Patent Description:
The use of NPPV for treatment of SDB such as Obstructive Sleep Apnea (OSA) was pioneered by <CIT>). Apparatus for the treatment of SDB involves a blower which delivers a supply of air at positive pressure to a patient interface via a conduit. The patient interface may take several forms, such as a nasal mask assembly and a nasal and mouth mask assembly. Patients typically wear a mask assembly while sleeping to receive the NPPV therapy.

Mask assemblies typically comprise a rigid shell or frame and a soft face-contacting cushion. The cushion spaces the frame away from the patient's face. The frame and cushion define a cavity which receives the nose or nose and mouth. The frame and cushion are held in position on the patient's face by a headgear assembly. The headgear assembly typically comprises an arrangement of straps which pass along both sides of the patient's face to the back or crown of the patient's head.

<CIT>) describes a nasal mask assembly for Continuous Positive Airway Pressure (CPAP) having a ballooning/molding seal that conforms with the patient's nose and facial contours. The mask assembly has a face-contacting portion mounted to a shell which is sized and shaped to overfit the nose region of the patient. The face-contacting portion is in the form of a distendable membrane which is molded from an elastic plastic material. The distendable membrane and the shell together define a chamber. Pressurized gas admitted to the chamber causes the membrane to distend outwardly from the patient's face.

<CIT>) describes a nasal mask assembly and a mask cushion therefor.

The cushion comprises a substantially triangularly-shaped frame from which extends a membrane. The frame has an edge by which the cushion is affixed to a mask body. The membrane has an aperture into which the patient's nose is received. The membrane is spaced away from the rim of the frame, and its outer surface is of substantially the same shape as the rim.

The cushion of a patient interface can play a key role in the comfort and effectiveness of therapy. There is considerable variation in facial size and shape which can mean that a mask designed for one type of face may not be suitable for another. For example, an Asian-type nose tends to have a lower nasal bridge whereas a Caucasian-type nose has a higher nasal bridge. Using the wrong cushion can lead to excessive leak and discomfort. While creating customized cushions for every patient may solve some fitting issues, customized masks are very expensive. Thus, manufacturers seek to develop cushions which provide a comfortable and effective seal for a range of facial sizes and shapes.

<CIT> relates to respiratory mark assembly for delivering breathable gas to a patient includes a frame and a cushion, wherein the cushion has a non-face contacting portion structured to be connected to the frame, a face-contacting portion structured to engage the patient's face, and an intermediate portion that interconnects the non-face contacting portion and the face-contacting portion and the intermediate portion includes a gusset portion that applies a first component of force to the patient's face through the face-contacting portion. It is said that a spring structure is coupled with the face-contacting portion of the cushion, wherein the spring structure applies a second component of force to the patient's face through the face-contacting portion. Furthermore, it is said that the first and second components of force applied by the gusset portion and spring structure, respectively, determine a contact force of the cushion applied to the patient's face through the face-contacting portion and that the intermediate portion may also include an elastic cuff portion.

<CIT> relates to a cushion for a patient interface that includes an outer membrane providing a sealed structure adapted to form a seal with the patient's face in use and an underlying membrane generally spaced away from the outer membrane. It is said that the underlying membrane provides a support structure for the outer membrane and that the outer membrane and the underlying membrane each have an inner edge which defines an aperture to receive the patient's nose in use.

<CIT> relates to a respiratory mask assembly for delivering breathable gas to a patient includes a frame and a cushion, the cushion having a non-face contacting portion structured to be connected to the frame, a face-contacting portion structured to engage the patient's face, and a central portion that interconnects the non-face contacting portion and the face contacting portion.

<CIT> relates to a face mask having both inwardly and outwardly directed seals for engaging around the nose and mouth of a patient, so as to be effective for both positive and negative pressures.

<CIT> A relates to a seal and a mask having a seal adapted for confronting engagement with a surface of a user to form an interface therewith, wherein the seal includes a first portion defined by a gel substance and a second portion associated with the first portion.

SUMMARY OF THE INVENTION According to the invention, there is provided a cushion according to claim <NUM> and a patient interface according to claim <NUM>. The dependent claims <NUM>-<NUM> define embodiments of the invention. The following aspects of the disclosure may contain features appearing in embodiments of the invention as claimed even if they do not fall within the scope of the claims.

One aspect of the disclosure is to provide a patient interface having a cushion that provides more comfort to the patient while maintaining an effective seal.

Another aspect of the disclosure is to provide a comfortable cushion for a patient interface which fits a wide range of facial shapes and sizes.

Another aspect of the disclosure relates to a cushion including an underlying cushion and a membrane, wherein the underlying cushion and the membrane have a substantially flat portion in a nasal region of the cushion.

Another aspect of the disclosure relates to a cushion including a base wall, an underlying cushion and a membrane, wherein the base wall and underlying cushion have a cross-sectional configuration that provides a variable spring constant around the perimeter of the cushion.

Another aspect of the disclosure relates to a patient interface wherein the base wall and the frame connection of the cushion are internally offset with respect to the most external cushion point, e.g., external membrane surface.

Another aspect of the disclosure relates to a cushion including a base wall and underlying cushion that are inclined or angled in a side of nose region of the cushion.

Another aspect of the disclosure relates to a cushion having a substantially constant mouth width irrespective of its face height. Another aspect of the invention relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane includes nasal bridge, cheek, and chin regions adapted to form a continuous seal on nasal bridge, cheek, and chin regions of the patient's face, respectively. The nasal bridge region and adjacent two cheek regions define an intersection or apex. The membrane in the nasal bridge region has a height at the apex or intersection that is greater than a height in an adjacent portion of the cheek region.

Another aspect of the disclosure relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane is adapted to form a continuous seal on the patient's face. The underlying cushion has a spring-like connection with the base wall. The underlying cushion and/or base wall define a spring constant that varies along a length of the seal.

Another aspect of the disclosure relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane is adapted to form a continuous seal on the patient's face. One of the membrane and the underlying cushion includes an external surface that defines an outer width of the cushion, and the base wall is internally offset with respect to the external surface.

Yet another aspect of the disclosure relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane includes at least nasal bridge and side of nose regions adapted to form a continuous seal on nasal bridge and side of nose regions of the patient's face, respectively. The base wall and the underlying cushion in the side of nose region are inclined or angled with respect to a bottom of the frame.

