Flow element and method of manufacture

Abstract

A flow element for a respiratory pressure therapy (RPT) device is disclosed. The flow element comprises an outer housing and an insert, wherein the insert and housing together define a plurality of flow channels within the housing. A transverse cross-section of the insert defines a simple open curve. The insert has a first side and an opposite second side, wherein the insert is configured such that any notional line in a predetermined direction intersects the first side of the insert only once and intersects the second side of the insert only once. A method of manufacturing the flow element is also disclosed

Description

FLOW ELEMENT AND METHOD OF MANUFACTURE1 CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Australian Provisional Patent Application No. 2024902060, filed 4 July 2024, the contents of which is incorporated herein by reference in its entirety.2 BACKGROUND OF THE TECHNOLOGY2.1 FIELD OF THE TECHNOLOGY

[0002] The present technology relates to one or more of the screening, diagnosis, monitoring, treatment, prevention and amelioration of respiratory-related disorders. The present technology also relates to medical devices or apparatus, and their use.2.2 DESCRIPTION OF THE RELATED ART2.2.1 Human Respiratory System and its Disorders

[0003] The respiratory system of the body facilitates gas exchange. The nose and mouth form the entrance to the airways of a patient.

[0004] The airways include a series of branching tubes, which become narrower, shorter and more numerous as they penetrate deeper into the lung. The prime function of the lung is gas exchange, allowing oxygen to move from the inhaled air into the venous blood and carbon dioxide to move in the opposite direction. The trachea divides into right and left main bronchi, which further divide eventually into terminal bronchioles. The bronchi make up the conducting airways, and do not take part in gas exchange. Further divisions of the airways lead to the respiratory bronchioles, and eventually to the alveoli. The alveolated region of the lung is where the gas exchange takes place, and is referred to as the respiratory zone. See “ Respiratory Physiology”, by John B. West, Lippincott Williams & Wilkins, 9th edition published 2012.

[0005] A range of respiratory disorders exist. Certain disorders may be characterised by particular events, e.g. apneas, hypopneas, and hyperpneas.

[0006] Examples of respiratory disorders include Obstructive Sleep Apnea (OSA), Cheyne-Stokes Respiration (CSR), respiratory insufficiency, Obesity Hypoventilation Syndrome (OHS), Chronic Obstructive Pulmonary Disease (COPD), Neuromuscular Disease (NMD) and Chest wall disorders.2.2.2 Therapies

[0007] Various respiratory therapies, such as Continuous Positive Airway Pressure (CPAP) therapy, Non-invasive ventilation (NIV), Invasive ventilation (IV), and High Flow Therapy (HFT) have been used to treat one or more of the above respiratory disorders.2.2.2.1 Respiratory pressure therapies

[0008] Respiratory pressure therapy is the application of a supply of air to an entrance to the airways at a controlled target pressure that is nominally positive with respect to atmosphere throughout the patient’s breathing cycle (in contrast to negative pressure therapies such as the tank ventilator or cuirass).

[0009] Continuous Positive Airway Pressure (CPAP) therapy has been used to treat Obstructive Sleep Apnea (OSA). The mechanism of action is that continuous positive airway pressure acts as a pneumatic splint and may prevent upper airway occlusion, such as by pushing the soft palate and tongue forward and away from the posterior oropharyngeal wall. Treatment of OSA by CPAP therapy may be voluntary, and hence patients may elect not to comply with therapy if they find devices used to provide such therapy one or more of: uncomfortable, difficult to use, expensive and aesthetically unappealing.

[0010] Non-invasive ventilation (NIV) provides ventilatory support to a patient through the upper airways to assist the patient breathing and / or maintain adequate oxygen levels in the body by doing some or all of the work of breathing. The ventilatory support is provided via a non-invasive patient interface. NIV has been used to treat CSR and respiratory failure, in forms such as OHS, COPD, NMD and Chest Wall disorders. In some forms, the comfort and effectiveness of these therapies may be improved.

[0011] Invasive ventilation (IV) provides ventilatory support to patients that are no longer able to effectively breathe themselves and may be provided using a tracheostomy tube or endotracheal tube. In some forms, the comfort and effectiveness of these therapies may be improved.2.2.2.2 Flow therapies

[0012] Not all respiratory therapies aim to deliver a prescribed therapeutic pressure. Some respiratory therapies aim to deliver a prescribed respiratory volume, by delivering an inspiratory flow rate profile over a targeted duration, possiblysuperimposed on a positive baseline pressure. In other cases, the interface to the patient’s airways is ‘open’ (unsealed) and the respiratory therapy may only supplement the patient’s own spontaneous breathing with a flow of conditioned or enriched gas. In one example, High Flow therapy (HFT) is the provision of a continuous, heated, humidified flow of air to an entrance to the airway through an unsealed or open patient interface at a “treatment flow rate” that may be held approximately constant throughout the respiratory cycle. The treatment flow rate is nominally set to exceed the patient’s peak inspiratory flow rate. HFT has been used to treat OSA, CSR, respiratory failure, COPD, and other respiratory disorders. One mechanism of action is that the high flow rate of air at the airway entrance improves ventilation efficiency by flushing, or washing out, expired CO2 from the patient’s anatomical deadspace. Hence, HFT is thus sometimes referred to as a deadspace therapy (DST). Other benefits may include the elevated warmth and humidification (possibly of benefit in secretion management) and the potential for modest elevation of airway pressures. As an alternative to constant flow rate, the treatment flow rate may follow a profile that varies over the respiratory cycle.

[0013] Another form of flow therapy is long-term oxygen therapy (LTOT) or supplemental oxygen therapy. Doctors may prescribe a continuous flow of oxygen enriched air at a specified oxygen concentration (from 21%, the oxygen fraction in ambient air, to 100%) at a specified flow rate (e.g., 1 litre per minute (LPM), 2 LPM, 3 LPM, etc.) to be delivered to the patient’s airway.2.2.3 Respiratory Therapy Systems

[0014] These respiratory therapies may be provided by a respiratory therapy system or device. Such systems and devices may also be used to screen, diagnose, or monitor a condition without treating it.

[0015] A respiratory therapy system may comprise a Respiratory Pressure Therapy Device (RPT device), an air circuit, a humidifier, a patient interface, an oxygen source, and data management.2.2.3.1 Patient Interface

[0016] A patient interface may be used to interface respiratory equipment to its wearer, for example by providing a flow of air to an entrance to the airways. The flow of air may be provided via a mask to the nose and / or mouth, a tube to the mouth or a tracheostomy tube to the trachea of a patient. Depending upon the therapy to beapplied, the patient interface may form a seal, e.g., with a region of the patient's face, to facilitate the delivery of gas at a pressure at sufficient variance with ambient pressure to effect therapy, e.g., at a positive pressure of about 10 cmBLO relative to ambient pressure. For other forms of therapy, such as the delivery of oxygen, the patient interface may not include a seal sufficient to facilitate delivery to the airways of a supply of gas at a positive pressure of about 10 cmfLO. For flow therapies such as nasal HFT, the patient interface is configured to insufflate the nares but specifically to avoid a complete seal. One example of such a patient interface is a nasal cannula.2.2.3.1 Respiratory Pressure Therapy (RPT) Device

[0017] A respiratory pressure therapy (RPT) device may be used individually or as part of a system to deliver one or more of a number of therapies described above, such as by operating the device to generate a flow of air for delivery to an interface to the airways. The flow of air may be pressure-controlled (for respiratory pressure therapies) or flow-controlled (for flow therapies such as HFT). Thus RPT devices may also act as flow therapy devices. Examples of RPT devices include a CPAP device and a ventilator.

[0018] Air pressure generators are known in a range of applications, e.g. industrial-scale ventilation systems. However, air pressure generators for medical applications have particular requirements not fulfilled by more generalised air pressure generators, such as the reliability, size and weight requirements of medical devices. In addition, even devices designed for medical treatment may suffer from shortcomings, pertaining to one or more of comfort, noise, ease of use, efficacy, size, weight, manufacturability, cost, and reliability.

[0019] An example of the special requirements of certain RPT devices is acoustic noise.

[0020] Table of noise output levels of prior RPT devices (one specimen only, measured using test method specified in ISO 3744 in CPAP mode at 10 cmH20).

[0021] One known RPT device used for treating sleep disordered breathing is the S9 Sleep Therapy System, manufactured by ResMed Inc. Another example of an RPT device is a ventilator. Ventilators such as the ResMed Stellar™ Series of Adult and Paediatric Ventilators may provide support for invasive and non-invasive nondependent ventilation for a range of patients for treating a number of conditions such as but not limited to NMD, OHS and COPD.

[0022] The ResMed Elisee™ 150 ventilator and ResMed VS III™ ventilator may provide support for invasive and non-invasive dependent ventilation suitable for adult or paediatric patients for treating a number of conditions. These ventilators provide volumetric and barometric ventilation modes with a single or double limb circuit.RPT devices typically comprise a pressure generator, such as a motor-driven blower or a compressed gas reservoir, and are configured to supply a flow of air to the airway of a patient. In some cases, the flow of air may be supplied to the airway of the patient at positive pressure. The outlet of the RPT device is connected via an air circuit to a patient interface such as those described above.

[0023] Control of therapy to a patient requires measurement of the flow of air provided to the patient. This flow varies as the patient inhales and exhales.

[0024] Air flow rate is typically ascertained by measuring a drop in pressure over a portion of the flow path. It may be advantageous for the air flow to remain laminar in this flow path portion (at least a low and medium flow rates), and for the velocity of the flow to remain substantially constant across the cross-section of the flow path.

