There is no evidence that O2 is narcotic at recreational diving depths.
O2 in a chamber at 2.8 pPO2 produces no narcosis.
The study states "In this pilot study 3, 3 and 4 subjects were studied at 6, 8.5 and 11 bar respectively..."
I have yet to read the study, but it seems to me they are talking well above recreational diving depth.
Now, if O2 were narcotic at 100 feet/30 meters (no evidence of this exist that I know of), then arguably one could use Trimix for a 100 foot cave dive.
Personally, I find increasing O2 and decreasing N significantly reduces narcosis in the 24 to 30 meters range in cave diving.
What I find odd is that Carlos allegedly carried from Canada an Alu80 bottle of Air (marked as O2...), when he also carried back-mount bottles of N30.
Air is cheap and it would have been easy enough for him if he wanted more gas to empty the Alu80 and fill it with the same gas he had in his back-mount (i.e. N30 which was quite suitable for the diving he intended to do).
Instead, he had an O2 bottle actually filled with O2 which we know he breathed at depth.
---------- Post added August 26th, 2013 at 02:58 PM ----------
Is this for cave diving (and can you cite as an example which agencies adopt this standard)?