Yet another aspect of the disclosure relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane includes nasal bridge, side of nose, upper cheek, lower cheek and chin regions adapted to form a continuous seal on nasal bridge, side of nose, upper cheek, lower cheek, and chin regions of the patient's face, respectively. An inner edge of the membrane defines an aperture that receives the patient's nose and mouth. A lower portion of the aperture that receives the patient's mouth has a mouth width that remains substantially constant irrespective of a face height of the cushion.

Yet another aspect of the disclosure inverrtterr relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane is adapted to form a continuous seal on the patient's face. At least a portion of the underlying cushion and/or base wall has a lower portion including a spring configuration that defines displacement of the cushion with respect to a force applied from the frame.

Still another aspect of the disclosure relates to a method of designing a series of mask assemblies. The method includes providing a first cushion adapted to fit a larger range of patients and providing a second cushion adapted to fit a smaller range of patients. Each of the first and second cushions includes an aperture that receives at least the patient's mouth. The aperture of the first and second cushions have the same width.

Still another aspect of the disclosure relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame; an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane includes at least a nasal bridge region adapted to form a continuous seal on a nasal bridge region of the patient's face. The membrane forms an elongated ridge in the nasal bridge region. The elongated ridge has sloping sides that meet to form an elongated crest. Each of the sloping sides is angled from a crest centerline in the range of <NUM>-<NUM>° and the crest has a radius of curvature in the range of <NUM>-<NUM>.

Still another aspect of the disclosure relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane includes at least a nasal bridge region adapted to form a continuous seal on a nasal bridge region of the patient's face. The nasal bridge region of the membrane includes a contoured portion that curves inwardly towards a cavity of the cushion along a radius to terminate at an inner edge of the membrane. The contoured portion has a free end that is angled with respect to a face contacting plane of the cushion in the range of <NUM>-<NUM>°.

Still another aspect of the disclosure relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane is adapted to form a continuous seal on the patient's face. The underlying cushion and/or base wall has a question-mark or sickle shape.

Still another aspect of the disclosure relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane is adapted to form a continuous seal on the patient's face. The underlying cushion has an arcuate configuration including an arc length greater than <NUM>.

Still another aspect of the disclosure relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient's face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane is adapted to form a continuous seal on the patient's face. The membrane includes a thickness that varies along a length of the seal.

Still another aspect of the disclosure relates to a cushion for a patient interface that delivers breathable gas to a patient. The cushion includes a base wall structured to be connected to a frame and a membrane adapted to form a continuous seal on the patient's face. At least a portion of the base wall includes a tapered portion that tapers towards the membrane.

Still another aspect of the disclosure relates to a mask system including a set of at least two cushions arranged to suit different face sizes, wherein the at least two cushions have substantially the same width.

Other aspects, features, and advantages of this disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of this disclosure.

The accompanying drawings facilitate an understanding of the various embodiments of this disclosure.

<FIG> illustrate a cushion <NUM> constructed according to an embodiment of the present disclosure. The cushion <NUM> is adapted to be removably or permanently connected (e.g., via mechanical and/or adhesive fastening) to a frame of a patient interface structured to deliver breathable gas to a patient. In an embodiment, the cushion <NUM> may be co-molded to a frame of a patient interface. In another embodiment, the cushion may form part of a frame with an outer support structure, e.g., ResMed's Hospital Nasal Mask. The cushion <NUM> provides a seal with the patient's face during use.

In the illustrated embodiment, the cushion <NUM> forms a part of a full-face mask. Specifically, the cushion <NUM> provides a seal around the patient's nose and mouth to enable the delivery of breathable gas to the patient's nose and mouth. However, aspects of the present disclosure may be applicable to other breathing arrangements, e.g., a nasal mask, a mouth mask, etc. The cushion <NUM> may be used with a gusset as described in <CIT>.

The cushion <NUM> is structured to provide a more comfortable fit for a wide range of facial shapes and sizes. Also, the cushion <NUM> is structured to provide a better seal and reduce the risk of leakage as discussed below.

As illustrated in <FIG>, the cushion <NUM> includes a non-face-contacting portion <NUM> structured to be connected to a frame of the patient interface, e.g., via a friction-fit, a tongue-and-groove arrangement, etc., and a face-contacting portion <NUM> structured to engage the patient's face.

As best shown in <FIG> and <FIG>, the face-contacting portion <NUM> of the cushion <NUM> preferably has a generally triangular shape and is structured to continuously contact nasal bridge, side of nose, upper cheek, lower cheek, and chin regions of the patient. However, the face-contacting portion <NUM> may have other suitable shapes, e.g., a generally trapezoidal shape. In the illustrated embodiment, as best shown in <FIG>, the cushion <NUM> includes a nasal bridge region <NUM> to provide a seal along the patient's nasal bridge, , a pair of cheek regions <NUM> to provide a seal along the patient's nose, cheek, and mouth, and a chin region <NUM> to provide a seal along the patient's chin. The pair of cheek regions <NUM> may be further defined as a pair of side of nose regions <NUM> to provide a seal along the sides of the patient's nose, a pair of upper cheek regions <NUM> to provide a seal along upper cheeks of the patient, and a pair of lower cheek regions <NUM> to provide a seal along the patient's lower cheeks and the sides of the patient's mouth.

The cushion <NUM> may be provided in various sizes in order to accommodate various facial sizes. For example, <FIG> illustrate embodiments of the cushion <NUM> in three other sizes. In an embodiment, the cushion <NUM> shown in <FIG> may represent a extra small size, the cushion <NUM> shown in <FIG> may represent a small size, the cushion <NUM> shown in <FIG> may represent a medium size, and the cushion <NUM> shown in <FIG> may represent a large size. As illustrated, the mouth width of the cushions <NUM>, <NUM>, <NUM>, <NUM> are substantially constant irrespective of their face height.

