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Carotid baroreceptor reflexes in humans during orthostatic stress

Cooper, V.L. and Hainsworth, R. (2001) Carotid baroreceptor reflexes in humans during orthostatic stress. Experimental Physiology, 86 (5). pp. 677-681. ISSN 0958-0670

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Orthostatic stress, including standing, head-up tilting and lower body suction, results in increases in peripheral vascular resistance but little or no change in mean arterial pressure. This study was undertaken to determine whether the sensitivity of the carotid baroreceptor reflex was enhanced during conditions of decreased venous return. We studied eight healthy subjects and determined responses of pulse interval (ECG) and forearm vascular resistance (mean finger blood pressure divided by Doppler estimate of brachial artery blood velocity) to graded increases and decreases in carotid transmural pressure, effected by a neck suction/pressure device.

Responses were determined with and without the application of lower body negative pressure (LBNP) at -40 mmHg. Stimulus-response curves were determined as the responses to graded neck pressure changes and the differential of this provided estimates of reflex sensitivity. Changes in carotid transmural pressure caused graded changes in R-R interval and vascular resistance. The cardiac responses were unaffected by LBNP. Vascular resistance responses, however, were significantly enhanced during LBNP and the peak gain of the reflex was increased from 1.2 ± 0.3 (mean ± S.E.M.) to 2.2 ± 0.3 units (P < 0.05). The increased baroreflex gain may contribute to maintenance of blood pressure during orthostatic stress and limit the pressure decreases during prolonged periods of such stress. Experimental Physiology (2001) 86.5, 677-681.

Item Type: Article
Copyright, Publisher and Additional Information: © Cambridge University Press
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Medicine and Health (Leeds) > School of Medicine (Leeds) > Leeds Institute of Genetics, Health and Therapeutics (LIGHT) > Academic Unit of Cardiovascular Medicine (Leeds)
Depositing User: Repository Assistant
Date Deposited: 26 May 2006
Last Modified: 05 Jun 2014 20:56
Published Version: http://dx.doi.org/10.1113/eph8602213
Status: Published
Publisher: Cambridge University Press
Refereed: Yes
Identification Number: 10.1113/eph8602213
URI: http://eprints.whiterose.ac.uk/id/eprint/1238

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