WO2013108145A1 - Cushion with venting support for use with patient interface device - Google Patents

Abstract

A cushion (16) for a patient interface device (10) comprises a first end portion, a second end portion (24) disposed opposite the first end portion, and a passage (26) formed therethrough. The second portion comprises a sealing portion (28) having a first side (28a) and an opposite second side (28b). The first side sealingly engages a portion of a user's face. The second portion further comprises a support portion (30) disposed adjacent the sealing portion. The support portion engages the opposite second side of the sealing portion and defines, at least in part, the passage when the patient interface device is disposed on the user. A cavity (32) is formed between the sealing portion and the support portion when the patient interface device is disposed on the user and the support portion comprises a venting structure (34) adapted to vent gas between the passage and the cavity.

Description

CUSHION WITH VENTING SUPPORT FOR USE

WITH PATIENT INTERFACE DEVICE

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the priority benefit under 35 U.S.C. § 1 19(e) of U.S. Provisional Application No. 61/587,141 filed on January 17, 2012, the contents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1 . Field of the Invention

The present invention generally relates to cushions for use on patient interface devices in pressure support systems that supply a flow of gas to the airway of a patient, and, more particularly, to a cushion that includes a venting support portion. The invention further relates to patient interface devices that includes such cushions.

2. Description of the Related Art

There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non- invasive ventilation (NIV). It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient's respiratory cycle, to treat a medical disorder, such as sleep apnea syndrome, in particular, obstructive sleep apnea (OSA), chronic obstructive pulmonary disease (COPD), or congestive heart failure (CHF).

Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device, which is typically a nasal or nasal/oral mask, on the face of a patient to interface the ventilator or pressure support system with the airway of the patient so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient.

Typically, patient interface devices include a mask shell having a cushion attached to the shell that contacts the surface of the patient. The mask shell and cushion are held in place by a headgear that wraps around the head of the patient. The mask and headgear form the patient interface assembly. A typical headgear includes flexible, adjustable straps that extend from the mask to attach the mask to the patient.

Because such masks are typically worn for an extended period of time, a variety of concerns must be taken into consideration. For example, in providing CPAP to treat OSA, the patient normally wears the patient interface device all night long while he or she sleeps. One concern in such a situation is that the patient interface device is as comfortable as possible, otherwise the patient may avoid wearing the interface device, defeating the purpose of the prescribed pressure support therapy. It is also important that the interface device provide a tight enough seal against a patient's face without discomfort.

In order to address such comfort and sealing issues, many cushions employ a double flap structure which includes a support element and a sealing element. FIGS. 1 and 2 show cross-sectional views of examples of such prior approaches. More particularly, example A of FIG. 1 shows a cross-sectional view of a portion of a cushion 2 that includes an inner support portion 4 and an outer sealing flap 6 that both generally extend from a wall portion (not numbered), while example B of FIG. 1 shows a cross- sectional view of a portion of a cushion 2' that includes an inner support portion 4' and an outer sealing flap 6' that are generally separate elements. As shown in FIG. 2, when either cushion 2 or 2' is compressed against the face of a user, shown generally at 8, sealing flap 6 or 6' generally collapses against support portion 4 or 4', typically creating an air filled gap or cavity 9 between the support portion 4, 4' and the sealing flap 6, 6' which tends to act as a buffer between the user and the support element. However, the effectiveness of such an air- filled cavity is often diminished when the sealing element contacts the support element as a virtual seal between the two elements is often created which tends to prohibit air from entering or exiting cavity 9, thus causing support portion 4,4' and sealing flap 6, 6' to act generally as a single element, reducing comfort and sealing ability. Such effect commonly becomes even more prominent when a mask is over-tightened on a user, a common occurrence in attempting to compensate for a poor seal. Accordingly, a need exists for a patient interface device that improves upon existing devices, for example, to maximize patient comfort while minimizing leak, during delivery of a positive airway pressure or flow of gas to the airway of the user.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide improved cushion assemblies and patient interface devices utilizing such cushion assemblies that overcome deficiencies in the known art.

