NITROX for any and all dives?

[Cowfish Aesthetic]

Hello again.



I know this was a tongue-in-cheek comment but I did not say that. If you go back a couple of posts I said that we have just embarked on a substantial research project to see if oxygen is less narcotic than nitrogen. I think that is a fairly unambiguous admission that we don't know. My point was that Storker's basis for believing that oxygen might be less narcotic is valid. And it is valid.

You are misinterpreting oxygen physiology and the best path to enlightenment here may be to google some basic accounts of oxygen delivery to tissues. Maybe start with the term "oxygen cascade". You will find lots of diagrams like this one:

View attachment 452494

It clearly illustrates that there is a big fall in PO2 from arterial blood to cells in tissue. This still holds even when we breathe high inspired PO2s because increasing the inspired PO2 does not actually increase the carriage of oxygen on hemoglobin much (it is already 97-100% saturated with oxygen when we breathe air) and the solubility of oxygen in the plasma is low. Thus, within the range of PO2s we see in diving there will always be a gradient from arterial blood to tissues like the one you see in the diagram (in fact, the gradient gets even bigger at high PO2s - which is part of the explanation of the so-called oxygen window). In contrast, if you drew a line for nitrogen in the brain on that diagram, after a short wash-in period there would be very little difference between the nitrogen in the alveoli and the tissue nitrogen. THAT is what Storker is saying.

Simon M

I have to say, your willingness to explain the complex science behind diving phenomena is consistently the thing I find most valuable about ScubaBoard.

 

[Storker]

My point was that Storker's basis for believing that oxygen might be less narcotic is valid.

Just a minor nitpick: Storker has no belief in that matter, he just has heard the argument put forward and thinks that the argument is plausible. However given the complete lack of anything but plausible speculation, he still treats oxygen as just as narcotic as nitrogen.

He is, however, looking forward to seeing experimental data on the subject and hopes that they will appear in about three to five years' time.

 

[RayfromTX]

It seems to be very subjective and the discussions and testing to date seem to indicate what divers would guess by they’re experiences which for me is that the difference between the Narc on air or Nitrox if it exists, is kinda lost in the noise. How much difference would it have to be to notice when many divers can’t even recognize that they are narced in the first place.

 

[boulderjohn]

It seems to be very subjective and the discussions and testing to date seem to indicate what divers would guess by they’re experiences which for me is that the difference between the Narc on air or Nitrox if it exists, is kinda lost in the noise. How much difference would it have to be to notice when many divers can’t even recognize that they are narced in the first place.

Narcosis tests in the past have usually been done by having people perform tasks under different conditions.

 

[Dr Simon Mitchell]

How much difference would it have to be to notice when many divers can’t even recognize that they are narced in the first place.

Yes.

That is exactly why we are trying to develop an objective outcome measure based on qEEG. No opinion from the diver, and no need for tests (although we will probably do these as well).

Simon M

 

[RayfromTX]

Narcosis tests in the past have usually been done by having people perform tasks under different conditions.

I understand and have read one of the tests. The difference was in the milliseconds as I recall and higher but still slight during the initial ascent. My point is that in such a fuzzy perceptual experience the difference may be similar to the difference between a blood alcohol level of .2 and .21. It may not be perceiveable and that small difference may not be the most important factor in determining safety. If it is an issue, Nitrox is not going to get you to a place where you are unimpaired. I suspect a small but insignificant difference depending on your definition.