Filter for a patient interface

Abstract

A filter configured for use with a patient interface for providing positive pressure respiratory therapy to a patient is disclosed. The filter comprises a filter body. The filter body comprises a filter inlet, a filter outlet and a sealed passageway between the filter inlet and the filter outlet. The filter further comprises a filter element in fluid communication with the filter outlet and a sealing element surrounding the filter inlet. The sealing element is configured to form a seal surrounding the outlet of a patient interface when the filter is coupled to a patient interface. The filter inlet is configured to receive gases from an outlet of a patient interface to allow the gases to flow through the sealed passageway to the filter outlet.

Description

FILTER FOR A PATIENT INTERFACETECHNICAL FIELD

[0001] The present invention relates to the field of non-invasive ventilation (NIV) for respiratory support. It relates particularly to a patient interface for NIV. More particularly, the invention relates to a filter for a patient interface for delivering NIV respiratory therapy to a patient.BACKGROUND

[0002] Non-invasive ventilation (NIV) is a form of respiratory therapy for treatment of respiratory diseases, such as thoracic restrictive diseases, acute respiratory failure, advanced neuromuscular diseases, chronic obstructive pulmonary disease (COPD - which includes emphysema, refractory asthma and chronic bronchitis). NIV may also be a form of respiratory support for a patient.

[0003] NIV therapy or NIV support provides a positive airway pressure and flow to the airways of a patient to aid or supplement respiration of a patient, respectively.

[0004] Patients receive NIV therapy or NIV support via a patient interface. In some applications, the patient interface is secured firmly to the patient’s face to achieve a seal sufficient to minimize leakages. In such a system, the patient receives positive pressure and flow. The patient undergoes many breathing cycles, where one cycle consists of inhalation and exhalation through the patient interface.

[0005] In some NIV applications, the exhaled gases may exit the NIV system through the patient interface to the surroundings. In some applications, the exhaled gases may exit the patient and re-enter the NIV system through the patient interface. These exhaled gases may contain air with higher concentration of carbon dioxide as well as other particulates, some harmful for the patient and for people around the patient.

[0006] There exists a need to reduce concentrations of particulates that may be harmful from gases exhaled by a patient on its exit or after it exits a patient interface. Particulates may be, but are not limited to, disease causing bacteria, virus and moisture.SUMMARY OF DISCLOSURE

[0007] The present invention will now be described by way of a set of embodiments. However, it will be appreciated that the invention may be defined by combining the features of two or more of the embodiments.

[0008] In a first aspect, a filter configured for use with a patient interface, for providing positive pressure respiratory therapy to a patient, comprises: a filter body comprising a filter inlet, a filter outlet and a sealed passageway between the filter inlet and the filter outlet, a filter element in fluid communication with the filter outlet, a sealing element surrounding the filter inlet, wherein the sealing element is configured to form a seal surrounding the outlet of a patient interface when the filter is coupled to a patient interface, and wherein the filter inlet is configured to receive gases from an outlet of a patient interface to allow the gases flow through the sealed passageway to the filter outlet

[0009] In a second aspect, a system comprises a filter and a patient interface, wherein the patient interface comprising a cushion module and a frame configured to couple with the cushion module, the cushion module further comprising a seal configured to form a seal with a patient’s face surrounding an entrance to a nose and / or mouth of a user and a housing comprising the outlet, and wherein the coupling mechanism of the filter is configured to couple with the frame of the patient interface, such that when the frame is coupled to the cushion module the filter is located in abutment with the housing and such that the sealing element of the filter forms a seal with the housing surrounding the outlet.

[0010] In a third aspect, a filter configured for use with a patient interface, for providing positive pressure respiratory therapy to a patient, comprises: a filter body comprising a filter inlet, a filter outlet, and a sealed passageway; a filter element in fluid communication with the filter outlet; wherein the filter inlet is configured to receive gases from an outlet of the patient interface and to convey the gases flow through the sealed passageway to the filter outlet and wherein the filter element is in fluid communication with the filter outlet such that substantially all gas exiting the filter outlet flows through the filter element to external of the filter; and wherein an opening area of the filter inlet is smaller than an opening area of the filter outlet.

[0011] In a fourth aspect, an assembly comprises a filter and a patient interface, wherein the patient interface comprises a cushion module and a frame configured to couple with the cushion module, the cushion module comprising a seal configured to form a seal with a patient’s face surrounding an entrance to a nose and / or mouth of a user, and a housing comprising the outlet; and wherein the coupling mechanism of the filter is configured to couple with the frame of the patient interface such that when the frame is coupled to the cushion module the filter is held against the housing by its connection with the frame and the sealing element of the filter forms a seal with the housing at least partially surrounding the outlet.

[0012] In a fifth aspect, a patient interface assembly for providing positive pressure respiratory therapy to a patient comprises: a cushion module comprising a seal and a housing which together define a cavity for receiving pressurised gasses; the housing comprising a gas inlet configured to receive supply of pressurised gasses and a gas outlet configured to exhaust gasses from within the cavity; the seal comprising a seal opening configured to seal with the mouth and / or nose of a patient to deliver pressurised gasses from within the cavity to the patient; a frame coupled to the cushion module; and a filter for coupling with the frame and engaging with a portion of the housing when the frame is removably coupled to the cushion module; the filter comprising a filter body, a filter inlet, a filter outlet, and a sealed passageway formed between the filter inlet and the filter outlet; a filter element positioned adjacent to or near the filter outlet; wherein the filter inlet is configured to receive gases from the gas outlet and wherein the filter element is in fluid communication with the filter outlet such that substantially all gas exiting the filter outlet flows through the filter element to atmosphere, and the filter further comprising a sealing element surrounding the filter inlet, the sealing element configured to form a seal surrounding the outlet of the cushion module when the filter is coupled with the frame.

[0013] The opening area of the filter inlet may be smaller than an opening area of the filter outlet.

[0014] The ratio between the opening area of the filter inlet and the opening area of the filter outlet may between 0.1 :1 to 0.5:1.

[0015] The filter inlet opening may be an elongate shaped opening or may be a substantially oval shaped opening.

[0016] The distance from the filter inlet to the filter outlet taken through the passageway may be between 1 mm to 15 mm.

[0017] The distance from the filter inlet to the filter outlet taken through the passageway may greater than 7 mm.

[0018] The sealed passageway of the filter body may undergo a change in geometry such that gases entering the filter inlet decrease in pressure before passing through the filter outlet and the filter element.

[0019] The change in geometry may comprise a change in cross-sectional area of the sealed passageway having regard to a cross-section perpendicular to a direction of gas flow through the sealed passageway.

[0020] The filter body may be substantially curved in a top-down view to follow the curvature of the patient interface.

[0021] The filter body may comprise a protruding lip surrounding the filter inlet.

[0022] The protruding lip may comprise a varying width in a plane of the rear surface of the filter around a perimeter of the protruding lip.

[0023] The varying width of the protruding lip projecting from a rear surface of the filter may be greater than 1mm.

[0024] The varying width of the protruding lip projecting from a rear surface of the filter may be less than 5mm.

[0025] The varying width of the protruding lip projecting from a rear surface of the filter may not greater than about 2mm.

[0026] The sealing element may affixed to the protruding lip.

[0027] The filter element may comprise a filter media.

[0028] The filter media may comprise a polypropylene and / or an acrylic material.

[0029] In some embodiments, the filter element further comprises a filter frame.

[0030] The filter frame may be over-moulded to at least a portion of the perimeter of the filter media.

[0031] The filter may comprise a cover configured to extend across a surface of the filter media.

[0032] The cover may be removably couplable to the filter frame.

[0033] The cover may be integrally formed with the filter frame.

[0034] The cover may comprise a plurality of openings.

[0035] The plurality of openings may be arranged in a lattice formation.

[0036] The filter may comprise a coupling mechanism configured to removably couple the filter to the patient interface.

[0037] The coupling mechanism may comprise at least one arm configured to removably couple with the patient interface.

[0038] The at least one arm may be connected to the filter body.

[0039] The at least one arm may comprise a first arm and a second arm and wherein the first arm may be connected at a first side of the filter body via a first connection and the second arm may be connected at a second side of the filter body via a second connection.

[0040] The first arm and the second arm may be formed as a unitary structure of the filter body.

[0041] The first connection may be a first hinge and the second connection may be a second hinge.

[0042] The first hinge may be located substantially midway along the first arm and the second hinge may be located substantially midway along the second arm.

[0043] The first hinge may be located at a distal end of the first arm and the second hinge may be located at a distal end of the second arm.

[0044] There may be a preformed angle between each of the filter body and the first arm, and the filter body and the second arm.

[0045] The preformed angle may be between about 5° and 135°.

[0046] The first arm and the second arm may each comprises a finger grip.

[0047] The finger grip may comprise a roughened surface and / or protrusions.

[0048] The filter body may comprise a first stop configured to make contact with the first arm and a second stop configure to make contact with the second arm, the first stop and the second stop may be configured to limit movement of the first arm and the second arm respectively.

[0049] The filter may comprise a recess configured to provide clearance for an inlet elbow of the patient interface.

[0050] The first arm of the coupling mechanism may comprise first protrusion, the second arm of the coupling mechanism may comprise a second protrusion, the frame may comprises a first aperture and a second aperture, and wherein the first protrusion and the second protrusion may be configured to engage the first aperture and the second aperture respectively to couple the filter to the frame.

[0051] The first arm of the coupling mechanism may comprise a first aperture, the second arm of the coupling mechanism may comprise a second aperture, the frame may comprise a first protrusion and a second protrusion, and wherein the first protrusion and second protrusion may be configured to engage the first aperture and the second aperture respectively to couple the filter to the frame.

[0052] The filter may comprise a sealing element surrounding the filter inlet, the sealing element may be configured to form a seal surrounding the outlet of the patient interface when the filter is coupled with the patient interface.

[0053] Although various features are disclosed above in relation to one or more aspects, it will be appreciated that one or more features of one aspect may be combined with other aspects to arrive at additional embodiments. It follows that disclosure of features in the preceding statements should not be interpreted as meaning that the features are limited in application to the aspects in respect of which they are disclosed.

[0054] Ordinal references (e.g. first, second, third) to aspects disclosed above serve to differentiate aspects from one another only. The ordinal references are not to be interpreted as the order of importance of the aspects.BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The aspects of the patient interface disclosed above are described in detail below by reference to embodiments, which serve as examples only, and with reference to the accompanying drawings, in which:

[0056] Figure 1 is an oblique view from the front and above of an assembly comprising a filter shown in Figure 2 and a patient interface.

[0057] Figure 2 is a side view of an embodiment of a filter according to the first aspect.

