A spirometer having a housing with an elongated flow chamber open at one end, a pressure sensing end opposite the open end and an outlet passageway intercepting the flow chamber at an angle .alpha. and proximate the pressure sensing end. A differential pressure sensor is coupled to the pressure sensing end from a port at an angle .beta. to an axis of the flow chamber. The angle .alpha. is substantially greater than 0.degree. but substantially less than 180.degree. while the angle .beta. may range from 90.degree. to 180.degree., such that a significantly increased measured air pressure results over that measured when .alpha.=180.degree. and .beta.=90.degree..