I'm referring to the lipid solubility of O2 relative to other inert gases. I understand that O2 is not "inert", and I am aware that Meyer-Overton addresses inert gases only. I am also aware that there are no conclusive scientific studies that support the relative narcotic potential of Oxygen as compared to other inert gases that are used in diving. That is why I was very careful to state that it is "theoretical" and that "in my opinion" it is most prudent to treat O2 as being at least as narcotic as N2.
This is based on my own personal observations, as well as the conclusions and observations of many divers whose opinions I hold in extremely high regard. I have never personally experienced a tox episode, but I have been narced plenty of times (both on air as well as on Nitrox), and my belief (based on my personal experience) is that Oxygen contributes to narcosis in a significant and measurable way. This belief has increased as a result of my transition to helium-based mixtures over the last few years (and in particular on logistically complex dives in the ~100 foot range that I had previously done on Nitrox).
Maybe your experience has been different, and you are certainly free to believe what you want about Oxygen narcosis. I'm just calling it like I see it.
As an ANDI IT, let me explain ANDI's position.. Overall ANDI believes Increasing the Oxygen and decreasing the Nitrogen reduces narcosis.. The BIG BUT!.. Some CNS sysmptoms are the same as nitrogen narcosis..
Personally I believe (and have ways to show it).. That increasing the oxygen reduces the narcosis by reducing the nitrogen.. I am not saying o2 is not narcotic at all but its significantly less..
This is a drill I do with my Technical Rebreather students when condtitons permit (due to the nature of this drill myself and any assistents are on a mix with a shallow END and have less narcotic gas to give the student should we need to clear up their heads quickly..) we do approximately a 45m dive, when at the bottom we allow the po2 to drop to around between .7ata to 1.0ata.. The person usually has a very strong narc.. now I have the student brings the po2 up quickly to a 1.4.. Virtually EVERY student has reported exactly the same.. The perceived narcosis level was reduced significantly and very rapidly.. The excercises that I have them do also are completed faster and in better control.. There have been a few students that I had to do this a bit deeper for them to see a big change (these are divers that are used to doing air dives in the 45-50m range)
My personal feeling due to obeservations is that the reason that some nitrox divers say they have increased narcosis is that many divers have poor breathing patterns and the higher po2 on some of these diver tends to allow them to strech out breathing cycles (especially co2 retainers), therefore retaining much more co2 which is HIGHLY narcotic (plus it is a prime catalyst for oxygen toxicity)..
Another thing to consider is that as depth increases so does the density of the breathing gas, and your ventillation efficiecy decreases, so its important that all your regulators are properly adjusted for ease of breathing.. Helium lowers a regs WOB, but there is acecdiodal evidence that it also raises the risk of oxygen toxicity..
ANDI's position is that if the po2 is at a level where it Might be a cns issue treat it as such.. CNS can hurt you quickly, where narcosis will probably just make you do something stupid..
There is evidence that high pn2 levels reduce the liklihod of oxygen toxicity.. All that one needs to do is look at alot of the old deep air records and dives that were done.. There were no reported serious cns issues at these very high po2s, but people on helium based gases have had issues with much lower po2s..
In my young stupid days (before He was easily availble) I had many dives with po2s in the 1.7 to 2.0 on the bottom (with a few significantly deeper than this) without ANY CNS issues whatsover..
