Increased Oxygen Desaturation During Acute Hypoxia In Individuals With High Heart Rate Variability

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 individuals with a higher 24 h heart rate variability (HRV) would exhibit greater decrease in oxygen saturation during acute exposure to normobaric hypoxia equivalent to an altitude of 4572 meters. METHODS: 22 young (20.8 ± 0.8 years), healthy subjects (16 female, 6 male) participated in the study. 24 h HRV was collected using the FirstBeat BodyGuard 3 and analyzed using the Kubios software one day prior to acute hypoxia exposure. Following the 24 h measurement, 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: Data from subjects was divided into two groups based on HRV calculated as RMSSD, the highest 50% (H-HRV) and the lowest 50% (L-HRV) and comparisons were made using a t-test. Subjects with H-HRV had a significantly greater (p < 0.05) decrease in %SpO2 from the last 5 min of rest at sea level to the first 5 min of hypoxia compared to subjects with L-HRV (-13.2 ± 0.9 v -11.2 ± 0.4). CONCLUSION: These results suggest that 24h HRV at sea level can be used to predict hypoxia induced hypoxemia and possibly risk for acute mountain sickness.