Specifically, the cushion <NUM> defines an aperture <NUM> that receives the patient's mouth. In a preferred embodiment, the lower portion of the aperture <NUM> has a constant width for all cushion sizes, e.g., <NUM>. However, the width of the lower portion of the aperture <NUM> may be almost constant, e.g., in a range of <NUM>, for all cushion sizes. For example, the width of the lower portion of the aperture <NUM> of the cushion <NUM> may be <NUM> ±<NUM>. In contrast, the width of the lower portion of the aperture <NUM> of a known cushion <NUM> commercially sold under the name of UltraMirage® Full Face by ResMed Ltd. is <NUM> for a large size, <NUM> for a medium size, and <NUM> for a small size. The UltraMirage® cushion <NUM> is shown in <FIG>.

Anthropometric data has indicated that mouth widths for patients with relatively small faces are not necessarily narrower than mouth widths for patients with relatively large faces. Hence, all faces generally have the same mouth width. Thus, the aperture <NUM> in the cushion <NUM> is made sufficiently wide to accommodate a wide range of patients and remains constant or almost constant, e.g., a range of <NUM>, regardless of the change in face height of a mask to fit larger faces. This can be seen in the substantially constant cushion geometry around the lower cheek and chin regions of the different cushion sizes, and thus the varying width to height ratios of the different cushion sizes. For example, the lower portion of the aperture <NUM> of each of the cushions <NUM>, <NUM>, <NUM>, <NUM> has substantially the same width.

As best shown in <FIG> and <FIG>, the face-contacting portion <NUM> of the cushion <NUM> includes a base wall <NUM>, a pair of underlying support cushions <NUM> extending away from the base wall <NUM>, and a membrane <NUM> provided to substantially cover at least a portion of the underlying cushions <NUM> and provide a sealing structure for the face contacting portion <NUM>. The base wall <NUM> and underlying cushions <NUM> provide a support structure for the membrane <NUM>.

As illustrated, the underlying cushions <NUM> are preferably provided on lateral sides of the base wall <NUM> only, e.g., in the side of nose, upper cheek, and lower cheek regions <NUM>, <NUM>, <NUM>, although the underlying cushions <NUM> could be joined and substantially surround the patient's nose and also the lower lip or chin region. The underlying cushions <NUM> add rigidity to the membrane <NUM> at the sides of the patient's mouth and cheeks. While it is preferable that the membrane <NUM> be thinner than the underlying cushions <NUM>, they could have the same thickness or the membrane could be thicker than the underlying cushion. Also, the elimination of an underlying cushion in the chin region <NUM> allows the cushion <NUM> to more deeply engage with the patient's face in this region without subjecting the patient's chin region <NUM> to excessive pressure. That is, there is no underlying cushion to restrain the movement of the membrane <NUM> in this region, which may improve the seal in this region and adjacent regions. Additionally, the elimination of an underlying cushion in the chin region <NUM> enables the cushion <NUM> to accommodate more facial shapes and provides more flexibility and allows for movement or opening of the mouth.

In the illustrated embodiment, the face-contacting portion <NUM> of the cushion has a double-walled construction, i.e., membrane <NUM> and underlying cushion <NUM>, in the side of nose, upper cheek, and lower cheek regions <NUM>, <NUM>, <NUM>, and a single-walled construction, i.e., membrane <NUM>, in the nasal bridge and chin regions <NUM>, <NUM> as shown in <FIG>. The single wall construction at the top and bottom of the cushion <NUM> helps to accommodate high landmarks, e.g., pointed chin, by allowing the center of the cushion <NUM> to flex. This flexibility accommodates more patients with the same cushion. However, the cushion <NUM> may have any other suitable construction, e.g., single walled, double walled, triple walled or more walled construction, in any suitable region of the cushion <NUM>, e.g., cheek, chin, nasal bridge. For example, the underlying cushion <NUM> may extend around the entire perimeter of the cushion <NUM>. Also, the underlying cushion <NUM> could be completely removed.

As shown in <FIG>, the membrane thickness may vary in the different regions of the cushion <NUM>. As illustrated, the membrane in the nasal bridge region <NUM> and upper cheek region <NUM> is <NUM> thick which transitions to <NUM> thickness in the upper cheek region <NUM> and maintains this thickness in the lower cheek and chin regions <NUM>, <NUM>. This arrangement provides greater compliance/stretch across the nasal bridge by providing a thinner membrane. This stretch is not required at the lower regions and here the thicker membrane is less likely to vibrate on the patient face in use.

Another aspect of the disclosure relates to the size and configuration of the base wall <NUM>, underlying cushion <NUM>, and membrane <NUM> of the cushion <NUM>. <FIG> illustrate the base wall <NUM>, underlying cushion <NUM>, and membrane <NUM> of the UltraMirage® cushion <NUM>. As illustrated, the cushion <NUM> has a different cross-sectional profile than the UltraMirage® cushion <NUM>.

For example, as best shown in <FIG>, the base wall <NUM> and the frame connection <NUM> are internally offset with respect to the most external cushion point <NUM>, e.g., external surface of membrane or underlying cushion. In contrast, the base wall <NUM> and frame connection <NUM> of the UltraMirage® cushion <NUM> are not offset with respect to the most external cushion point <NUM> (see <FIG>). As a result of this inward movement, the base width of the cushion <NUM> is narrowed, e.g., by about <NUM> or <NUM> per base, which provides a less obtrusive cushion and saves material which means less weight and cost. Also, the narrower cushion <NUM> provides less free length for the cushion <NUM> to bulge outwardly in use, thus helping to minimize or eliminate leakage.

As illustrated, a lower portion of the underlying cushion <NUM> has a more arcuate, e.g., semi-circular, question-mark, sickle-shape, configuration that defines a space <NUM> below a lower portion of the underlying cushion <NUM> and adjacent the base wall <NUM>.

In the illustrated embodiment, the widest or most external cushion point is the external surface of the underlying cushion <NUM> and the base wall <NUM> and frame attachment <NUM> are offset internally with respect to this. Thus, by the design of the cushion <NUM> and in particular the underlying cushion curvature, the frame is attached at a narrower point and thus the frame itself is narrower. This arrangement has significant advantages in terms of the frame weight, perceived bulk, and size. This arrangement may also minimize the dead space within the mask which will help to reduce CO<NUM> rebreathing.

