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

Abstract

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 pO 2 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 pO 2 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 pO 2 . Severe heart failure occurred when the blood in the carotid arteries was moderately hypoxic (pO 2 below 50, sat. below 80%) while the rest of the circulation was fully oxygenated.