Thermal conductivity measurements and predictions for biological fluids and tissues

Summary The thermal conductivities of normal samples of biological fluids and tissues determined experimentally have been presented. A special, unidirectional heat flow apparatus which yields absolute conductivity results was described. Conductivity measurements were reported for the following specimens: human blood and plasma; bovine muscle, vitreous humor, aqueous humor, lung, liver, kidney, bone marrow, fat, and brain; chicken skin and egg yolk. The thermal conductivities of several tissues measured after these specimens were slowly frozen to a little below 32°F and then slowly thawed were presented; the conductivities increased 10 to 20% above values obtained for corresponding unstressed specimens. The corresponding conductivity changes for samples that were cryogenically frozen and more quickly warmed were smaller. The thermal conductivities of all the biological fluids and tissues studied also were predicted using mathematical heat conduction models based on the premise that all biological specimens are composed of three primary materials, namely, water, fat, and protein. With the exception of one stratified biological species and one contaminated specimen, the predicted conductivities for one of the mathematical models differed from measured values by ±3% or less.