Page 134 - 2020 JSOM Winter

is designed prevent moisture from rain or melting snow from FIGURE 7 Screen shot of the Cold Weather Ensemble Decision Aid
entering the boot while retaining body heat. It is rated for tem- (CoWEDA).
peratures down to –51°C (–60°F). Because the boot is entirely
sealed between the two rubber layers, an air valve is provided
on the side of the boot to equalize air pressure and prevent the
boot from rupturing at high altitude. There is a wedge on the
back for military ski and snowshoe bindings. 9,107 The Army
is currently working on improvements to this boot, based on
new technologies.

For protection of the hands, the Generation 3 Modular Glove
System consists of 11 different gloves and mitts, shown in Fig-
ure 6C. Four of these are liners meant to be worn under other
gloves/mitts to increase warmth but can be worn on their own.
Two items are Combat Gloves designed to protect against im-
pact and abrasion. Four items are outer layers designed to be
worn over liners and/or gloves for extreme wet and cold con-
ditions. The gloves and mitts have design features that assist
in enhancing grip, aid in the use of mobile devices, and allow
shooting firearms. The Project Manager for Soldier Cloth-
108
ing and Individual Equipment recently issued a request for
proposals for the development of a new modular glove system Source: https://www.researchgate.net/figure/Cold-Weather-Ensemble
-Decision-Aid-CoWEDA_fig1_331993742.
adequate for temperatures 40°F to –60°F. 109
speeds. For example, when wind speeds were <2 mph and in-
There are several methods of determining the amount of cloth- dividuals were walking on a treadmill at 1.7 mph with a 6%
ing insulation necessary to protect against cold injury, 110,111 but incline, finger and nose temperatures were higher than when
the most recent development for military purposes is the com- walking at this speed with no incline. However, when wind
puter software application Cold Weather Ensemble Decision speeds were 11.2 mph, there was only a modest difference in
Aid (CoWEDA). The CoWEDA model is generally based finger temperatures between the two exercise intensities, al-
112
on maintaining skin temperature >5°C (>41°F) because below though nose temperature was higher with more intense exer-
this value, pain, numbness, and reduced tactile sensation are cise. The higher exercise intensity had little effect on cheek or
severe, and the risk of cold-weather injury increases. 93,94,113 forehead temperatures at any wind speed. 116,117
The effects of physical activity are considered in the model
because activity increases body heat and lowers insulation re- CIVD is also affected by exercise and physical training. Physi-
quirements, although activity of sufficient intensity will also cal activity considerably increased the number of CIVD cycles
produce sweat, which can reduce the effectiveness of clothing. and the number of individuals who experienced CIVD. Ex-
118
The model considers the insulation and moisture retention/ ercise training (5 days/wk, 4 weeks, 50%VO max) increased
2
dissipation properties of clothing available in the US military the number of rewarming cycles and the average skin tempera-
inventory. Figure 7 shows a screen shot of the CoWEDA user ture of the fingers when exposed to cold. 119
interface. The user selects the military clothing ensemble, envi-
ronmental conditions, and anticipated physical activity. There Other Prevention Techniques
are preset clothing ensemble selections, but military clothing Army Technical Bulletin Medicine 508 provides additional
11
can also be individually selected for five body regions, includ- recommendations for prevention of frostbite; these are shown
ing the head, upper body, hands, lower body, and feet. The in Table 7.
user can also input the environmental conditions, including air
temperature, humidity, and wind speed. A drop-down menu
has a list of military-related physical activities (i.e., guard Conclusion
duty, walking with load, exercise, lifting and carrying artillery Frostbite is a risk whenever temperatures are <0°C (32°F). Pre-
shells). Outputs (i.e., results) include potential for frostbite in vention is primarily based on an understanding of the clothing
exposed skin, as well as covered feet and hands. The model systems available to prevent cold-related injuries and the fact
has been validated against actual skin temperatures among in- that physical activity can raise body temperature. If frostbite
dividuals exposed to 0°C to –40°C (32°F to –40°F) and found does occur and the patient can be sequestered in a warm envi-
to adequately predict actual skin temperatures during rest and ronment, treatment involves rapid rewarming in a whirlpool
moderate treadmill activity exercise. 112,114 bath (preferred) or rewarming with another human body. Im-
aging techniques to determine the depth of the injury are avail-
Physical Activity able in the field, with more sophisticated techniques available
Physical activity increases the metabolic rate and produces in hospital settings. Prevention of cold-weather injuries is a
heat, which can provide additional protection against frost- command responsibility, with medical planners integrated into
bite. However, warming effects of physical activity differ planning decisions.
depending on the anatomic location and wind conditions.
Compared with no exercise, relatively modest exercise (50% Acknowledgments
VO max) increases skin temperature of the hands, fingers, Thanks to Dr Xiaojiang Xu for assistance with the CoWEDA
2
and nose under low wind speeds. 115–117 However, exercise is model and to Ms Patricia Bremner who obtained many of the
less effective in increasing temperature under higher wind more difficult to obtain references for this article.

132 | JSOM Volume 20, Edition 4 / Winter 2020