Background There is no reliable, minimally invasive, and fast method to measure core temperature in a pre-hospital-care. Nasopharyngeal temperature probe (NPTP) would allow continuous temperature monitoring while treating a patient, but its reliability on spontaneously breathing patients remains unclear.

The study aims to evaluate, whether NPTP monitoring for core temperature is reliable with spontaneously breathing patients, in different environments.

Method 47 healthy, ambulatory volunteers were recruited for the study. We measured ear and nasopharynx temperatures using a standard ear thermometer and nasopharyngeal temperature probe. Ear temperature was used as a reference due to its practicality and noninvasiveness. Ear and nasopharyngeal temperatures were measured in 5 different scenarios: room temperature (+22 °C), cold environment (-5 °C) after 5, 10 and 15 minutes of exposure and in a hot environment (+65 °C) after 15 minutes of exposure.

We used Bland-Altman-analysis to compare measurements.

Results We gathered a total of 235 ear temperature values and 235 nasopharynx temperature values. Due to a thermometer malfunction, 7 (3.0%) ear temperature values were excluded, leaving a total of 228 temperature value pairs for final analysis.

Bland-Altman-analysis showed a clinically significant positive bias between ear thermometer and NPTP, in all the environments. In room temperature mean difference was 1.90 with limits of agreement -0,00 to 3.81, in cold 3.20 (-0.62 to 7.03), and in hot 1.81 (0.55 to 3.07).

Conclusion According to our findings, nasopharynx temperature is not a reliable method to measure core temperature in spontaneous breathing patients.

Conflict of interest None declared.

Funding None declared.