Journal of Applied Physiology, Vol 65, Issue 4 1556-1562, Copyright © 1988 by American Physiological Society
Arterial hemodynamics during head-up tilt in conscious dogs
T. G. Bedford and K. J. Dormer
Department of Physiology and Biophysics, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
The purpose of this study was to measure the major arterial hemodynamic
responses to head-up tilt in the conscious dog. After recovery from surgery
for instrumentation, and after habituation to tilt, the dogs were tilted
from horizontal to 75 degrees for 5 min. The arterial hemodynamic response
after the initial cardiovascular adjustments to the tilt consisted of no
change in heart rate and significantly increased arterial blood pressure,
with significantly reduced stroke volume and cardiac output. Both renal
blood flow and terminal aorta blood flow declined significantly, even more
than cardiac output. Muscular exertion was not part of the tilt response
because upright standing on the hindlimbs elicited a sustained increase in
heart rate and a significantly smaller increase in estimated total
peripheral resistance. When compared with the orthostatic response in
humans, the increase in arterial pressure was exaggerated in the dogs.
