Evaluation of the novel non-invasive zero-heat-flux Tcore™ thermometer in cardiac surgical patients

Tcore™ Sensor is a novel zero-heat-flux thermometer that estimates core temperature from skin over forehead. We tested the hypothesis that this system estimates core temperature to an accuracy within 0.5 °C. 40 cardiac surgical patients were enrolled (960 measurements). Reference core temperatures were measured in nasopharynx, pulmonary artery and the arterial branch of the oxygenator of the cardiopulmonary bypass (CPB) circuit. 95% Bland–Altman limits of agreement for repeated measurement data was used to study the agreement between Tcore™ thermometer and the reference methods. The proportion of all differences that were within 0.5 °C and Lin’s concordance correlation coefficient (LCCC) were estimated as well. The mean overall difference between Tcore™ and nasopharyngeal temperature was − 0.2 ± 0.5 °C (95% limits of agreement of ± 1.09). The proportion of differences within 0.5 °C was 68.80% (95% CI 65.70–71.70%) for nasopharyngeal reference. LCCC was 0.84 (95% CI 0.83–0.86). The mean bias between Tcore™ and the temperature measured in the pulmonary artery was − 0.2 ± 0.5 °C (95% limits of agreement of ± 1.16). 55.30% of measurements were ≤ 0.5 °C (95% CI 51.40–59.20%). LCCC was 0.60 (95% CI 0.56–0.64). The average difference between Tcore™ and the temperature measured at the arterial outlet during the CPB period was − 0.1 ± 0.7 °C (95% limits of agreement of ± 1.43). The proportion of differences within 0.5 °C was 54.40% (95% CI 48.80–60.00%). LCCC was 0.74 (0.69–0.79). Cutaneous forehead zero-flux temperatures were not sufficiently accurate for routine clinical use in the cardiac surgical population.