Max optimal depth on air, narcosis related

[Crowley]

Out of the many hundreds of deep dives I have conducted as diver, guide or instructor, I would suggest the 30 metre mark is a good guideline. The standard recreational depth limit is rather arbitrary, in terms of where it originates historically, but in my experience it's a pretty good delimiter for narcosis.

Yes, in part it's physiological - and I don't think anybody knows 100% why it occurs (current theory involves nitrogen dissolving at high partial pressure into the protein that surrounds our nerve fibres, thus interfering with signal transmission) but also as others have rightly stated before me, it can be affected by factors such as cold and visibility and therefore seems to have physical and psychological causes also.

I think it happens to almost everybody, but many people don't actually realise it's happening, and therefore claim to have never been narced. That may well be true but again, I think if you've spent a few minutes at 30metres, you've probably been a bit narced. I've seen people at 40 metres who are fine, and I've seen others go positively loopy at about 24 metres (and panic with it)

Narcosis is, I think, a subject too easily glossed over - yes it's not a serious condition in itself, but it can lead to serious problems in much the same manner that a person who chooses to drive after drinking a few beers may feel perfectly fine until the pedestrian steps off the sidewalk.... a diver might not think they are narced until they have to deal with a rapidly changing situation where quick decisions might have to be made. The standard PADI literature suggests that people will see pink elephants and offer their regulators to fish (and these things really do happen) and har har yes that's all very comical but narcosis can lead to problems and I think divers need to understand that it does have an appreciable effect.

It's also possible to some extent to 'acclimatise' to narcosis - it seems that regular deep diving and training will decrease your susceptibility - again, a rather unpleasant analogy to use but - in the same way a person who drinks regularly will build up a tolerance to alcohol.

Hope that helps somewhat,

Happy diving,

C.

 

[sschlesi]

Several of my dives to 90+' I can feel the narc a little, usually I can tell my thinking is slowed down a bit. Occasionally I notice a bit of tunnel-vision.

The most narc'd I have ever been was on a dive that maxed out at 88', the deep portion of the dive was mostly in the 70's. In my log I wrote:

"I became significantly narc'd on reaching ~70'. I was a bit dizzy for ~30s, and buzzed/distracted for much of the dive. I mixed up Vince + Ron. Remained narc'd a bit until after ascent."

On that dive there were 2 pairs of divers. I kept following the wrong buddy, I couldn't tell the difference between my buddy Ron who had a bright yellow 30CF pony strapped to his back, and big blue smurf gloves, from Vince who had no pony and plain black gloves. We were back in ~40' of water near the end of the dive before I realized that the guy who kept crowding in on me was my buddy. My buddy was not the guy who I'd been following around for most of the dive. I should have thumbed that dive, and I almost did early on when I felt dizzy for a short time. Very shortly after that I was so narc'd that all good sense had left me.

That dive was definitely the exception, and I've never experienced anything close to that level of impairment without consuming excessive amounts of alcohol. It just goes to show there really is no hard and fast rule for narcosis.

 

[elan]

Thanks guys, I think I will stick to 100' for now. The bottom time below is short anyways and until I get my doubles and go through deco training I see no reason going below.

 

[ivobj]

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.

It is very difficult to define as narcosis varies between people, water temperature, stress level, physical effort, etc, too many variables, but I would consider that below 40 to 45 meters, almost all divers get narced to some extent, below 30 many present, even in a milder degree, some narcosis (many times unoticed), and below the 50s let's say that the most narcosis prone people may be offering the reg for the fish to breath.... In this sense the recommended depth to start including He in the blend for my tech agency (don't know if the same as muddiver) is also 30 meters.

 

[Meng_Tze]

.... based on the statistical/theoretical effect of Nitrogen at a partial pressure of 4.0 ATA causing narcotic affects.

I have always kept my PPN2 below 4 ATA. Even then some times I noticed narcosis setting in at a depth of 3 ATA, sometimes not at all. Even within the person it varies.

 

[dumpsterDiver]

Sorry if I have not put the question clear, what I was trying to ask is
"out of real experience at what depth does an average Joe start experiencing narcosis"

I think this has nothing to do with certifying agency and certifications etc, that's the nature of how our body behaves. And if I talk to one instructor it's just one person that is much less than a lot of those people on SB who has experience.

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',

Is there any statistical data is available ?

From my expereince, I feel no clear narcosis until a depth of around 150-160 maybe, but you can be sure that you are impaired at a shallower depth. I definetely can feel it at 180 feet and generally now limit my air dives to 200 ft. I've done some diving below 200, but to be honest, at 225 my tongue and lips are starting to get numb, your ability to take in all the visual information begins to close down somewhat and I become pretty ADD with trouble concentrating, monitoring pressure, time etc.

