Measurement of bronchial elastance in resected sheep lungs.

The elastance of bronchial segments in resected sheep lungs has been measured by the following method. A balloon mounted on a probe was introduced into a bronchus of 3-4 mm diameter, the elastance of the balloon itself having been determined previously. The changes in pressure in the balloon resulting from the addition of successive small volumes of saline to the balloon were recorded, and the slope of the resulting pressure/volume curve gave the elastance of balloon and bronchus. The bronchial elastance was found by subtracting the elastance of the balloon from the combined value. Estimates of bronchial elastance derived from repeated inflations of the balloon during a single insertion showed little variation. Considerable variation was found between bronchi in the same animal and between animals, the elastance ranging from 1·1 to 3·4 cm HO/μ1 in the 25 bronchi studied. Repeated insertion of the balloon into the same bronchus was accompanied by a progressive increase in elastance; possible causes for this are discussed. It is hoped that the method may be applicable in man.