[0058] Figure 3 is a cross-sectional view of the filter of Figure 1 along the line A-A in Figure 2.

[0059] Figure 4 is a rear view of the filter of Figure 1 .

[0060] Figure 5 is a top view of the filter of Figure 1 .

[0061] Figure 6 is a oblique exploded view of the filter of Figure 1 .

[0062] Figure 7 is an oblique view from the front and above of another embodiment of a filter with a cover.

[0063] Figure 8 is an oblique rear view of the filter of Figure 7.

[0064] Figure 9 is an oblique exploded view of the assembly of Figure 2.

[0065] Figure 10 is a top view of the assembly of Figure 1 .

[0066] Figure 11 is an oblique front view of the patient interface in the assembly of Figure 1 .

[0067] Figure 12 is a rear view of the patient interface of Figure 11 .

[0068] Figure 13 is a front view of the patient interface of Figure 11 .

[0069] Figure 14 is a cross-sectional view of the patient interface of Figure 12 along the line B-B.

[0070] Figure 15 is a top view of the patient interface of Figure 11 .

[0071] Figure 16 is an exploded view of the patient interface in Figure 11.

[0072] Figure 17 is a rear view of a housing of the patient interface of Figure 11 .

[0073] Figure 18 is a front view of a frame of the patient interface of Figure 11 .

[0074] Figure 19 is an oblique view of another embodiment of a filter.

[0075] Figure 20 is a top view of the filter in Figure 1 with stops.

[0076] Figure 21 is an oblique front view from above of another embodiment of a filter.

[0077] Figure 22 is a top view of the filter in Figure 21.

[0078] Figure 23 is a rear view of the filter in Figure 21 .

[0079] Figure 24 is an oblique rear view from below of the filter in Figure 21 .DESCRIPTION OF EMBODIMENTS

[0080] Embodiments of the aspects disclosed above will now be described in the following text which includes reference numerals that correspond to features illustrated in the accompanying figures. Where possible, related reference numerals have been used to identify the same or substantially similar features in the different embodiments. To maintain clarity of the figures, however, all reference numerals are not included in each figure.

[0081] The aspects of the patient interface disclosed above will be described in detail below by reference to embodiments of a patient interface in the general form shown in Figures 1 to 6. The embodiments described following this are variations on that general form. However, it will be appreciated that the scope of the aspects should not be limited by reference to that general form or to the specific embodiments described below, and, instead, the aspects should be interpreted as relating as well to other forms of patient interfaces that also deliver pressurised respiratory gas to a patient, including full face patient interfaces that do not contact the bridge of the nose (over the nose oro-nasal masks), total-face masks, helmet interfaces, and where suitable, nasal masks that seal with the patients nasal cavity.

[0082] The term “respiratory gas” or “respiratory gasses” as used throughout this specification is taken to mean a gas used in human respiration or human ventilation. The term “inhaled respiratory gas” as used throughout this specification is taken to mean respiratory gas that is inhaled during the inhalation phase of the breathing cycle. The term includes within its scope ambient air or air that isconditioned for treating a patient, such as having elevated humidity or oxygen levels, or both compared to ambient air. The term “exhaled respiratory gas” as used throughout this specification is taken to mean respiratory gas that is exhaled from the lungs and airways of a patient during the exhalation phase of the breathing cycle. It, therefore, includes respiratory gas from the lungs and gas which occupies the anatomical dead space of the patient at the end of the exhalation phase of the breathing cycle.Patient interface

[0083] With reference to Figure 1 , an embodiment of filter 800 is shown assembled with a patient interface 10. The filter 800 is shown in Figures 2 to 8 and the patient interface 10 is shown in Figures 9 to 18. The patient interface 10 of this embodiment is a sub-nasal full-face mask. The patient interface 10 comprises a cushion module 20, frame 30 and a conduit connector 40.

[0084] The cushion module 20 comprises a seal 218 and a housing 202. The seal 218 is formed of a soft and resilient material such that it can sustain a preformed shape. The seal 218 may be made of an elastomer for example, silicone.

[0085] The seal member 218 includes an oral opening 220. The oral opening 220 is configured to circumscribe a patient’s mouth when fitted to the patient. A patientcontact surface 290 forms a seal about the mouth. Respiratory gases at elevated pressure can be delivered to the patient via the oral opening 220.

[0086] The seal 218 comprises a nare opening 222. The nare opening 222 is located at the nare-sealing portion 224. The nare-sealing portion 224 is a nasal saddle. The nasal saddle shape is configured to receive and closely follow the curvature of an under-side of a nose of a patient. The nare-sealing portion 224 is configured to form a seal with the under-side of the nose of the patient. Respiratory gases at elevated pressure can be delivered to the patient via the nare opening 222.

[0087] The patient-contact surface 290 includes the nare-sealing portion 224 and a lip superior wall portion 268 located between the oral opening 220 and the nare opening 222. The lip superior wall portion 268 is the region between the oral opening 220, the nare opening 222 and the lateral sides of the nare opening 222.

[0088] The seal 218 is attached to a housing 202. The housing 202 is more rigid than the seal 218 such that housing 202 provides structural support for the seal 218. The housing may be constructed from a rigid material for example, a polymer. The housing has provision to accept a conduit connector 40.

[0089] The housing 202 includes a sleeve 212 that is sized and shaped to connect with the frame 30. The sleeve 212 forms an inlet opening 292 through which respiratory gas can be fluidly communicated from the conduit connector 40 to interior of the cushion module 20. The sleeve 212 includes key formations 214 that interact with the frame 30 to ensure correct alignment of the frame 30 with the housing 202 when assembled.

[0090] The housing 202 includes a series of tabs 204 which project outwardly around its perimeter. The outer ends of the tabs 204 are linked to a bead 206 which runs continuously across all of the tabs 204, thereby forming a series of discrete outer over-mould windows 208 between the tabs 204 and the bead 206. The seal member 218 is integrally formed with the housing by over-moulding a resilient material onto the housing 202 to fill the outer over-mould of windows 208.Therefore, the tabs 204 and the bead 206 become embedded in the resilient material and are mechanically interlocked with the seal member 218. The seal member 218 and the housing 202, therefore, form a unitary cushion module 20 structure.

[0091] The cushion module 20 defines an interior volume which comprises a first chamber 226 and a second chamber 228. The second chamber 228 is located in an upper portion of the internal volume of the seal 218. The first chamber 226 comprises the lower portion of the internal volume of the cushion module 20. The first chamber 226 and second chamber 228 are separated by a dividing wall 230. The oral opening 220 is associated with the first chamber 226 to enable transfer of respiratory gas between the first chamber 226 and the patient’s mouth. The inlet opening 292 of the sleeve 212 is also associated with the first chamber 226. The nare opening 222 is associated with the second chamber 228 to enable transfer of respiratory gas between a second chamber 228 and the patient’s nares.

[0092] The second chamber 228 includes an outlet 216. The outlet 216 delivers respiratory gas from the second chamber 228 to external to the patient interface 10.In the cushion module 20, the outlet 216 is a vent portion. The vent portion may comprise bias holes. In this embodiment of the patient interface 10, the outlet comprises fixed-aperture bias vent holes. The outlet 216 enables respiratory gas to be vented from the cushion module 20.

[0093] In another embodiment, the outlet may be configured to deliver respiratory gas from the second chamber 228 to a conduit. The conduit can be a portion of a dual limb NIV circuit. The conduit may carry respiratory gases to a ventilator or atmosphere.

[0094] The dividing wall 230 partitions the cushion module 20 internally to define the first chamber 226 and the second chamber 228. The dividing wall 230 separates the first chamber 226 from the second chamber 228 by extending all the way across the internal volume of the cushion module 20. In other words, the perimeter of the dividing wall 230 seals with the outer wall 288. A meeting line 282, notionally shows where the dividing wall 230 meets the outer wall 288. In particular, the dividing wall 230 extends all the way across between the first chamber 226 and the second chamber 228. The sealing of the first chamber 226 from the second chamber 228 means that the only flow of respiratory gas between the first chamber and the second chamber is through the flow directors 246.

[0095] The dividing wall 230 permits respiratory gas to flow from the first chamber 226 to the second chamber 228 only via the flow directors 246 (see Figures 10 to 16). The dividing wall 230 includes a forward panel 232 that links to the distal side 938 of the outer wall 288 and is distal of the deformation panel 294. The dividing wall 230 includes a rearward panel 234 that links to the proximal side 940 of the outer wall 288 and is proximal of the deformation panel 294. For the most part, the deformation panel 294 separates the forward panel 232 from the rearward panel 234. However, the forward and rearward panels 232, 234 meet along a notional line that extends laterally beyond the deformation panel 294 to the outer wall 288. The notional line is contiguous with the link between the forward panel 232 and the deformation panel 294.

[0096] The dividing wall 230 of the cushion module 20 has a generally planar transverse profile. This is shown by the meeting line 282 in Figure 12 extending below the bias vent holes 216 and across the lip superior wall portion 268. Thegenerally planar transverse profile of the dividing wall 230 results in the given volume ratio of the second chamber 228 to the first chamber 226. The patient interface 10 has a volume ratio of the second chamber to the first chamber in the range of 0.05:1 to 0.7:1.

[0097] The frame 30 includes the central body portion 302 that includes one or more passages for conveying respiratory gas from a gas source to the cushion module 20 to the patient. The frame 30 includes side wings 304 extending from the central body portion 302. Each side-wing 304 includes a pair of openings 308 are arranged to co-operate with headgear (such as resilient straps) for fitting the patient interface to a patient. The headgear operates by pulling the patient interface 10 into contact with the patient’s face to form a substantially air-tight seal when respiratory gas at elevated gas pressure is delivered to the patient via the patient interface 10. One opening 308 on each side wing 304 includes a bar 306 for connecting with a headgear clip to allow for easier connection to and disconnection from headgear.

[0098] In other embodiments, the headgear connection point may be on the housing.

[0099] The frame 30 further includes a connector sleeve 310 that includes four arcuate fingers 316. The connector sleeve 310 has an inner wall 314 which includes a concave profile having the shape of shape of a spherical segment. The outer wall 312 of the connector sleeve 310 is shaped to fit within the sleeve 212 of the housing 202. The arcuate fingers 316 are spaced by detents which are shaped to fit with the key formations 214. The location of the key formations 214 and the detents ensures that the frame 30 aligns correctly with the housing 202 when they are fitted together.

[0100] Each arcuate finger 316 has an end with an arcuate flange portion 318 which forms a snap-fit with a radially inwardly projecting lip 298 of the sleeve 212. The snap-fit holds the frame 30 to the housing 202. The snap-fit may be releasable or may be a permanent fit between the frame 30 and the housing 202. Instead of a snap-fit, the frame 30 may be connected to the housing 202 by any conventional means, such as gluing or welding. Such connection between the frame 30 and the housing 202 may be permanent or may enable releasable connection of the frame 30 to the housing 202.

