Thermal dose requirement for tissue effect: experimental and clinical findings

Abstract

In this review we have summarized the basic principles that govern the relationships between thermal exposure (Temperature and time of exposure) and thermal damage, with an emphasis on normal tissue effects. We have also attempted to identify specific thermal dose information (for safety and injury) for a variety of tissues in a variety of species. We address the use, accuracy and difficulty of conversion of an individual time and temperature (thermal doses) to a standardized value (eg equivalent minutes at 43 degrees C) for comparison of thermal treatments. Although, the conversion algorithm appears to work well within a range of moderately elevated temperatures (2-15 deg C) above normal physiologic baseline (37-39 deg C) there is concern that conversion accuracy does not hold up for temperatures which are minimally or significantly above baseline. An extensive review of the literature suggests a comprehensive assessment of the "thermal does-to-tissue effect" has not previously been assembled for most individual tissues and never been viewed in a semi-comprehensive (tissues and species) manner. Finally, we have addressed the relationship of thermal does-to-effect vs. baseline temperature. This issues is important since much of the thermal dose-to-effect information has been accrued in animal models with baseline temperatures 1-2 deg higher than that of humans.