The narc fairy comes to visit....

[Dave Sutton]

The thing is, if you want to respect normal PP02 exposure limits, there's a pretty small window of depths in which you can do a side-by-side comparison between air and enriched 02 nitrox on open circuit, which is the only fair test. Using 21% and 32% side by side, which is the split that is most notable, you really can't do side-by-side tests much deeper than 120 feet-ish. At 100 there is a definate narcosis difference... but you need to be pretty sensitive in your ability to detect it.

Never even thought about it using He mixes..... just my empirical observations changing the variables we are discussing, which are just 02 v/s Nitrogen ratios in an open circuit gas supply.


Dave

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[Bobjr]

The thing is, if you want to respect normal PP02 exposure limits, there's a pretty small window of depths in which you can do a side-by-side comparison between air and enriched 02 nitrox on open circuit, which is the only fair test. Using 21% and 32% side by side, which is the split that is most notable, you really can't do side-by-side tests much deeper than 120 feet-ish. At 100 there is a definate narcosis difference... but you need to be pretty sensitive in your ability to detect it.

Never even thought about it using He mixes..... just my empirical observations changing the variables we are discussing, which are just 02 v/s Nitrogen ratios in an open circuit gas supply.


Dave

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Are you conducting double blind and controlled experiments? Otherwise its just your subjective opinion not empirical evidence. Personally (my subjective opinion) I can't notice difference between air and nitrox although Richard Pyle in the old days was sure Nitrox was more narcotic (gain his subjective opinion).

The only hard data we have is chemical properties and these suggest that Oxygen is more than 2X more narcotic than Nitrogen (although we don't know how much of the oxygen is metabolised in the myelin sheath).

I have noticed conducting complicated scientific work (filling in worksheets of 50-60 species over many transects) that I can not concentrate at relatively shallow depths (10-15m) and didn't know what was going on - I would say narcosis.

One thing for sure - Helium is good and in a RB I never see the need to be without it at any depth :banana2:

Graham

 

[nickb]

The thing is, if you want to respect normal PP02 exposure limits, there's a pretty small window of depths in which you can do a side-by-side comparison between air and enriched 02 nitrox on open circuit, which is the only fair test. Using 21% and 32% side by side, which is the split that is most notable, you really can't do side-by-side tests much deeper than 120 feet-ish. At 100 there is a definate narcosis difference... but you need to be pretty sensitive in your ability to detect it.

I did think of a test comparing say 36% with 6% nitrox and 6/30 trimix whilst undertaking some cognitive tests.

If O2 is significantly less narcotic than N2, the difference in the first two should be marked, whilst replacing 30% O2 with He should make little difference.

If not, then there ought to be a marked difference between the first two and the trimix.

 

[Mr fish]

My mileage has no opinion either way really, as I said above.

However, many people's experience doesn't tally with reality. The internet is awash with heroes that have never been narc'd or say that 50m on air never did them any harm. Subjectivity is remarkably inadequate for measuring many things.

Oxygen has properties that would seem to lend themselves to inducing narcosis and that's good enough for me to include that possibility in my calculations. I could still have used 25% at 45m when I was diving OC and reaped some benefit over air, but I'd still have been dysfunctional. Anything over 40m was enough for me to want to use some helium, regardless of the conditions.

With closed-circuit, even 30m with air dil is unpleasant, so the calculation above is just a game but I hope you enjoyed your lollipop

See id use 24% down to 50m and not cos i think it would be safer than air,

id need the 24% back gas to cover my o2 pony , on the off chance she run amuck at 6m ,,

tho im with you on using heluim on the breath ,, good for the WOB and it cost not a lot ,, so why not ,,

mind you , ken would dive to 50 on tm and sit at 21m for 20 mins with his ali 80 of 50% then up and out,

see we all seem to be doing it wrong ,, lol



ps iv had a few pot runs with my club ,, just for fun ,,, i could feel the narc,s at less than 20m ,, lol

edit ,, i remember having to do a narc test for my (blue) deep air/buspass card ,, 50m at dotty, i gets a card saying (wright your name backwards on that big slate ,,, lol

i could not do it back wards ,,, i had to run the letter in my head forward , then wright the letter .. then do the same again, run the letters forward in my head till i got to the one i needed next ,,

 

[matt]

You could try 21/79 versus 10/90 at 60m and see if O2 is narcotic?

Matt.

