Validity of Core Temperature Measurements at 3 Rectal Depths During Rest, Exercise, Cold-Water Immersion, and Recovery

• Published in: Journal of athletic training Vol. 52; no. 4; pp. 332 - 338
• Main Authors: Miller, Kevin C, Hughes, Lexie E, Long, Blaine C, Adams, William M, Casa, Douglas J
• Format: Journal Article
• Language: English
• Published: United States National Athletic Trainers Association 01-04-2017
• Subjects: Anatomy; Athletic Coaches; Bias; Body Temperature - physiology; Climate; Cold Temperature; Cross-Sectional Studies; Esophagus; Exercise; Exercise - physiology; Female; Fever - diagnosis; Fever - physiopathology; Heat; Heat Stroke - diagnosis; Heat Stroke - physiopathology; Heatstroke; Hot Temperature; Humans; Immersion - physiopathology; Male; Original Research; Outcome Measures; Physical Activities; Physical fitness; Pregnancy; Pulmonary arteries; Rectum - physiology; Rest; Scientific Concepts; Studies; Temperature; Urine; Validity; Veins & arteries; Water; Young Adult; exertional heat stroke; esophagus; hyperthermia
• ISSN: 1062-6050; 1938-162X
• DOI: 10.4085/1062-6050-52.2.10

No evidence-based recommendation exists regarding how far clinicians should insert a rectal thermistor to obtain the most valid estimate of core temperature. Knowing the validity of temperatures at different rectal depths has implications for exertional heat-stroke (EHS) management.
  To determine whether rectal temperature (T
) taken at 4 cm, 10 cm, or 15 cm from the anal sphincter provides the most valid estimate of core temperature (as determined by esophageal temperature [T
]) during similar stressors an athlete with EHS may experience.
  Cross-sectional study.
  Laboratory.
  Seventeen individuals (14 men, 3 women: age = 23 ± 2 years, mass = 79.7 ± 12.4 kg, height = 177.8 ± 9.8 cm, body fat = 9.4% ± 4.1%, body surface area = 1.97 ± 0.19 m
).
  Rectal temperatures taken at 4 cm, 10 cm, and 15 cm from the anal sphincter were compared with T
during a 10-minute rest period; exercise until the participant's T
reached 39.5°C; cold-water immersion (∼10°C) until all temperatures were ≤38°C; and a 30-minute postimmersion recovery period. The T
and T
were compared every minute during rest and recovery. Because exercise and cooling times varied, we compared temperatures at 10% intervals of total exercise and cooling durations for these periods.
  The T
and T
were used to calculate bias (ie, the difference in temperatures between sites).
  Rectal depth affected bias (F
= 6.8, P = .008). Bias at 4 cm (0.85°C ± 0.78°C) was higher than at 15 cm (0.65°C ± 0.68°C, P < .05) but not higher than at 10 cm (0.75°C ± 0.76°C, P > .05). Bias varied over time (F
= 79.5, P < .001). Bias during rest (0.42°C ± 0.27°C), exercise (0.23°C ± 0.53°C), and recovery (0.65°C ± 0.35°C) was less than during cooling (1.72°C ± 0.65°C, P < .05). Bias during exercise was less than during postimmersion recovery (0.65°C ± 0.35°C, P < .05).
  When EHS is suspected, clinicians should insert the flexible rectal thermistor to 15 cm (6 in) because it is the most valid depth. The low level of bias during exercise suggests T
is valid for diagnosing hyperthermia. Rectal temperature is a better indicator of pelvic organ temperature during cold-water immersion than is T
.