The effect of exercise modality on exercise-induced hypoxemia

To investigate the effect of exercise mode on arterial oxyhemoglobin satura tion (Sa(O2)) 13 healthy, actively training men who displayed exercise-indu ced hypoxemia (EIH) performed two incremental maximal exercise tests: uphil l treadmill running and cycle ergometry. At maximum, treadmill running resu lted in a lower Sa(O2) (88.6 +/- 2.0% versus 92.6 +/- 2.0%), a lower ventil atory equivalent for carbon dioxide ((V) over dot (E)/(V) over dot (CO2): 2 8.8 +/- 0.6 versus 31.2 +/- 0.9); and a higher maximal oxygen consumption ( (V) over dot (O2 MAX); 4.83 +/- 0.11 l.min(-1) versus 4.61 +/- 0.14 l.min(- 1)) when compared to cycle ergometry. When data were combined from maximal running and cycling, Sa(O2) was correlated to (V) over dot (E)/(V) over dot (CO2) (r = 0.54). However, there was no relationship between the differenc es in Sa(O2) and ventilation between exercise modes. This suggests that ven tilation is important in the maintenance of Sa(O2) but that the difference observed in Sa(O2) between treadmill running and cycle ergometry cannot be explained by differences in ventilation and must be due to differences in d iffusion limitation or ventilation-perfusion inequality. (C) 1999 Elsevier Science B.V. All rights reserved.