[0025] To promote suitable flow characteristics in the flow path portion, the flow path portion may be provided with a flow element comprising a plurality of flow channels, e.g. defined by a plurality of parallel tubes.

[0026] In some devices of the prior art a flow element comprising a plurality of tubes has been manufactured by injection moulding. However, this requires tapering the internal diameter of the tubes due to the draft angle required for successful injection moulding. This taper reduces the available flow area. Since impedance is largely decided by the smallest flow area within an object the effect of the draft angle on high aspect ratio tubing is significant. While this reduction in area may beacceptable for large RPT devices, it may result in insufficient flow rates and / or unacceptably large pressure loss in smaller units, where space is limited. However, alternative prior art methods of manufacturing a flow element may not be economic.

[0027] The designer of a device may be presented with an infinite number of choices to make. Design criteria often conflict, meaning that certain design choices are far from routine or inevitable. Furthermore, the comfort and efficacy of certain aspects may be highly sensitive to small, subtle changes in one or more parameters.2.2.3.3 Air circuit

[0028] An air circuit is a conduit or a tube constructed and arranged to allow, in use, a flow of air to travel between two components of a respiratory therapy system such as the RPT device and the patient interface. In some cases, there may be separate limbs of the air circuit for inhalation and exhalation. In other cases, a single limb air circuit is used for both inhalation and exhalation.2.1.3.4 Humidifier

[0029] Delivery of a flow of air without humidification may cause drying of airways. The use of a humidifier with an RPT device and the patient interface produces humidified gas that minimizes drying of the nasal mucosa and increases patient airway comfort. In addition, in cooler climates, warm air applied generally to the face area in and about the patient interface is more comfortable than cold air.3 BRIEF SUMMARY OF THE TECHNOLOGY

[0030] The present technology is directed towards providing medical devices used in the screening, diagnosis, monitoring, amelioration, treatment, or prevention of respiratory disorders having one or more of improved comfort, cost, efficacy, ease of use and manufacturability.

[0031] A first aspect of the present technology relates to apparatus used in the screening, diagnosis, monitoring, amelioration, treatment or prevention of a respiratory disorder.

[0032] Another aspect of the present technology relates to methods used in the screening, diagnosis, monitoring, amelioration, treatment or prevention of a respiratory disorder.

[0033] An aspect of certain forms of the present technology is to provide methods and / or apparatus that improve the compliance of patients with respiratory therapy.

[0034] One form of the present technology comprises a flow element for a respiratory pressure therapy (RPT) device, the flow element comprising an outer housing and an insert, wherein the insert and housing together define a plurality of flow channels within the housing, wherein a transverse cross-section of the insert defines a simple open curve, the insert having a first side and an opposite second side, and wherein the insert is configured such that any notional line in a predetermined direction intersects the first side of the insert only once and intersects the second side of the insert only once.

[0035] In examples, a cross-section of the insert comprises a plurality of flat segments.

[0036] In examples, the flow channels are configured to flow a substantially equal mass flow of air, in use.

[0037] In examples, a ratio of a length of each flow channel to the cross- sectional area of the flow channel is between 5:1 and 10: 1.

[0038] In examples, the cross-section of the insert is substantially invariable along the length of the insert.

[0039] In examples, the insert is manufactured by injection moulding in a mould.

[0040] In examples, the predetermined direction is parallel to a line of draw of the mould.

[0041] Another form of the technology comprises a flow plate for an respiratory pressure therapy (RPT) device comprising the flow element defined above.

[0042] In examples, the flow plate further comprises an inlet tube.

[0043] Another form of the present technology comprises a method of manufacturing a flow element for a respiratory pressure therapy (RPT) device, the method comprising:• forming, by injection moulding, a housing for the flow element;• forming, by injection moulding, an insert having a transverse cross-section which defines a simple open curve; and• mounting the insert in the housing, such that insert and housing together define a plurality of flow channels.

[0044] In example, the mould used for forming the insert is a straight pull mould.

[0045] In examples, a line of draw of a mould used for injection moulding the insert is orthogonal to a longitudinal axis of the insert.

[0046] In examples, the step of forming the housing comprises forming a flow plate comprising the housing.

[0047] Another form of the technology comprises a method of manufacturing a flow element for a respiratory pressure therapy (RPT) device, the method comprising:• forming, by injection moulding, a housing for the flow element;• forming, by injection moulding using a straight pull mould, an insert; and• mounting the insert in the housing, such that insert and housing together define a plurality of flow channels.

[0048] An aspect of one form of the present technology is a method of manufacturing apparatus.

[0049] An aspect of one form of the present technology is a portable RPT device that may be carried by a person, e.g., around the home of the person.

[0050] The methods, systems, devices and apparatus described may be implemented so as to improve the functionality of a processor, such as a processor of a specific purpose computer, respiratory monitor and / or a respiratory therapy apparatus. Moreover, the described methods, systems, devices and apparatus can provide improvements in the technological field of automated management, monitoring and / or treatment of respiratory conditions, including, for example, sleep disordered breathing.

[0051] Of course, portions of the aspects may form sub-aspects of the present technology. Also, various ones of the sub-aspects and / or aspects may be combined in various manners and also constitute additional aspects or sub-aspects of the present technology.

[0052] Other features of the technology will be apparent from consideration of the information contained in the following detailed description, abstract, drawings and claims.4 BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The present technology is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements including:4.1 RESPIRATORY THERAPY SYSTEMS

[0054] Fig. 1 shows a system including a patient 1000 wearing a patient interface 3000, in the form of nasal pillows, receiving a supply of air at positive pressure froman RPT device 4000. Air from the RPT device 4000 is humidified in a humidifier 5000, and passes along an air circuit 4170 to the patient 1000. A bed partner 1100 is also shown. The patient is sleeping in a supine sleeping position.4.2 RPT DEVICE

[0055] Fig. 2A shows an RPT device in accordance with one form of the present technology.

[0056] Fig. 2B is a schematic diagram of the pneumatic path of an RPT device in accordance with one form of the present technology. The directions of upstream and downstream are indicated with reference to the blower and the patient interface. The blower is defined to be upstream of the patient interface and the patient interface is defined to be downstream of the blower, regardless of the actual flow direction at any particular moment. Items which are located within the pneumatic path between the blower and the patient interface are downstream of the blower and upstream of the patient interface.

[0057] Fig. 2C is a schematic diagram of the electrical components of an RPT device in accordance with one form of the present technology.

[0058] Fig. 2C-1 is a schematic diagram illustrating the interconnection of various electrical components of the RPT device.

[0059] Fig. 2D is a schematic diagram of the algorithms implemented in an RPT device in accordance with one form of the present technology.

[0060] Fig. 2E is a flow chart illustrating a method carried out by the therapy engine module of Fig. 2D in accordance with one form of the present technology.4.3 BREATHING WAVEFORMS

[0061] Fig. 3 shows a model typical breath waveform of a person while sleeping.4.4 FLOW ELEMENT OF THE PRESENT TECHNOLOGY

[0062] Fig. 4 shows a perspective view of portion of a pneumatic block of an RPT device including a flow element of the present technology.

[0063] Fig. 4 A shows an exploded perspective view of the pneumatic block portion of Fig. 4.

[0064] Fig. 5 shows a front view of the pneumatic block portion of Fig. 4.

[0065] Fig. 6 shows a perspective view of the insert of the flow element shown inFigs. 4, 4A and 5.

[0066] Fig. 7 shows a diagrammatic cross-section view of the insert in a mould for forming the insert.

[0067] Fig. 8 shows a perspective view of a flow insert according to one form of the technology.

[0068] Fig. 9 shows an enlarged cross-section view of a pneumatic block with the flow insert of Fig. 8 installed.

[0069] Fig. 9A shows an enlargement of area 9A from Fig. 9.5 DETAILED DESCRIPTION OF EXAMPLES OF THETECHNOLOGY

[0070] Before the present technology is described in further detail, it is to be understood that the technology is not limited to the particular examples described herein, which may vary. It is also to be understood that the terminology used in this disclosure is for the purpose of describing only the particular examples discussed herein, and is not intended to be limiting.

[0071] The following description is provided in relation to various examples which may share one or more common characteristics and / or features. It is to be understood that one or more features of any one example may be combinable with one or more features of another example or other examples. In addition, any single feature or combination of features in any of the examples may constitute a further example.5.1 THERAPY

[0072] In one form, the present technology comprises a method for treating a respiratory disorder comprising applying positive pressure to the entrance of the airways of a patient 1000.

[0073] In certain examples of the present technology, a supply of air at positive pressure is provided to the nasal passages of the patient via one or both nares.

[0074] In certain examples of the present technology, mouth breathing is limited, restricted or prevented.5.2 RESPIRATORY THERAPY SYSTEMS

[0075] In one form, the present technology comprises a respiratory therapy system for treating a respiratory disorder. The respiratory therapy system may comprise an RPT device 4000 for supplying a flow of air to the patient 1000 via an air circuit 4170 and a patient interface 3000.5.3 RPT DEVICE

[0076] An RPT device 4000 in accordance with one aspect of the present technology comprises mechanical, pneumatic, and / or electrical components and is configured to execute one or more algorithms 4300, such as any of the methods, in whole or in part, described herein. The RPT device 4000 may be configured to generate a flow of air for delivery to a patient’s airways, such as to treat one or more of the respiratory conditions described elsewhere in the present document.

