Ilkka Heikkilae

Skin temperature profiles on the human chest and in the wrist area

Skin temperatures on the chest and in the wrist area are interesting for continuous monitoring because they can be easily instrumented using an elastic belt or wristband which do not hamper movement in sports, for example. An infrared thermograph camera and NTC thermistors were used to take temperature profiles at these sensing points with a resolution of 0.1 degrees Celsius, and colored thermograms were used to analyze and compare the results. The effect of environmental changes on the skin temperature in the wrist area was studied by cooling and heating the fingers in water at 10 degrees Celsius and 40 degrees Celsius, and the effects of a loading situation on the chest area and wrist area were tested by means of a 30 min bicycle ergometer exercise. NTC thermistors were also used to measure wrist and chest temperatures in two environmental tests at minus 10 degrees Celsius and plus 60 degrees Celsius. Cooling of the fingers naturally reduces the skin temperature in the wrist area and heating increases it due to the venous circulation. The area of the radial artery in the wrist seems to be the most stable temperature point, altering by only about 2 degrees Celsius, whereas the temperature change at other points is up to 4 degrees Celsius. The bicycle ergometer exercise caused a decrease in skin temperature on the chest because of sweating. At the same time the skin temperature on the wrist decreased by about 1.5 degrees Celsius after the first 20 minutes and then returned to its previous level. The area of the radial artery in the wrist seems to be an attractive point for continuous temperature monitoring, especially under normal conditions, and also seems to reflect body temperature quite well upon loading and under different environmental conditions.