Comparison of rectal and aural core body temperature thermometry in hyperthermic, exercising individuals: a meta-analysis

Objective:

To compare mean differences in core body temperature (T_core) as assessed via rectal thermometry (T_re) and aural thermometry (T_au) in hyperthermic exercising individuals.

Data Sources:

PubMed, Ovid MEDLINE, SPORTDiscus, CINAHL, and Cochrane Library in English from the earliest entry points to August 2009 using the search terms aural, core body temperature, core temperature, exercise, rectal, temperature, thermistor, thermometer, thermometry, and tympanic.

Study Selection:

Original research articles that met these criteria were included: (1) concurrent measurement of T_re and T_au in participants during exercise, (2) minimum mean temperature that reached 38°C by at least 1 technique during or after exercise, and (3) report of means, standard deviations, and sample sizes.

Data Extraction:

Nine articles were included, and 3 independent reviewers scored these articles using the Physiotherapy Evidence Database (PEDro) scale (mean  =  5.1 ± 0.4). Data were divided into time periods pre-exercise, during exercise (30 to 180 minutes), and postexercise, as well as T_re ranges <37.99°C, 38.00°C to 38.99°C, and >39.00°C. Means and standard deviations for both measurement techniques were provided at all time intervals reported. Meta-analysis was performed to determine pooled and weighted mean differences between T_re and T_au.

Data Synthesis:

The T_re was conclusively higher than the T_au pre-exercise (mean difference [MD]  =  0.27°C, 95% confidence interval [CI]  =  0.15°C, 0.39°C), during exercise (MD  =  0.96°C, 95% CI  =  0.84°C, 1.08°C), and postexercise (MD  =  0.71°C, 95% CI  =  0.65°C, 0.78°C). As T_re measures increased, the magnitude of difference between the techniques also increased with an MD of 0.59°C (95% CI  =  0.53°C, 0.65°C) when T_re was <38°C; 0.79°C (95% CI  =  0.72°C, 0.86°C) when T_re was between 38.0°C and 38.99°C; and 1.72°C (95% CI  =  1.54°, 1.91°C) when T_re was >39.0°C.

Conclusions:

The T_re was consistently greater than T_au when T_core was measured in hyperthermic individuals before, during, and postexercise. As T_core increased, T_au appeared to underestimate T_core as determined by T_re. Clinicians should be aware of this critical difference in temperature magnitude between these measurement techniques when assessing T_core in hyperthermic individuals during or postexercise.