Frequency Domain Measures of Heart Rate Variability At Sea Level Predict Oxygen Desaturation During Normobaric Hypoxia

Previous studies demonstrate that individuals with greater resting hypoxemia at moderate to high altitudes are at greater risk for developing acute mountain sickness (AMS). PURPOSE: The purpose of this study was to determine if short-term (5 min) measures of heart rate variability (HRV) could predict oxygen saturation during acute exposure to normobaric hypoxia equivalent to an altitude of 4572 meters. METHODS: 59 young (20.67±0.99 years), healthy subjects (31 female, 28 male) participated in the study. HRV was measured using the FirstBeat BodyGuard 3 and analyzed using the Kubios software 5 min prior to acute hypoxia exposure. Subjects rested in a reclined position for 10 min, breathing room air (~sea level), then normobaric, hypoxic air equivalent to 4572 m (11.8% oxygen) for 10 min, followed by a return to room air for an additional 10 min. Heart rate, HRV, minute ventilation (VE), and percent oxygen saturation (SpO2%) were measured continuously. RESULTS: Significant (p<0.5) correlations were observed between the change in oxygen saturation from normoxia to hypoxia (ΔSpO2%) and the low-frequency to high-frequency ratio (LF/HF), the natural logarithm of low frequency (LnLF), the natural logarithm of high frequency (LnHF), and the natural logarithm of the low-frequency to high-frequency ratio (LnLF/HF) measures of heart rate variability 5 minutes before hypoxia (r = 0.3712, 0.3558, -0.3325, and 0.5270, respectively). No other measures of heart rate variability were significantly correlated with the change in oxygen saturation from normoxia to hypoxia. CONCLUSION: These results suggest that HRV variability measures associated with sympathovagal balance are related to the degree of oxygen desaturation in humans exposed to acute normobaric hypoxia. Therefore, sympathovagal balance may predict susceptibility to acute mountain sickness. William & Mary Charles Center Summer Honors Fellowship This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.