Carotid arterial hemodynamics in response to l.b.n.p in normal
subjects : methodological aspects.
B., Pannier, Slama M. A., London G. M., Safar M. E., Cuche J. L.
Department of Internal Medicine and INSERM (U337), Broussais
Hospital, Paris, and Manhes Hospital*, 91700 Fleury Merogis,
FRANCE.
APStracts 2:0271A, 1995.
Pulsatile changes in blood pressure and arterial diameter were studied
noninvasively using applanation tonometry and echotracking techniques
at the sites of the common carotid artery (CCA)and the carotid artery
bulb (CAB) in 12 healthy volunteers. Determinations were performed
before and during application of -10 and -40 mmHg lower body negative
pressure (LBNP) in order to investigate non invasively the tensile
forces acting on the carotid arterial bulb. Together with
significantly decreased mean arterial pressure and increased heart
rate, forearm vascular resistance and plasma norepinephrine, the -40
? mmHg LBNP stimulus produced the following significant changes in
carotid (CCA and CAB) arterial hemodynamics : (i) for the same
decrease in mean arterial pressure, a greater decrease in carotid
than in brachial pulse pressure was observed (P<0.01), due to a
significant change in pressure wave transmission and in the timing of
the carotid backward pressure wave ; (ii) a highly significant
decrease in pulsatile changes in diameter and tangential tension
occurred, with a greater decrease in systolic than in diastolic
tangential tension. Subsequently, cyclic tangential tension decreased
more substantially than mean tangential tension. The cyclic changes
in tension were quite significant after -40mmHg LBNP but were already
observed for mild -10 mmHg LBNP in which mean systemic blood pressure
and heart rate were not modified. During -10 and -40 mmHg LBNP, CCA
and CAB compliance and distensibility were unchanged. This study
provides evidence that the autonomic nervous system activation
produced by the LBNP procedure is associated with significant changes
in pressure wave amplification and in cyclic tensile forces acting on
the carotid bulb. These changes, which may occur even for mild LBNP,
should be taken into account when interpreting results of the LBNP
procedure in humans.
Received 1 June 1994; accepted in final form 22 June 1995.
APS Manuscript Number A537-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.