Got narced hard today!!

[MHK]

SimonN once bubbled...

Thanks AzAtty.

<snip>

I am not going to dispute this, however, we are not suddenly going to start suffering CO2 narcosis because we now know about it. In other words, the narcosis we thought was due entirely from nitrogen may be from other sources.

So what? The narcosis level is still the same.

While diving on mix may be safer, I still have never seen any statistics that diving on air to 50M is inherently dangerous.

I am not trying to be macho because I know that diving is not very James Bond and it does not impress the chicks and I have no interest in impressing other males.

I am being cheap though. At the moment, it costs me around $65 to do a dive. If I was to do the same dive on mix, it would cost me around $180. I makes my choices.

I appreciate that for you it's a financial issue but what still concerns me, and I'm also speaking to those other's that are following the thread, is a few things.

First off you suggest that the analysis has little or no bearing on narcosis, which is incorrect from a factual standpoint. If you look to the Meyer-Overton rule which predicts the anasthetic potency [ ie; the narcosis] of a gas. It states in pertinent part that "the potency of a gas is inversely related to its lipid solubility." In other words, more lipid soluble gases produce narcotic effects at lower concentrations then soluble gases. If you then look to the Bunsen Solubility Coefficients you can compare Helium and Nitrogen:

Helium 0.015
Nitrogen 0.052

Furthermore when you compare the narcotic potency of helium and Nitrogen you'll see that on a scale of 0-5 [ 5 being the least] that helium is 4.26 and nitrogen is 1.

Also the only study that I can place my hands on right now that speaks to the "adaptation" to narcosis by repetitive exposure confirms that you do not "adapt" to narcosis. The study was done breathing air at 54.6 meters of seawter once a day for five days and that there was no adaptation..

It's clear with any objective reading of the issue that there is no question that using a helium based mixture reduces narcosis so I disagree strongly with your thoughts.

Moreover, the real issue to concern yourself with in diving deeper on air is the potential for C02 accumulation, and as I've noted earlier C02 is nearly 130 times more narcotic then nitrogen so that is the danger that is often overlooked in these debates. Furthermore when you look to gas density, which becomes a true concern at depth you'll also see that helium is significantly more favorable in that department. As you should know the deeper you go the denser the gas and the potential for C02 accumulation increases. Now factor in poor preforming regulator's, excessive gear configurations, lack of streamlinning, current and so forth and the C02 accumulation is easy to see. Nitrogen is 1.2504 g/l whereas helium is 0.179 g/l on the density scale..

When you look at all of the factors, it's clear with the information and technology available currently that there is no good reason to continue the deep diving practice and any attempts to suggest that you can "adapt" to narcosis is obfuscation at a minimum and intellectually dishonest on a greater level. Moreover, by reducing the debate to the subjective "adaptation of narcosis" you avoid talking about the true concern which is C02 accumulation.

Regards

 

[newdiverAZ]

In some of the posts, a few stated there were problems with breathing nitrox at depth. I am not nitrox certified and haven't learned much about it yet. My deepest dive was 92' with no apparent onset of narcosis. Could someone explain the reason to not use nitrox on a deeper dive. I understand there are depth ht considerations for different blends due to o2 toxicity, but I thougt nitrox was supposed to help in this regard. Like I said, I have not had any training in this yet, and from some of the posts wonder if it is worth the time. I also wonder if this thread applies more to technical diving than recreational. Is it just a matter of different opinions on what is deep?




Thanx
Brian

 

[MHK]

newdiverAZ once bubbled...
In some of the posts, a few stated there were problems with breathing nitrox at depth. I am not nitrox certified and haven't learned much about it yet. My deepest dive was 92' with no apparent onset of narcosis. Could someone explain the reason to not use nitrox on a deeper dive. I understand there are depth ht considerations for different blends due to o2 toxicity, but I thougt nitrox was supposed to help in this regard. Like I said, I have not had any training in this yet, and from some of the posts wonder if it is worth the time. I also wonder if this thread applies more to technical diving than recreational. Is it just a matter of different opinions on what is deep?




