The Effect of Pressure on Skin Temperature Measurements for a Disk Sensor

In order to determine the effect of application pressure on the accuracy of skin temperature measurements for area contact sensors, low values of pressure (2-20 mm Hg) were applied to the mid-thigh and to the lateral aspect of the trochanter of human subjects using a thin, circular disk with a thermistor mounted in the base. From measurements of the local skin temperatures, it was determined that a pressure of 2 mm Hg is adequate to measure the skin temperature accurately. Applying larger pressure results in higher local skin temperatures with the thighs showing larger temperature increases than the trochanters. The results of a finite difference analysis indicate that the increases in skin temperature at higher pressures can be accounted for by the physical phenomena associated with the penetration of the sensor into the tissue. After the release of pressure, the local skin temperature immediately decreased for all subjects indicating little or no reactive hyperemia was occurring. A method of compensating for the changes in local skin temperature which are due to whole body transient thermal effects was also developed. Use of this method allows the effects of the local pressure application to be separated from the transient environmental effects.