Lung sounds in patients with emphysema.

Abstract

We recorded an index of breath sound intensity (Ib) and the transmission of white noise (Tn) over four lung regions between apex and base in eight subjects with emphysema. The Ib and Tn were recorded over the whole range of lung volume from residual volume to total lung capacity. Each value was expressed as a fraction of the value recorded over the apical region with the help of an analog divider. The ratio of Ib to Tn was computed to correct for differences in Ib due to differences in transmission of sound. The ratio of Ib and Tn was computed to correct for differences in Ib due to differences in transmission of sound. The ratio of Ib to Tn was also expressed as a fraction of the value recorded over the apex. Both Ib and Tn had definite patterns in subjects with emphysema but varied considerably from breath to breath. The Ib and Tn were more reproducible in normal subjects. The magnitude and the sequence of Ib, Tn, and Ib/Tn were also different in subjects with emphysema and normal subjects. The ratio of Ib to Tn is an index of sound production in both normal subjects and subjects with emphysema. We conclude that both production and transmission of breath sounds vary from breath to breath in patients with emphysema. There are areas of both increased and decreased production and transmission of sound. If regional breath sound production (Ib/Tn) is related to regional ventilation in persons with emphysema as in normal subjects, these findings further suggest that regional ventilation varies from breath to breath and is also altered drastically from the normal pattern, leading to a severe ventilation and perfusion inequality so characteristic of emphysematous lungs.