Oleic acid dose-related edema in isolated canine lung perfused at constant pressure

Fatty acid embolism of the lung results in pulmonary edema. Isolated lung lobes ventilated and blood perfused at constant pressure were treated with 1 (n = 6) or 45 microliter/kg body wt (n = 6 oleic acid or saline (n = 7). Lobe weight increase linearly over 1-3 h following oleic with regression slopes indicating a more rapid rate of weight gain at the higher oleic acid dosage. Total lobe weight gain was greater in the 45 than in the 1 microliter/kg group (0.60 +/- 0.10 vs. 0.31 +/- 0.07 g/g initial lobe wt) and greater in the acid-treated lobes than in the controls (0.13 +/- 0.05 g/g initial lobe wt). Pulmonary vascular resistance increased 79% after 45 microliter/kg oleic acid but appeared unchanged following 1 microliter/kg oleic acid or saline. The decrease in arterial O2 partial pressure was greater in the 45 microliter/kg group than in the controls, 47 vs 22 Torr. High vascular pressures and increased flow velocities in patent vessels are not essential for oleic acid-associated edema, since weight increased at constant pressure perfusion. Weight gain related to oleic acid dosage suggests that oleic acid increases permeability by affecting the vascular endothelium either directly or through biochemical intermediates endogenous to the lung or blood.