose of ontimating the respiratory flow andfor controlling the patient interface 300i) pressure. In one form the. humidity exchanger nce may be considered to be ible and not included in the model. .8 BREATHING WAVEFORMS 6000 [2.64] A model typical breath waveform of a person while 816:3le g. is shown in Fig. 6A! While the parameter values may vary, a typical breath max have the following approximate values: tidal , Vt, (ESL, inhalation time, T3,, 1.65, peak inspiratory flaw one, Qpeak, 0.4 US, exhalation time, Te, 2.45, peak expiratory flow rate, Qpeak, —().5 Us. The total duration of the breath, Tron is about, 45. The person typically breathes at a rate of about i5 breaths per minute {BPML with minute ventilation, or ventilation, Vent; aboul 7.5 L/minute. A typical duty cycle, the ratio of Ti to Trot is about. 40%. .9 GLOSSARY [2651 For the purposes of the present technology sure, 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, .9.] General {266] Air: In n. forms of [be present technology, the term ‘air’ may be used iniet‘cliangeably with “breathable gas’ Typically, air euppliecl to 21 patient may be atmospheric air, and in other forms of the preccnt logy atmospheric air may be supplemented with oxygen. {267] Continuous Positive Airway PFBSSEH‘E (CPAP): CPAP ent will be taken to mean the application of a supply of air or breathable gas to the entrance to the ahways at. a pressure that: is continuously positive with respect to a reference pressure lly atmospheric pressure .9.2 Aspects of PAP devices {268.} ARA 1": Automatic Ptisitiva Airway .‘Presmwa. Positive airway pmssure that is continually adjustable between minimum and maximum limits, depending on the ‘pl‘eSBHCG or e of tions 0f SDB wants. {2693 Therapy: Therapy in the present context: may be one 01‘ mate of positive pressure therapy, 0);}!an therapy! carbon lc thcrapy; control of dead space, and the administration of a drug. .9.3 Aspects of the respiratnry cycle {2170] Breathing rate: The rate of spontaneous respiration, (if a patient, usually measured in breaths per minutet {271] Emit-an»)! portion nfa breathing mic-1:2: The period from the start: at axpiramry flaw t0 tha- start of inspimtm‘y flew. {272] Impimmry portimz Qf'a breathing cycle: Pi‘efm‘ably the period from the start of inspiratot‘y flaw t0 the start of expiratory flaw will be taken to be the inspiratnry portion of a breathing cycle. [273} Tidal volume (VI): The: volumc of air inhaled or exhaled during normal breathing, when extra effort is not applied. ‘ rat-1 l; 14] Inhalation time (Ti): The duration of the inspiratnry pt‘irtion of the ‘atmy flow waveform, also refettmd to as length of tion or length of inspiration. {275] iintian time (Te): The nn of the expii‘al‘niy pm‘t‘inn (if the. respiratciry flow wavefnnn, 21150 referred to as length (if sxhalatinn or lsngth (if expiraton. [2761 T01:12 time ( T203): The total dLII‘fliiGl't n the start of the inspiratnry portion of one respiratory flow waveferm and the start. of the innpimtni‘y portion of the f0‘llowing respiratory flow waveform. {27?} l rec-em inemilmianz The value of“ ventilation around which recent values over some predetermined timescale tend to r, that is, 3117182181er of the central tendency of the recent vnlneg of ventilation. {278] Upper halfway obstruction (HAD): inclnden both partial and total upper airway obstruction. Thin may be associated with a. state of flow limitation, in which the level 0f flow increases only slightly or may even decrease as the preesure ence across the upper airway increases (Starling resistor behaviour). {279] Vrnzrilminn : A measure of the tntal amount of gas being exchanged by the patient‘e respiratory system, including both in spiratory and expiratory flow. per unit time. When expressed as a vnlume per , this quantity is often referred te 213 e ventilation”. Minute ventilatinn is sometimes given simply as a volume nnderstoncl to be the volume per minute. .9.4 Anatomy of the atory system {280] Diaphragm: A sheet of muscle that: extends 11017053 the bottom of the rib cage. The diaphragm sept rates the thoracic cavity, containing the heart, lungs. and ribs, from the abdominal . As the. diaphragm et‘mtraets the volume of the ic cavity increases and air is drawn into the lungs. {281] Lmym: The larynx, or voice box houses the vocal folds and connects the inferior part of the pharynx (hypopharynx) with the trachea. {282] Lungs: The organs of respiration in humans. The conducting zone of the lungs contains the trachea, the bronchi, the bronehiolee, and the terminal bronehioles.

