Modelling lung and muscle oxygen diffusion capacities from sea-level to Mount Everest

Abstract

Abstract Lung and muscle oxygen diffusion capacities (DLO 2 and DMO 2 , respectively) are difficult to measure at maximal-intensity exercise and at altitude and they are scarcely reported in the literature, yet they are key components of the O 2 transport cascade. The goal of the present study was to compute DLO 2 and DMO 2 at simulated increasing altitudes between sea-level and Mount Everest. Literature data were compiled to compute DLO 2 and DMO 2 at maximal exercise using a forward iterative algorithm. These computations were repeated every 250 m of increasing altitude between seal level and the altitude of Mount Everest. Computed DLO 2 increased from sea-level to 5500 m and then decreased to the altitude of Mount Everest; yet remaining higher than sea-level values. DMO 2 increased from sea-level to 3500 m and then progressively decreased to values lower than sea-level. The computed variations in DLO 2 and DMO 2 fit with the ability of the lung and muscle to increase their diffusion capacity at altitude, which seemingly indicates an existing diffusion capacity reserve. The muscle reserve seems depleted at a lower altitude than the lung reserve. The clinical relevance of the proposed model requires further investigation.