Analytical and experimental study on the use of skin temperature as a method of diagnosing impending tissue damage due to applied loads

Abstract

This study was undertaken to establish a theoretical and experimental base for the interpretation of skin temperature response to applied external loads. This information is applicable to the use of skin temperature as a diagnostic tool in the prevention of decubitus ulcers and related skin breakdown problems. An analytical model of heat transfer from the deep body core to the skin surface was developed. The model was based on the bio-heat equation in one-dimensional Cartesian co-ordinates. The model incorporated the parameters of importance to skin temperature elevation in living tissue. These parameters are blood perfusion, metabolic heat generation and heat conduction. The resulting non-homogeneous partial differential equation with non-homogeneous boundary conditions was solved under both transient and steady state conditions, using an exact analytical method for constant metabolic heat generation cases. The numerical method of Crank-Nicolson was used to solve additional cases of interest, including non-constant metabolic heat generation and non-constant blood flow. The numerical solutions were found to be convergent and agreed well with the exact analytical solution, for the solutions or cases compared. An experimental study was also undertaken to find out if skin temperature response due to applied loads could be generated in the Yorkshire pig. This study involved the use of 32 pigs for collecting skin temperature response data, after different magnitudes of loading had been applied to the iliac crest for various lengths of time. Biopsies were also taken for microscopic examination in order to determine the extent of damage produced by the loading. Also determined were the loaded and unloaded skin blood flow rates, using radioisotope techniques. The result of the animal experimental study showed that the Yorkshire pig could indeed be a good animal model for tissue breakdown studies. Skin temperature response of up to 1°C was observed in tissue that had been under a high magnitude loading of 5 psi (=258.5 mm Hg) or 8 psi (=413.7 mm Hg) for a long duration (4 or 6 hours)...