Max optimal depth on air, narcosis related

[scubadiver888]

I don't remember if it was Diver or Dive Training magazine but one of them this month has a good article on narcosis.

 

[DOkie]

I think people confuse narcosis with anxiety. N

Never looked at it that way.

I think you have something there, but in the right circumstances I think anxiety contributes to narcosis (increased breathing, task overload, etc.)

 

[rjack321]

Some people do not even get out of that state

Yup, just look at some of the "bright" ideas posted on SB at 1ATA

 

[Nemrod]

The human mind is very suggestible, if you expect or anticipate a result the human mind often delivers. There are often suppressed fears, when you are alone, deep, dark, cold, anxious, and expecting a result (narcosis) your mind will comply and release the demons. The demons are your own manufacture but we have to have something to blame it on beyond ourselves so we choose Rapture of the Deep. We need demons. That doesn't mean that narcosis is not a real effect but I think it is often highly exaggerated, especially at moderate (less than 130ish feet) sport diver depths, for our own purposes, we need a demon, so our minds give us one.

N

 

[gcbryan]

The human mind is very suggestible, if you expect or anticipate a result the human mind often delivers. There are often suppressed fears, when you are alone, deep, dark, cold, anxious, and expecting a result (narcosis) your mind will comply and release the demons. The demons are your own manufacture but we have to have something to blame it on beyond ourselves so we choose Rapture of the Deep. We need demons. That doesn't mean that narcosis is not a real effect but I think it is often highly exaggerated, especially at moderate (less than 130ish feet) sport diver depths, for our own purposes, we need a demon, so our minds give us one.

N

I certainly agree with this. The way I look at it is that many times people use the term narcosis to refer to more than the actual narcosis without realizing that they are doing so.

The narcosis is there for sure and gradually increases with depth. The other factors, CO2, anxiety, inexperience,etc. have nothing to do with narcosis but are simply made worse by it. Many people who have stories about freaking out at 100 fsw are in my opinion not primarily suffering from narcosis but rather from all of the other things listed above and simply made worse by the narcosis.

 

[boulderjohn]

The human mind is very suggestible, if you expect or anticipate a result the human mind often delivers. There are often suppressed fears, when you are alone, deep, dark, cold, anxious, and expecting a result (narcosis) your mind will comply and release the demons. The demons are your own manufacture but we have to have something to blame it on beyond ourselves so we choose Rapture of the Deep. We need demons. That doesn't mean that narcosis is not a real effect but I think it is often highly exaggerated, especially at moderate (less than 130ish feet) sport diver depths, for our own purposes, we need a demon, so our minds give us one.

N

The Dive Training magazine article mentioned above alludes to a research study that supports this. People who were trained through extensive instruction to believe that narcosis is unavoidable and severely debilitating were unable to perform tasks at depth (200 feet). People who were trained to believe that narcosis was not all that bad and could be overcome through will power performed the same tasks just fine.

That does not mean narcosis is not real. My opinoin is that you can minimize but not eliminate the effects.

 

[DOkie]

Good way to put it.... Don't want to offend anyone, but I think the stories of folks freaking out from narcosis at 100' are rather unlikely also. Is it possible to feel the effects? Yes, but if you're freaking out, something else is causing that.

In the article that I mentioned earlier, they (don't remember who) took three groups. This isn't verbatim, but they told each group a different scenario. Group 1 was the "you're going to die" group. Group 2 was the "you're going to get narced, but deal with it" group and group three was told that narcosis is no big deal not going to affect you, etc.... At an equivalent of 200' group 1 failed miserably on testing. Group 2 only had two failures and group 3 did better at depth than they did at surface.

 

[HowardE]

Good way to put it.... Don't want to offend anyone, but I think the stories of folks freaking out from narcosis at 100' are rather unlikely also. Is it possible to feel the effects? Yes, but if you're freaking out, something else is causing that.

Agreed. This is probably more aptly described as anxiety. Are there effects of narcosis at 100'? Sure... somewhat... but not so much that it would cause you to lose your mind.

At 200' I was very conscious of the tunnel vision effect. You lose a lot of your peripheral vision. You are impaired (Like I've said... when I was young - I followed the Grateful Dead - I know what impaired is). People who dive below 150 feet (where the PPN2 is almost 4.4) there is definitely narcosis. The question is - how people can deal with it. It's like those who say they can drive when they're drunk. Some people THINK they can do it. Maybe they can do a math problem, or solve a puzzle, or put a nut on a bolt. Which really leads to the BIG question... What are you going to do if something goes wrong, and you have to think fast? Lost gas, Freeflow, loss of buoyancy, entanglement... if something like this happens at deep depths, on air, where you are really narced... how will it end for you? Personally, I'd dive to 150 maybe even 160 if I knew that the max depth was 160, and I wouldn't be spending the whole dive at that depth; on air, and not be worried about the narcosis. For me... I prefer helium in my mix if my planned depth is below 160 feet... 160 feet with 35% helium has an END of less than 100 feet. Huge difference.

 

[DOkie]

That's why "managing" narcosis at those depths begins BEFORE the dive. While diving last year, we had a double free flow at depth. (Both mine and my husbands). We were diving with the same brand of reg and come to find out there was a defect... Because we've gone over and over these situations, both in theory and practice, and because we had redundent air supplies, it was no big deal. In fact we had several divers pass us on the line giving us the OK sign. (So we must have appeared pretty calm). We worked on each others equipment, got one of the regs working again and teminated the dive safely with our stops. Our equipment is always in the same place, we always have the same dive plan, and we've been married 20 years so we read each other very well.

Helium is a good and valid option, but is not readily available in all areas. 90% of our diving is below 135 feet. To obtain a helium mix, it's a two hour drive one way.

165 is my cutoff. Beyond that I would not be able to function in a way that would be safe for either me or my buddy.

 

[wedivebc]

One agentcy I trained through reccomends a maximum depth on air of 99 feet (30 m) based on the statistical/theoretical effect of Nitrogen at a partial pressure of 4.0 ATA causing narcotic affects.

Actually a recommended PP of nitrogen of 4.0 ata would result in a depth of 134ft