Precooling of Blood in the Arteries, Effective Heat Capacity and Evaporative Cooling as Factors Modifying Cooling of the Extremities

Abstract

The course of skin temp. changes of hands and feet inserted into a refrigerator box were followed with Cu-constantan thermocouples, during the cooling period and fol- lowing removal. In occasional expts. the extremity was also enclosed in a calorimeter within the refrigerator box. The extremities were covered with gloves or boots and socks (wet or dry) having different insulation and head capacity values. Rapid increases in surface temp. occurred in some expts. in response to painful cold. In the opinion of the authors the temps. reached are not high enough to preclude arterial precooling. During both cooling and rewarming, precooling of arterial blood may produce paradoxical changes in surface temp. Heat capacity of the covering is shown to be an important factor in the rate of cooling of an extremity; tolerance time was an unreliable guide to insulative value. Evaporative heat loss may constitute a large proportion of the total less in temps. near the freezing level. Suggestions for protection from such loss are made.