Comparison of ear‐based, bladder, oral, and axillary methods for core temperature measurement

To determine the accuracy and repeatability of ear-based, bladder, oral, and axillary temperature methods. Design:Prospective, descriptive comparison of the accuracy of four temperature methods in relation to pulmonary artery temperature and the repeatability of each method. Setting:Critical care units of a university teaching hospital. Patients:Convenience sample of 38 adult patients with indwelling pulmonary artery thermistor catheters. Interventions:None. Measurements and Main Results:Ear-based estimates of core temperature with an infrared thermometer and pulmonary artery, bladder, oral, and axillary temperatures with thermistor-based instruments were made every 20 mins for 4 hrs. Mean offsets (± SD) from pulmonary artery temperature for each method were as follows: ear-based 0.07 ± 0.41°C; bladder 0.03 ± 0.23°C; oral 0.05 ± 0.26°C; and axillary −0.68 ± 0.57°C. The accuracy of each method varied with the level of pulmonary artery temperature. Repeated measurements with all four methods had mean SD values within ±0.2°C. Conclusions:Infrared ear thermometry provided a relatively close estimate of pulmonary artery core temperature, although with more variability than bladder or oral methods, while axillary readings were substantially lower than the pulmonary artery temperature and highly variable. (Crit Care Med 1993; 21:1528–1534)