Interactions between permeability and hydrostatic pressure in perfused dogs' lungs.

To evaluate interactions between increased permeability of the pulmonary vasculature and increased hydrostatic pressure on lung fluid flux, we measured water and blood contents of five equally thick slices of in situ perfused dogs' lungs that had been vertically suspended and, after experimental manipulations, rapidly frozen. Measurements were made under four sets of conditions (4 dogs each): 1) control; 2) increased left atrial pressure (Pla), 25 cmH2O relative to the bottom of the lung; 3) oleic acid; and 4) oleic acid and increased Pla. Significant interactions on lung water content were found between 1) oleic acid and increased Pla (P less than 0.005) and 2) oleic acid and height of the slice of lung (P less than 0.003). Blood content was significantly affected by interactions between 1) oleic acid and height of the lung slice (P less than 0.001) and 2) increased Pla and height of the lung slice (P less than 0.001). We conclude that there are significant interactions between increased permeability and hydrostatic pressure that affect regional lung water content and intrapulmonary distribution of blood.