Dealing with Narcosis on Deep Dives

[tcrusson]

Hi guys,

I've been dealing with very severe narcosis on most of my deep dives this year, actually on any dive past 75m. Sometimes the effects are nice, but they can also be downright scary. I described some of them on my blog: Article: Diving in La La Land.

I did a search on DB and other sites but, to my surprise, could not find much information on narcosis related to Freediving. I was wondering if anyone had valuable information to share on the subject:

- What is narcosis? The effects looked to me pretty similar to nitrogen narcosis experienced when scuba diving. But could it also be CO2 narcosis?

- What is the main trigger for nitrogen narcosis? In scuba documents they get pretty elusive on the subject, and mention stress, darkness, increased exercise, but also a higher concentration of CO2. Apparently the link between nitrogen narcosis and CO2 was documented by Bennett and Elliott in 1993 but I could not find the actual study or a summary to see if it actually applies to breath hold diving.

- Is there a way to prevent it? I read somewhere that a slower descent could help, and even heard that some freedivers hyperventilate before the dive to decrease their CO2 levels? Or do you just need to get used to it?

- Any tips on how to dive under the effect of narcosis? An AIDA instructor trainer told me to focus on technique for example, but as narco comes with a great deal of confusion and disorientation (I sometimes completely forget where I am) I lose track of my thoughts (counting kicks is sometimes just plain impossible).

Thanks,
Tanguy

 

[efattah]

The three known methods to adapt are O2 statics, long deep hangs, and frequent deep dives. You NEED light, possibly on your neckweight, to focus hard on the line. Try to count your strokes. If you cannot, back off the depth until you can, or do more O2 statics. Fluid goggles and any visual distortion make it worse. Darkness and cold make it worse. Fear of the deep, or non confidence, make it worse. CO2 makes it worse. Hyperventilation reduces the narcosis but increases the risk of BO at the end. Diving without packing reduces narcosis. FRC diving produces no narcosis.

Will T. is nearly immune due to his long hangs at 50m (6min) and 1000s of dives over 80m.

Frequently getting drunk increases tolerance as well. Herbert jokes that when he gets hammered he is actually doing 'narcosis training.' Personally I have zero alcohol tolerance.

For me O2 statics worked the best.

 

[tcrusson]

Thanks Eric. I am not packing so no issues with this one. I can understand deep hangs and frequent deep diving to get progressively used to it, but do we know why O2 statics would help?

If fear of the deep makes it worse, does that mean that if you are prone to narcosis, you are very likely to get seriously narc'ed on any new depth PB?

Any difference between fast dives and slow descents?

 

[Simos]

Hi Tanguy

Just out of curiosity, do you get narcosis from a variable weight or sled dive to a similar depth?

Simos
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[tcrusson]

Good point Simos, I forgot about that: I have only done a couple of variable weight dives and never used a sled, so I don't know if it would be relevant, but I did get narcosis on shallower depth (50). Fast descent, but I produced no effort whatsoever to go down and probably very little CO2.

 

[Simos]

By the way, it's just a guess but probably faster descents help lessen narcosis? My rational being that there is less time spent at depth, hence less time for the body to absorb nitrogen (or Co2)...

Am i along the right track?
Presumably that's why deep hangs help? Ie more time for the body at pressure to absorb whatever gas it is that leads to narcosis and hence over time the body gets used to it..
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[tcrusson]

My rational being that there is less time spent at depth, hence less time for the body to absorb nitrogen (or Co2)...

That's what I thought at first, but it was the exact opposite: I got narc'ed faster on a variable weight dive, as shallow as 50m! No effort, very little CO2, no fear, no darkness.

 

[fflupo]

what helps me is the extensive pre visualisation of the dive, like this i have something to stick and focus in LA LA LAND and i don t get missleaded to something..

and as eric said the deep hangs

nice blog tanguy

 

[Simos]

Hi Tanguy
That's really interesting (that you got narc'd earlier).... The only reason I can think of (which sounds a bit far fetched?) is that it might be because of oxygen toxicity?

Ie when you went down faster and more relaxed you had more oxygen... Would be consistent as well perhaps with why not packing and frc helps and maybe that's why o2 statics help.

Would be interesting to find out if anyone has ever breathed nitrox or some other mix and then freedived to depth and find out if there was still narcosis (assuming they lived to tell the tale, that sounds like a BAD idea for other reasons...)
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[efattah]

I have done pure O2 dives to 6m or 7m and I got insane narcosis after 5 minutes.

The narcosis from O2 statics and O2 dives is from CO2 and O2. O2 is apparently twice as narcotic as nitrogen. CO2 would be vastly more narcotic than either, molecule for molecule.

 

[Simos]

I had a feeling you might have tried something Eric shame about the narcosis on pure o2, could have been an interesting way for us to do long, shallow dives ;-)

I guess nitrox would really help against co2 toxicity and might end up being worse in terms of o2 etc guess I better stick to good old ordinary air
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[Mullins]

Though hyperventilating should reduce narcosis, I haven't found it helps at all. The biggest thing for me has been reducing descent speed. I used to get very narked when I was diving heavy, but I hardly feel it now. It's counterintuitive because I must be producing more CO2 on the descent by diving light - but it has made a huge difference.

