AJP - Regulatory, Integrative and Comparative Physiology, Vol 273, Issue 4 1219-R1223, Copyright © 1997 by American Physiological Society

ARTICLES

Carotid baroreflex control of heart rate during acute exposure to simulated altitudes of 3,800 m and 4,300 m

S. Sagawa, R. Torii, K. Nagaya, F. Wada, Y. Endo and K. Shiraki
Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.

To examine the baroreflex response in humans during acute high-altitude exposure, the carotid baroreflex cardiac responsiveness was studied using a neck chamber in seven unacclimatized male subjects. Measurements were made in a high-altitude chamber on separate days at sea level and during 1-h exposure at two different altitudes of 3,800 m [partial pressure of oxygen in inspired air (PI(O2)) = 90 mmHg] and 4,300 m (PI(O2) = 82 mmHg). R-R intervals were plotted against neck chamber pressures, and the baroreceptor response was analyzed by applying a four-parameter sigmoidal logistic function. The baroreceptor response curve shifted downward in either altitude, reflecting a tachycardic response at high altitude, and the magnitude of the shift was greater at 4,300 m than at 3,800 m. There was no change in the sigmoidal parameters at 3,800 m compared with sea level except for a reduction (P < 0.05) of the minimum R-R interval. At 4,300 m the maximal R-R range, slope coefficient, minimum R-R interval, and maximal gain of the curve decreased significantly (P < 0.05) compared with sea level values, whereas the centering point of the curve remained unchanged. These results suggest that hypoxia (PI(O2) = 82 mmHg) reduces the sensitivity of carotid baroreflex cardiac response.

This article has been cited by other articles:

				B. E. Hunt, R. Tamisier, G. S. Gilmartin, M. Curley, A. Anand, and J. W. Weiss Baroreflex responsiveness during ventilatory acclimatization in humans Am J Physiol Heart Circ Physiol, October 1, 2008; 295(4): H1794 - H1801. [Abstract] [Full Text] [PDF]

				M. Gujic, D. Laude, A. Houssiere, S. Beloka, J.-F. Argacha, D. Adamopoulos, O. Xhaet, J.-L. Elghozi, and P. van de Borne Differential effects of metaboreceptor and chemoreceptor activation on sympathetic and cardiac baroreflex control following exercise in hypoxia in human J. Physiol., November 15, 2007; 585(1): 165 - 174. [Abstract] [Full Text] [PDF]

				L. Bennet, J. A. Westgate, Y.-C. Liu, G. Wassink, and A. J. Gunn Fetal acidosis and hypotension during repeated umbilical cord occlusions are associated with enhanced chemoreflex responses in near-term fetal sheep J Appl Physiol, October 1, 2005; 99(4): 1477 - 1482. [Abstract] [Full Text] [PDF]

				J. R. Halliwill and C. T. Minson Effect of hypoxia on arterial baroreflex control of heart rate and muscle sympathetic nerve activity in humans J Appl Physiol, September 1, 2002; 93(3): 857 - 864. [Abstract] [Full Text] [PDF]

				M. R. Bonsignore, G. Parati, G. Insalaco, O. Marrone, P. Castiglioni, S. Romano, M. Di Rienzo, G. Mancia, and G. Bonsignore Continuous Positive Airway Pressure Treatment Improves Baroreflex Control of Heart Rate during Sleep in Severe Obstructive Sleep Apnea Syndrome Am. J. Respir. Crit. Care Med., August 1, 2002; 166(3): 279 - 286. [Abstract] [Full Text] [PDF]