[0101] In another embodiment, the housing 202 and the frame 30 are integral. The patient interface 10 may include a unitary structure that performs the same function of the housing 202 and frame 30. While the housing 202 and the frame 30 are described as being separate components of the patient interface 10, the description should be read as including the option of an integrally formed component that functions in the same way as the housing 202 and frame 30.

[0102] The conduit connector 40 includes an elbow 60 and a socket insert 50 which couples the elbow 60 to the frame 30. The conduit connector 40 further includes a swivel connector 80 (not shown) which connects to a conduit that delivers respiratory gas from a flow source, such as a ventilator, a flow generator, a humidifier or a wall source. The swivel connector 80 (not shown), elbow 60 and socket insert 50 form a flow path for respiratory gas into the cushion module 20 from a conduit.

[0103] The socket insert 50 has an outer wall 502 that includes a convex spherical segment. The shape of the spherical segment fits with the shape of the concave spherical segment of the inner wall 314 of the frame 30. The outer wall 502 is joined at one end to an inner wall 504. The inner wall 504 includes an inner surface 506 that includes radially inwardly projecting shoulder 508. The socket insert 50 press fits with the frame 30 such that the outer wall 502 seats in the concave segment of the inner wall 314 of the frame 30. This connection forms a ball and socket style connection which allows the socket to rotate within the spherical segment of the inner wall 314 of the frame 30.

[0104] The elbow 60 includes a first conduit portion 602 and a second conduit portion 608. Longitudinal axes of the first conduit portion 602 and the second conduit portion 608 are set at an oblique angle. Accordingly, respiratory gas flowing through the elbow 60 undergoes a change of direction from the first conduit portion 602 to the second conduit portion 608. The conduit portion 602 includes a radially projecting flange 606. The elbow 60 is connected to the socket insert 50 by snap fitting the flange 606 with the shoulder 508. In other embodiments, however, the elbow 60 may be connected to the socket insert 50 by welding or by adhesive, in which case the shoulder 508 and the flange may be omitted.

[0105] The second conduit portion 608 includes an inlet 610 for respiratory gas. The inlet 610 is at the distal end of the second conduit portion 608.

[0106] The second conduit portion 608 further includes a structure that co-operates with an anti-asphyxiation valve 70 to permit ambient air into the patient interface if the source of respiratory gas fails or the conduit for conveying the gas from the source to the patient interface 10 becomes obstructed.Filter

[0107] The filter 800 shown in Figure 1 is configured for removable coupling with the patient interface 10.

[0108] The filter 800 is a modular component. The modularity of the filter enables a used filter 800 to be replaced with a fresh filter 800 without needing to replace patient interface 10. This results in reduced amounts of waste.

[0109] The filter 800 has a filter body 801 comprising a filter inlet 802, a filter outlet 803 and a sealed passageway 804. The sealed passageway is situated between the filter inlet 802 and the filter outlet 803. The filter inlet 802 is configured to receive gases from the outlet 216 of the patient interface 10. The filter inlet 802 comprises an opening. The filter inlet 802 is in fluid communication with the sealed passageway 804 of the filter body 801 , the filter element 805 and the filter outlet 803. The opening of the filter inlet 802 is on a substantially rear face of the filter body 801. In this embodiment, the filter inlet 802 extends over at least half of the surface area of the rear face. The opening of the filter inlet 802 is in a central location on the filter body 801. The filter inlet 802 follows the contours of the patient interface 10 such that the filter inlet 802 is positionable in abutment with and over the outlet 216 of the patient interface 10. When the filter 800 is coupled to the patient interface, the opening of the filter inlet 802 is aligned with the outlet 216.

[0110] The opening of filter inlet 802 is a singular opening. This offers low resistance to flow compared to multiple smaller openings. The opening of the filter inlet 801 also has a low resistance to flow compared to the filter element 805. The filter element 805 is at a distance from the filter inlet 802 which enables gases to readily enter the filter body 801 via the opening of the filter inlet 802.

[0111] When assembled, the filter inlet 802 surrounds the outlet 216 of the patient interface. That is, the filter inlet 802 surrounds the bias holes of the outlet 216 of the patient interface 10. The filter inlet 802 is larger than the outlet 216 of the patient interface 10. By surrounding the outlet 216, the exhaust flow through the outlet 216 is fed to the filter inlet 802. The exhaust flow exiting the patient interface 10 will be at a higher pressure than the pressure within the filter body 801 . This favorable pressure gradient may aid in exhaled gases entering the filter body 801 via the filter inlet 802 and exit via the filter outlet 803.

[0112] The filter 800 abuts the housing 202 of the patient interface 10 as shown in Figures 1 and 10. In some embodiments, it is possible for the filter 800 to abut the frame 30. In some embodiments, the filter 800 may abut a combination of the frame 30 and the housing 202 of patient interface 10.

[0113] The filter 800 comprises a sealing element 806 surrounding the filter inlet 802. In other words, the sealing element 806 surrounds the opening of the filter inlet 802.

[0114] The sealing element 806 is a resiliently flexible component which deforms when forces are applied to it. The sealing element 806 is a bead of material. The sealing element 806 is situated on a protruding lip 807. The protruding lip 807 is described in more detail below.

[0115] The protruding lip 807 projects rearwardly from the rear surface of the filter body 801. The sealing element 806 projects rearwardly from the protruding lip 807. Accordingly, the sealing element 806 is proud of the rear surface of the filter 800. Figures 2 and 3 shows the sealing element 806 surrounding the filter inlet 802. A vertical cross section through the filter body 801 as shown in Figure 3 shows the sealing element 806 extending from the filter inlet 802.

[0116] The protruding lip 807 comprises a rim 824. The rim comprises a rearwardly- facing surface 826. The surface 826 provides a stable surface for the sealing element 806. A flat surface is able resist any compressive forces applied to the free end of the sealing element 806 whilst the sealing element 806 deforms. This improves the ‘air-tightness’ of a seal between the filter 800 and the housing 202 when the filter 800 is coupled to a patient interface 10.

[0117] The sealing element 806 is configured to form a seal surrounding the outlet 216 of the patient interface. When the filter 800 is coupled with the patient interface 10 the filter inlet 802 is in sealing engagement with the outlet 216 of the patient interface 10. The sealing element 806 contacts a portion of the patient interface 10 that surrounds the outlet 216. In the embodiment of the patient interface 10 shown in Figure 11 , the housing 202 of the patient interface 10 comprises the outlet 216. When the filter 800 is assembled to the patient interface 10 as shown in Figure 1, the sealing element 806 compresses when it is pressed against the housing 202. The sealing element 806 is deformed and compressed between the filter body 801 and the housing 202 of the patient interface 10. The filter element 800 is retained on the patient interface 10 by the elongate members 829, 837. The elongate members 829, 837 are arms 829, 837 that engage with the frame 30 of the patient interface 10.

[0118] In another embodiments, the sealing element 806 may be pressed against other parts of the patient interface 10 to form a seal around outlet 216. For example, the sealing element may be designed to be pressed against one or a combination of the frame 30 or the housing 202 to form the seal between the filter inlet 802 and the outlet 216 of the patient interface 10. In another embodiment, the housing 202 and the frame 30 may be integral and the sealing element 806 is pressed up against such a component to form the seal between the filter inlet 802 and the patient interface 10.

[0119] The compression of the sealing element 806 against surfaces of components that are more rigid than the sealing element 806 itself results in the sealing element 806 deforming to a greater degree than the components. In other words, the sealing element 806 is more deformable compared housing 202 and the frame 30. Thus, the sealing element 806 compresses to form a substantially airtight seal. This means, substantially all the gases exiting the outlet 216 of the patient interface 10 enters the filter inlet 802. This way, gases escaping between the sealing element 806 and the patient interface 10 is minimized or even eliminated.

[0120] The sealing element 806 on the protruding lip 807 may be dome shaped. The sealing element 806 may be a polymer such as silicone or rubber. The freeend of the sealing element 806 is configured to resiliently flex and conform to the profile of the patient interface 10 when in contact and assembled.

[0121] Gases exiting the outlet 216 travels through the filter element 805 comprising the filter media 844 before exiting the filter 800. The sealing engagement between the filter inlet 802 and the patient interface 10 minimizes unfiltered gases escaping before entering the filter 800.

[0122] A filter element 805 is positioned adjacent to or near to the filter outlet 803. The filter element 805 is in fluid communication with the filter outlet 803. The filter element 805 is positioned such that substantially all gasses exiting the filter outlet 803 flows through the filter element 805. The filter element 805 is positioned such that substantially all gases that exit the outlet 216 of the patient interface are filtered before exiting via the filter outlet 803.

[0123] In some embodiments, the position of the filter element 805 will be downstream or abutting filter outlet 803. This means gases must travel through the filter element 805 to exit the filter 800. In some embodiments, the position of the filter element 805 may be near the filter outlet 803 but within the sealed passageway 804. That is, the filter element 805 may be positioned upstream of the filter outlet 803. This will also be effective in filtering gases flowing out of the filter outlet 803.Filter inlet and filter outlet

[0124] The filter inlet 802 is large enough to surround the outlet 216 of the patient interface 10. Too large a filter inlet 802 and filter becomes bulky and uncomfortable for the user to wear. The filter 800 is smaller relative to the patient interface 10. The filter inlet 802 is sized to surround the outlet 216 of the patient interface 10. This means substantially all gases exiting the outlet of the patient interface 10 enters the filter inlet 802. As a result, all gases that exit the filter 800 are filtered. The level of filtration will depend on the properties of the filter element 805 and the filter media 844.

[0125] The filter inlet 802 has an opening area that is smaller than the opening area of the filter outlet 803. A smaller opening area of the filter inlet 802 and a larger opening area of the filter outlet 803 allows gases entering the filter inlet 802 to slowdown as it travels through the sealed passageway 804. As gas slows down it expands within the sealed passageway 804 of the filter body 801 . This means the gas occupies substantially the entirety of the inner portion of the filter body 801. As a result, gas flow exiting the filter body 801 is filtered by substantially the entirety of the filter element 805. This increases the efficiency and reduces waste as substantially the entire surface area and / or volume of the filter media 805 is used to filter the gases. On the contrary, if the gases were not given the volume to slow down and potentially expand only a localized area of the filter element 805 will be filtering the gases which is wasteful. Gas is driven through the filter element 805 by the pressure differential between the filter inlet 802 and the atmosphere, for example the pressure of the room.

