The relationship between exercise intensity, pulmonary diffusion and hemoglobin saturation in competitive endurance athletes

The goal of the present investigation was to evaluate the role of the pulmonary diffusion capacity (as measured by DLco) in relation to exercise-induced hypoxemia in elite athletes working at near maximal exercise intensities. Twenty-four elite cyclists were submitted to a direct measurement of VO$ sb2$ max on cycle ergometer which permitted classification into one of two groups. "Desaturaters" (N = 13) if oxyhemoglobin saturation (SaO$ sb2$%), as determined by finger oxymetry, fell below 91% or "non-desaturaters" if SaO$ sb2$% remained above 91%. Subsequent determinations of the transfer capacity for CO (DLco) were made using a 3 second breath-hold technique (Gould 2400/2450), at rest as well as at 60% and 90% of previously determined VO$ sb2$ max ($>$4.0 1/min). The results show an increase in DLco from rest to the first exercise intensity (desat: 41.7 $ pm$ 5.7 to 55.1 $ pm$ 4.7; non-desat: 41.1 $ pm$ 5.8 to 57.2 $ pm$ 6.9 mlsCO/mmHg/min) without much further increase to the maximal workload (desat: 61.0 $ pm$ 6.0; non-desat: 61.4 $ pm$ 9.5 mls CO/mmHg/min). No significant differences in DLco were found between the two groups at rest or either of the two exercise intensities. Significant differences between the desat and non-desat groups were found for FVC, post-exercise FEF$ sb{25-75 %}$, and VE/VO$ sb2$.The present results are in agreement with previous reports showing arterial desaturation in 50% of highly-trained subjects when VO$ sb2$ max $>$4.0 1/min. The present investigation cannot clearly establish the role of DLco in this response. (Abstract shortened by UMI.