O2 Narcotic

[Atomox]

From Wienke, Basic Diving Physics and Applications, 1994, Best Publishing.

The narcotic potencies of various noble gases. Wienke also refers to significant studies but does not provide any citations.


H2 He Ne N2 Ar O2
A (amu) 2.02 4.00 20.18 28.02 39.44 32.00
S(atm-1)0.0149 0.0087 0.0093 0.0122 0.026 0.0241
v 1.83 4.26 3.58 1.00 0.43 -

Where:
A - weight in atomix mass units
S - solubilities
v - relative narcotic potencies (referenced to nitrogen)

Brad

 

[Atomox]

it was formated nice when i sent it.........

 

[Dr Deco]

Dear Atomox:

[sp]These numbers, or at least very similar ones, appear in “The Narcotic Properties of Gases” in Bennett and Elliott’s book The Physiology and Medicine of Diving. I believe that was the original source.

Dr Deco :doctor:

 

[VTWarrenG]

This thread is ancient, but I didn't see what I believe is the "right answer," so I thought I'd bump it to the top again.

The "right answer," as I know it, is that oxygen and nitrogen are to be treated as equally narcotic. In practice, oxygen is probably not as narcotic as nitrogen, so assuming their equality is akin to rounding toward safety.

Now, one should ensure two things when calculating a mix:

1) PPO2 maximum 1.4 ATA.
2) Total narcotic gas pressure (PPO2 + PPN2) maximum 4ATA. This is the equivalent of diving air at 100 fsw.

You add helium to your mix as necessary to keep the total narcotic content below 4, and the PPO2 below 1.4. Simple, really.

- Warren

 

[O-ring]

Now, one should ensure two things when calculating a mix:
1) PPO2 maximum 1.4 ATA.
2) Total narcotic gas pressure (PPO2 + PPN2) maximum 4ATA. This is the equivalent of diving air at 100 fsw.

Let's say that I am diving a wreck in North Carolina at 115 fsw, but I am not trimix certified. I was planning to use EANx30, and am willing to live with the NDLs I am going to get with a 100 or 120 cf tank and my ppO2 using EANx30 is 1.4. Everything looks good, except if we go with the O2 narcotic stance then the END will always equal the depth since I am breathing some mixture of N2 and O2 regardless of the exact percentages.

What would you do on a dive like this when faced with an END of 115'?

 

[VTWarrenG]

O-ring,

I'd go get that trimix cert, of course.

"Narcotic content below 4 ATA" is equivalent to "no nitrox below 100 fsw."

- Warren

 

[The Iceni]

Lost Yooper's original thead on oxygen narcosis was at

http://www.scubaboard.com/showthread.php?threadid=4425&highlight=oxygen+narcosis

As I understand it oxygen induced narcosis is not seen in practice because oxygen is not an inert gas. It is biologically very active and is in effect a stimulant.

As Dr Deco rightly stated at the start of this thread the problem with oxygen is not it's narcotic effects but its toxic effects, which to all intents and purposes are equal and opposite and I for one do not include oxygen when calculating END.

If you do the maths for molecular weight and lipid/aqueous solubity fractions oxygen appears to be six times as narcotic as nitrogen but clearly it is not!

Yes indeed, Trimix sounds like a good idea to me!

 

[O-ring]

I for one do not include oxygen when calculating END

I have nothing to worry about on an EANx30 dive to 115 fsw.

 

[VTWarrenG]

Dr. Paul Thomas,

As I said, oxygen is probably not as narcotic as nitrogen. However, if you're a stickler for safety, calling it as narcotic as nitrogen is akin to rounding towards safety. There's certainly no harm done in overestimating its narcotic qualities.

O-ring,

You're "probably" right. A dive to 115 fsw on the 30% is not likely to cause you any significant impairment. I wouldn't worry about it, either.

However, when thinking about the inherent depth limitations of nitrox mixes, you have to draw a line in the sand somewhere -- the GUE folks happen to have drawn the line at 100 fsw. It doesn't mean something's going to happen to you if you descend below 100 fsw on nitrox. It just means that, given the choice, dives below 100 fsw should be conducted on trimix. Equivalently, given the choice, divers should not subject themselves to a narcotic potency greater than 4 ATA.

Many different organizations have drawn different lines in the sand -- at 130 fsw, at 200 fsw, you name it. None of these groups are inherently correct, especially considering that every person's narcotic susceptibility is different.

- Warren

 

[O-ring]

The line would be better drawn at 100' (using GUE guidelines) but these are not very practical for the average recreational NC wreck diver since many of the wrecks are in the 100' - 120' range. Most of the boats down there that I know of pump 30% and they have a good safety record.

I will be sure to ask JJ about it weekend after next at my DIRF class...I will let you know his thoughts.