[0126] The filter 800 does not significantly increase the resistance to flow through the outlet 216 of the patient interface 10. The filter inlet 802 has an opening area that is larger than the outlet 216 of the patient interface 10. This means, the filter inlet 802 has a lower resistance to flow compared to the outlet 216 of the patient interface 10. This reduces the chance of flow entering the patient interface 10 from the filter 800.

[0127] In situations where the patient is exhaling, the pressure in the sealed passageway 804 will be higher than the ambient pressure allowing for gases to exit the filter 800 without re-entering the patient interface 10.

[0128] With reference to Figure 4, the opening area of the filter inlet 802 is less than the opening area of the filter outlet 803. The opening area of the filter inlet 802 is represented by a dash-dot line 813 and the opening area of the filter outlet 816 is indicated by a dashed line 816. A first cross sectional area at or near the filter inlet 802 is smaller compared to the second cross-sectional area at or near the filter outlet 803. The cross-sectional areas, that is the first and second cross sectional areas taken for reference lay within the sealed passageway 804, at the filter inlet 802 or the filter outlet 803. The cross-sectional area is taken perpendicular to axis A1 which is perpendicular to the plane of the page.

[0129] The ratio between the opening area of the filter inlet 802 and the opening area of the filter outlet 803 may be between 0.01 :1 to 0.99:1 , or between 0.09:1 to 0.8:1 , or between 0.1 :1 to 0.6:1. Preferably, the ratio between the opening area ofthe filter inlet 802 and the opening area of the filter outlet 803 is between 0.1 :1 to 0.5:1.

[0130] In this embodiment, the filter inlet 802 is an elongate opening. The filter inlet802 opening is substantially oval shaped opening. In other embodiments, the filter inlet 802 may be any shape that is capable of surrounding an outlet 216 of a patient interface 10. For example, the filter inlet 802 opening may be a polygonal or a curvilinear shape. That is, the filter inlet 802 may be a substantially rectangular with rounded edges.Sealed passageway

[0131] Figure 3 shows a sealed passageway 804 on the filter body 810. Gases entering the filter inlet 802 flows through the sealed passageway 804 to the filter outlet 803. The sealed passageway 804 is a portion of the filter extending between the filter inlet 802 and the filter outlet 803. The sealed passageway 804 is formed as a singular, unitary structure with the filter inlet 802 and the filter outlet 803. The lack of joining portions in the sealed passageway 804 ensures no gases escape through the sealed passageway 804 to the atmosphere.

[0132] In some embodiments, sealed passageway 804 is formed as a singular, unitary structure with the filter inlet 802, the filter outlet 803 and the filter element 805.

[0133] The filter inlet 802 is located at a distance from the filter outlet 803. Figure 3 shows the sealed passageway 804 spaces the filter inlet 802 at a distance away from the filter outlet 803. The distance from the filter inlet 802 to the filter outlet803 is between 1 mm to about 15 mm. The distance from the filter inlet 802 to the filter outlet 803 may be greater than 7mm. In this embodiment, the distance 817 from the filter inlet 802 to the filter outlet 803 is about 10 mm. The distance 817 is selected to allow the gases to sufficiently expand before the gases reach the filter media 844.

[0134] Gases that exit the outlet of patient interface 10 through the outlet 216 may be of high dynamic pressure. If the filter inlet 802 is too close to the filter outlet 803, it is likely that the total surface area of the filter media 844 is not utilized. It isbeneficial to allow the gases to expand before entering the filter element 805 comprising the filter media 844 and exiting the filter 800.

[0135] Expansion of gases occurs within the filter body 801. Specifically, the expansion of gases may occur within the sealed passageway 804. This allows the gases exiting the patient interface 10 to utilize the available surface area of the filter media 844 before exiting via the filter 800.

[0136] The sealed passageway 804 may comprise a change in geometry 818. The change in geometry 818 is an expansion of the sealed passageway 818 from a smaller cross-section 813 or volume associated with the filter inlet 802, to a larger cross-section 816 or volume associated with the filter outlet 803. The change in geometry 818 may be at a localised portion of the sealed passageway 804. The change in geometry 818 may comprise a step change of a wall of the sealed passageway 804. The step change may closely resemble a stair like formation on the sealed passageway 804. In other words, a front facing wall of the change in geometry 818 may be at an angle between 40° to 100°. The width of the front facing wall of the change in geometry 818 may be variable. Wherein, at the bottom of the filter 800 the change in geometry 818 may have a wider wall compared to the top of the filter 800.

[0137] In some embodiments, the change in geometry 818 comprises a gradual expansion of a wall of the sealed passageway 804. The angle of expansion of the sealed passageway 804 may be between 1° to 40° with respect to a plane along axis A1 .

[0138] The change in geometry 818 may cause gases entering the filter inlet 802 to decrease in pressure before passing through the filter outlet 803 and the filter element 805.

[0139] In some embodiments, the change in geometry 818 may be gradual. For example, the change in geometry may be a gradual change. Such gradual change may comprise the sealed passageway expanding at an angle of 7° from the filter inlet 802 to the filter outlet 803.Protruding lip

[0140] The filter body 801 comprises a protruding lip 807 surrounding the filter inlet 802, shown in Figures 2 and 3. The protruding lip 807 provides a seat for the sealing element 806. The sealing element 806 is affixed to the protruding lip 807. The sealing element 806 may be joined to the protruding lip 807 by mechanical or chemical bonding, for example utilizing an interference fit, over-moulding or adhesion.

[0141] The protruding lip 807 extends from the portion of the filter body 801 surrounding the filter inlet 802. The protruding lip 807 may surround the entirety of filter inlet 802. A face at a free end of the protruding lip 807 is substantially flat. The free end of the protruding lip 802 is the end that is configured to interface with the sealing element 806. At the opposing end of the free end of the protruding lip 807 it is connected to the filter body 801 .

[0142] The protruding lip 807 may comprise a width 823 in the proximal-distal direction (Figure 3). The width 823 may be a varying width 823 as described below. The width 823 of the protruding lip 807 is the distance it projects from a plane of the opening of the filter inlet 802. In other words, the protruding lip 807 projects from a rear surface of the filter 800. The varying width may be greater than 1 mm. The varying width may be less than 5mm. The varying width 823 of the protruding lip 807 is between about 1 mm to 10mm.

[0143] The varying width 823 is selected to align with the contours of the patient interface 10. Aligning with the contours when the filter 800 is assembled to the patient interface 10 will result in sufficient compression of the sealing element 806 to form a seal. In another embodiment, the varying width 823 may be greater at a first portion of the filter body 801 compared to a second portion of the filter body 801 . The first portion of the filter body 801 may be configured to be at the top when the filter 800 is assembled to a patient interface 10. The second portion of the filter body 801 may be configured to be at the bottom when the filter 800 is assembled to a patient interface 10.

[0144] As a result of the variable width 823 of the protruding lip 807, the cross- sectional area of the sealed passageway 804 between the proximal and distal ends of the protruding lip 807 increases in the distal direction from the filter inlet 802. In this embodiment, an upper portion 818 of the protruding lip 807 is less wide in theproximal-distal direction than the width 823 of a lower portion 820 of the protruding lip 807 in the proximal-distal direction. In some embodiments, the change in cross- sectional area may be gradual. For example, the protruding lip 807 may project from the rear surface of the filter 800 to form an obtuse angle with the rear wall. This provides a gradually increasing cross-sectional area in the proximal direction. In some embodiments, the gradual change the obtuse angle is between 91° to 100° or between 92° to 98° or about 97°.

[0145] In some embodiments, the protruding lip 807 may project from the rear surface of the filter 800 to form a right angle or an acute angle with the rear wall.

[0146] The protruding lip 807 comprises an inwardly projecting rim 824. A rearward facing surface 826 of the rim forms a base to which the sealing element 806 is affixed. When the filter 800 is abutted with the outlet 216 of the patient interface 10, the sealing element 806 will compress. The rearward-facing surface 826 of the rim 824 provides a stable seat for the sealing element 806 when compressed. In this embodiment, the protruding lip 807 varies in width 823. In another embodiment, the width 823 of the protruding lip 807 may be a substantially constant.

[0147] In some examples, the filter 800 may not have a protruding lip 807, instead the sealing element 806 may be attached to the rear wall of the filter body 801 around the filter inlet. The sealing element 806 may be disposed on the filter body 801 and affixed to the filter body by over-moulding or using a chemical adhesive to form a chemical bond.The filter element

[0148] The filter element 805 is the portion of the filter 800 that filters the gases travelling through the filter body 801 . The filter element 805 comprises a filter media 844. The filter media 844 may collect particles whilst the filtered gases proceed out of the filter 800. The particles that the filter media 844 collects may be one of more of: water vapor, impurities or particles of a size larger than the porosity of the filter media 844.

[0149] The filter element 805 is disposed adjacent to the filter outlet 803. In Figures 1 to 3, the filter element 805 interfaces with the edge of the filter body 801 defining the filter outlet 803. The filter element 805 is situated after the filter outlet 803 suchthat gases exiting the filter outlet 803 enters the filter media 844 of the filter element 805 before exiting the filter 800.

[0150] The filter element 805 encompasses the entire opening of the filter outlet 803 such that all gases that travel through the outlet 803 is filtered by the filter media 844 of the filter element 805.

[0151] In this embodiment, the filter media 844 comprises a polypropylene or an acrylic material. In another embodiment, the filter media 844 comprises a polypropylene and an acrylic material.

[0152] The filter element 805 further comprises a filter frame 822. The filter frame 822 surrounds the filter element 805. The filter frame 822 substantially contacts the perimeter of the filter media 844. The filter frame 822 has sufficient structural integrity to support the filter media 844. The filter frame 822 is substantially rigid and able to hold a preformed shape such that it can be attached onto the filter body 801.

[0153] The filter frame 822 interfaces with the filter outlet 803 of the filter body 801 . The filter frame 822 is over-moulded to at least a portion of the perimeter of the filter media 844. The filter frame is over-moulded to the whole of the perimeter of the filter media 844. Other methods of attaching the filter frame 822 to the filter media 844 include but are not limited to the use of adhesives and / or mechanical fasteners and / or mechanical fastening an example of which is given below.

[0154] In the embodiment shown in Figures 1 to 8, the filter frame 822 is integral with the filter body 801 . The filter frame 822 may be over-moulded together with the filter body for seamless integration. A joint between the filter frame 822 and the filter body 801 is substantially free of gaps such that the gases do not leak from the joint. Over-moulding the filter element 805 to the filter body 801 minimises the chances of gaps through which gases could leak.

