Abstract
Restriction of blood flow in isolated vascular territories in living and unanesthetized animals has recently attracted attention. Some workers have fitted the blood vessels which are to be constricted into a type of rigid frame which reduces the diameter of the vessels.
Other investigators (Goldblatt, 1 Collins, 2 Rytand 3 ) achieved the desired degree of ischemia by tightening loops of wire or thread around the vessel. Brotchner∗ and Blum, Schauer and Calef 5 employ a device which permits gradual mechanical closure of the vessel by means of 2 solid bars which are brought together by a screw to be actuated by a stiff wire from outside the animal.
The work of Mann, Herrick, Essex, and Baldes 6 correlated blood flow in vessels with a decrease in internal diameter brought about by local constriction. It was shown that a significant diminution of flow was achieved only after reduction of the internal diameter of arteries to a small percentage of the original.
The internal diameter of a vessel cannot very well be controlled quantitatively in the living animal because of the variability of the connective tissue reaction around the clamp among other reasons. Once a constricting loop or a rigid frame is applied to a vessel and the wound closed, the blood flow cannot be changed without further surgical intervention. Even then the percentage reduction of blood flow remains unknown until after the death of the animal, when model experiments can be performed on the flow of the blood in the constricted vessel.
The method which is described here attempts to regulate flow by employing the principle of the blood pressure cuff. This method should allow reversible and well defined obstruction of the vessels in vivo, when the pressure in the cuff can be controlled by a piece of rubber tubing which is brought out through the body wall.
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