The forced expiratory wheeze. Its site of origin and possible association with lung compliance

When a subject exhales forcefully, a wheeze is usually heard during the latter part of the maneuver. The origin and mechanism of this wheeze has been the subject of speculation but this has never been approached experimentally. In this study, a computerized frequency analysis technique was used to count the number of discrete frequency components making up the forced expiratory wheeze (FEW) in 10 normal subjects. The number varied from 1 to 5 implying a source in the larger airways. The supports previous theoretical considerations that relate the FEW to the so-called "equal pressure point" (EPP) in the larger airways. Since the EPP is thought to be determined principally by lung static recoil pressure, it can be surmised that this also determines (roughly) the number of wheeze components in the FEW.