Date of Award
Master of Science in Biomedical Engineering - (M.S.)
Biomedical Engineering Committee
David S. Kristol
Clarence W. Mayott
A whole body thermal model simulating heat distribution and temperature regulation in rats during hemorrhagic shock and during post-shock microwave core rewarming period was developed. An electrical circuit was used to simulate the thermal system and a software named PSpice? was used to analyze the circuit. The temperature regulation as the result of the simulation is demonstrated to match the measured temperature histories of rats in hemorrhagic shock and the microwave rewarming experiment.
The blood pressure drop and cardiac output decrease were considered in the simulation and the so called "set point temperature" was investigated in the model. Linear decrease and increase of the set point temperature were assumed during the simulation of the shock period and the post-shock rewarming period, respectively. The agreement between the simulation result and the experimental data validates the general structure of the model and assumptions.
Sensitivity Analysis shows the blood pressure drop, set point temperature and the ambient temperature to be the most sensitive parameters in the simulation.
A small group(n=3) of rats were rewarmed with microwave energy in a chilled environment meant to cool and vasoconstrict the peripheral circulation while warming the core organs with the penetrating microwave energy. The the survival rate of the rats was compared with the previous rewarming experiments. Even though the number of animals was statistically not adequate, the result of this work does suggest that further experiments along the same line, to increase the statistical data pool, are warranted. A larger number of experiments need to be performed to validate the suggestion.
A significant higher temperature gradient between the core and skin was observed during the chilled ambient rewarming which may be a contributory factor in the improvement of the survival statistics. The data acquisition is very time consuming and labor intensive. It requires at least 2 days to gather the data from one animal; most of the animals die during the shock interval and these animals are lost to the data poll.
Zhe, Liu, "The thermal model of the rat under hemorrhagic shock hypothermia with microwave intervention" (1993). Theses. 2218.