Patient interface and components thereof

Abstract

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. The present technology also relates to components formed from nonwoven composites for use in medical devices or apparatus.

Claims

1. A patient interface comprising: a plenum chamber pressurisable to a therapeutic pressure of at least 4 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; a heat and moisture exchanger positioned within the plenum chamber, the heat and moisture exchanger comprising: a body constructed from a permeable, nonwoven composite formed with a fibrous material, the body having a first surface and a second surface; a passageway extending within the fibrous material between the first surface and the second surface and being formed as a through hole, the fibrous material forming a wall of the passageway so that a flow of gas is configured to contact the fibrous material that forms the wall; a seal-forming structure constructed and arranged to form a seal with a region of the patient's face surrounding an entrance to the patient's airways, said seal-forming structure having a hole therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient's nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the plenum chamber throughout the patient's respiratory cycle in use; and a positioning and stabilising structure to provide a force to hold the seal-forming structure in a therapeutically effective position on the patient's head; and wherein the body includes a first impedance and the passageway includes a second impedance less than the first impedance; wherein the fibrous material configured to absorb water vapor from exhaled air; wherein the permeable, nonwoven composite of the body configured to transfer the absorbed water vapor to inhaled air and increase the humidity of the flow; and wherein the passageway is elbow shaped and extends along two axes.

2. The patient interface of claim 1, wherein the body has a disk shape.

3. The patient interface of claim 1, wherein the first surface is a first planar surface and the second surface is a second planar surface opposite to the first planar surface.

4. The patient interface of claim 3, wherein the passageway extends along a single axis between the first surface and the second surface.

5. The patient interface of claim 1, wherein the body is a first body, the patient interface further comprising a second body, the first body and the second body being alignable.

6. The patient interface of claim 5, further comprising attachment means for aligning and stacking the first body and the second body.

7. The patient interface of claim 6, wherein the attachment means is a polymer spacer.

8. A patient interface comprising: a plenum chamber pressurisable to a therapeutic pressure of at least 4 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; the heat and moisture exchanger positioned within the plenum chamber, the heat and moisture exchanger comprising: a body constructed from a permeable, nonwoven composite formed with a fibrous material, the body having a first surface formed as a first planar surface and a second surface formed as a sidewall oriented substantially perpendicularly to the first surface; a passageway formed as a hole extending within the fibrous material between the first surface and the second surface, the fibrous material forming a wall of the passageway; a seal-forming structure constructed and arranged to form a seal with a region of the patient's face surrounding an entrance to the patient's airways, said seal-forming structure having a hole therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient's nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the plenum chamber throughout the patient's respiratory cycle in use; and a positioning and stabilising structure to provide a force to hold the seal-forming structure in a therapeutically effective position on the patient's head; and wherein the body includes a first impedance and the passageway includes a second impedance less than the first impedance; wherein the fibrous material configured to absorb water vapor from exhaled air; wherein the permeable, nonwoven composite of the body configured to transfer the absorbed water vapor to inhaled air and increase the humidity of the flow; and wherein the passageway is elbow shaped and extends along two axes.

9. The patient interface of claim 8, wherein the body has a disk shape.

10. The patient interface of claim 8, wherein the body is a first body, the patient interface further comprising a second body, the first body and the second body being alignable and stackable on top of each other.

11. The patient interface of claim 10, further comprising attachment means for aligning and stacking the first body and the second body.

12. The patient interface of claim 11, wherein the attachment means is a polymer spacer.

Description

7 BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) 7.1 Respiratory Therapy Systems

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

(4) FIG. 1B shows a system including a patient 1000 wearing a patient interface 3000, in the form of a nasal mask, receiving a supply of air at positive pressure from an RPT device 4000. Air from the RPT device is humidified in a humidifier 5000, and passes along an air circuit 4170 to the patient 1000.

(5) FIG. 1C shows a system including a patient 1000 wearing a patient interface 3000, in the form of a full-face mask, receiving a supply of air at positive pressure from an RPT device 4000. Air from the RPT device is humidified in a humidifier 5000, and passes along an air circuit 4170 to the patient 1000. The patient is sleeping in a side sleeping position.

(6) 7.2 Respiratory System and Facial Anatomy

(7) FIG. 2A shows an overview of a human respiratory system including the nasal and oral cavities, the larynx, vocal folds, oesophagus, trachea, bronchus, lung, alveolar sacs, heart and diaphragm.

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

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

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

(11) FIG. 2E is a further side view of a head. The approximate locations of the Frankfort horizontal and nasolabial angle are indicated. The coronal plane is also indicated.

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

(13) FIG. 2G shows a side view of the superficial features of a nose.

(14) FIG. 2H shows subcutaneal structures of the nose, including lateral cartilage, septum cartilage, greater alar cartilage, lesser alar cartilage, sesamoid cartilage, nasal bone, epidermis, adipose tissue, frontal process of the maxilla and fibrofatty tissue.

(15) FIG. 2I shows a medial dissection of a nose, approximately several millimeters from the midsagittal plane, amongst other things showing the septum cartilage and medial crus of greater alar cartilage.

(16) FIG. 2J shows a front view of the bones of a skull including the frontal, nasal and zygomatic bones. Nasal concha are indicated, as are the maxilla, and mandible.

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

(18) FIG. 2L shows an anterolateral view of a nose.

(19) 7.3 Patient Interface

(20) FIG. 3A shows a patient interface in the form of a nasal mask in accordance with one form of the present technology.

(21) FIG. 3B shows a schematic of a cross-section through a structure at a point. An outward normal at the point is indicated. The curvature at the point has a positive sign, and a relatively large magnitude when compared to the magnitude of the curvature shown in FIG. 3C.

(22) FIG. 3C shows a schematic of a cross-section through a structure at a point. An outward normal at the point is indicated. The curvature at the point has a positive sign, and a relatively small magnitude when compared to the magnitude of the curvature shown in FIG. 3B.

(23) FIG. 3D shows a schematic of a cross-section through a structure at a point. An outward normal at the point is indicated. The curvature at the point has a value of zero.

(24) FIG. 3E shows a schematic of a cross-section through a structure at a point. An outward normal at the point is indicated. The curvature at the point has a negative sign, and a relatively small magnitude when compared to the magnitude of the curvature shown in FIG. 3F.

(25) FIG. 3F shows a schematic of a cross-section through a structure at a point. An outward normal at the point is indicated. The curvature at the point has a negative sign, and a relatively large magnitude when compared to the magnitude of the curvature shown in FIG. 3E.

(26) FIG. 3G shows a cushion for a mask that includes two pillows. An exterior surface of the cushion is indicated. An edge of the surface is indicated. Dome and saddle regions are indicated.

(27) FIG. 3H shows a cushion for a mask. An exterior surface of the cushion is indicated. An edge of the surface is indicated. A path on the surface between points A and B is indicated. A straight line distance between A and B is indicated. Two saddle regions and a dome region are indicated.

(28) FIG. 3I shows the surface of a structure, with a one dimensional hole in the surface. The illustrated plane curve forms the boundary of a one dimensional hole.

(29) FIG. 3J shows a cross-section through the structure of FIG. 3I. The illustrated surface bounds a two dimensional hole in the structure of FIG. 3I.

(30) FIG. 3K shows a perspective view of the structure of FIG. 3I, including the two dimensional hole and the one dimensional hole. Also shown is the surface that bounds a two dimensional hole in the structure of FIG. 3I.

(31) FIG. 3L shows a mask having an inflatable bladder as a cushion.

(32) FIG. 3M shows a cross-section through the mask of FIG. 3L, and shows the interior surface of the bladder. The interior surface bounds the two dimensional hole in the mask.

(33) FIG. 3N shows a further cross-section through the mask of FIG. 3L. The interior surface is also indicated.

(34) FIG. 3O illustrates a left-hand rule.

(35) FIG. 3P illustrates a right-hand rule.

(36) FIG. 3Q shows a left ear, including the left ear helix.

(37) FIG. 3R shows a right ear, including the right ear helix.

(38) FIG. 3S shows a right-hand helix.

(39) FIG. 3T shows a view of a mask, including the sign of the torsion of the space curve defined by the edge of the sealing membrane in different regions of the mask.

(40) FIG. 3U shows a view of a plenum chamber 3200 showing a sagittal plane and a mid-contact plane.

(41) FIG. 3V shows a view of a posterior of the plenum chamber of FIG. 3U. The direction of the view is normal to the mid-contact plane. The sagittal plane in FIG. 3V bisects the plenum chamber into left-hand and right-hand sides.

(42) FIG. 3W shows a cross-section through the plenum chamber of FIG. 3V, the cross-section being taken at the sagittal plane shown in FIG. 3V. A mid-contact plane is shown. The mid-contact plane is perpendicular to the sagittal plane. The orientation of the mid-contact plane corresponds to the orientation of a chord 3210 which lies on the sagittal plane and just touches the cushion of the plenum chamber at two points on the sagittal plane: a superior point 3220 and an inferior point 3230. Depending on the geometry of the cushion in this region, the mid-contact plane may be a tangent at both the superior and inferior points.

(43) FIG. 3X shows the plenum chamber 3200 of FIG. 3U in position for use on a face. The sagittal plane of the plenum chamber 3200 generally coincides with the midsagittal plane of the face when the plenum chamber is in position for use. The mid-contact plane corresponds generally to the plane of the face when the plenum chamber is in position for use. In FIG. 3X the plenum chamber 3200 is that of a nasal mask, and the superior point 3220 sits approximately on the sellion, while the inferior point 3230 sits on the lip superior.

(44) FIG. 3Y shows a patient interface in the form of a nasal cannula in accordance with one form of the present technology.

(45) 7.4 RPT Device

(46) FIG. 4A shows an RPT device in accordance with one form of the present technology.

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

(48) 7.5 Humidifier

(49) FIG. 5A shows an isometric view of a humidifier in accordance with one form of the present technology.

(50) FIG. 5B shows an isometric view of a humidifier in accordance with one form of the present technology, showing a humidifier reservoir 5110 removed from the humidifier reservoir dock 5130.

(51) 7.6 Breathing Waveforms

(52) FIG. 6A shows a model typical breath waveform of a person while sleeping.

(53) 7.7 Screening, Diagnosis and Monitoring Systems

(54) FIG. 7A shows a patient undergoing polysomnography (PSG). The patient is sleeping in a supine sleeping position.

(55) FIG. 7B shows a monitoring apparatus for monitoring the condition of a patient. The patient is sleeping in a supine sleeping position.

(56) 7.8 Heat and Moisture Exchanger

(57) FIG. 8A shows a perspective view of a first example of a first version of a heat and moisture exchanger.

(58) FIG. 8B shows a side view of the heat and moisture exchanger of FIG. 8A.

(59) FIG. 8C shows a front view of the heat and moisture exchanger of FIG. 8A.

(60) FIG. 9A shows a perspective view of a second example of a first version of a heat and moisture exchanger.

(61) FIG. 9B shows a side view of the heat and moisture exchanger of FIG. 9A.

(62) FIG. 9C shows a front view of the heat and moisture exchanger of FIG. 9A.

