The change in the peak frequency of forced expiratory wheezes in response to the bronchodilatation test

Abstract

The changes in the most prominent tracheal forced expiratory wheezes (FEW) and volumetric flow rates in response to the bronchodilatation test in 71 healthy volunteers and 69 patients with reversible bronchial obstruction have been evaluated. The absence of a decrease in FEW peak frequencies in the middle part of a forced expiration in response to the bronchodilatation test was typical for patients with bronchial obstruction but not for healthy subjects. The response of the peak value of middle-frequency (400–600 Hz) and early high-frequency (over 600 Hz) FEWs in the middle of forced expiration indicates that these sounds are generated by a forced flow and can be described by the vortex shedding model. The response of peak values of late high-frequency (over 600 Hz) FEWs provides evidence of self-oscillation involvement in the formation of these sounds independently from the flow.