Modelling and investigation of temperature field in the boundary layer of biological bodies

A problem on finding temperature field in the boundary layer of biological body when blood perfusion coefficient depends on coordinate is solved. Temperature distribution is caused by the temperature differences between the inside and outside of a body and by the outside heat sources and metabolic heat generation. Heat transfer problem is formulated by using generalized Heaviside functions. Applying the variation of constants method this problem is reduced to the Fredholm integral equation of the second kind. Numerical method of Simpson quadratures was used to solve integral equation. Analysis of temperature distribution in the boundary layer for some cases of boundary conditions is performed. Dependence on temperature inside body from metabolic heat generation and outside heat source is analyzed.

TEMPERATURE DISTRIBUTION AND THERMAL DAMAGE OF PERIPHERAL TISSUE IN HUMAN LIMBS DURING HEAT STRESS: A MATHEMATICAL MODEL

The physiological processes taking place in human body are disturbed by the abnormal changes in climate. The changes in environmental temperature are not effective only to compete with thermal stability of the system but also in the development of thermal injuries at the skin surfaces. Therefore, it is of great importance to estimate the temperature distribution and thermal damage in human peripherals at extreme temperatures. In this paper, the epidermis, dermis and subcutaneous tissue were modeled as uniform elements with distinct thermal properties. The bioheat equation with appropriate boundary conditions has been used to estimate the temperature profiles at the nodal points of the skin and subcutaneous tissue with variable ambient heat and metabolic activities. The model has been solved by variational finite element method and the results of the changes in temperature distribution of the body and the damage to the exposed living tissues has been interpreted graphically in relation with various atmospheric temperatures and rate of metabolic heat generation. By involving the metabolic heat generation term in bioheat equation and using the finite element approach the results obtained in this paper are more reasonable and appropriate than the results developed by Moritz and Henriques, Diller and Hayes, and Jiang et al.

Variational finite element approach to study the thermal stress in multi-layered human head

The human head is one of the most sensitive parts of human body due to the fact that it contains brain. Any abnormality in the functioning of brain may disturb the entire system. One of the disturbing factors of brain is thermal stress. Thus, it is imperative to study the effects of thermal stress on human head at various environmental conditions. For the thermoregulation process, the human head is considered to be a structure of four layers viz.; brain, cerebrospinal fluid (CSF), skull and scalp. A mathematical model has been formulated to estimate the variation of temperature at these layers. The model is based on radial form of bio-heat equation with the appropriate boundary conditions and has been solved by variational finite element method. The rate of metabolic heat generation and thermal conductivity in this study have been assumed to be heterogeneous. The results were compared with the experimental studies for their coincidence and it has been observed theoretically and experimentally that the human head has greater resistance to compete with the thermal stress up to large extent.

Effect of Geometry and Blood Flow in Cooling of Upper Leg

Systemic hypothermia has been shown to reduce neurological damage in post-cardiac arrest patients. Reducing a patient’s core temperature to 33°C over a period of 24 to 48 hours has been shown to reduce long-term neurological damage by 16% and mortality by 14% [1]. Hypothermia is frequently induced by surface cooling, either with medical devices that circulate coolant in a pad, or ice packs. However, there is a lack of knowledge about the thermal response of tissue to localized cooling. Current thermal models are designed for determining human comfort and have not been evaluated for the targeted low temperatures required for inducing hypothermia. Metabolic heat generation and tissue perfusion rate can significantly change under low temperature, which in turn affects the overall heat flux and cooling rates.

A Study on the Effect of Metabolic Heat Generation on Biological Tissue Freezing

The effect of metabolic heat generation on the freezing of biological tissue has been studied. Quasi-steady approximation is used to solve the Pennes bioheat equation in tissues. Temperature profile and motion of freezing interfaces are obtained for different values of metabolic heat generation. It is observed that metabolism has a significant effect on freezing of biological tissues during cryosurgery.

SEMINUMERICAL MODEL TO STUDY TEMPERATURE DISTRIBUTION IN PERIPHERAL LAYERS OF ELLIPTICAL AND TAPERED SHAPED HUMAN LIMBS

In this article, a seminumerical approach has been developed to study temperature distribution in peripheral layers of tapered shaped human limbs, which are elliptical in shape. The model is three-dimensional which incorporates the important biophysical parameters such as blood mass flow rate, thermal conductivity and rate of metabolic heat generation. Appropriate boundary conditions have been framed using biophysical conditions. The finite element method has been employed along radial and angular directions and Fourier series method along axial direction to obtain temperature profiles in the region. The results have been used to study relationships among various physical and physiological parameters. MATLAB 7.0 has been used to simulate the model and obtain numerical results.