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Contribution of oxygen extraction fraction to maximal oxygen uptake in healthy young men
Author(s) -
Skattebo Øyvind,
Calbet Jose A. L.,
Rud Bjarne,
Capelli Carlo,
Hallén Jostein
Publication year - 2020
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/apha.13486
Subject(s) - perfusion , blood flow , extraction (chemistry) , hypoxemia , fick principle , chemistry , medicine , hemodynamics , cardiac output , chromatography
We analysed the importance of systemic and peripheral arteriovenous O 2 difference ( a - v ¯ O 2difference and a‐v f O 2 difference, respectively) and O 2 extraction fraction for maximal oxygen uptake (V ˙ O 2max ). Fick law of diffusion and the Piiper and Scheid model were applied to investigate whether diffusion versus perfusion limitations vary withV ˙ O 2max . Articles ( n = 17) publishing individual data ( n = 154) onV ˙ O 2max , maximal cardiac output ( Q ˙ max ; indicator‐dilution or the Fick method), a - v ¯ O 2difference (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.Q ˙ max and two‐LBF increased linearly by 4.9‐6.0 L · min –1 per 1 L · min –1 increase inV ˙ O 2max ( R 2 = .73 and R 2 = .67, respectively; both P < .001). The a - v ¯ O 2difference increased from 118‐168 mL · L –1 from aV ˙ O 2max 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 increasingV ˙ O 2max ( R 2 = .17; P < .001), systemic O 2 extraction fraction increased up to ~90% (V ˙ O 2max : 4.5 L · min –1 ) with no further change (exponential decay model: R 2 = .42). Likewise, leg O 2 extraction fraction increased withV ˙ O 2max to approach a maximal value of ~90‐95% ( R 2 = .83). Muscle O 2 diffusing capacity and the equilibration index Y increased linearly withV ˙ O 2max ( 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 toV ˙ O 2max , enhanced O 2 extraction fraction (≥90%) contributes to the remarkably highV ˙ O 2max in endurance‐trained individuals.