AJP - Regulatory, Integrative and Comparative Physiology, Vol 260, Issue 3 576-R580, Copyright © 1991 by American Physiological Society

ARTICLES

Impairment of carotid-cardiac vagal baroreflex in wheelchair-dependent quadriplegics

V. A. Convertino, W. C. Adams, J. D. Shea, C. A. Thompson and G. W. Hoffler
Biomedical Operations and Research Office, Kennedy Space Center 32899.

The incidence of orthostatic hypotension can increase after prolonged exposure to chair rest and bedrest and is associated with post-bed rest impairment of the carotid-cardiac baroreflex response. We therefore hypothesized that the hypotension observed in humans confined to wheelchairs may be manifested by a reduced baroreflex sensitivity. We compared baroreflex responses of 16 wheelchair-dependent (WCD) quadriplegics with those of 15 able-bodied subjects (ABS) matched for age, height, and weight. Beat-to-beat R-R intervals were measured during application of graded pressures from 40 to -65 mmHg using a neck chamber for noninvasive stimulation of the carotid baroreceptors. Changes of R-R intervals were plotted against carotid distending pressures. The maximum slope of the stimulus-response relationship was greater (P less than 0.0001) in ABS (6.1 +/- 0.6 ms/mmHg) than in WCD (2.6 +/- 0.4 ms/mmHg). The range of the R-R interval response, i.e., the capacity to buffer blood pressure changes, was only 138 +/- 19 ms in WCD compared with 253 +/- 19 ms in ABS (P less than 0.001). Mean sitting systolic-to-diastolic blood pressures in WCD (92/60 mmHg) were less (P less than 0.0001) than in ABS (120/77 mmHg), although there were no significant differences between groups in supine resting blood pressures. Chronic loss of stimulation to carotid baroreceptors by routine standing posture is associated with attenuated sensitivity and reduced buffer capacity of the arterial baroreflex and hypotension during sitting in WCD patients.

This article has been cited by other articles:

				K. D. Monahan Effect of aging on baroreflex function in humans Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2007; 293(1): R3 - R12. [Abstract] [Full Text] [PDF]

				S. D. Beske, G. E. Alvarez, T. P. Ballard, and K. P. Davy Gender difference in cardiovagal baroreflex gain in humans J Appl Physiol, November 1, 2001; 91(5): 2088 - 2092. [Abstract] [Full Text] [PDF]

				J. M. Legramante, G. Raimondi, M. Massaro, and F. Iellamo Positive and Negative Feedback Mechanisms in the Neural Regulation of Cardiovascular Function in Healthy and Spinal Cord-Injured Humans Circulation, March 6, 2001; 103(9): 1250 - 1255. [Abstract] [Full Text] [PDF]

				D. E. Watenpaugh; and V. A. Convertino Gender and Heart Rate Regulation Am J Physiol Regulatory Integrative Comp Physiol, October 1, 1999; 277(4): R1246 - R1246. [Full Text] [PDF]

				V. A. Convertino Gender differences in autonomic functions associated with blood pressure regulation Am J Physiol Regulatory Integrative Comp Physiol, December 1, 1998; 275(6): R1909 - R1920. [Abstract] [Full Text] [PDF]