[0155] In other embodiments mechanical fastening may be utilized whereby the filter frame 822 of the filter element 844 may comprise a channel to receive the filter outlet 803 of the filter body 801 . The channel may comprise a seal such that when assembled to the filter body 801 , the joint between the filter frame 822 and the filter body 801 forms a substantially leak-proof engagement.

[0156] Figure 6 shows an exploded view of the filter body 801 and the filter element 805. In this embodiment, the filter element 805 comprises the filter media 844 and the filter frame 822. The filter body 801 comprises the elongate member 827, the filter inlet 802, the filter outlet 803, the sealing element 806 and the protruding lip 807. The filter element 805 is assembled to interface with the filter outlet 803 to the filter body 801 . The filter element 805 may be assembled onto the filter outlet 803 via an interference fit between it and the filter frame 822. In another embodiment, the filter element may be over-moulded to the filter body 801 .

[0157] In some embodiments, the filter element 805 may fit within the filter outlet 803 or the filter element 805 may be fitted near to or adjacent to the filter outlet 803. In some examples, the filter element 805 may be situated on the sealed passageway 804 rearward to the filter outlet 803. In such an embodiment, the gases exiting the filter outlet 803 will be filtered by the filter element 805 before it exits the filter outlet 803.Filter cover

[0158] The filter element 805 comprise a filter cover 808. Figures 7 and 8 show an alternative embodiment of a filter 900 which comprises a filter cover 808. The filter 900 comprises all the features described in relation to filter 800.

[0159] The filter cover 808 is configured to extend across a surface of the filter media 844. The filter cover 808 is a structure that is placed over the filter media 844, in front of the filter media. The filter cover 808 may be offset from or contacting an outer surface of the filter media 844. The filter cover 808 may span across the entirety of the filter media 844. The filter cover 808 may overhang the past edges of the filter media 844 and / or the filter frame 822.

[0160] The filter cover 808 comprises a lattice. The lattice comprises a series of openings 825. In this embodiment, the openings 825 are square-shaped. In other embodiments, the openings 825 may rectangular, round, triangular, pentagonal, hexagonal or octagonal. The openings may be arranged in a pattern or may be arranged randomly.

[0161] The filter cover 808 provides some protection to the filter media 844 from damage. Also, the filter cover 808 reduces the chances of objects perforating thefilter media 844. A torn filter media 844 allows gases to pass through it without filtration. The plurality of openings 825 are small such that the cover 808 prevents objects, including fingers, being inserted into the filter media 844. The size of one opening of the plurality of openings may be between 1 mm2to 5 mm2. The size of one opening of the plurality of openings may be less than about 1 mm2.

[0162] The filter cover 808 minimizes the blockage of the filter media 844 while keeping pathways open for gases to exit the filter 800 via the filter media 844. This plurality of openings 825 are sized such that it has a lower resistance to flow than the filter media 844. The filter cover 808 has openings 825 that are larger than the openings through the filter media 844 such that gases encounter less resistance to flow when passing through the filter cover 808 than when passing through the filter media 844.

[0163] The outer profile of the filter cover 808 matches the outer profile of the filter element 805. This allows for the filter cover 808 to be applied to the filter body 801 .

[0164] In this embodiment, the cover 808 may be integrally formed with the filter frame. The filter cover 808 may be over-moulded to the filter frame 822. In another embodiment, the filter cover 808 is removably couplable to the filter frame 822. The filter cover 808 may be coupled to the filter frame 822 via a mechanical interference fit.

[0165] The filter 800, 900 comprises a coupling mechanism which allows the filter 800,900 to be attached to the patient interface 10. The filter 800, 900 may comprise a coupling mechanism configured to removably couple the filter 800, 900 to the patient interface 10. The coupling mechanism comprises a pair of elongate members. Each elongate member is an arm 829, 837. The coupling mechanism may be attached to the filter body 801 on opposing sides of the filter body. This is shown in Figure 10. The elongate members of filter 900 operates in a similar manner to those of filter 800. The elongate member are described elsewhere in the specification with relation to filter 800.

[0166] In some examples, the coupling mechanism may be attached to the filter cover 808 (not shown). The coupling mechanism comprises a first elongate member and a second elongate member attached to the first side and a second side of the filter cover 844. The elongate member(s) are attached to the filter cover844 by a pivoting attachment. The pivoting attachment may comprise a short member that is able to flex and bend upon application of a force. The short member at one end is attached to the filter body 801 and at the second end 836 is attached to the elongate member.

[0167] By pressing a first end 835 that of the elongate member(s), the end distal to the first end 835 moves in an opposing direction. Thus, when the first end 835 of each of pair of elongate members are forced towards each other the distal ends of the elongate members will be widened. Releasing the force on the first end 835 of the elongate member(s) causes the distal ends to spring back into their rest position. The elongate member(s) are able to recoil back to the starting or rest position due to the resiliently flexible nature of the elongate members themselves and the pivoting attachment.

[0168] The elongate members and the pivoting attachment may constructed from polymers and or metals.Filter assembly with patient interface

[0169] The filter 800 is configured to be attached to the patient interface 10 as shown in Figures 1 and 10. That is, the filter inlet 802 is aligned with an outlet 216 of the patient interface 10 and located in position by the arms 829, 837.

[0170] Figure 10 shows the filter body 801 is substantially curved in a top-down view such that is it is configured to follow the curvature of the patient interface 10. Figure 10 shows the curvature of the filter body 801 which is indicated by the dotted line 32. The substantially curved shape of the filter body 801 allows for better abutment of the filter inlet 802 with the outlet of the patient interface 10. The curvature of the filter 800 may be C-shaped or concave.

[0171] The curvature of the filter 800 may also follow the concavity of a patient’s head in the transverse plane.

[0172] Additionally, curved filter body 801 lays close to the patient interface which makes it a low-profile attachment. The curved filter body 801 also allows for the sealing element to follow the curvature of the patient interface 10 closely. This means when assembled, the sealing element compresses 806 substantially evenly.This is advantageous as the chance of weaker locations of engagement between the sealing element 806 and the patent interface 10 is reduced.

[0173] The filter 800 is removably couplable to the patient interface 10. Removably coupled means that the filter 800 is able to be attached and removed without the filter 800 or the patient interface 10 sustaining damage. Damage includes destruction or disintegration of the structural components of the patient interface 10 which makes the patient interface 10 ineffective in use. Removably couplable may also mean that the filter 800 may be repeatedly attached and removed from the patient interface 10 with ease and no considerable damage to either part.

[0174] In the embodiment shown in Figures 1 to 6, removable coupling of the filter800 is achieved by the coupling mechanism 809.Coupling mechanism

[0175] The coupling mechanism 809 is shown in at least Figures 1 to 10. The coupling mechanism 809 comprises at least one elongate member configured to removably couple with the patient interface. In the filters 800 and 900, the at least one elongate member comprises arms 829, 837. The arms 829, 837 are integral to the filter 800, 900.

[0176] The arms 829, 837 extend in the direction of a horizontal axis A1 (Figure 4). The arms 829, 837 extend beyond the filter body 801 in the proximal direction to enable coupling with the patient interface 10. The arms 829, 837 are substantially parallel to the sealed passageway 804 of the filter body 801. The arms 829 also extend substantially parallel to the filter body 801 in a distal direction past the filter element 805.

[0177] The arms 829, 837 are connected to the filter body 801 . In the filters 800 and 900, the arms 829, 837 are integral to the filter body 801 . As an example, this integration may be achieved by moulding together the filter body 801 with the arms 829, 837. In other embodiments, the arms 829, 837 may be joined to the filter body801 with the use of an adhesive or mechanically coupled together.

[0178] The arms 829, 837 may be made from the same material as the filter body 801 . The arms 829, 837 may be resiliently flexible such that it can be flexed or bent for attachment to or removal from the patient interface 10. That is, the arms 829,837 are able to be flexed or bent without the arms 829, 837 sustaining permanent deformation or damage that makes it unusable.

[0179] The arm 829 is connected at a first side 810 of the filter body 801 via a first connection 830. The arm 837 is connected at a second side 811 of the filter body 801 via a second connection 838. The first side 810 of the filter body 801 and the second side 811 of the filter body 801 are opposing sides. This enables a user to grip the arms 829, 837 with one hand.

[0180] The first side 810 of the filter body 801 and the second side 811 of the filter body 801 may be at extremities of the filter body 801 . This makes the arms 829, 837 the outermost placed components of the filter 800, 900. The placement of the arms 829, 837 enables a user to grasp the arms 829, 837 without having their fingers obstructed by other components of the filter 800, 900.

[0181] The first connection 830 and the second connection 838 may each be a hinged, pinned or a fixed connection. The hinged connection may be a living hinge connection.

[0182] The arms 829, 837 are formed as a unitary structure with the filter body 801 . The arms 829, 837 are seamlessly integrated with the filter body 801 . A seamlessly integrated structure is one that has no visible joints or componentry that facilitate the joining of the individual parts. The lack of mechanical joints reduces small individual parts close to the nose or the mouth.

[0183] The arms 829, 837 may be moulded together with the filter body 801 . Other methods to form a unitary structure of the arms 829, 837 and the filter body 801 is via additive manufacturing techniques.

[0184] The filter 800, 900 is removably couplable with the patient interface 10. A removably couplable assembly requires the user to be able to easily assemble and disassemble the filter onto the patient interface 10.

[0185] The filter 800, 900 is removably coupled to the patient interface 10 using the at least one elongate member. In the example of the filter 800, 900 shown, removable coupling is achieved using the arms 829, 837. The arms 829, 837 are connectable to the filter body 801 using a first connection 830. The first connection may be a pinned or hinged connection. A force applied at a first end 835 of thearms 829, 837 causes the second end 836 of the arms 829, 837 to move in an opposite direction to the force ‘F’ applied. That is, the arms 829, 837 moves about the first connection 830 wherein the movement may be a combination of rotation and / or translation.

[0186] The arm 829 is a first beam 839 that is attached to the filter body 801. The arm 829 may be attached to the filter body 801 by a first connection 830. The first connection 830 is a second beam 831 that extends from the filter body 801. The second beam 831 is shorter than the first beam 839.

[0187] The first beam 839 is at an angle to the second beam 831. The angle between the first beam 839 and the second beam 831 may be between 0° to about 120°. Preferably the angle between the first beam 839 and the second beam 831 is approximately 90°. That is the angle between the first beam 839 and the second beam 831 are substantially perpendicular.

[0188] In the embodiments of the filter 800, 900, the first beam 839 and the second beam 831 are integral parts.

[0189] Similarly, the arm 837 is a third beam 846 that is attached to the filter body 801 . The arm 837 is attached to the filter body 801 by a second connection 838. The second connection 838 is a fourth beam 847 that extends from the filter body 801 . The fourth beam 847 is shorter than the third beam 846.

