Argon bottle mounting

[Mark Chase]

Originally Posted by And

I'm no expert, but there are a number of differences which were much better explained by Frank. Conceivably these will effect the deco in any number of ways. For example;

• What if the stepped decreases in inerts, whilst making use of the oxygen window with a higher po2, actually 'flushed' the inerts out of the cells in a more efficient manner than just a gradual reduction, shocking the gas exchange into action perhaps?

• Anything is possible and there was an old school of thought that said ascend at 20m/min to the first stop depth to invigorate the blood Mad as march hairs but that was a theory.
  
  
  

  What if the po2 of 1.3 doesn't help the gas exchange as much as 1.6, maybe the difference is not a simple linear relationship?

  Not relevant as decoing out on Trimix you will never achieve 1.6pp02. One assumes you would be on1.4 or less on the bottom and ever decreasing on the way up.
  
  

  A colder gas increases the metabolism as the body needs to generate more heat to protect the core temperature, therefore increasing the speed at which the blood travels to the tissue cells and back. Although this will need to be balanced to stop restricted flow to the extremities, it may actually make the gas exchange more efficient than breathing warm, moist gas.

All the info I have ever read on Deco from PADI recreational dive planner on wards instructs us to extend deco in cold conditions. Cold causes blood vessels to contract and blood vessels are fairly critical to off gassing. Therefore I would suggest this theory is way off the map.

Finally, if you were doing an hour at 30 mtrs on 30/30 then o2 would be recommended for deco, I wouldn't choose to deco out just on backgas. For a 30 minute dive, fine, but then we are not really on a deco dive at that point are we?

Yes but isn't GUE guidance on lost deco gas is to deco out on back gas using air tables and ignoring the He?

The shorter the bottom time the more you can take the piss out of deco. Mark Elliot told me once how switching from 13/75 to 32% was going to bend me. When I told him I had done it and not been bent he said I bet you were on the bottom less than 30mins. And he was right. Increase the bottom time and the margin for error gets smaller and smaller. However the question is if we are getting away with it due to shorter bottom times are we in fact doing cumulative sub clinical damage to our bodies? The fact we walk away today may come back and haunt us later in life.

I just think it is unwise to compare the two and make sweeping statements about how 'dangerous' one way is over the other, without referencing ALL possible reasons for those assumptions.

Mabey but I think we have covered it now and I stand by my original statement that off gassing is off gassing no mater how the gas is delivered. The only gray area I can see is the dynamic of C02 in the loop assuming Martin Parker is telling porkies.

ATB

Mark Chase

[Mark Chase]

Originally Posted by Foggy

Has this thread strayed somewhat, or is it just me?

Cheers, Paul

Sorry, but at least its an interesting discussion come on how many pages can you do on how to mount an argon tank


ATB

Mark Chase

[Foggy]

Originally Posted by Mark Chase

Sorry, but at least its an interesting discussion come on how many pages can you do on how to mount an argon tank


ATB

Mark Chase

True, but it could have been separate - under amore relevant title?

Anyhoo, I still like Bob Coopers gaffa tape DIR affair

Cheers, Paul

[Tim Davies]

It seems that the 'cave' mounting point as the most advantages (from what you're all saying) but suffers becasue the valve is too low and the hose a bit long. And of course, inverts aren't allowed in DIR

So why not mount it in the same place, but right way up, then the valve won't get bashed about, and hte hose can be really short. Or is that just to simple a solution to allowed??

...reeling back in....

Paul, the picture shows the 'wreck' style ('cave' is velcro-strapped to cylinders). Mounting the bottle 'right way up' would make access to the valve and securing to the backplate while maintaining removability more difficult, among other things (sleepy now...).

[Spike Jackson]

Originally Posted by Depth-junkie

I thought that there is a small amount of CO2 left in the loop regardless, and you need this as it's what triggers the bodys response to breath. It's the amount at what level to which it is maintained that is critical.

ATB
Gareth

No. The body's need to breathe is triggered by CO2 in your blood, not in what you're breathing. In normal atmospheric air there is effectively zero Co2.

[Andy Phillips]

Cor a decent thread;

Those that have had these discussions in the past where I have been involved will know that I am very loosly involved with a group of researchers in London looking at bubble mechanics, whilst they are not working on decompression theoryas such there research has relevance and I have played cell doner for them a few times because I do decompression dives.

O2 window, hmmm, an interesting theory, but apparently cobblers, where they do agree is the need for a gas gradient, i.e. high pressure in the tissue to low pressure in the blood. These guy's have been doing research on bubble mechanics in single mammalian cells, it is quite interesting to watch a cell explode as the bubble grows inside it. The bottom line, the bubble needs to be small enough to pass through the cell membrane. SLOW ASSENT RATES ARE GOOD.

Now admittedly, we are not normally working down to the single cell level, but if we follow this through to a logical conclusion, SMALL STEPS ARE BEST. A lot of empirical evidence backs this up, it is nothing new, but it was very interesting to see it in action.

The bottom line, you need a gradient, but not too high a gradient, and you need to move up slowly to minimise the actual damage you are doing to yourself. Shocking the cells is a bad idea Andy, you can almost hear the little buggers popping from here.

The problem Mark and I had was / is obvious, we just were not creating a sufficient gas gradient for the He to leave our tissues / cells, in other words we were getting out bent to buggery on He. So logically, He in a deco gas is bad, but on deep long dives, no He in a deco gas is bad because the gradient is too high. The CCR wins here because in theory the PPHe of the gas in the loop is reducing as we get shallower, but for Mark and myself, we did not reach a point where it was a big enough gradient towards the end of deco. An He free gas on the last stop was / is a good idea for Mark and myself, everybody else can do what makes them feel happy.

