The effect of exercise modality on exercise-induced hypoxemia

To investigate the effect of exercise mode on arterial oxyhemoglobin saturation (SaO2), 13 healthy, actively training men who displayed exercise-induced hypoxemia (EIH) performed two incremental maximal exercise tests: uphill treadmill running and cycle ergometry. At maximum, treadmill running resulted in a lower SaO2 (88.6+/-2% versus 92.6+/-2.0%) a lower ventilatory equivalent for carbon dioxide (VE/VCO2; 28.8+/-0.6 versus 31.2+/-0.9), and a higher maximal oxygen consumption (VO2, MAX; 4.83+/-0.11 l x min(-1) versus 4.61+/-0.14 l x min(-1) when compared to cycle ergometry. When data were combined from maximal running and cycling. SaO2 was correlated to VE/VCO2 (r = 0.54). However, there was no relationship between the differences in SaO2 and ventilation between exercise modes. This suggests that ventilation is important in the maintenance of SaO2, but that the difference observed in SaO2 between treadmill running and cycle ergometry cannot be explained by differences in ventilation and must be due to differences in diffusion limitation or ventilation-perfusion inequality.