[0190] The angle between the third beam 846 and the fourth beam 847 may be between 0° to about 120°. Preferably the angle between the third beam 846 and the fourth beam 847 is approximately 90°.

[0191] Figure 5 shows a first connection 830 and a second connection 838 that attaches the arms 829, 837 to the filter body 801 .

[0192] The first connection 830 and the second connection 838 are a hinging connection. The first and second connections 830, 838 comprise a beam 831 , 847 that links the respective arms 829, 837 to the filter body 801 . The arms 829, 837 may act as a hinge. The first and second connections 830, 838 and the arms 829, 837 are resilient. That is, a force ‘F’ applied to the first ends 835 of the arms 829, 837 in the direction of the other first end 835 causes the opposite second end 836 to move in a direction opposite to the direction of force ‘F’. The movement ispossible due to a combination of the arms 829, 837 and the first and second connections 830, 838 comprising beams 831, 847 being able to deflect. The deflection causes the distance between the second ends 836 of the arms 829, 837 to widen.

[0193] The arms 829, 837 are biased towards their “rest position” (as shown in Figures 2, 3 and 5). The rest position is that where the elongate member 829, 837 are undeflected. The biasing force arises from the elastic material properties of the arms 829, 837 and the first and second connections 830, 838. In other embodiments, the biasing force may arise from the arms 829, 837 or from the first and second connections 830, 838, but not both.

[0194] Upon removal of force ‘F’ from the first end 835 of the arms 829, 837, the second end 836 of the arms 829, 837 returns to the undeflected position. The undeflected position is substantially the position the elongate member 829, 837 were in before application of the force.

[0195] With reference to Figure 5, the user grips the first end 835 of the arms 829, 837. The force applied by the user is indicated in Figure 5 with the arrow labeled ‘F’. This causes the arms 829, 837 to undergo a substantially rotational movement about the first and second connections 830, 838. The distance between the second end 836 of the arms 829, 837 becomes larger. This enables the user to apply the filter 800, 900 over the patient interface 10. Releasing the force causes the distance between the second end 836 of the arms 829, 837 to return to the rest position. The force between the elongate members 829, 837 tending towards its rest position cases the filter to be held on to the patient interface 10.

[0196] This the arms 829, 837 to grip the patient interface 10 with the aid of a first protrusion 832 and a second protrusion 840. The first protrusion 832 and the second protrusion 840 are integral with the first elongate member 829 and second elongate member 837, respectively at the second end 836. The first protrusion 832 and second protrusion 840 protrude in a direction towards the middle of the filter body 801.

[0197] Figure 11 shows a patient interface 10 to which the filter 800, 900 may be attached. The arm 829 is inserted into a first aperture 841 on the patient interface 10. The surrounding wall of the first aperture 841 has a recess (not shown) toreceive the first protrusion 832. Similarly, the arm 837 is inserted into a second aperture 833 on the patient interface 10. The surrounding wall of the second aperture 833 has a recess 845 (not shown) to receive the second protrusion 840. That is, the filter 800 is retained on the patient interface 10 by the reaction force between the first and the second elongate members 829, 837 against the recess 845 and by the biasing force of the arms 829, 837 and the first and second connections 830, 838 which retain the first and second protrusions 832, 840 within the recesses 845.

[0198] The magnitude of force required to widen the second end 836 of the arms 829, 837 may be tuned by the location of the first connection 830 and the second connection 838, respectively, along the arms 829, 837. The first and second connections 830, 838 are located substantially midway along the arms 829, 837. To widen the second end 836 of the arms 829, 837, the user applies equal and opposing forces ‘F’ to the first end 835 of the arms 829, 837.

[0199] In other embodiments, the first and second connections 830, 838 may be located substantially closer to the first end 835 of the arms 829, 837. This requires more force from the user to widen the second end 836.

[0200] There may be a preformed angle 834 between each of the filter body 801 and the arms 829, 837. The preformed angle is between about 0° and 135°. The preformed angle 834 is measured between the arms 829, 837 and filter body 801 . More specifically, the preformed angle 834 is measured at the intersection and between a longitudinal axis of the arms 829, 837 to a tangential axis of the curved surface of the filter body 801 where it meets the respective first or second connection 830, 838.

[0201] The preformed angle 834 is associated with the space through which the first end 835 of the arms 829, 837 is allowed to move freely through. A larger preformed angle 834 allows for the arms 829, 837 to move freely a greater angular distance compared to a smaller preformed angle 834. The preformed angle 834 may be adjusted such that the arms 829, 837 only move a desired distance. That is, the preformed angle 834 may be a passive stop to prevent the elongate members 829, 837 from being overextended.

[0202] Figure 11 and 13 shows a first aperture on the patient interface. The filter800, 900 is retained on the patient interface 10 by the reaction force between the arms 829, 837 against the frame 30 of the patient interface 10. Upon successful assembly, a first protrusion 832 on the arm 829 member locates itself on the surrounding wall of the first aperture 841 of the frame 30 of the patient interface 10. Similarly, a second protrusion 840 on the arm 837 locates itself on the surrounding wall of the second aperture 833 of the frame 30 of the patient interface 10. Figure 1 shows the arms 829, 837 located within the first aperture 841 and the second aperture 833.

[0203] In another embodiment, the arms 829, 837 may be attached to the filter body 801 by living hinge connections. The living hinge may be provided by a portion of the filter body 801 .The living hinge may comprise at least one slit on the filter body801 . The at least one slit separates a portion of the filter body 801 such that the portion is movable in relation to the rest of the filter body 801. The respective arms 829, 837 are connected to the portion of the filter body 801 formed by the slit. The first connection and the second connection are at the location where the portion of the filter body 801 formed by the slit is attached to the arms 829, 837.

[0204] The portion of the filter body 801 formed by the slit is more flexible than the elongate members 829, 837. This is because the portion of the filter body 801 formed by the slit may be thinner than the arms 829, 837. This means that when the user applies the force ‘F’ on a first end 835 of the elongate member, the portion of the filter body 801 formed by the slit pivots about the slit to move the second end836 in the opposite direction of force ‘F’.

[0205] In another embodiment, the living hinge may comprise a first slit and a second slit on the filter body 801. The portion between the first slit and the second slit is the living hinge which connects to the arms 829, 837. The portion between the first slit and the second slit is a locally mobilised portion. A first arm 829 is attached the first side of the filter body 801 via a first connection and a second arm837 is attached the second side of the filter body 801 via a second connection. The first connection and the second connection each comprises a first slit and a second slit such that the locally mobilised portion of the filter body is pivotable in relation to the rest of the filter body 801 . By gripping the first end 835 of the arm 829 and asecond end 836 of the arm 837 and applying a force in the direction towards the midline of the filter 800, the second end 836 of the arm 829 and the second end 836 of the arm 837 are moved away from each other. This enables the user to apply the filter 800, 900 over the patient interface 10. Releasing the force causes the distance between the second end 836 of the arms 829, 837 to return to the rest position. This causes the arms 829, 837 to grip and hold on the patient interface 10.

[0206] There is a preformed angle 834 between each of the filter body 801 and the respective arms 829, 837. The preformed angle positions the first end 835 of the arms 829, 837 at a desired distance to the filter body 801 . The preformed angle is between about 1° and 50°. In some examples, the preformed angle may be between 0° and 90°, or between 0° and 70°, or between 0° and 60°. The preformed angle 834 allows the first end 835 of the arms 829, 837 to be squeezed towards the filter body 801 when the user applies a force at the first end 835.

[0207] In another embodiment shown in Figure 19, a filter 1000 comprises arms 1829, 1837 that are attached to the filter body 801. The arm 1837 extends parallel to the filter body 801 in the direction towards the filter inlet 802. The arm 1837 extends past the filter inlet 802. The arm 1837 has a first end 835 attached to the filter body 801. The second end 836 of the arm 1837 is a free end.

[0208] An engaging arm 1841 extends generally in a distal direction from the second end 836 of the arm 1837. That is, the engaging arm 1841 is joined with the arm 1837 at the second end 836. The engaging arm 1841 has a free end at its distal end. The engaging arm 1841 is at an angle to the arm 1837. That is, a longitudinal axis of the engaging arm 1841 is at an angle to a longitudinal axis of the support arm 1839. The angle may be between about 1° and 50°.

[0209] The engaging arm 1841 and the arm 1837 are resiliently flexible. That is, by pushing the free end of the engaging arm 1841 towards the direction of the arm 1837 causes the engaging arm 1841 to move towards the arm 1837. The angle between the engaging arm 1841 and the arm 1837 reduces to approximately 0°. By releasing the force on the engaging arm 1841 at its free end causes the engaging arm 1841 to assume its undeflected state. That is, an angle between the engaging arm 1841 and the arm 1837 becomes close to or equal to the angle it was at rest.

[0210] The arm 1837 is configured to extend towards the aperture 833 of the patient interface 10. A protrusion 1840 on the engaging arm 1841 is configured to engage with a recess in the wall surrounding the aperture 841 in the frame 30 of the patient interface 10. To attach the filter 1000 to the patient interface 10, the user applies force to the free end of the engaging arm 1841 and pushes it towards the arm 1837. The user then inserts the arm 1837 into the first aperture 841 of the patient interface 10. The protrusion 1840 of the engaging arm 1841 snaps into position within the recess on the surrounding wall of the aperture 833 of the patient interface 10. The arm 1837 is retained within the aperture 833 as a result of the reaction force between the engaging arm 1841 and the frame 30 surrounding the aperture 841. In other words, the bias of the engaging arm 1841 to tend to its rest position or undeflected position retains the filter 1000 within the wall of the frame 30 of the patient interface 10 surrounding the aperture 841.

[0211] This embodiment further comprises an arm 1829 attached to an opposite side the filter body 801 to the arm 1837. The arm 1829 has the same components as the arm 1837. It functions in the same was as described above for the arm 1837. In some embodiments, the connection between the engaging arm 1841 and the arm 1837 may be a living hinge.Stop

[0212] The filter body 801 may comprise a first stop 848 configured to make contact with the arm 829. The first stop limits movement of the arm 829. The filter body 801 comprises a second stop 849 configure to make contact with the arm 837. The second stop limits the movement of the arm 837.

[0213] Each of the first stop 848 and the second stop 849 may be a protrusion on the filter body 801 configured to limit the movement of each of the arms 829, 837. The first stop and the second stop may be a portion of the filter body 801 .

