O2 CARRYING CAPACITY OF BLOOD AND VO2max DURING MAXIMAL EXERCISE 807

Effects of arterial desaturation on VO2max and anaerobic metabolism were evaluated during ergometer rowing in eleven oarsmen with hyperoxia(FIO2 30%). Low intensity rowing (47 (27-52)%, VO2max(5.0 (3.8-5.9) l min-1; median and range) did not affect arterial O2 tension (PaO2), arterial hemoglobin saturation (SaO2), or pH, while they were reduced at 75 (55-99)% VO2max and at a maximal exercise intensity. PaO2 was similar (74 (67-95) mmHg) at both high work intensities, but SaO2 was lower (89 (85-95) vs. 94(88-97)%) during maximal exercise concurrent with a low pH (7.13 (7.06-7.26)vs. 7.30 (7.18-7.35)). Hyperoxia elevated PaO2 at rest to 162(146-184) mmHg and it remained unchanged by maximal exercise. The arterial O2 content and VO2max increased similarly (6(-1-13) and 9(5-25)%) with no significant effect on performance (397 (245-446)vs. 385 (322-465) W; normoxia vs. hyperoxia). Blood lactate reached the same level in the last minute of exercise (11.3 (9.0-14.0) mmol-1) and also pH and base excess were similar to those established during air breathing. Thus, the O2 deficit was reduced (5.0 (0.4-33.6)vs. 3.0 (-4.1-30.8) l; normoxia vs. hyperoxia), but the O2 debt was not affected. We conclude that VO2max with 30% FIO2 increase in proportion to the O2 carrying capacity of blood without an effect on work capacity or anaerobic metabolism.