Nonlinear bioheat model for dynamics of hypothermia and frostbite. Ⅰ. Modeling aspects.

We propose a new bioheat model for thermoregulation in the human body in response to cold environments, with emphasis on hypothermia and frostbite in exposed extremities. The model couples the bioheat transfer equation in the extremity with a differential equation that describes the core temperature. We used simulations to illustrate the connection between microscale vascular exchange and the effective perfusion term in the bioheat transfer equation. The nonlinear coupling proposed here incorporates physiologically motivated feedback laws for local and reflex vasoconstriction, as well as heat exchange with the environment. We illustrated the model numerically with realistic scenarios of thermoregulation regarding the thermal response of the body, which involves preservation of core temperature despite an increased frostbite risk. The model provides a robust framework for predictive studies of cold-induced injuries.