INVIVO THERMAL-CONDUCTIVITY OF THE HUMAN FOREARM TISSUES

The effective thermal conductivities of the skin + subcutaneous fat (k(eff skin+fat)) and muscle (k(eff muscle)) tissues of the human forearm at thermal steady state during immersion in water at temperatures (T(w)) ranging from 15 to 36-degrees-C were determined. Tissue temperature (T(t)) was continuously monitored by a calibrated multicouple probe during a 3-h immersion of the resting forearm. T(t) was measured every 5 mm from the longitudinal axis of the forearm (determined from computed-tomography scanning) to the skin surface. Skin temperature (T(sk)), heat loss (H(sk)), and blood flow (Q) of the forearm, as well as rectal temperature (T(re)) and arterial blood temperature at the brachial artery (T(bla)), were measured during the experiments. When the k(eff) values were calculated from the finite-element (FE) solution of the bioheat equation, k(eff skin+fat) ranged from 0.28 +/- 0.03 to 0.73 +/- 0.14 W. degrees-C-1. m-1 and K(eff muscle) varied between 0.56 +/- 0.05 and 1.91 +/- 0.19 W. degrees-C-1. m-1 from 15 to 36-degrees-C. The values of K(eff skin+fat) and k(eff muscle), calculated from the FE solution for T(w) less-than-or-equal-to 30-degrees-C, were not different from the average in vitro values obtained from the literature. The k(eff) values of the forearm tissues were linearly related (r = 0.80, P < 0.001) to Q for T(w) greater-than-or-equal-to 30-degrees-C. It was found that the muscle tissue could account for 92 +/- 1% of the total forearm insulation during immersion in water between 15 and 36-degrees-C.