The circulation in cold acclimatization.

The hand and forearm blood flow of the Eskimo has been found to be greater than that of a control group of white persons in a temperate climate both at rest at an ambient temperature of 20 C. and during acute cold exposure. Under cold stress, rectal temperature was better maintained in the Eskimos, though certain deep muscle temperatures fell more than they did in the white men because of the greater blood flow through exposed parts. The Eskimos showed an elevation of basal metabolic rate and of plasma and total red cell volume. There are similarities between the circulatory changes found in the Eskimo and those found in hyperthyroidism. IT IS well known that the effects of acute cold exposure are peripheral vasocon-,striction, diuresis and hemoconcentration. Two questions arise in connection with long-term cold exposure or cold acclimatization. Is the vascular response to acute cold exposure different in the acclimatized person? Does the acclimatized person, as compared with the unacclimatized, show changes in peripheral circulation when both are at a reasonably comfortable ambient temperature? Studies of the vascular dynamics of acclimatized persons have so far been few. The most important have been those of Balke, Cremer, Kramer and Reichel1 who studied skin temperature changes in men exposed to moderate cold for 28 days, and those of Carlson and his col-leagues2' 3 who studied skin, muscle and rectal temperatures in subjects who had been exposed for various times. In this report there are presented the results of studies of peripheral blood flow, skin, subcutaneous, muscle and rectal temperatures in acclimatized and non-acclimatized subjects, both during acute cold exposure and at a comfortable ambient temperature. Data have also been obtained on the basal metabolic rate and on the blood volume while at rest.