Gastrointestinal thermal homogeneity and effect of cold water ingestion

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.

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.

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.

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.