CONTEXT: Cold-water immersion (CWI) is the best treatment for patients with exertional heat stroke (EHS), and rectal temperature (Trec) cooling rates may differ between sexes. Previous authors have suggested that the body surface area (BSA):lean body mass (LBM) ratio is the largest factor affecting CWI Trec cooling rates in men with hyperthermia; this has never been confirmed in women with hyperthermia.
OBJECTIVE: To examine whether the BSA:LBM ratio and other anthropometric characteristics affect Trec cooling rates in women with hyperthermia.
DESIGN: Cross-sectional study.
SETTING: Laboratory.
PATIENTS OR OTHER PARTICIPANTS: Sixteen women were placed in either a low BSA:LBM ratio (LOW; n = 8; age = 22 ± 1 years, height = 166.8 ± 6.0 cm, mass = 64.1 ± 4.5 kg, BSA:LBM ratio = 3.759 ± 0.214 m2/kg·102) or high BSA:LBM ratio (HIGH; n = 8; age = 22 ± 2 years, height = 162.7 ± 8.9 cm, mass = 65.8 ± 12.7 kg, BSA:LBM ratio = 4.161 ± 0.232 m2/kg·102) group.
INTERVENTION(S): On day 1, we measured physical characteristics using dual-energy x-ray absorptiometry, and participants completed a maximal oxygen consumption test. On day 2, participants walked at 4.8 km/h for 3 minutes and then ran at 80% of their predetermined maximal oxygen consumption for 2 minutes in the heat (temperature = ∼40°C, relative humidity = 40%). This sequence was repeated until Trec reached 39.5°C. Then they underwent CWI (temperature = ∼10°C) until Trec was 38°C.
MAIN OUTCOME MEASURE(S): Rectal temperature and CWI cooling rates.
RESULTS: The groups had different BSA:LBM ratios (P = .001), LBM (LOW: 45.8 ± 3.0 kg; HIGH: 41.0 ± 5.1 kg; P = .02), and body fat percentages (LOW: 25.7% ± 5.0%; HIGH: 33.7% ± 6.3%; P = .007) but not different BSA (LOW: 1.72 ± 0.08 m2; HIGH: 1.70 ± 0.16 m2; P = .40) or body mass index (LOW: 23.1 ± 2.1; HIGH: 24.9 ± 4.7; P = .17). Despite differences in several physical characteristics, Trec cooling rates were excellent but comparable (LOW: 0.26°C/min ± 0.09°C/min; HIGH: 0.27°C/min ± 0.07°C/min; P = .39). The BSA:LBM ratio (r = 0.14, P = .59), BSA (r = -0.01, P = .97), body mass index (r = 0.37, P = .16), and body fat percentage (r = 0.29, P = .28), LBM (r = -0.10, P = .70) were not correlated with Trec cooling rates.
CONCLUSIONS: Body anthropometric characteristics did not affect CWI Trec cooling rates in women with hyperthermia. Therefore, clinicians need not worry that anthropometric characteristics might slow CWI treatment in women with severe hyperthermia.
