Nasal interface
A nasal cannula for use in a system for providing a flow of respiratory gases to a user is described. The nasal cannula comprises a body made from a pliable material. The body has an inlet and at least one nasal prong fluidly connected to the inlet. In use a conduit providing a flow of gases to the cannula is connected to the inlet, and the nasal prong is inserted into a user's nostril. The cannula is arranged to direct the flow of gases from the nasal prong towards the front wall of the user's nasal passage within the user's nose.
1. A nasal interface for use in a system for providing a flow of respiratory gases to a user, the nasal interface comprising:
a body made from a pliable first material, the body comprising an inlet configured to receive a flow of gases and at least one nasal outlet, the at least one nasal outlet comprising a tubular structure configured to interface with a user's nostril, the at least one nasal outlet being fluidly connected to the inlet, wherein at least one plastically deformable member is attached to or integrally formed with the body, the at least one plastically deformable member having an elastic limit less than the elastic limit of the pliable first material; and
a flow restrictor comprising a member coupled to the body in a fixed position, the flow restrictor blocking a center of the flow of gases through the body and defining a gradually reducing cross sectional flow area such that all flow into and through the body passes through and is thereby restricted by the flow restrictor, wherein the flow restrictor is a dominant flow restriction of all gases flow in the system.
2. A nasal interface as claimed in claim 1 , wherein the at least one plastically deformable member is integrally formed with the pliable first material in a wall of the at least one nasal outlet.
3. A nasal interface as claimed in claim 1 , wherein the body comprises two side arms, each side arm extending from a side of a central portion of the body configured to pass across a user's upper lip region, and
the at least one plastically deformable member is integrally formed with the pliable first material of both side arms and configured to extend across the user's upper lip region.
4. A nasal interface as claimed in claim 1 , wherein the at least one plastically deformable member is a metal wire.
5. A nasal interface as claimed in claim 1 , wherein the at least one plastically deformable member is a metal strap.
6. A nasal interface as claimed in claim 1 , wherein the nasal interface is a nasal cannula, the at least one nasal outlet is a nasal prong configured for insertion into a user's nostril.
7. A nasal interface as claimed in claim 1 , wherein the at least one nasal outlet is a nasal pillow configured to provide a seal against a user's nostril.
8. A nasal interface as claimed in claim 1 , wherein the flow restrictor is disposed within the inlet of the body.
9. A nasal interface as claimed in claim 8 , wherein the flow restrictor is bullet shaped and coaxial with the inlet of the body.
10. A nasal interface as claimed in claim 8 , wherein a cross-section of the flow restrictor gradually decreases along an axial direction.
11. A nasal interface as claimed in claim 1 , wherein the flow restrictor is conical.
12. A nasal interface as claimed in claim 1 , wherein the flow restrictor decouples the flow of gases downstream of the flow restrictor from the flow of gases upstream of the flow restrictor.
13. A nasal interface as claimed in claim 12 , wherein the flow restrictor decouples the flow of gases such that any variation in resistance to the flow of gases downstream of the flow restrictor does not affect the operation of a gases source unit.
14. A nasal interface as claimed in claim 13 in combination with a gases source unit connected to the inlet of the body.
15. A nasal interface for use in a system for providing a flow of respiratory gases to a user, the nasal interface comprising:
a gas flow path assembly defining a gas flow path from a gas source to a user in use, the gas flow path assembly comprising:
gas supply conduit having a gas conduit inlet end configured to receive gas from the gas source and a gas conduit outlet end;
a patient interface comprising an interface inlet connected to the gas conduit outlet end and a body made from a pliable first material, the interface inlet configured to receive a flow of gases from the gas supply conduit, the patient interface also comprising at least one nasal outlet comprising a tubular structure configured to interface with a user's nostril, the at least one nasal outlet being fluidly connected to the inlet; and
a flow restrictor comprising a member coupled to the gas flow path assembly in a fixed position in the gas flow path, blocking a center of the gas flow path and defining a gradually decreasing cross section of the gas flow path such that all of a flow of gas through the gas flow path into the patient interface passes through the flow restrictor and is thereby restricted by the flow restrictor, wherein the flow restrictor is a dominant flow restriction of all gases flow in the system.
16. A nasal interface as claimed in claim 15 , wherein the flow restrictor extends across a diameter of the gas flow path.
17. A nasal interface as claimed in claim 15 , additionally comprising a plurality of support members extending outwardly from the fixed member and supporting the fixed member.
18. A nasal interface as claimed in claim 17 , wherein the plurality of support members comprise a plurality of spokes.
19. A nasal interface as claimed in claim 15 , wherein the fixed member defines an annular passage around the fixed member within the gas flow path.
20. A nasal interface as claimed in claim 15 , wherein the flow restrictor is conical.
21. A nasal interface as claimed in claim 15 , wherein the flow restrictor has an upstream end with a first cross section and a downstream portion with a second cross section that is larger than the first cross section, the upstream end being disposed so as to be closer to a gas source unit than the downstream portion in use.
22. A nasal interface as claimed in claim 15 , wherein the flow restrictor is bullet shaped and coaxial with the gas flow path assembly.
23. A nasal interface as claimed in claim 15 , wherein the flow restrictor is the dominant flow restriction of all gas flow in the gas flow path when a portion of the gas flow path assembly is squashed or pinched in use.
24. A nasal interface as claimed in claim 15 , wherein the flow restrictor decouples the flow of gas downstream of the flow restrictor from the flow of gas upstream of the flow restrictor.
25. A nasal interface as claimed in claim 24 , wherein the flow restrictor decouples the flow of gas such that any variation in resistance to the flow of gas downstream of the flow restrictor does not affect the operation of the gas source.
26. A nasal interface as claimed in claim 25 in combination with a gas source unit, the gas source comprising the gas source unit.