Thermal measurements on divers in hyperbaric helium-oxygen environments

During a series of three saturation dives to simulated depths of 1000, 1200, and 1400 fsw at the Ocean Simulation Facility, measurements were made to establish the rate of heat loss of unclad divers in helium-oxygen gaseous environments. These measurements were part of a program to determine the dangers of cold stress and the temperature/time relationship tolerated by divers in cold diving bells or in hyperbaric chambers in which environmental conditions are uncontrolled. Three specific gaseous temperatures of 15, 20, and 25 degrees C were considered. In each experiment, as many as four subjects were monitored for body core and mean skin temperature over a 2-h testing period. One or two of the subjects were also monitored for mean body convective heat loss to determine physiological (shell) thermal insulation. Results of these experiments are expressed in depth-time-temperature three-dimensional graphs in whic, the temperature variable is one of the following: mean skin temperature change, mean body temperature change, or mean rectal (core) temperature change, each suitable for defining diver thermal limitations. It was also possible to rank body areas of the subjects in relation to heat loss and temperature decrease during exposure to the cold environment.