As one aspect of the invention a cushion for use in a patient interface device for delivering a flow of gas to the airway of a user is provided. The cushion comprises a first end portion adapted to be coupled to a mask shell, a second end portion disposed opposite the first end portion, and a passage formed therethrough passing between the first end and the second end portion. The passage is adapted to conduct the flow of gas therethrough to the airway of the user when the patient interface device is disposed on the head of the user. The second end portion comprises a sealing portion having a first side and an opposite second side. The first side is adapted to sealingly engage a portion of a user's face when the patient interface device is disposed on the head of a user. The second end portion further comprises a support portion disposed adjacent the sealing portion, the support portion being adapted to engage the opposite second side of the sealing portion and define, at least in part, the passage when the patient interface device is disposed on the head of a user. A cavity is formed between the sealing portion and the support portion when the patient interface device is disposed on the head of the user. The support portion comprises a venting structure adapted to vent gas between the passage and the cavity.

The venting structure may comprise an aperture formed through the support portion. In addition, the venting structure may comprise a number of channels disposed in a portion of the support portion. The venting structure may further comprise an uneven surface treatment on a portion of the support portion adapted to engage the sealing portion. As another aspect of the invention, a cushion assembly for use with a mask in a patient interface device for delivering a flow of breathing gas to an airway of a patient is provided. The cushion assembly comprises an outer sealing member having a first end portion adapted to be coupled to a mask and an opposite second end portion having an outer surface adapted to sealingly engage a face of a patient and an inner surface disposed opposite the outer surface. The cushion assembly further comprises an inner support member formed separately from the outer sealing member, the inner support member having one or more venting structures for preventing entrapment of air between the outer sealing member and the support member. The support member is adapted to engage the inner surface of the second end portion of the sealing member when the cushion assembly is compressed on the face of a patient.

The support portion may comprise a body portion having a number of apertures disposed therein. The support member may be formed as a ring-like structure. The support member may comprise a plurality of separate support members. The inner support member may include an adhesive portion adapted to couple the inner support member to at least one of the outer sealing member or a mask to which the sealing member is coupled. The support member may comprise a base portion having a number of support portions extending therefrom. The support portions may comprise a plurality of finger-like projections which extend generally perpendicular from the base portion toward the inner surface of the opposite second end portion of the sealing member. The support portion may comprise a plurality of separate support members.

As yet another aspect of the invention, a patient interface device for delivering a flow of gas to a patient is provided. The patient interface device comprises a mask shell and a cushion. The cushion comprises a first end portion coupled to the mask shell, a second end portion disposed opposite the first end portion, and a passage formed therethrough passing between the first end portion and the second end portion. The passage is adapted to conduct the flow of gas therethrough to the airway of the user when the patient interface device is disposed on the head of the user. The second portion comprises a sealing portion having a first side and an opposite second side, the first side being adapted to sealingly engage a portion of a user's face when the patient interface device is disposed on the head of a user. The second portion further comprises a support portion disposed adjacent the sealing portion, the support portion being adapted to engage the opposite second side of the sealing portion and define, at least in part, the passage when the patient interface device is disposed on the head of a user. The sealing portion and the support portion for a cavity therebetween when the patient interface device is disposed on the head of the user. The support portion comprises a venting structure adapted to vent gas between the passage and the cavity.

These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are cross-sectional views of prior art cushion designs;

FIG. 3 is a front isometric view of an example embodiment of a patient interface device according to the principles of the present invention shown (schematically) connected to a gas flow/pressure generating system to form a patient interface system;

FIG. 4 is a rear isometric view of the patient interface device of FIG. 3;

FIGS. 5 A, 5B and 5C, respectively, are cross-section views of a portion of the cushion of the patient interface device of FIGS. 3 and 4 taken along line 5-5 of FIG. 4 shown in a relaxed (FIG. 5A) and compressed (against a user) state (FIGS. 5B and 5C);

FIG. 6A is a cross-sectional view of a portion of another example embodiment of a cushion according to the principles of the present invention;

FIG. 6B is a cross-sectional view of the portion of FIG. 6A taken along line B-B of FIG. 6A; FIG. 7A is a cross-sectional view of a portion of a further example embodiment of a cushion according to the principles of the present invention;

FIG. 7B is a cross-sectional view of the portion of FIG. 7A taken along line B-B of FIG. 7 A;

FIG. 8 A is a partial cross-sectional view of an embodiment of a cushion assembly according to the principles of the present invention;

FIG. 8B is an elevational view of a portion of the support member of the cushion assembly of FIG. 8A;

FIG. 8C is a top view of the support member of the cushion assembly of

FIG. 8A;

FIG. 9A is a partial cross-sectional view of another embodiment of a cushion assembly according to the principles of the present invention; and

FIG. 9B is an isometric view of a portion of the support member of the cushion assembly of FIG. 9A.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

As used herein, the singular form of "a", "an", and "the" include plural references unless the context clearly dictates otherwise. As used herein, the statement that two or more parts or components are "coupled" shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, "directly coupled" means that two elements are directly in contact with each other. As used herein, "fixedly coupled" or "fixed" means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other.

