Vent and vent adaptor for patient interface

1. A patient interface system configured to provide respiratory therapy to a patient with a therapy flow of gas pressurized above ambient pressure throughout the patient's respiratory cycle, the patient interface system comprising:

a seal-forming structure constructed from a soft, flexible, resilient material and configured to seal against the patient's face in use to provide the therapy flow of gas to the patient's airways;

a plenum chamber joined to the seal-forming structure and having a connection port configured to receive the therapy flow of gas during use;

a positioning and stabilising structure comprising at least one strap and configured to secure the seal-forming structure on the patient in use; and

a vent system configured to provide a vent flow of gas to discharge gas exhaled by the patient from a pressurized volume, the vent flow being continuous during the respiratory therapy,

a vent housing comprising a base having at least one first orifice extending through the base to allow gas to be discharged to atmosphere from the pressurized volume;

at least one second orifice to allow gas to be discharged to atmosphere from the pressurized volume; and

a membrane positioned adjacent to the base,

wherein the pressurized volume is in fluid communication with atmosphere through the at least one first orifice and the at least one second orifice throughout a therapeutic pressure range, and

wherein the membrane is elastically deformable due to pressure within the pressurized volume to apportion the vent flow between the at least one first orifice and the at least one second orifice throughout the therapeutic pressure range, and

wherein the membrane is not attached to the vent system such that the membrane is freely movable towards and away from the base.

2. The patient interface system of claim 1 , wherein the vent housing comprises an outer wall and an inner wall, the inner wall defining an inlet for the therapy flow of gas, and

wherein the base is positioned between the outer wall and the inner wall.

3. The patient interface system of claim 2 , wherein the base further comprises an inner base and an outer base.

4. The patient interface system of claim 3 , wherein the outer base is adjacent to the outer wall, the inner base is adjacent to the outer base, and the inner base is adjacent to the inner wall.

5. The patient interface system of claim 4 , wherein the at least one first orifice further comprises a plurality of first orifices and the at least one second orifice further comprises a plurality of second orifices.

6. The patient interface system of claim 5 , wherein the plurality of second orifices pass through the outer base and the plurality of first orifices pass between the outer base and the inner base.

7. The patient interface system of claim 6 , further comprising a plurality of base connectors to join the inner base and the outer base and to divide the plurality of first orifices.

8. The patient interface system of claim 7 , further comprising a plurality of membrane spacers extending from the inner base.

9. The patient interface system of claim 8 , wherein the membrane is supported over the plurality of first orifices on the outer base and the membrane spacers.

10. The patient interface system of claim 8 , wherein the vent housing comprises a base divider between the inner base and the outer base, and

wherein the membrane is supported over the plurality of first orifices on the base divider and the membrane spacers.

11. The patient interface system of claim 8 , wherein the plurality of membrane spacers define a plurality of membrane spacer gaps between adjacent ones of the plurality of membrane spacers.

12. The patient interface system of claim 8 , wherein the membrane includes an atmosphere-side surface adjacent to the inner base and the outer base of the vent housing and an inner surface defining a membrane opening, and

wherein an inner base membrane passage for the vent flow is defined between the atmosphere-side surface of the membrane and the inner base of the vent housing.

13. The patient interface system of claim 12 , wherein an inner wall membrane passage for the vent flow is defined between the inner surface of the membrane and the inner wall of the vent housing.

14. The patient interface system of claim 8 , wherein the inner base comprises a plurality of inner base slots positioned between individual membrane spacers.

15. The patient interface system of claim 5 , wherein the outer base comprises a plurality of lateral membrane supports that are configured to prevent the membrane from covering the plurality of second orifices.

16. The patient interface system of claim 5 , wherein the vent housing comprises a plurality of recesses opposite the outer base, and

wherein at least one of the plurality of second orifices opens into a corresponding one of the plurality of recesses.

17. The patient interface system of claim 3 wherein the inner wall extends above the inner base and the outer base.

18. The patient interface system of claim 3 , wherein the inner wall extends below the inner base and the outer base.

19. The patient interface system of claim 3 , wherein the outer wall, the inner wall, the inner base, the outer base, and the membrane are circular.

20. The patient interface system of claim 19 , wherein the outer wall, the inner wall, the inner base, the outer base, and the membrane are concentric.

21. The patient interface system of claim 1 , wherein the vent housing comprises a shaft extending from the base to receive the therapy flow of gas, the at least one first orifice passing through the base, and the at least one second orifice passing through the shaft.

22. The patient interface system of claim 21 , wherein the at least one first orifice and the at least one second orifice are oriented such that the vent flow passing through the at least one first orifice and the at least one second orifice intersects outside of the vent housing.

23. The patient interface system of claim 22 , further comprising a diffuser,

wherein the vent flow passing through the at least one first orifice and the at least one second orifice intersects within the diffuser.

24. The patient interface system of claim 23 , wherein the at least one first orifice further comprises a plurality of first orifices and the at least one second orifice further comprises a plurality of second orifices.

25. The patient interface system of claim 1 , wherein the membrane comprises an elastically deformable material.

26. The patient interface system of claim 25 , wherein the elastically deformable material comprises silicone.

27. The patient interface system of claim 1 , wherein the vent housing is formed from a single, homogeneous piece of a relatively rigid material.

28. The patient interface system of claim 27 , wherein the relatively rigid material is polycarbonate.

29. The patient interface system of claim 1 , further comprising a tube that connects the vent system to the plenum chamber at the connection port to allow gas to flow between the vent system and the plenum chamber during use.

30. The patient interface system of claim 1 , further comprising an air circuit removably connected to the vent system to direct the therapy flow of gas to the patient from a respiratory pressure therapy device during use.