Thanx
Brian

Like most things in life you don't get anything for free. Nitrox is a mix of oxygen and nitrogen. The standard air that you breath is 21% oxygen [ 02] and 79% Nitrogen [N2] There are a very small amount of trace gases but to immaterial to discuss.

A nitrox mix will generally elevate the oxygen content. The most often used are 32% and 36%, meaning that the mix will have 32% 02 and 68% N2 for a 32% mix as it's called. A 36% mix will have, as you may guess 36% 02 and 64% N2. The idea being that by replacing some of the N2 with additional 02 you can decrease the tissue loading of nitrogen and thus increase your bottom times.

However as I noted you don't get anything for free. Oxygen becomes toxic as you breath it at depth [ or increased partial pressures].. The measuring rod, if you will, for that Maximum Operating Depth is measured in what we call PP02. The maximun operating depth, as you may imagine is the maximiun depth at which your chosen mix should be breathed without risking oxygen toxicity. Oxygen toxicity means that the diver will convulse, and if that happens 100' or so underwater it's quit likely the diver will die. So paying strict attention to the maximum operating depth is vital..

NOAA recommends the "measuring rod" to be 1.6 [ GUE recommends 1.4 or lower] but the point being that using the standard NOAA recommendation a 32% Nitrox mix means that you have a mximum operating depth of 130', which is why 32% was chosen to coincide with the recreational diving limits. At 130' however because of the reduced nitrogen in your mix it would appear, in terms of narcosis, that you were really diving at 107' and thus you would have a roughly 23' "advantage"..

So the thinking is that you trade off a reduced level of narcosis in exchange for the added oxygen in the mix.. The balancing act is that you don't want to add to much extra oxygen which will reduce the narcosis level, but may increase the likliehood of exposing you to oxygen toxicity..

That's a real Reader's Digest version of Nitrox, but if you have more questions let me know or seek out qualified training..

Later

 

[newdiverAZ]

Thanx MHK,
I understand the basics of nitrox and was gonna take the nitrox course. The part that is confusing was the people sayin nitrox was bad. And if I'm understanding you correctly the bad part is the oxygen, and assume in the helium mix you are just lowering the amount of nitrogen, without increasing the oxygen. If this is true is it even worth taking a nitrox course or do ya just do the tri-mix course




Thanx
Brian

 

[SimonN]

MHK once bubbled...

First off you suggest that the analysis has little or no bearing on narcosis,

Actually, that is not what I said. I said that we have been experiencing the same level of narcosis at 50M since the beginning of time, regardless of whether it is from N2, CO2 or anything else.

Also the only study that I can place my hands on right now that speaks to the "adaptation" to narcosis by repetitive exposure confirms that you do not "adapt" to narcosis. The study was done breathing air at 54.6 meters of seawter once a day for five days and that there was no adaptation..

Addressed in an earlier post to this thread.

It's clear with any objective reading of the issue that there is no question that using a helium based mixture reduces narcosis so I disagree strongly with your thoughts.

Where have I said that helium does not reduce narcosis?

Moreover, the real issue to concern yourself with in diving deeper on air is the potential for C02 accumulation, and as I've noted earlier C02 is nearly 130 times more narcotic then nitrogen so that is the danger that is often overlooked in these debates.

Where is the evidence, as opposed to theories, for this? See point about narcosis earlier in this post.

Furthermore when you look to gas density, which becomes a true concern at depth you'll also see that helium is significantly more favorable in that department. As you should know the deeper you go the denser the gas and the potential for C02 accumulation increases. Now factor in poor preforming regulator's, excessive gear configurations, lack of streamlinning, current and so forth and the C02 accumulation is easy to see. Nitrogen is 1.2504 g/l whereas helium is 0.179 g/l on the density scale..