As used herein, the word "unitary" means a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a "unitary" component or body. As employed herein, the statement that two or more parts or components "engage" one another shall mean that the parts exert a force against one another either directly or through one or more intermediate parts or components. As employed herein, the term "number" shall mean one or an integer greater than one (i.e., a plurality) and the singular form of "a", "an", and "the" include plural referents unless the context clearly indicates otherwise.

Directional phrases used herein, such as, for example and without limitation, top, bottom, left, right, upper, lower, front, back, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.

FIGS. 3, 4, 5A and 5B illustrate an exemplary embodiment of a patient interface device 10 and components thereof according to the principles of the present invention. Patient interface device 10 communicates a flow of breathing gas between the patient's airway and a pressure/flow generating system 12 (shown schematically), such as a ventilator, CPAP device, or variable pressure device, e.g., a BiPAP^® device manufactured and distributed by Philips Respironics, Inc. of Pittsburgh, Pa., or an auto-titration pressure support system.

A BiPAP device is a bi-level device in which the pressure provided to the patient varies with the patient's respiratory cycle, so that a higher pressure is delivered during inspiration than during expiration. An auto-titration pressure support system is a system in which the pressure varies with the condition of the patient, such as whether the patient is snoring or experiencing an apnea or hypopnea. For present purposes, pressure/flow generating system 12 is also referred to as a gas flow generating device, because flow results when a pressure gradient is generated. The present invention contemplates that pressure/flow generating system 12 is any conventional system for delivering a flow of gas to an airway of a patient or for elevating a pressure of gas at an airway of the patient, including the pressure support systems summarized above and noninvasive ventilation systems.

Communicating a flow of breathing gas between the patient's airway and pressure/flow generating system 12 includes delivering a flow of breathing gas to the patient from the pressure/flow generating device and exhausting a flow of gas from the patient to ambient atmosphere. Referring to FIG. 3, the system for delivering a breathing gas to a patient according to the present invention comprises pressure/flow generating system 12 that produces a flow of gas, and a conduit 14, which is also referred to as a patient circuit, having a first end portion (not numbered) operatively coupled to the gas flow generating device and a second end portion (not numbered). Conduit 14 carries the flow of gas from pressure/flow generating device 12 during operation of the system to patient interface device 10, which is coupled to the second end portion of conduit 14. Conduit 14 corresponds to any conduit suitable for communicating the flow of gas form the pressure/flow generating system to the patient interface device. An example of a typical conduit is a flexible tube. A headgear assembly, which is not shown in the figures, attaches patient interface device 10 to the patient's head.

Patient interface device 10 includes a cushion 16 and a mask shell 18 having a patient side and opposite thereto, an outer side. Attached to outer side of mask shell 18 is a conduit coupling member (not numbered) that couples mask shell 18 to conduit 14 so that a flow of gas is communicated to the interior of the patient interface device for subsequent delivery to the patient. Conversely, gas from the patient is communicated from the patient interface device into conduit 14, where an exhaust port is located. In an exemplary embodiment, mask shell 18 is formed as a generally rigid shell formed from rigid plastic, such as polycarbonate. It is to be understood that the present invention contemplates that one or more of the size, shape, or composition of mask shell 18 may be varied without varying from the scope of the present invention.

In the illustrated embodiment of FIGS. 3 and 4, mask shell 18 has a generally rounded triangular shape and is provided with upper and lower headgear attaching elements 20, 22, which cooperate with corresponding attachment elements on headgear straps (not illustrated) for securely mounting patient interface device 10 on the head of a user. It is to be understood, however, that the present invention contemplates using any conventional connection assembly to attach a headgear or headgear strap to mask shell 18 or other suitable shell arrangement. It is to be further understood that the present invention also contemplates that mask shell 18 may further include a forehead support portion having headgear attaching elements for connection to further headgear straps. The present invention also contemplates providing a post or other protrusion at the upper portion of the shell, i.e., the portion overlying the bridge of the nose, to which the headgear can be attached.

