Vascular Resistance of Intestine, Muscle and Skin during Blood Pressure Oscillation

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Abstract
After the blood supply to the head was surgically limited to 1 common carotid artery in rabbits, the artery was compressed by exertion of stepwise elevated side pressure on a segment of the artery. Systemic arterial pressure rose and began to oscillate when the side pressure was increased to 50-60 mm Hg. The oscillations were regular and occurred at a rate of 3-4/min with a wave height of 15-45 mm Hg. Concomitant with systemic pressure oscillations and in near synchrony were undulations in the perfusion pressures recorded during constant flow from the vascularly isolated abdominal skin, skeletal muscle and small intestine. With the graded elevation of side pressure on the common carotid artery, mean systemic pressure and perfusion pressure showed a nearly exponential relation. The ratio between the 2 variables was slightly less than 1 below the systemic pressure of 120 mm Hg and rapidly increased above this level. At ratios greater than 1, the peripheral resistance undulations in the isolated areas gave a larger minimum and maximum, a sharper contour and, particularly in the skin, a phase lag in the period of the wave form when compared to the systemic pressure oscillations. The differences in response characteristics of peripheral resistance vessels and those of cardiac output and different consecutive parts of the systemic arteries during periods of intense sympathetic activation are highlighted.

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