VI. The Energetic Significance of Lactate Accumulation in Blood at Altitude

Abstract

The O₂ equivalent of lactic acid accumulation in blood was estimated from data on ten subjects acclimatized to altitudes up to 6500 m in the course of a Mt. Everest expedition. The calculated value of the O₂ equivalent of La by standard least squares regression was 2.07 ± 0.41 O₂ for a rise of blood lactic acid concentration [La_b] of 1 g per liter of blood (2.92 ml O₂ per kg of body weight per 1 mM increase in blood lactate). This value, as well as the value obtained by the regression procedure suggested by Brace (2.84 ± 0.51), was not significantly different from the previously reported value of 2.38 ± 0.22 (14) for sea-level conditions. This finding indicated that, after La equilibrium is achieved, the redistribution of La among extra- and intracellular body compartments, as reflected by [La_b], appears not to be substantially affected by chronic hypoxia. The calculated maximum lactic O₂ debt values at the Mt. Everest base camp (5350 m) were 1.26 and 1.42 liters for acclimatized Caucasians and for Sherpas, respectively. The amount of the measured maximum O₂ debt at altitude was somewhat increased by pure O₂ breathing (1.53 vs 1.26 l).

Key words

altitude - lactate O₂ equivalent - O₂ debt