Journal of Applied Physiology, Vol 74, Issue 3 1274-1279, Copyright © 1993 by American Physiological Society
Hemodynamic and respiratory responses to carotid sinus pressure alteration in experimental hypertension
M. J. Brunner and M. D. Kligman
Department of Surgery, University of Maryland, Baltimore 21201.
The purpose of this study was to determine whether baroreflex control of
respiratory responses is diminished in hypertension. Ten dogs were made
chronically hypertensive with use of a bilateral renal wrap technique.
Eight sham-operated dogs served as normotensive controls. After the
development of experimental hypertension, carotid baroreflex control of
arterial pressure, heart rate, respiratory frequency, tidal volume, and
ventilation was acutely assessed. Under pentobarbital anesthesia and with
bilateral vagotomy, the carotid sinuses were isolated and perfused at
controlled pressures. Before the carotid sinus region was manipulated, the
mean arterial pressure was significantly higher (P < 0.005) in the
hypertensive group (146.4 +/- 2.3 mmHg) than in the normotensive group
(124.7 +/- 2.6 mmHg). The mean arterial pressures and heart rates measured
at every level of carotid sinus pressure were significantly higher in the
hypertensive group. Reflex gain of heart rate, but not mean arterial
pressure, was significantly reduced in the hypertensive group. Respiratory
frequency, tidal volume, and ventilatory responses to changes in carotid
sinus pressure were significant and resulted in an approximately 40% reflex
change in ventilation. These responses were not diminished in the
hypertensive group. We conclude that respiratory baroreflex responses are
preserved in experimental hypertension.