(63) FIG. 10A shows a perspective view of a third example of a first version of a heat and moisture exchanger.

(64) FIG. 10B shows a side view of the heat and moisture exchanger of FIG. 10A.

(65) FIG. 10C shows a front view of the heat and moisture exchanger of FIG. 10A.

(66) FIG. 11 shows a schematic view of the heat and moisture exchanger of any one of the first example of FIG. 8A, the second example of FIG. 9A, or the third example of FIG. 10A.

(67) FIG. 12A shows a perspective view of a first example of a second version of a heat and moisture exchanger.

(68) FIG. 12B shows a side view of the heat and moisture exchanger of FIG. 12A.

(69) FIG. 12C shows a front view of the heat and moisture exchanger of FIG. 12A.

(70) FIG. 12D shows a detail view of the heat and moisture exchanger of FIG. 12A.

(71) FIG. 13 shows a schematic view of the heat and moisture exchanger in FIG. 12A.

(72) FIG. 14A shows a perspective view of a single heat and moisture exchanger connected to an attachment means.

(73) FIG. 14B shows a perspective view of a pair of heat and moisture exchangers stackable within an attachment means.

(74) FIG. 14C shows a perspective view of multiple heat and moisture exchangers stackable within an attachment means.

(75) FIG. 14D shows a front view of an alternate form of the attachment means containing at least one heat and moisture exchanger.

(76) FIG. 14E shows a view perspective view of the attachment means of FIG. 14D.

(77) FIG. 15 shows an example of a heat and moisture exchanger with an antibacterial filter.

(78) FIG. 16 shows an example of the placement of the heat and moisture exchanger (HMX) in the patient interface.

(79) FIG. 17 shows a perspective view of the attachment means of FIG. 14D connected from a patient interface.

(80) FIG. 18 shows a rear view of the patient interface of FIG. 17 connected to the attachment means.

(81) FIG. 19 shows a rear view of another patient interface connected to the attachment means of FIG. 14D.

DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY

(82) 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.

(83) 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.

(84) 8.1 Therapy

(85) 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.

(86) 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.

(87) In certain examples of the present technology, mouth breathing is limited, restricted or prevented.

(88) 8.2 Respiratory Therapy Systems

(89) 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 or 3800.

(90) 8.3 Patient Interface

(91) A non-invasive patient interface 3000 in accordance with one aspect of the present technology comprises the following functional aspects: a seal-forming structure 3100, a plenum chamber 3200, a positioning and stabilising structure 3300, a vent 3400, one form of connection port 3600 for connection to air circuit 4170, and a forehead support 3700. In some forms a functional aspect may be provided by one or more physical components. In some forms, one physical component may provide one or more functional aspects. In use the seal-forming structure 3100 is arranged to surround an entrance to the airways of the patient so as to maintain positive pressure at the entrance(s) to the airways of the patient 1000. The sealed patient interface 3000 is therefore suitable for delivery of positive pressure therapy.

(92) An unsealed patient interface 3800, in the form of a nasal cannula, includes nasal prongs 3810a, 3810b which can deliver air to respective nares of the patient 1000 via respective orifices in their tips. Such nasal prongs do not generally form a seal with the inner or outer skin surface of the nares. This type of interface results in one or more gaps that are present in use by design (intentional) but they are typically not fixed in size such that they may vary unpredictably by movement during use. This can present a complex pneumatic variable for a respiratory therapy system when pneumatic control and/or assessment is implemented, unlike other types of mask-based respiratory therapy systems. The air to the nasal prongs may be delivered by one or more air supply lumens 3820a, 3820b that are coupled with the nasal cannula-type unsealed patient interface 3800. The lumens 3820a, 3820b lead from the nasal cannula-type unsealed patient interface 3800 to a respiratory therapy device via an air circuit. The unsealed patient interface 3800 is particularly suitable for delivery of flow therapies, in which the RPT device generates the flow of air at controlled flow rates rather than controlled pressures. The vent or gap at the unsealed patient interface 3800, through which excess airflow escapes to ambient, is the passage between the end of the prongs 3810a and 3810b of the nasal cannula-type unsealed patient interface 3800 via the patient's nares to atmosphere.

(93) If a patient interface is unable to comfortably deliver a minimum level of positive pressure to the airways, the patient interface may be unsuitable for respiratory pressure therapy.

(94) The patient interface 3000 in accordance with one form of the present technology is constructed and arranged to be able to provide a supply of air at a positive pressure of at least 6 cmH2O with respect to ambient.

(95) The patient interface 3000 in accordance with one form of the present technology is constructed and arranged to be able to provide a supply of air at a positive pressure of at least 10 cmH2O with respect to ambient.

(96) The patient interface 3000 in accordance with one form of the present technology is constructed and arranged to be able to provide a supply of air at a positive pressure of at least 20 cmH2O with respect to ambient.

(97) 8.3.1 Seal-Forming Structure

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

(99) In one form the target seal-forming region is located on an outside surface of the seal-forming structure 3100.

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

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

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

(103) 8.3.1.1 Sealing Mechanisms

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

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

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

(107) In one form, the seal-forming structure comprises a tension portion. In use, the tension portion is held in tension, e.g. by adjacent regions of the sealing flange.

(108) In one form, the seal-forming structure comprises a region having a tacky or adhesive surface.

(109) In certain forms of the present technology, a seal-forming structure may comprise one or more of a pressure-assisted sealing flange, a compression sealing portion, a gasket sealing portion, a tension portion, and a portion having a tacky or adhesive surface.

(110) 8.3.1.2 Nose Bridge or Nose Ridge Region

(111) In one form, the non-invasive patient interface 3000 comprises a seal-forming structure that forms a seal in use on a nose bridge region or on a nose-ridge region of the patient's face.

(112) In one form, the seal-forming structure includes a saddle-shaped region constructed to form a seal in use on a nose bridge region or on a nose-ridge region of the patient's face.

(113) 8.3.1.3 Upper Lip Region

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

(115) In one form, the seal-forming structure includes a saddle-shaped region constructed to form a seal in use on an upper lip region of the patient's face.

(116) 8.3.1.4 Chin-Region

(117) In one form the non-invasive patient interface 3000 comprises a seal-forming structure that forms a seal in use on a chin-region of the patient's face.

(118) In one form, the seal-forming structure includes a saddle-shaped region constructed to form a seal in use on a chin-region of the patient's face.

(119) 8.3.1.5 Forehead Region

(120) In one form, the seal-forming structure that forms a seal in use on a forehead region of the patient's face. In such a form, the plenum chamber may cover the eyes in use.

(121) 8.3.1.6 Nasal Pillows

(122) In one form the seal-forming structure of the non-invasive patient interface 3000 comprises a pair of nasal puffs, or nasal pillows, each nasal puff or nasal pillow being constructed and arranged to form a seal with a respective naris of the nose of a patient.

(123) Nasal pillows in accordance with an aspect of the present technology include: a frusto-cone, at least a portion of which forms a seal on an underside of the patient's nose, a stalk, a flexible region on the underside of the frusto-cone and connecting the frusto-cone to the stalk. In addition, the structure to which the nasal pillow of the present technology is connected includes a flexible region adjacent the base of the stalk. The flexible regions can act in concert to facilitate a universal joint structure that is accommodating of relative movement both displacement and angular of the frusto-cone and the structure to which the nasal pillow is connected. For example, the frusto-cone may be axially displaced towards the structure to which the stalk is connected.

(124) 8.3.2 Plenum Chamber

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

(126) In certain forms of the present technology, the plenum chamber 3200 does not cover the eyes of the patient in use. In other words, the eyes are outside the pressurised volume defined by the plenum chamber. Such forms tend to be less obtrusive and/or more comfortable for the wearer, which can improve compliance with therapy.

(127) In certain forms of the present technology, the plenum chamber 3200 is constructed from a transparent material, e.g. a transparent polycarbonate. The use of a transparent material can reduce the obtrusiveness of the patient interface, and help improve compliance with therapy. The use of a transparent material can aid a clinician to observe how the patient interface is located and functioning.

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

(129) 8.3.3 Positioning and Stabilising Structure

(130) The seal-forming structure 3100 of the patient interface 3000 of the present technology may be held in sealing position in use by the positioning and stabilising structure 3300.

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

(132) In one form the positioning and stabilising structure 3300 provides a retention force to overcome the effect of the gravitational force on the patient interface 3000.

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

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

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

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

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

(138) In one form of the present technology, a positioning and stabilising structure 3300 comprises a strap constructed from a laminate of a fabric patient-contacting layer, a foam inner layer and a fabric outer layer. In one form, the foam is porous to allow moisture, (e.g., sweat), to pass through the strap. In one form, the fabric outer layer comprises loop material to engage with a hook material portion.

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

(140) In one form of the present technology, the positioning and stabilising structure comprises a first tie, the first tie being constructed and arranged so that in use at least a portion of an inferior edge thereof passes superior to an otobasion superior of the patient's head and overlays a portion of a parietal bone without overlaying the occipital bone.

(141) In one form of the present technology suitable for a nasal-only mask or for a full-face mask, the positioning and stabilising structure includes a second tie, the second tie being constructed and arranged so that in use at least a portion of a superior edge thereof passes inferior to an otobasion inferior of the patient's head and overlays or lies inferior to the occipital bone of the patient's head.

(142) In one form of the present technology suitable for a nasal-only mask or for a full-face mask, the positioning and stabilising structure includes a third tie that is constructed and arranged to interconnect the first tie and the second tie to reduce a tendency of the first tie and the second tie to move apart from one another.

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

(144) In certain forms of the present technology, a positioning and stabilising structure 3300 comprises a strap constructed to be breathable to allow moisture vapour to be transmitted through the strap,

(145) In certain forms of the present technology, a system is provided comprising more than one positioning and stabilizing structure 3300, each being configured to provide a retaining force to correspond to a different size and/or shape range. For example the system may comprise one form of positioning and stabilizing structure 3300 suitable for a large sized head, but not a small sized head, and another. suitable for a small sized head, but not a large sized head.

(146) 8.3.4 Vent

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

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

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

(150) The vent 3400 may be located in the plenum chamber 3200. Alternatively, the vent 3400 is located in a decoupling structure, e.g., a swivel.

(151) 8.3.5 Decoupling Structure(s)

(152) In one form the patient interface 3000 includes at least one decoupling structure, for example, a swivel or a ball and socket.

(153) 8.3.6 Connection Port

(154) Connection port 3600 allows for connection to the air circuit 4170.

(155) 8.3.7 Forehead Support

(156) In one form, the patient interface 3000 includes a forehead support 3700.

(157) 8.3.8 Anti-Asphyxia Valve

(158) In one form, the patient interface 3000 includes an anti-asphyxia valve.

(159) 8.3.9 Ports

(160) In one form of the present technology, a patient interface 3000 includes one or more ports that allow access to the volume within the plenum chamber 3200. In one form this allows a clinician to supply supplementary oxygen. In one form, this allows for the direct measurement of a property of gases within the plenum chamber 3200, such as the pressure.

