Vent valve assembly

Abstract

A vent valve apparatus (10) for use with a system for supplying breathable gas pressurised above atmospheric pressure to a human or animal. The apparatus (10) includes a gas washout vent (15), a vent valve (18) adapted to progressively restrict the flow area of the washout vent (15), and a pressure sensitive vent valve control means (20,22,23). The control means is adapted to progressively cause the vent valve (18) to restrict the flow area of the gas washout vent (15) in response to increases in the pressure of the gas supply, thereby substantially regulating the volumetric flow of gas and/or CO.sub.2 gas through the washout vent (15) over a range of gas supply pressures.

Claims

1. A CPAP apparatus for supplying pressurized breathable gas to a patient, comprising: a flow generator structured to generate a supply of pressurized gas; a mask adapted to provide a seal with the patient's face; a conduit that interconnects the flow generator and the mask; and a vent valve apparatus for gas washout, the vent valve apparatus structured to control gas washout based on the pressure of the gas supply, wherein the vent valve apparatus includes a gas washout vent, a vent valve adapted to progressively move within the gas washout vent so as to progressively restrict the flow area of the gas washout vent, and a pressure sensitive vent valve controller adapted to progressively cause the vent valve to restrict the flow area of the gas washout vent in response to increases in the pressure of the gas supply, wherein the vent valve apparatus is structured to restrict gas washout in response to increases in the pressure of the gas supply.

2. The CPAP apparatus according to claim 1, wherein the vent valve apparatus is structured to expand gas washout in response to decreases in the pressure of the gas supply.

3. The CPAP apparatus according to claim 2, wherein the vent valve apparatus is structured to progressively expand gas washout.

4. The CPAP apparatus according to claim 1, wherein the gas washout vent and the vent valve include complementary shapes.

5. The CPAP apparatus according to claim 4, wherein the gas washout vent and the vent valve are cone-shaped.

6. The CPAP apparatus according to claim 1, wherein the vent valve apparatus is structured to progressively restrict gas washout.

7. The CPAP apparatus according to claim 1, wherein the flow generator is structured to generate pressurized gas in the range of about 4-22 cm H.sub.2O.

8. The CPAP apparatus according to claim 1, wherein the flow generator supplies pressurized gas at a constant pressure.

9. The CPAP apparatus according to claim 1, wherein the flow generator supplies pressurized gas at two levels in synchronism with patient breathing.

10. The CPAP apparatus according to claim 1, wherein the flow generator continuously varies the level of pressurized gas.

11. The CPAP apparatus according to claim 1, wherein the vent valve apparatus is provided to the conduit.

12. The CPAP apparatus according to claim 1, wherein the vent valve apparatus is provided to the mask.

13. The CPAP apparatus according to claim 1, wherein the mask includes a face mask, nose mask, or mouth mask.

14. The CPAP apparatus according to claim 1, wherein the vent valve controller includes an elastic diaphragm connected to the vent valve such that displacement of the diaphragm results in displacement of the vent valve.

15. The CPAP apparatus according to claim 1, wherein the vent valve controller includes an aerodynamic member connected to the vent valve and rotatably displaceable such that rotatable displacement of the aerodynamic member results in displacement of the vent valve.

16. A CPAP apparatus for supplying pressurized breathable gas to a patient, comprising: a flow generator structured to generate a supply of pressurized gas; a mask adapted to provide a seal with the patient's face; a conduit that interconnects the flow generator and the mask; and a vent valve apparatus for gas washout, the vent valve apparatus structured to control gas washout based on the pressure of the gas supply, wherein the vent valve apparatus includes a gas washout vent, a vent valve adapted to progressively move within the gas washout vent so as to progressively restrict the flow area of the gas washout vent, and a pressure sensitive vent valve controller adapted to progressively cause the vent valve to restrict the flow area of the gas washout vent in response to increases in the pressure of the gas supply, and wherein the vent valve apparatus is structured to expand gas washout in response to decreases in the pressure of the gas supply.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

(1) Preferred embodiments of the invention will now be described, by way of examples only, with reference to the accompanying drawings in which:

(2) FIG. 1 is a schematic sectional side view of a vent valve apparatus according to the first embodiment of the invention;

(3) FIG. 2 is a schematic sectional side view of a vent valve apparatus is according to a second embodiment of the invention; and

(4) FIG. 3 is a schematic sectional side view of a vent valve according to a third embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

(5) Referring to FIG. 1, there is shown a vent valve apparatus 10 according to a first embodiment of the invention. The vent valve apparatus 10 is connected to a mask 100 at 12. The mask is adapted to receive a continuous supply of gas 13 above atmospheric pressure from a flow generator 200 through a flexible conduit 14. The apparatus 10 includes a gas washout vent, in the form of a substantially conical orifice 15 formed in a wall 16 of the pipe branch 17, and a vent valve in the form of a substantially conical plug 18. The rim 19 of the orifice 15 acts as a valve seat for the plug 18. The apparatus 10 also includes a pressure sensitive vent valve control means which includes an elastic diaphragm 20 stretched over a circular orifice 22 of the branch 17, and a rigid wire rod 23 connecting the plug 18 to the centre of the diaphragm 20.

