Thomas K A, Savage M V, Brengelmann G L
Department of Family-Child Nursing, University of Washington, Seattle, USA.
Am J Crit Care. 1997 Jan;6(1):46-51.
In clinical practice, tympanic temperature is used as an estimate of body temperature. Theoretically, temperature recorded directly from the tympanum reflects the temperature of arterial blood circulating to the brain. However, some studies do not support this connection. Ear-based thermometers in clinical use, commonly called tympanic thermometers, detect heat emission from the aural canal and tympanum. Dissociation of core body temperature and tympanic temperature would suggest that factors other than arterial blood perfusion affect tympanic temperature.
In a controlled laboratory experiment with four adult volunteers, esophageal and tympanic temperatures were recorded repeatedly at 2-minute intervals during whole-body heating and cooling. Facial cooling, produced by a small electrical fan, was used in three subjects.
The gradient between tympanic and esophageal temperature was inconsistent across subjects, with tympanic temperature both higher and lower than esophageal temperature. Correlations between esophageal and tympanic temperature varied widely across subjects. Fanning the face produced a decrease in tympanic temperature without an accompanying decline in esophageal temperature.
Facial cooling in the form of fanning altered the relationship between tympanic and esophageal temperature. This result suggests the possible lowering of tympanic temperature by cooled facial venous blood flow. Use of tympanic temperature in circumstances in which facial temperature may be different from that of other regions of the body deserves further study.
