Why do we blackout? Not how, WHY.

[perow1]

I started this thread some time ago:
[ame="http://forums.deeperblue.net/showthread.php?t=63651"]Diving response or survival response? Is a freediver fitter?[/ame]

My point was that for SURVIVAL it might be beneficial to black out early. The concious mind may be oxygen consuming. This has nothing to do with brain damage but for mere survival we should be able to turn off the oxygen to "less essential brain areas" aswell. I do not beleive this may be a function that has been gained to spare oxygen, but it might be an effect. If you do the anology with the car once again:

The car does not stop to save gas. BUT: When the car has stopped it does not use ANY gas. It might be possible to get it started under the right conditions.

I do not think that it is a prefferad way to save oxygen since brain damage might be a result. Still survival might be ensured.

If you can train to get a better defense mechanism (MDR) you should be able to train to reduce your defense mechanism by deleterious living. Or to put it another way: When you do not actively train to get better you train to sustain your low level. You can even train to get worse by deleterious living.

 

[perow1]

To make things clear i just want to add that i think the BO-state is less oxygen consuming than the concious state, but death is even less oxygen consuming. This is why i think BO is not a defense mechanism, just brain faliure. It just happen to be less oxygen consuming to be blacked out and chilled down than being concious and active.

 

[sickbugs]

Why do we blackout? Not how, WHY

cuz we hold our breath too long !


perow, why do u say that it is a brain faliure? doesnt the brain still work when you have blacked out?

blackouts, the way i see it, are basically our bodys own built in power saving device, under some conditions, a computer can go into standby mode, and use less power than when you are actually doing things with it, same thing as with yourself, when you have blacked out, your body uses less oxygen.. that said, i've never blacked out, so i cant give a personal view of it, my reply is just, at the most, an educated guess

 

[efattah]

As brain energy begins to decrease to critical levels, the GABA to glutamate ratio changes, in favour of glutamate. Glutamate then increases without limit. Glutamate is an excitatory neurotransmitter. When it becomes high, then 'random' electrical impulses in the brain are enough to make entire muscles shake.

 

[cdavis]

Very Interesting thread.

If the brain running out of energy is all there is to it, why do some divers wake up after a BO immediately after the mask comes off and long before any new O2 from the lungs could get to the brain? Seems like there has to be some brain activity that senses when air is available and resumes activity (the diver wakes up) before new 02 is actually available to the brain. If so, it argues pretty strongly that the brain is not completely out of energy and that there is some kind of protective mechanism working.

One speculative explanation that fits the energy exhaustion reasoning would be that higher brain functions (consiousness) require more energy than lower functions that could still sence the renewed availability or air. The idea requires that the body be able to somehow increase immediate energy availability, restoring consiousness to the brain before the new 02 gets there. I have no clue how such a thing could happen.


Connor

 

[efattah]

Blackout victims wake up after sniffing, even without a real inhale, because oxygen is transferred directly across the nasal membrane into the brain, even without going to the lungs. This is why, I think, that re-inhaling from the mask can prevent a blackout in the last few meters, even though the air may never reach the lungs.

 

[TNdiver]

interesting concept about the absorbtion directly into the brain. That makes perfect sense, if you consider that many illegal drugs are ingested in that way so that the effects are near immediate and the substance doent have to absorb into the blood stream or what not first. Also along with that theory the person wouldnt even have to sniffle at all, because once the mask is off the oxygen would difuse into the air in the sinsus and no other movement would really be needed. Another thing to consider, once out of water, there is much less pressure on the body, and it seems to me that once the outside pressure is released that the blood (especially from the extremidies) would flow much better and that blood may contain enough O2 to restart the system, and if it moves through the brain quicker because of less resistance then it would put more O2 in the brain. One last idea. This one is a little bit more "out there" though. I know that some animals, especially frogs, can absorb O2 through their skin. That is because of large abouts of capillaries near the surface and what not, but is it possible that we can do the same to a small extent, and maybe if the person was just barely over the limit that the small ammount available in that was would be enough? Also on the earlier comment about low O2 being the trigger to breath, i though that high CO2 was the true trigger to breathe......

 

[Skywalker]

Blackout victims wake up after sniffing, even without a real inhale, because oxygen is transferred directly across the nasal membrane into the brain, even without going to the lungs. This is why, I think, that re-inhaling from the mask can prevent a blackout in the last few meters, even though the air may never reach the lungs.

Hm maybe there are changing some molecules from the air to tissue or small vessels in your nasal ways but sorry I do not believe that there is any exchange that does effect your brain.

The absorbation of medics (or the white stuff) in your nasal ways works just like a nicotine strip poeple use to get rid of cig's just that the tissue in your nasal ways is much better perfused than your average skin and it is closer to your brain so anything absorbable will hit your brain very fast. All that said that does not make you grow alvoelus in your nose.

Robert

 

[perow1]

perow, why do u say that it is a brain faliure? doesnt the brain still work when you have blacked out?

I would call it brain faliure because the brain is not able to carry out its normal functions because of energy deficit. Yes, the brain still works, but it is working sub optimally. I would not call it brain faliure in the sense of stroke or whatever. It is always a problem of definition. It is extremely hard to in medical terms define a disease or what is healthy, in general terms. Health and disease is defined by convention in the medical world.

