Max. depth on Air

[perpet1]

well said!

The only thing I would add though is that as with beer some people can have 3 beers and you would NEVER know it while others are fine after three beers.

I have done some deep divs on air in warm water. In order to do this type of diving you have to work up to it. Just as if you drink all the time you are better able to handle drinking (you can not deny this). We all know people that can operate 100% fine at BAC .1 while others are falling all over themself. In fact when I used to drink a lot (way back) I could drink a lot more then I can now without getting sloppy and I have to say it takes a fraction of that now that I hardly ever drink. My friend, this is not just my perception it is reality there is tollerance to any narcotic.

Moral to the story: You can and will built a tollerance to any narcotic. I agree you will have the same amount in your body and BAC is simply how much you drink over time BUT the narcotic affect will differ based on your (you guessed it) Tollerance.

So while I have not been deep in a while if I dove down to 134' where PN2 is 4.0 (give or take) I would probably feel the effect and be impared. Now back a few years ago when I was going to 100-110 feet ever day or every other day I will bet that at a PN2 of 4.0 I was fine and NOT impared.


I agree with you last statement:
There's a difference between medical (and actual) "impairment" and the legal definition.

 

[DA Aquamaster]

In my law enforcement days we would get the state lab reports every morning for the bllod alcohol levels for all the DUI's in the state the night before. I frequently saw BAC's of .30 (at which point the average person should have been unconsious) .40, (at which point they should have been comatose) and .50 (where they should by all rights have been dead). But these people were not only consious but actually driving a car. They drove badly but had developed a tolerance to alcohol to such a degree that they were driving at a blood alcohol level where the average person would be dead.

In a similar fashion divers will develop a tolerance to nitrogen narcosis. So the depth at which narcosis impairs them to the point of being at excessive risk varies from diver to diver and from day to day.

 

[perpet1]

.5!?!

and awake?

wow now that would be very deep to coralate that to diving....

 

[Dan MacKay]

DA Aquamaster once bubbled...

In a similar fashion divers will develop a tolerance to nitrogen narcosis. So the depth at which narcosis impairs them to the point of being at excessive risk varies from diver to diver and from day to day.

There have been many studies that have tried to prove this, none of them successful. All the studies that I have read conclude that there was no appreciable adaptive behaviours displayed among the control population.

In other words the great manly man statement of I have learned to adapt is horse hocky. Get over it. Narcosis anesthesizes your brain, that is assuming the idiot diving deep on air has one to begin with.

 

[perpet1]

Dan MacKay once bubbled...


There have been many studies that have tried to prove this, none of them successful. All the studies that I have read conclude that there was no appreciable adaptive behaviours displayed among the control population.

In other words the great manly man statement of I have learned to adapt is horse hocky. Get over it. Narcosis anesthesizes your brain, that is assuming the idiot diving deep on air has one to begin with.

studies are in question

Be careful with your horse hocky!

here ia an MD and his take on it:

http://www.mtsinai.org/pulmonary/books/scuba/gaspress.htm

"There is also some evidence that some divers can become partially acclimated to the effects of excess nitrogen; the more frequently they dive the less each subsequent dive appears to affect them. "


Here is another one from J. H. Abraini, Ph.D.

http://www.sportsci.org/encyc/drafts/Nitrogen_narcosis.doc
'Opposingly, frequent exposure at depth during up to 5 days has been shown to afford some adaptation with real improvement in performance (for review, see ref. 6 and 9).'


Pete

 

[RichLockyer]

perpet1 once bubbled...
"the more frequently they dive the less each subsequent dive appears to affect them. "
......
"shown to afford some adaptation with real improvement in performance

Muscle memory? Familiarity with the testing procedure?

How "real world" are the test conditions in these studies?
Kinda goes back to "Wha do you want me to prove, I'll perform a study to support it".

Real performance measurement would have to include heavy multitasking, unexpected drills, and rotated skills tests.

Another thing missing is a control group... but how do you have a control group under pressure?

