Hypothermia

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Dea

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Ok, all I got from diver training is-- if you are so cold you are shaking uncontrollably-- get out.
Seems sufficient enough for practical purposes, but I'd like to understand a little about the mechanisms of hypothermia.

For diving as well as other sports. Say you have prolonged exposure, but you don't die, don't get frostbite and get to warmth. What effects does it have on your organs, in what order... Why does the temperature rize so sharply? and how to get over it in a quickest possible way?
 
Hi Dea,

Scubadoc has an excellent article about hypothermia and near drowning at

Hyopthermia and near drowning

Hypothermia is a killer because it causes cardiac arrythmias (cardiac arrest) at core temperatures of less than 32 degrees C. Frostbite is something entirely different. Most of the victims of the Titanic disaster died from hypothermia not drowning.

Oddly, you shivver when you are experiencing cold but do not shivver when you are hypothermic. The main danger is the victim of hypothermia (alone) can feel quite euphoric and may be quite unaware of the danger he is in; - ill equipped and inexperienced fell walkers are at greatest risk because of the wind-chill factor.

I have been very cold on some dives but do not remember shivvering underwater, probably because it is so easy to ignore if you are enjoying yourself!

Prevention is better than any treatment. If you are going to dive in cold water a dry suit and good undersuit are essential. However, you can become hypothermic diving in the tropics. First Aid treatment consists of preventing further head loss using warm, dry clothing, and rewarming with hot drinks.

Perhaps a look at the section under environmental suits on this site might help?
 
Your link didn't work so I copied and pasted it again now it seems to work.

Larry Stein:)
 
Laurence Stein DDS once bubbled...
Your link didn't work so I copied and pasted it

Larry Stein:)
This Regulator business has clearly gone to your head!:D :D
 
Ok, that link works for me now. I just wanted everyone to be able to access the wisdom of our own Scubadoc.:)

BTW, this is the ONLY edit I have ever done on any thread except for my own stupid mistakes.

I'm trying not to let superpowers go to my head.

Larry Stein
 
Concerning hypothermia, in what way can effect
the diver and what can it do to him while diving,
what I am trying to say that if I am very cold in the
water of course I have to adored the dive but if I am
doing some deco stop what could happen to my buddy
concerning off gassing if I was very cold. Or could it affect
something else

Sorry about my English and I hope guys when u want to explain something ( take it easy ) don’t complicate my life with your explanation just small nice understanding answer. Thanks again
 
wazza once bubbled...
Concerning hypothermia, in what way can effect the diver and what can it do to him while diving. What I am trying to say is that if I am very cold in the water, of course I have to adored the dive, but if I am doing some deco stops what could happen to my body concerning off gassing if I was very cold. Or could it affect something else.
Hi again Wazza,

Forgetting about hypothermia for a moment I am sure you will realise no-one really fully understands what happens to gas transfer overall when a diver's body temperature changes.

What I do know is this.

1) The solubility of gasses is decreased with increasing temperature. Thus if the diver is already cold at the start of a dive his tissues can hold more gas molecules before they become saturated. Once he has rewarmed this extra dissolved gas must come out of solution. Hence the need for increased conservatism when diving in very cold water. This is also another reason why post-dive hot tubs and heavy exercise are not recommended as rewarming reduces gas solubility.

2) On the other hand, the rate of diffusion is increased with temperature, reducing the tissue half times for the affected tissues and theoretically lessening total deco obligations.

3) I am aware that in the '70s, at the London Hospital, Professor Keating researched hypothermia using pigs carcasses. Not suprprisingly his findings could not be directly applied to live animals because they have a circulation. An unregulated circulation in a live animal serves to speed up the heat transfer from the periphery to the core and visa-versa. However, as you know living animals have reflexes to prevent this. The most important is peripheral vasoconstriction in response to cold. This reduces peripheral tissue perfusion to preserve core temperature. The down side is reduced perfusion directly reduces offgassing, thus increasing the half-times for the affected tissues with an attendant increase in deco obligations.

If my understanding is correct, recreational deco shedules assume a constant body temperature.