Moreover, the space <NUM> below the underlying cushion <NUM> allows a greater range of movement of the underlying cushion <NUM> to add more flexibility to the underlying cushion <NUM> and hence the membrane <NUM> in use. Specifically, the space <NUM> below the underlying cushion <NUM> enables more displacement of the underlying cushion <NUM> using substantially the same space restraints as the UltraMirage® cushion <NUM>, for example. Additionally, the space <NUM> allows more displacement of the underlying cushion <NUM> before bottoming out, therefore reducing discomfort. Thus, this arrangement provides a more gradual force, improves comfort, and allows a wider range of patients to achieve seal.

As illustrated, the underlying cushion <NUM> has a spring-like connection with the base wall <NUM> such that the underlying cushion <NUM> can move with respect to the base wall <NUM>. That is, the underlying cushion <NUM> is movable into the space <NUM> (the underlying cushion <NUM> is also movable into the space <NUM>). Thus, a spring force is provided when a frame force is applied and the underlying cushion <NUM> is resiliently moved back into its initial position when the frame force is released. The underlying cushion <NUM> and/or base wall <NUM> may have any suitable spring constant, and the spring constant which, according to the invention as claimed, varies anywhere along its length, e.g., by tapering and/or varying the thickness of the base wall <NUM>, varying the thickness of intermediate and/or lower portions of the underlying cushion <NUM>. Also, the spring-like connection may extend along the whole underlying cushion <NUM> or the spring-like connection may be localized in certain regions such as the cheekbone region.

Thus, a spring characteristic is molded with the base wall <NUM> and underlying cushion <NUM> of the cushion <NUM> which allows a continuously variable spring constant to be incorporated into the base wall <NUM> and underlying cushion <NUM>, e.g., the wall stiffness can be varied at each cushion region to suit the sealing requirements in each region which may vary due to the underlying facial structure of the patient.

The spring characteristics of the base wall <NUM> and underlying cushion <NUM> may be modified by varying a number of characteristics shown in <FIG>. For example, the spring characteristics may be modified by varying the underlying cushion height h, the thickness t, the radius r, and the underlying cushion offset c. It is to be understood that these parameters are merely exemplary, and other parameters may be varied to modify the spring characteristics of the base wall <NUM> and underlying cushion <NUM>.

<FIG> illustrate parameters of an embodiment of the underlying cushion <NUM> and base wall <NUM> to achieve desired spring characteristics. As illustrated, the underlying cushion <NUM> and base wall <NUM> is configured to provide a variable spring constant around the perimeter of the cushion <NUM>. That is, the spring constant of the underlying cushion <NUM> and base wall <NUM> differs along the side of nose, upper cheek, and lower cheek regions <NUM>, <NUM>, <NUM>. Although specific parameters of the cushion <NUM> are shown in <FIG>, it is to be understood that these parameters are merely exemplary and other parameters are possible depending on application.

In the nasal bridge region <NUM> (e.g., see <FIG>), no underlying cushion <NUM> is provided in order to provide high flexibility and the ability to conform to a variety of facial shapes. However, in an embodiment, there may be an underlying cushion <NUM> with a very soft spring characteristic in this region.

In the side of nose regions <NUM> (see <FIG>), an underlying cushion <NUM> and base wall <NUM> with a fairly stiff spring characteristic is provided in order to provide lateral stability to squeeze the side of the patient's nose and keep the membrane <NUM> in contact with the underlying cushion <NUM>. As illustrated, this arrangement is achieved by a relatively thick underlying cushion, short height, and tight radius. In an embodiment of the section shown in <FIG>, h maybe <NUM>, r may be <NUM>, t may be <NUM>-<NUM>, b may be <NUM>, w1 may be <NUM>, and w2 may be <NUM>. In an embodiment of the section shown in <FIG>, h may be <NUM>, r may be <NUM>-<NUM>, t may be <NUM>, b may be <NUM>, w1 may be <NUM>, w2 may be <NUM>, and α may be <NUM>°. It is to be understood that these dimensions and ranges are merely exemplary and other dimensions and ranges are possible depending on application.

Also, as best shown in <FIG>, the base wall <NUM> and underlying cushion <NUM> in the side of nose regions <NUM> have been rotated by about <NUM> degrees with respect to the bottom of the frame. That is, the base wall <NUM> and underlying cushion <NUM> are inclined or angled in the side of nose regions <NUM> of the cushion <NUM>. This arrangement further increases the lateral stability and allows the force on the membrane to be applied perpendicular to the skin surface at the side of the patient's nose. This further helps to keep the membrane <NUM> in contact with the patient's skin and prevent any air leaks. In further embodiments, this angle may vary from <NUM> to <NUM> degrees.

In the upper cheek regions <NUM> (see <FIG>), the underlying cushion <NUM> and base wall <NUM> have a stiffness that is less than that provided in the side of nose regions <NUM> but stiffer than that provided in the lower cheek regions <NUM> due to the geometry of the underlying cushion, this is provided to suit the firmer bone structure of the upper cheeks. In an embodiment of the section shown in <FIG>, h may be <NUM>-<NUM>, preferably <NUM>, r may be <NUM>, t may be <NUM>, b may be <NUM>, and w1 may be <NUM>. In an embodiment of the section shown in <FIG>, h may be <NUM>-<NUM>, preferably <NUM>, r may be <NUM>, t may be <NUM>, b may be <NUM>, and w1 may be <NUM>. It is to be understood that these dimensions and ranges are merely exemplary and other dimensions and ranges are possible depending on application.

In the lower cheek regions <NUM> (see <FIG>), the underlying cushion <NUM> and base wall <NUM> has a relatively low spring constant. That is, the underlying cushion <NUM> in the lower cheek regions <NUM> is fairly soft since the fleshy cheek region of the patient deforms readily to form a seal with the cushion at relatively low forces. As illustrated, this arrangement is achieved by a greater height h, larger radii r, and a thinner underlying cushion wall. In an embodiment of the section shown in <FIG>, h may be <NUM>, r1 may be <NUM>, r2 may be <NUM>, t may be <NUM>-<NUM>, b may be <NUM>, and w1 may be <NUM>. In an embodiment of the section shown in <FIG>, h may be <NUM>, r1 may be <NUM>-<NUM>, r2 may be <NUM>, t may be <NUM>, b may be <NUM>, and w1 may be <NUM>. In an embodiment of the section shown in <FIG>, h may be <NUM>, r1 may be <NUM>-<NUM>, r2 may be <NUM>-<NUM>, t may be <NUM>, b may be <NUM>, and w1 may be <NUM>. It is to be understood that these dimensions and ranges are merely exemplary and other dimensions and ranges are possible depending on application.

