Record-breaking cold weather has gripped the country this week, including cities unaccustomed to single-digit temperatures. Georgia Tech’s Michael N. Sawka, an adjunct professor in the School of Applied Physiology, offers tips on preventing and treating cold weather injuries.
Humans are not well acclimatized to cold weather, so prevention of cold stress to the body depends primarily on avoiding cold exposure and having adequate insulation (natural and clothing) and caloric intake to support metabolism. Body composition (heavily muscled and subcutaneous fat) is an important physiological determinant of tolerance to cold exposure.
The clothing requirement for warmth and comfort varies if at rest or performing physical activity. Clothing insulation requirements are much higher during rest and light activity than during strenuous activity, so it is important to layer clothing so it can be added or removed as needed.
Cold-induced skin constriction decreases blood flow to peripheral tissues, allowing them to cool and making them susceptible to cold injury. Cooling of peripheral tissues can degrade finger dexterity and impair skeletal muscle contractile function, while reduced core temperature can degrade the ability to achieve maximal metabolic rates and exercise performance.
Preventing cold weather injuries
Hypothermia is low core temperatures (<35°C (95°F)) and is characterized by severe shivering, lethargy, difficulty performing work and mental confusion.
Severe hypothermia is a life-threatening condition that is characterized by unconsciousness, weakening and/or loss of pulse, slow breathing and absence of shivering.
- Select clothing materials that provide good insulation, low water absorbing capacity (no cotton), are waterproof (when appropriate) and breathable.
- Wear clothing in layers and adjust them to environmental conditions and work rate.
- Keep clothing dry and change / dry wet clothes.
- Provide warm / hot beverages and food.
- If in remote areas, such as when hunting, prepare sheltered areas for warming.
Frostbite is characterized by frozen tissues with the most susceptible areas being fingers, toes, ears and nose.
- Be aware of the risk for frostbite (see Wind Chill Temperature Index Chart below)
- Use gloves to handle all metal equipment; never use bare hands (skin touching metals can induce frostbite in seconds).
- Avoid spilling liquids on skin or clothes.
- Do not use face camouflage or petroleum jelly below freezing temperatures
- Keep face and ears covered and dry by wearing hat and face cover.
- Keep socks clean and dry and avoid tight boots.
Non-freezing cold injuries (e.g. Immersion or Trench Foot)
Non-freezing cold injuries are characterized by numb, swollen, tissues that often have had prolonged wet-cold exposures (above freezing).
- Keep feet / hands clean and dry; change wet or damp socks / gloves as soon as possible.
- Dry your boots / liners at least several times per day.
- Use gaiters to keep snow out of boots; gaiters made with semi-permeable membranes will allow sweat can evaporate.
Windchill temperature is shown on the table below. Windchill temperature is based on the combination of air temperature and wind speed. In the table below, coloring indicates the time to frostbite for exposed facial skin. Wind Speed (mph) is on the y-axis. Air temperature (°F) is on the x-axis.
Yellow – Frostbite could occur in 30 minutes
Blue – Frostbite could occur in 10 minutes
Red - Frostbite could occur in 5 minutes
The body’s performance in cold weather
- Manual dexterity is impaired in cold
- Hypothermia impairs mental and physical capacities
- Adjust clothing layers to minimize sweating when working
- Drink sufficient fluids to replace sweat losses to sustain performance
Treatment of cold weather stress
- Remove victim from cold to warm area
- Remove wet clothing, wrap victim in dry blankets or a sleeping bag, and move to warming areas
- Avoid rapid heating and manipulating extremities (not massage or alcohol)
- Provide warm beverages to conscious victims
- Minimize handling or moving so as to not induce cardiac arrest
- Never assume someone is dead until determined by a medical authority, even if a victim is cold and not breathing
- Severe hypothermia is a medical emergency and victims should be evacuated as soon as possible
- Remove victim from cold to warm area
- Slowly warm the frozen areas and do not expose them to any intense heat source
- Do not thaw frozen areas, if re-freezing is likely, or break blisters
- Do not use frozen body areas (e.g., walk on frozen feet)
- Do not massage or rub frozen areas. Do not apply snow or ice to frozen areas
- If severe frost-bite is suspected then evacuate as soon as possible
Non-freezing cold injuries (e.g. Immersion Foot or Trench Foot)
- Remove victim from cold to warm-dry area and remove wet clothing
- Dry and clean tissues gently. Re-warm feet by exposing them to warm air (But do not expose to extreme heat)
- Do not allow victim to stand or walk on injury
- Do not massage, rub, moisten, or use lotions
- Do not break blisters
- Evacuate victim to a hospital
Department of Army, Cold Stress Control and Cold Injury Management. Department of Army Technical Bulletin, TBMED508, Washington D.C. (USARIEM Misc. #04-24), 2005.
NATO Research Task Group HFM-187, RTG. Management of Heat and Cold Stress – Guidance to NATO Medical Personnel, North Atlantic Treaty Organization, RTO-TR-IST-999, 2013.
Winkenwerder, W. and M.N. Sawka. Disorder Due to Heat and Cold. Chapter 109, In: Goldman’s Cecil Medicine 24th edition, L. Goldman and I. Schaffer, eds. Philadelphia: W.B. Saunders Company, 666-670, 2011.
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