Evidence for tissue diffusion limitation of VO2max in normal humans

摘要: We recently found [at approximately 90% maximal O2 consumption (VO2max)] that as inspiratory PO2 (PIO2) was reduced, VO2 and mixed venous (PVO2) fell together along a straight line through the origin, suggesting tissue diffusion limitation of VO2max. To extend these observations to VO2max directly examine effluent blood from muscle, six normal men cycled at while breathing air, 15% 12% in random order on single day. From femoral venous, radial arterial samples, we measured PO2, PCO2, pH, lactate computed mean muscle capillary by Bohr integration between (PaO2) (PfvO2). CO2 production (VCO2) were expired gas analysis, averaged 61.5 +/- 6.2 (air), 48.6 4.8 (15% O2), 38.1 4.1 (12% O2) ml.kg-1.min-1. Corresponding values 16.8 5.6, 14.4 5.0, 12.0 5.0 Torr for PfVO2; 23.6 3.2, 19.1 4.2, 16.2 3.5 PVO2; 38.5 5.4, 30.3 4.1, 24.5 3.6 (PmCO2). Each variables linearly related (r = 0.99 each), with an intercept not different origin. Similar results obtained when subjects pushed work load 30 W higher ensure had been achieved. By extending our prior 1) maximum 2) direct sampling blood, conclude may be present humans. In addition, since PVO2, PfVO2, PmCO2 all relate VO2max, suggest whichever is most readily acceptable further evaluation hypothesis.