Abstract:
A pressure sensitive valve for a positive pressure airway system which allows bi-directional flow with low resistance. When positive pressure from the air generator of the positive pressure airway system is lost, a spring actuated disc moves away from its compressed position to block the outlet of the air generator. By blocking the outlet of the air generator, the path of entry for contaminants is significantly restricted in so doing, an alternate, low resistance path to atmosphere is exposed to allow contaminants to escape.

Description:
FIELD OF THE INVENTION 
     The present invention relates to providing a valve at the outlet of a positive airway pressure (PAP) device such as a continuous positive airway pressure (CPAP) device or bi-level positive airway pressure (BiPAP) device for preventing contaminants from entering the device. 
     BACKGROUND OF THE INVENTION 
     Sleep apnea syndrome is due to episodic upper airway obstruction during sleep. As a consequence, there is severe interruption of sleep in the patient. Positive airway pressure devices, such as CPAP, and bi-level positive airway pressure devices have been developed to treat this disorder. CPAP devices deliver positive air pressure to the nasal passages of patients during sleep in order to maintain their airways in a continuously open state. In BiPAP therapy, pressure is applied alternately at relatively higher and lower prescription pressure levels. 
     A typical PAP device comprises a flow generator (e.g., a blower) which receives air from any suitable source such as a pressurized bottle or the ambient atmosphere. The gas flow from the flow generator is passed via a delivery conduit to a patient interface, such as a mask. 
     Humidifiers have been developed for use with PAP devices to humidify the air supplied to the patient. A typical humidifier comprises a water reservoir connected in series with the delivery conduit between the flow generator and the patient interface. A problem associated with these humidifiers is the possibility of water from the humidifier entering the PAP device through the delivery conduit and potentially causing damage to the device. 
     Many PAP devices are also used in combination with a therapeutic gas such as oxygen which is generally delivered at the patient end of the delivery conduit. A problem associated with the use of therapeutic gas is when positive pressure from the flow generator is lost, the therapeutic gas will flow through the delivery conduit to the PAP device potentially causing damage to the device. 
     The pressure sensitive flow control valve of the present invention has been developed to overcome the problem of water from a humidifier and other contaminants from entering the PAP device by blocking the outlet of the PAP device to restrict the path of entry for the contaminants. Also, the valve prevents the flow of gas, in the absence of positive pressure, back into the PAP device or ventilator by providing a low resistance exit path to atmosphere for any gas or water in the patient circuit. 
     SUMMARY OF THE INVENTION 
     The principal advantage of the present invention is realized by providing a pressure sensitive flow control valve at the outlet of a PAP unit to prevent contaminants from entering the PAP unit when positive pressure is lost. 
     The present invention provides a pressure sensitive flow control valve for a PAP system. While the system is at pressure, the valve allows bi-directional flow with low resistance. When positive pressure is lost, a spring actuated disc moves away from its normal position to block the outlet of the PAP unit. This valve will allow reverse flow as long as there is sufficient pressure. However, if there is not adequate pressure in the valve, indicating that the PAP unit is not functioning, the valve acts much like a one way valve to prevent reverse flow. 
     The valve of the presently preferred embodiment of the present invention comprises a valve top cap, a valve bottom cap, a valve body disposed between the valve top cap and the valve bottom cap, a valve stem/disc and a spring. All of the components, with the exception of the spring, preferably are polycarbonate components ultrasonically welded together. But those skilled in the art will appreciate that other manufacturing materials and methods are possible. 
     Other details, objects and advantages of the present invention will become apparent as the following description of the presently preferred embodiments proceeds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become more readily apparent from the following description of preferred embodiments thereof shown, by way of example only, in the accompanying drawings, wherein: 
     FIG. 1 is a view schematically illustrating a PAP system incorporating the pressure sensitive valve of the present invention; 
     FIG. 2 is a perspective view of the pressure sensitive valve; 
     FIG. 3 is a side view of the pressure sensitive valve; 
     FIG. 4 is an end view of the valve illustrated in FIG. 3 as seen from line 4--4 of that figure; 
     FIG. 5 is an end view of the valve body as shown in the direction of line 5--5 in FIG. 3; 
     FIG. 6 is an exploded side view of the valve; 
     FIG. 7 is a cross-sectional side view of the valve illustrated in FIG. 4 as seen from line 7--7 of that figure illustrating the position of the disc in the absence of positive pressure; 
     FIG. 8 is a cross-sectional side view of FIG. 4 as seen from line 8--8 of that figure illustrating the position of the disc in the presence of positive pressure; and 
     FIG. 9 is a close-up view illustrating details of the disc. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning to the drawings, a schematic drawing of a PAP system 10 is shown in FIG. 1 which includes a flow generator 12 which delivers gas flow via a delivery conduit 14 to a patient interface 16 such as a mask. Typically a humidifier 18 is disposed in line with the delivery conduit 14 between the flow generator 12 and the patient interface 16. The patient interface 16 may include an inlet 19 for the administration of a therapeutic gas such as O 2 . In accordance with the present invention a pressure sensitive flow control valve 20 is located at the outlet of the flow generator 12 at the end of the delivery conduit 14 opposite the patient interface 16. 
