Breathing therapy aid

Claim 1

In a breathing aid system having a source of oxygen under pressure, a flow meter to control the flow rate of oxygen from said source and a face mask for a patient, the improvement in a device for regulating the concentration of oxygen provided to the face mask comprising: a first end portion having an inlet port and adapted to be connected to the controlled flow of oxygen, a second end portion having an outlet port and adapted to be placed in communication with the face mask, an annular center portion between said inlet and said outlet portions, said center portion having a side wall with first and second ports, a sleeve mounted for circumferential rotation on said center portion, said sleeve having first and second side wall openings, the overlap between said ports on said center portion and said openings on said sleeve varying as a function of the circumferential position of said sleeve on said center portion, a flange extending outwardly from one end of said center protion, a spring at the other end of said center portion positioned between said sleeve and one of said end portions and urging said sleeve against said flange, one of said flange and said sleeve having a tab extending toward and in contact with the adjacent end of the other of said sleeve and said flange, the other of said sleeve and said flange having a series of notches adapted to mate with said tab to hold said sleeve in a circumferential position determined by the particular one of said notches which is set at said tab.