When I was about 15 I commonly dove to 90 feet in cold water and never felt any narcosis, however when I did my first deep solo wreck dive to 130 +, I felt fine until I realized that I was having significant trouble coordinating my eyes and head to follow the light beam from my light. A fish would swim to the left and I would sweep the light across the fish and my head would move the other way. I quickly realized I was pretty wasted, but still felt somewhat confident and in controll.

Now after many hundreds of dives to 115-130, I experience little or no narcosis symptoms. To function well at deeper depths (over about 130), I tthink the diver needs to be very experienced and confident that they have done similar dives hundreds of times before. When everything it automatic and there are no novel problems or true emergencies, diving deeper is deceptively easy for many people.

When I am diving around 170 and I begin to feel zero narcosis, I try to remind myself that the reason I feel no narcosis is because I am impaired. Most actions, require an extra moment of reflection and thought and a double check on your own thought process to try to ensure that you are not doing something really stupid.

When diving around 180-190, I can not recall how many times I have grabbed my console, looked at my pressure gage, decided it was "fine" and then within 2 seconds realize that I don't know the numerical value of air pressure that I just checked, only that it "looked OK". Sometimes I will immediately check it again and forget the pressure a second time! All this when I feel fine, I'm coordinated and can swim and regulate my bouyancy perfectly and even hunt and stalk fish. It is like having bad ADD, I think. It requires more concentration and an understanding that you really are "stupid" at this depth and you need to be careful.

Based on what I read on this board, indivdual susceptibility varies widely and of course high workloads can make a huge difference.

 

[jkaterenchuk]

I have always kept my PPN2 below 4 ATA. Even then some times I noticed narcosis setting in at a depth of 3 ATA, sometimes not at all. Even within the person it varies.

I echo what Meng_Tze says. You need to find out what works for you. I have found increased narcosis at less depth when cold (41F) and poor visability (less then 10ft) or when diving CCR then when diving warm 80, good vis (50ft plus) or Open Circuit. On Cave dives I will generally go for a lower ppN2 ATA then an equivalent open water dive.

Therefore I plan my dives with max ppN2 of 3 ATA if cold water, poor viz or CCR and 4 ATA if otherwise.

Usually my narc feeling is increase relaxation with the warm water and better viz and greater anxiety when cold, low viz and CCR.

John

 

[DOkie]

While sitting in a Dr's office today, I picked up the May issue of Dive Training Magazine. There is actually a very interesting article on Narcosis with three different test groups.

Personally, my cutoff is 165 on air in clear (cold) water. In that depth, I definitely have to concentrate. There is one particular wreck that we dive at 135 is cold and very dark and sits on a the edge of a valley. I have to be particularly diligent to brush off the "creeps" on that one.

 

[RickHeil]

I agree with most all thats been posted - varies by individual, its progressive, etc. One factor not mentioned I think is key in my experience is your confidence on the dive. When my comfort/experience/conditioning/training is prime and doing a clear warm open water dive in an area I'm familiar with I feel minimal narcotic effects at 100,110,120,130 ft. In the 120-150 range narcosis is usually noticeable yet very manageable - again depends on task loading. Then again when in dark, cold, unfamiliar water doing a dive (e.g. a wreck) I don't know, with greater task loading, then given all that the narcosis is definitely more of an effect - even at 90-100 ft.
Rather than an absolute depth my thought is to know, plan, and execute the dive within my training and experience level I'm comfortable with. With new gear, new skills this may be a 60ft limit. Doing I dive of done dozens of times, my regular config, etc then a dive well over 100ft would be no problem.
In the end each of us knows our own limits and its up to us to stay in them.

Oh my most narc'ed dive was probably at 115 ft, and my deepest 160. I can normally dive 100-140 with only modest narc effects, my greater concern is the dive plan, air managment and executing the deco procedures.

 

[elan]

With new gear, new skills this may be a 60ft limit. Doing I dive of done dozens of times, my regular config, etc then a dive well over 100ft would be no problem.

You know I came to the same thing, once I get my config changed I limit my dives to 50' for the next 3-4 dives until I can do all of the things more or less effectively, and only after I feel that I'm confident and comfortable with the config I get below 50, generally all experimenting stay within 40-50' range and I only do it with one of my buddies to whom I trust and with whom I have been in different situations. Then he is watching me and is ready to help right away in case any issue arises. With insta buddies and deeper dives I go back to my settled config. I have came to a conclusion hard way that I should not change more then 1 variable of the dive. Config, condition, depth, time , buddy. If I change one of them all the other should stay the same as before.