The Alveolar-Capillary Membrane and Pulmonary Edema

Abstract

CONVENTIONAL teaching, based on light microscopy, has dealt with the physiopathology of pulmonary edema in terms of a simple barrier separating pulmonary capillaries from the alveolar spaces. According to this simplistic view, pulmonary edema represents the extravasation of a filtrate of plasma directly from pulmonary capillaries into alveoli as the result of one of two alternative mechanisms: an imbalance of forces operating across a normal alveolar-capillary barrier so that reabsorptive forces cannot cope with the high transcapillary filtration rates; or, despite normal transcapillary forces, excessive passage of plasma filtrate out of the capillary because of a breakdown of the barrier. . . .