The impact of environmental factors in pre-hospital thermistor-based tympanic temperature measurement: a pilot field study

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. TRIAL REGISTRATION ClinicalTrials.gov: NCT02274597.