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Les stages de l’hypothermie

Science | Jean-Daniel Bourgault | Affiché 1171 fois | Publié le mercredi 23 janvier 2013 à 04:06


NB : Le texte suivant provient d’un livre américain. Les mesures de températures y sont donc exprimées en anciens degrés Farenheit. Nous avons ajouté les Celsius pour des fins de lisibilité.

[…]

Never mistake frostbite for hypothermia. Frostbite freezes extremities, while hypothermia cools the body's interior. Humans function best at a core temperature of just under ninety-nine degrees (37,2°C). At windchills of minus forty degrees (-40°C), with serviceable clothing, it is reasonable to expect the core temperature to drop at something like one degree every thirty minutes.

When the core drops to ninety-five (35°C), significant symptoms appear. People shiver uncontrollably. They become argumentative. They feel detached from their surroundings. As their minds slow, they become what winter travelers sometimes refer to as "cold stupid." They become sleepy.

A thirteen-year-old boy who survived the School Children's Blizzard later recounted his experience. "I felt sleepy," he said. "I thought if I could only lie down just for a few minutes I would be all right. But I had heard the farmers telling stories about lying down and never getting up again in snow storms. So I kept on, but I finally got to the point where I could hardly lift my feet any more. I knew that I couldn't stand it but a minute or two longer."

At a core temperature of about ninety-three degrees (34°C), amnesia complicates things. Do we turn right or left? Did I put that glove in my pocket? Have I been here before?

At ninety-one degrees (33°C), apathy settles in. Muscles by now are stiff and nonresponsive. If one continues moving at ail, one begins to stagger.

When the core temperature reaches ninety degrees (32°C), the bodys ability to fight the cold diminishes, and the core temperature tumbles downward. The heart itself becomes sluggish. Blood thickens. Lactic and pyruvic acids build up in tissues, further slowing the heartbeat.

It is possible to survive core temperatures as low as eighty-seven degrees (31°C), but only with rescue and rewarming. At this temperature, self-rescue is almost impossible. Hallucinations are common. The mind imagines warm food and dry sleeping bags. The ears might hear music. A survivor might report looking down from above on his own struggling body, or he might remember strolling away from his own prone carcass in the snow. Victims at this point have crossed the line between cold stupid and what is sometimes called "cold crazy."

Just shy of death, victims may experience a burning sensation in the skin. This may be a delusion, or it may be caused by a sudden surge of blood from the core reaching the colder extremities. The last act of many victims is the removal of their clothes - the ripping away of collars, the disposal of hats. Doctors sometimes cali this "paradoxical undressing."

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Source : Streever B (2009) Cold : adventures in the world's frozen places. New York, Little, Brown and Co. pp. 25-26 [Disponible à la bibliothèque du 490 : G608 S69 2009 et partiellement sur GoogleBooks]

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