Heat Loss and Blood Flow of the Feet Under Hot and Cold Conditions

Abstract

Progressive changes in the feet related to thermoregulation during relatively long exposures (2-7 days) alternately to heat (33[degree] C) and cold (21[degree] C) were studied in 2 subjects, during winter and summer. Heat loss to the air was measured with a double-walled Cu calorimeter shaped like a boot. Blood flow was measured by the venous occlusion technic. Skin temps. were obtained with 36-gauge Cu-constantan thermocouples. During exposure to heat there was a gradual increase in toe temp. relative to the rest of the foot, but no other progressive change. In the cold no progressive changes were found. Evidence of acclimatization appeared only as differences between the various periods of exposure to the same temp. Exposure to cold reduced the ability of the foot to lose heat by vaporization during subsequent exposure to heat. This was associated with a decrease in the amt. of heat lost by each vol. of blood flowing through the foot. The foot, having about 5% of the total body area, lost approx. 6.5% of the total heat at 33[degree] C and only 3.5% at 21[degree] C. The heat loss per degree difference between skin and air at the higher temp. was approx. twice that at the lower temp.