BLOOD FLOW AND VASOMOTOR REACTIONS IN THE HAND, FOREARM, FOOT, AND CALF IN RESPONSE TO PHYSICAL AND CHEMICAL STIMULI 1

Abstract

In order to obtain an accurate picture of the state of the peripheral circulation it is necessary to know the blood flow and the vasomotor reactions in as many parts of the body as possible. An investigation of the blood flow and the vaso-motor reactions of parts of the upper and the lower extremities is of particular significance, not only because of the wide variations in the proportion of muscle to skin in the different parts of the extremities, but also because of the presence in the skin of the hands and feet of numerous arteriovenous anastomoses which have not been demonstrated in other parts of the body (1). In order, therefore, to secure a more complete understanding of the peripheral circulation, the blood flow and the vasomotor reactions in the hand, forearm, foot, and calf at rest were studied by plethysmographic methods. In-addition, the changes in the blood flow following exercise and arterial occlusion and the effect of epinephrine and of pitressin on the blood flow were observed in these four parts of the body. METHOD The subjects selected for this study had normal cardio-vascular systems. The hand was studied in the plethys-mograph described by Freeman (2) and the foot in that described by Stead and Kunkel (3). The plethys-mograph of Lewis and Grant (4) was used for the forearm and a similar one of larger size was constructed for the calf. In each case the rubber cuffs closing the instruments were attached to the skin by rubber cement in such a manner as to cause no elevation of the venous pressure; they were prevented from bulging outward by suitable firm, fitted diaphragms. The instruments were connected by pressure tubing to Brodie bellows of 14 cc. capacity which recorded the changes in volume on a smoked drum. In order to maintain the water within the forearm and calf plethysmographs at a constant temperature, the instruments were surrounded by large 'The expense of this investigation has been met in part by a grant from the Proctor Fund of Harvard University for the Study of Chronic Disease. water baths; the hand or foot distal to them was exposed to the air. In experiments in which the blood flow and vasomotor reactions of the hand and foot were studied, the water surrounding these organs was constantly circulated by motor driven propellers, but that surrounding the arm and the calf was not mechanically stirred. The water baths were maintained at a constant temperature for at least 30 minutes before blood flow determinations were made. All observations were made with the subjects horizontal and the parts to be tested resting comfortably in the instruments at heart level. In order to measure simultaneously blood flows and vasomotor reactions in various organs, two or three plethysmographs were usually applied, though in no case was more than one instrument applied to the same extremity. These plethysmographs could be used for the determination of the blood flow to the enclosed portion of the extremity, since the initial rate of increase in volume produced by applying a collecting pressure just proximal to the instrument was a measure of the blood flow. The method used for calibrating the instruments and for calculating the blood flow was the same as that previously described for the determination of blood flow in the foot (3). As two rubber diaphragms had to be stabilized in the forearm and calf plethysmographs, these instruments were-found to be less accurate than the hand and foot plethysmographs. Unless otherwise stated, the blood flows are recorded as cubic centimeters of blood per minute per 100 cc. of tissue. In some instances the surface area of the part enclosed within the plethysmograph was measured by making a light plaster mold of the part. This mold was cut while still soft and made to lie flat by multiple incisions; its outline was traced on cardboard, which was then weighed. The surface area of the mold was calculated from the known weight of 100 sq. cm. of the cardboard.