title: Influence of low ambient temperature on epitympanic temperature measurement: a prospective randomized clinical study.
abstract: BACKGROUND
  Epitympanic temperature (Tty) measured with thermistor probes correlates with core body temperature (Tcore), but the reliability of measurements at low ambient temperature is unknown. The aim of this study was to determine if commercially-available thermistor-based Tty reflects Tcore in low ambient temperature and if Tty is influenced by insulation of the ear.
  
  
  METHODS
  Thirty-one participants (two females) were exposed to room (23.2 ± 0.4 °C) and low (-18.7 ± 1.0 °C) ambient temperature for 10 min using a randomized cross-over design. Tty was measured using an epitympanic probe (M1024233, GE Healthcare Finland Oy) and oesophageal temperature (Tes) with an oesophageal probe (M1024229, GE Healthcare Finland Oy) inserted into the lower third of the oesophagus. Ten participants wore ear protectors (Arton 2200, Emil Lux GmbH & Co. KG, Wermelskirchen, Switzerland) to insulate the ear from ambient air.
  
  
  RESULTS
  During exposure to room temperature, mean Tty increased from 33.4 ± 1.5 to 34.2 ± 0.8 °C without insulation of the ear and from 35.0 ± 0.8 to 35.5 ± 0.7 °C with insulation. During exposure to low ambient temperature, mean Tty decreased from 32.4 ± 1.6 to 28.5 ± 2.0 °C without insulation and from 35.6 ± 0.6 to 35.2 ± 0.9 °C with insulation. The difference between Tty and Tes at low ambient temperature was reduced by 82% (from 7.2 to 1.3 °C) with insulation of the ear.
  
  
  CONCLUSIONS
  Epitympanic temperature measurements are influenced by ambient temperature and deviate from Tes at room and low ambient temperature. Insulating the ear with ear protectors markedly reduced the difference between Tty and Tes and improved the stability of measurements. The use of models to correct Tty may be possible, but results should be validated in larger studies.
authors.affiliation: EURAC Institute of Mountain Emergency Medicine, Bolzano, Italy. giacomo.strapazzon@eurac.edu.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Strapazzon
authors.affiliation: EURAC Institute of Mountain Emergency Medicine, Bolzano, Italy.
authors.forename: Emily
authors.initials: E
authors.lastname: Procter
authors.affiliation: Department of Anaesthesiology and Critical Care Medicine, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Putzer
authors.affiliation: EURAC Institute of Mountain Emergency Medicine, Bolzano, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Avancini
authors.affiliation: EURAC Institute of Mountain Emergency Medicine, Bolzano, Italy.
authors.forename: Tomas
authors.initials: T
authors.lastname: Dal Cappello
authors.affiliation: Department of Otolaryngology, General Hospital of Bressanone, Bressanone, Italy.
authors.forename: Norbert
authors.initials: N
authors.lastname: Überbacher
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, General Hospital of Silandro, Silandro, Italy.
authors.forename: Georg
authors.initials: G
authors.lastname: Hofer
authors.affiliation: Department of Anaesthesiology, Marienklinik, Bolzano, Italy.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Rainer
authors.affiliation: Department of Anaesthesiology and Critical Care Medicine, General Hospital of Bressanone, Bressanone, Italy.
authors.forename: Georg
authors.initials: G
authors.lastname: Rammlmair
authors.affiliation: EURAC Institute of Mountain Emergency Medicine, Bolzano, Italy.
authors.forename: Hermann
authors.initials: H
authors.lastname: Brugger
mesh_terms: D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D003080:Cold Temperature; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D012881:Skin Temperature / Q000502:physiology; D013821:Thermometers; D062125:Thermometry / Q000379:methods*; D014432:Tympanic Membrane / Q000502:physiology*; D055815:Young Adult