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Finite Element Model of Human Thermoregulation in Cold Conditions

Author
Berman, Aaron; Khalatyan, Yekaterina; Umeki, Chris; Zhou, Max
Abstract
The human body can only function properly within a narrow range of temperatures. Therefore, the
regulation of body temperature is a critical part of survival. Thermal homeostasis is maintained
through complex feedback loops, with the body reacting to local temperature changes. The
critical components of this feedback loop are linked to the skin temperature and the hypothalamus
temperature. the skin is responsible for heat sensing, while the hypothalamus is the body’s
temperature control center.
In this study the effect of thermoregulation on the temperature of multiple domains throughout
the body was considered, and an attempt to create a 3-dimensional model that accurately displays
its effect on body temperature was attempted. To investigate the effect that thermoregulation has
on maintaining temperature and to investigate the accurate temperature profile of the human body,
COMSOL, a finite element software capable of running physics simulations, was utilized. There
had been previous research on the topic that used only a few hundred nodes or used lumped
parameters to simulate thermal regulation. Our model’s geometry was 3-dimensional and inspired
by the dimensions used in a previous model by Dr. Dusan Fiala [1].
To implement thermoregulatory effects, empirical formulas were found in previous literature
for shivering, vasodilation and vasoconstriction among others. All empirical formulas were
temperature sensitive and were functions of the skin temperature and/or the hypothalamus
temperature. These effectors change the local heat generation terms and the local blood perfusion
terms, both crucial components of the heat equation in biological systems. An initial simulation
of the body temperature was run at cool environment with some air flow. The results showed a
sharp decline in average skin and fat temperatures initially due to their proximity to the surface,
while the average brain temperatures declined gradually and then flattened off within the first
two hours. Simulations excluding different components of thermoregulation were also ran to
portray the importance of thermoregulation in the body. The simulations without thermoregulatory
components resulted in much lower brain temperatures, as expected . Furthermore, the magnitude
of different effectors were measured, allowing for analysis on the importance of different ways
body’s thermoregulate. To validate the model, experimental data was compared to our simulated
result. Experimental data regarding skin temperature over time, and shivering magnitude over
time matched the overall trend of our data. Similarly, research on what external temperatures
induce shivering were in line with the simulated results.
This model provides insight into the distribution of temperature across the human body and will
provide the basis of a comprehensive human model applicable to a range of topics, such as
clothing insulation and frostbite analysis. By incorporating empirical equations that are functions
of temperature and having a 3D model that is heavily discretized, the model can accurately
portray the body’s temperature profile in cold climates.
Date Issued
2019-05Subject
thermoregulation; weather; body heat; hypothermia; homeostasis
Type
presentation