The Meyer-Overton Rule is not neccesarily accurate. All it does is list the solubility of gasses in olive oil!
Seeing as most things that are narcotic are also toxic and O2 can also be toxic at relatively low pressures, I would expect some of the O2 narcosis to be realted to it's toxicity as well as lipid solubility. However, this is nothing but utter speculation as I have absolutely no medical training whatsoever (well, PADI MFA .:bonk
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I just want to add something here that there is some decompression softwear ask u if u are planning a deco dive if u want the O2 to be narcotic or not
..i think after that the END should change
Wazza, I wrote a post on another board regarding the difference between EAD and END... here it is...
How to calculate your EAD and END.
EAD stands for Equivalent Air Depth, which basically means 'If I am breathing a gas mix at a certain depth, what depth would I have to be at breathing air to have the same partial pressure of nitrogen'. This is useful for using Air tables when breathing nitrox and for getting an idea of the narcosis you may experience if you do not believe O2 to be narcotic.
END stands for Equivalent Narcotic Depth. This means 'If I am breathing a mix at a certain depth, what would be the equivalent depth I would have to be at breathing air to experience the same level of narcosis'. If you do not consider oxygen to be narcotic then this is the same as EAD. If you do consider O2 to be narcotic (which I do), then every nitrox mix has the same potential for narcosis.
There are several formulas out there to calculate EAD, but most are all overly complicated or differ depending on whether they are for metric or imperial. In my opinion anyone who dives nitrox regularily should be able to work in atomspheres (they needed to to get certified), so why complicate it? The easiest way to do it is to use the 'triangle' which represents Dalton's Law (as you should have been taught on your nitrox course)
i.e.
Pg
-----
fg | P
Which, to recap, means
Pg (partial pressure of a gas) = fg (fraction of a gas) * P (pressure in Ata)
fg = Pg / P
P = Pg / fg
P is the same as depth (it is not the depth we are worried about per se, but the pressure caused by being at that depth)
So using EAN25 at a depth of 40M as an example.
fg = 0.75 [1 (the complete mix) - 0.25 (fraction of O2) = 0.75 (fraction of N2)]
P = 5 [40M = (40/10)+1 = 5 ata]
Pg = 0.75 * 5 = 3.75
So the partial pressure of nitrogen when breathing EAN25 @ 40M is 3.75 ata.
To find out the EAD, we use Daltons Law again:
Pg = 3.75 (PP from above)
fg = 0.79 (fraction of nitrogen in air)
P = 3.75/0.79 = 4.746835443 ata or (4.75-1)*10 = 37.5M
Expressed in one formula:
EAD(ata) = [fN2 * Depth(ata)]/0.79
