title: Validity of Core Temperature Measurements at 3 Rectal Depths During Rest, Exercise, Cold-Water Immersion, and Recovery.
abstract: BACKGROUND
  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.
  
  
  OBJECTIVE
  To determine whether rectal temperature (Trec) 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 [Teso]) during similar stressors an athlete with EHS may experience.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  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 m2).
  
  
  METHODS
  Rectal temperatures taken at 4 cm, 10 cm, and 15 cm from the anal sphincter were compared with Tesoduring a 10-minute rest period; exercise until the participant's Tesoreached 39.5°C; cold-water immersion (∼10°C) until all temperatures were ≤38°C; and a 30-minute postimmersion recovery period. The Tesoand Trecwere 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.
  
  
  METHODS
  The Tesoand Trecwere used to calculate bias (ie, the difference in temperatures between sites).
  
  
  RESULTS
  Rectal depth affected bias (F2,24= 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 (F2,34= 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).
  
  
  CONCLUSIONS
  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 Trecis valid for diagnosing hyperthermia. Rectal temperature is a better indicator of pelvic organ temperature during cold-water immersion than is Teso.
authors.affiliation: Central Michigan University, Mount Pleasant.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Miller
authors.affiliation: Central Michigan University, Mount Pleasant.
authors.forename: Lexie E
authors.initials: LE
authors.lastname: Hughes
authors.affiliation: Central Michigan University, Mount Pleasant.
authors.forename: Blaine C
authors.initials: BC
authors.lastname: Long
authors.affiliation: University of Connecticut, Storrs.
authors.forename: William M
authors.initials: WM
authors.lastname: Adams
authors.affiliation: University of Connecticut, Storrs.
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Casa
mesh_terms: D001831:Body Temperature / Q000502:physiology*; D003080:Cold Temperature; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D005334:Fever / Q000175:diagnosis / Q000503:physiopathology; D018883:Heat Stroke / Q000175:diagnosis / Q000503:physiopathology; D006358:Hot Temperature; D006801:Humans; D007101:Immersion / Q000503:physiopathology*; D008297:Male; D012007:Rectum / Q000502:physiology; D012146:Rest; D014867:Water; D055815:Young Adult
chemical_list: D014867:Water
keywords: esophagus; exertional heat stroke; hyperthermia