(161) 8.3.10 Heat and Moisture Exchanger

(162) A heat and moisture exchanger can be included in the patient interface. The heat and moisture exchanger is a component that is intended to help humidify and warm air flowing into the airways of the patient. This helps prevent complications due to drying of the respiratory mucosa.

(163) The heat and moisture exchanger may be designed in order to capture exhaled water vapor in order to improve humidity during use of the patient interface 3000. Accordingly, the heat and moisture exchanger increases the impedance of the airflow through the plenum chamber 3200. The increased impedance may assist in allowing greater moisture retention. But as described below, increased impedance may also decrease carbon dioxide washout. Accordingly, a heat and moisture exchanger may be designed in order to increase moisture capture without substantially decreasing gas washout (e.g., in order to limit carbon dioxide build-up in the plenum chamber 3200).

(164) In one form of the present technology, the heat and moisture exchanger 800 comprises a nonwoven composite having a first planar surface 802, an opposite second planar surface 804 and a sidewall 806. The heat and moisture exchanger also comprises at least one vent 808 on the first planar surface 802. The nonwoven composite is formed such that it is air permeable to all the directions. In other words, the nonwoven composite is bidirectionally permeable to air through the first planar surface and the second planar surface. The vent 808 allows a flow of gas through the first planar surface, that is, it allows air to flow in both directions through the first planar surface.

(165) FIGS. 8A to 10C show examples of a heat and moisture exchanger 800. A cross-sectional schematics is shown as 810 in FIG. 11. Air from an air source can, for example, flow 812 into the heat and moisture exchanger 800. Air can flow 812 at an angle through the heat and moisture exchanger 800 via the second planar surface 804 to be received by a patient at the first planar surface 802. For example, the illustrated schematic 810 shows the flow 812 may be substantially perpendicular with respect to the second planar surface 804. However, the flow 812 may also be oriented at an oblique angle with respect to the second surface. In some forms, an angle between the flow 812 and the second surface 804 may be at least about +/?1?. In some forms, an angle between the flow 812 and the second surface 804 may be at least about +/?10?. In some forms, an angle between the flow 812 and the second surface 804 may be at least about +/?25?. In some forms, an angle between the flow 812 and the second surface 804 may be about +/?45?. The angle may depend on the orientation of the air circuit 4170. The air can then flow 814 out of the heat and moisture exchanger 800 through the first planar surface 802 to be received by the patient Similarly, as shown in FIG. 13, air can flow 852 through the heat and moisture exchanger 840 (illustrated as schematic 850) perpendicularly with respect from an inlet tubing to a plenum chamber via the second planar surface 844 to the first planar surface 842 and thus flow 854 out from the heat and moisture exchanger to be received by the patient. Alternatively, the flow 852 and/or flow 854 may be oriented at an oblique angle (e.g., at least about +/?1?, +/?10?, +/?25?, or +/?45?) with respect to the first or second planar surfaces 842, 844. The angle may similarly depend on the orientation of the air circuit 4170.

(166) Advantageously, as the nonwoven composite is a porous material, air permeability across the heat and moisture exchanger can be obtained. Further, as fibre arrangements can be tuned, the permeability can be controlled to regulate the flow of air.

(167) The vent 808 allows a flow 816 of gas through the first planar surface 802. As shown in FIG. 11, the vent 808 allows a flow 816 of air between the first planar surface 802 and the second planar surface 804. The gas or exhaled air from the patient passes through the nonwoven composite via the vent 808 and exits 818 via the second planar surface 804. In this regard, the vent 808 allows gas to flow in an opposite direction 816 to the air 814 from the air source.

(168) Advantageously, the vent 808 facilitates the flow of air from a high pressure region to a low pressure region. When a patient breathes out, a high pressure region is created within the plenum chamber. The high pressure region can be quickly de-pressurised through the flow of air via the vent 808. In this way, carbon dioxide that is breathed out by the patient can be quickly removed from the plenum chamber.

(169) For example, the vents 808 may decrease the impedance by allowing the exhaled air to more freely flow through the nonwoven composite. However, the fibrous material of the nonwoven composite may form the boundary of the vents 808 through the heat and moisture exchanger 800. Thus, flow 816 may still contact the nonwoven composite, which may absorb water vapor in the exhaled gas, even while not traveling directly through the solid nonwoven composite. The carbon dioxide may be able to exit 818 without substantial build up in a plenum chamber, while also maintaining sufficient levels of moisture capture.

(170) Advantageously, the combination of these two features act synergistically to retain heat and moisture in the heat and moisture exchanger. When gas is expelled from the airways of a patient and exits the heat and moisture exchanger 800 via the vent 808, heat and moisture can be captured within the nonwoven composite. This is due to the high surface area and structure created by the web of fibres. As air from the air source pass through the heat and moisture exchanger 800 to be breathe in by the patient, heat and moisture which are trapped within the nonwoven composite is carried out by this air, and can be delivered to the patient's airways. In this regard, the heat and moisture content of the air that is delivered can be regulated and an external humidifier and/or heating element is not required.

(171) FIGS. 12A to 13 show another example of the heat and moisture exchanger 840. The heat and moisture exchanger 840 comprises a nonwoven composite having a first planar surface 842, an opposite second planar surface 844 and a sidewall 846. The heat and moisture exchanger 840 also comprises at least one vent 848 on the first planar surface 842. The nonwoven composite is formed such that it is bidirectionally permeable to air through the first planar surface 842 and the second planar surface 844. The vent 848 allows a flow of gas through the first planar surface 842, that is, it allows air to flow in both directions through the first planar surface 842.

(172) A cross-sectional schematics is shown as 850 in FIG. 13. Air from an air source can flow 852 into the heat and moisture exchanger 840 via the second planar surface 844. The air can then flow 854 out of the heat and moisture exchanger 840 through the first planar surface 842. The vent 848 allows a flow 856 of gas through the first planar surface 842. The gas or exhaled air from the patient passes through the nonwoven composite via the vent 848 and exits 858 via the sidewall 846.

(173) In some forms, the sidewall 846 may include at least one opening 847. For example, a plurality of openings 847 may be disposed around the perimeter of the heat and moisture exchanger 840. The exit flow 858 may exhaust through the openings 847 in a direction substantially perpendicularly to the flow 852.

(174) In certain forms, the one or more openings 847 may assist in diffusing airflow (e.g., the flow 858) that exits the heat and moisture exchanger 840. The diffusion of the flow 858 may assist with sound dampening related to airflow through the heat and moisture exchanger 840 (e.g., by reducing or eliminating whistling or other sounds that could disturb a patient's sleep).

(175) In one form, forming a vent 848 with a tortuous path (e.g., by angling the pathway 849 of the vent 848 such that a through-hole configuration is avoided), may cause sound to be more readily transmitted through the non-woven fabric and to be absorbed by the material. The sound is also diffused (redirected or scattered) into a wider space which may make the sound less coherent and may reduce echos.

(176) In some forms, the sidewall 846 may be formed from a permeable material and may allow air flow (e.g., the exit flow 858 in FIG. 13) to pass through the sidewall 846. In this example, the sidewall 846 may have a greater permeability than the planar surfaces 842, 844 in order to assist in exhausting carbon dioxide.

(177) This arrangement advantageously minimises the mixing of the inhalable air and the exhaled air. Further, as a portion of the vent 848 is substantially parallel to the first and second planar surfaces 842, 844, and the exhaled air travels a greater distance within the heat and moisture exchanger 840, more heat and moisture can be trapped within.

(178) In certain forms the vent 848 is configured to allow a continuous vent flow from an interior of the plenum chamber 3200 to ambient whilst the pressure within the plenum chamber is positive with respect to ambient. The vent 3400 is configured such that the vent flow rate has a magnitude sufficient to reduce rebreathing of exhaled CO.sub.2 by the patient while maintaining the therapeutic pressure in the plenum chamber in use.

(179) One form of vent of a heat and moisture exchanger in accordance with the present technology comprises a plurality of holes, for example, about 20 to about 80 holes, or about 40 to about 60 holes, or about 45 to about 55 holes.

(180) The vent (e.g., vent 808) can allow the passage of gas between the first planar surface 802 and the second planar surface 804 as illustrated in FIG. 11. Alternatively (or additionally), the vent (e.g., vent 848) can allow the passage of gas between the first planar surface 842 and the sidewall 846 as illustrated in FIG. 12D.

(181) For example, a pathway 849 may be formed through the body of the heat and moisture exchanger 840 in order to connect a vent 848 to an opening 847 in the sidewall 846. In the illustrated example, the pathway 849 may connect a single vent 848 to a single opening 847, although in other examples, multiple vents 848 and/or multiple openings 847 may be connected to a single pathway 849. For example, vents 848 oriented in concentric patterns (see e.g., FIGS. 8C and 9C) may include a single pathway 849 connecting both vents 848 to a single opening 847.

(182) In certain forms, the pathway 849 may be formed with a substantially elbow shape extending between the first planar surface 842 and the sidewall 846.

(183) In some forms, the pathways 849 and the vents 848 may be similar to the vents 808 described above. The nonwoven composite may line (e.g., form the boundary of) the pathway 849. Thus, the nonwoven composite may not substantially interfere (e.g., provide an elevated impedance) to carbon dioxide in the flow 856. However, the airflow flowing through the pathways 849 may contact the fibrous material of the nonwoven composite, which may absorb the water vapor in the airflow (e.g., thereby maintaining absorption but limiting impedance).

(184) The heat and moisture exchanger can comprise a plurality of vents. The vents may be arranged in any suitable pattern, and may be uniformly or randomly dispersed. For example, the vents can be arranged in at least one concentric pattern on the heat and moisture exchanger. FIGS. 10A to 10C and 12A to 12D show an example of the vents 808, 848 being arrayed as a concentric pattern (e.g., a singular circular pattern) on the heat and moisture exchanger 800, 840. FIGS. 8A to 9C show other examples of vents 808 being arranged in two concentric patterns (see e.g., FIGS. 9A and 9C) or three concentric patterns (see e.g., FIGS. 8A and 8C) on the heat and moisture exchanger 800. Alternatively, the vents can be arranged in a spiral pattern, or in any other patterns that is suitable for use.

(185) The vents can have a diameter of about 0.1 mm to about 2 mm

(186) The pattern and number of vents can be selected such that it reduces a flow resistance of air. For example, the air flow resistance can be defined as R=?p/?S, where ?p is the air pressure difference (Pa) across the heat and moisture exchanger, ? is the linear air velocity (m/s) and S is the cross sectional area of the heat and moisture exchanger perpendicular to the direction of the flow (m.sup.2).

(187) When combined with the nonwoven composite, the flow resistance (or impedance) of the heat and moisture exchanger can be such that the patient feels no or minimal resistance to breathing in and out. This provides a therapeutically effective air pressure to a patient when the heat and moisture exchanger is incorporated in the patient interface.

(188) The heat and moisture exchanger can have a low through impedance. The impedance can be less than about 150 L/min at 3 cm H.sub.20. The impedance of the nonwoven composite (first impedance) can be less than about 150 L/min at 3 cm H.sub.2. The impedance of the vent (second impedance) can be less than about 120 L/min at 3 cm H.sub.20, or preferably less than about 80 L/min at 3 cm H.sub.20. The heat and moisture exchanger can add about 18 mg/L to about 25 mg/L absolute humidity at 10 cm H.sub.2O therapy pressure. Advantageously, after being saturated with water, humidification performance does not decrease and impedance does not increase.