[0077] In one form, the RPT device 4000 is constructed and arranged to be capable of delivering a flow of air in a range of -20 L / min to +150 L / min while maintaining a positive pressure of at least 4 cmH20, or at least 10cmH2O, or at least 20 cmH20.

[0078] Referring to Fig. 2 A, the RPT device may have an external housing 4010, formed in two parts, an upper portion 4012 and a lower portion 4014. Furthermore, the external housing 4010 may include one or more panel(s) 4015. The RPT device 4000 comprises a chassis 4016 that supports one or more internal components of the RPT device 4000. The RPT device 4000 may include a handle 4018.

[0079] The pneumatic path of the RPT device 4000 may comprise one or more air path items, e.g., an inlet air filter 4112, an inlet muffler 4122, a pressure generator 4140 capable of supplying air at positive pressure (e.g., a blower 4142), an outlet muffler 4124 and one or more transducers 4270, such as pressure sensors 4272 and flow rate sensors 4274.

[0080] One or more of the air path items may be located within a removable unitary structure which will be referred to as a pneumatic block 4020. The pneumatic block 4020 may be located within the external housing 4010. In one form a pneumatic block 4020 is supported by, or formed as part of the chassis 4016.

[0081] As shown in Fig. 2C, the RPT device 4000 may have an electrical power supply 4210, one or more input devices 4220, a central controller 4230, a therapy device controller 4240, a pressure generator 4140, one or more protection circuits 4250, memory 4260, transducers 4270, data communication interface 4280 and one or more output devices 4290. Electrical components 4200 may be mounted on a single Printed Circuit Board Assembly (PCBA) 4202. In an alternative form, the RPT device 4000 may include more than one PCBA 4202.5.3.1 RPT device mechanical & pneumatic components

[0082] An RPT device may comprise one or more of the following components in an integral unit. In an alternative form, one or more of the following components may be located as respective separate units.5.3.1.1 Air filter (s)

[0083] An RPT device in accordance with one form of the present technology may include an air filter 4110, or a plurality of air filters 4110.

[0084] In one form illustrated in Fig. 2B, an inlet air filter 4112 is located at the beginning of the pneumatic path upstream of a pressure generator 4140.

[0085] In one form illustrated in Fig. 2B, an outlet air filter 4114, for example an antibacterial filter, is located between an outlet of the pneumatic block 4020 and a patient interface 3000.5.3.1.2 Muffler(s)

[0086] An RPT device in accordance with one form of the present technology may include a muffler 4120, or a plurality of mufflers 4120.

[0087] In one form of the present technology (see e.g., Fig. 2B), an inlet muffler 4122 is located in the pneumatic path upstream of a pressure generator 4140.

[0088] In one form of the present technology, an outlet muffler 4124 is located in the pneumatic path between the pressure generator 4140 and a patient interface 3000.5.3.1.3 Pressure generator

[0089] In one form of the present technology, a pressure generator 4140 for producing a flow, or a supply, of air at positive pressure is a controllable blower 4142. For example, the blower 4142 may include a brushless DC motor 4144 with one or more impellers. The impellers may be located in a volute. The blower may be capable of delivering a supply of air, for example at a rate of up to about 120 litres / minute, at a positive pressure in a range from about 4 cmH20 to about 20 cmH20, or in other forms up to about 30 cmH20 when delivering respiratory pressure therapy. The blower may be as described in any one of the following patents or patent applications the contents of which are incorporated herein by reference in their entirety: U.S.Patent No. 7,866,944; U.S. Patent No. 8,638,014; U.S. Patent No. 8,636,479; and PCT Patent Application Publication No. WO 2013 / 020167.

[0090] The pressure generator 4140 may be under the control of the therapy device controller 4240.

[0091] In other forms, a pressure generator 4140 may be a piston-driven pump, a pressure regulator connected to a high pressure source (e.g. compressed air reservoir), or a bellows.5.3.1.4 Transducer(s)

[0092] Transducers may be internal of the RPT device, or external of the RPT device. External transducers may be located for example on or form part of the air circuit, e.g., the patient interface. External transducers may be in the form of noncontact sensors such as a Doppler radar movement sensor that transmit or transfer data to the RPT device.

[0093] In one form of the present technology (see e.g., Fig. 2B), one or more transducers 4270 are located upstream and / or downstream of the pressure generator 4140. The one or more transducers 4270 may be constructed and arranged to generate signals representing properties of the flow of air such as a flow rate, a pressure or a temperature at that point in the pneumatic path.

[0094] In one form of the present technology, one or more transducers 4270 may be located proximate to the patient interface 3000.

[0095] In one form, a signal from a transducer 4270 may be filtered, such as by low-pass, high-pass or band-pass filtering.5.3.1.4.1 Flow rate sensor

[0096] A flow rate sensor 4274 in accordance with the present technology may be based on a differential pressure transducer, for example, an SDP600 Series differential pressure transducer from SENSIRION.

[0097] In one form, a signal generated by the flow rate sensor 4274 and representing a flow rate is received by the central controller 4230.5.3.1.4.2 Pressure sensor

[0098] A pressure sensor 4272 in accordance with the present technology is located in fluid communication with the pneumatic path. An example of a suitable pressure sensor is a transducer from the HONEYWELL ASDX series. An alternative suitable pressure sensor is a transducer from the NPA Series from GENERAL ELECTRIC.

[0099] In one form, a signal generated by the pressure sensor 4272 and representing a pressure is received by the central controller 4230.5.3.1.4.3 Motor speed transducer

[0100] In one form of the present technology a motor speed transducer 4276 is used to determine a rotational velocity of the motor 4144 and / or the blower 4142. A motor speed signal from the motor speed transducer 4276 may be provided to the therapy device controller 4240. The motor speed transducer 4276 may, for example, be a speed sensor, such as a Hall effect sensor.5.3.1.5 Anti-spill back valve

[0101] As shown in Fig. 2B, one form of the present technology, an anti-spill back valve 4160 is located between the humidifier 5000 and the pneumatic block 4020. The anti-spill back valve is constructed and arranged to reduce the risk that water will flow upstream from the humidifier 5000, for example to the motor 4144.5.3.2 RPT device electrical components5.3.2.1 Power supply

[0102] A power supply 4210 may be located internal or external of the external housing 4010 of the RPT device 4000.

[0103] In one form of the present technology, power supply 4210 provides electrical power to the RPT device 4000 only. In another form of the present technology, power supply 4210 provides electrical power to both RPT device 4000 and humidifier 5000.

[0104] As illustrated in Fig. 2C-1, the power supply 4210 may provide electrical power to the input device 4220, the central controller 4230, the output device 4290, and the pressure generator 4140. The power supply 4210 may also provide electric energy to other components of the RPT device 4000 (or the humidifier 5000, as described above).5.3.2.1 Input devices

[0105] In one form of the present technology, an RPT device 4000 includes one or more input devices 4220 in the form of buttons, switches or dials to allow a person to interact with the device. The buttons, switches or dials may be physical devices, or software devices accessible via a touch screen. The buttons, switches or dials may, in one form, be physically connected to the external housing 4010, or may, in another form, be in wireless communication with a receiver that is in electrical connection to the central controller 4230.

[0106] In one form, the input device 4220 may be constructed and arranged to allow a person to select a value and / or a menu option.5.3.1.3 Central controller

[0107] In one form of the present technology, the central controller 4230 is one or a plurality of processors suitable to control an RPT device 4000. The central controller 4230 is show in Figs. 2C and 2C-1.

[0108] Suitable processors may include an x86 INTEL processor, a processor based on ARM® Cortex®-M processor from ARM Holdings such as an STM32 series microcontroller from ST MICROELECTRONIC. In certain alternative forms of the present technology, a 32-bit RISC CPU, such as an STR9 series microcontroller from ST MICROELECTRONICS or a 16-bit RISC CPU such as a processor from the MSP430 family of microcontrollers, manufactured by TEXAS INSTRUMENTS may also be suitable.

[0109] In one form of the present technology, the central controller 4230 is a dedicated electronic circuit.

[0110] In one form, the central controller 4230 is an application-specific integrated circuit. In another form, the central controller 4230 comprises discrete electronic components.

[0111] The central controller 4230 may be configured to receive input signal(s) from one or more transducers 4270, one or more input devices 4220, and / or the humidifier 5000.

[0112] The central controller 4230 may be configured to provide output signal(s) to one or more of an output device 4290, a pressure generator 4140, a therapy device controller 4240, a data communication interface 4280, and / or the humidifier 5000.

[0113] In some forms of the present technology, the central controller 4230 is configured to implement the one or more methodologies described herein, such as the one or more algorithms 4300 which may be implemented with processor-control instructions, expressed as computer programs stored in a non-transitory computer readable storage medium, such as memory 4260. In some forms of the present technology, the central controller 4230 may be integrated with an RPT device 4000. However, in some forms of the present technology, some methodologies may be performed by a remotely located device. For example, the remotely located device may determine control settings for a ventilator or detect respiratory related events by analysis of stored data such as from any of the sensors described herein.53.2.4 Clock

[0114] The RPT device 4000 may include a clock 4232 that is connected to the central controller 4230.5.3.2.5 Therapy device controller

[0115] In one form of the present technology, therapy device controller 4240 is a therapy control module 4330 that forms part of the algorithms 4300 executed by the central controller 4230.

