Several tools exist to reduce rectal temperature (TREC) quickly for patients experiencing exertional heatstroke (EHS). Stationary tubs (TUB) effectively treat EHS but are bulky and impractical in some situations. More portable cold-water immersion (CWI) techniques, like tarp-assisted cooling with oscillation (TACO), are gaining popularity due to their benefits (e.g., less water needed, portability). The Polar Life Pod® (PLP) may be another portable way to reduce TREC, but little research has examined its effectiveness.
We questioned whether the PLP and TUB reduced TREC at “acceptable” or “ideal” rates, whether TREC cooling rates differed by method, and how subjects felt before, during, and after cooling.
Randomized, crossover study
Thirteen individuals (8 men, 5 women; age:21±2y; mass:73.99±11.24kg; height:176.2±11.1cm).
Participants exercised in the heat until TREC was 39.5°C. They immersed themselves in TUB (567.8±7.6L; 15.0±0.1°C) or PLP (202.7±23.8L; 3.2±0.6°C) until TREC was 38°C. Thermal sensation and environmental symptom questionnaire (ESQ) responses were recorded before, during, and after exercise and cooling.
TREC cooling rates, thermal sensation, ESQ responses
Subjects had similar exercise durations (PLP=41.6±6.9min, TUB=42.2±9.3min, t12=0.5, P=0.31), thermal sensation scores (PLP=7.0±0.5, TUB=7.0±0.5, P>0.05), and ESQ scores immediately post-exercise each day (PLP=25±13, TUB=29±14, P>0.05). While TREC cooling rates were excellent in both conditions, PLP cooled faster than TUB (PLP=0.28±0.09°C/min; TUB=0.20±0.09°C/min, t12=2.5, P=0.01). PLP thermal sensation was lower than TUB half-way through cooling (PLP=1±1, TUB=2±1, P<0.05) and post-cooling (PLP=2±1, TUB=3±1, P<0.05). PLP ESQ scores were higher than TUB post-cooling (PLP=25±14, TUB=12±9, P<0.05).
PLP and TUB cooled hyperthermic individuals at “ideal” rates for treating EHS victims (i.e., >0.16°C/min). The PLP may be an effective tool for treating EHS when portability and limited water volumes are concerns. Clinicians should have re-warming tools/strategies (e.g., heating blankets) available to help patients feel better following PLP usage.