Twenty-four hour monitoring of deep body temperature with a novel flexible probe

A portable thermomemory unit with a light, thin and flexible probe has been developed for the measurement of whole-day variations in deep body temperature. The probe consists of a thermistor, a heat-flow sensor and a heater. The probe detects heat flow from the skin; the heater then compensates for the heat lost and consequently the skin is effectively insulated from the ambient microenvironment. Skin temperature beneath the probe is therefore determined by the deep body temperature. The probe is 46 mm in diameter and 3 mm thick, its weight is 5 g. The probe is light and flexible and makes close contact with the skin. A 2 kbyte RAM in the unit enables up to 34 h of data to be collected with a sampling rate of once per minute. The device was applied to the chest and abdominal walls, and to the calf; the chest and abdominal deep body temperatures showed a significant dual phase diurnal variation, usually being low during sleep. In contrast, the calf showed a dynamic deep body temperature variation which depended on the amount of leg exercise. The device was found to be effective for analysing daily variations; measurements on the limbs suggested that it could be used for monitoring peripheral circulatory disorders.