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Old 01-12-2010, 13:21   #16
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or even a four-stage model

The Cold Water boot camp folks have a four-stage model of what happens when people fall in cold water. Roughly, it goes something like

1. first minute or so... cold water immersion shock, gasp reflex -- likelihood of breathing or swallowing water, rapid shallow breathing, chance of heart attack, panic....
2. next ten minutes or so depending on water and swimmer... swim failure; failure first of fine muscle control (inability to handle buckles, zippers, etc.), then failure of control of big muscles; with swim failure the body becomes more vertical and drowning is nigh....
3. hypothermia... various degrees of severity with progression from shivering to unconsciousness.
4. post-hypothermia shock and collapse... frequent response after a victim has been pulled out of the water.

A big caveat for the rules of thumb and timelines (such as 50-50-50; 50% chance of surviving hypothermia for 50 minutes in 50 degree F water, provided the victim doesn't drown first) is that people vary hugely in their response to cold water immersion and their survival. About the one time when it's good to have plenty of body fat is when you're in cold water.
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Old 20-12-2010, 13:52   #17
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body fat hasnt anything to do with preventing hypothermia. sorry. is just many more miles of blood vessels that take away body heat by trading the warmth of your blood for the chill of the cold water. hypothermia gets ye BEFORE drowning does. to drown, you must INHALE water, which is not a normal body action. UNLESS THERE IS NO ACTIVITY DUE TO EXTREMELY COLD BODY TEMP. then ye will voluntarily breathe water. time line be damned-- takes less than 15 min for hypothermia in pacific ocean in our allegedly temperate zone, wherein the sea is only 50 something degrees.
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Old 21-12-2010, 16:45   #18
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body fat hasnt anything to do with preventing hypothermia. sorry. is just many more miles of blood vessels that take away body heat by trading the warmth of your blood for the chill of the cold water. hypothermia gets ye BEFORE drowning does. to drown, you must INHALE water, which is not a normal body action. UNLESS THERE IS NO ACTIVITY DUE TO EXTREMELY COLD BODY TEMP. then ye will voluntarily breathe water. time line be damned-- takes less than 15 min for hypothermia in pacific ocean in our allegedly temperate zone, wherein the sea is only 50 something degrees.
Sorry Z, but you are flat wrong. This isn't really a matter of debate anymore, it is a well established medical fact. Unfortunately there is still a lot of misinformation and misunderstanding about the subject. In an earlier post on this thread I suggested some good sources on the subject. I suggest you check them out. One link I forgot to add is the State of Alaska Emergency Medical Servicis "Cold Injury Guidelines" at http://www.chems.alaska.gov/EMS/docu...oldInj2005.pdf These were developed in part by Dr. Giesbrecht and have been widely adopted outside Alaska.

In a nutshell, what happens in cold water imersion is this:

The first phase is cold water shock, which can last from a few seconds to a few minutes. This is characturized by rapid gasping and hyperventilation. Quite often people will inhale water at this time. If not wearing a pfd, they will often drown immediately from inhaling water. But body core tempearature has not dropped at all in this phase.

The second phase is cold incapacitation, which can last from 5 to 15 minutes, depending on water temperature. The arms and legs chill quickly, due to larger surface to volume ration. Also, the bodies response to cold is to shut down circulation to the limbs and skin ("vasoconstriction") in order to reduce heat loss. The result of this is that you gradually lose use of your limbs. Fingers and hands go first, then arms and legs. This leads to swim failure. If not wearing a pfd, you will drown at this point. However, body core temperature has not dropped significantly, and you are no where near close to dying from hypothermia.

The third phase is hypothermia. Even in ice water, it takes at least a half hour (usually an hour or more) for your body core temperature to drop to the point of losing consciesness. In the water, you will not get this far without a pfd, instead you will have drowned in the first or second phase. Death from hypothermia doesn't occur until core temperature has dropped to below 82 F (28 C), often when your heart goes into ventricular fibrolation.

Also, body fat does make a difference. This has been demonstrated in experiments with volunteers. Check out the graph at 1/10/1 Fat does insulate. That's why marine mammals in cold areas like seals and walruses have think layers of fat.

As I noted above, this isn't really a matter of debate. In cold water without a pfd you will drown before hypothermia. What I have outlined above is established medical fact. Check out the "Cold Water Boot Camp" videos for graphic demontrations on volunteers.
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