Not diving to greater than 30m/100ft unless with helium

[Jack Hammer]

I used to regularly make dives in the 150' range on air/nitrox and was very comfortable. Then a few years ago I starting becoming more and more aware of just how affected by narcosis I really was and had been. I decided to use helium for those dives but was OK doing dives in the 130' range on air/nitrox. Last year I started becoming more aware of how much narcosis affects me at those depths and prefer helium there too. I've found the effects to be more pronounced in colder/Lower vis conditions, but if you are aware of the subtleties its often also there in warmer/clearer waters just waiting for a real problem to occur to rear its ugly head. I think for technical dives, especially with penetration/overhead/current/challenging conditions helium is an important part of the plan.

 

[Lorenzoid]

I used to regularly make dives in the 150' range on air/nitrox and was very comfortable. Then a few years ago I starting becoming more and more aware of just how affected by narcosis I really was and had been. I decided to use helium for those dives but was OK doing dives in the 130' range on air/nitrox. Last year I started becoming more aware of how much narcosis affects me at those depths and prefer helium there too. I've found the effects to be more pronounced in colder/Lower vis conditions, but if you are aware of the subtleties its often also there in warmer/clearer waters just waiting for a real problem to occur to rear its ugly head. I think for technical dives, especially with penetration/overhead/current/challenging conditions helium is an important part of the plan.

Thanks for the data point. So, if you have actually done the same dives on air/nitrox and helium in the 130-150 foot range and noticed the difference, that would suggest CO2 wasn't the major player in your case.

 

[guyharrisonphoto]

Unfortunately, too few divers allow themselves the time to learn the difference between elevated CO2 and the onset symptoms of narcosis. Elevated CO2 is especially a problem among those that obsess over their RMV instead of adequate lung ventilation. The symptoms are often indistinguishable, until you overtly modify your breathing to reduce CO2.

CO2 symptoms can go away with proper breathing and can occur on Trimix or HeO2. IGN (Inert Gas Narcosis) does not, though the intensity often reduces. There’s a lot more to narcosis management than just switching mixes. It is also about learning to manage yourself under stress.

IGN is not a weakness or a strength, only a human characteristic that must be managed.

Akimbo, can you describe the breathing techniques you use for adequate lung ventilation, or are there references for that?

I read the GUE article as well, seems like trimix can be very useful for eliminating CO2 elevation as well as nitrogen narcosis.

This discussion is very interesting, as deep rec dives (100-140) in strong currents, often with some exertion, are pretty standard fare where I dive. Warm clear water, though.

 

[Akimbo]

CO2 is indeed believed "worse than nitrogen." The problem is that one can only control their breathing so much. We can practice, but most of us will never be yoga masters or commercial divers…

Breathing technique is only part of the equation, controlling exertion is the other major factor, but physical condition also plays a role. Anyone can breathe like a commercial diver; just don’t expect much bottom time since you will burn through a set of doubles like a gas turbine. Commercial divers get their gas through a hose, have massive supplies switched for them on deck, and don’t pay for any of it.

Scuba divers must balance the gas supplies they can carry with the lower end of “adequate” lung ventilation. Fortunately you can learn to use “CO2 awareness” to continually modify your breathing and exertion to manage it rather than a 1½ Ft³/Min RMV. I suspect that many experienced divers do it without even being aware.

---------- Post added October 6th, 2015 at 09:05 AM ----------

Akimbo, can you describe the breathing techniques you use for adequate lung ventilation, or are there references for that?...

I don’t recall a description, but does the above help explain it? A lot of divers increase breathing and/or reduce exertion almost automatically, sort of using their bodies as CO2 analyzers. Elevated CO2 automatically forces you to breathe faster, you just need to learn to breathe deeper instead as a diver.

People notice different symptoms first but range from feeling uneasy, short of breath, or just “not right”. It isn’t that different on deck. How many times have you made yourself slow down and breathe just to clear your head of a feeling of dread?