 

[nickb]

You could try 21/79 versus 10/90 at 60m and see if O2 is narcotic?

How would that work?

 

[Iain3]

Qucik math test: At what depth using air as diluent and a 1.2 PP02 setpoint does your rebreather become MORE narcotic than breathing air open circuit?

.

If you consider oxygen to be equally narcotic to nitrogen then never?

 

[matt]

How would that work?

Perhaps I'm not following - you're saying O2 is narcotic. On paper it is. In practice I don't see it.

How shall we test if it is narcotic?

We know 10/90 is not giving narcosis at 65m. We want a practical test that oxygen is narcotic (we know nitrogen is) so the only thing we can increase is oxygen - 21/79 was my suggestion. Go for 50/50 if you dare...

Matt.

 

[Bythesea]

I'm bored of my own thread now, is O2 narcotic? If it were I think we would have scientific proof by now, wouldn't we? It seems a hot topic so surely Rubicon or some such facility would have made a paper....

I don't know but I do know lowering the Nitrogen works a treat....

 

[matt]

I'm bored of my own thread now, is O2 narcotic? If it were I think we would have scientific proof by now, wouldn't we? It seems a hot topic so surely Rubicon or some such facility would have made a paper....

I don't know but I do know lowering the Nitrogen works a treat....

Spoil sport. Where's the like button...

 

[Mr fish]

I'm bored of my own thread now, is O2 narcotic? If it were I think we would have scientific proof by now, wouldn't we? It seems a hot topic so surely Rubicon or some such facility would have made a paper....

I don't know but I do know lowering the Nitrogen works a treat....

sockpuppet is what you need , you can chat to your self all night never get board .. just look at that apox thread over on that udder forum ,,

adw having a fine old time over there ,, if you look at all the names in them post i think only two ant awd .. Brad and Matt,
im off to get me some 50/50

:hehehm:

 

[Dave Sutton]

Perhaps I'm not following - you're saying O2 is narcotic. On paper it is. In practice I don't see it.

How shall we test if it is narcotic?

We know 10/90 is not giving narcosis at 65m. We want a practical test that oxygen is narcotic (we know nitrogen is) so the only thing we can increase is oxygen - 21/79 was my suggestion. Go for 50/50 if you dare...

Matt.

Kind of irrelevent on a CCR where the PP02 is fixed... diluent only changes inert gas ratio, not 02 fraction at any depth. At depth "X" the 02 fraction in the loop will always be the same. What will you prove? That more helium v/s more nitrogen is less narcotic? I think that's been done already...

These tests really need to be done without any helium in the mix... and done open circuit. Compare nitrogen and 02 at different ratios ranging from 100% 02 to 21% 02 at a constant depth and that's the only real way to discriminate it out. Naturally you have issues with 02 tolerance and hypoxia, so the depth band for testing is pretty small. Like I said before, the easy test is at 100 feet using air and then using 32% nitrox. There is a definate narcosis reduction with the nitrox.



(And not to make matters stupid... don't DO this: But I've bounced to 190 on 32% Nitrox (Open Circuit) and the narcosis there was WAY less than the narcosis at that depth on air... like I said DON'T TRY THIS: It was dumb then and it's dumb now... sometimes we live and we learn... 2.2 PP02 is not the place to be (for long).)



Best,

Dave

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[Mr fish]

Kind of irrelevent on a CCR where the PP02 is fixed... diluent only changes inert gas ratio, not 02 fraction at any depth. At depth "X" the 02 fraction in the loop will always be the same. What will you prove? That more helium v/s more nitrogen is less narcotic? I think that's been done already...

These tests really need to be done without any helium in the mix... and done open circuit. Compare nitrogen and 02 at different ratios ranging from 100% 02 to 21% 02 at a constant depth and that's the only real way to discriminate it out. Naturally you have issues with 02 tolerance and hypoxia, so the depth band for testing is pretty small. Like I said before, the easy test is at 100 feet using air and then using 32% nitrox. There is a definate narcosis reduction with the nitrox.



(And not to make matters stupid... don't DO this: But I've bounced to 190 on 32% Nitrox (Open Circuit) and the narcosis there was WAY less than the narcosis at that depth on air... like I said DON'T TRY THIS: It was dumb then and it's dumb now... sometimes we live and we learn... 2.2 PP02 is not the place to be (for long).)



