Effect of lung inflation on bronchial dimensions in the dog

Abstract

Bronchial diameters and lengths were measured from bronchograms of separate lobes of dogs' lungs. The lobes were initially completely airless, and radiographs were taken at intrabronchial pressures of 10 and 20 cm H2O at stages during inflation of the lobe. The bronchi were dissected out, made airtight, and radiographs taken at different distending pressures. In the intact lobe the increase in bronchial diameter occurred mainly at volumes below the functional residual capacity of the lobe. At greater degrees of inflation the diameters increased only slightly and in some cases were reduced. The bronchial lengths increased throughout inflation. Full inflation of the lung caused approximately a 60% increase in bronchial diameter and a 40% increase in bronchial length. Change of intrabronchial pressure from 10 to 20 cm H2O caused only 4% increase in bronchial diameters in the inflated lobe. Comparison with the same diameters in the isolated bronchus showed that the lung parenchyma exerts traction on the bronchial wall but the traction bears no simple relationship to the inflation volume. Submitted on January 18, 1962