Effect of capillary pressure and plasma protein on development of pulmonary edema

Abstract

In 23 isolated, perfused dog lung preparations, the pulmonary capillary pressure was elevated to various levels up to 45 mm Hg and maintained for 1 hr. during the course of perfusion. The effect of these pressures on the accumulation of edema fluid was then studied. Edema was estimated by determining the ratio of the weight of the wet lung to the weight of the same lung after drying. In lungs perfused with blood having normal plasma protein concentrations, fluid began to transude into the lungs when the pulmonary capillary pressure exceeded 28 mm Hg. In another series, the plasma protein concentrations were reduced by dilution of the perfusing blood with isotonic saline solution to effect a decrease in colloid osmotic pressure to one-half normal. In these lungs, fluid began to transude into the tissues at a correspondingly lower level of capillary pressure. Furthermore, the rate at which fluid accumulated in the lungs, in both series of experiments, was directly proportional to the rise in capillary pressure above the cirtical pressure at which fluid began to collect in the lungs.