The reepiratery zone contains the reepirntory brenehinles, the alveolar ducts, and the alveoli. {283] Nam! cavity: The nasal cavity {or nasal loss-(1) is a large air filled space above anti behind the nose in the middle of the face. The natal entity is divided in two by a vertical fin called the nasal septum. 0n the sides of the nasal cavity are three horizontal outgrowths called nasal eonehae (singular "conclia“} er turblnntes. To the front at the nasal cavity is the nose. While the hack blende, via the ehoanae, into the nesophmynx. {284'} lerynx: The part of the throat ed immediately or to (below) the nasal cavity? and superior tn the, oesophagus and larynx The pharynx is conventionally divided into time sections: the nasophnrynx {epiplmrynx} (the nasal part of the pharynx), the oroplrarynx (mesonharynx) (the oral part of ll’lfi x), and the laryngopharynx (hypophnrynxl .9.5 Aspects of a patient interface {285} Amivcmphyxia valve MAX/3); The comprment or sub-assembly of a mask system that, by opening [:0 atnmsphere in a failsafe manner, reduces the risk of excessive, CO; rebreathing by a. patient {286] Elbmt’: A t that directs an axis of flow of air to change direction through an angle. In one form, the nngln may be approximately 90 degrees. In another form, the angle may be less than 90 degrees; The conduit may have an approximately circular cross—section. In another form the conduit may have an oval or rectangular crass-section. {287] Frame: Frame will be taken to mean a mask structure that bears the load of innsion between two or more points of connection with a headgear. A mask frame may he a nonunirl‘lght load bearing structure in the mask. However, some forms of mask frame may also be air-tight. {288] Hréadgmr: Headgear will be taken, to mean a form of positioning and stabilizing structure. dcsigned for use on a head. rahly the ear comprises a tion of one or more strutsg ties and stiffcncrs nonfignred to locate and retain a patient interface in position on n paiient’s face for delivery of respiratory therapy.

Some ties are formed of a soft, flexible, elastic 1n alerial such as a laminated composite of foam and fabric. {289] Pimnm chamber: a mask plenum Chamber will be taken to a. mean portion of a patient interface having walls enclosing a volume of space, the volume having air therein pres surised above atmospheric: re in use, A shell may form part 0f the walls of a mask plenum r. In one form, a region 01:31th patienl"s face forms 0116 of the walls of the plenum chamber. .10 OTHER REMARKS {290] 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 whatsoev if. {291} 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, n 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 lot 'et limits of these intervening , which may be independently included in the intervening ranges, are also eneompasned within the technology, t to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limitst ranges excluding either or, both of those included limits are also included in the technology. {292] Furthermore: where a value or values are. stated herein as being ented 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 icant. digit to the extent that a practical technical implementation may permit. or require it. {2931 Unless defined otherwise, all technical and ific terms used herein have the same meaning as commonly understood by one of ordinary skill in the an: to which this technology belongs. Although any methods and materials similar or equivalent to those deserihed herein can also be used in the ce or testing of the present logy, a d. number of the exemplary methods and materials are described herein. {294-} When a. particular material is identified as being preferably used to construct. a component, obvious alternative materials with similar properties may be used as 3 Substitute. Furthermme5 unless specified to the thnttrz‘iry5 filly and all components herein described are understood to be e of being manufactured and, us such, may be manufactured together or separately. {295] 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 utherwise. {296] All ations mentioned herein are incorporated by“ reference to disclose and describe the methods author materials which are the. subject. of those publications. The publications discussed herein are provided solely for their disclosure prior to the filing date of the t ation. Nothing herein is to be construed as an admission that the present technology is not entitled to te such publication by virtue. of prior invention. Further, the dates of publication provided may be ent from the actual publication dates, which may need to be ndently confirmed. [2971 Moreover, in interpreting the. disclosure, all terms should be interpreted in the broadest able manner consistent with the context. In particular, the terms “comprises" and "comprising" should be interpreted as referiing 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. {298] The subject. gs used in the ed descriptinn 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 gs should not be used in construing the scope of the Claims or the Claim limitations. {299] 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 temis "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 ts, 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. recognise that such ordering 2014/050315 may be modified and/m“ aspects (hareof may be mnduclsd concurrently or even onously. {300] It is therefore to he understood that numerous ations may be made to the illusstral'iva embodiments and that othm‘ arrangcmsnts 111 ay be devised without disputing frmn the spirit and scope 0f the tcclmolngy. 6 CITATIGNS 6.1 NON—PATENT LITERATURE {301] Latino, AM... Hi Latino, and A. Harf, A symiwsis qr" the Otis, Mead, and Mount mechanical aimfiy nizx'nieish. Respiration P11ysiniugy. 97(2): p. 123- 133. [302} RQdI-n'te, JR. and. K. Rshdsr, Dymmiim QfRaspirmioH, 1’7? kuflmok cg“ Physiology — The! Rexpimtmy System. 2011, Williams and Wilkins; Baltimore. p. 13] — 144. {3033] Handbook aff’kysioiagy - The: Respiratory System, ed. J] WCSL 2012: John Wiley 8:; Sans, Inc.

