Narcosis - How does it work?

[AndyNZ]

I was under the impression that it was more relative and there is not really a cut-off depth at which the increased partial pressure of the Nitrogen becomes narcotic... Anyone know?

Empirically, I'd have to agree that it's not a cut-off depth. I've noticed myself becomming increasing narc'd with depth - there's a point where it's quite a nice feeling, then a little bit concerned, then beyond a certain depth I become paranoid and things get ugly....

It's also something that varies with time, recent diving history and physiology. For example, a couple of months ago I was only diving on OW courses, so rarely got deeper than 12m for about 6 weeks. on my first pleasure dive I started noticing that I was a bit narc'd much shallower than normal - around 25m as opposed to where I normally notice it at around 32m. By the time I got to 30m, I was Mr Paranoid Freak which normally doesn't get me until pushing 40m.

It also varies from individual to individual, so I guess the actual physiological mechanisms aare going to be more complex than we beleive!

 

[DivingCRNA]

We do know what inhalation anesthetics do. Miller's "Anesthesia", one of the premiere anesthesia texts, has an entire chapter devoted to the subject. It is very complicated, but understandable with the right background.

It basically comes down to effects on brain chemistry and neuronal conduction. Alcohol works in the same way. I do not know it for a fact, but I experience and intuition tell me that nitrogen acts in the same fashion at the right pressure. I have read that one can use CO2 to conduct a general anesthetic, but I would not advise it.

I do not mean to sound like a know it all. I really do think that this adds to the discussion.

What you guys may find interesting is that we don't even really know how the anesthetic gases we use in the operating room work at a cellular level. We know what they DO, but not how they do it. Same thing for the narcotic properties of nitrogen.

 

[Snowbear]

Empirically, I'd have to agree that it's not a cut-off depth. I've noticed myself becomming increasing narc'd with depth - there's a point where it's quite a nice feeling, then a little bit concerned, then beyond a certain depth I become paranoid and things get ugly....

I agree with you here. If I'm completely relaxed and paying attention, I can start feeling the effects of narcosis as shallow as 40-45'. If I'm stressed or just not paying attention to how my body/brain is feeling, I can dive to 110+ without noticing I'm narced.

I've posted about it before, but one of the best narcosis lessons I learned was the first time I did a trimix dive and switched to a deco gas.... It was a training dive where we dove 30/30 to ~ 110'. We did our deco dive as planned and on the ascent switched to EAN 50 at 70'. The first breath of the nitrox after being clear-headed on trimix hit me like.... uh..... well... like the bong hits I did back when I did those things :blush:

It took a few more breaths to adapt and re-orient... but the point is, the lesson to me was that once you start increasing the PPN2, you start increasing the narcotic effects of that nitrogen, whether you realize it or not....

 

[WarmWaterDiver]

HAHAHA Snowbear - now you've given me a REAL reason / perspective to maybe some day get Trimix certified - for the switch to deco gas!!! I've worked under DOT compliance testing protocols for 20+ years now - but I also remember earlier times:14: . These days, they take a 2 inch lock of hair and the test instruments supposedly give a 3 month history - our college interns have to behave during their campus semesters as well as their work semesters!

I've noticed narcosis on a few of my dives but not many, and depth was greater in some than others. My AOW class was in the coldest water I have dived so far (high 50's / low 60's) and they had me add two different sets of six digit numbers - once on the surface before the deep dive, once at depth, and I took 3 seconds on the surface and 4 seconds at depth. The times I've noted it have been on my more typical caribbean bathtub-warm water dives - which comprises over 90% of my dive history so that's maybe not too surprising. It's just that even day to day as individuals the suceptibility varies, or the percieved impact anyway.

 

[Bubble Twin One]

I agree with Catherine that you can get Narc'd on many different dives at different depths. I got Narc'd in the Blue Hole. After having a bad Narc experience I seem to be more susceptible to it. On several dives after the Blue Hole I experienced similar symptoms. I'm not sure if it was anxiety about getting Narc'd or actual NN. For me the symptoms feel similar. Anyone else experience this? Any way to prevent NN?

