Calibrated Hypoxemia Test in Normal Subjects and Coronary Patients

Abstract

In 13 patients with angina pectoris and 5 normal subjects hypoxemia tests have been carried out, with continual registration of the arterial O2 saturation and ECG. A gradual depression of the T wave was found during hypoxemia in most cases. There was no difference in the pattern found in normal subjects and coronary patients. The S‐T depression during hypoxemia was not found in the normal subjects. In 6 patients with angina pectoris the S‐T change occurred in the course of 3–4 min, at somewhat differing degrees of saturation, depending on the degree of angina pectoris. When the mask was removed, the arterial saturation rose rapidly in the course of approximately 30–40 sec. In most cases the ECG was normalized before saturation was complete. In a few cases the ECG changes persisted for some minutes before full saturation occurred. On repeated tests in the same patient the S‐T changes occurred within the same saturation range. The deviation was, on the average, 2.4%. On administration of nitroglycerine the tolerance of the myocardium to hypoxemia increased, the S‐T depression occurring only at considerably lower degrees of saturation and normalization occurring more rapidly. It therefore seems that a calibrated hypoxemia test with continuous O2 registration is capable of giving a standardized and reproducible registration of the degree of coronary insufficiency. This test will also permit the registration of the effect of medication on coronary insufficiency.