Nitrox & Narcosis (again)

[TSandM]

<note - this thread is a split from a thread on deeper diving - Rick>

I, at least, was taught in my Nitrox class that Nitrox does NOT affect narcosis. And what was probably the worst narcosis I've had was on 32%.

 

[SparticleBrane]

I, at least, was taught in my Nitrox class that Nitrox does NOT affect narcosis. And what was probably the worst narcosis I've had was on 32%.

<thread hijack>
I was under the impression that one of the main functions of Nitrox is that by increasing the amount of oxygen in the mix (ie 32% instead of 20.9%) then the amount of nitrogen in the mixture is decreased (from ~78-79% to ~68%). This therefore means that at the same depth one is actually ingassing less nitrogen if they are using nitrox, thus resulting in lessened narcosis. Many people are still debating this, and lots of people say that oxgen itself is narcotic so that increasing oxygen in the mix you still get narc'd.
In my (small) experience you can calculate an "equivalent air depth" from which to work your dive tables, if you're using air tables and not nitrox tables. Also, it is this EAD of which I'm basing my claim. My last open water dive was on the wreck of the Caribsea off the coast of NC with a max depth of 87ft using 32%. At 87ft I was ingassing the equivalent amount of nitrogen as if I were diving ~70ft on air. Thus, at 87ft on 32% I was experiencing the narcotic effects of air at 70ft. So, you still get narc'd, but you get narc'd less at depth. Just make sure you don't get too deep and get oxygen toxicity...

I try to dive exclusively nitrox when I'm out in open water, and make sure that I have the highest percentage of oxygen in my mix that is possible for the dive (making sure that at my max depth I'll have no more than 1.4ata). If I don't feel like making a special blend then I use 32% and make sure that the dive won't be any deeper than 111ft.


...then again I could be wrong. Sometimes it's hard to tell who to trust these days with xyz claim about nitrox.
</thread hijack>
Please continue with your normally scheduled thread.

As a note to scubasherry--just make sure that no matter what or how you're diving, it's fun and enjoyable.

 

[Kevrumbo]

Yeah Scubasherry --Diving is Fun! But like others have said, you can thumb the dive whenever you need to. If it feels wrong, then it is wrong . . .ascend to your Safety Stop and surface if need be.

<thread hijack>
I was under the impression that one of the main functions of Nitrox is that by increasing the amount of oxygen in the mix (ie 32% instead of 20.9%) then the amount of nitrogen in the mixture is decreased (from ~78-79% to ~68%). This therefore means that at the same depth one is actually ingassing less nitrogen if they are using nitrox, thus resulting in lessened narcosis. Many people are still debating this, and lots of people say that oxgen itself is narcotic so that increasing oxygen in the mix you still get narc'd.
In my (small) experience you can calculate an "equivalent air depth" from which to work your dive tables, if you're using air tables and not nitrox tables. Also, it is this EAD of which I'm basing my claim. My last open water dive was on the wreck of the Caribsea off the coast of NC with a max depth of 87ft using 32%. At 87ft I was ingassing the equivalent amount of nitrogen as if I were diving ~70ft on air. Thus, at 87ft on 32% I was experiencing the narcotic effects of air at 70ft. So, you still get narc'd, but you get narc'd less at depth. Just make sure you don't get too deep and get oxygen toxicity...

I try to dive exclusively nitrox when I'm out in open water, and make sure that I have the highest percentage of oxygen in my mix that is possible for the dive (making sure that at my max depth I'll have no more than 1.4ata). If I don't feel like making a special blend then I use 32% and make sure that the dive won't be any deeper than 111ft.


...then again I could be wrong. Sometimes it's hard to tell who to trust these days with xyz claim about nitrox.
</thread hijack>
Please continue with your normally scheduled thread.

As a note to scubasherry--just make sure that no matter what or how you're diving, it's fun and enjoyable.

<address hijack>
You know, I used to have the same impression too, all things being equal. But there is one big confounding variable here and that's CO2 Build-up & Retention and its role in Deep Air Narcosis (if someone is thinks I've been preaching a Religion here, well this is what I've been harping on SB for the past couple of weeks --My CO2 Epiphany if you will ). This post was a Revelation to me: http://www.scubaboard.com/showpost.php?p=248750&postcount=56
<end hijack>

 

[Rick Murchison]

ingassing less nitrogen if they are using nitrox, thus resulting in lessened narcosis

You are a victim of the misnomer we used for years and years (and many still do) "Nitrogen Narcosis."
Problem is, the term isn't accurate, as oxygen is also narcotic, and a more accurate term is probably "compressed gas narcosis." Indeed, by the lipid solubility standard, oxygen should be about twice as narcotic as nitrogen - but as oxygen is a reactive gas carried by active combination in - and scavenged by - hemoglobin, and metabolized, its brain tissue level titre is much lower than it would be if it were an inert gas.
What's the bottom line?
I like the SSI book's statement: "It is best not to assume any reduced narcosis from nitrox use."
Rick