Prediction of maximal oxygen uptake at high altitude

The maximal oxygen uptake (VO 2 max) at high altitude is a key quantity in alpine medicine but has not been explained yet in terms of physiological parameters – ventilation, cardiac frequency, PvO 2 and inhaled gas O 2 pressure. Here, a novel theoretical approach (Kang, M.-Y. et al. Respir. Physiol. Neurobiol. 2015; 205:109-119) is used to predict the altitude dependence of VO 2 max on the above parameters values. By solving interactively the equations for O 2 convection-diffusion in airways and O 2 saturation in the pulmonary capillaries, the method yields the corresponding values of VO 2 max. Using a quadratic fit of ventilation and perfusion data from literature (see the figure inset) and under the condition PvO 2 = 20 mmHg, VO 2 max at different altitudes is computed. In the figure, it is shown as a percentage of sea level value. The predicted VO 2 max, shown in red, has a curvilinear decrease with increasing altitude, which exhibit very good agreement with experimental data. Both prediction and experiments gives around 80% decrease in VO 2 max at Mt. Everest altitude. Further investigation shows that the role of ventilation on VO 2 becomes much more significant at high altitude. This explains why hyperventilation is the most important feature of acclimatization to altitude (West, Integr. Comp. Biol . 2006; 46:25-34).