Behavior of pulmonary hypertension produced by serotonin and emboli

¹ Departments of Medicine and Pathology, Peter Bent Brigham Hospital, and Harvard Medical School, Boston, Massachusetts

Pulmonary hypertension was produced in 25 dogs by infusion of serotonin, lycopodium spores, or polystyrene spheres. Flow through one lung was doubled by balloon occlusion of the opposite pulmonary artery, and the changes in calculated pulmonary vascular resistance of the unoccluded lung were observed. In the presence of pulmonary hypertension produced by serotonin, balloon occlusion produced a 51% fall of pulmonary vascular resistance in the unoccluded lung. A similar result was obtained with hypertension produced by small precapillary emboli 28 µ in diameter. Resistance fell 47% with occlusion of one artery. These results suggested that vasodilatation had occurred in the unoccluded lung. When pulmonary hypertension was produced by larger spheres, the fall of resistance seen in the unoccluded lung was only 18%. Significant vasodilatation had not occurred. The findings suggest active control of pulmonary vascular resistance by the precapillary arteriole.