Heart Rate Nonlinear Dynamics During Sudden Hypoxia at 8230 m Simulated Altitude

Abstract

Autonomic responses are crucial for adaptation to hypoxia. Acute hypoxia triggers several autonomic mechanisms, mainly in the respiratory system (eg, the hyperventilation started by the peripheral chemoreceptor reflex) and in the cardiovascular system (eg, sympathetic activation with heart rate and cardiac output increase to improve pulmonary and tissue perfusion).¹ x 1 Weir, E.K., Lopez-Barneo, J., Buckler, K.J., and Archer, S.L. Acute oxygen-sensing mechanisms. N Engl J Med. 2005; 353: 2042–2055 Crossref | PubMed | Scopus (307) | Google Scholar See all References Previous studies have evaluated heart autonomic response using heart rate variability (HRV) analysis in subjects exposed to acute hypobaric hypoxia in real² x 2 Kanai, M., Nishihara, F., Shiga, T., Shimada, H., and Saito, S. Alterations in autonomic nervous control of heart rate among tourists at 2700 and 3700 m above sea level. Wilderness Environ Med. 2001; 12: 8–12 Abstract | Full Text | Full Text PDF | PubMed | Scopus (54) | Google Scholar See all References as well as simulated settings,³ x 3 Zuzewicz, K., Biernat, B., Kempa, G., and Kwarecki, K. Heart rate variability in exposure to high altitude hypoxia of short duration. Int J Occup Saf Ergon. 1999; 5: 337–346 PubMed | Google Scholar See all References ^{, 4} x 4 Yamamoto, Y., Hoshikawa, Y., and Miyashita, M. Effects of acute exposure to simulated altitude on heart rate variability during exercise. J Appl Physiol. 1996; 81: 1223–1229 PubMed | Google Scholar See all References usually introducing the changes in inspired O₂ concentration gradually and at altitudes below 6400 m (21 000 ft).