Patent Publication Number: US-2011067698-A1

Title: Handheld device for delivering continuous positive airway pressure

Description:
TECHNICAL FIELD 
     The invention relates to a hand held CPAP device for providing a continuous positive airway pressure where pressure is generated by a flow of gas from a demand valve by the interaction of an adjustable compression spring compressing the demand valve actuating diaphragm 
     BACKGROUND TO THE ART 
     Continuous Positive Airway Pressure (CPAP) is used for a number of applications in assisting patients with respiratory difficulties (such as Pulmonary Edema) or for persons suffering from sleep apnea. In the pre-hospital emergency market CPAP is becoming a primary treatment option for many respiratory impaired patients. Current CPAP devices are large, cumbersome and heavy. The invention that is the subject of this application is lightweight and handheld. 
     DISCLOSURE OF THE INVENTION 
     The invention provides a device for providing a continuous positive airway pressure where the pressure is generated by a flow of gas from a demand valve. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The attached drawing is a sectional view along a plane through a central axis of the device 
     
    
    
     DESCRIPTION OF THE CURRENT INVENTION 
     The new device utilizes a simple rotating control ( 1 ) to interface with a threaded member ( 2 ) which rotates within a housing ( 11 ) to compress a spring ( 3 ) against a diaphragm ( 4 ) which in turn depresses a tilt lever ( 5 ) within the body of the device to open a jet orifice ( 6 ). The flow of gas from the jet orifice lowers the pressure in the control chamber ( 7 ) producing a flow of gas from the demand valve ( 8 ). This gas flow passes through conduit ( 9 ) to a circuit means to deliver the flow to a facemask attached to a patient (not shown). The constant flow of gas from the demand valve creates a positive pressure within the facemask. 
     On inspiration by the patient a conduit ( 12 ) within the body of the demand valve allows negative pressure to build up in tilt lever chamber ( 13 ) below the diaphragm which draws the diaphragm ( 4 ) downwards against the tilt lever ( 5 ) increasing the flow of gas from the jet orifice ( 6 ), dropping the pressure further in control chamber ( 7 ) and providing an increased flow of gas from demand valve ( 8 ) equivalent to that demanded by the patient. Because jet orifice ( 6 ) is already opened by the actuation of the CPAP control, the negative pressure required to be generated is lower than that normally required to “crack” the tilt lever seal on the jet orifice thereby not allowing the pressure to enter a negative phase providing the CPAP pressure. 
     To prevent a dangerous build up of pressure in the event of a device failure a pressure relief system ( 10 ) is incorporated into the design.