 

[tcrusson]

Hi Dave, was it just a matter of removing weights to dive slower overall, or did you also slow down the initial part of the dive and stopped finning earlier?

I reach 20m in 12 to 14 seconds, and then stop finning. My rate of descent is 1.05m/sec on average past 40m. I'm just using a 1Kg neckweight, as I've been diving with a 2mm suit and don't pack - and the Glide fin gets fairly heavy once compressed (I was actually thinking about ditching the neckweight).

I'm wondering if the initial phase of the dive should be done slowly, as it's where the biggest gradient of pressure is experienced.

PS: apparently tech divers learn that a fast descent speed means heavier narcosis, but I couldn't find any explanation as to why. It really looks like we're taking stabs in the dark on the subject of narcosis...

 

[Simos]

Dave/Tanguy, if it helps at all (or if relevant) I do remember reading somewhere (scuba related) that an important factor in reducing narcosis is keeping the descent speed constant. I don't remember all the details but it had to do with the fact that varying descend speeds lead to irregular nitrogen compression...

I haven't really thought this through but could it be that diving lighter leads to a more constant descend speed?
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[Mullins]

That's interesting Simos - I'm not sure if the descent speed would be more regular, I'd have to look at some of my dive profiles.

Tanguy - it was a bit of both. Took some weight off and slowed my kicking down, but I did have to kick deeper before I could glide. My peak descent speed is now fractionally under 1m/s. From memory I was using about 1.5kg neckweight with a 2mm top and lots of packing. It was in the Bahamas though, where the salinity is lower than the Red Sea.

 

[Mullins]

It really looks like we're taking stabs in the dark on the subject of narcosis...

Absolutely. It's really just trial, error and word of mouth for us.

On the subject of darkness and cold water - I find that I rarely get narked in the lake where I train, which is usually 10-15m vis and 20C surface temp / 10C bottom temp. Not freezing, but hardly tropical either. Narcosis used to be a real problem for me (may have cost me a WR) and after experimenting I've found the only significant variables are depth and speed. I remember Martin and/or Kirk K. saying the same thing.

 

[Simos]

A relevant parameter I've seen quoted Dave is stress so it might be that cold and darkness cause stress to most people whereas this is presumably not the case if you are used to training in dark/cold waters...

However, these days stress is quoted as a factor in everything! (easy way out for doctors?) what is likely is that being stressed really does not help in dealing correctly with being narc'd and remaining calm, focussed etc so i guess if you see it this way it is a multiplier effect.

Ps I don't even go deep enough to feel the effect of narcosis I'm prob talking out of my a$$ lol
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[trux]

I checked some documents, and most of them also list factors increasing and reducing the narcosis. The most funny factor increasing narcosis is low intelligence rofl I do not know whether your IQ is identical to the depth you can safely dive, but perhaps we can make some statistics

This is one of the lists:

Factors which tend to increase the effects of narcosis include:
• low intelligence
• fatigue or heavy work
• anxiety, inexperience or apprehension
• cold (hypothermia)
• recent alcohol intake or use of sedative drugs (includes seasickness medications), marijuana etc.
• poor visibility

Factors which tend to reduce the effects of narcosis include:
• strong motivation to perform a given task
• acclimatisation following prolonged or repeated exposures
• tolerance to heavy alcohol intake

The wikipedia article about narcosis offers relatively good starting point with a lot of information. One thing caught my attention there - unlike often considered to be fact that you can get used to narcosis, they tell that scientific evidence does not show that a diver can train to overcome any measure of narcosis at a given depth or become tolerant of it.

 

[tcrusson]

Well, I don't know if going deep with no air and deliberately facing O2 shortage, dirty contractions, and bad narcosis could be the act of a smart person, so we should be sorted on that front

Dave, did you change anything with your training rhythm that you think could have affected narcosis, e.g.: rate at which you increase your depth, more repetition of dives to the same depth, gradual training or on a longer timeframe, etc.?

I did mostly 2 trips to focus on depth, 3 weeks each. On the first one I went from 45 to 71, on the second one a year later from 71 to 91, training every second day and adding 3m each time. If fear is a factor then it would explain why I get hit badly by narcosis, as I went for a PB at every dive... With a short timeframe, so not too much time to build enough confidence.

 

[Kars]

I think the intelligence factor relates to the ability to have rational control over your mind.

I did face a couple of "Oh shit" moments down below 50 in the cold dark waters, but thankfully recognised the 'fear to panic' process and went to the practical thought of doing just my best and see where the chips may fall.

Remembering my deepest cwt dive, 65m in a nice Swedish Fjort, I did not notice narcosis. I did have narcosis when I hit 40m for the first time in freediving, in a cold low visibility Dutch lake.

In regard to your experience at the blue hole in Dahab, not seeing arch and panicking. That's what I refer to an "Oh shit" moment. On such occasion I did recognise the futility of such emotion and reverted to focussing on the things I CAN DO. In your situation I probably would count the blessing of seeing the line, knowing I'm on my way up, and I have a nice swimming pace and speed, watching the rope fly bye.

When it come to factors involved, would the state of you blood be a factor?