(189) The heat and moisture exchanger can have a moisture exchange rate of at least about 1 mg/s. The heat and moisture exchanger can have a moisture exchange rate of at least about 3 mg/s. In other examples, the moisture exchange rate is at least about 5 mg/s. The heat and moisture exchanger can have a moisture exchange rate of at least about 7 mg/s.

(190) The heat and moisture exchanger can have an air permeability of more than about 1 mL/s/mm.sup.2. The heat and moisture exchanger can have an air permeability of more than about 3 mL/s/mm.sup.2. In other embodiments, the air permeability is more than about 5 mL/s/mm.sup.2. The heat and moisture exchanger can have an air permeability of more than about 7 mL/s/mm.sup.2.

(191) The heat and moisture exchanger can have a suitable heat conductivity as defined by

(192) $?=\frac{\mathrm{QL}}{\mathrm{At}\left(T_1-T_2\right)},$
where Q is the heat flow (W) passing in time t (h) through an area A (m.sup.2) of the composite thickness L (m) at a temperature difference (T.sub.1?T.sub.2) (? C.).

(193) The heat and moisture exchanger can have a thickness of about 2 mm to about 20 mm In other embodiments, the thickness is about 3 mm to about 15 mm This provides the heat and moisture exchanger with sufficient rigidity to facilitate its insertion into, for example, the patient interface.

(194) As illustrated in FIGS. 14A to 14C, two or more of the he heat and moisture exchangers (e.g., heat and moisture exchanger 800 and/or heat and moisture exchanger 840) can also be alignable and stackable on top of each other. In other words, two or more heat and moisture exchangers may be positioned adjacent to each other. This allows a patient to adjust and control the amount of heat and moisture to be delivered into the airways of the patient. To this end, when two or more heat and moisture exchangers are stacked together, the amount of heat and moisture retained in the heat and moisture exchanger can be increased. When the heat and moisture exchangers (e.g., heat and moisture exchanger(s) 800 and/or heat and moisture exchanger(s) 840) are stacked such that the vents can be aligned, the impedance can at least be maintained. FIGS. 14A to 14C illustrate the heat and moisture exchanger 800, but the description and figures may be equally applicable for the heat and moisture exchanger 840.

(195) The heat and moisture exchanger 800 (or alternatively the heat and moisture exchanger 840) can further comprise an attachment means 900 for aligning and stacking the two or more heat and moisture exchangers 800. The attachment means 900 can be a bayonet connector or can be an adhesive. The attachment means 900 can also be a polymer spacer. The attachment means 900 can also provide a physical space between the adjacent heat and moisture exchangers. This may eliminate, or at least reduce, the need for alignment of the vents.

(196) For example, as illustrated in FIG. 14A, a single heat and moisture exchanger 800 may be connected to the attachment means 900. A patient may selectively add additional heat and moisture exchangers 800 as illustrated in FIG. 14B (e.g., two total heat and moisture exchangers 800) and FIG. 14C (e.g., three total heat and moisture exchangers 800). In some forms, the combined structure connected to the attachment means 900 may be the heat and moisture exchanger 800, which is made up of multiple nonwoven components (e.g., singular heat and moisture exchangers 800). As mentioned above, the heat and moisture exchanger 800 may be replaced with the heat and moisture exchanger 840, or the heat and moisture exchangers 800, 840 may be used in combination with one another.

(197) In FIGS. 14A to 14C, the heat and moisture exchanger(s) (e.g., one or more heat and moisture exchangers 800, one or more heat and moisture exchangers 840, or a combination of both heat and moisture exchangers 800, 840) may be secured to the attachment means 900 so that the heat and moisture exchanger(s) is not movable relative to the attachment means 900 in use.

(198) FIGS. 14D and 14E illustrates another form of an attachment means 940. The attachment means 940 may have an outer body 942 holding one or more heat and moisture exchangers 800, 840. Opposing ends 944 of the outer body 942 may include an interface for allowing the patient to handle the attachment means 940.

(199) As shown in FIGS. 16 to 19, the heat and moisture exchanger(s) 800 (or alternatively the heat and moisture exchanger 840) may be positioned in the plenum chamber 3200 proximate to the air circuit 4170 so that pressurized air flowing into the plenum chamber is directed through the heat and moisture exchanger(s) 800, 840.

(200) As shown in FIG. 14E, one side of the outer body 942 may include one or more tabs 946, which may engage with the connection port 3600 of the plenum chamber 3200.

(201) As shown in FIGS. 17 and 18, the attachment means 940 may be inserted into the plenum chamber 3200 prior to use, and connected to the connection port 3600. For example, the tabs 946 face away from the patient in use, and connect to the connection port 3600 so that the heat and moisture exchanger 800 is positioned within the plenum chamber 3200. The outer body 942 (via the tabs 946) may mechanically engage the connection port 3600 (e.g., using a snap fit, friction fit, and/or press fit). Once the outer body 942 is connected to the connection port 3600, the heat and moisture exchanger 800 (and/or 840not shown) may be positioned proximate to the connection port 3600 so that airflow entering the plenum chamber 3200 via the air circuit 4170 passes through the heat and moisture exchanger 800. The attachment means 900 may be similarly connected to the plenum chamber 3200.

(202) As shown in FIG. 19, the outer body 942 may be similarly connected to the connection port 3600 (see e.g., FIG. 18 illustrating a similar connection port of the patient interface 3000) of a nasal patient interface 6000 with a plenum chamber 6200 that provides pressurized air only to the patient's nares.

(203) In some forms, the pressurized air from the air circuit 4170 may be directed through the heat and moisture exchanger(s) 800 and into the plenum chamber 3200. The pressurized air may pass through the nonwoven composite and pick up the trapped water vapor, thereby humidifying the flow of air entering the plenum chamber 3200. The patient may then inhale this humidified air.

(204) In some forms, the patient may exhale water vapor as part of the normal respiratory process. The nonwoven composite may assist in trapping the water vapor from exhausting to ambient so that the water vapor can be reintroduced into the patient's lungs.

(205) In certain forms, the heat and moisture exchanger(s)' position proximate to an interface between the air circuit 4170 and an opening of the plenum chamber 3200 may allow the heat and moisture exchanger(s) 800 to act as a vent to exhaust exhaled air to ambient. However, as described above, the nonwoven material, while permeable, may have a relatively high impedance that slows airflow through the material. In order to limit the build-up of carbon dioxide, the vents 808, 848 may allow the carbon dioxide to more easily exhaust to ambient through a lower impedance opening.

(206) As described above, the high pressure in the plenum chamber 3200 (e.g., as a result of the flow of air from the air circuit 4170 and the exhaled air from the patient's lungs) may assist the exhaled air to flow through the vents 808 (or vents 848 when the heat and moisture exchanger 840 is used) and exit the plenum chamber 3200.

(207) In certain forms, the exhaled, humidified air (e.g., as a result of natural respiration) exhausts through the vents 808 and/or 848 which are formed directly through the nonwoven composite. In either form (e.g., the vent 808 between the first and second surfaces 802, 804 in FIGS. 8A to 11, or the vent 848 between the first surface 842 and the sidewall 846 in FIGS. 12A to 13), the wall of the vent 808, 848 (e.g., the pathway 849) is formed by the nonwoven composite. The flow of air through the vents 808, 848 thus contacts the nonwoven composite even without substantially experiencing the impedance of the composite. The fibrous material of the nonwoven composite may absorb water vapor from the exhausted air so that the water vapor can be returned to the plenum chamber 3200 and eventually the patient's lungs.

(208) 8.3.11 Nonwoven Composite for Heat and Moisture Exchanger

(209) The heat and moisture exchanger can be formed from a nonwoven composite as disclosed herein.

(210) For example, the nonwoven composite can be a multi-layered nonwoven composite. The multi-layered composite can comprise at least two layers, and can be up to 10 layers.

(211) For example, the heat and moisture exchanger can comprise a first nonwoven composite and a second nonwoven composite, the first nonwoven composite and the second nonwoven composite may be positioned adjacent to each other. Alternatively, the first nonwoven composite and the second nonwoven composite may be aligned and stacked on top of each other. The first nonwoven composite and the second nonwoven composite can be stacked such that the vents in the first and second nonwoven composites are aligned.

(212) The nonwoven composite can have a water contact angle of less than about 90?.

(213) The nonwoven composite can have a mass change of at least 20% at a relative humidity of 50%. The mass change can be measured using dynamic vapour sorption.

(214) The nonwoven composite can have a porosity of at least 20%.

(215) The nonwoven composite can have a density of at least 50 fibres/cm.

(216) The nonwoven composite can have an internal surface area of about 5 m.sup.2/g to about 100 m.sup.2/g.

(217) The nonwoven composite can be treated with a wetting agent for allowing rapid moisture penetration. The wetting agent can be applied to an inner layer of a multi-layered composite. Alternatively, an inner layer can be composed of rayon fibres for improving the moisture absorbent property of the heat and moisture exchanger.

(218) As shown in FIG. 15, the heat and moisture exchanger 800 (or the heat and moisture exchanger 840; not shown) can further comprise a filter layer 910. The filter layer 910 can be an anti-bacterial filter layer. The filter layer 910 can be formed within the heat and moisture exchanger 800 during the fabrication thereof, or can be sandwiched between a plurality of heat and moisture exchangers 800 and/or 840. For example, the filter layer 910 may be separate from the heat and moisture exchangers 800, and may be positioned between adjacent heat and moisture exchangers 800 within an attachment means 900 (e.g., similar to FIGS. 14B and 14C).

(219) 8.3.12 Nonwoven Composite in General

(220) The nonwoven composite can be a multi-layered nonwoven composite. The multi-layered composite can comprise at least two layers, and can be up to 10 layers. One of the layers can comprise microfibers. The layer comprising microfibers can be a patient-contacting layer of the nonwoven composite.

(221) The nonwoven composite can be formed from fibres which are spunbond, meltblown, or from a combination thereof.

(222) The fibres can be a single component fibre or a bi-component fibre. A multi-component fibre is also envisioned. Bi-component fibres are fibres which are extruder with two different types of polymer within a single fibre. The components do not mix with each other, but by changing the physical relationship of the two components within the fibre, and by changing the composition of the components, the properties of the final fibre can be altered. Examples of bi-component fibres include side-by-side, eccentric sheath/core, citrus, island-in-the-sea, segmented pie, segmented circle, segmented ribbon, trilobal sheath/core and trilobal side-by-side.

(223) The non-woven composite may comprise fine fibres and/or fibres with high surface area. Advantageously, the non-woven composite is capable of effectively absorbing moisture. Fibres with high surface area may include engineered fibres having various cross-sectional geometry, such as trilobal or multilobal. Preferably, the non-woven material may comprise fine fibres which leads to a higher surface area and therefore better moisture absorption.

