Wireless measurement of rectal temperature during exercise: Comparing an ingestible thermometric telemetric pill used as a suppository against a conventional rectal probe

Wireless measurement of rectal temperature during exercise may circumvent some limitations associated with the use of a conventional wired probe. We determined, for the first time, whether temperatures provided in vivo by wireless ingestible thermometric telemetric pills and a rectal probe compare favorably under conditions producing slow and rapid increases and decreases in rectal temperature. While wearing a rectal probe linked to a wireless ingestible thermometric telemetric pill, 13 participants completed the following phases: 1) 30 min sitting; 2) 45 min passive heat exposure (40-42 degrees C); 3) 45 min sitting while ingesting 7.5 g of ice slurry . kg body mass(-1); 4) running exercise (38 degrees C) at 68% (V) over dot O-2max until a 39.5 degrees C increase in rectal probe temperature and; 5) cold-water (10 degrees C) immersion until a 1.5 degrees C decrease in rectal probe temperature. Acceptable differences between devices were taken as <= 0.3 degrees C. Mean differences within phases were all < 0.3 degrees C, whereas 95% limits of agreement ranged from +/- 0.2 degrees C to +/- 0.4 degrees C, coefficient of variations from +/- 0.3% to +/- 0.6% and typical error of measurements from +/- 0.1 degrees C to +/- 0.2 degrees. Of the 14881 rectal temperature values measured over the experiment with the wireless ingestible thermometric telemetric pills and rectal probe, 91% of the differences between devices were found to be <= 0.3 degrees C. Results suggest that rectal temperatures provided by a wireless ingestible thermometric telemetric pill used as a suppository agree with those of a conventional wired probe. Hence, rectal temperature can reliably be measured using a wireless ingestible thermometric telemetric pill as a suppository.