The present invention contemplates that the headgear suitable for use with patient interface device 10 is any conventional headgear used in the patient interface field. For example, without limitation, a typical headgear assembly comprises a headpiece that overlies a portion of the patient's crania and with headgear straps extending therefrom to adjustably connect the headgear to the mask.

In an exemplary embodiment, cushion 16 is formed of a soft, cushiony, elastomeric material, such as silicone, appropriately soft thermoplastic elastomers, closed cell foam, thin materials, or any combination of suitable materials and includes a first end portion (not numbered) adapted to be coupled to a mask (such as mask shell 18 of FIGS. 3 and 4), an opposite second end portion 24, and a passage 26 formed therethrough extending between the first end portion and second end portion 24. Passage 26 is adapted to conduct the flow of gas generated by pressure/flow generating device 12 (and passed through conduit 14) therethrough to the airway of the user when patient interface device 10 is disposed on the head of the user.

Referring to the cross-sectional views of FIGS. 5A and 5B, second end portion 24 of cushion 16 includes a sealing portion 28, shown as a sealing flap having a first side 28a and an opposite second side 28b. As shown in FIG. 5B, first side 28a is adapted to sealingly engage a portion (not numbered) of a user's face when patient interface device 10, and thus cushion 16, is disposed on the head of a user. Continuing to refer to FIGS. 5A and 5B, second end portion 24 further includes an inner support portion 30 disposed adjacent sealing portion 28 and which generally defines at least a portion of passage 26. As shown in FIG. 5B, support portion 30 is adapted to engage opposite second side 28b of sealing portion 28 when patient interface device 10, and thus cushion 16, is disposed on, and generally compressed against a portion of, the head of a user. When in such engaged position such as shown in FIG. 5B, a cavity 32 is formed between sealing portion 28 and support portion 30. In order to promote the flow of gas into and/or from cavity 32, and thus prevent the undesirable trapping of air within cavity 32, support portion 30 includes a venting structure, such as an aperture 34, which is positioned in a manner that allows passage of air or other gas between passage 26 and cavity 32 when cushion 16 is compressed against the face of a user, such as shown in FIGS. 5B and 5C. As shown by the arrows in FIG. 5C, by providing a venting structure (e.g., aperture 34) between passage 26 and cavity 32, the pressurized flow of gas passing through passage 26 can effectively produce an air curtain effect within cavity 32 on sealing portion 28 which acts to enhance the seal between sealing portion 28 and the user's face by generally pressing sealing portion 28 outward toward the user. It is to be appreciated that by enhancing the sealing effect of sealing portion 28, generally less strapping force is required in order to effectively seal patient interface device 10. By reducing the strapping forces needed to produce an adequate seal, the overall comfort of patient interface 10 on the head of a user is improved.

FIGS. 6A and 6B, as well as FIGS. 7A and 7B, show cross-sectional views of portions of further example embodiments of cushions 16' and 16" in accordance with the principles of the present invention. In the example embodiment of FIGS. 6A and 6B, support portion 30' includes a venting structure 34' formed from a number of channels 36 disposed in the portion (not numbered) of support portion 30' that engages sealing portion 28 when the patient interface device on which cushion 16' is coupled is disposed on the head of a user.

In the example embodiment of FIGS. 7A and 7B, support portion 30" includes a venting structure 34" formed from a number of micro -channels or other suitable generally uneven surface treatment on the portion (not numbered) of support portion 30" that engages sealing portion 28 when the patient interface device on which cushion 16" is coupled is disposed on the head of a user.

FIGS. 8A-8C show an example embodiment of a cushion assembly 40 and components thereof according to the principles of the present invention. Referring to FIG. 8A, which shows a cross-sectional view of a portion of the cushion assembly 40 similar to those shown in FIGS. 5 A and 5B, cushion assembly 40 includes an outer sealing member 42 and an inner support member 44, formed separately from sealing portion 42. In an exemplary embodiment, sealing portion 42 is formed of a soft, cushiony, elastomeric material, such as silicone, appropriately soft thermoplastic elastomers, closed cell foam, thin materials, or any combination of suitable materials and includes a first end portion 46 adapted to be coupled to a mask (such as mask shell 18 of FIGS. 3 and 4), and an opposite second end portion 48 having an outer surface 48a adapted to sealingly engage the face of a user and an inner surface 48b disposed opposite the outer surface 48a.