(224) The fibres can have a combination of hydrophilic and hydrophobic components. The ratio of hydrophilic to hydrophobic component can be tuned to regulate the retention of heat and/or moisture. For example, the ratio can be from about 1:99 to about 99:1, about 10:90 to about 90:10, about 20:80 to about 80:20, about 30:70 to about 70:30, about 40:60 to about 60:40, or about 50:50.

(225) The nonwoven fibres can have a diameter of about 0.5 ?m to about 50 ?m.

(226) The nonwoven composite can be moulded to give it surface texturisation. For example, the texture can be of at least 1 cm deep.

(227) The nonwoven composite can have a thickness of about 1 mm to about 5 cm.

(228) The nonwoven composite can have a density of about 0.05 g/cm.sup.3 to 5.0 g/cm.sup.3.

(229) The nonwoven composite can be formed from a web of fibres. The fibres can be a synthetic polymer fibre and/or a natural plant or animal fibre such as seed fibre, leaf fibre, bast fibre, fruit fibre, stalk fibre, chitin, chitosan, collagen or keratin. Examples of natural plant fibres are cotton (or other cellulose fibres), kapok, coir, flax, hemp, jute, ramie, abaca, henequen, and sisal. Examples of synthetic polymer fibres are polyamides, polyacrylonitrile, polyethylene, polypropylene, polyethylene terephthalate, polyester, regenerated cellulose fibres, or rayon and their co-polymer derivatives such as co-polyester, co-polypropylene etc. In some embodiments, the fibres can be selected from polyethylene, polypropylene, polyethylene terephthalate, polyester, rayon, viscose, cotton, or a combination thereof.

(230) The fibres can be further functionalised with a functional coating on the fibres. For example, the fibres can be functionalised with hydrophilic moieties selected from hydroxyl, carboxyl, amino, sulfinyl, sulfonyl, phosphoryl, or a combination thereof.

(231) Advantageously, the nonwoven composite can be washed and re-used.

(232) Alternatively, the nonwoven composite can further comprise a hydrophilic coating on the first planar surface and/or the second planar surface. The hydrophilic coating can be selected from various cross-linking polymers such as derivatives of polysiloxanes or it can be achieved by other treatments like plasma.

(233) Alternatively, the nonwoven composite can further comprise a hydrophobic coating on the first planar surface and/or the second planar surface. The hydrophobic coating can be selected from combination of chemicals such as polydimethylsiloxane (PDMS).

(234) The nonwoven composite can further comprises an anti-bacterial coating. The anti-bacterial coating can be based on silicone based softeners, silver salts, zinc pyrithione, silane quarternary ammonia compounds, Polyhexamethylene Buguanide (PHMB), or the likes. Alternatively, the nonwoven composite can comprise a filter layer, the filter layer is an anti-bacterial layer. In this way, the fabrication process does not have to be substantially modified and the anti-bacterial substance will not adversely affect the properties of the fibres.

(235) Alternatively, as illustrated in FIG. 15, the Meltblown nonwoven membrane can be sandwiched between two or more nonwoven composites in order to achieve air filtration and bacterial filtration.

(236) The nonwoven composite further comprises an olfactory coating or layer. The olfactory coating can be selected from various essential oils. The essential oils can be used as a form of aromatherapy for inducing relaxation and/or restful sleep. Examples of essential oils include, but not limited to, sweet orange, peppermint, menta arvensis, cedarwood, lemon, eucalyptus globulus, spearmint, lavender, bergamot, rose, chamomile, ylang-ylang, tea tree, jasmine, or a combination thereof. The olfactory coating can be coated on the fibres or impregnated into the fibres. This can be done during the fabrication of the nonwoven composite. Alternatively, the nonwoven composite can comprise a layer, the layer is an olfactory layer. In this way, the fabrication process does not have to be substantially modified and the olfactory substance will not adversely affect the properties of the fabric fibers. Further, the layer can be switched out when all or most of the olfactory substance has defused off.

(237) 8.4 RPT Device

(238) 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.

(239) 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 6 cmH2O, or at least 10 cmH2O, or at least 20 cmH2O.

(240) 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.

(241) 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.

(242) 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.

(243) The RPT device 4000 may have an electrical power supply, one or more input devices, a central controller, a therapy device controller, a pressure generator 4140, one or more protection circuits, memory, transducers, data communication interface and one or more output devices. Electrical components may be mounted on a single Printed Circuit Board Assembly (PCBA). In an alternative form, the RPT device 4000 may include more than one PCBA.

(244) 8.4.1 RPT Device Mechanical & Pneumatic Components

(245) 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.

(246) 8.4.1.1 Air Filter(s)

(247) 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.

(248) In one form, an inlet air filter 4112 is located at the beginning of the pneumatic path upstream of a pressure generator 4140.

(249) In one form, 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 or 3800.

(250) 8.4.1.2 Muffler(s)

(251) An RPT device in accordance with one form of the present technology may include a muffler 4120, or a plurality of mufflers 4120.

(252) In one form of the present technology, an inlet muffler 4122 is located in the pneumatic path upstream of a pressure generator 4140.

(253) 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 or 3800.

(254) 8.4.1.3 Pressure Generator

(255) 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 cmH2O to about 20 cmH2O, or in other forms up to about 30 cmH2O 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. Pat. Nos. 7,866,944; 8,638,014; 8,636,479; and PCT Patent Application Publication No. WO 2013/020167.

(256) The pressure generator 4140 may be under the control of the therapy device controller.

(257) 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.

(258) 8.4.1.4 Transducer(s)

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

(260) In one form of the present technology, 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.

(261) In one form of the present technology, one or more transducers 4270 may be located proximate to the patient interface 3000 or 3800.

(262) In one form, a signal from a transducer 4270 may be filtered, such as by low-pass, high-pass or band-pass filtering.

(263) 8.4.1.5 Anti-Spill Back Valve

(264) In 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.

(265) 8.4.2 RPT Device Electrical Components

(266) 8.4.2.1 Power Supply

(267) A power supply 4210 may be located internal or external of the external housing 4010 of the RPT device 4000.

(268) 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.

(269) 8.4.2.2 Input Devices

(270) 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.

(271) 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.

(272) 8.5 Air Circuit

(273) 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 or 3800.

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

(275) In some forms, the air circuit 4170 may comprise one or more heating elements configured to heat air in the air circuit, for example to maintain or raise the temperature of the air. The heating element may be in a form of a heated wire circuit, and may comprise one or more transducers, such as temperature sensors. In one form, the heated wire circuit may be helically wound around the axis of the air circuit 4170. The heating element may be in communication with a controller such as a central controller. One example of an air circuit 4170 comprising a heated wire circuit is described in U.S. Pat. No. 8,733,349, which is incorporated herewithin in its entirety by reference.

(276) 8.5.1 Supplementary Gas Delivery

(277) In one form of the present technology, supplementary gas, e.g. oxygen, 4180 is delivered to one or more points in the pneumatic path, such as upstream of the pneumatic block 4020, to the air circuit 4170, and/or to the patient interface 3000 or 3800.

(278) 8.6 HUMIDIFIER 8.6.1 Humidifier overview

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

(280) The humidifier 5000 may comprise a humidifier reservoir 5110, a humidifier inlet 5002 to receive a flow of air, and a humidifier outlet 5004 to deliver a humidified flow of air. In some forms, as shown in FIG. 5A and FIG. 5B, an inlet and an outlet of the humidifier reservoir 5110 may be the humidifier inlet 5002 and the humidifier outlet 5004 respectively. The humidifier 5000 may further comprise a humidifier base 5006, which may be adapted to receive the humidifier reservoir 5110 and comprise a heating element 5240.

(281) 8.6.2 Humidifier Components

(282) 8.6.2.1 Water Reservoir

(283) According to one arrangement, the humidifier 5000 may comprise a water reservoir 5110 configured to hold, or retain, a volume of liquid (e.g. water) to be evaporated for humidification of the flow of air. The water reservoir 5110 may be configured to hold a predetermined maximum volume of water in order to provide adequate humidification for at least the duration of a respiratory therapy session, such as one evening of sleep. Typically, the reservoir 5110 is configured to hold several hundred millilitres of water, e.g. 300 millilitres (ml), 325 ml, 350 ml or 400 ml. In other forms, the humidifier 5000 may be configured to receive a supply of water from an external water source such as a building's water supply system.

(284) According to one aspect, the water reservoir 5110 is configured to add humidity to a flow of air from the RPT device 4000 as the flow of air travels therethrough. In one form, the water reservoir 5110 may be configured to encourage the flow of air to travel in a tortuous path through the reservoir 5110 while in contact with the volume of water therein.

(285) According to one form, the reservoir 5110 may be removable from the humidifier 5000, for example in a lateral direction as shown in FIG. 5A and FIG. 5B.

(286) The reservoir 5110 may also be configured to discourage egress of liquid therefrom, such as when the reservoir 5110 is displaced and/or rotated from its normal, working orientation, such as through any apertures and/or in between its sub-components. As the flow of air to be humidified by the humidifier 5000 is typically pressurised, the reservoir 5110 may also be configured to prevent losses in pneumatic pressure through leak and/or flow impedance.

(287) 8.6.2.2 Conductive Portion

(288) According to one arrangement, the reservoir 5110 comprises a conductive portion 5120 configured to allow efficient transfer of heat from the heating element 5240 to the volume of liquid in the reservoir 5110. In one form, the conductive portion 5120 may be arranged as a plate, although other shapes may also be suitable. All or a part of the conductive portion 5120 may be made of a thermally conductive material such as aluminium (e.g. approximately 2 mm thick, such as 1 mm, 1.5 mm, 2.5 mm or 3 mm), another heat conducting metal or some plastics. In some cases, suitable heat conductivity may be achieved with less conductive materials of suitable geometry.

(289) 8.6.2.3 Humidifier Reservoir Dock

(290) In one form, the humidifier 5000 may comprise a humidifier reservoir dock 5130 (as shown in FIG. 5B) configured to receive the humidifier reservoir 5110. In some arrangements, the humidifier reservoir dock 5130 may comprise a locking feature such as a locking lever 5135 configured to retain the reservoir 5110 in the humidifier reservoir dock 5130.

(291) 8.6.2.4 Water Level Indicator

(292) The humidifier reservoir 5110 may comprise a water level indicator 5150 as shown in FIG. 5A-5B. In some forms, the water level indicator 5150 may provide one or more indications to a user such as the patient 1000 or a care giver regarding a quantity of the volume of water in the humidifier reservoir 5110. The one or more indications provided by the water level indicator 5150 may include an indication of a maximum, predetermined volume of water, any portions thereof, such as 25%, 50% or 75% or volumes such as 200 ml, 300 ml or 400 ml.

(293) 8.6.2.5 Humidifier Transducer(s)

(294) The humidifier 5000 may comprise one or more humidifier transducers (sensors) instead of, or in addition to, transducers 4270 described above. Humidifier transducers may include one or more of an air pressure sensor, an air flow rate transducer, a temperature sensor, or a humidity sensor. A humidifier transducer may produce one or more output signals which may be communicated to a controller such as the central controller and/or the humidifier controller. In some forms, a humidifier transducer may be located externally to the humidifier 5000 (such as in the air circuit 4170) while communicating the output signal to the controller.

