EFFECT OF CHRONIC HYPOXIA ON HEMODYNAMICS, ORGAN BLOOD-FLOW AND O-2 SUPPLY IN RATS

Aortic blood flow, heart rate, blood pressure and blood flow distribut ion were measured in 10 chronically hypoxic rats (3 weeks, PB 370-380 Torr) breathing 10% O2 (chronic hypoxia) and after 30 min of breathing air (acute normoxia). Controls were 10 normoxic littermates breathing air (normoxia) and 10% O2 for 30 min (acute hypoxia). Acute hypoxia r esulted in increased aortic blood flow and heart rate, and decreased t otal peripheral resistance. Blood flow and oxygen supply to vital orga ns increased, indicating that blood flow redistribution plays an impor tant role in oxygen supply. In chronic hypoxia, aortic blood flow and heart rate remained elevated, and total peripheral resistance remained decreased. Blood flow distribution returned towards normoxia levels. Oxygen supply was maintained via increased arterial oxygen concentrati on. Acute normoxia resulted in decreased aortic blood flow and heart r ate, and increased blood pressure and total peripheral resistance. Blo od flow distribution was similar to that of chronic hypoxia except ske letal muscles, in which blood flow decreased markedly. Oxygen supply r emained unchanged or increased.