Breath sounds and distribution of pulmonary ventilation.

Abstract

A phonocardiograph and microphone were used to record normal breath sounds in different lung zones at controlled lung volumes and flows and body positions. Breath sound intensity varied with lung volume, flow, body position, and the site of recording on the chest wall. At a given inspiratory flow, in various body positions, the maximal relative intensity of breath sounds was always recorded at low lung volumes over superior regions, but the maximum occurred over inferior regions of the lung at larger lung volumes. The results correlated well with the differences in regional distribution of ventilation found with radioactive gases.