TISSUE TEMPERATURE PROFILE IN THE HUMAN FOREARM DURING THERMAL-STRESS AT THERMAL-STABILITY

The purpose of the present study was to investigate the effect of a range of water temperatures (T(w) from 15 to 36-degrees-C) on the tissue temperature profile of the resting human forearm at thermal stability. Tissue temperature (T(ti)) was continuously monitored by a calibrated multicouple probe during 3 h of immersion of the forearm. The probe was implanted approximately 9 cm distal from the olecranon process along the ulnar ridge. T(ti) was measured every 5 mm, from the longitudinal axis of the forearm (determined from computed tomography scanning) to the skin surface. Along with T(ti), skin temperature (T(sk)), rectal temperature (T(re)), and blood flow were measured during the immersions. For all temperature conditions, the temperature profile inside the limb was linear as a function of the radial distance from the forearm axis (P < 0.001). Temperature gradient measured in the forearm ranged from 0.2 +/- 0.1-degrees-C cm (T(w) = 36-degrees-C) to 2.3 +/- 0.5-degrees-C cm (T(w) = 15-degrees-C). The maximal T(ti) was measured in all cases at the longitudinal axis of the forearm and was in all experimental conditions lower than T(re). On immersion at T(w) < 36-degrees-C, the whole forearm can be considered to be part of the shell of the body. With these experimental data, mathematical equations were developed to predict, with an accuracy of at least 0.6-degrees-C, the T(ti) at any depth inside the forearm at steady state during thermal stress. The data of the present study support the important role of convective heat exchange between blood and tissue on the T(ti) of the forearm.