Sealing portion 42 further includes a passage, shown generally at 50, formed therethrough extending between first end portion 46 and second end portion 48. Passage 50 is adapted to conduct the flow of gas generated by a pressure/flow generating device and passed through a conduit therethrough to the airway of the user when the patient interface device on which cushion assembly 40 is coupled is disposed on the head of a user.

Referring to FIGS. 8B and 8C, support portion 44 includes a body portion 52 formed from an elastic or other suitable semi-elastic material having a number of apertures 54 disposed therein. In use, support portion 44 is structured to function in a similar manner as support portions 30, 30' and 30" previously discussed by engaging inner surface 48b of second end portion 48 of sealing portion 42 when sealing portion 42 is disposed on and compressed against the face of a user. It is to be understood that by including one or more apertures 54 or other suitable venting structures, formation of sealed cavities between support portion 44 and sealing portion 42, and thus entrapment of air between sealing portion 42 and support portion 44 is avoided. It is also to be understood that by being formed as a separate member from sealing portion 42, support portion 44 may be retrofit to cushions in order to provide or bolster support as needed. Accordingly, it is further to be understood that support portion 44 may be formed as a single member, such as shown in the example of FIG. 8C, or may be formed as a number of smaller members which may be selectively placed in desired locations.

FIGS. 9A-9B show a further example embodiment of a cushion assembly 60 and components thereof according to the principles of the present invention. Referring to FIG. 9A, which shows a cross-sectional view of a portion of the cushion assembly 60 similar to those shown in FIGS. 5 A and 5B, cushion assembly 60 includes an outer sealing member 62 and an inner support member 64, formed separately from sealing portion 62. In an exemplary embodiment, sealing portion 62 is formed of a soft, cushiony, elastomeric material, such as silicone, appropriately soft thermoplastic elastomers, closed cell foam, thin materials, or any combination of suitable materials and includes a first end portion 66 adapted to be coupled to a mask (such as mask shell 18 of FIGS. 3 and 4) and an opposite second end portion 68 having an outer surface 68a adapted to sealingly engage the face of a user and an inner surface 68b disposed opposite the outer surface 68a. Sealing portion 62 further includes a passage, shown generally at 70, formed therethrough extending between first end portion 66 and second end portion 68. Passage 70 is adapted to conduct the flow of gas generated by a pressure/flow generating device and passed through a conduit therethrough to the airway of the user when the patient interface device on which cushion assembly 60 is coupled is disposed on the head of a user.

Referring to FIG. 9B, support portion 64 includes a base portion 72 having a number of support members 74 extending therefrom. In the exemplary embodiment shown in FIGS. 9A and 9B, support members 74 are formed as a plurality of finger-like projections which extend generally perpendicularly from base portion 72 toward inner surface 68b of second end portion 68 of sealing portion 62. However, it is to be understood that support members of other suitable shapes may be employed without varying from the scope of the present invention.

In use, support portion 64 is structured to function in a similar manner as support portions 30, 30', 30" and 44 as previously discussed by engaging inner surface 68b of second end portion 68 when sealing portion 62 is disposed on and compressed against the face of a user. It is to be understood that by providing support via a number of spaced support members 74, formation of sealed cavities between support portion 64 and sealing portion 62, and thus entrapment of air between sealing portion 62 and support portion 64 is avoided. It is also to be understood that by being formed as a separate member from sealing portion 62, support portion 64 may be retrofit to cushions in order to provide or bolster support as needed. Accordingly, it is further to be understood that support portion 64 may be formed as a single member or may be formed as a number of smaller members which may be selectively placed in desired locations.

It is to be appreciated that the present invention contemplates various retention means that may be employed in order to retain support portions, such as support portions 44 or 64, within the respective sealing portions 42 and 62. For example, support portions 44 or 64 may be formed in a manner that, due to their shape, tend to be retained within a sealing portion. The circular arrangement of FIG. 8C shows an example of a support member formed in a manner that would tend to be retained within a sealing portion without any additional retention means. Examples of other retention means that may be employed include, without limitation, adhesives, velcro, or other suitable means, that may be employed to secure support portions 44 or 64 to one or both of sealing portions 42 or 62 or the mask to which such portions are coupled.

It is to be understood that the present invention contemplates that one or more of the size, shape, or quantity of venting structures employed on or within the support portions or members described herein may be varied without varying from the scope of the present invention. Accordingly, it is to be appreciated that instead of, or in addition to, selected portions as described herein, the entire support portion or support member may be formed from a suitable porous material which naturally allows air flow therethrough to provide the ballooning effects as described herein.

