Deep body temperature from aural canal with servo-controlled heating to outer ear.

A portable battery-powered device was used to measure temperature in the external aural canal by a thermistor while keeping the temperature of the outer ear, monitored by a second thermistor at the same level by servo-controlled heating. Aural canal temperature then always stabilized within 0.35 degrees C of esophageal in moving air at between 18 and 45 degrees C. It often did so in colder air, but stabilization was slow even after brief exposure to the cold air. Aural temperature then paralleled esophageal within 0.35 degrees C during rapid changes in deep body temperature while rectal temperature was seriously depressed in cold air. These conclusions were based on 30 experiments on 11 male and 7 female subjects.