Tympanic temperature measurement through the ear
canal is commonly used as it is thought to accurately
reflect the hypothalamic temperature. However, a metaanalysis
published in 2002 demonstrated a poor tympanic-
rectal correlation (Craig et al, 2002). Tympanic
thermometers usually rely on infra-red to detect radiant
heat—therefore the presence of ear wax will impair their
accuracy. Other techniques include the use of thermistors
attached to central venous or pulmonary artery
catheters, urinary catheters and intracranial probes.
Temporal artery scanning has been shown to correlate
more closely with brain parenchymal temperature than
tympanic measurement (Kirk et al, 2009), but has been
repeatedly shown to be poorly correlated with other
temperatures, in particular rectal measurements, and
may be unreliable in the face of high body mass index
(BMI)