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. 2005 Jul-Sep;40(3):207-10.

The uncertainty (validity and reliability) of three electrothermometers in therapeutic modality research

Lisa S Jutte  1 , Kenneth L Knight, Blaine C Long, Jeremy R Hawkins, Shane S Schulthies, Ethan B Dalley
Affiliations

The uncertainty (validity and reliability) of three electrothermometers in therapeutic modality research

Lisa S Jutte et al. J Athl Train. 2005 Jul-Sep.

Abstract

Context: Data from electrothermometers are used to determine therapeutic modality usage, but the value of experimental results is only as good as the data collected.

Objective: To determine the reliability and validity of 3 electrothermometers from 2 manufacturers.

Design: A 3 x 4 x 17 factorial with repeated measures on 2 factors. Independent variables were trial (1, 2, 3), thermometer (mercury thermometer, Iso-Thermex calibrated from -50 degrees C to 50 degrees C, Iso-Thermex calibrated from -20 degrees C to 80 degrees C, and Datalogger), and time (17).

Setting: Human Performance Research Center.

Intervention(s): Eighteen thermocouples were inserted through the wall of a foamed polystyrene cooler, and 6 were connected to each of the 3 electrothermometers. The cooler was positioned on a stir plate and filled with room-temperature water (18.4 degrees C). A mercury thermometer was immersed into the water bath. Measurements of the water bath were taken every 10 seconds for three 3-minute trials.

Main outcome measure(s): The temperature variability of 3 electrothermometers was taken from a calibrated mercury thermometer.

Results: The Iso-Thermex electrothermometers did not differ statistically from each other in uncertainty (validity error +/- reliability error = 0.06 degrees C +/- 0.03 degrees C +/- 0.03 degrees C +/- 0.02 degrees C, P < .05), but both differed from the Datalogger (0.64 degrees C +/- 0.20 degrees C, P < .05). The Datalogger temperature was consistently higher than the mercury thermometer temperature.

Conclusions: The Iso-Thermex electrothermometers were more stable than the Datalogger, and values were within the published uncertainty (+/-0.1 degrees C) when used with PT-6 thermocouples. The Datalogger we used had an uncertainty of measurement greater than that indicated in the user's manual (approximately +/-0.52 degrees C). Uncertainty of +/-0.84 degrees C can significantly influence the interpretation of results when intramuscular temperature changes are usually less than 5 degrees C.

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Figures

Figure 1
Figure 1. Datalogger, Iso-Thermex −20:80, and Iso-Thermex −50: 50 electrothermometers stacked (top to bottom) in center of picture
Computer for Iso-Thermex −20:80 in background; computer for Iso-Thermex −50:50 in foreground right. Foamed polystyrene cooler in foreground left
Figure 2
Figure 2. Mercury thermometer positioned in the cooler
Figure 3
Figure 3. Mean temperatures and standard deviations for each electrothermometer
See this image and copyright information in PMC

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