 

[guyharrisonphoto]

Yes, that is a big help. I am thinking something like deep yoga breathing, at a faster pace when working. My wife/buddy "sips" air in shallower breaths and has commented several times that she feels uneasy on these deeper dives which is not really from lack of experience. I had not thought about a physiological explanation related to CO2, but a lot of this makes sense now. I am going to work with her (and practice myself) some deeper breathing techniques for fuller ventilation on our next dive.

Actually, I think this thread is very, very important. This is something that is just not addressed in either OW or AOW. Divers are drilled about nitrogen narcosis, which comes into play only rarely at rec depths (I have managed 240 on air in the "old days"), but CO2 seems to be a danger that is not addressed and which might be even worse.

 

[Lorenzoid]

In his book The Six Skills and Other Discussions, Steve Lewis offers some breathing technique.

 

[abscuba]

Narcosis is a tricky one to nail down because there is so much we still don't know about it. It is a moving target as was mentioned before I have had friends that regularly do dives to 400ft go from bing fine on one dive having to stop at 80ft due to affects on another dive then be fine on the dive after. When you throw CO2 into the mix it becomes very difficult to nail down what is affecting what. This is the problem with set depths because you won't always feel the same thing at the same depth. It is better to know when you are feeling affects of either necrosis or CO2 slow down or stop if able slow your breathing then look at your task at hand. Helium does help with narcosis but it does not eliminate it you just push the limit farther down Oxygen and Nitrogen are still in the gas your are breathing. Yes Oxygen, most OW dive manuals miss the fact that O2 is narcotic so nitrox does not fix narcosis you just feel the effect of O2 less because your body can not handle as high of partial pressures of O2 as it can nitrogen, but you are still breathing 2 narcotic gasses. What ever your reason for your limits just know what they are and have a plan that is muscle memory for what you do when you are feeling impaired. Every one will experience narcosis differently and since we still don't know much about narcosis past the symptoms all we can really do is know how our body reacts and work to gain experience to handle situations where not all cylinders are firing.

 

[Akimbo]

… It is a moving target as was mentioned before I have had friends that regularly do dives to 400ft go from bing fine on one dive having to stop at 80ft due to affects on another dive then be fine on the dive after...

I am very skeptical of attributing symptoms to nitrogen narcosis at 80'. I’m not sure what dive courses are teaching but symptoms are infinitely more likely CO2 and/or equalization issues than narcosis.

 

[Germie]

I teach the adv. nitrox course, 42m. I can teach the technical diver, but don't do that. I teach then normoxic trimix. It is a difficult discussion, when teaching I am responsable and I dive same gas as students. So I don't teach the technical diver course, but only the normoxic course with helium. Adv. nitrox I teach as I believe the 42m on air is ok, if you know the risks. Normally I get narced between 44 and 46m, tunnelvision. If people want to try helium and do the art course, I don't say don't do that. Then I dive with helium too of course. 42m is the max of adv. nitrox and I try to reach that depth 1 time with students in a course. I always tell students that narcoses is strange, sometimes not feelable, sometimes really heavy, not predictable. And that it is possible I have to turn too when I feel it myself.
CO2 is a contributing factor for narcoses.
So when people want to dive helium at 30m, no problem, when people don't want to dive helium up to some greater dephts no problem too. Decide yourself. I explain narcoses and CO2 as distributing factor and hope people feel some kind of narcoses on a dive to 40-42m. Going deeper on air is still done a lot and I don't have problems when people do it, but I don't do myself, and I have problems when people say they don't have any narcoses, that is never true. Everybody has some narcoses. People who say helium is bull**** I don't agree. But the END strict at 30m is sometimes not needed. Choose what your suits and always be carefull. Currents, bad physical condition, and so on, can make you feel more narcoses (co2)

 

[100days-a-year]

I do strenuous work in depths up to 180'ish and video quite a bit of them.I see the effects on other divers in frame vary from day to day and dive to dive too much to believe there is a set guideline for everyone.There are people I don't trust outside of a pool including at least 1 instructor and guys who I enjoy diving deep with due to the obvious competence they show repeatedly.

Glad this didn't degenerate into a 'You're all going to die" deep air commercial from a particular agency.