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obviously more common
and severe on the coldest days.
Signs and Symptoms
of Hypothermia:
-sensation of being cold -intense shivering (later, no shivering)
-fumbling hands, frequent stumbling
-slow, slurred speech
-drowsiness
-slow and shallow breathing
-exhaustion
Severe Hypothermia
may lead to coma and even death. Frost Bite occurs from subfreezing cold.
Frostnip is the superficial injury that people recover from quickly while
frostbite injuries may be permanent. Chilbain (or Trenchfoot) occur when skin
is damaged by a constant wet but above freezing temperature.Both chilblain
and frostbite will cause damage to the skin and underlying tissues. Hypothermia,
Frost Bite and Chilblain, may all coexist. It is much easier to prevent these
conditions than to begin treating them, particularly if you are alone or with
no nearby help. It requires less energy to stay warm and comfortable that
it does to stay warm!
General
Rules for Staying Warm
Blocking Conduction of heat away from the body.
Remember: Thickness = Warmth. This is only true if the insulative layer of
clothing is dry. It is the air spaces in the insulation that prevents the
loss of heat.
Block Convection or the
loss of the layer of warmed air that is always next to your body. An outer
'shell' should be wind-proof and a drawstring at the waist will also prevent
the 'chimney effect', which occurs when warm air escapes from the neck or
head and cool air rushes in at the waist to replace it. A hat also blocks
a significant amount of lost heat.
Stopping Evaporation. Much heat loss occurs through evaporation of sweat.
During winter activities, vented clothing can bring down body temperature
avoiding unnecessary perspiration. A water vapour, Slowing Heat Loss From
Respiration. Exhaled breath contains warm humidified air. Breathing through
a neck warmer, scarf, or air-warming mask, will create a warm vestibule reservoir
so that you rebreath the same humidified air and decrease warm air loss.
Other Hints
Avoid extreme winds that will accelerate convection heat loss, wet clothing,
or water that will drop insulation values down to zero. Wearing multiple layers
of clothing is helpful since you can adjust the thickness of insulation by
adding or subtracting layers of clothing.
Winter clothing can be divided into different types of beneficial clothing
systems:
1) Breathable: consists of 3 levels- a thin, underwear (transport layer),
middle insulative layers, and outer-shell fabric. The outer shell allows protection
against wind but is still breathable.
2) Waterproof/barrier system; is the same as above except the shell
layer is selectively permeable, since water vapour can escape from inside,
but is waterproof from the outer. Gore-tex brand is an example. (Gore-Tex
can fail if water freezes on it becomes a layer of frost)
3) The Vapour-Barrier system consists of 4 layers: The layer next to
the skin is a thin layer of polyester or polypropylene. The next layer is
the vapour barrier used to control perspiration and should be waterproof.
(Usually a coated nylon or polyethylene). This vapour barrier prevents sweating
into the layers of insulation. The following layer is the insulative layer
and lastly the shell is Gore-tex.
This system thereby prevents contamination of the insulative material from
inner and outer moisture. This system reduces insensible perspiration.
Most heat loss occurs from the head so be sure to remember the old mountaineer
saying: "If your feet are cold, put on a hat, and if they are still cold........
put on another hat."
For your reference a downloadable version of this text can be found at these
links.
Front
Page - Back
Page
References:
1) Secrets of Warmth, 2nd edition. Hal Weins, Rocky Mountain Books, *1992,
Calgary, AB
2) Manitoba Lifesaving Society, 2001. 3) Wilderness Medical Society Guidelines
on Hypothermia and Frostbite Injury 2001.
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