EXPONENTIAL ANALYSIS OF LOBAR PRESSURE-VOLUME CHARACTERISTICS

In 19 excised left human lungs, 7 of which were emphysema-free, lobar pressure-volume (P-V) characteristics were analyzed by fitting to the P-V data an exponential of the form V = A-Be-KPL (where V is the volume at a transpulmonary pressure [PL], A is the theoretical lung volume at infinite PL, B is the difference between A and the intercept of the fitted exponential on the volume axis and K is a shape constant). In emphysema-free lungs there was no difference in the B/A ratio expressed as a percentage, indicating an identical position of the P-V curves of the upper and lower lobes. Upper lobes had significantly (P < 0.025) higher values for K than the lower lobes indicating greater compliance. In 10 emphysematous lungs the upper lobes were more severely involved than the lower lobes. In these lungs the difference in K between upper and lower lobes was abolished, suggesting that the less emphysematous lower lobes had increased compliance relatively more than the upper lobes.