Chemically Activated Cooling Vest's Effect on Cooling Rate Following Exercise-Induced Hyperthermia: A Randomized Counter-Balanced Crossover Study

Background and objectives: Exertional heat stroke (EHS) is a potentially lethal, hyperthermic condition that warrants immediate cooling to optimize the patient outcome. The study aimed to examine if a portable cooling vest meets the established cooling criteria (0.15 degrees C.min(-1) or greater) for EHS treatment. It was hypothesized that a cooling vest will not meet the established cooling criteria for EHS treatment. Materials and Methods: Fourteen recreationally active participants (mean +/- SD; male, n = 8; age, 25 +/- 4 years; body mass, 86.7 +/- 10.5 kg; body fat, 16.5 +/- 5.2%; body surface area, 2.06 +/- 0.15 m(2). female, n = 6; 22 +/- 2 years; 61.3 +/- 6.7 kg; 22.8 +/- 4.4%; 1.66 +/- 0.11 m(2)) exercised on a motorized treadmill in a hot climatic chamber (ambient temperature 39.8 +/- 1.9 degrees C, relative humidity 37.4 +/- 6.9%) until they reached rectal temperature (T-RE) >39 degrees C (mean T-RE, 39.59 +/- 0.38 degrees C). Following exercise, participants were cooled using either a cooling vest (VEST) or passive rest (PASS) in the climatic chamber until T-RE reached 38.25 degrees C. Trials were assigned using randomized, counter-balanced crossover design. Results: There was a main effect of cooling modality type on cooling rates (F[1, 24] = 10.46, p < 0.01, eta(2)(p) = 0.30), with a greater cooling rate observed in VEST (0.06 +/- 0.02 degrees C.min(-1)) than PASS (0.04 +/- 0.01 degrees C.min(-1)) (MD = 0.02, 95% CI = [0.01, 0.03]). There were also main effects of sex (F[1, 24] = 5.97, p = 0.02, eta(2)(p) = 0.20) and cooling modality type (F[1, 24] = 4.38, p = 0.047, eta(2)(p) = 0.15) on cooling duration, with a faster cooling time in female (26.9 min) than male participants (42.2 min) (MD = 15.3 min, 95% CI = [2.4, 28.2]) and faster cooling duration in VEST than PASS (MD = 13.1 min, 95% CI = [0.2, 26.0]). An increased body mass was associated with a decreased cooling rate in PASS (r = -0.580, p = 0.03); however, this association was not significant in vest (r = -0.252, p = 0.39). Conclusions: Although VEST exhibited a greater cooling capacity than PASS, VEST was far below an acceptable cooling rate for EHS treatment. VEST should not replace immediate whole-body cold-water immersion when EHS is suspected.