ARTERIAL OXYGEN SATURATION DURING MAXIMAL EXERCISE DEPENDS ON CAPACITY TO INCREASE VENTILATION

Abstract

Listen

Translate article

1660 The capacity of the healthy pulmonary system has traditionally been considered too large to limit exercise. The observation of exercise-induced hypoxemia (EIH) in some highly trained athletes has led to reevaluation of pulmonary performance during exercise. In order to examine the relationship between ventilatory response to exercise and the maintenance of arterial oxygen saturation (SaO2), nine highly trained collegiate male runners (VO2max, 72.1, s.d. 4.4 ml*kg−1*min−1) performed a progressive treadmill test to maximal exercise. Flow-volume loops, metabolic data, and end-tidal gas samples were collected during the penultimate and final stages of exercise. All subjects displayed EIH (SaO2, 88.8, s.d. 1.8%). The extent of expiratory flow limitation varied (range 0.0 - 42.6% flow limited). SaO2 at maximal exercise was inversely related to the change in FETCO2 with the final work increase (r = −0.72) and the change in VE/VCO2 (r = 0.81). The breathing frequency response to the final work increase was inversely related to the change observed in FETCO2 (r = −0.79), and directly related to the changes in VE/VCO2 (r = 0.78) and SaO2 at end exercise (r = 0.66). Also, there was a relationship between the change in degree of expiratory flow limitation and the decline in SaO2 (r = −0.84). Within our sample, relationships are evident among the extent of expiratory flow limitation, the ability to increase breathing frequency, and end exercise arterial desaturation. This suggests that some athletes ventilate at their maximal ventilatory capacity and further increases in ventilation are not possible.