title: The impact of environmental factors in pre-hospital thermistor-based tympanic temperature measurement: a pilot field study.
abstract: BACKGROUND
  Few pre-hospital services have the possibility to accurately measure core temperature (T core). Non-invasive estimation of T core will improve pre-hospital decision-making regarding the triage and management of hypothermic patients. Thermistor-based tympanic temperature (T tymp) correlates well with T core in controlled studies; however, little is known about the feasibility of using T tymp under field conditions. This study assessed the impact of pre-hospital environmental factors on the accuracy of T tymp . Deep rectal temperature (T rect) was used as a substitute for T core .
  
  
  METHODS
  Normothermic volunteers (n = 13) were exposed to four simulated field conditions producing local cooling of the head and ear canal. After exposure, T tymp was recorded every 15 s for 10 min and compared with T rect . Descriptive analysis and Bland-Altman plots were used to assess agreement.
  
  
  RESULTS
  Immediately after exposure mean T tymp was low, but increased rapidly and reached an apparent steady state after 3-5 min. After 5 and 10 min, the mean temperature difference (∆T rect-tymp) ranged from 1.5-3.2 °C (SD = 0.5) and 1.2-2.0 °C, respectively. T rect remained unchanged throughout the study period.
  
  
  CONCLUSIONS
  After surface cooling of head and neck, T tymp did not accurately reflect core temperature within the first 10 min of measurement. The variation of ∆T rect-tymp was low after 10 min, regardless of the initial degree of cooling. With the risk of over-triage, T tymp may at this point provide an indication of T core and also exhibit a trend.
  
  
  BACKGROUND
  ClinicalTrials.gov: NCT02274597.
authors.affiliation: Department of Anaesthesia & Intensive Care, Oslo University Hospital, N 0424, Oslo, Norway. scskaiaa@gmail.com.
authors.forename: Sven Christjar
authors.initials: SC
authors.lastname: Skaiaa
authors.affiliation: Department of Anaesthesia & Intensive Care, Haukeland University Hospital, N 5021, Bergen, Norway. guttorm.brattebo@helse-bergen.no.
authors.forename: Guttorm
authors.initials: G
authors.lastname: Brattebø
authors.affiliation: Centre for Clinical Research, Haukeland University Hospital, N 5021, Bergen, Norway. jorg.assmus@helse-bergen.no.
authors.forename: Jörg
authors.initials: J
authors.lastname: Aßmus
authors.affiliation: Department of Anaesthesia & Intensive Care, Haukeland University Hospital, N 5021, Bergen, Norway. oyvind.thomassen1@helse-bergen.no.
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Thomassen
mesh_terms: D000328:Adult; D001831:Body Temperature; D004632:Emergency Medical Services / Q000379:methods*; D004777:Environment; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007035:Hypothermia / Q000175:diagnosis* / Q000628:therapy; D008297:Male; D017145:Models, Educational; D010865:Pilot Projects; D018570:Risk Assessment; D013821:Thermometers; D062125:Thermometry / Q000379:methods*; D014432:Tympanic Membrane / Q000502:physiology*