[0116] In one form of the present technology, therapy device controller 4240 is a dedicated motor control integrated circuit. For example, in one form a MC33035 brushless DC motor controller, manufactured by ONSEMI is used.5.3.2.6 Protection circuits

[0117] The one or more protection circuits 4250 in accordance with the present technology may comprise an electrical protection circuit, a temperature and / or pressure safety circuit.5.3.2.7 Memory

[0118] In accordance with one form of the present technology the RPT device 4000 includes memory 4260, e.g., non-volatile memory. In some forms, memory 4260 may include battery powered static RAM. In some forms, memory 4260 may include volatile RAM.

[0119] Memory 4260 may be located on the PCBA 4202. Memory 4260 may be in the form of EEPROM, or NAND flash.

[0120] Additionally, or alternatively, RPT device 4000 includes a removable form of memory 4260, for example a memory card made in accordance with the Secure Digital (SD) standard.

[0121] In one form of the present technology, the memory 4260 acts as a non- transitory computer readable storage medium on which is stored computer program instructions expressing the one or more methodologies described herein, such as the one or more algorithms 4300.5.3.2.8 Data communication systems

[0122] In one form of the present technology, a data communication interface 4280 is provided, and is connected to the central controller 4230 (see e.g., Fig. 2C). Data communication interface 4280 may be connectable to a remote external communication network 4282 and / or a local external communication network 4284. The remote external communication network 4282 may be connectable to a remoteexternal device 4286. The local external communication network 4284 may be connectable to a local external device 4288.

[0123] In one form, data communication interface 4280 is part of the central controller 4230. In another form, data communication interface 4280 is separate from the central controller 4230, and may comprise an integrated circuit or a processor.

[0124] In one form, remote external communication network 4282 is the Internet. The data communication interface 4280 may use wired communication (e.g. via Ethernet, or optical fibre) or a wireless protocol (e.g. CDMA, GSM, LTE) to connect to the Internet.

[0125] In one form, local external communication network 4284 utilises one or more communication standards, such as Bluetooth, or a consumer infrared protocol.

[0126] In one form, remote external device 4286 is one or more computers, for example a cluster of networked computers. In one form, remote external device 4286 may be virtual computers, rather than physical computers. In either case, such a remote external device 4286 may be accessible to an appropriately authorised person such as a clinician.

[0127] The local external device 4288 may be a personal computer, mobile phone, tablet or remote control.5.3.1.9 Output devices including optional display, alarms

[0128] An output device 4290 in accordance with the present technology may take the form of one or more of a visual, audio and haptic unit. A visual display may be a Liquid Crystal Display (LCD) or Light Emitting Diode (LED) display.5.3.2.9.1 Display driver

[0129] A display driver 4292 receives as an input the characters, symbols, or images intended for display on the display 4294, and converts them to commands that cause the display 4294 to display those characters, symbols, or images.5.3.2.9.2 Display

[0130] A display 4294 is configured to visually display characters, symbols, or images in response to commands received from the display driver 4292. For example, the display 4294 may be an eight-segment display, in which case the display driver 4292 converts each character or symbol, such as the figure “0”, to eight logical signals indicating whether the eight respective segments are to be activated to display a particular character or symbol.5.3.3 RPT device algorithms

[0131] As mentioned above, in some forms of the present technology, the central controller 4230 may be configured to implement one or more algorithms 4300 expressed as computer programs stored in a non-transitory computer readable storage medium, such as memory 4260. The algorithms 4300 are generally grouped into groups referred to as modules.

[0132] In other forms of the present technology, some portion or all of the algorithms 4300 may be implemented by a controller of an external device such as the local external device 4288 or the remote external device 4286. In such forms, data representing the input signals and / or intermediate algorithm outputs necessary for the portion of the algorithms 4300 to be executed at the external device may be communicated to the external device via the local external communication network 4284 or the remote external communication network 4282. In such forms, the portion of the algorithms 4300 to be executed at the external device may be expressed as computer programs, such as with processor control instructions to be executed by one or more processor(s), stored in a non-transitory computer readable storage medium accessible to the controller of the external device. Such programs configure the controller of the external device to execute the portion of the algorithms 4300.

[0133] In such forms, the therapy parameters generated by the external device via the therapy engine module 4320 (if such forms part of the portion of the algorithms 4300 executed by the external device) may be communicated to the central controller 4230 to be passed to the therapy control module 4330.5.3.3.1 Pre-processing module

[0134] A pre-processing module 4310 in accordance with one form of the present technology receives as an input a signal from a transducer 4270, for example a flow rate sensor 4274 or pressure sensor 4272, and performs one or more process steps to calculate one or more output values that will be used as an input to another module, for example a therapy engine module 4320.

[0135] In one form of the present technology, the output values include the interface pressure Pm, the vent flow rate Qv, the respiratory flow rate Qr, and the leak flow rate QI.

[0136] In various forms of the present technology, the pre-processing module 4310 comprises one or more of the following algorithms: interface pressureestimation 4312, vent flow rate estimation 4314, leak flow rate estimation 4316, and respiratory flow rate estimation 4318.5.3.3.1.1 Interface pressure estimation

[0137] In one form of the present technology, an interface pressure estimation algorithm 4312 receives as inputs a signal from the pressure sensor 4272 indicative of the pressure in the pneumatic path proximal to an outlet of the pneumatic block (the device pressure Pd) and a signal from the flow rate sensor 4274 representative of the flow rate of the airflow leaving the RPT device 4000 (the device flow rate Qd). The device flow rate Qd, absent any supplementary gas 4180, may be used as the total flow rate Qt. The interface pressure algorithm 4312 estimates the pressure drop AP through the air circuit 4170. The dependence of the pressure drop AP on the total flow rate Qt may be modelled for the particular air circuit 4170 by a pressure drop characteristic AP(Q). The interface pressure estimation algorithm, 4312 then provides as an output an estimated pressure, Pm, in the patient interface 3000. The pressure, Pm, in the patient interface 3000 may be estimated as the device pressure Pd minus the air circuit pressure drop AP.5.3.3.1.2 Vent flow rate estimation

[0138] In one form of the present technology, a vent flow rate estimation algorithm 4314 receives as an input an estimated pressure, Pm, in the patient interface 3000 from the interface pressure estimation algorithm 4312 and estimates a vent flow rate of air, Qv, from a vent 3400 in a patient interface 3000. The dependence of the vent flow rate Qv on the interface pressure Pm for the particular vent 3400 in use may be modelled by a vent characteristic Qv(Pm).5.3.3.1.3 Leak flow rate estimation

[0139] In one form of the present technology, a leak flow rate estimation algorithm 4316 receives as an input a total flow rate, Qt, and a vent flow rate Qv, and provides as an output an estimate of the leak flow rate QI. In one form, the leak flow rate estimation algorithm estimates the leak flow rate QI by calculating an average of the difference between total flow rate Qt and vent flow rate Qv over a period sufficiently long to include several breathing cycles, e.g. about 10 seconds.

[0140] In one form, the leak flow rate estimation algorithm 4316 receives as an input a total flow rate Qt, a vent flow rate Qv, and an estimated pressure, Pm, in the patient interface 3000 , and provides as an output a leak flow rate QI, by calculating aleak conductance, and determining a leak flow rate QI to be a function of leak conductance and pressure, Pm. Leak conductance is calculated as the quotient of low pass filtered non-vent flow rate equal to the difference between total flow rate Qt and vent flow rate Qy, and low pass filtered square root of pressure Pm, where the low pass filter time constant has a value sufficiently long to include several breathing cycles, e.g. about 10 seconds. The leak flow rate QI may be estimated as the product of leak conductance and a function of pressure, Pm.5.3.3.1.4 Respiratory flow rate estimation

[0141] In one form of the present technology, a respiratory flow rate estimation algorithm 4318 receives as an input a total flow rate, Qt, a vent flow rate, Qy, and a leak flow rate, QI, and estimates a respiratory flow rate of air, Qr, to the patient, by subtracting the vent flow rate Qy and the leak flow rate QI from the total flow rate Qt.5.3.3.1 Therapy Engine Module

[0142] In one form of the present technology, a therapy engine module 4320 receives as inputs one or more of a pressure, Pm, in a patient interface 3000, and a respiratory flow rate of air to a patient, Qr, and provides as an output one or more therapy parameters.

[0143] In one form of the present technology, a therapy parameter is a treatment pressure Pt.

[0144] In one form of the present technology, therapy parameters are one or more of an amplitude of a pressure variation, a base pressure, and a target ventilation.

[0145] In various forms, the therapy engine module 4320 comprises one or more of the following algorithms: phase determination 4321, waveform determination 4322, ventilation determination 4323, inspiratory flow limitation determination 4324, apnea / hypopnea determination 4325, snore determination 4326, airway patency determination 4327, target ventilation determination 4328, and therapy parameter determination 4329.5.3.3.2.1 Phase determination

[0146] In one form of the present technology, the RPT device 4000 does not determine phase.

[0147] In one form of the present technology, a phase determination algorithm 4321 receives as an input a signal indicative of respiratory flow rate, Qr, and provides as an output a phase of a current breathing cycle of a patient 1000.

