Hypoxemia and Coronary Blood Flow12

Abstract

In experiments on open-chest dogs and on fibrillating heart preparations, reduction of O2 content of arterial blood produced increases in coronary blood flow only when coronary sinus O2 levels fell below about 5.5 volumes %. High perfusion pressures were employed in order to increase coronary flow to the extent that coronary sinus blood became relatively rich in O2. Under these conditions it was possible to demonstrate that moderate lowering of arterial O2 content does not decrease coronary resistance by a direct action on the vessel walls. Coronary vasodilation in hypoxemia appears to be related to myocardial hypoxia.