THE INFLUENCE OF ATTACHMENT METHOD AND CLOTHING ON SKIN TEMPERATURE SENSOR ACCURACY

Abstract

Skin temperature (Tsk) is commonly measured with contact sensors taped to the skin. Due to it being exposed to both the skin and the environment, Tsk is a reflection of both actual skin temperature and also the surrounding environment. However, no standardization of attachment methods exists, with the majority of protocols simply stating that skin sensors were taped to the skin. Biophysically, taping the sensor should act similarly to an additional layer of clothing, providing a barrier to heat exchange. Therefore, tapes with different thermal characteristics may influence the accuracy of Tsk measurement. This study investigated the separate and combined effects of Tsk attachment methods and clothing insulation on Tsk accuracy. On the arm of a Thermal Instrumented Manikin (TIM), thermocouples (YSI 499B) were attached using either waterproof tape (Elastoplast), surgical tape (Transpore), or a rubber ring that secured the thermocouples without covering it. Measurements of Tsk were taken with the manikin temperature (TTIM) set to 32–40°C in 2°C increments. Three levels of clothing insulation were tested: 1) nude, 2) cotton flannel shirt (1.0 clo), and a marine immersion survival suit (2.2 clo). Ambient temperature was 21°C for all trials. All conditions produced Tsk readings that were significantly lower than the actual manikin temperature. In the nude trial, as TTIM increased from 32–40°C, Tsk error increased from −1.4 to −1.7°C for Ring. This was significantly less than the errors for Surgical (−1.5 to −2.1°C) and Waterproof (−1.4 to 2.1°C). With the cotton clothing, Tsk measured −1.0 to −1.4°C, −1.2 to −1.6°C, and −1.3 to −2.0°C for Ring, Surgical, and Waterproof attachment, respectively. With the survival suit, Tsk measured −0.9 to −1.3°C, −1.0 to −1.4°C, and −1.1 to −1.7°C for Ring, Surgical, and Waterproof attachment, respectively. The conclusions from this study are as follows: Tsk measured using contact sensors underestimated the actual skin surface temperature in a thermoneutral environment, with the magnitude of the error increasing with an increase in the thermal gradient between the skin and the environment. An increase in clothing insulation results in a decrease in Tsk error, likely due to increased heat retention around the sensor and a subsequent decrease in the thermal gradient. Tsk is influenced by the attachment method, with the least error when attached by a ring. It is recommended that consideration be given to standardizing attachment methods for contact skin sensors.