(6) In this embodiment, the plug 18 is conical and the orifice 15 is circular. In other embodiments (not shown), the plug and the orifice are other complimentary shapes.

(7) The orifice 15 provides an outlet for the removal of gas upon patient expiration. Gas removal is aided by the continuous flow of gas pressurised above atmospheric pressure flowing through the conduit 14 and to atmosphere through the orifice 15.

(8) As the air pressure in conduit 14 increases, corresponding increases occur in the air pressure adjacent diaphragm 20. These pressure increases cause diaphragm 20 to bulge to the position represented by phantom line 26. The displacement of the centre of the diaphragm 20 results in corresponding displacement in the plug 18, causing the plug 18 to be drawn into the orifice 15 thereby restricting the flow of gases through the vent orifice. In this way, the flow area of the vent is restricted at higher delivery pressures thereby reducing flow of gas through the orifice 15 compared to a fully open orifice.

(9) The apparatus can be calibrated by adjusting the length of the wire rod 23 between the plug 18 and the diaphragm 20.

(10) The vent valve apparatus 10 thereby maintains the airflow through the vent at, or at least near, the optimum safe minimum amount. This has the effect of reducing the noise produced at higher CPAP pressures, compared to the noise emitted by a similar orifice without the vent valve. A quieter vent improves patient and bed-partner comfort. An additional benefit provided by the invention is the reduction in the amount of wasted gas forced through the vent unnecessarily at higher CPAP treatment pressures.

(11) A prototype of the first embodiment of the invention shown in FIG. 1 has been tested over a range of CPAP treatment pressures utilising the present Applicant's Sullivan™ flow generator made by ResMed Limited and Sullivan™ mask frame (fitted with Series 3 Sullivan™ Bubble Cushion™) modified in accordance with the teaching of this invention. This prototype was also tested without the conical plug 18. The results of the tests are summarised in the table below:

(12) TABLE-US-00001 TABLE 1 Performance Comparison for Prototype Vent Valve Apparatus With and Without the Conical Plug With Without CPAP Pressure Air Flow Sound Pressure Air Flow Sound Pressure cmH20 1/m Level dB(A) 1/m Level dB(A) 4 11.2 34.1 11.9 36.1 10 14.4 46.8 19.5 48.4 18.5 9.0 52.7 26.7 55.7

(13) As the results show, the prototype vent valve according to the first embodiment of the invention maintained a substantially constant air flow through the vent over a wide range of CPAP treatment pressures compared to the large variation exhibited by a similar mask without the conical plug. Further, at all pressures, the noise produced by the mask using the vent valve apparatus according to the first embodiment of the invention was less than the same mask without the conical plug.

(14) Referring now to FIG. 2, there is shown a vent valve apparatus according to a second embodiment of the invention. Like reference numerals to those used in FIG. 1 will be used to indicate like features in FIG. 2. This second embodiment functions in the same way as the first embodiment in that an increase in pressure in the conduit 14 causes the diaphragm 20 to bulge and draw the plug 18 into the washout valve orifice 15, thereby restricting the flow of gas through that orifice.

(15) A third embodiment of the present invention is shown in FIG. 3. Once again, like reference numerals are used to indicate like features. This third embodiment includes an aerodynamic member, in the form of wing 30, which is disposed in conduit branch 17 and adapted to pivot about an axis transverse to the direction of the gas flow along the conduit branch 17. The wing 30 is connected to a pivot mechanism, indicated generally at 31, which includes a connecting rod 33 and pilot joint 34. The connecting rod 33 and pivot joint 34 operatively connects the plug 18 to the wing 30, is used to bias the wing 30 and plug 18 to a position where the flow area of orifice 15 is maximized. As gas supply 13 is forced through the conduit 14, branch 17 and over the wing 30, the wing generates lift which opposes the spring and causes displacement of the wing to the position shown by phantom line 37, thereby drawing plug 18 into orifice 15 as shown by phantom line 32 and, thereby reducing the flow area of the gas washout orifice 15. Accordingly, the higher the pressure and flow rate of air passing through the branch 17 of the conduit 14, the more lift is produced by the wing and the more the flow area of the washout vent orifice 15 is restricted.

(16) As with the earlier embodiments described above, this maintains a substantially constant air flow through the washout vent orifice.

(17) Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.