[0148] In some forms, known as discrete phase determination, the phase output is a discrete variable. One implementation of discrete phase determination provides a bi-valued phase output with values of either inhalation or exhalation, for example represented as values of 0 and 0.5 revolutions respectively, upon detecting the start of spontaneous inhalation and exhalation respectively. RPT devices 4000 that “trigger” and “cycle” effectively perform discrete phase determination, since the trigger and cycle points are the instants at which the phase changes from exhalation to inhalation and from inhalation to exhalation, respectively. In one implementation of bi-valued phase determination, the phase output is determined to have a discrete value of 0 (thereby “triggering” the RPT device 4000) when the respiratory flow rate Qr has a value that exceeds a positive threshold, and a discrete value of 0.5 revolutions (thereby “cycling” the RPT device 4000) when a respiratory flow rate Qr has a value that is more negative than a negative threshold. The inhalation time Ti and the exhalation time Te may be estimated as typical values over many respiratory cycles of the time spent with phase equal to 0 (indicating inspiration) and 0.5 (indicating expiration) respectively.

[0149] Another implementation of discrete phase determination provides a trivalued phase output with a value of one of inhalation, mid-inspiratory pause, and exhalation.

[0150] In other forms, known as continuous phase determination, the phase output is a continuous variable, for example varying from 0 to 1 revolutions, or 0 to 2 ;r radians. RPT devices 4000 that perform continuous phase determination may trigger and cycle when the continuous phase reaches 0 and 0.5 revolutions, respectively. In one implementation of continuous phase determination, a continuous value of phase is determined using a fuzzy logic analysis of the respiratory flow rate Qr. A continuous value of phase determined in this implementation is often referred to as “fuzzy phase”. In one implementation of a fuzzy phase determination algorithm 4321, the following rules are applied to the respiratory flow rate Qr.1. is zero and increasing fast then is 0 revolutions.2. If Qr is large positive and steady thenis 0.25 revolutions.3. If Qr is zero and falling fast, then is 0.5 revolutions.4. If Qr is large negative and steady then is 0.75 revolutions.5. If Qr is zero and steady and the 5-second low-pass filtered absolute value of Qr is large then O is 0.9 revolutions.6. If Qr is positive and the phase is expiratory, then O is 0 revolutions.7. If Qr is negative and the phase is inspiratory, then O is 0.5 revolutions.8. If the 5-second low-pass filtered absolute value of Qr is large, O is increasing at a steady rate equal to the patient’s breathing rate, low-pass filtered with a time constant of 20 seconds.

[0151] The output of each rule may be represented as a vector whose phase is the result of the rule and whose magnitude is the fuzzy extent to which the rule is true. The fuzzy extent to which the respiratory flow rate is “large”, “steady”, etc. is determined with suitable membership functions. The results of the rules, represented as vectors, are then combined by some function such as taking the centroid. In such a combination, the rules may be equally weighted, or differently weighted.

[0152] In another implementation of continuous phase determination, the phase O is first discretely estimated from the respiratory flow rate Qr as described above, as are the inhalation time Ti and the exhalation time Te. The continuous phase O at any instant may be determined as the half the proportion of the inhalation time Ti that has elapsed since the previous trigger instant, or 0.5 revolutions plus half the proportion of the exhalation time Te that has elapsed since the previous cycle instant (whichever instant was more recent).5.3.3.2.2 Waveform determination

[0153] In one form of the present technology, the therapy parameter determination algorithm 4329 provides an approximately constant treatment pressure throughout a respiratory cycle of a patient.

[0154] In other forms of the present technology, the therapy control module 4330 controls the pressure generator 4140 to provide a treatment pressure Pt that varies as a function of phase O of a respiratory cycle of a patient according to a waveform template 11( ).

[0155] In one form of the present technology, a waveform determination algorithm 4322 provides a waveform template 11( ) with values in the range [0, 1] on the domain of phase values O provided by the phase determination algorithm 4321 to be used by the therapy parameter determination algorithm 4329.

[0156] In one form, suitable for either discrete or continuously-valued phase, the waveform template 11( ) is a square-wave template, having a value of 1 for values of phase up to and including 0.5 revolutions, and a value of 0 for values of phase above 0.5 revolutions. In one form, suitable for continuously-valued phase, the waveform template 11( ) comprises two smoothly curved portions, namely a smoothly curved (e.g. raised cosine) rise from 0 to 1 for values of phase up to 0.5 revolutions, and a smoothly curved (e.g. exponential) decay from 1 to 0 for values of phase above 0.5 revolutions. In one form, suitable for continuously-valued phase, the waveform template 11( ) is based on a square wave, but with a smooth rise from 0 to 1 for values of phase up to a “rise time” that is less than 0.5 revolutions, and a smooth fall from 1 to 0 for values of phase within a “fall time” after 0.5 revolutions, with a “fall time” that is less than 0.5 revolutions.

[0157] In some forms of the present technology, the waveform determination algorithm 4322 selects a waveform template 11( ) from a library of waveform templates, dependent on a setting of the RPT device. Each waveform template 11( ) in the library may be provided as a lookup table of values II against phase values O. In other forms, the waveform determination algorithm 4322 computes a waveform template 11(0) “on the fly” using a predetermined functional form, possibly parametrised by one or more parameters (e.g. time constant of an exponentially curved portion). The parameters of the functional form may be predetermined or dependent on a current state of the patient 1000.

[0158] In some forms of the present technology, suitable for discrete bi-valued phase of either inhalation (0 = 0 revolutions) or exhalation (O = 0.5 revolutions), the waveform determination algorithm 4322 computes a waveform template II “on the fly” as a function of both discrete phase O and time t measured since the most recent trigger instant. In one such form, the waveform determination algorithm 4322 computes the waveform template 11( , f) in two portions (inspiratory and expiratory) as follows: 0 = 00 = 0.5

[0159] where Ili(t) and TIC( / ) are inspiratory and expiratory portions of the waveform template 11(0, f). In one such form, the inspiratory portion H i( / ) of the waveform template is a smooth rise from 0 to 1 parametrised by a rise time, and theexpiratory portion Hc( / ) of the waveform template is a smooth fall from 1 to 0 parametrised by a fall time.5.3.3.2.3 Ventilation determination

[0160] In one form of the present technology, a ventilation determination algorithm 4323 receives an input a respiratory flow rate Qr, and determines a measure indicative of current patient ventilation, Vent.

[0161] In some implementations, the ventilation determination algorithm 4323 determines a measure of ventilation Vent that is an estimate of actual patient ventilation. One such implementation is to take half the absolute value of respiratory flow rate, Qr, optionally filtered by low-pass filter such as a second order Bessel low- pass filter with a comer frequency of 0.11 Hz.

[0162] In other implementations, the ventilation determination algorithm 4323 determines a measure of ventilation Vent that is broadly proportional to actual patient ventilation. One such implementation estimates peak respiratory flow rate Qpeak over the inspiratory portion of the cycle. This and many other procedures involving sampling the respiratory flow rate Qr produce measures which are broadly proportional to ventilation, provided the flow rate waveform shape does not vary very much (here, the shape of two breaths is taken to be similar when the flow rate waveforms of the breaths normalised in time and amplitude are similar). Some simple examples include the median positive respiratory flow rate, the median of the absolute value of respiratory flow rate, and the standard deviation of flow rate. Arbitrary linear combinations of arbitrary order statistics of the absolute value of respiratory flow rate using positive coefficients, and even some using both positive and negative coefficients, are approximately proportional to ventilation. Another example is the mean of the respiratory flow rate in the middle K proportion (by time) of the inspiratory portion, where 0 < K< 1. There is an arbitrarily large number of measures that are exactly proportional to ventilation if the flow rate shape is constant.5.3.3.2.4 Determination of Inspiratory Flow Limitation

[0163] In one form of the present technology, the central controller 4230 executes an inspiratory flow limitation determination algorithm 4324 for the determination of the extent of inspiratory flow limitation.

[0164] In one form, the inspiratory flow limitation determination algorithm 4324 receives as an input a respiratory flow rate signal Qr and provides as an output ametric of the extent to which the inspiratory portion of the breath exhibits inspiratory flow limitation.

[0165] In one form of the present technology, the inspiratory portion of each breath is identified by a zero-crossing detector. A number of evenly spaced points (for example, sixty-five), representing points in time, are interpolated by an interpolator along the inspiratory flow rate-time curve for each breath. The curve described by the points is then scaled by a scalar to have unity length (duration / period) and unity area to remove the effects of changing breathing rate and depth. The scaled breaths are then compared in a comparator with a pre-stored template representing a normal unobstructed breath, similar to the inspiratory portion of the breath shown in Fig. 3. Breaths deviating by more than a specified threshold (typically 1 scaled unit) at any time during the inspiration from this template, such as those due to coughs, sighs, swallows and hiccups, as determined by a test element, are rejected. For non -rejected data, a moving average of the first such scaled point is calculated by the central controller 4230 for the preceding several inspiratory events. This is repeated over the same inspiratory events for the second such point, and so on. Thus, for example, sixty-five scaled data points are generated by the central controller 4230, and represent a moving average of the preceding several inspiratory events, e.g., three events. The moving average of continuously updated values of the (e.g., sixty-five) points are hereinafter called the "scaled flow rate ", designated as Qs(t). Alternatively, a single inspiratory event can be utilised rather than a moving average.

[0166] From the scaled flow rate, two shape factors relating to the determination of partial obstruction may be calculated.

[0167] Shape factor 1 is the ratio of the mean of the middle (e.g. thirty -two) scaled flow rate points to the mean overall (e.g. sixty-five) scaled flow rate points. Where this ratio is in excess of unity, the breath will be taken to be normal. Where the ratio is unity or less, the breath will be taken to be obstructed. A ratio of about 1.17 is taken as a threshold between partially obstructed and unobstructed breathing, and equates to a degree of obstruction that would permit maintenance of adequate oxygenation in a typical patient.

