Nitrogen Narcosis, what's up with that?

[MXGratefulDiver]

Here's an experiment I tried once a few years back. Take two buddies, one diving air the other diving a mix with 20-25% helium in it. Dive down to 120-130 feet. Swap regs and take a few breaths. See if you notice any difference. I certainly did. It really brought home how muddle-headed you really are on air at that depth ...

... Bob (Grateful Diver)

 

[Akimbo]

Interesting, I never perceived significant impairment down to the 130-140' range. I have switched from HeO2 to air and back several times at ~160' and didn’t notice much change. We were doing some pretty complex work that required problem solving. However, we had spent a lot of time at that depth on air during that month. I can say that narcosis was noticeable on my first few jumps on air at the start of the project though. I don’t think I am exceptional since the people I worked with over the years were about the same. Experience with narcosis is an important factor in performance.

A means of measuring performance can be photographic evidence. The problem is my exposures and focus were about the same when deep and my artistic sensibilities sucked just as bad as when I am standing on a mountain. Conclusion, I’m no artist but can manage narcosis doing familiar tasks.

 

[Bob DBF]

I have not seen studies that confirm or deny the phenomenon but nearly all commercial divers and supervisors I have spoken with believe repeated short-term deep air exposure increases narcosis tolerance and improves performance. Most people I have spoken with think that nitrogen narcosis is quite different than being impaired by alcohol. Mental and physical control under narcosis is much better.

I can see how narcosis can be much worse if you have never experienced it and it sneaks up on you. It is a shame that chambers are so expensive to operate because it is such a safe way to learn about it.

I keep narcosis from sneaking up on me by assuming I am narked at 100'. I keep myself on a short leash, so to speak, from that point on.

As for repeated short-term deep air exposure increases narcosis tolerance and improves performance, my experience has been the same. After repeated recent dives to 110 to 150' I went from functioning at a survival level (tracking gas, NDL, buoyancy, and deciding to head up whenever anything "felt" wrong) to adding navigating, running line, mapping, performing other tasks, and remembering more about the dive after the fact. I found, for myself, that more task loading can be accomplished however, when anything goes wrong I have to consciously focus more on survival skills and not get sucked into the problem, it can be fixed next dive.

A couple of years ago I dove Lake Tahoe late one afternoon and followed the beautiful blue water down to 150' before heading up. My plan was to dive to 120 or so and meander back up, I knew I passed my plan but it was so pretty [-]almost[/-] and mesmerizing, I checked my air and NDL then set 150 as my new limit and had the discipline to head back. If I was not observant and familiar with narcosis I could have followed the feeling to the bottom, some have.




Bob
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"the future is uncertain and the end is always near"
Jim Morrison

That's my point, people, by and large, are not taught that diving can be deadly, they are taught how safe it is, and they are not equipped with the skills, taught and trained to the level required to be useful in an emergency.

 

[boulderjohn]

Here's an experiment I tried once a few years back. Take two buddies, one diving air the other diving a mix with 20-25% helium in it. Dive down to 120-130 feet. Swap regs and take a few breaths. See if you notice any difference. I certainly did. It really brought home how muddle-headed you really are on air at that depth ...

And that shows the difference between individuals. I did the same thing at about 160 feet. I was breathing 21/35 (21% O2, 35% He, and 44% N2). My buddy was breathing air (79% N2). He said he felt a big difference. I didn't notice a darn thing.

 

[RJP]

I was never cognizant of any narcotic effects - negative or positive - as deep as 170fsw... until the first time I dived TMX.

 

[Drin]

And that shows the difference between individuals. I did the same thing at about 160 feet. I was breathing 21/35 (21% O2, 35% He, and 44% N2). My buddy was breathing air (79% N2). He said he felt a big difference. I didn't notice a darn thing.

Divers don't on-gas so quickly that we saturate our tissues in 3 or 4 breaths, and I believe the narcotic effect of nitrogen is thought to occur because of accumulation reaching a threshold PPN2.

I personally suspect it takes more than a few breaths of a different gas for the effect to be noticeable.

-Adrian

 

[dumpsterDiver]

Divers don't on-gas so quickly that we saturate our tissues in 3 or 4 breaths, and I believe the narcotic effect of nitrogen is thought to occur because of accumulation reaching a threshold PPN2.

I personally suspect it takes more than a few breaths of a different gas for the effect to be noticeable.

-Adrian

then why would narcosis effects be associated with very rapid descents?

 

[Drin]

then why would narcosis effects be associated with very rapid descents?

It's interesting. There's evidence on both sides. On the one hand a rapid pressure increase has been shown to aggravate the effects of narcosis in some individuals. On the other, rapid descents crush bubble micronuclei and that has been shown to decrease the effects of narcosis in some individuals. Note the "some" in there. Our individual physiologies contribute in varying degrees to our narcosis, as do environmental factors. That's why it's so difficult to replicate studies - how you respond to the same PPN2 level tomorrow at the same depth will probably not be the same as how you respond today.

The bottom line, I think, is that it's a crapshoot all round. We all get narced at some level, with some partial pressure of nitrogen, for some period of time, and while we may be able to learn to work through that narcosis I don't think we acclimate to it and lessen it over time. Just my opinion though...

Don't want to get narced? Don't dive...

-Adrian

 

[Adventure-Ocean]

Nothing I've experienced felt anything like nitrogen narcosis. For me, I was always in warm, clear water. I don't think I can describe what I felt like only to say it felt good. Adventure-Ocean

 

[Dr. Lecter]

I start to feel the wet blanket settling onto my brain around 150-160', and found rapidly descending down a steep slope from 50' or so to 200' made it easy to recognize and assess the evolution of the impairment. Most days, I enjoy the 'heavy head' feeling of having critical thinking become something that requires a good bit of conscious focus. Other days, I don't feel anything at all when I know I'm narced given the depth and I feel a bit annoyed I'm both (1) not getting to enjoy the buzz at depth and (2) having to watch myself extra carefully because I may just be really narced.