Lung Lesions in Experimental Hydrostatic Pulmonary Edema: An Electron Microscopic and Morphometric Study

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Abstract
Distinct barrier lesions and an apical-basal distribution of alveolar edema fluid in either moderate or high elevated pressure edema lungs have been found in previous studies. In the present study, quantitative measurements were obtained by using electron microscopy and morphometry of extravascular lung water and barrier lesions, on the relations between interstitial and alveolar edema fluid as well as between extravascular lung water and barrier lesions. The study further addressed the question of whether 6% bovine serum albumin (BSA) perfusion could induce lung ultrastructure alterations. It was found that interstitial fluid distribution is similar to that of alveolar edema fluid. Epithelial blebs are also distributed with an apical-basal gradient, and are always submerged in alveolar edema fluid. Perfusion with 6% bovine serum albumin does not induce any lung ultrastructure alterations. The results indicate that endothelium and epithelium play a different role in controlling fluid movement between capillary and extravascular spaces and thus in preventing the formation of interstitial and alveolar edema. Because the interaction of cells and tissue must be taken into account, simple physiological models of pulmonary fluid exchange may not be adequate to explain pulmonary edema formation.