Effects of arterial hypoxia on the heart and circulation: an integrative study

¹ Department of Medical Research, St. Joseph Hospital, and Lockheed Aircraft Corporation, Burbank, California

An integrative series of investigations progressed from simplified systems, where cause-and-effect relations were relatively clear, to the virtually intact animal with separately perfused carotid arteries. Arterial pO₂ below 40 mm Hg (about 75% oxygen saturation) caused edema of the heart muscle; however, the contractile strength and performance of isolated hearts were compromised severely only when the arterial pO₂ had fallen below 15 mm Hg (about 25% saturation). The ‘acute circulatory crisis" which is known to occur when the arterial oxygen saturation falls below 80% was not caused by weakness of the heart muscle but by reflexes from the carotid artery territory: even when the oxygen saturation of systemic arterial blood had fallen as low as 50% this did not cause heart failure as long as the carotids were perfused with blood of normal pO₂. Severe heart failure occurred when the blood in the carotid arteries was moderately hypoxic (pO₂ below 50, sat. below 80%) while the rest of the circulation was fully oxygenated.

Key Words: myocardial edema • acute heart failure • carotid artery reflex • heart muscle contractile strength • arterial pO₂

Submitted on November 13, 1962