Tiede

-20°C AND 200K
BEWARE THE RISK OF COLD INJURIES

Jan van Oosterom wrote about the hardships that he and other Dutch skaters went through during the last year´s Finland Ice Marathon on February 27 in Kuopio Finland (Extreme 200K in Finland; It was on the edge... http://www.rrz.uni-koeln.de/bin2/maillist/skate/1000228.154931/151241).

In Jan's words:

Jan himself was injured, which he only noticed after finishing the cruel 200K:

Worse was it, unfortunately, with Arnold Gaasenberg (team Thyssen)

What were the conditions? At the start of the race early in the morning it was -20 oC. In the course of the run it warmed up but not more than to minus about -11. It was not windy and the sun was shining. For Finns, it was a beautiful, brisk and enjoyable winter weather which they enjoyed as spectators along the course on lake Kallavesi. This seasoning may have contributed to the failure of the organizers to inform the skaters about the hazards of freezing conditions especially when compounded by the wind chill factor due to the speed of 30-40 km per hour of the elite skaters.

To protect especially those skaters who are unitiated to arctic conditions and to make a marathon run on ice in Finland an enjoyable experience for all even at temperatures lower than that experienced at the "extreme 200K" in Kuopio in 2000, we have compiled some material which give instructions in the ways to prevent frostbites and more severe cold injuries. It includes an authoritative article by Dr. Eero Lehmuskallio who has conducted studies on frostbite prevention on Finnish army conscripts. Attached to this article is a wind chill calculator taken from a booklet on cold injuries by Mäkinen et al. (Mäkinen, T., Hassi, J., Tervaskanto-Mäentausta, T., Maunu, M.-L. Rati riti ralla- tuli talvi halla. Suomalaisen kylmäopas. Työterveyslaitos, 1999). We also attach a few addresses of web-sites which provide easy-to-read and practical advice on cold injury prevention.

Veli-Pekka Lehto (lehto@csc.fi)
Irko Aario (luistelu@ouluntarmo.fi)
Pentti Kiiskinen (pentti.kiiskinen@ouka.fi)

Oulun Tarmo

PREVENTION OF COLD INJURIES

by Eero Lehmuskallio, M.D.
Lieutenant Colonel
Finnish Defense Forces

I. Evaluation of risk for cold injury

Ambient temperature

It is possible, but not usual to get frostbite already at temperatures above 0°C. The risk rises slowly when temperature lowers under the freezing point and increases to high risk at -25°C or lower.

Wind-chill effect

The temperature alone does not correlate exactly with the risk of frostbite. Wind or air stream caused by transport or moving without shelter causes an extra loss of skin warmth by convection.
The warm "miniclimate" on the skin surface moves rapidly away from areas of bare or inadequately covered skin. The effect of wind-chill can be calculated and tabulated, as seen in table I.

Contact frostbite

Skin contact with cold items or material, i.e. metal, gasoline etc., may cause an immediate frostbite by conduction at the location of contact (often hands).

II. Grading of frostbite

The severity of frostbite can be assessed only after thawing in warm surroundings and some time (from several hours up to two days) after the injury. In cold there is local blanching of the skin with clear demarcation from unaffected skin. In deep cold injury the skin may turn hard and dark.

- In grade I frostbite the skin is reddish and oedematous.
- In grade II frostbite the skin starts to blister and form bullae.
- In grade III frostbite local necrosis of the dermis develops over 1-2 weeks.

III. Locations with highest risk of cold injury

Epidemiological reports on cold injuries consist mostly of severe cases of deep frostbite. In studies including also everyday mild superficial cold injuries it can be found that the incidence of frostbite in different locations is usually the following (in decreasing order):

1. Toes and feet
2. Fingers and hands
3. Ears (auricles)
4. Nose ~ cheeks > chin
5. Other

IV. Prevention of cold injuries

Behavioural prevention

Avoidance of risk situations, when possible, is naturally the most important preventive action.

Energy supplies, liquid balance and supplement

Muscular activity is responsible for the majority of warmth production in cold. It demands sufficient energy supplies before and during long-lasting cold exposure. Liquid balance is of utmost importance to the peripheral circulation and should be taken care by liquid "tanking" before and during cold exposure, even without the sensation of thirst. Warm drinks are recommended.