It is to be appreciated that the present invention is not intended to be limited to the mask or cushion shapes described herein but instead may be employed with masks and cushion of various other shapes or designs. In addition, the various structures described herein can be used alone or in combination to the extent possible.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" or "including" does not exclude the presence of elements or steps other than those listed in a claim. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination.

Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.

Claims

What is Claimed is:

1. A cushion (16, 16', 16") for use in a patient interface device (10) for delivering a flow of gas to the airway of a user, the cushion comprising:

a first end portion adapted to be coupled to a mask shell; a second end portion (24, 24', 24") disposed opposite the first end portion; and

a passage (26) formed therethrough passing between the first end portion and the second end portion, the passage being adapted to conduct the flow of gas therethrough to the airway of the user when the patient interface device is disposed on the head of the user,

wherein the second portion comprises:

a sealing portion (28) having a first side (28a) and an opposite second side (28b), the first side adapted to sealingly engage a portion of a user's face when the patient interface device is disposed on the head of a user; and

a support portion (30, 30', 30") disposed adjacent the sealing portion, the support portion adapted to engage the opposite second side of the sealing portion and define, at least in part, the passage when the patient interface device is disposed on the head of a user,

wherein a cavity (32) is formed between the sealing portion and the support portion when the patient interface device is disposed on the head of the user, and wherein the support portion comprises a venting structure (34, 34', 34") adapted to vent gas between the passage and the cavity.

2. The cushion of claim 1, wherein the venting structure comprises an aperture (34) formed through the support portion.

3. The cushion of claim 1, wherein the venting structure comprises a number of channels (36) disposed in a portion of the support portion.

4. The cushion of claim 1, wherein the venting structure comprises an uneven surface treatment on a portion of the support portion adapted to engage the sealing portion.

5. A cushion assembly (40, 60) for use with a mask in a patient interface device for delivering a flow of breathing gas to an airway of a patient, the cushion assembly comprising:

an outer sealing member (42, 62) having a first end portion (46, 66) adapted to be coupled to a mask and an opposite second end portion (48, 68) having an outer surface (48a, 68a) adapted to sealingly engage a face of a patient and an inner surface (48b, 68b) disposed opposite the outer surface; and

an inner support member (44, 64) formed separately from the outer sealing member, the inner support member having one or more venting structures for preventing entrapment of air between the outer sealing member and the support member, wherein the support member is adapted to engage the inner surface of the second end portion of the sealing member when the cushion assembly is compressed on the face of a patient.

6. The cushion assembly of claim 5, wherein the support member comprises a body portion (52) having a number of apertures disposed therein.

7. The cushion assembly of claim 6, wherein the support member comprises a ring-like structure.

8. The cushion assembly of claim 6 wherein the support member comprises a plurality of separate support members.

9. The cushion assembly of claim 5, wherein the inner support member includes an adhesive portion adapted to couple the inner support member to at least one of the outer sealing member or a mask to which the outer sealing member is coupled.

10. The cushion assembly of claim 5, wherein the support member comprises a base portion (72) having a number of support portions (74) extending therefrom.

11. The cushion assembly of claim 10, wherein the support portions (74) comprise a plurality of finger-like projections which extend generally perpendicular from the base portion toward the inner surface of the opposite second end portion of the sealing member.

12. The cushion assembly of claim 10, wherein the support member comprises a plurality of separate support members.

13. A patient interface device (10) for delivering a flow of gas to a patient, the patient interface device comprising:

a mask shell (18); and

a cushion (16) comprising:

a first end portion coupled to the mask shell;

a second end portion (24, 24', 24") disposed opposite the first end portion; and

a passage (26) formed therethrough passing between the first end portion and the second end portion, the passage being adapted to conduct the flow of gas therethrough to the airway of the user when the patient interface device is disposed on the head of the user,

wherein the second portion comprises: a sealing portion (28) having a first side (28a) and an opposite second side (28b), the first side adapted to sealingly engage a portion of a user's face when the patient interface device is disposed on the head of a user; and a support portion (30, 30', 30") disposed adjacent the sealing portion, the support portion adapted to engage the opposite second side of the sealing portion and define, at least in part, the passage when the patient interface device is disposed on the head of a user,

wherein a cavity (32) is formed between the sealing portion and the support portion when the patient interface device is disposed on the head of the user, and wherein the support portion comprises a venting structure (34, 34', 34") adapted to vent gas between the passage and the cavity.