(295) 8.6.2.5.1 Pressure Transducer

(296) One or more pressure transducers may be provided to the humidifier 5000 in addition to, or instead of, a pressure sensor provided in the RPT device 4000.

(297) 8.6.2.5.2 Flow Rate Transducer

(298) One or more flow rate transducers may be provided to the humidifier 5000 in addition to, or instead of, a flow rate sensor provided in the RPT device 4000.

(299) 8.6.2.5.3 Temperature Transducer

(300) The humidifier 5000 may comprise one or more temperature transducers 5216. The one or more temperature transducers 5216 may be configured to measure one or more temperatures such as of the heating element 5240 and/or of the flow of air downstream of the humidifier outlet 5004. In some forms, the humidifier 5000 may further comprise a temperature sensor 5216 to detect the temperature of the ambient air.

(301) 8.6.2.5.4 Humidity Transducer

(302) In one form, the humidifier 5000 may comprise one or more humidity sensors 5218 to detect a humidity of a gas, such as the ambient air. The humidity sensor 5218 may be placed towards the humidifier outlet 5004 in some forms to measure a humidity of the gas delivered from the humidifier 5000. The humidity sensor may be an absolute humidity sensor or a relative humidity sensor.

(303) 8.6.2.6 Heating Element

(304) A heating element 5240 may be provided to the humidifier 5000 in some cases to provide a heat input to one or more of the volume of water in the humidifier reservoir 5110 and/or to the flow of air. The heating element 5240 may comprise a heat generating component such as an electrically resistive heating track. One suitable example of a heating element 5240 is a layered heating element such as one described in the PCT Patent Application Publication No. WO 2012/171072, which is incorporated herewith by reference in its entirety.

(305) In some forms, the heating element 5240 may be provided in the humidifier base 5006 where heat may be provided to the humidifier reservoir 5110 primarily by conduction as shown in FIG. 5B.

(306) 8.7 Breathing Waveforms

(307) FIG. 6A shows a model typical breath waveform of a person while sleeping. The horizontal axis is time, and the vertical axis is respiratory flow rate. While the parameter values may vary, a typical breath may have the following approximate values: tidal volume Vt 0.5 L, inhalation time Ti 1.6 s, peak inspiratory flow rate Qpeak 0.4 L/s, exhalation time Te 2.4 s, peak expiratory flow rate Qpeak ?0.5 L/s. The total duration of the breath, Ttot, is about 4 s. 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%.

(308) 8.8 Screening, Diagnosis, Monitoring Systems

(309) 8.8.1 Polysomnography

(310) FIG. 7A shows a patient 1000 undergoing polysomnography (PSG). A PSG system comprises a headbox 2000 which receives and records signals from the following sensors: an EOG electrode 2015; an EEG electrode 2020; an ECG electrode 2025; a submental EMG electrode 2030; a snore sensor 2035; a respiratory inductance plethysmogram (respiratory effort sensor) 2040 on a chest band; a respiratory inductance plethysmogram (respiratory effort sensor) 2045 on an abdominal band; an oro-nasal cannula 2050 with oral thermistor; a photoplethysmograph (pulse oximeter) 2055; and a body position sensor 2060. The electrical signals are referred to a ground electrode (ISOG) 2010 positioned in the centre of the forehead.

(311) 8.8.2 Non-Obtrusive Monitoring System

(312) One example of a monitoring apparatus 7100 for monitoring the respiration of a sleeping patient 1000 is illustrated in FIG. 7B. The monitoring apparatus 7100 contains a contactless motion sensor generally directed toward the patient 1000. The motion sensor is configured to generate one or more signals representing bodily movement of the patient 1000, from which may be obtained a signal representing respiratory movement of the patient.

(313) 8.9 Portable Oxygen Concentrator (POC)

(314) Portable oxygen concentrators may take advantage of pressure swing adsorption (PSA). Pressure swing adsorption may involve using one or more compressors to increase gas pressure inside a canister that contains particles of a gas separation adsorbent arranged in a sieve bed. As the pressure increases, certain molecules in the gas may become adsorbed onto the gas separation adsorbent. Removal of a portion of the gas in the canister under the pressurized conditions allows separation of the non-adsorbed molecules from the adsorbed molecules. The gas separation adsorbent may be regenerated by reducing the pressure, which reverses the adsorption of molecules from the adsorbent. Further details regarding oxygen concentrators may be found, for example, in U.S. Published Patent Application No. 2009-0065007, published Mar. 12, 2009, and entitled Oxygen Concentrator Apparatus and Method, which is incorporated herein by reference.

(315) Ambient air usually includes approximately 78% nitrogen and 21% oxygen with the balance comprised of argon, carbon dioxide, water vapor and other trace gases. If a gas mixture such as air, for example, is passed under pressure through a canister containing a gas separation adsorbent bed that attracts nitrogen more strongly than it does oxygen, part or all of the nitrogen will stay in the bed, and the gas coming out of the canister will be enriched in oxygen. When the bed reaches the end of its capacity to adsorb nitrogen, it can be regenerated by reducing the pressure, thereby releasing the adsorbed nitrogen. It is then ready for another cycle of producing oxygen enriched air. By alternating canisters in a two-canister system, one canister can be separating oxygen while the other canister is being purged (resulting in a continuous separation of the oxygen from the nitrogen). In this manner, oxygen enriched air can be accumulated, such as in a storage container or other pressurizable vessel or conduit coupled to the canisters, for a variety of uses including providing supplemental oxygen to patients.

(316) 8.10 Respiratory Therapy Modes

(317) Various respiratory therapy modes may be implemented by the disclosed respiratory therapy system. For example, the system may implement CPAP therapy, bi-level therapy, and/or high flow therapy.

(318) 8.11 Glossary

(319) For the purposes of the present technology disclosure, in certain forms of the present technology, one or more of the following definitions may apply. In other forms of the present technology, alternative definitions may apply.

(320) 8.11.1 General

(321) Air: In certain forms of the present technology, air may be taken to mean atmospheric air, and in other forms of the present technology air may be taken to mean some other combination of breathable gases, e.g. oxygen enriched air.

(322) Ambient: In certain forms of the present technology, the term ambient will be taken to mean (i) external of the treatment system or patient, and (ii) immediately surrounding the treatment system or patient.

(323) For example, ambient humidity with respect to a humidifier may be the humidity of air immediately surrounding the humidifier, e.g. the humidity in the room where a patient is sleeping. Such ambient humidity may be different to the humidity outside the room where a patient is sleeping.

(324) In another example, ambient pressure may be the pressure immediately surrounding or external to the body.

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

(326) Automatic Positive Airway Pressure (APAP) therapy: CPAP therapy in which the treatment pressure is automatically adjustable, e.g. from breath to breath, between minimum and maximum limits, depending on the presence or absence of indications of SDB events.

(327) Continuous Positive Airway Pressure (CPAP) therapy: Respiratory pressure therapy in which the treatment pressure is approximately constant through a respiratory cycle of a patient. In some forms, the pressure at the entrance to the airways will be slightly higher during exhalation, and slightly lower during inhalation. In some forms, the pressure will vary between different respiratory cycles of the patient, for example, being increased in response to detection of indications of partial upper airway obstruction, and decreased in the absence of indications of partial upper airway obstruction.

(328) Flow rate: The volume (or mass) of air delivered per unit time. Flow rate may refer to an instantaneous quantity. In some cases, a reference to flow rate will be a reference to a scalar quantity, namely a quantity having magnitude only. In other cases, a reference to flow rate will be a reference to a vector quantity, namely a quantity having both magnitude and direction. Flow rate may be given the symbol Q. Flow rate is sometimes shortened to simply flow or airflow.

(329) In the example of patient respiration, a flow rate may be nominally positive for the inspiratory portion of a breathing cycle of a patient, and hence negative for the expiratory portion of the breathing cycle of a patient. Device flow rate, Qd, is the flow rate of air leaving the RPT device. Total flow rate, Qt, is the flow rate of air and any supplementary gas reaching the patient interface via the air circuit. Vent flow rate, Qv, is the flow rate of air leaving a vent to allow washout of exhaled gases. Leak flow rate, Ql, is the flow rate of leak from a patient interface system or elsewhere. Respiratory flow rate, Qr, is the flow rate of air that is received into the patient's respiratory system.

(330) Flow therapy: Respiratory therapy comprising the delivery of a flow of air to an entrance to the airways at a controlled flow rate referred to as the treatment flow rate that is typically positive throughout the patient's breathing cycle.

(331) Humidifier: The word humidifier will be taken to mean a humidifying apparatus constructed and arranged, or configured with a physical structure to be capable of providing a therapeutically beneficial amount of water (H.sub.2O) vapour to a flow of air to ameliorate a medical respiratory condition of a patient.

(332) Leak: The word leak will be taken to be an unintended flow of air. In one example, leak may occur as the result of an incomplete seal between a mask and a patient's face. In another example leak may occur in a swivel elbow to the ambient.

(333) Noise, conducted (acoustic): Conducted noise in the present document refers to noise which is carried to the patient by the pneumatic path, such as the air circuit and the patient interface as well as the air therein. In one form, conducted noise may be quantified by measuring sound pressure levels at the end of an air circuit.

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

(335) Noise, vent (acoustic): Vent noise in the present document refers to noise which is generated by the flow of air through any vents such as vent holes of the patient interface.

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

(337) Medical Oxygen: Medical oxygen is defined as oxygen enriched air with an oxygen concentration of 80% or greater.

(338) Patient: A person, whether or not they are suffering from a respiratory condition.

(339) Pressure: Force per unit area. Pressure may be expressed in a range of units, including cmH.sub.2O, g-f/cm.sup.2 and hectopascal. 1 cmH.sub.2O is equal to 1 g-f/cm.sup.2 and is approximately 0.98 hectopascal (1 hectopascal=100 Pa=100 N/m.sup.2=1 millibar ?0.001 atm). In this specification, unless otherwise stated, pressure is given in units of cmH.sub.2O.

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

(341) Respiratory Pressure Therapy: The application of a supply of air to an entrance to the airways at a treatment pressure that is typically positive with respect to atmosphere.

(342) Ventilator: A mechanical device that provides pressure support to a patient to perform some or all of the work of breathing.

(343) 8.11.1.1 Materials

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

(345) Polycarbonate: a thermoplastic polymer of Bisphenol-A Carbonate.

(346) 8.11.1.2 Mechanical Properties

(347) Resilience: Ability of a material to absorb energy when deformed elastically and to release the energy upon unloading.

(348) Resilient: Will release substantially all of the energy when unloaded. Includes e.g. certain silicones, and thermoplastic elastomers.

(349) Hardness: The ability of a material per se to resist deformation (e.g. described by a Young's Modulus, or an indentation hardness scale measured on a standardised sample size). Soft materials may include silicone or thermo-plastic elastomer (TPE), and may, e.g. readily deform under finger pressure. Hard materials may include polycarbonate, polypropylene, steel or aluminium, and may not e.g. readily deform under finger pressure.

