Transport lattice models of heat transport in skin with spatially heterogeneous, temperature-dependent perfusion

BACKGROUND: Investigation of bioheat transfer problems requires the evaluation of temporal and spatial distributions of temperature. This class of problems has been traditionally addressed using the Pennes bioheat equation. Transport of heat by conduction, and by temperature-dependent, spatially heterogeneous blood perfusion is modeled here using a transport lattice approach. METHODS: We represent heat transport processes by using a lattice that represents the Pennes bioheat equation in perfused tissues, and diffusion in nonperfused regions. The three layer skin model has a nonperfused viable epidermis, and deeper regions of dermis and subcutaneous tissue with perfusion that is constant or temperature-dependent. Two cases are considered: (1) surface contact heating and (2) spatially distributed heating. The model is relevant to the prediction of the transient and steady state temperature rise for different methods of power deposition within the skin. Accumulated thermal damage is estimated by using an Arrhenius type rate equation at locations where viable tissue temperature exceeds 42°C. Prediction of spatial temperature distributions is also illustrated with a two-dimensional model of skin created from a histological image. RESULTS: The transport lattice approach was validated by comparison with an analytical solution for a slab with homogeneous thermal properties and spatially distributed uniform sink held at constant temperatures at the ends. For typical transcutaneous blood gas sensing conditions the estimated damage is small, even with prolonged skin contact to a 45°C surface. Spatial heterogeneity in skin thermal properties leads to a non-uniform temperature distribution during a 10 GHz electromagnetic field exposure. A realistic two-dimensional model of the skin shows that tissue heterogeneity does not lead to a significant local temperature increase when heated by a hot wire tip. CONCLUSIONS: The heat transport system model of the skin was solved by exploiting the mathematical analogy between local thermal models and local electrical (charge transport) models, thereby allowing robust, circuit simulation software to obtain solutions to Kirchhoff's laws for the system model. Transport lattices allow systematic introduction of realistic geometry and spatially heterogeneous heat transport mechanisms. Local representations for both simple, passive functions and more complex local models can be easily and intuitively included into the system model of a tissue

A gender comparison of portuguese firefighters’ perceptions concerning personal protective equipment: results from a pilot study

Over the years, the nature of firefighting and the role of firefighters has evolved including a demographic change, with an increasing number of women in this profession. Recent studies have specifically addressed the particular needs of female firefighters. Ill-fitting turnout gear, protective gloves, and other personal protective equipment make female firefighters’ tasks not only uncomfortable but also more difficult and dangerous. A pilot study comprising both male and female firefighters from a fire brigade located in the North of Portugal was conducted. The goal was to investigate the fit of the Portuguese firefighters’ personal protective equipment, its level of adjustment to their anthropometrics and to identify areas that need improvement. This paper focuses on gender differences and presents the preliminary results regarding size selection and purchasing of protective clothing as well as the level of protection experienced among participants.We would like to acknowledge the 2C2T-Centre for Textile Science and Technology of the University of Minho. This work is financed by FEDER funds through the Competitive Factors Operational Program (COMPETE) POCI-01-0145-FEDER-007136, by national funds through the FCT-Portuguese Foundation for Science and Technology under the project UID/CTM/000264, by Fundo de Apoio às Vítimas dos Incêndios de Pedrógão, and by ICC/Lavoro. We would also like to acknowledge the United States North Central Multistate Research Project titled NC-170 for assistance developing the questionnaire