Decreases in maximal oxygen uptake following long-duration spaceflight: Role of convective and diffusive O2 transport mechanisms

We have previously predicted that the decrease in maximal oxygen uptake (Vo2max) that accompanies time in microgravity reflects decrements in both convective and diffusive O2 transport to the mitochondria of the contracting myocytes. The aim of this investigation was therefore to quantify the relative changes in convective O2 transport (Qo2) and O2 diffusing capacity (Do2) following long-duration spaceflight. In nine astronauts, resting hemoglobin concentration ([Hb]), Vo2max, maximal cardiac output (QTmax), and differences in arterial and venous O2 contents (CaO2-CvO2) were obtained retrospectively for International Space Station Increments 19–33 (April 2009–November 2012). Qo2 and Do2 were calculated from these variables via integration of Fick’s Principle of Mass Conservation and Fick’s Law of Diffusion. Vo2max significantly decreased from pre- to postflight (–53.9 ± 45.5%, P = 0.008). The significant decrease in QTmax (–7.8 ± 9.1%, P = 0.05), despite an unchanged [Hb], resulted in a significantly decreased Qo2 (–11.4 ± 10.5%, P = 0.02). Do2 significantly decreased from pre- to postflight by –27.5 ± 24.5% (P = 0.04), as did the peak CaO2-CvO2 (–9.2 ± 7.5%, P = 0.007). With the use of linear regression analysis, changes in Vo2max were significantly correlated with changes in Do2 (R2 = 0.47; P = 0.04). These data suggest that spaceflight decreases both convective and diffusive O2 transpo...

Source: Journal of Applied Physiology - April 11, 2017 Category: Physiology Authors: Ade, C. J., Broxterman, R. M., Moore, A. D., Barstow, T. J. Tags: RESEARCH ARTICLE Source Type: research