Importance of mitochondrial PO2 in maximal O2 transport and utilization: A theoretical analysis

​In previous calculations of how the O₂ transport system limits V̇_O2max, it was reasonably assumed that mitochondrial P_O2 (Pm_O2) could be neglected (set to zero). However, in reality, Pm_O2 must exceed zero and the red cell to mitochondrion diffusion gradient may therefore be reduced, impairing diffusive transport of O₂ and V̇_O2max. Accordingly, we investigated the influence of Pm_O2 on these calculations by coupling previously used equations for O₂ transport to one for mitochondrial respiration relating mitochondrial V̇_O2 to P_O2. This hyperbolic function, characterized by its P₅₀ and V̇_MAX, allowed Pm_O2 to become a model output (rather than set to zero as previously). Simulations using data from exercising normal subjects showed that at V̇_O2max, Pm_O2 was usually < 1mmHg, and that the effects on V̇_O2max were minimal. However, when O₂ transport capacity exceeded mitochondrial V̇_MAX, or if P₅₀ were elevated, Pm_O2 often reached double digit values, thereby reducing the diffusion gradient and significantly decreasing V̇_O2max.

DOI: 10.1016/j.resp.2013.08.020

Importance of mitochondrial PO2 in maximal O2 transport and utilization.pdf