Impact of Hypoxia on Heart Rate Variability Based on Sample Entropy

In this study, changes in heart rate variability (HRV) induced by exposure to hypoxia were evaluate in healthy male. The sample entropy as a non-linear method of HRV analysis was used; it’s a powerful way to analyze biological system. Our aim was to investigate the influence of stepwise hypoxia on HRV using sample entropy, we tested nine healthy yellow males (age=35 ± 5) at 3600m, 4000m, 4400m, 4800m during rest, these were a part of the acclimation test. An increase in sample entropy at high altitude compared to 1000m was established in this research. The parameters showed similar tendencies during different altitude, but not so obvious. The changing of sample entropy in every day was analyzed. Our results indicate that hypoxia exerts an influence on HRV; it also suggested that acute exposure to normobaric hypoxia induces increases in sympathetic vasomotor activity and cardiac sympathetic dominance resulting in an increased heart rate.