EXERCISE INDUCED ARTERIAL HYPOXEMIA IN HIGHLY TRAINED WOMEN ATHLETES466

Abstract

Significant exercise induced arterial hypoxemia (EIH) occurs in some endurance trained young adult men with VO2max>65 ml/kg/min, presumably because demand for max O2 transport exceeds the lung's diffusion capacity. We asked if this imbalance of demand and capacity might also occur in female endurance trained athletes, who have lower reported values for VO2max. Ten healthy highly trained women (VO2max: 62.1; 53-70 ml/kg/min) (age: 28±4 yr) with normal resting lung function were tested during an incremental treadmill test to VO2max during the follicular phase of their menstrual cycle. Multiple blood samples were collected from the radial artery at rest, near the end of each exercise workload, and during recovery. Blood temperature was estimated from an esophageal probe. PaO2 decreased (p≤0.05) 19.5±7.4 mmHg from rest to VO2max (78.2; 67-91 mmHg) with significant hypoxemia(PaO2<75mmHg; SaO2=90.2+0.3%) occurring in 6 subjects. A-aDO2 increased from 5±3mmHg at rest to 38±5mmHg(29-47mmHg) at VO2max. The reduction in PaO2 at VO2max was significantly correlated to A-aDO2 and to PAO2. PaCO2 decreased 5.4±2.4 mmHg from rest to VO2max (32-39mmHg) and was not significantly correlated to PaO2. More female subjects are currently under study to better define the prevalence and severity of EIH. These findings in a limited sample size show that some adult female athletes experience significant EIH at VO2max values which are generally lower than in trained males. The data suggest that inequities between max demand for systemic O2 transport and pulmonary diffusion capacity are greater in trained females vs trained males.