In the chin region <NUM> (see <FIG>), no underlying cushion <NUM> is provided, although a very flexible spring region may be used. The chin region <NUM> provides an unconstrained membrane region that allows for lateral movement, mouth opening or movement, and a range of facial shapes.

Thus, the cushion <NUM> may be configured to provide different vertical and/or lateral stiffness in different regions of the cushion. For example, the side of nose regions <NUM>, <NUM> are laterally stiffer than the other regions in order to provide more lateral stability at the patient's nose.

<FIG> illustrate alternative embodiments of the base wall <NUM> and the underlying cushion <NUM>. Each of these embodiments provides an arrangement that allows flexibility of the underlying cushion <NUM> in use. In <FIG>, the underlying cushion <NUM> defines an enclosed space <NUM> that may optionally be filled with pressurized air, foam, gel, or elastomeric material and adapted to dampen movement of the underlying cushion <NUM> in use. In <FIG>, the space <NUM> below the underlying cushion <NUM> is within the interior of the breathing cavity. Also, the underlying cushion <NUM> has an arcuate shape that curves away from the interior of the breathing cavity towards the base wall <NUM>. However, the underlying cushion <NUM> may have any other suitable shape. For example, the underlying cushion <NUM> in <FIG> has a bulbous shape, which may be solid or hollow. In <FIG>, the underlying cushion <NUM> has a general Z-shape. In <FIG>, the underlying cushion <NUM> has a bulbous shape (which may be solid or hollow), and the space <NUM> below the underlying cushion <NUM> has a ramped configuration. In <FIG>, the bulbous shape may optionally be filled with pressurized air, foam gel, or elastomeric material and adapted to dampen movement of the underlying cushion <NUM> in use. In <FIG> the ramped configuration of the space <NUM> is adapted to direct the underlying cushion <NUM> downwardly into the base wall <NUM> in use, and in <FIG> the ramped configuration of the space <NUM> is adapted to direct the underlying cushion <NUM> inwardly towards the breathing cavity in use. In <FIG>, and <NUM>, the underlying cushion <NUM> has a general T-shape. Also, in <FIG>, the base wall <NUM> defines an enclosed space <NUM> below the T-shaped underlying cushion <NUM>. The enclosed space <NUM> may be optionally filled with pressurized air, foam, gel, or elastomeric material and adapted to dampen movement of the underlying cushion <NUM> in use. Moreover, the spring constant may be varied by varying the pressure within the enclosed space <NUM>. Additionally, the lower surface of the space <NUM> may have a ramped configuration (as shown in <FIG>) adapted to direct the underlying cushion <NUM> inwardly towards the breathing cavity in use. The lower surface of the enclosed space <NUM> in <FIG> may also have a ramped configuration for directing the underlying cushion <NUM> in use. In <FIG>, the underlying cushion <NUM> has an elongated section length for soft spring characteristics. <FIG> illustrates a single wall construction with an underlying cushion <NUM> and no membrane. In <FIG>, the space <NUM> below the underlying cushion <NUM> is greatly increased. In <FIG>, a spring construction is provided below the base wall <NUM>.

The space <NUM> allows more displacement of the underlying cushion <NUM> for a predetermined amount of force when compared to the UltraMirage® cushion <NUM>. That is, the underlying cushion <NUM> provides more movement for a given force. For example, <FIG> illustrates the general relationship between Force and Displacement for the cushion <NUM> and the UltraMirage® cushion <NUM>. As illustrated, the curve for the cushion <NUM> is flatter than the exponential-type curve of the UltraMirage® cushion <NUM>. Thus, the underlying cushion <NUM> is less stiff and more compliant when compared to the UltraMirage® cushion <NUM>. It is noted that the space <NUM> could be filled with a gel, silicone or other structure to vary the spring characteristic that it provides.

Further, as illustrated in <FIG>, the point B<NUM> at which the cushion <NUM> is fully compressed or bottomed-out is at a greater displacement than the point B<NUM> at which the UltraMirage® cushion <NUM> is bottomed-out. Moreover, the bottom-out point B<NUM> occurs at a greater force than the bottom-out point B<NUM>. Thus, the cushion <NUM> increases the force required to bottom-out, and provides a wider range of adjustment. Additionally, <FIG> illustrates an example of maximum and minimum comfortable sealing forces, which provides an example force range necessary to achieve seal. As illustrated, the range of displacement A<NUM> within this force range for the cushion <NUM> is substantially larger than the range of displacement A<NUM> within this force range for the UltraMirage® cushion <NUM>. Thus, the cushion <NUM> allows a wide range of adjustment or displacement to achieve seal, and ensures that the sealing force is substantially less than the bottom-out force so that the cushion does not have to bottom-out to seal.

<FIG> illustrates another embodiment of the relationship between Force and Displacement for the cushion <NUM> and the UltraMirage® cushion <NUM>. In this embodiment, the linear portion of the curve for cushion <NUM> has a greater slope than the linear portion of the curve for cushion <NUM> in <FIG>. The difference in slope may be attributed to a difference in spring constants of respective underlying cushions <NUM>. Thus, the cushion represented in <FIG> provides more displacement for a given force than the cushion represented in <FIG>. Also, the curve for the cushion <NUM> in <FIG> intersects with the curve for the UltraMirage® cushion <NUM>, such that the force of cushion <NUM> is higher at lower displacement, to ensure a seal, and lower at higher displacement, to maintain comfort for a longer range of displacement.

<FIG> illustrates another embodiment of the relationship between Force and Displacement for the cushion <NUM>. In this embodiment, typical curves for the different regions of the cushion <NUM> are shown. Specifically, one curve represents the cross-sections of <FIG> in the side of nose region <NUM>, another curve represents the cross-sections of <FIG> in upper cheek and lower cheek regions <NUM>, <NUM>, and yet another curve represents the cross-sections of <FIG> in the lower cheek region <NUM>. As illustrated, the cushion <NUM> is softer or less stiff in the lower regions of the cushion <NUM>.