[0168] Shape factor 2 is calculated as the RMS deviation from unit scaled flow rate, taken over the middle (e.g. thirty-two) points. An RMS deviation of about 0.2 units is taken to be normal. An RMS deviation of zero is taken to be a totally flow-limited breath. The closer the RMS deviation to zero, the breath will be taken to be more flow limited.

[0169] Shape factors 1 and 2 may be used as alternatives, or in combination. In other forms of the present technology, the number of sampled points, breaths and middle points may differ from those described above. Furthermore, the threshold values can be other than those described.5.3.3.2.5 Determination of apneas and hypopneas

[0170] In one form of the present technology, the central controller 4230 executes an apnea / hypopnea determination algorithm 4325 for the determination of the presence of apneas and / or hypopneas.

[0171] In one form, the apnea / hypopnea determination algorithm 4325 receives as an input a respiratory flow rate signal Qr and provides as an output a flag that indicates that an apnea or a hypopnea has been detected.

[0172] In one form, an apnea will be said to have been detected when a function of respiratory flow rate Qr falls below a flow rate threshold for a predetermined period of time. The function may determine a peak flow rate, a relatively short-term mean flow rate, or a flow rate intermediate of relatively short-term mean and peak flow rate, for example an RMS flow rate. The flow rate threshold may be a relatively long-term measure of flow rate.

[0173] In one form, a hypopnea will be said to have been detected when a function of respiratory flow rate Qr falls below a second flow rate threshold for a predetermined period of time. The function may determine a peak flow, a relatively short-term mean flow rate, or a flow rate intermediate of relatively short-term mean and peak flow rate, for example an RMS flow rate. The second flow rate threshold may be a relatively long-term measure of flow rate. The second flow rate threshold is greater than the flow rate threshold used to detect apneas.5.3.3.2.6 Determination of snore

[0174] In one form of the present technology, the central controller 4230 executes one or more snore determination algorithms 4326 for the determination of the extent of snore.

[0175] In one form, the snore determination algorithm 4326 receives as an input a respiratory flow rate signal Qr and provides as an output a metric of the extent to which snoring is present.

[0176] The snore determination algorithm 4326 may comprise the step of determining the intensity of the flow rate signal in the range of 30-300 Hz. Further, the snore determination algorithm 4326 may comprise a step of filtering the respiratory flow rate signal Qr to reduce background noise, e.g., the sound of airflow in the system from the blower.5.3.3.2. 7 Determination of airway patency

[0177] In one form of the present technology, the central controller 4230 executes one or more airway patency determination algorithms 4327 for the determination of the extent of airway patency.

[0178] In one form, the airway patency determination algorithm 4327 receives as an input a respiratory flow rate signal Qr, and determines the power of the signal in the frequency range of about 0.75 Hz and about 3 Hz. The presence of a peak in this frequency range is taken to indicate an open airway. The absence of a peak is taken to be an indication of a closed airway.

[0179] In one form, the frequency range within which the peak is sought is the frequency of a small forced oscillation in the treatment pressure Pt. In one implementation, the forced oscillation is of frequency 2 Hz with amplitude about 1 cmH20.

[0180] In one form, airway patency determination algorithm 4327 receives as an input a respiratory flow rate signal Qr, and determines the presence or absence of a cardiogenic signal. The absence of a cardiogenic signal is taken to be an indication of a closed airway.5.3.3.2.8 Determination of target ventilation

[0181] In one form of the present technology, the central controller 4230 takes as input the measure of current ventilation, Vent, and executes one or more target ventilation determination algorithms 4328 for the determination of a target value Vtgt for the measure of ventilation.

[0182] In some forms of the present technology, there is no target ventilation determination algorithm 4328, and the target value Vtgt is predetermined, for example by hard-coding during configuration of the RPT device 4000 or by manual entry through the input device 4220.

[0183] In other forms of the present technology, such as adaptive servoventilation (ASV), the target ventilation determination algorithm 4328 computes atarget value Vtgt from a value Vtyp indicative of the typical recent ventilation of the patient.

[0184] In some forms of adaptive servo-ventilation, the target ventilation Vtgt is computed as a high proportion of, but less than, the typical recent ventilation Vtyp. The high proportion in such forms may be in the range (80%, 100%), or (85%, 95%), or (87%, 92%).

[0185] In other forms of adaptive servo-ventilation, the target ventilation Vtgt is computed as a slightly greater than unity multiple of the typical recent ventilation f -

[0186] The typical recent ventilation Vtyp is the value around which the distribution of the measure of current ventilation Vent over multiple time instants over some predetermined timescale tends to cluster, that is, a measure of the central tendency of the measure of current ventilation over recent history. In one implementation of the target ventilation determination algorithm 4328, the recent history is of the order of several minutes, but in any case should be longer than the timescale of Cheyne-Stokes waxing and waning cycles. The target ventilation determination algorithm 4328 may use any of the variety of well-known measures of central tendency to determine the typical recent ventilation Vtyp from the measure of current ventilation, Vent. One such measure is the output of a low-pass filter on the measure of current ventilation Vent, with time constant equal to one hundred seconds.5.3.3.2.9 Determination of therapy parameters

[0187] In some forms of the present technology, the central controller 4230 executes one or more therapy parameter determination algorithms 4329 for the determination of one or more therapy parameters using the values returned by one or more of the other algorithms in the therapy engine module 4320.

[0188] In one form of the present technology, the therapy parameter is an instantaneous treatment pressure Pt. In one implementation of this form, the therapy parameter determination algorithm 4329 determines the treatment pressure Pt using the equation

[0189] where:• A is the amplitude,• 11( , f) is the waveform template value (in the range 0 to 1) at the current value 0 of phase and t of time, and• P is a base pressure.

[0190] If the waveform determination algorithm 4322 provides the waveform template 11( , f) as a lookup table of values II indexed by phase , the therapy parameter determination algorithm 4329 applies equation (1) by locating the nearest lookup table entry to the current value of phase returned by the phase determination algorithm 4321, or by interpolation between the two entries straddling the current value of phase.

[0191] The values of the amplitude A and the base pressure Po may be set by the therapy parameter determination algorithm 4329 depending on the chosen respiratory pressure therapy mode in the manner described below.5.3.3.3 Therapy Control module

[0192] The therapy control module 4330 in accordance with one aspect of the present technology receives as inputs the therapy parameters from the therapy parameter determination algorithm 4329 of the therapy engine module 4320, and controls the pressure generator 4140 to deliver a flow of air in accordance with the therapy parameters.

[0193] In one form of the present technology, the therapy parameter is a treatment pressure Pt, and the therapy control module 4330 controls the pressure generator 4140 to deliver a flow of air whose interface pressure Pm at the patient interface 3000 is equal to the treatment pressure Pt.5.3.3.4 Detection of fault conditions

[0194] In one form of the present technology, the central controller 4230 executes one or more methods 4340 for the detection of fault conditions. The fault conditions detected by the one or more methods 4340 may include at least one of the following:• Power failure (no power, or insufficient power)• Transducer fault detection• Failure to detect the presence of a component• Operating parameters outside recommended ranges (e.g. pressure, flow rate, temperature, PaO2)• Failure of a test alarm to generate a detectable alarm signal.

[0195] Upon detection of the fault condition, the corresponding algorithm 4340 signals the presence of the fault by one or more of the following:• Initiation of an audible, visual & / or kinetic (e.g. vibrating) alarm• Sending a message to an external device• Logging of the incident.5.3.4 Flow Element

[0196] Referring next to Figs. 4-6, a flow element 4600 for an RPT device 4000 is shown. In examples, the flow element 4600 forms part of the pneumatic block 4020 of the RPT device 4000. In the example shown, the flow element 4600 is formed as part of a flow plate 4700. In the example shown the flow plate 4700 also comprises an inlet tube 4710, but this is not an essential feature of the invention. In other examples the flow element 4600 may be formed independently (e.g. not as part of a flow plate), or may form part of, or may be formed with, another component of the RPT device.

[0197] The flow element 4600 comprises an outer housing 4610 and an insert 4620. The insert 4620 is configured to cooperate with the housing 4610 to define a plurality of flow paths, conduits or channels 4630 (best seen in Fig. 5). Each flow path 4630 is defined by a portion of the insert 4620 and a portion of the housing 4610.

[0198] As best seen in Fig. 5, a transverse cross-section of the insert 4620 forms a simple open curve. Referring next to Fig. 6, the insert 4620 has a first side 4640 and an opposite second side 4650, and is configured such that any notional line L having a predetermined direction (relative to the insert 4620) intersects the first side 4640 of the insert 4620 only once and intersects the second side 4650 of the insert 4620 only once. In examples, the insert 4620 is manufactured from plastic by injection moulding and the predetermined direction L is parallel with the line of draw of the mould (see Fig. 7). The predetermined direction of the notional line L is typically orthogonal to the longitudinal axis LA of the insert 4620 (the axis LA being parallel to the direction of flow through the flow element). In many examples the insert 4620 can be injection moulded using a straight-pull mould 4680, as shown diagrammatically in Fig. 7, with the parting direction P of the mould 4680 being parallel to the line L.

[0199] Referring back to Figs. 5 and 6, in examples, the transverse cross-section of the insert 4620 comprises a plurality of segments 4660, for example straightsegments. In some embodiments the transverse cross-section of the insert 4620 does not include any non-straight segments. In one example the insert 4620 has a substantially constant wall thickness, for example of around 0.6mm. In examples, the insert 4620 may have a substantially invariable cross-section along its length.

