Modelling Thermoregulation of the Human Body PDF Download

Author: Elias Ghadam Soltani
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Languages : en
Pages : 0

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Book Description
In this study, a computational model of the human thermoregulatory system is developed to predict the temperature distribution within tissues, on the skin and the arterial net- work. It is based on an anatomically accurate whole human body geometry comprising various tissue structures, organs and its vascular network. The governing equations that couple energy transfer between the blood and surrounding tissues were implemented in OpenCMISS, an open-source computational library that provides an environment to utilise the nite element method (among other specialised numerical methods) to solve partial di erential equations in complex bioengineering problems. Moreover, an open standard framework built using the XML mark-up language known as CellML was used to impose appropriate regulatory or control actions and update heat transfer mechanisms accordingly. The framework was also used to prescribe di erent types of boundary conditions as it is primarily used to solve di erential-algebraic equations. An extensive literature review is included in this thesis to provide an overview of the existing mathematical models used for studying the thermoregulation of the human body. The review covers the strengths, limitations and scope of ap- plications of these models. The computational model was formulated by coupling the bioheat equation describing the di usion of heat in three-dimensional tissue structures with the energy equation that is responsible for advection and di usion of heat along the one-dimensional blood ow in the arterial network. It can simulate the heat exchange between the body surface and surrounding environment due to conduction, convection, radiation and evapora- tive cooling or moisture transfer. Furthermore, it is capable of simulating blood ow under di erent conditions which is essential for evaluating heat exchange between the blood and surrounding tissues. This functionality of the model allows us to investigate how physiological conditions in the arterial network in uence the human thermal system and a ect its performance. Functionally the model is organised into two subsystems. The passive subsystem pri- marily deals with various modes of heat transport within tissues, between tissues and blood (arterial system and perfusion) and between the body and the surrounding en- vironment. The governing equations that mathematically describe the passive subsys- tem are based on the laws of conservation. The active subsystem, on the other hand, prescribes physiological phenomena in the body, namely, shivering, sweating, vasodila- tion and vasoconstriction and facilitates maintaining the body core temperature. These physiological activities are based on empirical formulations from previous studies. The blood ow and heat transfer included in the passive system was simulated using OpenCMISS and the active system was implemented by using CellML capabilities that enable to input controlling parameters and prescribe and update the boundary conditions to OpenCMISS (passive system). The model results were veri ed against closed-form so- lutions obtained for topologically simple domains and validated against published exper- imental data acquired under controlled conditions. In the latter case, a reasonably good agreement was seen between the model predictions and experimental observations. The structure of the model allows for investigation of the thermoregulatory responses of the human body under a multitude of ambient environmental conditions. Further- more, it would be possible to investigate temperature distribution in the vital organs and skin that can be used to diagnose heat-related conditions and make informed de- cisions to plan suitable treatments. The models capability of simulating the human thermoregulatory system with the abil- ity to obtain realistic skin and internal temperature distribution was demonstrated by considering a number of exposure scenarios. These included neutral condition, high and low temperatures. In all cases, local skin temperature distributions were eval- uated. The e ect of body shape and distribution of the thermophysical properties were also investigated. An important aspect of the current model development is that an open-source code and libraries were used in this thesis research. As such, any contribution made through this study allows other researchers to modify, improve and extend the model for other applications.