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

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

(352) Rigid structure or component: A structure or component that will not substantially change shape when subject to the loads typically encountered in use. An example of such a use may be setting up and maintaining a patient interface in sealing relationship with an entrance to a patient's airways, e.g. at a load of approximately 20 to 30 cmH2O pressure.

(353) As an example, an I-beam may comprise a different bending stiffness (resistance to a bending load) in a first direction in comparison to a second, orthogonal direction. In another example, a structure or component may be floppy in a first direction and rigid in a second direction.

(354) 8.11.2 Respiratory Cycle

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

(356) Breathing rate: The rate of spontaneous respiration of a patient, usually measured in breaths per minute.

(357) Duty cycle: The ratio of inhalation time, Ti to total breath time, Ttot.

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

(359) Expiratory portion of a breathing cycle: The period from the start of expiratory flow to the start of inspiratory flow.

(360) Flow limitation: Flow limitation will be taken to be the state of affairs in a patient's respiration where an increase in effort by the patient does not give rise to a corresponding increase in flow. Where flow limitation occurs during an inspiratory portion of the breathing cycle it may be described as inspiratory flow limitation. Where flow limitation occurs during an expiratory portion of the breathing cycle it may be described as expiratory flow limitation.

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

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

(363) Hyperpnea: An increase in flow to a level higher than normal.

(364) Inspiratory portion of a breathing cycle: The period from the start of inspiratory flow to the start of expiratory flow will be taken to be the inspiratory portion of a breathing cycle.

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

(366) Positive End-Expiratory Pressure (PEEP): The pressure above atmosphere in the lungs that exists at the end of expiration.

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

(368) Respiratory flow rate, patient airflow rate, respiratory airflow rate (Qr): These terms may be understood to refer to the RPT device's estimate of respiratory flow rate, as opposed to true respiratory flow rate or true respiratory flow rate, which is the actual respiratory flow rate experienced by the patient, usually expressed in litres per minute.

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

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

(371) Exhalation Time (Te): The duration of the expiratory portion of the respiratory flow rate waveform.

(372) Total Time (Ttot): The total duration between the start of one inspiratory portion of a respiratory flow rate waveform and the start of the following inspiratory portion of the respiratory flow rate waveform.

(373) Typical recent ventilation: The value of ventilation around which recent values of ventilation Vent over some predetermined timescale tend to cluster, that is, a measure of the central tendency of the recent values of ventilation.

(374) Upper airway obstruction (UAO): includes both partial and total upper airway obstruction. This may be associated with a state of flow limitation, in which the flow rate increases only slightly or may even decrease as the pressure difference across the upper airway increases (Starling resistor behaviour).

(375) Ventilation (Vent): A measure of a rate of gas being exchanged by the patient's respiratory system. Measures of ventilation may include one or both of inspiratory and expiratory flow, per unit time. When expressed as a volume per minute, this quantity is often referred to as minute ventilation. Minute ventilation is sometimes given simply as a volume, understood to be the volume per minute.

(376) 8.11.3 Ventilation

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

(378) Backup rate: A parameter of a ventilator that establishes the minimum breathing rate (typically in number of breaths per minute) that the ventilator will deliver to the patient, if not triggered by spontaneous respiratory effort.

(379) Cycled: The termination of a ventilator's inspiratory phase. When a ventilator delivers a breath to a spontaneously breathing patient, at the end of the inspiratory portion of the breathing cycle, the ventilator is said to be cycled to stop delivering the breath.

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

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

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

(383) Pressure support: A number that is indicative of the increase in pressure during ventilator inspiration over that during ventilator expiration, and generally means the difference in pressure between the maximum value during inspiration and the base pressure (e.g., PS=IPAP?EPAP). In some contexts, pressure support means the difference which the ventilator aims to achieve, rather than what it actually achieves.

(384) Servo-ventilator: A ventilator that measures patient ventilation, has a target ventilation, and which adjusts the level of pressure support to bring the patient ventilation towards the target ventilation.

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

(386) Swing: Equivalent term to pressure support.

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

(388) 8.11.4 Anatomy

(389) 8.11.4.1 Anatomy of the Face

(390) Ala: the external outer wall or wing of each nostril (plural: alar)

(391) Alare: The most lateral point on the nasal ala.

(392) Alar curvature (or alar crest) point: The most posterior point in the curved base line of each ala, found in the crease formed by the union of the ala with the cheek.

(393) Auricle: The whole external visible part of the ear.

(394) (nose) Bony framework: The bony framework of the nose comprises the nasal bones, the frontal process of the maxillae and the nasal part of the frontal bone.

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

(396) Columella: the strip of skin that separates the nares and which runs from the pronasale to the upper lip.

(397) Columella angle: The angle between the line drawn through the midpoint of the nostril aperture and a line drawn perpendicular to the Frankfort horizontal while intersecting subnasale.

(398) Frankfort horizontal plane: A line extending from the most inferior point of the orbital margin to the left tragion. The tragion is the deepest point in the notch superior to the tragus of the auricle.

(399) Glabella: Located on the soft tissue, the most prominent point in the midsagittal plane of the forehead.

(400) Lateral nasal cartilage: A generally triangular plate of cartilage. Its superior margin is attached to the nasal bone and frontal process of the maxilla, and its inferior margin is connected to the greater alar cartilage.

(401) Greater alar cartilage: A plate of cartilage lying below the lateral nasal cartilage. It is curved around the anterior part of the naris. Its posterior end is connected to the frontal process of the maxilla by a tough fibrous membrane containing three or four minor cartilages of the ala.

(402) Nares (Nostrils): Approximately ellipsoidal apertures forming the entrance to the nasal cavity. The singular form of nares is naris (nostril). The nares are separated by the nasal septum.

(403) Naso-labial sulcus or Naso-labial fold: The skin fold or groove that runs from each side of the nose to the corners of the mouth, separating the cheeks from the upper lip.

(404) Naso-labial angle: The angle between the columella and the upper lip, while intersecting subnasale.

(405) Otobasion inferior: The lowest point of attachment of the auricle to the skin of the face.

(406) Otobasion superior: The highest point of attachment of the auricle to the skin of the face.

(407) Pronasale: the most protruded point or tip of the nose, which can be identified in lateral view of the rest of the portion of the head.

(408) Philtrum: the midline groove that runs from lower border of the nasal septum to the top of the lip in the upper lip region.

(409) Pogonion: Located on the soft tissue, the most anterior midpoint of the chin.

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

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

(412) Sellion: Located on the soft tissue, the most concave point overlying the area of the frontonasal suture.

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

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

(415) Subnasal point: Located on the soft tissue, the point at which the columella merges with the upper lip in the midsagittal plane.

(416) Supramenton: The point of greatest concavity in the midline of the lower lip between labrale inferius and soft tissue pogonion

(417) Anatomy of the Skull

(418) Frontal bone: The frontal bone includes a large vertical portion, the squama frontalis, corresponding to the region known as the forehead.

(419) Mandible: The mandible forms the lower jaw. The mental protuberance is the bony protuberance of the jaw that forms the chin.

(420) Maxilla: The maxilla forms the upper jaw and is located above the mandible and below the orbits. The frontal process of the maxilla projects upwards by the side of the nose, and forms part of its lateral boundary.

(421) Nasal bones: The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, the bridge of the nose.

(422) Nasion: The intersection of the frontal bone and the two nasal bones, a depressed area directly between the eyes and superior to the bridge of the nose.

(423) Occipital bone: The occipital bone is situated at the back and lower part of the cranium. It includes an oval aperture, the foramen magnum, through which the cranial cavity communicates with the vertebral canal. The curved plate behind the foramen magnum is the squama occipitalis.

(424) Orbit: The bony cavity in the skull to contain the eyeball.

(425) Parietal bones: The parietal bones are the bones that, when joined together, form the roof and sides of the cranium.

(426) Temporal bones: The temporal bones are situated on the bases and sides of the skull, and support that part of the face known as the temple.

(427) Zygomatic bones: The face includes two zygomatic bones, located in the upper and lateral parts of the face and forming the prominence of the cheek.

(428) 8.11.4.2 Anatomy of the Respiratory System

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

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

(431) Lungs: The organs of respiration in humans. The conducting zone of the lungs contains the trachea, the bronchi, the bronchioles, and the terminal bronchioles. The respiratory zone contains the respiratory bronchioles, the alveolar ducts, and the alveoli.

(432) Nasal cavity: The nasal cavity (or nasal fossa) is a large air filled space above and behind the nose in the middle of the face. The nasal cavity is divided in two by a vertical fin called the nasal septum. On the sides of the nasal cavity are three horizontal outgrowths called nasal conchae (singular concha) or turbinates. To the front of the nasal cavity is the nose, while the back blends, via the choanae, into the nasopharynx.

(433) Pharynx: The part of the throat situated immediately inferior to (below) the nasal cavity, and superior to the oesophagus and larynx. The pharynx is conventionally divided into three sections: the nasopharynx (epipharynx) (the nasal part of the pharynx), the oropharynx (mesopharynx) (the oral part of the pharynx), and the laryngopharynx (hypopharynx).

(434) 8.11.5 Patient Interface

(435) Anti-asphyxia valve (AAV): The component or sub-assembly of a mask system that, by opening to atmosphere in a failsafe manner, reduces the risk of excessive CO2 rebreathing by a patient.

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

(437) Frame: Frame will be taken to mean a mask structure that bears the load of tension between two or more points of connection with a headgear. A mask frame may be a non-airtight load bearing structure in the mask. However, some forms of mask frame may also be air-tight.

(438) Functional dead space: (description to be inserted here)

(439) Headgear: Headgear will be taken to mean a form of positioning and stabilizing structure designed for use on a head. For example the headgear may comprise a collection of one or more struts, ties and stiffeners configured to locate and retain a patient interface in position on a patient's face for delivery of respiratory therapy. Some ties are formed of a soft, flexible, elastic material such as a laminated composite of foam and fabric.

(440) Membrane: Membrane will be taken to mean a typically thin element that has, preferably, substantially no resistance to bending, but has resistance to being stretched.

(441) Plenum chamber: a mask plenum chamber will be taken to mean a portion of a patient interface having walls at least partially enclosing a volume of space, the volume having air therein pressurised above atmospheric pressure in use. A shell may form part of the walls of a mask plenum chamber.

(442) Seal: May be a noun form (a seal) which refers to a structure, or a verb form (to seal) which refers to the effect. Two elements may be constructed and/or arranged to seal or to effect sealing therebetween without requiring a separate seal element per se.

(443) Shell: A shell will be taken to mean a curved, relatively thin structure having bending, tensile and compressive stiffness. For example, a curved structural wall of a mask may be a shell. In some forms, a shell may be faceted. In some forms a shell may be airtight. In some forms a shell may not be airtight.

(444) Stiffener: A stiffener will be taken to mean a structural component designed to increase the bending resistance of another component in at least one direction.

(445) Strut: A strut will be taken to be a structural component designed to increase the compression resistance of another component in at least one direction.

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

(447) Tie (noun): A structure designed to resist tension.

