Screen filtration pressure and pulmonary hypertension

Abstract

A series of experiments was devised to test the resistance to flow through the lungs of blood samples with different screen filtration pressures (SFP). The pulmonary artery and left atrial presures were measured in dogs rendered acutely hypotensive by rapid bleeding, and in others subjected to severe soft tissue trauma. Following acute hypotension the SFP always increased before and more markedly in the pulmonary artery than it did in femoral artery or vein blood. In other dogs similar measurements were made in normotensive dogs perfused with blood having a high screen filtration pressure. In each of these series of experiments the pulmonary artery pressure and difference between it and the left atrial pressure increased when the blood of the animal developed a high SFP (during hypotension and after trauma), or when high SFP blood was infused into the animal. It was suggested that the high SFP was due to adhesive and aggregated blood cells, especially platelets and leukocytes, and that these aggregates had occluded numerous blood conduits of the lungs.