CALIBRATED HYPOXEMIA TEST IN NORMAL SUBJECTS AND CORONARY PATIENTS

Abstract There is a great need for a calibrated test that can be used in coronary patients for diagnostic purposes and for evaluating the effect of drugs. A hypoxemia test with 7½% oxygen in nitrogen on mouthpiece, with continuous registration of the oxygen saturation of the blood, has been evaluated in 13 patients with coronary disease and in 5 normal subjects. The test usually gives a decline of the oxygen saturation of the blood to 70% or less, the level necessary to give a maximal positive response. The dispersion of oxygen saturation is rather great. During hypoxemia of short duration the heart rate and the cardiac output will increase, but will never compensate for the decline of oxygen saturation. The change in acid base equilibrium is very slight. No significant change of BP occurred during hypoxemia. The degree of oxygen saturation will therefore give a good indication of the coronary strain and may provide a reproducible and calibrated test for use in coronary insufficiency.