Influences of hypoxemia and acidemia on left ventricular function

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Abstract
The purpose of this study was to systematically examine the influence of reduced arterial O2 tension on cardiac function at various controlled values of pH. The performance of the left ventricle was studied in a feline preparation which permitted control of aortic pressure, cardiac output, heart rate, and temperature. Arterial pH, PO2, and PCO2 were continuously measured with a Jewett flow-through electrode assembly. Reducing the arterial PO2 to 25-35 mm Hg by ventilating the animal with 6% O2 caused minimal reduction of left ventricular contractility (VC) when the pH was in the normal range. When arterial pH was reduced to 7.00 by infusion of HC1 or lactic acid no deterioration of cardiac function was observed at normal PO2. However, reduction of PO2 to the same range at pH 7.00 produced a much greater diminution of VC. Elimination of CNS (central nervous system) function by vascular ligation was associated with a greater reduction of VC during hypoxemia at both normal and reduced pH values. It si concluded that acidemia contributes to the reduction of VC during hypoxemia, and the CNS in part compensates for these changes.