The accuracy of zero-flux and ingestible thermometry in the peri-operative setting

Relevance of research:  Accurately monitoring core temperature during anaesthesia is a cornerstone of good practice. Relatively invasive devices such as oesophageal temperature probes and pulmonary artery flotation catheters allow accurate measurement of core temperature. However these are not appropriate for many patients. There is a need for accurate non-invasive measurement of core temperature. 

Background and Goal of Study:  This study was designed to compare the accuracy of two new non-invasive core temperature thermometers, the 3M SpotOn™ Temperature Monitoring System Zero Flux Device (ZFD) and the CorTempR Wireless Ingestible Temperature Sensor (ITS) with the oesophageal temperature probe (OTP), which is the current introperative standard.

Materials and Methods: 20 patients scheduled for elective surgical procedures under general anaesthesia were recruited to the study. Prior to induction patients ingested an ITS, and after induction a ZFD was attached above their right eyebrow.  During surgery temperature on each device was recorded every minute. Data were compared using Bland Altman analysis.

Results and Discussion:  The ITS experienced considerable interference from equipment used in the operating theatre, including diathermy and fluoroscopy, rendering around 30% of its readings redundant. These were removed from subsequent analysis.  The bias for the ZFD compared to OTP was 0.024 and the 95% limits of agreement -0.47 to 0.52. 97.7% of readings are within +/-0.5C of the probe reading.  With erroneous readings removed, the bias for the ITS when compared with the OTP was 0.42 and the 95% limits of agreement -2.4 to 3.2. 75.4% of readings were within +/-0.5C of the OTP reading.  Bland Altman analysis found good concordance between the ZFD and OTP.

Conclusions: The results of this study suggest the ZFD is an accurate non-invasive measure of core temperature, whereas the ITS is not suitable for perioperative practice.

A study to determine the accuracy of zero-flux and ingestible thermometers in the perioperative setting