Narked on Nitrox

[Stu Sheridan]

<font color='#0000FF'>Guys, just to clarify somthing.

END is just as relevant with Nitrox as it is with Trimix.
Each mix has a ratio of Nitrogen that can be compared with an air dive to a similar depth.

Fair enough, this is one of the main aims of trimix (lowering END) but it applies to any gas mix in comparison to air.
IMO as long as a gas can be considered narcotic, it can have an Air END.

Stu.

[Phil Ennis]

<font color='#810541'>If you consider o2 to be as narcotic as nitrogen then surely the END doesnt come into it. Only when you add He do you lower the narcosis.

I was taught to consider o2 as narcotic as Nitrogen, PADI and IANTD.

[Ian Murray]

Originally Posted by [b

Quote[/b] (kirky @ Nov. 22 2003,21:27)]The only other info was that it was my first 30 this year so maybe I just need more exposure to this depth.

My point was - given the reduced N2 in the mix over air, I did not expect this and wondered if anyone had experience/info on this. My PPO2 was Ok (about 1.4 max) so I assume the effect was N2 induced

Kirky,

How was your descent for this dive?.

I find that if I do a rapid descent it usually causes a narked feeling for the first few minutes of a dive.

A nice slow descent seems to cure the problem or at least make it less noticable.

[Conor]

I'm not even Nitrox qualified, but I am interested in the gas laws being applied.

So would the following be right according to the tables ?

32% Oxygen =&gt; 68% Nitrogen, Pressure at 30M 4 ATM

ppN2 = 0.68x4 = 2.72

Surface Air 21% O2 =&gt; 79% N2

equivalent pressure on air =&gt; 2.72/0.79 = 3.44 ATM

So that means in terms of narcotic effects of Nitrogen at 30M of a 32% mix is equivalent to diving to 24.4 M (approx) on air.

So if a diver normally gets narked around 25 M the same diver could get narked at 30 on this mix, especially if he has some of the other risk factors (tiredness, cold, dehydration, stress etc).

Does this make any sense ?

Cheers

Conor

[chrisch]

Conor - you are correct.

The calcs are correct - go do your EAN at once!!!

END and EAD are the same thing for nitrox - END for trimix refers to the PPN2 as a general rule and most of us do not bother with O2, which is wrong really as it is narcotic...

Cold water increases narcosis which may explain the event.

Chris

[Conor]

I do want to do the EANx course, mostly cos I am interested in the science.

On the subject of Narcotic effects of Oxygen, I found the following that states;
&quot;In recreational divers, if oxygen has any narcotic effect at all, it is far less narcotic than nitrogen.&quot;
http://divermag.com/archives/dec96/d...tor_Dec96.html

Hope this is of interest

Conor

[Dr Stevil]

A different slant for you Kirky, perhaps you're just &quot;high on life&quot;

Sorry but I can't come to terms with &quot;great&quot; and &quot;Stony&quot; in the same sentence, surely a non sequiteur...

[chrisch]

For more on O2 narcosis read Kevin Gurr's article:

http://www.iantd.co.uk/IANTD/pages/TA%20Kev%20Gurr.htm

Chris

[Conor]

Odd point....

The latter article states;
'What does this mean to us as divers? Oxygen is potentially twice as narcotic than Nitrogen. The upside being that at the partial pressures of oxygen within which we normally operate (0.21 to 1.6), oxygen narcosis is not a relevant issue'

The phrase 'Oxygen is potentially twice as narcotic than Nitrogen' strikes me as quite bizarre and possible in complete contradiction to the previous linked article.

Have to confess, I'll go with the Doctor on this one

[Mark Chase]

Originally Posted by [b

Quote[/b] (camdiver @ Dec. 05 2003,13:14)]Odd point....

The latter article states;
'What does this mean to us as divers? Oxygen is potentially twice as narcotic than Nitrogen. The upside being that at the partial pressures of oxygen within which we normally operate (0.21 to 1.6), oxygen narcosis is not a relevant issue'

The phrase 'Oxygen is potentially twice as narcotic than Nitrogen' strikes me as quite bizarre and possible in complete contradiction to the previous linked article.

Have to confess, I'll go with the Doctor on this one

Funny I was told that 02 is AS narcotic as Nitrogen but not twice as?? But the science is based on weight of the gas or density of the gas and in those terms 02 is as narcotic as Nitrogen. However as 02 is metabolised by the body the effect is reduced so if 02 has twice the density of N2 then perhaps that explains the reduction.

Truth is if you think its better it will be. At Nitrox depths narcosis can be controlled by will power and confidence but it’s definitely still there waiting to bite you if things get a bit stressful.

I find it annoying that you have to spend more money on yet another course to do Helium Trimix diving. It’s far easier to learn than Nitrox as it has less affect on the dive. There should be a 50m cert for He, which is cheep (say £50) and allows people to dive a safe gas to recreational depths. 10 and 20% He fills are not that expensive and they make a massive difference in the 35 -50m range

ATB

Mark Chase