Vent adaptor for patient interface system

1. A vent system for use with a patient interface during respiratory therapy of a patient with a therapy flow of gas pressurized above ambient pressure, the vent system providing a vent flow of gas to discharge gas exhaled by the patient from a pressurized volume, the vent flow of gas being continuous during the respiratory therapy, the vent system comprising:

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;

a vent housing connector having an outlet opening configured to direct the therapy flow of gas to the patient interface;

a heat and moisture exchanger (HME) comprising an HME housing and an HME material within the HME housing; and

a membrane positioned adjacent to the base,

wherein the vent housing and the vent housing connector are configured to be connected to, at least in part, form a cavity, and

wherein the HME is positioned in the cavity when the vent system is assembled,

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 of gas between the at least one first orifice and the at least one second orifice throughout the therapeutic pressure range.

2. The vent system of claim 1 , further comprising an annular lip extending from around an inner periphery of the vent housing and at least one retaining protrusion extending from the annular lip.

3. The vent system of claim 2 , further comprising an annular recess extending around an outer periphery of the HME housing,

wherein the at least one retaining protrusion and the annular recess are configured to removably connect the HME housing to the vent housing.

4. The vent system of claim 3 , wherein the HME housing is removably connected to the vent housing with a snap-fit.

5. The vent system of claim 3 , wherein the HME housing comprises a patient-side HME housing portion and an atmosphere-side HME housing portion, and

wherein vent assembly is configured such that the patient-side HME housing portion is positioned closer to the patient than the atmosphere-side HME housing portion in use.

6. The vent system of claim 5 , wherein the annular recess is provided to the atmosphere-side HME housing portion.

7. The vent 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.

8. The vent system of claim 7 , wherein the base further comprises an inner base and an outer base.

9. The vent system of claim 8 , 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.

10. The vent system of claim 8 , wherein the at least one first orifice further comprises a plurality of inner orifices and the at least one second orifice further comprises a plurality of outer orifices.

11. The vent system of claim 10 , wherein the plurality of outer orifices pass through the outer base and the plurality of inner orifices pass between the outer base and the inner base.

12. The vent system of claim 8 , wherein the membrane comprises an elastically deformable material.

13. The vent system of claim 12 , wherein the elastically deformable material comprises silicone.

14. The vent system of claim 8 , wherein the vent housing is formed from a single, homogeneous piece of a relatively rigid material.

15. The vent system of claim 14 , wherein the relatively rigid material is polycarbonate.

16. The vent system of claim 8 , wherein the outer wall, the inner wall, the inner base, the outer base, and the membrane are circular.

17. The vent system of claim 16 , wherein the outer wall, the inner wall, the inner base, the outer base, and the membrane are concentric.

18. The vent system of claim 1 , wherein the membrane is not attached to the vent housing such that the membrane is freely movable towards and away from the base.

19. The vent system of claim 1 , wherein, the HME, including the HME housing and the HME material, are removable from the cavity.

20. A patient interface comprising:

a seal-forming structure comprising a sealing flange configured to contact and seal against the patient's face in use;

a plenum chamber joined to the seal-forming structure;

a positioning and stabilising structure comprising a strap configured to secure the patient interface on the patient in use; and

the vent system of claim 1 .

21. The patient interface of claim 20 , further comprising a vent connector tube connected to the vent housing connector at the outlet opening to fluidly connect the vent system to the plenum chamber.