Accurate monitoring of core body temperature is integral to targeted temperature management (TTM) following cardiac arrest. However, there are no reliable non-invasive methods for monitoring temperature during TTM. We compared the accuracy and precision of a novel non-invasive Zero-Heat Flux Thermometer (SpotOnä) to a standard invasive esophageal probe in a cohort of patients undergoing TTM post cardiac arrest.
We prospectively enrolled 20 patients undergoing post-cardiac arrest care in the intensive care units at the London Health Sciences Centre in London, Canada. A SpotOnä probe was applied on each patient’s forehead, while an esophageal temperature probe was inserted, and both temperature readings were recorded at 1-minute intervals for the duration of TTM. We compared the SpotOnä and esophageal monitors using Bland-Altman analysis and Pearson correlation, with accuracy set as a primary outcome. Secondary outcomes included precision and correlation. Bias exceeding 0.1°C and limits of agreement exceeding 0.5°C were considered clinically important.
Sixteen (80%) of patients had complete data used in the final analysis. The median (interquartile range) duration of recording was 38 (12-56) hours. Compared to the esophageal probe, SpotOnä had a bias of 0.05 ± 0.35ºC and 95% limits of agreement of -0.64 to 0.74 ºC. Pearson correlation coefficient was 0.98 (95% confidence interval 0.9796-0.9805), with a two-tailed p-value of <0.0001.
The SpotOnä is an accurate method that may enable non-invasive monitoring of core body temperature during TTM, although its precision is slightly worse than the pre-defined 0.5°C when compared to invasive esophageal probe.