Resting Heart Rate Variability at Sea Level Predicts Arterial Desaturation during Acute Exercise in Hypoxia

Predicting responses to acute hypoxia based on physiologic measures at sea level may be valuable in anticipating adverse responses to acute hypoxia. The purpose of this study was to examine the relationships between heart rate variability (HRV) and arterial oxygen desaturation in response to acute hypoxia exposure at rest and during exercise. METHODS: 13 subjects (6 male, 7 female) aged 20.6±0.3 years rested in a supine position for 10 min after steady state respiration was achieved. Average resting HRV and arterial oxygen saturation (%SpO2) were calculated from the last 5 min. A VO2peak test to determine aerobic fitness (44.1±3.0 ml/kg/min) was performed on a stationary cycle at sea level. Subjects also performed a submaximal bike test for 10-15 min at 65% of HRmax achieved during the VO2peak test in normobaric hypoxia equivalent to an altitude of 3500 meters. RESULTS: HRV (RMSSD 54.5±5.7) was significantly correlated (r=0.227, P\u3e0.05) to the percent change (9.7±0.7) in %SpO2 from rest (97.4±0.2) to exercise (88.0±0.8) in normobaric hypoxia. CONCLUSIONS: HRV at rest appears to be predictive of the degree of arterial desaturation during exercise in hypoxia equivalent to an altitude of 3500 meters. Current wearable technology that can measure HRV could be used to predict potential adverse responses to exercise in hypoxic conditions such as altitude. Keywords: Heart Rate Variability (HRV), Acute Hypoxia, Arterial Desaturation, Acute Mountain Sickness (AMS