Duration of tracheal sound recorded during forced expiration: From a model to establishing standards

Analysis of the duration of tracheal sound recorded during forced expiration (TSFE) was performed to detect bronchial conductance disorders and to develop a method for establishing individually tailored standards. A standard individual duration of the TSFE served as an estimate of the relevant expiratory resistance of the bronchial tree in healthy subjects and showed the extent to which sound duration exceeded that predicted from the normal individual resistance in flow-limited subjects.