<FIG> illustrate the extended length of the flexible underlying cushion <NUM> which is used to provide a softer spring characteristic in selected regions of the cushion <NUM> when compared with a typical prior art cushion, e.g., the UltraMirage® cushion <NUM>. The length a to b can deform, thus providing a spring characteristic. As illustrated, the length a to b of the cushion <NUM> (<FIG>) is considerably longer when compared to the UltraMirage® cushion <NUM> (<FIG>) due to the curvature of the underlying cushion <NUM>. In the illustrated embodiment, the length a to b of the cushion <NUM> is <NUM>. However, in an embodiment, the length a to b of the cushion <NUM> may be in the range of <NUM>-<NUM>, preferably <NUM>-<NUM>, most preferably <NUM>-<NUM>. In another embodiment, the length a to b of the cushion <NUM> may be in the range of <NUM>-<NUM>. The length b to c is fairly rigid and does not deform to provide a spring characteristic. The added length in the cushion <NUM> has been achieved by the arcuate shape of the underlying cushion <NUM> and the space <NUM> is a result of this shape. This added length adds flexibility and a greater range of movement to the cushion <NUM>. <FIG> illustrate other embodiments for achieving a longer section length.

The membrane <NUM> is structured to form an effective seal around nasal bridge, side of nose, upper cheek, lower cheek, and chin regions <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of a patient. Another aspect of the disclosure relates to the configuration of the membrane <NUM> in the nasal bridge region <NUM> of the cushion <NUM>, which has been structured to improve sealing and comfort in this region.

Specifically, as shown in a preferred embodiment in <FIG> and in an alternative embodiment in <FIG>, the membrane <NUM>, according to the invention as claimed, forms an elongated ridge <NUM> in the nasal bridge region <NUM> wherein sloping sides <NUM> meet to form an elongated crest <NUM>. Each of the sloping sides <NUM>, according to the invention as claimed, is angled from the crest centerline in the range of <NUM>-<NUM>°, preferably about <NUM>°. The crest <NUM>, according to the invention as claimed, has a radius of curvature in the range of <NUM>-<NUM>, preferably about <NUM>. As illustrated, the underlying cushion <NUM> has been eliminated from beneath the membrane <NUM> in the nasal bridge region <NUM>, which allows the membrane <NUM> in this region to freely move between the underlying cushions <NUM> provided in the side of nose regions <NUM>. As discussed in greater detail below, this membrane configuration allows the creation of a steeply inverted section upon engagement with the patient's nose, which improves fit, comfort, and seal in the nasal bridge region <NUM>. In contrast, the UltraMirage® cushion <NUM> is relatively flat in this region (see <FIG>).

As shown in a preferred embodiment in <FIG> and in an alternative embodiment in <FIG>, the forward end <NUM> of the elongated ridge <NUM> has an arcuate configuration. The forward end <NUM> is structured to engage the patient's nasal bridge region and has a radius of curvature in the range of <NUM>-<NUM>, preferably about <NUM>.

As shown in <FIG>, the membrane <NUM> in the nasal bridge region <NUM> has a sharper cross-sectional profile than the corresponding portion of the UltraMirage® cushion <NUM> (see <FIG>). Specifically, the membrane <NUM> provides a large contoured portion that curves inwardly towards the cavity of the cushion along a radius to terminate at an inner edge of the membrane <NUM>. This arrangement more closely follows the contour or curvature of the patient's nasal bridge region. In the illustrated embodiment, the membrane <NUM> is angled with respect to a face contacting plane of the cushion, e.g., in the range of <NUM>-<NUM>°. In contrast, the corresponding angle of the UltraMirage® cushion <NUM> is about <NUM>°. This arrangement provides more comfort and a better fit for the patient.

As best shown in <FIG>, the nasal bridge region <NUM> has a substantially flat portion <NUM>, e.g., on the apex of the membrane curvature, in elevation view that may deform to provide a more comfortable fit for a wide range of patients, e.g., from flatter nasal bridges to sharper nasal bridges.

Specifically, one aspect of the disclosure is to provide a membrane <NUM> in the nasal bridge region <NUM> that will accommodate "flat faces", e.g., those patient's with a low nasal bridge. In order to achieve this, the cushion <NUM> has an upper point A which is higher than or level with points B (see <FIG>). This height in the nasal bridge region <NUM> is combined with a rolled edge that keeps the surface area of the membrane <NUM> substantially flat against the patient's nasal bridge. Keeping the surface area of the membrane <NUM> substantially flat against the patient's nasal bridge prevents leaks at the edge of the membrane.

The rolled edge also allows movement to accommodate higher nasal bridges. This arrangement is achieved without "stretching" the membrane which can lead to discomfort and patient sores. For example, the displacement of the cushion <NUM> at the nasal bridge region <NUM> may be greater than about <NUM>, e.g., <NUM>. In contrast, the UltraMirage® cushion <NUM> provides displacement of about <NUM> in the nasal bridge region. At these displacements, the membrane becomes quite taut, i.e., the point on the force vs. displacement graph where the force begins to rise sharply for a small displacement (see <FIG>).

The displacement values. of the cushion in the nasal bridge region for some prior art cushions are as follows:.

The above displacement values are by no means an accurate representation of what nose depth the cushion will cover. Rather, these displacement values are only an indication of the flexibility and/or range of the membrane. Thus, the cushion <NUM> provides an arrangement that is much more flexible and/or rangy than the UltraMirage® cushion <NUM>, for example.

The force vs. displacement graph of membrane <NUM> in the nasal bridge region <NUM> has a large displacement for relatively low forces. For example, as shown in <FIG>, the displacement provided by the cushion <NUM> in the nasal bridge region <NUM> is larger than that provided by the UltraMirage® cushion <NUM>. This allows the cushion <NUM> to accommodate relatively deep nasal bridges in use. Also, the molded (undeformed) cushion state of the UltraMirage® cushion <NUM> (i.e., no force applied) does not comfortably accommodate a relatively flat or shallow nasal bridge. In an embodiment, the membrane of the cushion <NUM> blows out to meet patient's faces with shallow nasal bridges. Thus, the cushion <NUM> also accommodates a wider range of nasal bridge shapes than the UltraMirage® cushion <NUM>.

Further, as shown in <FIG>, the profile of the membrane is more sharply peaked as compared to a flat profile or a saddle shape (e.g., compare with UltraMirage® cushion <NUM> in <FIG>). Also, as shown in <FIG>, flat portion in the nasal bridge region <NUM> extends along a relatively flat plane P1, and this plane P1 is angled at an angle A with respect to the plane P2 that defines the frame connection.

