Cushion for patient interface

1. A cushion for a patient interface that delivers breathable gas to a patient, the cushion comprising:

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 including at least a nasal bridge region adapted to form a continuous seal on a nasal bridge region of the patient's face,

wherein the membrane includes a curvature, and the membrane in the nasal bridge region has a substantially flat portion on an apex of the membrane curvature in elevation view,

wherein the nasal bridge region of the membrane includes a contoured portion along a longitudinal axis of the cushion to closely follow a contour or curvature of the patient's nasal bridge region, the contoured portion curves inwardly towards a cavity of the cushion along a radius to terminate at an inner edge of the membrane, the contoured portion having a free end that is angled with respect to a face contacting plane of the cushion in the range of 30-50°, and

wherein the membrane in the nasal bridge region forms an elongated ridge along the longitudinal axis of the cushion, the elongated ridge having sloping sides that meet to form an elongated crest, and the elongated ridge is structured to engage with the patient's nasal bridge region in use.

2. A cushion

according to claim 1 , wherein the membrane includes cheek and chin regions adapted to form a continuous seal on cheek and chin regions of the patient's face, respectively, the nasal bridge and adjacent two cheek regions defining an intersection,

wherein the membrane in the nasal bridge region has a height between a peak of the intersection to where it meets the underlying support cushion that is greater than a corresponding height in an adjacent portion of the cheek region.

3. The cushion according to claim 2 , wherein the membrane in the nasal bridge region has a rolled edge.

4. The cushion according to claim 2 , wherein the underlying cushion is provided only on lateral sides of the base wall in the cheek region of the membrane.

5. A cushion according to claim 1 ,

wherein the underlying cushion has a spring-like connection with the base wall, the underlying cushion and/or base wall defining a spring constant that varies along a length of the seal, and

wherein 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.

6. A cushion according to claim 1 ,

wherein 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.

7. The cushion according to claim 6 , wherein a depth of the base wall internal offset is different in different regions of the cushion, and the depth is at least partially determinative of a spring-like characteristic provided by the base wall and the underlying cushion.

8. The cushion according to claim 1 , wherein each of the sloping sides is angled from a crest centerline in the range of 30-60° and the crest has a radius of curvature in the range of 1.0-5.0 mm.

9. The cushion according to claim 8 , wherein each of the sloping sides is angled from a crest centerline by about 40°-50°, and the crest has a radius of curvature of about 2.5 mm.

10. The cushion according to claim 8 , wherein a forward portion of the elongated ridge has an arcuate configuration having a radius of curvature in the range of 1.5-7.0 mm.

11. The cushion according to claim 10 , wherein the forward portion has a radius of curvature of about 4.0 mm.

12. The cushion according to claim 1 , wherein a leading edge of the elongated ridge is adapted to roll in use.

13. The cushion according to claim 1 , wherein the contoured portion is angled about 40° with respect to a face contacting plane of the cushion.

14. The cushion according to claim 1 , wherein the underlying cushion and/or base wall has a question-mark or sickle shape.

15. The cushion according to claim 1 , wherein an inner edge of the membrane defines a generally triangular-shaped aperture that receives the patient's nose and mouth, and a lower portion of the aperture that receives the patient's mouth has a width greater than about 54 mm.

16. The cushion according to claim 1 , wherein the cushion is a nasal cushion.

17. The cushion according to claim 16 , wherein the membrane includes nasal bridge, side of nose, and upper lip regions adapted to form a continuous seal on nasal bridge, side of nose, and upper lip regions of the patient's face, respectively.

18. The cushion according to claim 1 , wherein the cushion is a full-face cushion.

19. The cushion according to claim 18 , wherein 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.