Archive for the ‘Paradoxical undressing’ Category

LIGHTNING – THE BEAUTY AND THE BEAST

February 14, 2007

Lightning #2 – The Physics of Lightning

The Physics of Lightning:
Direct current electricity.  ( DC, not AC like the current that feeds our houses.)
Very high voltage and high amperage: can exceed 100 million volts, 100,000 amps.
Very hot, 50,000C, hotter than the surface of the sun.
Very short duration – instantaneous; milliseconds.
Produces Ozone, O3, that protects the earth from the deadly effects of ultraviolet light.
Electricity travels over the surface of objects, unless there is an internal conductor.
Internal conductors – nerves & blood vessels (contain an electrolyte solution).

Formation of lightning:
Vertical acceleration of moist air, forms ice crystals, causes charge separation.
Areas of positively and negatively charged atoms occur throughout the cloud head.
Electrical discharge to stabilize charges created in cumulonimbus clouds.
The base is negatively charged with a positive shadow forming on earth.
Typically, lightning occurs under and along the leading edge of the cumulonimbus cloud.
It can occur as far as 10 miles away, a strike “out of the blue.”
Can travel horizontally over 60 miles; the longest recorded to date was at 118 miles long.

Lightning strike can be: 
Direct strike or streamer current.
Splash or surface arc.    
Step voltage or ground current.
The principle is don’t be a conductor!

For more detailed information about lightning and lightning-related injuries see the Wilderness Medicine Newsletter, Lightning – Beauty & the Beast, July/August 2003.

This blog is powered by the Wilderness Medicine Newsletter, now celebrating 20 years of publication. The WMN is published and distributed online six times each year by TMC Books, and subscriptions cost as little as $10 per year. To find out more, or to subscribe online, click here.

Hypothermia & Paradoxical Undressing

February 7, 2007

Hypothermia & Paradoxical Undressing

Recently in the news, there was a tragic event where a family got caught out in deep snow while driving through the mountains. Eventually, the father decided to leave his family in their car and go for help on foot. Unfortunately, through his valient effort, he didn’t survive that cold, harsh winter environment, and died of hypothermia. 

One of the discussions in the news was that even though he succumbed to the cold and hypothermia, at some point he had taken off some of his clothes. This is a phenomenom associated with hypothermia known as paradoxical undressing.

Pathophysiology:
The supposition as to the cause of paradoxical undressing is that the primary defense against the cold and hypothermia is vasoconstriction of the peripheral circulation. This shunts the blood into the warm core and the skin now becomes a more effective layer of insulation. The problem is that vasoconstriction of the smooth muscles in the vasculature requires glucose and energy consumption. Vasodilation, on the other hand, is a passive process that simply requires the smooth muscles that make up the blood vessels to relax. Over time, the vasoconstricted vessels begin to run out of energy (glucose) because of the poor circulation, and they fatigue and relax, thus vasodilating. This now allows the warm core-blood to re-perfuse the skin, causing a sensation of warmth. This results in the hypothermia victim feeling warm, so, they now begin to shed layers, thus the paradoxical undressing. Between the peripheral vasodilation and the loss of layers of protective clothing, their core temperature now begins to plummet and this hastens death from hypothermia.

I spoke with Dr. Murray Hamlet about parodoxical undressing and hypothermia and his experience and expertise with this phenomenom is the same as ours, in that we do not know of any cases where a hypothermia victim that underwent paradoxical undressing survived.

This blog is powered by the Wilderness Medicine Newsletter, now celebrating 20 years of publication. The WMN is published and distributed online six times each year by TMC Books, and subscriptions cost as little as $10 per year. To find out more, or to subscribe online, click here.