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Hi All,

It’s very easy to see why bubbles form in the blood/tissues if one has a rapid ascent, as I understand it, the dissolved gasses are coming out of solution and expanding faster than the body can off gas through respiration.

However, this in itself (the expanding bit) causes me some confusion. We’ve all been taught not to go out, exert ourselves and get blind drunk after a dive, especially after a deep long one. We know this can bring on DCS, but why? I know that certain activities can slow down the bodies off gassing process but several hours after the dive the bulk of the gas will be gone and what’s left will not suddenly decide to expand unless there is a rapid drop in ambient pressure.

Anyone know please.
 

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A VS Cash Cow
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whats is 'after' a dive - 10 minutes, 1 hours, 6 hours....

most times you'll be looking at, at least, 2 hours after a dive before begining to drink.
 

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Alcohol is a vaso-dilator (spelling?) and I'm sure that this has an impact upon where any micro-bubbles can get to. Also alcohol dehydrates us and I know dehydration is often a factor in DCI.
 

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"Three sheds"
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After a dive your body is saturated with gas. Not all of this is in bubbles. A good experiment is to microwave a cup of water for two or three minutes, then add a pinch of salt or sugar (try it). You get a shower of bubbles each formed around the nuclei of salt or sugar.

Nuclei don't have to be physical objects. You can also create nucliei by knocking the cup. Again you get a shower of bubbles. These nuclei are little pressure waves.

It's very hard for bubbles to form without nuclei.

One of the reasons post-dive exercise is bad is because the contracting and squishing of your body causes localised pressure waves. These act as nuclei and allow bubbles to form. Similarly if you damage your body during exercise [1] then this would also cause a lot of bubbles.

I've no idea why a post-dive beer is bad though.

Janos

[1] - Like me - I'm on crutches at the mo :(
 

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It's a quiet day in GP land, so I did a bit of hunting for research on beer and DCS. Couldn't find any, but I will offer my services to do the research if any of the major breweries wish to sponsor me. Especially Ringwood and Badger.

TBH I can't ever recall being specifically warned not to go and get bladdered post dive, and my experience of many liveaboard trips (several deep dives/day for several days, then beers until midnight) is that I haven't ever seen anyone get broken by this practice.

I think the vasodilator theory is maybe where this comes from - if you have bubble laden blood you want it going to your lungs and not so much to your skin.

Mines still a beer after a day of diving though...

CC
 

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"Three sheds"
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I think the vasodilator theory is maybe where this comes from - if you have bubble laden blood you want it going to your lungs and not so much to your skin.
All blood goes through the lungs, whether or not the skin is vasodilated. I can see that vasodilation will come into play underwater, but not so much once you've surfaced.

Janos
 

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working on janos' pressure wave bit.

if you are dehydrated, therefore have a low blood volume does this cause a higher heart rate / blood pressure, therefore you would have bigger pressure gradients as the blood is pushed though the heart, thus potentially causing more nucli and therefore bubbles?

all of that could be rubbish tho.
 

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Guru
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Its why it's not a good idea to hold onto a shotline on deco
 

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Finless: You couldn't invent him...
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most times you'll be looking at, at least, 2 hours after a dive before begining to drink.
It takes at least that long for the boat to get back in and get your kit stowed away?
 

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R.I.P.
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Its why it's not a good idea to hold onto a shotline on deco
I'd be more concerned about getting salt water in my pint whilst on the shotline than holding onto it, or can you put beer in those hydration packs ;)

and the cure for a mild skin bend is 3 pints of cider with a puff of O2 in between. Seems to work ok :D
 

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I fixed a permenant shotline to the Bretagne many years ago.
Chain 10m from the wreck, then thick line and @ 6m(ish) we had an alloy beer barrel... bloody great deco station....
 

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After a dive your body is saturated with gas. Not all of this is in bubbles. A good experiment is to microwave a cup of water for two or three minutes, then add a pinch of salt or sugar (try it). You get a shower of bubbles each formed around the nuclei of salt or sugar
& the moral is .. don't dive in a microwave? seriously, why is this? lower gas solubility in hot water?
 

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Best Computer I've Ever Had
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Do an advanced nitrox course, possibly with deco procedures. Rack up the 02, use air tables and you should finish your dive with minimal bubbles. So you can have a good few beers and the bubbles in it shouldn't cause you a problem:beer:
 

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i got alot of questions...
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Im pretty sure the effect of salt and sugar in hot water is nothing to do with pressure, its to do with heat being energy increasing the soluble rate of the sugar, which makes it a faster reaction. Sugar doesn't Bond to the molecules of the water, it just becomes a solution. if anything it would be to do with the surface area of the sugar and the rate of the breakdown into solution.
I dont see how this makes any difference to Alcohol and gas pressure in tissue, I think its the dehydration factor. In my Stupid days, we used to drink silly amounts...tank loads of water and dehydration salts. Go diving hungover but hydrated and no bend. That was Thailand though, where gas law doesnt apply :shade:
 

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Nigel Hewitt
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I can see the bubble generation arguments for not exercising shortly after a dive but I think alcohol is the converse of 'stay hydrated'.

Your body sees alcohol as a poison and pumps it out of your kidneys as fast as possible taking a lot of water out of circulation as it does. Alcohol dehydrates you and (anecdote not data) just about every 'undeserved' bend I've seen correlates to dehydration.

However I'd say it was irrelevant after an hour so glug down the bottled water on the boat ride out and back but don't worry about a beer or N with your dinner.
 

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& the moral is .. don't dive in a microwave? seriously, why is this? lower gas solubility in hot water?
Boiling produces bubbles (as the water turns to water vapour) but in a microwave it is possible for the liquid to become superheated and get above 100C without boiling. Microwaves work by being at the resonant frequency of water molecules and thus they 'excite' the water molecules making them vibrate more which is what we measure as a tempertaure rise. It happens at a microscopic level and is rapid allowing some regions to exceed 100C ahead of the molecules becoming gaseous and thus making bubbles. There is 'explosive boiling when a nucleation site appears...either grains of something or the knock which creates a pressure wave. (More physics is required to explain why the pressure wave allows bubbles to form but it does!)
 

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Creature of the night
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Boiling produces bubbles (as the water turns to water vapour) but in a microwave it is possible for the liquid to become superheated and get above 100C without boiling. Microwaves work by being at the resonant frequency of water molecules and thus they 'excite' the water molecules making them vibrate more which is what we measure as a tempertaure rise. It happens at a microscopic level and is rapid allowing some regions to exceed 100C ahead of the molecules becoming gaseous and thus making bubbles. There is 'explosive boiling when a nucleation site appears...either grains of something or the knock which creates a pressure wave. (More physics is required to explain why the pressure wave allows bubbles to form but it does!)
Nerd :kiss: ;)

Safe diving,
Steve
 

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ccr_ada top DAC guru 001#Blackberry pin 283E29BB
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i like a cider as soon after a long deco as poss as it makes me feel good
after 6 or 7 pints i feel even better and have been doing it for years!
but i do try and drink 1 to 1.5ltrs of berocca before diving the next day




it works for me

ada:popcorn:
 
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