Reduction of myocardial reactive hyperemia during oxygen breathing in dogs

In 7 open-chest anesthetized mongrel dogs the left anterior descending coronary artery was occluded for 20 sec. Myocardial reactive hyperemia was recorded during air and oxygen breathings. The excess blood flow during the reactive hyperemia was smaller and the duration of the reactive hyperemia was shorter during oxygen breathing than during air breathing. It is suggested that the reduction of oxygen demand during oxygen breathing is a possible reason for the decreased reactive hyperemia and oxygen administration is beneficial in relieving myocardial ischemia.