Double-blind study... 150ft task-loading, air vs 21% heliox. Tanks not marked, and divers forced to breathe a pony to 20ft with the back gas locked off so they can't breathe on-deck and see if they talk like Donald Duck.

 

[Dan MacKay]

perpet1 once bubbled...


studies are in question

Be careful with your horse hocky!

Pete

Hi Pete,

For heavens sake will you just listen to what the deep air advocate are saying? Even the studies or opinions that you are quoting are saying the "some" folks "may" be displaying adaptive behaviour.

You forget that most of these studies are done in a nice safe dry tank. Not in a stressful situation. Now put you head in a place where you cannot breath, say at 180', cold, crappy vis, swimming against a current and then "adapt" to narcosis. Absolute insanity. At this point you may get away with one minor thing going wrong but never two and if the narcosis does not get you the CO2 will.

Deep air is very dangerous behaviour specially when there are so many alternatives available these days. What is the cost of you life? Aparently less than a 21/35 as or what ever mix as the number of deep air body recoveries will attest to.

It is your life and do what you wish with it, but for goodness sake do not even suggest in a forum like this where young and less informed divers are influenced, that deep air is safe in any way shape or form.

 

[perpet1]

I think you missunderstood my agruement. I do not dissagree with you that deep air is dangerous. That you will not get an arguement out of me.


I personally have done it and I really do think it is STUPID. Yes, you there are noted experts (PHD's) that agree that you can build a tollerance to Narcosis. Is it smart to do so? I am thinking no, as would any reasonable person. That is like saying lets become an alcoholic so you have a better tollerance to alcohol. Truth is you would have a better tollerance to alachol but at what cost?

For everyone to say you don't you obviously have not don a lot of deep diving over time because you do build a tollerance to it. Do I think I am a stud because I have done it? NO! Do I recommend it? NO! Have I seen the direct effects of narcisis? YES (to the point where I almost died) Do I think almost dieing makes me special in any way? NO (putting yourself in that position is about the dumbest thing a person can do)

As for the comments about a nice enviornment you could not be more wrong. All the studies that are done in very controlled enviornments (chambers) tend to support that you can not build a tollerance to narcosis. It is the general observations of real world situations (an noted by researchers) the tend to support that you can build a tollerance. This is why it is such a hard concept to actually quanitfy because real world does not support the controlled enviornment conclusions. But then again you yourself noted there was a difference.

Just because it is easier for you to justify in your head that deep always = dangerous if you believe Narcosis is a 100% given in all deep situations.

Here is what you want to hear and I do agree with it: Diving deep on air is dangerous and it should not be done. Now what is deep? I personally think 130' is a good recreational limit.

Pete

 

[DrSteve]

At 100 feet my buddy passed me a slate - I knew what I had to do...add up 5 numbers e.g.
7+8-5+6-2

He timed me - even allowing for fumbles and the like it was 25s.

On the surface I said he chose difficult numbers - I was never good with 7's and 8's.

He handed me the slate again and gave me a different sum and asked me to do it:
7-8+5-6+2

Took me 3s!

Seriously, try it. It opened my eyes to my previously held belief "I've never tried to hand my demand valve to a fish, I've never been narced - I'm OK."

 

[perpet1]

DrSteve once bubbled...
At 100 feet my buddy passed me a slate - I knew what I had to do...add up 5 numbers e.g.
7+8-5+6-2

He timed me - even allowing for fumbles and the like it was 25s.

On the surface I said he chose difficult numbers - I was never good with 7's and 8's.

He handed me the slate again and gave me a different sum and asked me to do it:
7-8+5-6+2

Took me 3s!

Seriously, try it. It opened my eyes to my previously held belief "I've never tried to hand my demand valve to a fish, I've never been narced - I'm OK."

I am betting if you did that same dive three or four days a week for a month you would notice an improvement.


And that is an exercise you should have to do for any AOW / deep speciality class.

Pete