An Overnight Comparison of Core Temperature Using a Rectal Probe and a Radio Pill.

Abstract : Previous efforts to record core temperature with radio pills produced consistent results showing that core temperature provided by radio pill tended to be lower than that provided by rectal probe by about 0.5c to o.6c Part of this temperature difference (about 0.2c to 0.3c) was thought to be due to the fact that as the radio pill courses through the gut it passes through areas of differing vasculature, perfusion, and metabolism which result in slightly varying local core temperatures. The studies which produced these results were generally monitoring subjects for 3 to 4 hours. There was very little information as to the efficacy of the radio pill with respect to its ability to track the daily circadian temperature trough, which is a pre-requisite to successful work in the domain of circadian rhythms. This study is an attempt to evaluate the radio pill against the rectal probe, over 15 hours, in order to determine whether or not the radio pill is sensitive enough to discriminate the circadian temperature trough. Methods. Resting core temperatures provided by radio pill and by rectal probe, were monitored in 7 subjects over 15 hours, including the overnight period. The rectal probe and its data logger were the standard units used in this laboratory. The radio pill and its data logger were recently improved units lent to us by their manufacturers for evaluation. The data loggers for each of the rectal probes and the radio pills were set to collect data every minute. The subjects wore the data loggers (for each of the pill and probe) on a belt throughout the 15 hour time block. The data from the 7 subjects were submitted to a double repeated-measures analysis of variance (anova).