Thus, the shape (e.g., peak), the rolled edge, and the height, in the nasal bridge region <NUM> provide large displacement at relatively low forces. This arrangement accommodates a wider range of patients, e.g., from those with a low nasal bridge to those with a high nasal bridge, while maintaining a seal against the patient's face with little force on the membrane.

It is noted that the cushion height may vary around the cushion perimeter to vary flexibility or cushion displacement in different regions of the cushion. A reference dimension <NUM> for measurement of the cushion height (which may also be referred to as the membrane height) - i.e. the height between the apex of the membrane to where it meets the underlying cushion - is shown in <FIG>. A reference dimension <NUM> for measurement of the cushion height of the prior art cushion is shown in <FIG>.

As shown in <FIG>, the inner edge of the membrane <NUM> defines the aperture <NUM> that receives the patient's nose and mouth. As illustrated, the aperture <NUM> has a generally triangular shape. Also, the apex of the aperture <NUM> has a rounded notch <NUM>, e.g., keyhole. The notch <NUM> improves the seal with nasal bridge regions of various sizes and shapes, particularly patients with sharp noses. The notch <NUM> has a radius of curvature in the range of <NUM>-<NUM>, preferably about <NUM>. This rounded keyhole shape has a length, e.g., the keyhole shape extends outwards from an interior portion of the cushion, of at least <NUM>, as shown in <FIG>.

<FIG> include hand-marked lines applied to the outer surface of the nasal bridge region <NUM> of the cushion <NUM> to illustrate the rolling action of the nasal bridge region <NUM> of the membrane <NUM> upon engagement with the patient's nose. As described above, the membrane <NUM> in the nasal bridge region <NUM>, according to the invention as claimed, includes sloping sides <NUM> that meet to form an elongated crest <NUM> as shown in <FIG>. As the patient's nasal bridge (simulated using a small rod) is engaged with the nasal bridge region <NUM> of the membrane <NUM> (see <FIG>), the membrane <NUM> creates a steeply inverted section <NUM> wherein the sloping sides <NUM> invert their position as the membrane <NUM> moves between the underlying cushions <NUM> provided in the side of nose regions <NUM>. As the membrane <NUM> comes more into contact with the patient's nasal bridge, the leading edge <NUM> of the inverted section "rolls" towards the top of the cushion <NUM> as the membrane <NUM> conforms to the patient's face as shown in <FIG>. This structure is advantageous since it allows the cushion <NUM> to accommodate patients having a wide range of nasal profiles, including those with relatively low and relatively high root depth at the nose. <FIG> and <FIG> show the nasal bridge region <NUM> of the membrane <NUM> in its completely inverted position. The creation of the steeply inverted section <NUM> upon engagement with the patient's nose provides a better seal and reduces the risk of creasing and/or folding and associated discomfort and leaks. That is, this configuration encourages rolling instead of creasing which can be detrimental to patient comfort and seal.

<FIG> illustrate another embodiment of a cushion <NUM>. In each of the figures, portions of the cushion <NUM> that are substantially similar to the cushion <NUM> are indicated with similar reference numerals.

<FIG> illustrates the base wall <NUM>, underlying cushion <NUM>, and membrane <NUM> of the cushion <NUM> (in solid lines) in relation to the base wall <NUM>, underlying cushion <NUM>, and membrane <NUM> of the UltraMirage® Full Face cushion <NUM> (in dashed lines). As illustrated, the cushion <NUM> has a different cross-sectional profile than the UltraMirage® Full Face cushion <NUM>.

For example, the membrane <NUM> is connected to the underlying cushion <NUM> at a position that is further inwardly and upwardly with respect to the membrane connection of the UltraMirage® cushion <NUM>. This arrangement substantially removes the vertically extending groove <NUM> provided in the UltraMirage® cushion <NUM>. Also, this arrangement narrows the width of the membrane <NUM>, e.g., in the range of <NUM>-<NUM>, preferably about <NUM>, with respect to the corresponding portion of the UltraMirage® cushion <NUM>. As a result of this and the inward movement of the non-face contacting portion <NUM>, this narrows the total width of the cushion <NUM> by about <NUM>, e.g., about <NUM> per base, which provides a less obtrusive cushion and saves material. Also, the narrower membrane <NUM> provides less free length for the cushion <NUM> to bulge outwardly in use, thus helping to minimize or eliminate leakage. Further, the base wall <NUM> and the frame connection <NUM> are internally offset with respect to the most external cushion point, e.g., external surface of underlying cushion. <FIG> also shows the longer length a to b in the cushion <NUM> when compared to the UltraMirage® cushion <NUM>.

<FIG> illustrates further structural details and dimensions in one embodiment of the base wall <NUM>, underlying cushion <NUM>, and membrane <NUM> of the cushion <NUM>. For example, the depth of the space <NUM> is in the range of <NUM>-<NUM>, preferably about <NUM>.

<FIG> illustrates the elongated ridge <NUM> in the nasal bridge region <NUM>. Each of the sloping sides <NUM> is angled from the crest centerline in the range of <NUM>-<NUM>°, preferably about <NUM>°. The crest <NUM> has a radius of curvature in the range of <NUM>-<NUM>, preferably about <NUM>. As shown in <FIG>, the forward end <NUM> of the elongated ridge <NUM> has a radius of curvature in the range of <NUM>-<NUM>, preferably about <NUM>.

<FIG> and <FIG> illustrate the flat portion <NUM> in the nasal bridge region <NUM> of the cushion <NUM>. Also, as shown in <FIG>, the membrane <NUM> in the nasal bridge region <NUM> has a first portion with a radius of curvature in the range of <NUM>-<NUM>, preferably about <NUM>, and a second portion with a radius of curvature in the range of <NUM>-<NUM>, preferably about <NUM>. In the illustrated embodiment, the membrane <NUM> is angled with respect to a face contacting plane of the cushion in the range of <NUM>-<NUM>°, preferably about <NUM>°.

