Contribution of oxygen extraction fraction to maximal oxygen uptake in healthy young men
Øyvind Skattebo, José A. L. Calbet, Bjarne Rud, Carlo Capelli, Jostein Hallén
Abstract
Abstract We analysed the importance of systemic and peripheral arteriovenous O 2 difference ( difference and a‐v f O 2 difference, respectively) and O 2 extraction fraction for maximal oxygen uptake ( ). Fick law of diffusion and the Piiper and Scheid model were applied to investigate whether diffusion versus perfusion limitations vary with . Articles ( n = 17) publishing individual data ( n = 154) on , maximal cardiac output ( ; indicator‐dilution or the Fick method), difference (catheters or the Fick equation) and systemic O 2 extraction fraction were identified. For the peripheral responses, group‐mean data (articles: n = 27; subjects: n = 234) on leg blood flow (LBF; thermodilution), a‐v f O 2 difference and O 2 extraction fraction (arterial and femoral venous catheters) were obtained. and two‐LBF increased linearly by 4.9‐6.0 L · min –1 per 1 L · min –1 increase in ( R 2 = .73 and R 2 = .67, respectively; both P < .001). The difference increased from 118‐168 mL · L –1 from a of 2‐4.5 L · min –1 followed by a reduction (second‐order polynomial: R 2 = .27). After accounting for a hypoxemia‐induced decrease in arterial O 2 content with increasing ( R 2 = .17; P < .001), systemic O 2 extraction fraction increased up to ~90% ( : 4.5 L · min –1 ) with no further change (exponential decay model: R 2 = .42). Likewise, leg O 2 extraction fraction increased with to approach a maximal value of ~90‐95% ( R 2 = .83). Muscle O 2 diffusing capacity and the equilibration index Y increased linearly with ( R 2 = .77 and R 2 = .31, respectively; both P < .01), reflecting decreasing O 2 diffusional limitations and accentuating O 2 delivery limitations. In conclusion, although O 2 delivery is the main limiting factor to , enhanced O 2 extraction fraction (≥90%) contributes to the remarkably high in endurance‐trained individuals.