ReviewExtremity cooling for heat stress mitigation in military and occupational settings
Introduction
Numerous commercial and industrial occupational settings, as well as military operational and training exercises, expose individuals to considerable heat stress due to high environmental heat and/or a high rate of metabolic heat production (Carter et al., 2005, Centers for Disease Control and Prevention, 2008). As a result body heat storage and associated cardiovascular strain limit exercise performance and increase the risk of exertional heat illness (EHI) (Carter et al., 2005, Sawka et al., 2012). In a number of occupational and military settings it may be biophysically difficult to dissipate body heat due to very hot ambient conditions and/or wearing needed protective clothing or equipment. Clothing/equipment limiting heat loss is common in numerous military, firefighting, hazmat incident, law enforcement, and sporting endeavors (e.g., American Football) (Cheuvront et al., 2003). When physiological cooling is insufficient, active cooling countermeasures may be capable of extending work performance time and reducing EHI incidence and severity (O’Hara et al., 2008).
The purpose of this paper is to review literature on extremity cooling and present a prototype Arm Immersion Cooling Systems (AICS) which we have developed and successfully implemented at military training sites. We will also present information demonstrating that extremity immersion cooling is highly effective and well received by users.
Section snippets
Exertional heat injury epidemiology
In the active duty military, there are typically over 300 cases of exertional heat stroke and over 2000 cases of other reportable heat illness hospitalizations in the training environment per year (Army Medical Surveillance Activity, 2012). In the civilian sector the incidence of EHI is more difficult to determine, as the diagnosis of heat stroke is not required to be reported in any US state (Howe and Boden, 2007). It has been reported, however, that exertional heat stroke is the third leading
Extremity immersion in cold water
Extremity immersion can be an effective method for reducing core temperature and extending work for the following reasons: the heat transfer coefficient of water is approximately 25 times greater than air; the extremities have relatively large surface area to mass ratios compared to the torso; and blood flow through the cutaneous vasculature is very high when core temperature is elevated.. As a result of these characteristics, a number of investigators have examined the use of extremity
Arm immersion cooling system
Over the past several years, in an attempt to take advantage of the well-documented efficacy of extremity immersion for reducing core temperature, the US Army Research Institute of Environmental Medicine and the Natick Solider Research, Development and Engineering Command have been jointly developing an Arm Immersion Cooling System (AICS) for use by Soldiers in the training environment (Fig. 2). The goal was to develop a solution that was suitable for use by multiple soldiers at once, that was
Summary
From research studies (Giesbrecht et al., 2007, House, 1998, House et al., 1997, Selkirk et al., 2004) it can be concluded that (1) hand or hand and forearm immersion in cool water is preferable to foot immersion due to greater rate of cooling and/or convenience factors regarding removing footwear; (2) 10 °C and 20 °C water provides greater cooling power than 30 °C water; (3) 20 °C water is still effective and allowing colder water to warm to 20 °C through repeated use may reduce logistical demands;
Disclaimer
This study is approved for public release, distribution is unlimited. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the U.S. Army or the Department of Defense. Any citations of commercial organizations and trade names in this report do not constitute an official U.S. Department of the Army endorsement of approval of the products or services of these organizations.
References (33)
- et al.
Comfort and thermal sensations and associated physiological responses at various ambient temperatures
Environ. Res.
(1967) - et al.
The effect of hand immersion on body temperature when wearing impermeable clothing
J. Roy. Nav. Med. Serv.
(1991) - et al.
Palm cooling does not reduce heat strain during exercise in a hot, dry environment
Appl. Physiol. Nutr. Metab.
(2010) - et al.
American College of Sports Medicine position stand. Exertional heat illness during training and competition
Med. Sci. Sports Exercise
(2007) - Army Medical Surveillance Activity, 2012. Update: heat injuries, active component, U.S. Armed Forces, 2011. Medical...
- et al.
A practical cooling strategy for reducing the physiological strain associated with firefighting activity in the heat
Ergonomics
(2009) - et al.
The impact of different cooling modalities on the physiological responses in firefighters during strenuous work performed in high environmental temperatures
Eur. J. Appl. Physiol.
(2011) - et al.
National Athletic Trainers’ Association position statement: exertional heat illnesses
J. Athl. Train.
(2002) - et al.
Epidemiology of hospitalizations and deaths from heat illness in soldiers
Med. Sci. Sports Exercise
(2005) - Centers for Disease Control and Prevention, 2008. Heat-related deaths among crop workers- United States, 1992–2006....
Efficacy of intermittent, regional microclimate cooling
J. Appl. Physiol.
Impaired defense of core temperature in aged humans during mild cold stress
AJP – Regul. Integrative Comp. Physiol.
Cooling hyperthermic firefighters by immersing forearms and hands in 10 degrees C and 20 degrees C water
Aviat. Space Environ. Med.
Heat extraction through the palm of one hand improves aerobic exercise endurance in a hot environment
J. Appl. Physiol.
Heat loss through the glabrous skin surfaces of heavily insulated, heat-stressed individuals
J. Biomech. Eng.
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2022, Science and SportsCitation Excerpt :When physiological cooling by sweating is insufficient, active cooling countermeasures may extend work performance time and reducing occurrence of exertional heatstroke by the method of recovering in a shady area, removing clothing and applying cool water to the skin [11,12]. Extremity immersion can be an effective method for reducing core temperature and extending work for the following reasons; the heat transfer coefficient of water is approximately 25 times greater than air; the extremities have relatively large surface area to mass ratios compared to the torso; and blood flow through the cutaneous vasculature is very high when core temperature is elevated [13]. Military personnel may not have a place under the shade to recover, and to bring a large, rapid speed fan requires electrical current.
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Present Address: US Army Public Health Command, 5158 Blackhawk Rd, Aberdeen, MD 21010, United States.