If the BO is an defense mechanism or not is evolutionary speculation. For us who beleive in evolution there is one important point to make. You make a serious error if you say that a certain trait has been developed to have a certain purpose. The very foundation of evolution is adaption. If we take MDR for instance. It has not been developed so that our ancestors would be able to go deeper to catch food. It is an effect of the surrounding they had. It just happened to be beneficial for those who had the first peculiar adaptations that led to the MDR. Several thousands of years passed and adaption went on. It NEVER reaches a goal and evolution is still goin on.

If the BO is a defence mechanism or not is like specultaing about if there is a design behind our adaptation. The question we should ask is not if BO is an adapted mechanism that saves us oxygen in critical situations. I think we should ask ourselves if the BO is oxygen saving or not (compared to the alternative) We should also ask what happens during a BO. How long can we go without suffering critical damage? Maybe a long time if you look at wictims being trapped under water for much longer than any of us can hold our breath. If we conclude that it is oxygen saving and that we can remain blacked out without damage can we then use this? Probably not, we would have to be able to black out and regain conciousness at will. Maybe possible, but i doubt it. I would say that it is no doubt that BO occurs because of energy deficit. But can the effect of adaptation be that this "failure" acctually can serve as protection? Not purpously, but by chance.

I think that blackout should be avoided since blacking out from holding ones breath for a long time desaturates the body of oxygen to near haardous levels for even a blacked out person. That is why i think that in extreme situations the person who blacks out fairly quick will be more likely to get in that tell-tale state of surviving under water for extreme times. A person who first desaturates his body by remaning concious will be at danger levels quicker.

 

[naiad]

Maybe blackout isn't meant to be a protective mechanism, but it can work that way sometimes.

 

[Observer]

The only way it could be "meant to be" would be if there were an intelligent designer behind it who wanted it to be like that, and I for one don't hold with creationism, and I thus disagree with descriptions of things our bodies (or those of other creatures) do as being "meant" to do anything. We don't adapt to the environment; the environment changes us. Think of the Douglas Adams "puddle" analogy. Imagine if a puddle could think, and it wakes up and sees that it fits the hole that it's in very precisely. "Very, very precisely," thinks the puddle, "in fact this is so good a fit it can't be a coincidence. I think this hole was made to fit me into it."

 

[naiad]

Sometimes 'meant to be' can just be a figure of speech. Saying that we are meant to eat food, or to breathe air doesn't necessarily imply that we were designed to do so. It can mean that we evolved to do so, and therefore it is probably an advantage to us to do things in a way that we are best adapted to.

Lucia

 

[perow1]

That´s exactly my point. A BO is an extrteme state and since we are unactive (almost totally) during it, it is a very low oxygen spending state. It is the next thing to death. That is why BO can serve as a defense mechanism as long as it is possible to bring back the person to life.

Onset: energy deficit
Effect: oxygen saving.

It is a defense mechanism in contrast to the alternative: death. If it is a defense against brain damage? Probably not.

 

[cdavis]

Going back to 02 absorbed through the nose tissue. How could this work? Even if absorption is enough to provide enough 02 to regain consiousness, the blood it would be absorbed into is headed back to the lungs, not into the brain. Absorption into interstitial fluid would have a hard time getting to the brain quickly. At the same time, "the white stuff" seems to get to the brain pretty quick after being sniffed. How quick is quick? Same time scale as recovering from a BO? Is it possible that the effects of sniffed drugs travel through other pathways(nerves?) than circulation, making a comparison moot? This is not an area I know much about.

Connor

 

[TNdiver]

Im not sure it even has to enter the blood stream to be absorbed, it may very well be taken directly in to the brain. I'll do some research on this and get back to the post with it. And i dont mean hands on research either:t

 

[Skywalker]

I can not imagine any direct transmition to the brain as there is no connection between the liquor your brain is having a swim in and your nose (unless you have cracked your skull what I do not hope).

Robert

 

[efattah]

The reason may be unclear, but it is very easy to show by experiment.

Do a static breath-hold until near blackout. Then, close your epiglottis, and pack through your nose -- i.e., suck air through your nose, with your epiglottis closed. This prevents the air from entering the lungs. Instead, it passes through the sinuses only. Notice the relief from hypoxia. In fact, by doing this continuously throughout the breath-hold, I'd bet a huge static time is possible, by cheating and getting O2 through the sinuses...

I've also heard that humans get as much as 8% of the O2 through their skin.

 

[Skywalker]

There were several posts in the david blaine thread (http://forums.deeperblue.net/showthread.php?t=65769&page=17&highlight=goldfinger) about the skin breathing thing. I fear that is not happening as well.
Is it possible that this "relief" is experienced because of the higher preasure in your lungs (with the same volume but I could imagine that by the packing process even when you are not packing in your lungs that the partial preasure in your lungs raisen due to contracting your muscles?)?

Robert

 

[naiad]

Another question - why do we samba? Most other kinds of hypoxic blackout, which are not caused by apnea, don't seem to cause spasms or convulsions. I used to nearly black out almost every day, when I got up in the morning, because of low blood pressure and tiredness. I have also passed out because of period pains. In these situations, there was never any twitching or other LMC. There was a fading of vision and hearing until everything goes black or grey and things sound distant. This has never happened in a blackout or samba caused by apnea - my vision and hearing remain normal before and after, and there is just a gap in my memory.

I thought that in all these situations the blackout is caused by the same thing - lack of O2 to the brain. Why is the reaction different?

 

[efattah]

Samba/LMC can happen from other types of blackout. I think the main issue is the timeframe. If the blackout happens more gradually, the glutamate level has more time to build up. If the blackout happens more suddenly (i.e. fainting or choking, from lack of blood flow to the brain), I think the glutamate doesn't have much time to build up.