<FIG> illustrate another embodiment of a cushion <NUM>. As best shown in <FIG>, the cushion includes at least a base wall <NUM> and a membrane <NUM>. As illustrated, the length of the membrane <NUM> (e.g., membrane cross-sectional length) in a nasal bridge region may change. For example, the membrane length may be selected to have a shorter length L<NUM> or a longer length L<NUM> in the nasal bridge region.

As shown in <FIG>, the membrane length controls how far on the patient's nose the displaced cushion membrane will sit when fitted onto the patient's face (shown by the dotted line on the patient's facial profile). This arrangement prevents the potential (e.g., particularly for patients with a shallow nasal bridge depth) for any excess cushion membrane to sit too far down on the patient's nose, which may lead to facial discomfort and skin markings on the patient's nose.

<FIG> illustrate another embodiment of a cushion <NUM>. The cushion <NUM> includes a base wall <NUM>, an underlying support cushion <NUM>, and a membrane <NUM>. As described above, the underlying cushion <NUM> is preferably provided on lateral sides of the cushion <NUM> only.

The base wall <NUM> may be internally offset with respect to the most external cushion point, e.g., external surface of membrane or underlying cushion. This arrangement provides a spring characteristic which may be varied around the cushion perimeter to vary the cushion flexibility (lateral and/or vertical) around the cushion perimeter, e.g., the cushion stiffness can be varied at each cushion region to suit the sealing requirements in each region which may vary due to the underlying facial structure of the patient. That is, the level if bias (e.g., from "hard" to "soft") along the sides of the cushion may be changed.

For example, <FIG> illustrate cross-sections through three different regions R1, R2, R3 in the cushion <NUM>. As shown in <FIG>, the base wall <NUM>, the underlying cushion <NUM>, and the membrane <NUM> cooperate to define a relatively straight external surface <NUM>. This provides a minimal spring component in the region R1, e.g., hard or stiff characteristics.

As shown in <FIG>, the base wall <NUM>, the underlying cushion <NUM>, and the membrane <NUM> cooperate to define an external surface <NUM> that transitions from a relatively straight configuration to a curved configuration. This provides a relatively small offset for a more flexible spring component than the region R1.

As shown in <FIG>, the base wall <NUM>, the underlying cushion <NUM>, and the membrane <NUM> cooperate to define an external surface <NUM> that curves outwards from the base wall <NUM>. This provides a relatively large offset for an optimal spring component in the region R3, e.g., soft or flexible characteristics.

Thus, the cushion <NUM> may be designed to provide varying flexibilities around its perimeter which allows the cushion <NUM> to conform to a variety of facial shapes.

<FIG> illustrate another embodiment of a cushion <NUM>. The cushion <NUM> includes a base wall <NUM>, an underlying support cushion <NUM>, and a membrane <NUM>. As illustrated, the underlying cushion <NUM> is preferably provided on lateral sides of the cushion <NUM> only, e.g., no underlying cushion at nasal bridge and chin regions (see <FIG>).

As shown in <FIG>, the base wall <NUM> includes a tapered portion <NUM> when compared to <FIG>, which tapers towards the membrane <NUM> according to the invention as claimed. This arrangement may improve moldability.

<FIG> illustrates an alternative arrangement to the cushion <NUM> of <FIG> (arrangement of <FIG> shown in dashed lines). As illustrated, material has been removed from the side wall <NUM> and the space or gap <NUM> has been reduced with respect to the arrangement of <FIG>. This arrangement of <FIG> increases displacement with respect to the previous displacement of <FIG>. The increased displacement is achieved by the changed geometry in the side wall <NUM>. It is noted that the gap <NUM> may be variable or constant around the cushion perimeter.

<FIG> illustrates an alternative arrangement to the cushion <NUM> of <FIG> (arrangement of <FIG> shown in dashed lines). As illustrated, some material has been removed from the side wall <NUM> and the space or gap <NUM> has been reduced with respect to the arrangement of <FIG>. This arrangement of <FIG> increases displacement with respect to the previous displacement of <FIG>. The increased displacement is achieved by the changed geometry in the side wall <NUM>. This arrangement may require the cross-section of the base wall <NUM> to be thickened to add stiffness around the cushion perimeter or locally. Stiffening may be achieved by local ribs where required.

<FIG> illustrates an alternative arrangement to the cushion <NUM> shown in <FIG>. As illustrated, the keyhole-shaped cutout (for receiving the patient's nasal bridge region) may be larger as the mask size reduces. For example, the cutout is larger for an extra small size mask than a large size mask.

It is noted that the cross-section design of the cushion at specific areas of the patient's face (e.g., <FIG>) may be in the specific area or any area around the cushion perimeter. That is, the cross-section design should not be limited to the specified area. Also, the cross-section shown in <FIG> may be employed at any point around the cushion perimeter.

Claim 1:
A cushion (<NUM>, X10) for a patient interface that delivers breathable gas to a patient, the cushion comprising:
a base wall (<NUM>, X28) structured to be connected to a frame;
and
a membrane (<NUM>, X28) adapted to form a continuous seal on the patient's face,
wherein at least a portion of the base wall (<NUM>, X28) includes a tapered portion that tapers towards the membrane (<NUM>, X32);
wherein a spring constant that varies along a length of the seal is defined y the base wall (<NUM>, X28) and/or an optional underlying support cushion (<NUM>, X30) extending away from the base wall towards the patient's face in use, wherein the membrane is provided to substantially cover at least a portion of the underlying support cushion;
wherein the membrane (<NUM>, X28) includes a nasal bridge region (<NUM>, X16) adapted to form a continuous seal on a nasal bridge region of the patient's face and forms an elongated ridge (<NUM>, X35) in the nasal bridge region (<NUM>, X16), the elongated ridge (<NUM>, X35) having sloping sides (<NUM>, X36) that meet to form an elongated crest (<NUM>, X38), and wherein each of the sloping sides (<NUM>, X36) is angled from a centreline of the crest (<NUM>, X38) in the range of <NUM>-<NUM>° and the crest (<NUM>, X38) has a radius of curvature in the range of <NUM>-<NUM>; and
wherein the elongated ridge (<NUM>, X35) is structured to invert its configuration upon engagement of the membrane's nasal bridge region (<NUM>, X16) with the patient's nasal bridge region to create an inverted section of the membrane (<NUM>, X32) and a leading edge of the inverted section is adapted to roll as the elongated ridge (<NUM>, X35) inverts its configuration.