The vagaries of ear temperature assessment

Abstract

There have been a growing number of reports suggesting that ear temperature measurement is unreliable and by implication so is the device. Examination of the measurement site, the tympanic membrane (eardrum) and the walls of the external auditory meatus (ear canal) reveals that at least some of the unreliability might derive from poor aiming of the infrared thermometer: the ear canal walls have a lower temperature than the eardrum. Additionally, anatomical properties of the ear canal may increase the difficulty of aiming the thermometer at the eardrum. Furthermore, the rich vascularization, innervation and variations in skin properties (thickness, oil secretion and hair) along the length of the ear canal affect the black body-like nature of the structure. It is concluded that such factors are more likely underlying reasons for the difficulties in reliably reproducing temperatures from this site. We conclude that concerns should extend beyond the reliability of the device and there should be greater study of the measurement site. The argument extends to all sites chosen for clinical assessment of the patient, as previous studies of the alternative temperature measurement sites are also unfortunately few and tend to be lacking in scientific rigour.

Enhancement of the finger cold-induced vasodilation response with exercise training

“…In our study, we defined the thermal status of the participants from the measurement of T ear canal , which is an index of core temperature, and the T avg prior to the immersion in warm water. Although there have been serious concerns raised regarding the accuracy and reliability of infrared tympanic thermometry (McCarthy and Heusch 2006;Romanovsky et al 1997), Mekjavic et al (1992) have reported good correlation of tympanic temperature with oesophageal (r = 0.96 ± 0.02) and rectal (r = 0.95 ± 0.03) temperatures during cooling of subjects to mildly hypothermic levels and subsequent rewarming. Since we observed no changes in T ear canal and T avg prior to the immersion of the hand in 35°C water, during the four testing periods, we can assume that the subjects' thermal status had not altered during the training period, and it therefore did not affect the CIVD response.…”

Central Hyperthermia in Acute Stroke

“…In patients with consciousness disturbance, rectal measurement should be considered [8, 24]. However, this was a retrospective study, and in our hospital rectal temperature is usually measured in pediatric patients and ear temperature is recorded for adult patients.…”

Evidence Utilisation Project: Management of Inadvertent Perioperative Hypothermia. The challenges of implementing best practice recommendations in the perioperative environment

“…30 The presence of ear wax or hair, along with ear canal anatomy variations, can also decrease accuracy. 31 In any case, some argue that these devices are unable to be inserted far enough into the ear canal to easily obtain a tympanic reading. 26 At the project commencement, devices had been calibrated and set to 'ear' mode, which provides an unadjusted peripheral temperature reading within the ear canal.…”