[0200] In some examples, one or more of the intersections 4670 between two connected segments 4660 may be configured to allow the angle A between the segments 4660 to be varied (e.g. in a similar manner to a living hinge) such that the insert 4620 can be deformed to at least a small degree when mounted within the housing 4610. In some examples the angle A between the segments 4660 may be different when the insert 4620 is in place in the housing 4610 than it is when the insert 4620 is not under any stress.

[0201] The insert 4620 may be configured such that a substantially equal mass flow rate of air flows through each flow path 4630, in use. In examples, each flow path 4630 may have substantially the same cross-sectional area (e.g. in a direction parallel to the flow direction). However, in other examples the geometry of the conduits upstream and / or downstream of the flow element 4600 may make it necessary (or at least desirable) for the flow paths 4630 to have different cross- sectional areas to substantially equalise the mass flows.

[0202] The flow element 4600 may be provided between two pressure measurement points (not shown) as part of a flow rate sensing apparatus for the RPT device (e.g. flow rate sensor 4274). The flow element 4600 may be configured to ensure the air flow is sufficiently developed towards laminar flow, at least at the downstream pressure measurement point, at least when the flow rates are relatively low. In examples the ratio of the length of each flow path 4630 to the cross-sectional area of the flow path 4630 is between 5:1 and 10: 1. Preferably, at least six flow paths 4630 are formed.

[0203] In examples, the insert 4620 is manufactured separately to the housing 4610 and is then mounted to the housing 4610. In examples, both the insert 4620 and the housing 4610 are manufactured by injection moulding processes.

[0204] Referring to Figs. 8, 9 and 9A, in examples, the insert 4620 comprises retention features 4720 configured to engage with features provided to an innersurface of the housing 4610 to retain the insert 4620 in a required position within the housing 4610. In examples, the retention features 4720 comprise notches or cutouts which engage suitably formed protrusions 4730 provided to an inner surface of the housing 4610.

[0205] In examples, the protrusions 4730 comprise a ramped face 4740 which is configured to assist in deforming the insert 4620 to allow the insert to slide over the protrusion 4730 during installation. The connection between the retention features 4720 and the protrusions 4730 may be a snap fit connection.

[0206] In examples, retention features 4720 are provided to the intersections 4670 between adjacent segments 4660. Preferably, at least two retention features 4720 are provided, at least one on either side of the insert 4620, as shown in Fig. 8.

[0207] Those skilled in the art will appreciate that the insert 4620 assists in creating a flow element 4600 which is compact, is relatively inexpensive and simple to manufacture, and can be configured to provide laminar flow at low to medium flow rates while not leading to excessive pressure loss at high flow rates.5.4 AIR CIRCUIT

[0208] An air circuit 4170 in accordance with an aspect of the present technology is a conduit or a tube constructed and arranged to allow, in use, a flow of air to travel between two components such as RPT device 4000 and the patient interface 3000.5.5 BREATHING WAVEFORMS

[0209] Fig. 3 shows a model typical breath waveform of a person while sleeping. The horizontal axis is time, and the vertical axis is respiratory flow rate. While the parameter values may vary, a typical breath may have the following approximate values: tidal volume Vt 0.5L, inhalation time Ti 1.6s, peak inspiratory flow rate Qpeak 0.4 L / s, exhalation time Te 2.4s, peak expiratory flow rate Qpeak -0.5 L / s. The total duration of the breath, Tlol. is about 4s. The person typically breathes at a rate of about 15 breaths per minute (BPM), with Ventilation Vent about 7.5 L / min. A typical duty cycle, the ratio of Ti to Ttot, is about 40%.5.6 RESPIRATORY THERAPY MODES

[0210] Various respiratory therapy modes may be implemented by the disclosed respiratory therapy system.5.6.1 CPAP therapy

[0211] In some implementations of respiratory pressure therapy, the central controller 4230 sets the treatment pressure Pt according to the treatment pressure equation (1) as part of the therapy parameter determination algorithm 4329. In one such implementation, the amplitude A is identically zero, so the treatment pressure Pt (which represents a target value to be achieved by the interface pressure Pm at the current instant of time) is identically equal to the base pressure o throughout the respiratory cycle. Such implementations are generally grouped under the heading of CPAP therapy. In such implementations, there is no need for the therapy engine module 4320 to determine phase or the waveform template 11( ).

[0212] In CPAP therapy, the base pressure Po may be a constant value that is hard-coded or manually entered to the RPT device 4000. Alternatively, the central controller 4230 may repeatedly compute the base pressure Po as a function of indices or measures of sleep disordered breathing returned by the respective algorithms in the therapy engine module 4320, such as one or more of flow limitation, apnea, hypopnea, patency, and snore. This alternative is sometimes referred to as APAP therapy.

[0213] Fig. 2E is a flow chart illustrating a method 4500 carried out by the central controller 4230 to continuously compute the base pressure P as part of an APAP therapy implementation of the therapy parameter determination algorithm 4329, when the pressure support^ is identically zero.

[0214] The method 4500 starts at step 4520, at which the central controller 4230 compares the measure of the presence of apnea / hypopnea with a first threshold, and determines whether the measure of the presence of apnea / hypopnea has exceeded the first threshold for a predetermined period of time, indicating an apnea / hypopnea is occurring. If so, the method 4500 proceeds to step 4540; otherwise, the method 4500 proceeds to step 4530. At step 4540, the central controller 4230 compares the measure of airway patency with a second threshold. If the measure of airway patency exceeds the second threshold, indicating the airway is patent, the detected apnea / hypopnea is deemed central, and the method 4500 proceeds to step 4560; otherwise, the apnea / hypopnea is deemed obstructive, and the method 4500 proceeds to step 4550.

[0215] At step 4530, the central controller 4230 compares the measure of flow limitation with a third threshold. If the measure of flow limitation exceeds the third threshold, indicating inspiratory flow is limited, the method 4500 proceeds to step 4550; otherwise, the method 4500 proceeds to step 4560.

[0216] At step 4550, the central controller 4230 increases the base pressure Po by a predetermined pressure increment AP, provided the resulting treatment pressure Pt would not exceed a maximum treatment pressure Pmax. In one implementation, the predetermined pressure increment AP and maximum treatment pressure Pmax are 1 cmH20 and 25 cmH20 respectively. In other implementations, the pressure increment AP can be as low as 0.1 cmH20 and as high as 3 cmH20, or as low as 0.5 cmH20 and as high as 2 cmH20. In other implementations, the maximum treatment pressure Pmax can be as low as 15 cmH20 and as high as 35 cmH20, or as low as 20 cmH20 and as high as 30 cmH20. The method 4500 then returns to step 4520.

[0217] At step 4560, the central controller 4230 decreases the base pressure Po by a decrement, provided the decreased base pressure P would not fall below a minimum treatment pressure Pmin. The method 4500 then returns to step 4520. In one implementation, the decrement is proportional to the value of Po-Pmin, so that the decrease in Po to the minimum treatment pressure Pmin in the absence of any detected events is exponential. In one implementation, the constant of proportionality is set such that the time constant rof the exponential decrease of Po is 60 minutes, and the minimum treatment pressure Pmin is 4 cmH20. In other implementations, the time constant T could be as low as 1 minute and as high as 300 minutes, or as low as 5 minutes and as high as 180 minutes. In other implementations, the minimum treatment pressure Pmin can be as low as 0 cmH20 and as high as 8 cmH20, or as low as 2 cmH20 and as high as 6 cmH20. Alternatively, the decrement in Po could be predetermined, so the decrease in Po to the minimum treatment pressure Pmin in the absence of any detected events is linear.5.6.2 Bi-level therapy

[0218] In other implementations of this form of the present technology, the value of amplitude^ in equation (1) may be positive. Such implementations are known as bi-level therapy, because in determining the treatment pressure Pt using equation (1) with positive amplitude^, the therapy parameter determination algorithm 4329 oscillates the treatment pressure Pt between two values or levels in synchrony withthe spontaneous respiratory effort of the patient 1000. That is, based on the typical waveform templates 11( , f) described above, the therapy parameter determination algorithm 4329 increases the treatment pressure Pt to Po + A (known as the IPAP) at the start of, or during, or inspiration and decreases the treatment pressure Pt to the base pressure Po (known as the EPAP) at the start of, or during, expiration.

[0219] In some forms of bi-level therapy, the IPAP is a treatment pressure that has the same purpose as the treatment pressure in CPAP therapy modes, and the EPAP is the IPAP minus the amplitude A, which has a “small” value (a few cmH20) sometimes referred to as the Expiratory Pressure Relief (EPR). Such forms are sometimes referred to as CPAP therapy with EPR, which is generally thought to be more comfortable than straight CPAP therapy. In CPAP therapy with EPR, either or both of the IPAP and the EPAP may be constant values that are hard-coded or manually entered to the RPT device 4000. Alternatively, the therapy parameter determination algorithm 4329 may repeatedly compute the IPAP and / or the EPAP during CPAP with EPR. In this alternative, the therapy parameter determination algorithm 4329 repeatedly computes the EPAP and / or the IPAP as a function of indices or measures of sleep disordered breathing returned by the respective algorithms in the therapy engine module 4320 in analogous fashion to the computation of the base pressure P in APAP therapy described above.