Claims (30)

CLAIMS :

1. An apparatus for controlling a supply of breathable gas at a positive pressure for treatment of a respiratory disorder, the apparatus comprising: a controller, ing at least one processor, adapted to control setting of a blower of a therapy apparatus for controlling a supply of breathable gas at a controlled pressure above ambient in a patient interface, the controller coupled with at least one sensor for the therapy apparatus, the at least one sensor configured to measure pressure through a conduit from the therapy tus to the patient interface, the t in fluid communication with the patient interface, the patient interface ured to deliver the supply of breathable gas to an airway of a patient, the controller being further configured to determine gas re in the patient interface using a first process when the conduit to the at least one sensor is blocked and using a second process when the conduit to the at least one sensor is unblocked.

2. The apparatus of claim 1 n the first process comprises determining the patient interface gas pressure from a current measure of re from the at least one sensor when the conduit to the at least one sensor is unblocked.

3. The apparatus of claim 2 wherein the first process comprises determining the patient interface gas pressure from a pressure drop associated with a delivery conduit characteristic and the current measure of pressure.

4. The apparatus of any one of claims 2-3 wherein the first s comprises determining a pressure adjustment for pressure in the patient ace from a difference between the determined patient interface gas pressure and a target pressure.

5. The apparatus of any one of claims 1-4 wherein the second process comprises determining the t interface gas pressure from a ed flow estimate when the conduit to the at least one sensor is blocked.

6. The apparatus of claim 5 wherein the modelled flow estimate is an expiratory flow estimate.

7. The apparatus of claim 6 wherein the determined patient interface gas pressure is calculated from an elapsed time and the expiratory flow estimate.

8. The apparatus of claim 7 wherein the second process comprises determining the elapsed time by detecting an end of inspiration.

9. The appara tus of any one of claims 5-8 wherein the second process comprises determining a pressure adjustment for pressure in the patient interface from a difference n the determined patient interface gas pressure and a target pressure.

10. The apparatus of any one of claims 1-9 wherein the controller is further configured to determine the gas pressure in the patient interface by cyclical selection of the first s and the second process.

11. The apparatus of claim 10 wherein the controller selects the first process upon determination of patient ation.

12. The apparatus of any one of claims 10-11 n the controller selects the second process upon determination of patient expiration.

13. The apparatus of any one of claims 1-12 wherein the controller is further configured to determine an ntional leak flow by subtracting a magnitude of patient flow at a ined point of inflection of a total flow from the total flow.

14. The apparatus of any one of claims 1-13 further comprising the blower.

15. The apparatus of any one of claims 1-14 further comprising the patient interface and the conduit.

16. The apparatus of any one of claims 1-15 further comprising a valve ured to selectively block expiratory gas communication to the at least one sensor.

17. A method of operation in a processor for determining settings of a blower of a therapy apparatus for providing a supply of breathable gas to a patient interface at a controlled pressure, the method comprising: with a sensor of the therapy apparatus, measuring a pressure through a conduit from the therapy apparatus to the patient interface, the t in fluid communication with the patient interface, determining a patient interface gas pressure for determining settings of the blower using a first s when the conduit to the sensor is blocked and using a second process when the conduit to the sensor is unblocked.

18. The method of claim 17 wherein the first process comprises determining the patient interface gas pressure from a current measure of pressure from the sensor when the conduit to the sensor is unblocked.

19. The method of claim 18 wherein the first process comprises determining the patient ace gas pressure from a pressure drop associated with a delivery conduit teristic and the current measure of pressure.

20. The method of any one of claims 17-18 wherein the first process comprises determining a re adjustment for pressure in the patient interface from a difference between the determined patient interface gas pressure and a target pressure.

21. The method of any one of claims 17-20 n the second process comprises determining the patient interface gas pressure from a ed flow estimate when the conduit to the sensor is blocked.

22. The method of claim 21 wherein the ed flow estimate is an expiratory flow estimate.

23. The method of claim 22 n the determined patient ace gas re is calculated from an elapsed time and the expiratory flow estimate.

24. The method of claim 23 wherein the second process comprises determining the elapsed time by detecting an end of inspiration.

25. The method of any one of claims 21-24 wherein the second process comprises determining a pressure adjustment for pressure in the patient interface from a ence between the determined patient interface gas pressure and a target pressure.

26. The method of any one of claims 17-25 further comprising cyclically selecting the first process and the second process.

27. The method of claim 26 wherein the first process is selected upon determination of patient inspiration.

28. The method of any one of claims 26-27 wherein the second s is selected upon ination of patient expiration.

29. The method of any one of claims 17-28 further comprising determining an unintentional leak flow by subtracting a magnitude of patient flow at a determined point of inflection of a total flow from the total flow.

30. The method of any one of claims 17-29 wherein the t interface ses a valve configured to selectively block expiratory gas communication to the sensor.