Jim M Adams: Expiratory flow meter. Projects in Health, Wolder Gross & Yavner, June 19, 1979: US04158360 (28 worldwide citation)

A peak expiratory flow meter device for indicating airway obstruction in a patient. The device includes an elongated channel arranged perpendicularly to a mouthpiece, at the end of which an adjustable orifice is disposed. A float moves within the channel in response to expiration from the patient. A ...