[0220] In other forms of bi-level therapy, the amplitude A is large enough that the RPT device 4000 does some or all of the work of breathing of the patient 1000. In such forms, known as pressure support ventilation therapy, the amplitude A is referred to as the pressure support, or swing. In pressure support ventilation therapy, the IPAP is the base pressure Po plus the pressure support^, and the EPAP is the base pressure Po.

[0221] In some forms of pressure support ventilation therapy, known as fixed pressure support ventilation therapy, the pressure support^ is fixed at a predetermined value, e.g. 10 cmH20. The predetermined pressure support value is a setting of the RPT device 4000, and may be set for example by hard-coding during configuration of the RPT device 4000 or by manual entry through the input device 4220.

[0222] In other forms of pressure support ventilation therapy, broadly known as servo-ventilation, the therapy parameter determination algorithm 4329 takes as inputsome currently measured or estimated parameter of the respiratory cycle (e.g. the current measure Vent of ventilation) and a target value of that respiratory parameter (e.g. a target value Vtgt of ventilation) and repeatedly adjusts the parameters of equation (1) to bring the current measure of the respiratory parameter towards the target value. In a form of servo-ventilation known as adaptive servo-ventilation (ASV), which has been used to treat CSR, the respiratory parameter is ventilation, and the target ventilation value Vtgt is computed by the target ventilation determination algorithm 4328 from the typical recent ventilation Vtyp, as described above.

[0223] In some forms of servo-ventilation, the therapy parameter determination algorithm 4329 applies a control methodology to repeatedly compute the pressure support A so as to bring the current measure of the respiratory parameter towards the target value. One such control methodology is Proportional-Integral (PI) control. In one implementation of PI control, suitable for ASV modes in which a target ventilation Vtgt is set to slightly less than the typical recent ventilation Vtyp, the pressure support^ is repeatedly computed as:

[0224] where G is the gain of the PI control. Larger values of gain G can result in positive feedback in the therapy engine module 4320. Smaller values of gain G may permit some residual untreated CSR or central sleep apnea. In some implementations, the gain G is fixed at a predetermined value, such as -0.4 cmH2O / (L / min) / sec. Alternatively, the gain G may be varied between therapy sessions, starting small and increasing from session to session until a value that substantially eliminates CSR is reached. Conventional means for retrospectively analysing the parameters of a therapy session to assess the severity of CSR during the therapy session may be employed in such implementations. In yet other implementations, the gain G may vary depending on the difference between the current measure Vent of ventilation and the target ventilation Vtgt.

[0225] Other servo-ventilation control methodologies that may be applied by the therapy parameter determination algorithm 4329 include proportional (P), proportional-differential (PD), and proportional-integral-differential (PID).

[0226] The value of the pressure support A computed via equation (2) may be clipped to a range defined as [Amin, Amax], In this implementation, the pressure support A sits by default at the minimum pressure support Amin until the measure ofcurrent ventilation Vent falls below the target ventilation Vlgl, at which points starts increasing, only falling back to Amin when Vent exceeds Vtgt once again.

[0227] The pressure support limits Amin and Amax are settings of the RPT device 4000, set for example by hard-coding during configuration of the RPT device 4000 or by manual entry through the input device 4220.

[0228] In pressure support ventilation therapy modes, the EPAP is the base pressure o. As with the base pressure Po in CPAP therapy, the EPAP may be a constant value that is prescribed or determined during titration. Such a constant EPAP may be set for example by hard-coding during configuration of the RPT device 4000 or by manual entry through the input device 4220. This alternative is sometimes referred to as fixed-EPAP pressure support ventilation therapy. Titration of the EPAP for a given patient may be performed by a clinician during a titration session with the aid of PSG, with the aim of preventing obstructive apneas, thereby maintaining an open airway for the pressure support ventilation therapy, in similar fashion to titration of the base pressure Po in constant CPAP therapy.

[0229] Alternatively, the therapy parameter determination algorithm 4329 may repeatedly compute the base pressure P during pressure support ventilation therapy. In such implementations, the therapy parameter determination algorithm 4329 repeatedly computes the EPAP as a function of indices or measures of sleep disordered breathing returned by the respective algorithms in the therapy engine module 4320, such as one or more of flow limitation, apnea, hypopnea, patency, and snore. Because the continuous computation of the EPAP resembles the manual adjustment of the EPAP by a clinician during titration of the EPAP, this process is also sometimes referred to as auto-titration of the EPAP, and the therapy mode is known as auto-titrating EPAP pressure support ventilation therapy, or auto-EPAP pressure support ventilation therapy.5.6.3 High flow therapy

[0230] In other forms of respiratory therapy, the pressure of the flow of air is not controlled as it is for respiratory pressure therapy. Rather, the central controller 4230 controls the pressure generator 4140 to deliver a flow of air whose device flow rate Qd is controlled to a treatment or target flow rate Qtgt that is typically positive throughout the patient’s breathing cycle. Such forms are generally grouped under the heading of flow therapy. In flow therapy, the treatment flow rate Qtgt may be aconstant value that is hard-coded or manually entered to the RPT device 4000. If the treatment flow rate Qtgt is sufficient to exceed the patient’s peak inspiratory flow rate, the therapy is generally referred to as high flow therapy (HFT). Alternatively, the treatment flow rate may be a profile Qtgt(t) that varies over the respiratory cycle.5.7 OTHER REMARKS

[0231] A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in Patent Office patent files or records, but otherwise reserves all copyright rights whatsoever.

[0232] Unless the context clearly dictates otherwise and where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit, between the upper and lower limit of that range, and any other stated or intervening value in that stated range is encompassed within the technology. The upper and lower limits of these intervening ranges, which may be independently included in the intervening ranges, are also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the technology.

[0233] Furthermore, where a value or values are stated herein as being implemented as part of the technology, it is understood that such values may be approximated, unless otherwise stated, and such values may be utilized to any suitable significant digit to the extent that a practical technical implementation may permit or require it.

[0234] Furthermore, “approximately”, “substantially”, “about”, or any similar term used herein means + / - 5-10% of the recited value.

[0235] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this technology belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present technology, a limited number of the exemplary methods and materials are described herein.

[0236] When a particular material is identified as being used to construct a component, obvious alternative materials with similar properties may be used as a substitute. Furthermore, unless specified to the contrary, any and all components herein described are understood to be capable of being manufactured and, as such, may be manufactured together or separately.

[0237] It must be noted that as used herein and in the appended claims, the singular forms "a", "an", and "the" include their plural equivalents, unless the context clearly dictates otherwise.

[0238] All publications mentioned herein are incorporated herein by reference in their entirety to disclose and describe the methods and / or materials which are the subject of those publications. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present technology is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates, which may need to be independently confirmed.

[0239] The terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

[0240] The subject headings used in the detailed description are included only for the ease of reference of the reader and should not be used to limit the subject matter found throughout the disclosure or the claims. The subject headings should not be used in construing the scope of the claims or the claim limitations.

[0241] Although the technology herein has been described with reference to particular examples, it is to be understood that these examples are merely illustrative of the principles and applications of the technology. In some instances, the terminology and symbols may imply specific details that are not required to practice the technology. For example, although the terms "first" and "second" may be used, unless otherwise specified, they are not intended to indicate any order but may be utilised to distinguish between distinct elements. Furthermore, although process steps in the methodologies may be described or illustrated in an order, such an ordering is not required. Those skilled in the art will recognize that such ordering may bemodified and / or aspects thereof may be conducted concurrently or even synchronously.

[0242] It is therefore to be understood that numerous modifications may be made to the illustrative examples and that other arrangements may be devised without departing from the spirit and scope of the technology.5.8 REFERENCE SIGNS LIST

Claims

6 CLAIMS1. A flow element for a respiratory pressure therapy (RPT) device, the flow element comprising an outer housing and an insert, wherein the insert and housing together define a plurality of flow channels within the housing, wherein a transverse cross-section of the insert defines a simple open curve, the insert having a first side and an opposite second side, and wherein the insert is configured such that any notional line in a predetermined direction intersects the first side of the insert only once and intersects the second side of the insert only once.

2. The flow element of claim 1, wherein a cross-section of the insert comprises a plurality of flat segments.

3. The flow element of claim 1 or 2, wherein the flow channels are configured to flow a substantially equal mass flow of air, in use.

4. The flow element of any one of claims 1 to 3, wherein a ratio of a length of each flow channel to the cross-sectional area of the flow channel is between 5: 1 and 10: 1.

5. The flow element of any one of claims 1 to 4 wherein the cross-section of the insert is substantially invariable along the length of the insert.

6. The flow element of any one of claims 1 to 5, wherein the insert is manufactured by injection moulding in a mould.

7. The flow element of claim 6, wherein the predetermined direction is parallel to a line of draw of the mould.

8. A flow plate comprising the flow element of any one of claims 1 to 7.

9. The flow plate of claim 8 further comprising an inlet tube.

10. A method of manufacturing a flow element for a respiratory pressure therapy (RPT) device, the method comprising:• forming, by injection moulding, a housing for the flow element;• forming, by injection moulding, an insert having a transverse cross-section which defines a simple open curve; and• mounting the insert in the housing, such that insert and housing together define a plurality of flow channels.

11. The method of claim 10, wherein a mould used for forming the insert is a straight pull mould.

12. The method of claim 11, wherein a line of draw of the mould used for injection moulding the insert is orthogonal to a longitudinal axis of the insert.

13. The method of claim 10, 11 or 12, wherein the step of forming the housing comprises forming a flow plate comprising the housing.

14. The method of claim 13, wherein the flow plate further comprises an inlet tube.

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