Now to hypothermia

Hypothermia occurs when the heat conserving mechanisms are unable to prevent the core temperature from falling any further. Even on land this will happen if an individual is not wearing sufficient protective clothing. The heat loss in an unclothed and submerged diver is over twenty times faster than in the air and even in tropical waters this can lead to true hypothermia. (The life expectancy of an uprotected man-overboard in the North Sea in winter is less than 15 minutes.)

The danger is this. Once the body's core temperature falls below a certain level the reflexes I mentioned cease to work effectively so heat loss is accellerated. (These reflexes require energy, which is no longer available as the enzymes needed for its generation are less efficient at lower than normal temperatures.) The victim tends to feel better because he has stopped shivvering, for example, but is actually in a very dangerous situation made worse by the fact that the brain no longer functions properly. He is much more likely to make dangerous mistakes in judgment, made even more likely bacause hypothermia causes a state of euphoria or a feeling of well-being. In the case of a fell walker he may be lulled into a false sense of security and stop to sleep - never to wake up.

I am sure there are other factors in diving but to me the one that matters the most is, like narcosis, the inability to think properly and to make the right decisions in an alien environment. This is why, in Britain at least, the mantra is plan the dive (on the surface when you are thinking straight) and dive the plan (because any decision to change the plan made underwater is likely to be based on false assumptions.) Technical divers frown on dive computers for this reason alone.

I have tried to make this simple, Wazza but in reality it is very complex.

Hypothermia is a killer and must be avoided at all costs
 
Dear Dr. Paul
Thanks a lot for your explanation, I did understand most of it and I know exactly what u mean. But I am going to tell u what I know from what I read from here and there , and hope u can correct me if I am wrong as u are a Dr. after all and I am jut a diver.
So:
1- the blood circulation in the body is formed from 2 parts one comes from the heart to the brain and one comes from the heart to the hall rest of the body. (I don’t know if its cold the big circulation and the small circulation ) So when u feel cold, pumping blood to the brain will be more, then pumping blood to the rest of the body that means the off casing from the body will be less and u will surface and u think that u have finished your deco or your safety stop but in reality u did not, ( as I said the circulation was slower in your body then to the brain)
2- and why the fingers and twos feel cold first, cos the veins are very very small there and as the circulation is not pumping properly and the blood is not reaching this aria as normal so the off casing will be slower.

So this is what I know and this is how I could explain it, I think it could be explained in a better matter. But hope u can tell me is this true or not and if not what is the truth ?thanks again .
 
wazza once bubbled...
1- the blood circulation in the body is formed from 2 parts one comes from the heart to the brain and one comes from the heart to the all rest of the body. (I don’t know if its called the big circulation and the small circulation )
It is not as simple as that, unfortunately Wazza. There are indeed two circulations, but one is from the left side of the heart to the whole of the body, including the brain. The other is from the right side of the heart through the lungs. The lung circulation is ALWAYS equal to the peripheral circulation because the two systems are in series. What this means is that if output from the left ventricle is increased, because of exercise for example, the venous return to the right side of the heart is increased by the same amount so the output from the right ventricle through the lungs is also increased. It is something like a figure of eight, if you know what that means. Left ventricle > whole body, returning via the veins to the right atrium> right ventricle > lungs > left atrium > left ventricle. Round and around it goes!

In health, the body reflexly controls the arterial blood supply to the vital organs so that the brain and the kidneys, for example, will always receive sufficient oxygen and nutrients. In the case of a massive haemorrhage blood flow to the skin, muscles and digestive system is reduced almost to zero.
So when u feel cold, pumping blood to the brain will be more, then pumping blood to the rest of the body that means the off casing from the body will be less and u will surface and u think that u have finished your deco or your safety stop but in reality u did not, ( as I said the circulation was slower in your body then to the brain)
No wazza, it does not work like that at all!
2- and why the fingers and toes feel cold first, cos the veins are very very small there and as the circulation is not pumping properly and the blood is not reaching this area as normal so the off gassing will be slower.
Thats about right!

The fingers and toes are not vital organs and they are also exposed so blood flow to these is reduced to conserve heat in a cold environment. They not only feel cold, they will be cold.

In extreme cases of hypothermia in arctic conditions the victim can lose fingers and toes from frostbite as they are effectively sacrificed by the body actively shutting-off their blood supply in order to protect the vital organs.

I hope this helps.:doctor:
 

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