Re-visiting the tympanic membrane vicinity as core body temperature measurement site

Abstract

Core body temperature (CBT) is an important and commonly used indicator of human health and endurance performance. A rise in baseline CBT can be attributed to an onset of flu, infection or even thermoregulatory failure when it becomes excessive. Sites which have been used for measurement of CBT include the pulmonary artery, the esophagus, the rectum and the tympanic membrane. Among them, the tympanic membrane is an attractive measurement site for CBT due to its unobtrusive nature and ease of measurement facilitated, especially when continuous CBT measurements are needed for monitoring such as during military, occupational and sporting settings. However, to-date, there are still polarizing views on the suitability of tympanic membrane as a CBT site. This paper will revisit a number of key unresolved issues in the literature and also presents, for the first time, a benchmark of the middle ear temperature against temperature measurements from other sites. Results from experiments carried out on human and primate subjects will be presented to draw a fresh set of insights against the backdrop of hypotheses and controversies.

Fig 1. Measurement spot on the tympanic membrane.

Tympanic membrane of the right ear showing a temperature measurement spot at the lower anterior quarter (pointed by the arrow).

Fig 2. Temperature uniformity maps.

Temperature uniformity maps of the left ear: (a) without face cooling and (b) without face cooling.

Fig 3. Human ear model.

Human Ear Model used in Finite Element Analysis.

Fig 4. FEA results.

FEA showing temperature uniformity: (a) on the tympanic membrane and (b) at 1mm above the tympanic membrane.

Fig 5. Temperature measurement points for Experiment 1.

Tympanic membrane of the right ear with temperature measuring points labeled as A, B and C.

Fig 6. Modified clinical tympanic membrane probe.

Clinical tympanic membrane probe supplied by Exacon Scientific A/S retrofitted with a Keyence Reflective Fibre Unit for use in Experiment 1.

Fig 7. Custom heating chamber.

Custom heating chamber constructed for use in Experiments 2–3.

Fig 8. Temperature measurements results from Experiment 2.

Primate body temperature measurements with Esophageal, Rectal and Tympanic Membrane (Left TM and Right TM) Temperatures plots. Experiment results are split into two test scenarios for Experiment 2: (1) X—Full Body Hyperthermia, and (2) Y—Full Body Hyperthermia with Left Face Fanning.

Fig 9. Temperature measurements results from Experiment 3A.

T_rm, T_me and T_tm,R vs. Time plots that depict behavior of each measurement site in Experiment 3A (No general anesthesia disruption).

Fig 10. Temperature measurements results from Experiment 3B.

T_rm, T_me, T_tm,R and T_es vs. Time plots that depict behavior of each measurement site with general anesthesia being disrupted in Experiment 3B.