 

[MoonWrasse]

I agree with Catherine that you can get Narc'd on many different dives at different depths. I got Narc'd in the Blue Hole. After having a bad Narc experience I seem to be more susceptible to it. On several dives after the Blue Hole I experienced similar symptoms. I'm not sure if it was anxiety about getting Narc'd or actual NN. For me the symptoms feel similar. Anyone else experience this? Any way to prevent NN?

Sure. Watch your depth.

 

[TSandM]

I'll have to pick up a copy of that text at some point and read what they have to say. The last stuff I read still didn't know exactly what anesthetics were doing at a cellular level.

I was actually thinking about this the other day . . . thinking about why very simple actions are excessive task-loading underwater, and thinking about why I've failed to follow very simple sets of directions once I'm submerged. I suspect narcosis is really a continuum, and the place where you RECOGNIZE it is the place where you can no longer do what you are accustomed to doing easily.

 

[Rick Inman]

I agree with you here. If I'm completely relaxed and paying attention, I can start feeling the effects of narcosis as shallow as 40-45'. If I'm stressed or just not paying attention to how my body/brain is feeling, I can dive to 110+ without noticing I'm narced.

I've posted about it before, but one of the best narcosis lessons I learned was the first time I did a trimix dive and switched to a deco gas.... It was a training dive where we dove 30/30 to ~ 110'. We did our deco dive as planned and on the ascent switched to EAN 50 at 70'. The first breath of the nitrox after being clear-headed on trimix hit me like.... uh..... well... like the bong hits I did back when I did those things :blush:

It took a few more breaths to adapt and re-orient... but the point is, the lesson to me was that once you start increasing the PPN2, you start increasing the narcotic effects of that nitrogen, whether you realize it or not....

Often times, if it's dark and especially if it's a new site, at about 100' I get this major sense of impending doom. At about 110'-115' it totally goes away and I feel absolutely great, narcosis gone.

OK, I know it's not really gone, it's actually worse. But it feels like it's gone.

I did a dive Sunday where the plan was to switch from EAN34 to some 30/30 at 100'. I was very comfortable and very familiar with the site. I needed to find this small boat that I can usually hit about 50% of the time. But this time it was important that I find it so we could recover some stuff my buddy left down there on a prior dive (long story). Anyway, I was swimming around at 95' feeling the pressure to find the boat, thinking at one point that I had missed it, but not feeling narked at all. And then I found it, and I was elated! Ya-hoo! What a great job I had done!

I switched over to the 30/30 and suddenly my elation was gone. Maybe I wasn't such a big deal after all.

Good lesson for me.

Funny what a little depth will do to you...

 

[Cacia]

I have only had the good narc never the bad one. (I have had vertigo or fear) but the narcosis I get is a drug high, no mistake about it. My most profound experience was in Palau. I was griping about not getting to shoot macro, blah, blah so finally I got everybody (the tank rappers) to leave me on a wall. No current and I was at only 50 ft or so for like...a long time. Happy as a clam, totally convinced this one Damsel fish loved me and was following me. Well, something strikes me from the back and its my BF. He had freedove down to get me, everyone was waiting on the boat. He needed air so he grabbed my alt (pre-long hose days) and just sat there glaring at me. I was looking at him, but I did not really recognize him. I hauled off and hit him. He starts rapping on his watch. (meaning time, time, time.) 70 mins. And I just looked at him, a foot from my face and had no idea who he was. I was not scared until later, thinking back about it.....I get very goofy down there and I need to be aware of this. I think I like the high too much. I might add that I do not use drugs, so....not sure what it means other than I find it very pleasant and it is a major factor why I dive. Every pre-dive, I have a little "talk" with myself. At about 90, I am aware that I am deep. At 120, I would willingly follow anything deeper and need to be in a group.