OXYGEN DEFICIT INCURRED DURING HYPOXIA AND ITS RELATION TO EXCESS LACTATE

The oxygen deficit incurred during hypoxia was compared to the peak excess lactate XL level in order to see if any consistent relationship existed when a known oxygen limitation was imposed. Twelve anesthetized dogs, in which ventilation was held constant, breathed 9.1 O2 in N2 for 10, 20, and 30 minutes. Oxygen uptake was measured every 10 minutes during a control period, hypoxia, and a recovery period. Oxygen content and tension of systemic and pulmonary arterial blood were measured at the end of each of these periods. Excess lactate was calculated from blood lactate and pyruvate levels measured during the control period, the last minute of hypoxia, the first minute of recovery, and at intervals thereafter. Depletion and repletion of oxygen stores were estimated by assuming values on a body-weight basis for functional residual volume, body water, total blood volume, and its distribution. True O2 deficit and true excess O2 of recovery were thus calculated and compared to each other and to peak XL values. Excess O2 uptake measured during recovery, which is the oxygen debt as usually measured, never was as great as the oxygen deficit incurred during hypoxia, and bore little consistent relationship to peak XL. The true O2 deficit, on the other hand, had a coefficient of correlation of .781 when compared with peak XL.