Max optimal depth on air, narcosis related

[ptyx]

I've dived feeling fine at 150ft, and got one memorable narc at 100ft (tired + cold + nothing to see = narc - who would have guessed ?)

So rather than a depth limit, how do you figure out it's time to go up and get easy on the nitrogen?

The only consistent aspect I can think of for me is loss of short term memory (aka checking my gauge every 5 minutes) - but it can take a while before I realize that happens (duh!). No narc induced creeps or euphoria I can remember - and I'd rather not experiment. Does anyone have useful tricks?

 

[rjack321]

I understand that everyone is different and I also understand the fact that rec limit is 130' but I have heard many people saying having narc in a range of 110'

Narcosis is a continuum and its basically starting at the surface. At 20ft its barely noticable. At 50ft its preset but still fairly innoculous. At 80ft its getting noticable if you are presented with a novel problem to solve (not something you've done or seen before, so math doesn't qualify). At 100ft narcosis is definitely present but still generally acceptable if there's a clear plan you're following. By 130ft narcosis is becoming more and more prevalent, but the proportional change in ATAs is actually declining so its not hugely different than 100ish. And onwards down to 150-200ft. despite all discussions to the contrary there isn't "one number".

BTW the NTSC recreational depth limit of 130ft is more based on no deco time (~5mins) than narcosis. Some agencies extend a little deeper and teach rudimentary deco as "recreational" I think CMAS and BSAC into this category.

 

[Jeff Toorish]

I can tell you, without question, you get narced on air at 180 feet.

Jeff

 

[gcbryan]

For me DA Aquamaster summed it up best and in a way that fit's more with my experience/understanding...

(for full context the thread is here:
http://www.scubaboard.com/forums/ma...-my-buddy-claims-he-not-narced-135-45m-3.html)

To be honest, I don't disagree with you. When I used to do frequent deep air dives to 150' or so with much less diving over the winter, I'd notice improvement early in the spring and summer. I would also work up to deep diving with dives to progessively deeper depths over a few weeks time.

However, I got tired of getting flamed here for suggesting that divers can develop tolerance by all the divers who apparently do not develop any degree of tolerance. And if you hint at THAT, you get flamed again.

Personally I think it is a mix of the four major factors:

1. Experience - to reduce task loading through familiarity with normal tasks.
2. Differences in inital functioning levels and susceptibility - some divers can afford to lose more than others and some are less noticeably affected than others.
3. Recency of expereince at depth (tolerance), and
4. Psychological expectations regarding narcosis - if you have been trained or indoctrinated to believe you will be debilitated by narcosis at fairly shallow depths, you will be.

The last one will also get you flamed. There is some interesting research out there but it again gets discredited even though the methodology was pretty sound.

 

[Diver0001]

I have a question to those who did many dives past 100' and observe others at those depth. According to your experience what would be the max depth on air you would suggest to set as a limit.

I guess if you want a suggestion then I'd suggest making some dives to 100+ and see what feels right for you. Narcosis is one of those things that some people just tolerate better than others so everyone's limit will probably be different and even your own limit will change somewhat from day to day

In my case, I function pretty much normally up to about 120 most of the time. After that my performance starts to drop. At 165 I'm generally pretty narced on air so I better be doing something that isn't too complicated.

What makes a big difference to how deep I start to feel it seems to be how well I slept the night before the dive.

R..

 

[elan]

Narcosis is a continuum and its basically starting at the surface.

Some people do not even get out of that state

 

[HowardE]

I have a question to those who did many dives past 100' and observe others at those depth. According to your experience what would be the max depth on air you would suggest to set as a limit. So far I have not been below 100' though did dives in 90' range in cold water. I was able to do math calculations fairly quick so I think I was not narced.

Would it be wise to limit the depth to 100' and just get the training for using HE mixes if necessity to go past 100' arises (like diving Arabia @ Tobermory). The depth is not interesting for me now. Most of the time so far I tend to work on my skills at this time but do not forget about the fun part.

Thanks a lot.

I have been to 200 feet on Air. I could certainly feel the effects of narcosis at around 150-160 feet on other dives to those intermediately deep ranges. However, for me at least. They were not debilitating, nor were things kooky crazy. At 160 feet, I could feel "tingly" and buzzed. I could feel the effects of the tunnel vision beginning to set in, and I could feel the sound of my breathing beginning to reverberate a little in my head.

At 200 feet. I could definitely feel the narcosis. For me, it wasn't the feeling I had in my head when I would go see the Grateful Dead, but it was definitely strong narcosis. It was similar to the feeling of being in the dentist's chair with some nitrous oxide. I wasn't out of my head, and I do have clear recollections of the reef and details of my dive. I was with my instructor at the time, and he gave me math problems to complete, and fill in the blank questions with letters and numbers. While I did have to think about the task at hand more than I would on the surface, I was able to complete the math, and other skills. I will say that 200 feet is certainly a doable thing on air, but with the availability of helium in the mix, why do it; unless you are wanting the experience. I only spent about 10 minutes on the bottom on my 200 foot air dives (yeah more than one) and I would do it again, in the right conditions, but not for a prolonged dive, or a wreck penetration.

However; as stated... Narcosis effects different people differently, and your mileage may vary.

 

[Nemrod]

I think people confuse narcosis with anxiety. N

 

[SailNaked]

Very useful thread and great posts, as a summary it seems narcosis = Drinking.
you can get used to it, some think it is manly to do lots of it, better to do at home in a safe environment, a little is fun a lot is sometimes not,even a little you are still effected, dont do it and drive (task load).

 

[muddiver]

For me DA Aquamaster summed it up best and in a way that fit's more with my experience/understanding...

(for full context the thread is here:
http://www.scubaboard.com/forums/ma...-my-buddy-claims-he-not-narced-135-45m-3.html)

To be honest, I don't disagree with you. When I used to do frequent deep air dives to 150' or so with much less diving over the winter, I'd notice improvement early in the spring and summer. I would also work up to deep diving with dives to progessively deeper depths over a few weeks time.

However, I got tired of getting flamed here for suggesting that divers can develop tolerance by all the divers who apparently do not develop any degree of tolerance. And if you hint at THAT, you get flamed again.

Personally I think it is a mix of the four major factors:

1. Experience - to reduce task loading through familiarity with normal tasks.
2. Differences in inital functioning levels and susceptibility - some divers can afford to lose more than others and some are less noticeably affected than others.
3. Recency of expereince at depth (tolerance), and
4. Psychological expectations regarding narcosis - if you have been trained or indoctrinated to believe you will be debilitated by narcosis at fairly shallow depths, you will be.

The last one will also get you flamed. There is some interesting research out there but it again gets discredited even though the methodology was pretty sound.

You have some good points and you have stated nothing you should get flamed for. I have done working scientific diving to 170' and I remember the dive quite well. I was not impared to the point that I was not functioning and I helped perform the project successfully.