Effect of Elevated Left Atrial Pressure and Decreased Plasma Protein Concentration on the Development of Pulmonary Edema

Abstract

In 97 dogs left atrial pressure was elevated to various levels up to 50 mm. Hg by partial constriction of the aorta. The effect of these pressures for from 30 min. to 3 hours on the accumulation of lung edema 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 animals with normal plasma protein concentrations fluid began to transude into the lungs when the left atrial pressure rose above an average of 24 mm. Hg. In another series of animals the plasma protein concentrations were reduced by plasmapheresis at the beginning of each experiment until the plasma protein concentration averaged 47 per cent of the control value. In these animals fluid began to transude into the lungs when the left atrial pressure rose above a critical value of 11 mm Hg. Furthermore, the rate at which fluid accumulated in the lungs, in all series of experiments, was directly proportional to the rise in left atrial pressure above the critical pressure at which fluid began to collect in the lungs.