Warm versus Cool, err, wrong Andy, in truth, it is the bodies core temp that is the issue, and that is because it restricts the blood flow to the extremities, i.e. fingers and toes when it gets to a dangerous level, which is what frost bite is all about. This is the reason you increase the deco time, not reduce it for cold. You are better off being warm, so in theory the CCR is better. But lets face it, the temp of the gas makes little difference to how cold you are, though in my experience I don't feel quite as cold on a CCR as I do on OC, that being said, a lot goes on in my head that my hands and feet don't necessarily agree with.

Right, I shall now crawl back into my hole.

Andrew

Originally Posted by And

I'm no expert, but there are a number of differences which were much better explained by Frank. Conceivably these will effect the deco in any number of ways. For example;

• What if the stepped decreases in inerts, whilst making use of the oxygen window with a higher po2, actually 'flushed' the inerts out of the cells in a more efficient manner than just a gradual reduction, shocking the gas exchange into action perhaps?
• What if the po2 of 1.3 doesn't help the gas exchange as much as 1.6, maybe the difference is not a simple linear relationship?
• A colder gas increases the metabolism as the body needs to generate more heat to protect the core temperature, therefore increasing the speed at which the blood travels to the tissue cells and back. Although this will need to be balanced to stop restricted flow to the extremities, it may actually make the gas exchange more efficient than breathing warm, moist gas.

Finally, if you were doing an hour at 30 mtrs on 30/30 then o2 would be recommended for deco, I wouldn't choose to deco out just on backgas. For a 30 minute dive, fine, but then we are not really on a deco dive at that point are we?

I just think it is unwise to compare the two and make sweeping statements about how 'dangerous' one way is over the other, without referencing ALL possible reasons for those assumptions.

Andy

[Spike Jackson]

Originally Posted by Andy Phillips

. SLOW ASSENT RATES ARE GOOD.

Now admittedly, we are not normally working down to the single cell level, but if we follow this through to a logical conclusion, SMALL STEPS ARE BEST. A lot of empirical evidence backs this up, it is nothing new, but it was very interesting to see it in action.

The bottom line, you need a gradient, but not too high a gradient, and you need to move up slowly to minimise the actual damage you are doing to yourself. Shocking the cells is a bad idea Andy, you can almost hear the little buggers popping from here.


Andrew

I am no deco expert (though I do have a fair grounding in physiology) and this makes sense to me.

DCI is caused ultimately by excessive supersaturation of an inert gas. Whether that supersaturation is created by an excessive ascent rate causing the drop in partial pressures or whether the massive drop in partial pressure is caused by changing to a radically different gas mixture with a much lower partial pressure of the inert gas your body is saturated with would not seem to me to make any difference. The excessive gradient would be the same in either situation.

[Andy Phillips]

Spike,

The reason this makes sense is because I am correct, the reason I know that it is correct is because any one who say's any different is incorrect, I know this because I am never wrong. I thought that you would already know that and therefore comment would have been unnecessary .

Blanaid was threatening to set up a Tuesday dive so we could all hook up for a paddle befoe Christmas, don't know if she got hold of you but would you and Clair be up for it.

Andrew

Originally Posted by Spike Jackson

I am no deco expert (though I do have a fair grounding in physiology) and this makes sense to me.

DCI is caused ultimately by excessive supersaturation of an inert gas. Whether that supersaturation is created by an excessive ascent rate causing the drop in partial pressures or whether the massive drop in partial pressure is caused by changing to a radically different gas mixture with a much lower partial pressure of the inert gas your body is saturated with would not seem to me to make any difference. The excessive gradient would be the same in either situation.

[Janos]

Originally Posted by And

[*]What if the stepped decreases in inerts, whilst making use of the oxygen window with a higher po2, actually 'flushed' the inerts out of the cells in a more efficient manner than just a gradual reduction, shocking the gas exchange into action perhaps?

All the O2 window theories I've seen refer to inert gases and I see no reason why the O2 window (if it existed) would apply more to He than to N2 (except of course that (IMHO) Helium is a little more dangerous than Nitrogen). Thus we would expect the same result if we were using Nitrox as a diluent, and I think[1] that Mark and Andy felt significantly worse on trimix dil than they have when decoing out on Nitrox dil.

Originally Posted by And

[*]What if the po2 of 1.3 doesn't help the gas exchange as much as 1.6, maybe the difference is not a simple linear relationship?

Then again the same would appear on Nitrox, which it doesn't.

Originally Posted by And

[*]A colder gas increases the metabolism as the body needs to generate more heat to protect the core temperature, therefore increasing the speed at which the blood travels to the tissue cells and back. Although this will need to be balanced to stop restricted flow to the extremities, it may actually make the gas exchange more efficient than breathing warm, moist gas.

In which case you could flush your suit with trimix as well on the deco - that would make you colder and increase your metabolic rate too. Or you could not do up your p-valve properly and open that on your stop.

Janos


[1] - Although happy to be corrected - but I know you fellers use Trimix dil most of the time now

[Mark Chase]

[1] - Although happy to be corrected - but I know you fellers use Trimix dil most of the time now

Presently using 16/55 for everything between 0m and 70m. Only other dill gas I have used is Air. We now always spend minimum 15mins deco on pure 02to flush the He out because we prety much dont do any dives with less than 30mins deco


ATB

Mark Chase