Resting Heart Rate Variability At Sea Level Does Not Predict Arterial Desaturation Or Ventilatory Responses To Acute Hypoxia Exposure

Acute exposure to hypoxia results in a stress response categorized by sympathetic dominance, resulting in increased ventilation to prevent arterial desaturation. Heart rate variability (HRV) can be used as an estimation of overall stress and a provides understanding of the balance between sympathetic and parasympathetic autonomic regulation. PURPOSE: The purpose of this study was to determine whether resting heart rate variability at sea level is correlated with arterial desaturation and respiratory responses to acute normobaric hypoxia exposure equivalent to an altitude of 3500 meters. METHODS: Resting HRV, %SpO2, and respiratory rate was measured in 24 male and female subjects at sea level for 15 minutes. HRV was measured using Firstbeat Bodyguard2 and included RMSSD, High Frequency (HF), and Low Frequency (LF) components. Subjects then returned for a subsequent visit and resting HRV, SpO2 and respiratory rate were measured at rest in a normobaric hypoxic chamber (Colorado Altitude Training) set at either 3500 meters or sea level for control subjects. Correlation analysis using RStudio was performed. RESULTS: No significant correlation was observed between HRV in the time domain (RMSSD) and %SpO2 at rest (r=0.26, p=0.39), %SpO2 during exercise (r=-0.15, p=0.62), or respiratory rate during rest (r=0.42, p=0.15) when exposed to hypoxia. No significant correlation was observed between HRV in the frequency domain (LFHF Ratio) and %SpO2 at rest (r=-0.10, p=0.74), %SpO2 during exercise (r=-0.18, p=0.53), or respiratory rate during rest (r=-0.39, p=0.19) when exposed to hypoxia. CONCLUSION: Although exposure to acute hypoxia exerts a physiologic stress response, HRV as a measure of overall stress and the balance of sympathetic and parasympathetic balance does not seem to be predictive of the change in %SpO2 or respiratory rate. Supported by The Doug Morton/Marilyn Brown Endowment for Biomedical Research, The Foundation for Aging Studies and Exercise Science Research, and The Borgenicht Program.