Thermoregulatory controller function : modeling and manipulation

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2021-05

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This dissertation presents research conducted to advance the field of human thermoregulation. Specifically, a novel method for stimulating the thermoregulatory system is introduced. Additionally, the formulation and analysis of a model of the interdependency of core temperature and the primary thermoregulatory effector mechanism, glabrous skin blood flow (GSBF), is described. Prior to conducting the research, the need for a conformable, two-dimensional skin temperature sensor was realized. The design, fabrication, and testing of a novel sensor is also presented. Thermoregulation research and various medical procedures are accomplished by manipulating skin temperature in a nonuniform pattern. Skin temperature monitoring is essential to assess conformance to protocol specifications and to prevent thermal injury. Existing solutions for skin temperature monitoring, such as single point thermocouples are not capable of integrating the temperature over an area. Therefore, I developed two-dimensional resistance temperature detector (2D RTD) by knitting copper magnet wire into custom shapes. The 2D RTD proved to be a superior device for measuring average skin temperature over a defined area exposed to a nonuniform temperature boundary. The 2D RTD allowed for an accurate assessment of the efficacy of Selective Thermal Stimulation (STS), a method of stimulating the thermoregulatory system. STS is accomplished by mild surface heating along the spinal cord, which houses a concentration of thermoreceptors. STS caused a statistically significant increase in GSBF. This study supports the theory that STS improves the heat exchanger efficiency of palmar and plantar surfaces by increasing the blood flow. The final section of this dissertation focuses on a model that describes the interplay between core temperature and GSBF in controlling thermoregulatory function. Transient GSBF in the model is influenced by core temperature, nonglabrous skin temperature, and the application of STS. Core temperature in the model is influenced by integrated heat transfer across the nonglabrous body surface and GSBF. Thus, there is a strong cross-coupling between GSBF and core temperature. The model coefficients were unique to each of the twelve data sets but produced excellent agreement between the model and experimental data. The strong match between the model and data confirms the mathematical structure of the control algorithm.

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