Pulmonary circulation and respiration in hypoxic and circulatory hypoxias

Abstract

The linear and volumetric blood flow velocity in left low-lobar pulmonary artery and vein, the balance between cardiac output of right and left ventricles, as well as the blood pressure in pulmonary and femoral arteries, respiratory movements of the chest in hypoxic (3-5% O2 in nitrogen) and circulatory (acute hemorrhage) hypoxia were studied by ultrasonic method in acute experiments in cats under nembutal narcosis. It was shown that under the influence of severe hypoxic hypoxia the blood pressure in the pulmonary artery and the pulmonary vascular resistance increased; in the majority of the experiments, respiratory standstill without transitional stages occurred within 3 to 20 minutes. In circulatory hypoxia, the development of respiratory disorders was gradual with the appearance of pathological types of respiration such as apneusis and gasping occurring with a drop of systemic blood pressure to 30-40 mmHg, lowered pulmonary AP and 3-10-fold increased pulmonary vascular resistance. In hypoxic hypoxia the cardiac output changed insignificantly, without changes in the balance between cardiac output of the right and left ventricles. Only in the general circulation was observed. In circulatory hypoxia with decreased cardiac output redistribution of the blood to the general circulation occurred from the very beginning of the hemorrhage. Reinfusion of the autoblood restored the balance between the cardiac output of the right and left ventricles. The index of the capillary perfusion in the lungs decreased in parallel with a decrease of the pulmonary blood pressure. The index of capillary perfusion in hemorrhage decreased in parallel with a decrease of the pulmonary AP.