Warm clothing

• Clothing should have enough thermal insulative properties. This is best achieved by multi-layer clothing leaving insulative air spaces inside and between the layers.
• The surface of the clothing should protect the body against the cooling effect of wind or air flow (convection).
• Clothing must not be too tight, as it then disturbs the circulation in tissues.
• Clothing must let the humidity caused by perspiration to penetrate outwards without interfering with the insulative properties.
• Feet have to be protected by roomy boots or shoes (iceskates) with enough space for insulative socks or other kind of thermoresistant material.

continues...

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• Hands are best protected with mittens instead of gloves, as mittens allow the fingers warm each other.
• Warm hat with earflaps and possibility to adjust its insulative protection along with the changes in physical activity gives best protection against cold injuries and balances body temperature in heavy physical performance.
• To protect the face and ears, the use of a neckcloth, hood, commando ski-cap, face-mask or even face-guard is recommended. Their choice depends on the estimated risk of cold injury.
• The surface of clothing material, shoes and mittens should be water-resistant inwards not letting the melting snow or rain to get into the material and diminish its insulative capacity.
• Dry spare clothing should be changed on, even in cold environment, if the original clothing gets wet and the cold exposure continues for an extended period.

V. Warnings

• Do not apply "protective" ointments on your face or ears before cold exposition. Their use has been shown to give a false (skin) sensation of (warmth) safety and to be associated with increased risk of facial frostbite, probably mainly by leading to neglect of other necessary preventive measures.
• Do not expose yourself to cold if you are already tired, dehydrated, starving, intoxicated, under influence of sedative drugs or otherwise incapacitated.
• Do not warm frozen extremities by an open fire or with hot material, as they can cause burn injuries to the numb tissues.

VI. First aid and treatment of frostbite

Periphery of extremities

Cold pain and starting numbness of toes or fingers should lead to an increased physical activity, if possible. The enhanced warmth production often helps to restore the safe temperature and circulation of periphery. If it does not help, go into warm surroundings to prevent deeper damages.

If severe symptoms and signs have already developed, do not thaw the frozen extremity if it is probable to freeze again before getting into warm surroundings. When there, 40°C warm bath is the recommended way to thaw frozen feet or hands safely. If there are signs of deep frostbite, seek professional help.

Ears and face

As soon you (or your buddy) notice the beginning signs of frostbite, start warming it up with your hand (palm). Do not rub the injured tissue. Notice the superficial frostbite as a warning of threatening danger. Try to protect the affected location better than originally. If it is not possible, seek your way to warm surroundings to avoid deeper damage to the tissues.

Wind Chill Effect

There are two measures of coldness. One is the temperature we read in the thermometers. The other is the bitterness which is the measure of the actual coldness on the skin as a combination of cold temperature and wind. Windy conditions can increase the bitterness of the cold weather many fold (Wind Chill Effect) with an increased risk of cold injuries. At -17°C and with a wind of 12 m/s, the bitterness of the cold is equivalent to -48°C with no winds. At -22°C and with a wind of 12 m/s, the bitterness of the cold is equivalent to -56°C with no winds.

The bitterness of the cold weather can be calculated by using a calculator (below) when the temperature and the wind velocity are known.

References

Lehmuskallio, E, Rintamäki, H and Anttonen, H. Thermal effects of emollients on facial skin in the cold. Acta Derm Veneorol 80: 203-207, 2000

Lehmuskallio, E. Cold protecting ointments and frostbite. A questionnaire study of 830 conscripts in Finland. Acta Derm Venereol 79: 67-70, 1999

Lehmuskallio, E. and Anttonen H. Thermophysical effects of ointments in cold: an experimental study with a skin model. Acta Derm Venereol 79: 33-36, 1999

Lehmuskallio, E., Lindholm, H., Koskenvuo, K., Sarna, S., Friberg, O. and Viljanen, A. Frostbite of the face and ears: epidemiological studies of risk factors in Finnish conscripts. BMJ 311: 1661-1663, 1995