Best,

Dave

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i was on a dive trip in 2005 ,, we had o2 pumped down to us on the deco station 13 regs ,12 you could hit at 6m, the other reg no 13 went down to 10m and had a scrapper hanging of it ,

the skipper of the boat would dive some days also ,, he would always come up 20m plus a min , go on the o2 at 10/9m
and do ten mins at 9m then he would move no up get under his boat and get two work with the scrapper ,, till his deco was done ,, once back on deck first thing was a large G&T and a smoke ,, think he was hitting 68 years and he was looking good

 

[Dave Sutton]

the skipper of the boat would dive some days also ,, he would always come up 20m plus a min , go on the o2 at 10/9m
and do ten mins at 9m then he would move no up get under his boat and get two work with the scrapper ,, till his deco was done ,, once back on deck first thing was a large G&T and a smoke ,, think he was hitting 68 years and he was looking good

I think we need to motion this to become the official CCRx Deco protocol... With further testing required, naturally. Various Gins, and various smoking products need to be fully vetted, of course... no sense for a rush-rush conclusion, eh?


Note aside: Offshore we routinely did 02 deco at 40 feet. Hundreds of hours spent there in a year by our divers, thousands perhaps. Company had been doing it for decades. It was a Bill Hamilton developed table, BTW. Never even dreamed of an 02 hit. Oh well... that was then and this is now.


Dave

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[Mr fish]

I think we need to motion this to become the official CCRx Deco protocol... With further testing required, naturally. Various Gins, and various smoking products need to be fully vetted, of course... no sense for a rush-rush conclusion, eh?


Note aside: Offshore we routinely did 02 deco at 40 feet. Hundreds of hours spent there in a year by our divers, thousands perhaps. Company had been doing it for decades. It was a Bill Hamilton developed table, BTW. Never even dreamed of an 02 hit. Oh well... that was then and this is now.


Dave

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He was a commercial diver in his youth ,,
why it stuck in my mind is not the 9m stop but the hard work he would put it under the boat 45 / 60mins with the scrapper ,,

 

[Dave Sutton]

He was a commercial diver in his youth ,,
why it stuck in my mind is not the 9m stop but the hard work he would put it under the boat 45 / 60mins with the scrapper ,,

Perhaps he had never heard of antifouling bottom paint... :doh:

The 02 tox limits that we use as standard as sport divers were the end result of a huge political compromise between the training agencies at the very dawn of sport nitrox diving. 1.6 was our standard gas offshore... mixed on the spot by the rack operators so as to produce minimum deco obligation. Go from that to pure 02 at 40 feet every dive of the week and collect your check. And before folks start talking about "fit young carefully selected divers"... Uhh... the old farts were all fat Bioprene-Insulated chain smokers who ate a pound of bacon every day just to keep their gullets lubricated for lunch. Nothing magic.


Dave

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[matt]

Kind of irrelevent on a CCR where the PP02 is fixed...

Yer, if you're doing my test then take some OC bottles...total waste of time CCR.

Didn't follow the no-helium point, seems backwards to me, but the whole things also seems OT.

Matt.

 

[matt]

i was on a dive trip in 2005 ,, we had o2 pumped down to us on the deco station 13 regs ,12 you could hit at 6m, the other reg no 13 went down to 10m and had a scrapper hanging of it ,

the skipper of the boat would dive some days also ,, he would always come up 20m plus a min , go on the o2 at 10/9m
and do ten mins at 9m then he would move no up get under his boat and get two work with the scrapper ,, till his deco was done ,, once back on deck first thing was a large G&T and a smoke ,, think he was hitting 68 years and he was looking good

Is this in the SCS?

 

[PeterN]

Back in the early 90's we were doing deep air to "get used to being narced at depth."

Even then we knew about PO2 and the deepest I went was 211 Feet. Commonly we went to 170 - 180 feet on air.

What got me was how varied my responce was. One day I could write things down that made sense, a few days later I was zonked.

IMHO you would need a large sample size to prove anything, and then the conclusion would probably be that individual responces vary greatly. Also I expect that dehidration, fatgue, water temp and clarity etc. make a huge difference.

I do not believe one gets used to narcosis and almost all my ccr dives are now on mix.

Peter

Peter

 

[matt]

I do not believe one gets used to narcosis and almost all my ccr dives are now on mix.

Once a year I like to bob down to 60m or so on air (usually in blue water), just for the nark. Not quite a GnT, but just as much fun!

Matt.