Estimation of expiratory efficiency of emphysematous lungs on the basis of anatomical findings.

Abstract

Expiratory efficiencies of individual autopsied lungs, normal and emphysematous, were calculated with the expressions for expiratory mechanics derived in our previous report. The estimation of the pertaining parameters was possible on anatomical findings and by histometrical treatments. Estimated quantities were: elasticity constant a, total lung volume in relaxation V0, the mean density of elastic system E, the standard deviation of the density of elastic system σ, and total airway resistance R. Emphysematous lungs were generally characterized by increased V0 and reduced E. Concomitant fibrosis elevated a. The evidence was presented that R was rather reduced in emphysematous lungs when expiration proceeded without participation of thoracic activity. Distinct deterioration of expiratory functions was demonstrated in all the examined emphysematous lungs. In extreme cases the expiratory efficiency was lowered to 20% of the normal value. The major cause of the disturbance was an increase of V0. The reduction of E also impaired expiratory function. Increased σ exerted only insignificant influence on expiratory efficiency, but it effected an increase of transalveolar flow. A rise in the value of a caused distinct elevation of intrapulmonary pressure at pulmonary expansion and improved expiratory efficiency. Enlarged thoracic cavities in emphysema also contributed to elevation of expired volume. These compensatory mechanisms could not, however, restore the expiratory efficiency in emphysema to the normal level.