Breath sounds and distribution of pulmonary ventilation

A phonocardiograph and microphone fixed on the chest wall, have been used to record normal breath sounds at controlled lung volumes and flow rates in different lung zones and body positions. Breath sounds intensity varied with lung volumes, flow rate, body position and the site of recording on the chest wall. In upright position, as well as the lateral decubitus position, the relative intensity of breath sounds was always maximal at low lung volumes when recorded at the upper parts of the lung, but this maximum was reached at higher lung volumes when recorded at dependent parts of the lung. Our results correlate well with the differences in regional distribution of ventilation studied with radioactive gases.