Core temperature response to cycling exercise: Effect of time of day and measurement site

Validation of e-Celsius gastrointestinal telemetry system as measure of core temperature

The main objective of this study was to validate gastrointestinal measurement with the e-Celsius® system composed of an ingestible electronic capsule and a monitor. Twenty-three healthy volunteers aged 18-59 years stayed at the hospital for 24 h under fasting conditions. They were only allowed for quiet activity and were asked to keep their sleeping habits. Subjects ingested a Jonah capsule and an e-Celsius® capsule, and a rectal probe and an esophageal probe were inserted. Mean temperature measured by the e-Celsius® device was lower than that measured by Vitalsense® (-0.12 ± 0.22°C; p < 0.001) and the rectal probe (-0.11 ± 0.03°C; p = 0.003) and higher than that measured by the esophageal probe (0.17 ± 0.05; p = 0.006). Mean difference (bias) and 95% confidence intervals between temperature of e-Celsius capsule, Vitalsense Jonah capsule, esophageal probe, and rectal probe were computed using Bland and Altman procedure. The magnitude of the measurement bias is significantly greater when comparing the e-Celsius® and the Vitalsense® device pair with any other device pairs containing the esophageal probe. Amplitude of confidence interval between the e-Celsius® system and the Vitalsense® system was 0.67°C. This amplitude was significantly lower than those of the esophageal probe-e-Celsius® pairing (0.83°C; p = 0.027), of the esophageal probe-Vitalsense (0.78°C; p = 0.046) and of the esophageal probe-rectal probe (0.83°C; p = 0.002). The statistical analysis did not reveal any effect of time on the amplitude of bias, whatever the device concerned. When comparing missing data rate of the e-Celsius® system (0.23 ± 0.15%) and the Vitalsense® devices (0.70 ± 0.11%) during the whole experiment, no differences was observed (p = 0.09). The e-Celsius® system could be used when a continuous following of internal temperature is needed.

Gastrointestinal thermal homogeneity and effect of cold water ingestion

PURPOSE

Gastrointestinal temperature (GIT) is a common alternative for body core temperature (CT) monitoring via an ingestible pill connected to an external monitor. However, its reliability could depend on thermal homogeneity, regardless of the gastrointestinal tract location. The purpose of this study was to evaluate GIT variation during the transit of telemetric pills and the impact of cold drink ingestion compared to the time point of pill intake.

METHODS

Twenty-three healthy participants ingested six e-Celsius electronic pills, one every five hours, and they ingested 150 milliliters of cold water (5 +/- 1 °C) 1, 2, 3, 4, 8, and 12 h following the first pill ingestion.

RESULTS

The recorded temperature remained similar between pills consecutively ingested by each subject, regardless of the internal location within the gastrointestinal tract, supporting the homogeneity of GIT. GIT monitoring was significantly affected by ingestion of a cold drink two hours (-0.8 ± 0.2 °C; p = 0.001) and three hours following pill ingestion (-0.9 ± 0.2 °C; p < 0.001) in all subjects, and abnormal drops in GIT were observed in 22% of subjects up to twelve hours following pill ingestion.

CONCLUSION

Temperature may be considered homogenous all along the internal intestinal tract and correlates with CT, supporting telemetric monitoring as an efficient method for monitoring temperature. The interaction between GIT measurements and substance intake has to be taken into account. To avoid the effect of substance ingestion on CT data, we recommend users to employ the pill as a rectal suppository or to mark every substance ingestion time and/or allow only tepid water and food intake.