Effect of a personal ambient ventilation system on physiological strain during heat stress wearing a ballistic vest

Abstract

The present study was conducted in order to evaluate whether physiological strain is alleviated by a new personal cooling system (CS) consisting of a layered vest and integrated blower that generate a flow of air. Twelve male volunteers were exposed to climatic conditions of 40 degrees C, 40%RH (40/40), and 35 degrees C, 60%RH (35/60) during a 115 min exercise routine, followed by 70 min resting recovery, while wearing a battle dress uniform (BDU) and a ballistic vest, with (COOL) or without (NOCOOL) CS. The CS was able to attenuate the physiological strain levels during exercise, when compared to identical exposures without the CS. Temperature elevation, (DeltaT (re)) after 100 min of exercise, was lower by 0.26 +/- 0.20 and 0.34 +/- 0.21 degrees C in 40/40 and 35/60, respectively, (p < 0.05). Mean skin temperature (T(sk)) was lower by 0.9 +/- 0.4 and 0.6 +/- 0.5 degrees C for 40/40 and 35/60, respectively. Heart rate (HR) was not significantly different for COOL versus NOCOOL for 40/40. At 35/60, HR was lower by 10 beats per min (bpm) (p < 0.05). Physiological strain index (PSI) was 9 and 21% lower for the 40/40 and 35/60, respectively, for COOL versus NOCOOL (p < 0.05). Heat storage (S) rates were 19 and 24% lower and sweat rates were 21 and 25% lower for the 40/40 and 35/60, respectively, for COOL versus NOCOOL (p < 0.05). However, the CS was not effective in alleviating physiological strain during resting recovery with no difference in T (re) cooling rate, S, or HR drop rate between groups over resting recovery periods. The CS tested in this study was found to be an effective tool for lowering physiological strain while exercising but not during resting recovery. Therefore, the CS should be further developed in order to achieve greater attenuation of the thermal strain during exercise and improve effectiveness during rest. Overall, it has the potential to be useful for both military and sports personnel.

Towards Optimizing a Personal Cooling Garment for Hot and Humid Deep Mining Conditions

“…The ACG's primary mode of cooling is by evaporating the body's sweat. However, the efficiency of air-cooled garments in environments with high humidity levels is severely limited [7].…”

“…The space between the body and the inner layer of the garment affects heat transfer. It is recommended that a gap be maintained between the vest and the skin to maximize the evaporation of sweat [7].…”

Effects of Air Velocity, Air Gap Thickness and Configuration on Heat Transfer of a Wearable Convective Cooling System

“…It was indicated that the convective and evaporative heat transfer were significantly improved. However, the average convective and evaporative heat transfer coefficients in their study were around 13 [19]. Consequently, our cooling system showed the advantages of similar cooling capability but at a smaller size, making the system potentially more wearable for every-day wear.…”

“…Published research [10][11][12][13][14][15][16][17][18] on air ventilation systems has primarily focused on reducing thermal stress in warm environments (35°C-40°C) where evaporative cooling from sweat is still realistic. Depending on the blower units used, the ventilation system may be fairly heavy (1 kg-4 kg), limiting the wearability of such systems in office environments.…”

Effectiveness of Exercise-Heat Acclimation for Preventing Heat Illness in the Workplace

“…Thus, if workers wear protective clothing with limited vapor permeability, the benefits of short-term heat acclimation or short-term exercise training are relatively small, and it is necessary for such individuals to lower their work rate and take as many breaks as possible. During rest and physical work, cooling of the inner sites of protective clothing by fanning and an ice vest and cooling of the limbs have been found be effective for heat strain relief [57][58][59][60]. Finally, workers and the general public should be educated about the psychophysiological mechanisms of heat illness and specific countermeasures, including cooling the body [61][62][63][64][65], f luid intake [66][67][68][69], and heat acclimation.…”