[0214] The arms 829, 837 each comprise a finger grip 842. The finger grip 842 comprises a roughened surface and / or protrusions. The finger grip 842 may also be a surface with smooth finish to provide increased tackiness. The finger grip 842 allows the user to hold the filter 800 by each of the arms 829, 837. The finger grip 842 assists the user to grip and assemble the filter to the patient interface 10.Recess

[0215] The filter 800 comprises a recess 812 configured to provide clearance for an inlet elbow 60 of the patient interface 10. The recess 812 is shown in Figure 4. The recess 812 is a narrowing of the filter body 801 towards the midsection of the filter body 801. A bottom portion of the filter body 801 may comprise a recess 812 that is a C-shaped curve. The top of the filter body 801 may also have a recess 850 that is a U-shaped curve.

[0216] The narrowing of the filter body 801 at the bottom of the midsection assists in the avoidance of interference with the inlet elbow 60. The elbow 60 is a connection to the patient interface 10.

[0217] The narrowing of the filter body 801 at the top of the midsection i.e. recess 850 assists in the edges of the filter body 801 stopping short of the edges of the patient interface 10. This has the advantage that the filter body 801 reduces obstruction of the patient’s face and reduces obstruction of the patient’s field of vision.

[0218] The recess 812 assists in the filter 800 being able to access the frame 30 of the patient interface 10. The recess 812 avoids the elbow 60 of the patient interface 10 such that the sealing element 806 of the filter inlet 802 is able to abut the frame 30 of the patient interface 10.An assembly comprising a patient interface and a filter

[0219] The filter 800 and the patient interface 10 form a patient interface assembly that provides filtration for respiratory gases that exit the patient interface 10 via the filter 800. In some embodiments, the filter 800 also provides filtration to the gases that enter the patient interface 10 through the filter outlet 803.

[0220] The assembly comprising the filter 800 and the patient interface 900 may be a part of a ventilator system that comprises a ventilator or a flow generator, inspiratory tubing, expiratory tubing, a heat and moisture exchanger, humidifier, sensors, controllers and relief valves.

[0221] A patient interface assembly may be used for providing positive pressure respiratory therapy to a patient. The patient interface assembly may be used fornon-invasive ventilation therapy which includes but is not limited to positive airway pressure therapy (PAP), continuous PAP therapy, high flow therapy etc. In some embodiments, the gases exiting the filter outlet 803 may enter a conduit. The conduit may be part of an expiratory or exhaust conduit of a respiratory ventilation system.

[0222] In the embodiment shown in Figures 1 to 18, the coupling mechanism 809 of the filter 800 is configured to couple with the frame 30 of the patient interface 10, such that when the frame 30 is coupled to the cushion module 20 the filter 800 is located in abutment with the housing 202. In this arrangement, the sealing element 806 of the filter 800 forms a seal with the housing 202 surrounding the outlet. Accurately and stably locating the filter on the patient interface is important to achieve a good seal. The coupling mechanism 809 on the filter 800 allows for it to be accurately and stably located on the outlet 216 of the patient interface 10.

[0223] An alternative embodiment of a filter 2000 is shown in Figures 21 to 24. The filter is the same as the filter 800 described above in terms of structure and operation. All of the description above regarding the filter 800 is applicable to the filter 2000. Features of the filter 2000 which are shown in Figures 21 to 24 and which are the same as the features of the filter 800 are denoted by like reference numerals but with the prefix “2”.

[0224] The filter 2000 comprises elongate member 2829 and 2837. Each elongate member 2829, 2837 is respectively connected by a second beam 2831 and fourth beam 2847 to a filter body 2801. The second beam 2831 and the fourth beam 2847 act as hinges. A first end 2835 of each elongate member 2829, 2837 comprises a finger grip 2842. The finger grip assists users to grasp the first end 2835 to actuate coupling and decoupling of the filter 2000 with the patient interface 10. The coupling occurs in the same way as described above in respect of the filter 800. That is, the user squeezes the first ends 2835 of the elongate members 2829, 2837 toward each other in order to spread the first and second protrusions 2832, 2840 for seating with or unseating from the respective first and second apertures 833, 841 on the patient interface. To assist this, the filter 2000 comprise push shoulders 2850. The push shoulders 2850 are distal of the second and fourth beams 2831 and 2847. While the finger grips contribute to reducing slippage of fingers acting onthe elongate member 2829, 2837, the push shoulders 2850 capture proximally directed forces applied by a user when fitting the filter 2000 to the patient interface. In other words, forces applied by the user in the same orientation of the elongate members 2829, 2837 are directed into the push shoulders. That force contributes to fitting the filter 2000 to the patient interface 10 because the proximally directed force causes the first and second protrusions 2832, 2840 to spread as they contact and slide over the surface of the patient interface 10 until they reach the respective first and second apertures 833, 841 . The push shoulders 2850 better capture the proximally directed forces than do elongate members 2829, 2837 without the push shoulders.

[0225] The filter 2000 further differs from the filter 800 by comprising an exhaust vent 2860. In the filter 2000, the sealing element 2806 comprises the exhaust vent 2860. In other embodiments, the sealing element may be omitted and protruding lip 2807 may comprise the exhaust vent 2860. The sealing element 2806 extends partly around the filter inlet. Discontinuities in the sealing element form the exhaust vent 2860. In other words, the exhaust vent 2860 comprises gaps in the sealing element 2806. In this embodiment, two segments of the sealing element 2806 are spaced apart from each other about the filter inlet 2802 to form two exhaust vents 2860. In other embodiments, there may be one exhaust vent 2860 or there may be more than two exhaust vents 2860. When the filter 2000 is coupled to the patient interface 10, the sealing element 2806 contacts the patient interface 10. The exhaust vents form a flow channel between with the patient interface 10 and the filter 2000. Respiratory gas from within the patient interface can flow through the channels to externally of the patient interface 10.

[0226] The exhaust vents 2860 are at lateral sides of the filter inlet 2802. This location directs respiratory gas flowing through the exhaust vents 2860 away from the patient. In other embodiments, the exhaust vents 2860 may be at any other location about the filter inlet 2802.

[0227] Those skilled in the art of the present invention will appreciate that many variations and modifications may be made to the preferred embodiment without departing from the spirit and scope of the present invention.

[0228] In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” and variations such as “comprises” or “comprising” are used in an inclusive sense, i.e., to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the apparatus and method as disclosed herein.

[0229] In the foregoing description of preferred embodiments, specific terminology has been resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "front" and "rear", "inner" and "outer", "above", "below", “top”, “bottom”, "upper" and "lower", “underside” and “topside”, “vertical” and “horizontal” and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms. These terms when used in reference to the filter and the patient interface throughout the specification, including the claims, refer to orientations relative to the normal operating orientation, i.e., when the interface is fitted to a patient and the patient’s head is upright. An example of the “upright orientation” of a patient interface and the filter is shown in Figure 10.

[0230] Throughout the description and claims, terms such as “join”, “link” and “connection” should not be construed as requiring two separate components being linked together. Those terms should be interpreted in context, including the option of meaning an intersection of integrally formed features.

[0231] Furthermore, invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Also, the various embodiments described above may be implemented in conjunction with other embodiments, for example, aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, eachindependent feature or component of any given assembly may constitute an additional embodiment.

Claims

CLAIMS1 . A filter configured for use with a patient interface for providing positive pressure respiratory therapy to a patient, the filter comprising: a filter body comprising a filter inlet, a filter outlet and a sealed passageway between the filter inlet and the filter outlet, a filter element in fluid communication with the filter outlet, a sealing element surrounding the filter inlet, wherein the sealing element is configured to form a seal surrounding the outlet of a patient interface when the filter is coupled to a patient interface, and wherein the filter inlet is configured to receive gases from an outlet of a patient interface to allow the gases to flow through the sealed passageway to the filter outlet.

2. The filter according to claim 1 , wherein an opening area of the filter inlet is smaller than an opening area of the filter outlet.

3. The filter according to claim 2, wherein a ratio between the opening area of the filter inlet and the opening area of the filter outlet is between 0.1 :1 to 0.5:1 .

4. The filter according to any one of claims 1 to 3, wherein the filter inlet opening is an elongate shaped opening or a substantially oval shaped opening.

5. The filter according to any one of claims 1 to 4, wherein a distance from the filter inlet to the filter outlet taken through the passageway is between 1 mm to 15 mm.

6. The filter according to any one of claims 5, wherein the distance from the filter inlet to the filter outlet taken through the passageway is greater than 7 mm.

7. The filter according to any one of claims 1 to 6, wherein the sealed passageway of the filter body undergoes a change in geometry such that gases entering the filter inlet decrease in pressure before passing through the filter outlet and the filter element.

8. The filter according to claim 7, wherein the change in geometry comprises a change in cross-sectional area of the sealed passageway having regard to a crosssection perpendicular to a direction of gas flow through the sealed passageway.

9. The filter according to any one of claims 1 to 8, wherein the filter body is substantially curved in a top-down view to follow the curvature of the patient interface.

10. The filter according to any one of claims 1 to 9, wherein the filter body comprises a protruding lip surrounding the filter inlet.11 . The filter according to claim 10, wherein the protruding lip comprises a varying width in a plane of the rear surface of the filter around a perimeter of the protruding lip.

12. The filter according to claim 11 , wherein the varying width of the protruding lip projecting from a rear surface of the filter is greater than 1mm.

13. The filter according to claim 12, wherein the varying width of the protruding lip projecting from a rear surface of the filter is less than 5mm.

14. The filter according to claim 13, wherein the varying width of the protruding lip projecting from a rear surface of the filter is not greater than about 2mm.

15. The filter according to any one of claims 10 to 14, wherein the sealing element is affixed to the protruding lip.

16. The filter according to any one of claims 1 to 15, wherein the filter element comprises a filter media.

17. The filter according to claim 16, wherein the filter media comprises a polypropylene and / or an acrylic material.

18. The filter according to any one of claims 16 to 17, wherein the filter element further comprises a filter frame.

19. The filter according to claim 18, wherein the filter frame is over-moulded to at least a portion of the perimeter of the filter media.

20. The filter according to any one of claims 16 to 19, wherein the filter comprises a cover configured to extend across a surface of the filter media.

21. The filter according to claim 20, wherein the cover is removably couplable to the filter frame.

22. The filter according to claim 20, wherein the cover is integrally formed with the filter frame.

23. The filter according to any one of claims 20 to 22, wherein the cover comprises a plurality of openings.

24. The filter according to claim 23, wherein the plurality of openings are arranged in a lattice formation.

25. The filter according to any one of claims 1 to 24, wherein the filter comprises a coupling mechanism configured to removably couple the filter to the patient interface.

26. The filter according to claim 25, wherein the coupling mechanism comprises at least one arm configured to removably couple with the patient interface.

27. The filter according to claim 26, wherein the at least one arm is connected to the filter body.

28. The filter according to claim 27, wherein the at least one arm comprises a first arm and a second arm and wherein the first arm is connected at a first side of the filter body via a first connection and the second arm is connected at a second side of the filter body via a second connection.

