Partial Immersion Using Body Bags for Exertional Hyperthermia: A Randomized Crossover Study

Recent recommendations suggest emergency medical personnel should consider rapid whole-body cooling for heat stroke patients. Cold-water immersion maximizes cooling rate and subsequent outcomes following heat stroke. Body bags filled with ice and water may provide portable, accessible partial cold-water immersion for this setting. The purpose of this study was to determine whole-body cooling rates when using body bags to facilitate partial cold-water immersion to treat exertional hyperthermia.

A total of 9 healthy participants (8 male; mean [SD] age, 24 [4] years; height, 175 [7] cm; body mass, 83.6 [21.6] kg) completed our randomized-crossover field study. Following hydration verification, participants completed a self-paced 400 warm-up run, 1,609 m run, and 10-m sprints until rectal temperature (T-_rec) reached 39.2 °C or volitional exhaustion. Following exercise, participants were cooled for a maximum of 30 minutes lying supine in the shade (control; CON) or in body bags filled with 20 gallons of ice water (5.2 [1.6] °C). Following cooling, participants sat upright for a 15-minute recovery. T-_rec and heart rate (HR) were taken throughout exercise, every minute of cooling, and every 5 minutes of recovery. Participants completed both trials separated by 1 week in random order.

Wet bulb globe temperature between trials was not significantly different (grand mean, 28.43 [1.03] °C; P = .73). There was no difference in participant maximum T-_rec (body bag, 38.98 [.23] °C; CON, 38.93 [.39] °C; P = .45); HR (body bag, 183 [14] beats per minute [bpm]; CON, 189 [13] bpm; P = .21); rating of perceived exertion (P >.99); thirst (P = .62); or thermal sensation (P = .73) during exercise. Fluid consumed (P = .40), body mass change (P = .90), 400 m run times (P = .19) and 1,609 m run times (P = .17) were no different between trials. Whole-body cooling rate for body bag was .102 (.04) °C/min, whereas CON produced a cooling rate of .040 (.04) °C/min (95% CI, .030-.095; P = .002). Total cooling time was significantly faster (13.2 (5.8) min) with BB compared to CON (27.6 (4.2) min; 95% CI, 9.2-19.5; P = .002).

In clinical settings where full-body cold-water immersion is not feasible, or during emergency transport, partial immersion via body bags offers acceptable cooling rates for hyperthermic patients. Emergency medical personnel could apply these data for support in updating heat stroke protocols to include partial immersion via body bag during transport, or immediately upon emergency department arrival.