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

(449) 8.11.6 Shape of Structures

(450) Products in accordance with the present technology may comprise one or more three-dimensional mechanical structures, for example a mask cushion or an impeller. The three-dimensional structures may be bounded by two-dimensional surfaces. These surfaces may be distinguished using a label to describe an associated surface orientation, location, function, or some other characteristic. For example a structure may comprise one or more of an anterior surface, a posterior surface, an interior surface and an exterior surface. In another example, a seal-forming structure may comprise a face-contacting (e.g. outer) surface, and a separate non-face-contacting (e.g. underside or inner) surface. In another example, a structure may comprise a first surface and a second surface.

(451) To facilitate describing the shape of the three-dimensional structures and the surfaces, we first consider a cross-section through a surface of the structure at a point, p. See FIG. 3B to FIG. 3F, which illustrate examples of cross-sections at point p on a surface, and the resulting plane curves. FIGS. 3B to 3F also illustrate an outward normal vector at p. The outward normal vector at p points away from the surface. In some examples we describe the surface from the point of view of an imaginary small person standing upright on the surface.

(452) 8.11.6.1 Curvature in One Dimension

(453) The curvature of a plane curve at p may be described as having a sign (e.g. positive, negative) and a magnitude (e.g. 1/radius of a circle that just touches the curve at p).

(454) Positive curvature: If the curve at p turns towards the outward normal, the curvature at that point will be taken to be positive (if the imaginary small person leaves the point p they must walk uphill). See FIG. 3B (relatively large positive curvature compared to FIG. 3C) and FIG. 3C (relatively small positive curvature compared to FIG. 3B). Such curves are often referred to as concave.

(455) Zero curvature: If the curve at p is a straight line, the curvature will be taken to be zero (if the imaginary small person leaves the point p, they can walk on a level, neither up nor down). See FIG. 3D.

(456) Negative curvature: If the curve at p turns away from the outward normal, the curvature in that direction at that point will be taken to be negative (if the imaginary small person leaves the point p they must walk downhill). See FIG. 3E (relatively small negative curvature compared to FIG. 3F) and FIG. 3F (relatively large negative curvature compared to FIG. 3E). Such curves are often referred to as convex.

(457) 8.11.6.2 Curvature of Two Dimensional Surfaces

(458) A description of the shape at a given point on a two-dimensional surface in accordance with the present technology may include multiple normal cross-sections. The multiple cross-sections may cut the surface in a plane that includes the outward normal (a normal plane), and each cross-section may be taken in a different direction. Each cross-section results in a plane curve with a corresponding curvature. The different curvatures at that point may have the same sign, or a different sign. Each of the curvatures at that point has a magnitude, e.g. relatively small. The plane curves in FIGS. 3B to 3F could be examples of such multiple cross-sections at a particular point.

(459) Principal curvatures and directions: The directions of the normal planes where the curvature of the curve takes its maximum and minimum values are called the principal directions. In the examples of FIG. 3B to FIG. 3F, the maximum curvature occurs in FIG. 3B, and the minimum occurs in FIG. 3F, hence FIG. 3B and FIG. 3F are cross sections in the principal directions. The principal curvatures at p are the curvatures in the principal directions.

(460) Region of a surface: A connected set of points on a surface. The set of points in a region may have similar characteristics, e.g. curvatures or signs.

(461) Saddle region: A region where at each point, the principal curvatures have opposite signs, that is, one is positive, and the other is negative (depending on the direction to which the imaginary person turns, they may walk uphill or downhill).

(462) Dome region: A region where at each point the principal curvatures have the same sign, e.g. both positive (a concave dome) or both negative (a convex dome).

(463) Cylindrical region: A region where one principal curvature is zero (or, for example, zero within manufacturing tolerances) and the other principal curvature is non-zero.

(464) Planar region: A region of a surface where both of the principal curvatures are zero (or, for example, zero within manufacturing tolerances).

(465) Edge of a surface: A boundary or limit of a surface or region.

(466) Path: In certain forms of the present technology, path will be taken to mean a path in the mathematicaltopological sense, e.g. a continuous space curve from f(0) to f(1) on a surface. In certain forms of the present technology, a path may be described as a route or course, including e.g. a set of points on a surface. (The path for the imaginary person is where they walk on the surface, and is analogous to a garden path).

(467) Path length: In certain forms of the present technology, path length will be taken to mean the distance along the surface from f(0) to f(1), that is, the distance along the path on the surface. There may be more than one path between two points on a surface and such paths may have different path lengths. (The path length for the imaginary person would be the distance they have to walk on the surface along the path).

(468) Straight-line distance: The straight-line distance is the distance between two points on a surface, but without regard to the surface. On planar regions, there would be a path on the surface having the same path length as the straight-line distance between two points on the surface. On non-planar surfaces, there may be no paths having the same path length as the straight-line distance between two points. (For the imaginary person, the straight-line distance would correspond to the distance as the crow flies.)

(469) 8.11.6.3 Space Curves

(470) Space curves: Unlike a plane curve, a space curve does not necessarily lie in any particular plane. A space curve may be closed, that is, having no endpoints. A space curve may be considered to be a one-dimensional piece of three-dimensional space. An imaginary person walking on a strand of the DNA helix walks along a space curve. A typical human left ear comprises a helix, which is a left-hand helix, see FIG. 3Q. A typical human right ear comprises a helix, which is a right-hand helix, see FIG. 3R. FIG. 3S shows a right-hand helix. The edge of a structure, e.g. the edge of a membrane or impeller, may follow a space curve. In general, a space curve may be described by a curvature and a torsion at each point on the space curve. Torsion is a measure of how the curve turns out of a plane. Torsion has a sign and a magnitude. The torsion at a point on a space curve may be characterised with reference to the tangent, normal and binormal vectors at that point.

(471) Tangent unit vector (or unit tangent vector): For each point on a curve, a vector at the point specifies a direction from that point, as well as a magnitude. A tangent unit vector is a unit vector pointing in the same direction as the curve at that point. If an imaginary person were flying along the curve and fell off her vehicle at a particular point, the direction of the tangent vector is the direction she would be travelling.

(472) Unit normal vector: As the imaginary person moves along the curve, this tangent vector itself changes. The unit vector pointing in the same direction that the tangent vector is changing is called the unit principal normal vector. It is perpendicular to the tangent vector.

(473) Binormal unit vector: The binormal unit vector is perpendicular to both the tangent vector and the principal normal vector. Its direction may be determined by a right-hand rule (see e.g. FIG. 3P), or alternatively by a left-hand rule (FIG. 3O).

(474) Osculating plane: The plane containing the unit tangent vector and the unit principal normal vector. See FIGS. 3O and 3P.

(475) Torsion of a space curve: The torsion at a point of a space curve is the magnitude of the rate of change of the binormal unit vector at that point. It measures how much the curve deviates from the osculating plane. A space curve which lies in a plane has zero torsion. A space curve which deviates a relatively small amount from the osculating plane will have a relatively small magnitude of torsion (e.g. a gently sloping helical path). A space curve which deviates a relatively large amount from the osculating plane will have a relatively large magnitude of torsion (e.g. a steeply sloping helical path). With reference to FIG. 3S, since T2>T1, the magnitude of the torsion near the top coils of the helix of FIG. 3S is greater than the magnitude of the torsion of the bottom coils of the helix of FIG. 3S

(476) With reference to the right-hand rule of FIG. 3P, a space curve turning towards the direction of the right-hand binormal may be considered as having a right-hand positive torsion (e.g. a right-hand helix as shown in FIG. 3S). A space curve turning away from the direction of the right-hand binormal may be considered as having a right-hand negative torsion (e.g. a left-hand helix).

(477) Equivalently, and with reference to a left-hand rule (see FIG. 3O), a space curve turning towards the direction of the left-hand binormal may be considered as having a left-hand positive torsion (e.g. a left-hand helix). Hence left-hand positive is equivalent to right-hand negative. See FIG. 3T.

(478) 8.11.6.4 Holes

(479) A surface may have a one-dimensional hole, e.g. a hole bounded by a plane curve or by a space curve. Thin structures (e.g. a membrane) with a hole, may be described as having a one-dimensional hole. See for example the one dimensional hole in the surface of structure shown in FIG. 3I, bounded by a plane curve.

(480) A structure may have a two-dimensional hole, e.g. a hole bounded by a surface. For example, an inflatable tyre has a two dimensional hole bounded by the interior surface of the tyre. In another example, a bladder with a cavity for air or gel could have a two-dimensional hole. See for example the cushion of FIG. 3L and the example cross-sections therethrough in FIG. 3M and FIG. 3N, with the interior surface bounding a two dimensional hole indicated. In a yet another example, a conduit may comprise a one-dimension hole (e.g. at its entrance or at its exit), and a two-dimension hole bounded by the inside surface of the conduit. See also the two dimensional hole through the structure shown in FIG. 3K, bounded by a surface as shown.

(481) 8.12 Other Remarks

(482) 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.

(483) 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.

(484) 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.

(485) 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.

(486) 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.

(487) 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.

(488) 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.

(489) 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.

(490) 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.

(491) 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 be modified and/or aspects thereof may be conducted concurrently or even synchronously.

(492) 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.

(493) TABLE-US-00004 8.13 REFERENCE SIGNS LIST moisture exchanger 800 first planar surface 802 second planar surface 804 sidewall 806 vent 808 angle 812 flow 814 flow 816 exit 818 moisture exchanger 840 first planar surface 842 second planar surface 844 sidewall 846 opening 847 vent 848 pathway 849 flow 852 flow 854 flow 856 exit flow 858 attachment means 900 filter layer 910 attachment means 940 outer body 942 opposing ends 944 tabs 946 patient 1000 bed partner 1100 headbox 2000 ground electrode ISOG 2010 EOG electrode 2015 EEG electrode 2020 ECG electrode 2025 submental EMG electrode 2030 snore sensor 2035 respiratory inductance plethysmogram respiratory effort sensor 2040 respiratory inductance plethysmogram respiratory effort sensor 2045 oro - nasal cannula 2050 photoplethysmograph pulse oximeter 2055 body position sensor 2060 patient interface 3000 seal - forming structure 3100 plenum chamber 3200 chord 3210 superior point 3220 inferior point 3230 structure 3300 vent 3400 connection port 3600 forehead support 3700 ISO 3744 unsealed patient interface 3800 nasal prong 3810a nasal prong 3810b lumen 3820a lumen 3820b RPT device 4000 external housing 4010 upper portion 4012 portion 4014 panel 4015 chassis 4016 handle 4018 pneumatic block 4020 air filter 4110 air filters 4110 inlet air filter 4112 outlet air filter 4114 muffler 4120 inlet muffler 4122 outlet muffler 4124 pressure generator 4140 blower 4142 controllable blower 4142 motor 4144 brushless DC motor 4144 anti - spill back valve 4160 air circuit 4170 power supply 4210 input device 4220 transducer 4270 pressure sensors 4272 flow rate sensors 4274 algorithms 4300 humidifier 5000 humidifier inlet 5002 humidifier outlet 5004 humidifier base 5006 reservoir 5110 conductive portion 5120 humidifier reservoir dock 5130 locking lever 5135 water level indicator 5150 temperature sensor 5216 humidity sensor 5218 heating element 5240 patient interface 6000 plenum chamber 6200 monitoring apparatus 7100