Influence of esophageal temperature probe tip placement on core temperature measurement accuracy in cold...

Accurate core temperature (CT) measurement is critical for staging and management in accidental hypothermia, particularly in cardiac arrest, where it guides extracorporeal rewarming decisions. Esophageal temperature monitoring is considered the reference method in the prehospital setting in patients with a secured airway, provided the probe tip is positioned in the distal third of the esophagus behind the heart. However, the effect of proximal misplacement on measurement accuracy remains unknown. We hypothesized that a probe tip positioned behind the trachea would yield falsely low readings during cold air exposure.

In this randomized crossover study (May 2024 at Eurac Research, Bolzano, Italy), healthy volunteers underwent nasal esophageal probe placement using a height-based formula. Two probe positions were defined via posteroanterior chest radiographs: correct (behind the heart) and incorrect (5 cm above the tracheal bifurcation). Participants were exposed to -20 °C for 20 min in a climate chamber, once with the probe in the correct and once in the incorrect position, in randomized order, separated by a washout period.

Fifteen participants (7 male, 8 female) completed the study. Mean correct insertion depth was 41.1 (2.5) cm for males and 39.3 (1.5) cm for females. At baseline and throughout -20 °C exposure, mean CT was on average 0.6 °C lower when the probe was incorrectly positioned. Temperature fluctuations were also greater with proximal misplacement.

Proximal misplacement of esophageal probes during cold air exposure results in falsely low and more variable CT readings. This may critically affect triage and treatment, particularly in hypothermic cardiac arrest.