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Cold Stress: 
when is it dangerous to be cold?

A cold environment is defined as an environment under which greater than normal heat losses are anticipated and compensatory thermoregulatory actions are required. That is, we have to pay attention to the heat escaping our bodies and do something about it.

Before a cold exposure

People in general good health who are physically fit face winter with the least danger of non-freezing (blood vessel damage) and freezing cold injury (frostbite) and hypothermia (a decrease in body temperature).

The very young, the elderly, those with cardiovascular or circulatory difficulties or who are emotionally, physically or drug or alcohol impaired, or who are inactive are in the greatest danger when the weather becomes cold.

You are best prepared if you know how to select clothing based on your activities and the predicted air temperature and winds speed. You should also know how to recognize the early warning signs and symptoms of cold injury and hypothermia in yourself and others and what to do about them.

During a cold exposure

Clothing choices and control of exposure is important, especially if there is a wind.

Clothing should be loosely fitting, dry and clean with snug, but not constricting, cuffs and sleeves. Use clothing that can be easily changed or adjusted to match changes in exposure conditions and exercise levels. This is why you should wear several layers of clothing rather than one heavy garment.

If there is a wind a top layer of tightly woven, snugly fitting, windproof clothing will help keep you warm.

Get used to removing or adjusting clothing to keep you comfortable and to provide ventilation so water vapor from sweat can escape. Periods of changing activity exercise then rest require frequent adjustments.

Check every ten minutes or so to be sure there is no loss of feeling in toes, feet, fingers, hands, ears or nose, especially if you have been sitting or resting.

Frequently check children, the elderly the infirm or incapacitated to be sure they are alert. Grogginess can be a sign of hypothermia. Check to see that their extremities are warm. Cold or stiff fingers and toes may be showing early signs of cold injury or frostbite.

Even if you dont think its a particularly cold day, believe anyone who tells you they feel sleepy or chilled. Take immediate action to get them to a warm shelter. Hypothermia can occur even when the air temperature is 65F, especially if clothing is damp and theres a wind.

Routinely carry extra clothing, boots, gloves, blankets, emergency lighting and food in your car during winter months. Just a flat tire, leaky radiator hose or other minor problem can soon become a dangerous situation for yourself or your passengers on a windy, cold, and wintery day.

Do not massage or apply heat to any extremity which becomes cold, hard or looks waxy. Loosen clothing around it, protect it with warm, clean and insulating clothing, and seek medical help immediately. Do not delay!

After a cold exposure

Once you are out of the cold, remove boots, socks, gloves and other clothing and put them where they can get warm and dry.

Check your own fingers and toes, as well as those of children, the elderly and infirm, to be sure they are dry and can re-warm.

Avoid any re-exposure to the cold until you and others in your care are fully re-warmed and clothing is dry and warm.

Emergency measures

If fingers or hands become either painfully cold, or have lost sensation, bring them inside your clothing against warm, bare skin. If toes or feet become numb or cold, get to a shelter, loosen or remove boots and socks and allow full re-warming, drying and recovery before re-entering the cold.

If you suspect there is frostbite of toes or feet, do not massage or walk on them. If its the fingers and hands, do not rub or use them. Keep cold damaged extremities immobile, protect them with warm, dry clothing and seek medical help immediately. Do not attempt self-treatment.

Cold exposed people who are sleepy, lethargic, slow to respond, or who begin behaving strangely may be hypothermic. Profoundly hypothermic people will appear to be dead, even to experienced medical and paramedical professionals. Do not attempt to treat them yourself. Take no chances, demand emergency medical help.

Health effects

Inhalation of very cold air cools the mucous membranes of the upper respiratory tract and may eventually cause irritation, micro-inflammatory reactions and produce broncho-spasm.

Cold may increase blood pressure, acute or chronically. Persons with circulatory diseases are more susceptible and prone to suffer from cold exposures.

Many drugs act on the cardio-respiratory system so their effect may interfere with the bodys response to cold.

Local tissue damage ("white finger") may be triggered by exposure to cold after prolonged exposures to vibration from hand held power tools.

An affected person may not fully realize the danger of the situation because the progressive cooling of the body can cause mental confusion and impaired judgement.

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