Spirometer accessory

Claim 1

An inlet for use with a spirometer responsive to the exhalation flow of breath gases from a patient, said inlet comprising an inlet tube having an inlet end for the entry of said exhalation flow and an outlet and for connection to the spirometer; a mouthpiece having a first and second end and an internal bore, said mouthpiece being in engagement at its first end with said inlet end of said inlet tube as an exhalation flow inlet thereto; an apertured valve seating member carried by said mouthpiece and being formed to extend across said bore; a valve diaphragm formed of thin flexible material, said diaphragm having a peripheral region, a central region and an intermediate region between said peripheral region and said central region; said valve seating member having an axially projecting outer rim and a diaphragm mounting means positioned within said outer rim, said diaphragm mounting means having a central mount and at least three radially extending spokes connected between said central mount and said sidewall for retaining said diaphragm by said central region thereof in an axial position such that said diaphragm flexes toward the outlet end of said inlet tube and said diaphragm lies in a first plane with said peripheral region of said diaphragm in sealing engagement with said outer rim; said spokes having cross-sections that provide laminar flow therearound in a direction from said first end to said second end of said mouthpiece to minimize flow resistance therethrough; said diaphragm mounting means further including inner members extending laterally from each of said spokes, said spokes and said inner members being axially displaced from said first plane in a direction toward the first end of said mouthpiece such that said inner members lie in a second plane parallel to and axially displaced from said first plane whereby, under zero flow conditions, said diaphragm lies in said first plane and engages only said outer rim and, under reverse flow conditions, said diaphragm distorts and engages said inner members at said intermediate region thereof thereby preventing disengagement of said diaphragm from sealing engagement with said outer rim.