The accuracy and precision of four infrared aural canal thermometers during cardiac surgery

Background: Four infrared aural canal thermometers are currently available in Japan: Genius(R), Thermoscan(R), Quickthermo(R), and Thermopit(R). We therefore tested the hypothesis that each is sufficiently accurate and precise for clinical use. Methods: For the purpose of this investigation, we considered accuracy to be the mean difference between the test thermometers and the reference thermocouple. Precision was considered to be the standard deviation of the difference between the test and reference values. We evaluated ten patients undergoing cardiopulmonary bypass with moderate hypothermia (approximate to 30 degrees C). Aural canal temperatures were measured in random order with each infrared thermometer, and compared with readings from a thermocouple positioned at the contralateral tympanic membrane. Results: Compared to the thermocouple, the Genius(R) and Thermoscan(R) both had regression slopes >0.85 and correlation coefficients near 0.87; in contrast, slopes of the Quickthermo(R) and Thermopit(R) regressions were 0.68 and 0.53, respectively. The correlation coefficients for each were <0.65. The accuracy (offset, or bias) was near 0 degrees C with both the Genius(R) and Thermoscan(R) thermometers. In contrast, it was 1.1 degrees C with the Quickthermo(R) and a full 2.3 degrees C with the Thermopit(R). The precision (standard deviation) of the measurements, however, was approximate to 0.8 degrees C in each case. Conclusion: We conclude that none of the tested aural canal infrared thermometers was sufficiently accurate and precise for perioperative use.