29. The filter according to claim 28, wherein the first arm and the second arm are formed as a unitary structure of the filter body.

30. The filter according to claim 28 or 29, wherein the first connection is a first hinge and the second connection is a second hinge.

31. The filter according to claim 30, wherein the first hinge is located substantially midway along the first arm and the second hinge is located substantially midway along the second arm.

32. The filter according to claim 30, wherein the first hinge is located at a distal end of the first arm and the second hinge is located at a distal end of the second arm.

33. The filter according to any one of claims 30 to 32, wherein there is a preformed angle between each of the filter body and the first arm, and the filter body and the second arm.

34. The filter according to claim 33, wherein the preformed angle is between about 5° and 135°.

35. The filter according to any one of claims 28 to 33, wherein the first arm and the second arm each comprises a finger grip.

36. The filter according to claim 35, wherein the finger grip comprises a roughened surface and / or protrusions.

37. The filter according to claim 28 to 36, wherein the filter body comprises a first stop configured to make contact with the first arm and a second stop configure to make contact with the second arm, the first stop and the second stop configured to limit movement of the first arm and the second arm respectively.

38. The filter according to any one of claims 1 to 37, wherein the filter comprises a recess configured to provide clearance for an inlet elbow of the patient interface.

39. A system comprising the filter of any one of claims 25 to 38 and a patient interface, wherein the patient interface comprises a cushion module and a frame configured to couple with the cushion module, the cushion module further comprises a seal configured to form a seal with a patient’s face surrounding an entrance to a nose and / or mouth of a user and a housing comprising the outlet, and wherein the coupling mechanism of the filter is configured to couple with the frame of the patient interface, such that when the frame is coupled to the cushion module the filter is located in abutment with the housing, and such that the sealing element of the filter forms a seal with the housing surrounding the outlet.

40. The system of claim 39, wherein the first arm of the coupling mechanism comprises a first protrusion, the second arm of the coupling mechanism comprises a second protrusion, the frame comprises a first aperture and a second aperture, and wherein the first protrusion and the second protrusion are configured to engage the first aperture and the second aperture respectively to couple the filter to the frame.

41. The system of claim 39, wherein the first arm of the coupling mechanism comprises a first aperture, the second arm of the coupling mechanism comprises a second aperture, the frame comprises a first protrusion and a second protrusion,and wherein the first protrusion and second protrusion are configured to engage the first aperture and the second aperture respectively to couple the filter to the frame.

42. A filter configured for use with a patient interface for providing positive pressure respiratory therapy to a patient, the filter comprising: a filter body comprising a filter inlet, a filter outlet, and a sealed passageway; a filter element in fluid communication with the filter outlet; wherein the filter inlet is configured to receive gases from an outlet of the patient interface and to convey the gases flow through the sealed passageway to the filter outlet and wherein the filter element is in fluid communication with the filter outlet such that substantially all gas exiting the filter outlet flows through the filter element to external of the filter; and wherein an opening area of the filter inlet is smaller than an opening area of the filter outlet.

43. The filter according to claim 42, wherein the filter comprises a sealing element surrounding the filter inlet, the sealing element configured to form a seal surrounding the outlet of the patient interface when the filter is coupled with the patient interface.

44. The filter according to any one of claims 42 to claim 43, wherein a ratio between the opening area of the filter inlet and the opening area of the filter outlet is between 0.1 :1 to 0.5:1.

45. The filter according to any one of claims 42 to 44, wherein the filter inlet opening is an elongate shaped opening or a substantially oval shaped opening.

46. The filter according to any one of claims 42 to 45, wherein a distance from the filter inlet to the filter outlet is between 1 mm to 15 mm.

47. The filter according to claim 46, wherein the distance from the filter inlet to the filter outlet is greater than 7mm.

48. The filter according to any one of claims 42 to 47, wherein the sealed passageway of the filter body undergoes a change in geometry such that gases entering the filter inlet decrease in pressure before passing through the filter outlet and the filter element.

49. The filter according to claim 48, wherein the change in geometry comprises a change in cross-sectional area of the sealed passageway when a cross-section is taken perpendicular to the direction of gas flow through the sealed passageway.

50. The filter according to any one of claims 42 to 49, wherein the filter body is substantially curved in a top-down view such that it is configured to follow the curvature of the patient interface.

51. The filter according to any one of claims 42 to 50, wherein the filter body comprises a protruding lip around the perimeter of the filter inlet.

52. The filter according to claim 51 , wherein the protruding lip comprises a varying width in a plane of the rear surface of the filter around a perimeter of the protruding lip.

53. The filter according to claim 52, wherein the varying width of the protruding lip projecting from a rear surface of the filter is greater than 1mm.

54. The filter according to claim 53, wherein the varying width of the protruding lip projecting from a rear surface of the filter is less than 5mm.

55. The filter according to claim 54, wherein the varying width of the protruding lip projecting from a rear surface of the filter is not greater than 2mm.

56. The filter according to any one of claims 51 to 55, wherein the sealing element is affixed to the protruding lip.

57. The filter according to any one of claims 42 to 56, wherein the filter element comprises a filter media.

58. The filter according to claim 57, wherein the filter media comprises a polypropylene and / or an acrylic material.

59. The filter according to any one of claims 57 to 58, wherein the filter element further comprises a filter frame.

60. The filter according to claim 59, wherein the filter frame is overmoulded to at least a portion of the perimeter of the filter media.

61. The filter according to any one of claims 57 to 60, wherein the filter comprises a cover configured to extend across a surface of the filter media.

62. The filter according to claim 61 , wherein the cover is removably couplable to the filter frame.

63. The filter according to claim 61 , wherein the cover is integrally formed with the filter frame.

64. The filter according to any one of claims 61 to 63, wherein the cover comprises a plurality of openings.

65. The filter according to claim 64, wherein the plurality of openings are arranged in a lattice formation.

66. The filter according to any one of claims 42 to 65, wherein the filter comprises a coupling mechanism configured to removably couple the filter to the patient interface.

67. The filter according to claim 66, wherein the coupling mechanism comprises at least one arm configured to removably couple with the patient interface.

68. The filter according to claim 67, wherein the at least one arm is connected to the filter body.

69. The filter according to claim 67 to 68, wherein the at least one arm comprises a first arm and a arm and wherein the first arm is connected at a first side of the filter body via a first connection and the second arm is connected at a second side of the filter body via a second connection.

70. The filter according to claim 69, wherein the first arm and the second arm are formed as a unitary structure of the filter body.

71. The filter according to claim 69 to 70, wherein the first connection is a first hinge and the second connection is a second hinge.

72. The filter according to claim 71 , wherein the first hinge is located substantially midway along the first arm and the second hinge is located substantially midway along the second arm.

73. The filter according to claim 71 , wherein the first hinge is located at a distal end of the first arm and the second hinge is located at a distal end of the second arm.

74. The filter according to any one of claims 69 to 73, wherein there is a preformed angle between each of the first hinge and the first arm, and the second hinge and the second arm.

75. The filter according to claim 74, wherein the preformed angle is between about 20° and 135°.

76. The filter according to any one of claims 69 to 75, wherein the first arm and the second arm each comprises a finger grip.

77. The filter according to claim 76, wherein the finger grip comprises a roughened surface and / or protrusions.

78. The filter according to claim 69 to 77, wherein the filter body comprises a first stop configured to make contact with the arm and a second stop configure to make contact with the second arm, the first stop and the second stop configured to limit movement of the first arm and the second arm, respectively.

79. The filter according to any one of claims 42 to 78, wherein the filter comprises a recess configured to provide clearance for an inlet elbow of the patient interface.

80. An assembly comprising the filter of any one of claims 66 to 79 and a patient interface, wherein the patient interface comprises a cushion module and a frame configured to couple with the cushion module, the cushion module comprising a seal configured to form a seal with a patient’s face surrounding an entrance to a nose and / or mouth of a user, and a housing comprising the outlet; and wherein the coupling mechanism of the filter is configured to couple with the frame of the patient interface such that when the frame is coupled to the cushion module the filter is held against the housing by its connection with the frame and the sealing element of the filter forms a seal with the housing at least partially surrounding the outlet.

81. The system of claim 80, wherein the first arm of the coupling mechanism comprises a first protrusion, the second arm of the coupling mechanism comprises a second protrusion, the frame comprises a first aperture and a second aperture, and wherein the first protrusion and second protrusion are configured to engage the first aperture and the second aperture, respectively to couple the filter to the frame.

82. The system of claim 80, wherein the first arm of the coupling mechanism comprises a first aperture, the second arm of the coupling mechanism comprises a second aperture, the frame comprises a first aperture and a second aperture, andwherein the first protrusion and second protrusion are configured to engage the first aperture and the second aperture respectively to couple the filter to the frame.

83. A patient interface assembly for providing positive pressure respiratory therapy to a patient, the patient interface assembly comprising: a cushion module comprising a seal and a housing which together define a cavity for receiving pressurised gasses; the housing comprising a gas inlet configured to receive supply of pressurised gasses and a gas outlet configured to exhaust gasses from within the cavity; the seal comprising a seal opening configured to seal with the mouth and / or nose of a patient to deliver pressurised gasses from within the cavity to the patient; a frame coupled to the cushion module; and a filter for coupling with the frame and engaging with a portion of the housing when the frame is removably coupled to the cushion module; the filter comprising a filter body, a filter inlet, a filter outlet, and a sealed passageway formed between the filter inlet and the filter outlet; a filter element positioned adjacent to or near the filter outlet; wherein the filter inlet is configured to receive gases from the gas outlet and wherein the filter element is in fluid communication with the filter outlet such that substantially all gas exiting the filter outlet flows through the filter element to atmosphere, and the filter further comprising a sealing element surrounding the filter inlet, the sealing element configured to form a seal surrounding the outlet of the cushion module when the filter is coupled with the frame.

84. The patient interface assembly of claim 83, wherein an opening area of the filter inlet is smaller than an opening area of the filter outlet.

85. The patient interface assembly of any one of claims 83 to 84, wherein the seal opening comprises an oral opening to communicate gas with the mouth of the patient and a nasal opening to communicate gas with the nose of the patient; and the cavity of the cushion module comprises a first chamber and a second chamber; andthe oral opening is in fluid communication with the first chamber and the nasal opening is in fluid communication with the second chamber; and a dividing wall that separates the first chamber from the second chamber; and one or more flow directors which enable gas to flow into the second chamber from the first chamber through the dividing wall; and wherein the gas inlet is in fluid communication with the first chamber and the gas outlet is in fluid communication with the second chamber.

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