Hypothermia is a significant medical risk of mass participation long-distance open water swimming.

OBJECTIVE: To document the prevalence of hypothermia in a mass participation endurance open water swimming event and to determine demographic and individual factors that may predict failure to finish the race and hypothermia. METHODS: A prospective observational study in competitors in a 19.2-km open water swimming race in Perth, Western Australia. Pre-race information collected included age, sex, training and race experience, medical history, and body mass index (BMI). Body temperatures at 5 minutes postrace were measured using an equilibrated oral- or rectal-reading low-range glass mercury thermometer. Logistic regression was used to develop models predicting hypothermia (defined as a temperature of <35 degrees C) and failure to finish the race. RESULTS: One hundred and nine competitors (70 male, 39 female) with a combined mean age of 38.4 +/- 12.1 years were studied. Hypothermia was the most common race-related illness, identified in 26 of 35 swimmers screened as requiring temperature measurement, including 5 who required short-stay hospital care and 2 who required critical care transfer. Longer race duration (odds ratio [OR] 1.77, 95% CI 1.10-2.84, P = .018) was associated with an increased risk of hypothermia, and higher BMI (OR 0.57, 95% CI 0.41-0.79, P = .001) was associated with a decreased risk of hypothermia. Weak predictors of failure to finish were age (OR 1.06, 95% CI 1.01-1.11, P = .012) and hours spent training (OR 1.08, 95% CI 1.01-1.16, P = .025). CONCLUSIONS: Hypothermia is a common condition affecting mass participation long-distance open water swimmers. Increased BMI appears to be protective against hypothermia, while prolonged duration of the swim predicts an increased risk of hypothermia. The weak predictors of failing to finish are of questionable clinical significance.

Tympanic thermometry is unsuitable as a screening tool for hypothermia after open water swimming.

OBJECTIVE: Mass participation in competitive open water swimming is becoming increasingly popular. The purpose of this study was to determine whether infrared emission detection (IRED) tympanic temperature measurement taken in participants approximately 1 minute following a long-distance open water swimming event is a suitable screening tool for hypothermia. METHODS: We studied 15 males and 7 females who completed the 20-km Rottnest Channel Swim off the coast of Perth, Western Australia. Following the swim, each athlete was clinically assessed for hypothermia through the observation of gait, cognitive processing, and demeanor. Approximately 1 minute following the swim, participants underwent temperature measurement using one of two IVAC Core Check 2090 IRED tympanic thermometers set to core equivalent mode. Further tympanic readings and an oral temperature reading were taken at 5 minutes post swim in subjects triaged to the medical tent after the initial clinical screen. RESULTS: At 1 minute post event, the average tympanic temperature measurement was 28.9 degrees C (95% CI, 28.3-29.7), while at 5 minutes postevent it was 31.6 degrees C (95% CI, 31.1-32.2). The average oral temperature at 5 minutes post event was 34.3 degrees C (95% CI, 33.7-34.7). The difference between the screening tympanic and oral temperatures was statistically significant (P = 0.000). CONCLUSIONS: Infrared emission detection tympanic thermometry is unsuitable as a screening tool for hypothermia following a prolonged open water swim because it substantially overestimates the incidence and severity of hypothermia in participants.