Non-invasive zero-heat-flux technology compared with traditional core temperature measurements in the emergency...

Core temperatures (T_core) are often invasive, and can be underutilized. Peripheral temperatures are easier to obtain, but are often less accurate. A zero-heat-flux thermometer (ZHF) is a non-invasive method to obtain core temperatures (T_ZHF), and has been accurate when compared to T_core in the operating room. We aimed to determine whether T_ZHF accurately and reliably measures T_core in emergency department (ED) patients when compared to rectal, bladder or esophageal temperatures.

We conducted a prospective observational quality improvement project, with concurrent T_ZHF and T_core measurements. The primary outcome was whether one device detected a fever (≥38.1 °C) when the other device did not. Unadjusted linear regression was used to determine the relationship between temperature differences between devices.

268 patients were included. Mean temperatures were 36.6 °C for T_core and 36.3 °C for T_ZHF. 16 of 52 patients with fever identified by T_core were not detected by T_ZHF, 13 with an infectious etiology. The mean temperature difference between T_core and T_ZHF increased as the patient's temperature increased; the difference was 0.2 °C in afebrile patients, but 0.7 °C in febrile patients.

While we found overall concordance between T_core and T_ZHF, the ZHF did not detect fever in 25% of patients presenting with fever of infectious origin. Measurements between T_core and T_ZHF varied more as temperatures increased, with T_ZHF consistently reporting lower values. Although more study is needed, these findings call into question the use of T_ZHF in the ED where detection of fever frequently guides patient evaluation and management.