Enriched Air

[Guy Alcala]

I emboldened the most important part of your entire post. Nitrogen Narcosis is a silent killer: you very rarely feel it's onset. I can guarantee that if you are below 80 fsw, you are impaired. You may not know it, you may even vehemently deny it, but you are impaired.

I phrased that sentence very carefully, precisely because I anticipated such comments from someone.


That doesn't mean you can't dive safely to 130 or even deeper. Planning, forethought, contingencies and bail out should be done ahead of time. Turn times, pressures and depths should be written down and adhered to. All of us think we are the exception and that's just plain denial mixed with hubris. You can manage narcosis to a degree, but you can never eliminate it.

Yes, and that's my point; I was able to operate with acceptable levels of performance at that depth on air, in those conditions on those days. Blithely saying "Hey, I've never done this before, let's give it a shot; no worries" isn't my style.


From my experience, it is a mood/character amplifier. The timid become frightful, the confident become arrogant, the apathetic become morbidly so.

So, what happens to those of us who are naturally cautious about establishing and approaching our limits, and meticulous in observing them? In the cases mentioned, I was able to correctly record the details of my position (depth, time, PSI, temp, something which I do routinely throughout all dives on my wrist slate), check my buddy (whom I'd told to hold 10 feet above and monitor me while I did my narc checks and basic housekeeping chores), look around at the surrounding fish, etc. I was not euphoric, frightened, arrogant or apathetic, just interested in observing how I was functioning under the conditions. That's my normal tendency at moments of physiological stress; I like to see how the machine that is my body is working.

Now, I have had scattered instances (at shallower depths) where I have recorded individual pieces of data that were manifestly wrong upon later examination. Whether that was due to narcosis or just momentary brain farts I can't say.


That's why so few feel it. But everyone that I have tested has suffered from perceptual narrowing. You focus so intently on one task that you lose your situational awareness.

To date that hasn't happened to me. I'm sure it will at some depth; that's why I'm trying to establish, under semi-controlled conditions, when and how narcosis tends to affect me.


The most dangerous diver is the one who denies they are narced. The most foolish diver is the one who follows him.

Agreed. But I think it's also useful (if not essential) to establish how well you as an individual respond to being narc'ed, at what depth(s), how well you can deal with it and how well your buddies perform likewise. Personally, I'm more worried about Oxtox as the _primary_ limiting safety factor for my dives, since its onset may come with zero warning.

Guy

 

[Guy Alcala]

In an alcohol safety lecture way back when, I remember a police officer quoting a saying that has stuck with me ever since: "The person LEAST able to tell if he's intoxicated is the one who's drunk." There's a bit of poetic license in that, but if someone's intellectual capacity is somehow impaired, it's not unreasonable to assume that their capacity to use the same abilities to recognize that impairment may also be somewhat decreased. And that probably applies to narcosis as much as it does to alcohol, even if the details may be slightly different.

Certainly, which is why I always have another diver along who's been to the depths in question safely on numerous occasions, to monitor me from higher up when I'm doing such test dives. Ideally they would video me as well, but I'd rather have them not worrying about dealing with extra equipment if I start to do something stupid and they have to intervene. In any case, I think we've drifted rather far from a discussion appropriate for Basic Scuba, so maybe we should end it or move it to a more suitable forum.

Guy

 

[DCBC]

Agreed. But I think it's also useful (if not essential) to establish how well you as an individual respond to being narc'ed, at what depth(s), how well you can deal with it and how well your buddies perform likewise. Personally, I'm more worried about Oxtox as the _primary_ limiting safety factor for my dives, since its onset may come with zero warning.

Hi Guy, I agree with Oxtox; it happens without warning. Many divers push PPO2 too far with no idea what their O2 tolerance is.

The only place that it's safe to establish how well anyone responds to narcosis is in a decompression chamber. Many decompression facilities take tours of divers on "air dives" for this purpose. Obviously this doesn't present an accurate picture, as variables such as diver motivation, experience (learning to cope), ability to concentrate, age, training, temperature and individual variances come into play. It does however give you an idea of what you're dealing with.

 

[Guy Alcala]

Hi Guy, I agree with Oxtox; it happens without warning. Many divers push PPO2 too far with no idea what their O2 tolerance is.

The only place that it's safe to establish how well anyone responds to narcosis is in a decompression chamber. Many decompression facilities take tours of divers on "air dives" for this purpose. Obviously this doesn't present an accurate picture, as variables such as diver motivation, experience (learning to cope), ability to concentrate, age, training, temperature and individual variances come into play. It does however give you an idea of what you're dealing with.

I'd love to take a chamber ride for the reason you mention, even though I recognize the difference between that and actual diving. However, my local chamber doesn't seem to offer them, or at least not for a reasonable price. They do 'tours', but that seems kind of pointless to me: "Look; it's a big tube with pipes, gauges and valves, a lock-out chamber, and someone to look at the gauges and operate the valves:shocked2:" Maybe if you were seriously claustrophobic it might be useful (or terrifying) to know what awaited you if you ever had to take a ride, but I don't have that problem -- I've slept in snow caves and bivy sacks that make a deco chamber look positively spacious.

Guy