     The details of a pressure sensitive flow control valve 20 in accordance with a presently preferred embodiment of the present invention are shown in FIGS. 2-9 The valve 20 includes a valve body 22, valve top cap 24, a valve bottom cap 26, a spring 28 and a valve stem/disc 30/32 as shown in FIG. 3. 
     The valve top cap 24, as shown in FIG. 3, is generally cylindrical in shape having a conical end 34 which attaches to the valve body 22. The valve top cap 24 acts as an outlet port to the valve. Valve bottom cap 26, which acts as a supply port to the valve, is also generally cylindrical in shape and has an annular flared portion 36 which attaches to the valve body 22. 
     The valve body 22, as seen in FIG. 6, is generally cylindrical in shape and has a top end 38 for attachment to the valve top cap 24 and a bottom end 40 for attachment to the valve bottom cap 26. Exhaust ports 42, as shown in FIGS. 5 and 8, extend radially from an internal conical chamber 44 to the outer surface of the cylindrical body 22. In the preferred embodiment three exhaust ports 42 are shown. Internal conical chamber 44 (FIGS. 5, 7 and 8) extends from the top end to the bottom end and has a central cylindrical guide 48 concentrically disposed within the internal conical chamber 44. The top end 50 of the central cylindrical guide 48 is closed and the bottom end 52 preferably is open such that a spiral spring 28 is insertable inside. The central cylindrical guide 48 preferably has three slits 54 (FIG. 5) which serve as guides for protrusions 56 on the valve stem/disc 30/32. The body 22 also preferably has horizontal ribs 58 on the outside of the body 22 to make it difficult to block the exhaust ports 42 with tape by an untrained user. 
     The valve stem/disc 30/32 has a stem portion which is adapted to fit inside the cylindrical guide 48 of the valve body 22. An end of the stem portion engages the spring 28 within the cylindrical guide 48, protrusions 56 on the valve stem portion project through the slits 54 in the central cylindrical guide 48 to guide the valve stem as it moves relative to the central cylindrical guide 48. The protrusions 56 are preferably in the form of two rows of fingers but may also be rib-like. 
     The spring 28 is preferably a spiral spring designed to provide adequately constant force throughout the travel range, giving the valve 20 a sharper response characteristic at precisely the desired pressure condition. The slits 54 are preferably offset 60° from the exhaust ports 42 to prevent unwanted tampering with the internal parts by users. 
     Integral with the valve stem portion is a valve disc portion located on an end opposite to the spring engaging end. The disc preferably has a centralized conical portion 59 and aerodynamic curves 60 (FIG. 9) to reduce flow resistance. 
     In normal operation, pressurized air from the PAP unit 10 enters the valve 20 through the valve bottom cap 26 and engages the disc against the work of the spring 28 (FIG. 8). The centralized conical portion and aerodynamic curves of the disk reduce flow resistance such that the pressurized air flows across the disc, around the outside of the internal conical chamber 44 and out through the valve top cap 24 which is connected to the delivery conduit 14 for delivery of the air to the patient through the patient interface 16. While the system is at pressure, the valve 20 also allows reverse flow into the positive airway pressure device. In the absence of pressurized air (FIG. 7), the spring 28 pushes the disc against the annular flared portion 36 of the valve bottom cap 26 to seal off the entry of air or any contaminants into the PAP unit 10. Air or contaminants which enter into the valve 20 when positive air pressure is lost, enter through the valve top cap 24, flow around the outside of the internal conical chamber 44, into the inside of the internal conical chamber 44 to exit the exhaust ports 42 which are open to atmosphere. 
     While a presently preferred embodiment is shown and described, many variations are within the scope of the present invention. For example, the disc may be formed from a flexible material or formed from a metal such that it may be actuated by pressure as well as magnetic attraction. A floating ball, which is movable back and forth may be used instead of a disk to block the outlet ports to the PAP unit and atmosphere. 
     Although the invention has been described for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited to the claims.