However, where are the statistics that prove this to be a problem?

When you look at all of the factors, it's clear with the information and technology available currently that there is no good reason to continue the deep diving practice and any attempts to suggest that you can "adapt" to narcosis is obfuscation at a minimum and intellectually dishonest on a greater level.

Actually, I think it would be intellectually dishonest of me to not agree with my experiences.

Moreover, by reducing the debate to the subjective "adaptation of narcosis" you avoid talking about the true concern which is C02 accumulation.

Prove CO2 to be the true concern then? I agree that avoiding CO2 retention is a good thing, however, where are the statistics to prove this is a problem on air @ 50M?

 

[MASS-Diver]

MHK,

Thanks for pointing out that CO2 information in one your last posts, that's very interesting. I think alot of intermediate level divers like myself are not aware of that benefit of diving MIX (having never dove it).

So, mix actually does breath that much better (for example - same reg- 150' with MIX vs air - can you feel the difference)?

I thought I knew most of the obvious advantages of TRIMIX, mainly reducing narcosis and for deeper diving lowering PO2, but, I did not realize that gas density was an added bonus even in this era of high performance regs. I've really "tugged on" my ATX 200 in about 100' of water with a current and it kept up pretty well, but, still Co2 accumaltions makes me very nervous since from what I hear (from rebreather diving friends) you can't really feel it coming on, all of sudden youa re just napping.

For me, the case for TRIMIX is pretty solid, I'll take any advantage I can get, whether it's being in top shape, not going in the water with tons of drag, or breathing the best gas for the dive.

 

[MikeFerrara]

The problem with accident statistics is almost all divers who die drown. I witnessed an accident where on the way up from a 120 ft dive a diver panicked because he felt like he wasn't getting enough air and made a rapid ascent. The ambulance took him away. It could have been a problem with CO2 but you can't prove it. A student one time left her buddy and came to me signalliny "up". I couldn't see a proble so I had her stay still and just breath. After a few moments she was fine. CO2? I had another student so narced at 120 ft that he couldn't perform a simple out and back. He was picking up random directions and bocomming agtated. I ended the dive and took him up. Narcosis? Why so bad at 120? CO2? This diver had done sever 100+ ft dives in the past. He was only a few feet deeper than his deepest dive to date. I have seen lots of things like this and I have seen divers injured by rapid ascents and near drownings. I think we do see that narcosis and CO2 retention are problems but they don't leave any evidence.

 

[MHK]

newdiverAZ once bubbled...
Thanx MHK,
I understand the basics of nitrox and was gonna take the nitrox course. The part that is confusing was the people sayin nitrox was bad. And if I'm understanding you correctly the bad part is the oxygen, and assume in the helium mix you are just lowering the amount of nitrogen, without increasing the oxygen. If this is true is it even worth taking a nitrox course or do ya just do the tri-mix course




Thanx
Brian

It's hard, and quite frankly unwise, to discuss all the nuances of mix over a newsgroup. But the short answer to your question is that it depends..

Depending on depth you consider the proper mix. GUE has standardized mixes to eliminate variables and in the recreational ranges we use either a 32% Nitrox mix or a 30/30 Triox mix depending on depth. Generally speaking if you are 80' or above you'll use 32%, deeper then 100' you'll use a 30/30 and in the 80' to 100' range the answer is that it depends. If I were spending most of my dive in the 90' or 100' range I'd use 30/30, if I were spending most of my dive at 80' or 90' and were maybe going to jump down to 90' or 95' for a few moments I'd probably use a 32%..

Hope that helps..

Later

 

[LUBOLD8431]

IANTD Technical Diver / TDI Extended Range

Two technical dive agencies that teach deep air...

Hmmm....

 

[Uncle Pug]

...I'm startin' to rethink this:

Maybe if M.A.D.D. used their resources to teach folk how to safely drive while drunk we would have fewer traffic fatalities.