Lumped parameter tissue temperature - blood perfusion model of a cold-stressed finger tip. Shitzer, Avraham, Leander A. Stroschein, Richard R. Gonzalez, and Kent B. Pandolf. Department of Mechanical Engineering, Technion, Israel Institute of Technology, Haifa, Israel 2000, Biophysics and Biomedical Modeling Division, Environmental Physiology and Medicine Directorate, US Army Research Institute of Environmental Medicine, Natick, MA. 01760 -5007
APStracts 3:0029A, 1996.
A lumped parameter model of a finger tip is presented. The semi -spherical model includes the effects of heat storage, heat exchange with the environment and heat transport by blood perfusion. The thermal insulation on the surface of the finger tip is represented by the overall heat transfer coefficient which is calculated by common engineering formulae. The model is solved analytically for the simple case of constant blood perfusion rate. The general case of variable blood perfusion rates is solved by an Euler finite difference technique. At this stage the model does not include active control mechanisms of blood perfusion. Thus, the effects of cold induced vasodilatation (CIVD) have to be superimposed and are modeled by symmetrical triangular wave forms as these were found to best depict the behavior of fingers exposed to cold environments. Results of this model were compared to experimental data obtained in two separate studies. One included 60 minute infrared thermograms of the dorsal surface of bare hands, horizontally suspended on a fish-net of sedentary subjects in a 0oC environment. Another study, on gloved finger temperatures, involved 0oC and -6.7oC environments. Finger tip (nail bed) temperatures of both these studies were compared to model predictions. Blood perfusion rates were assumed and adjusted within physiologically reasonable limits. Comparison of measured and computed temperature records showed very good conformity in both cases studied. 

Received 26 July 1994; accepted in final form 12 December 1995.
APS Manuscript Number A764-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 January 96