How To Experience Narcosis With Minimal Risk?

[chrisch]

Narcosis affects you gradually like getting drunk. The more narked you are the less you notice it or care about it. A chamber "dive" is safe and a good way to see what 50m is like on air. In the water it cannot be "safe" by definition as you are functioning at an impaired level. In practice it can hit you hard in cold dark water at shallower depths than in clear warm water. The actual depth is not the only issue therefore. The more you dive and the deeper you dive the more your body learns to deal with it. So the "effects" can be very different each time. You don't really detect it and cannot really make a decision to stop the dive so easily.

The real best way to handle nitrogen narcosis is not to get it in the first place. Think of it like going round a corner fast in a car. In wet conditions or with a poor quality tire you skid. Pushing the car to it's limits to "feel" the limit has to be done every time the road/weather/tire/car/driver changes. Much better to slow down a bit and stay safe. Get into a skid and it might be okay or you might have a wreck.

If you want to dive beyond 40m (130foot) then put a little helium in the mix. There are plenty of training courses like IANTD ART that allow you to do that.

 

[Jim Lapenta]

For some people the tests on a deep dive in AOW that involve a lock, puzzle, or math problem are not very indicative of the level of narcosis. For one thing, you know it's coming, you know what it will be and, if only subconsciously, you are preparing and maybe even rehearsing it. As a result your focus is on that task and some may even be able to do it faster.

When I wrote my Advanced Level 3 course (what SEI calls AOW) I wanted to avoid this issue. So rather than games, puzzles, etc. I chose to use actual dive tasks to gauge the response. The key word is tasks, plural, not one thing for them to focus on.

This is how I conduct the deep dive of the class.
1. Descend to 50 ft and drop our stage bottles
2. Continue descent to 90-100 ft.
3. At 100 ft. do a quick pressure gauge check and verify everyone is ok
4. Tie off a reel and do a swim out with one buddy manning the reel. The other is concentrating on staying with them and communicating.
5. At the turn point the reel handler will pass the reel to their buddy who will bring us back to the tie off.
6. The handler will untie the reel and secure it, hand it off to their buddy who will hand it to me.
7. Make the sign for ascent to 50 ft to retrieve the stage bottles.
8. As we start the ascent I give the out of air sign to them. The first one to donate will do an air share ascent with me to 70 ft while the other one maintains touch contact with both of us.
9. At 70 I will ask the other to donate to me while original donor maintains contact.
10. At 50 we deploy the stage bottles and do a simulated deco stop to the surface.

Steps 4,5, and 6 are where narcosis seems to be the most pronounced. They don't know exactly when the hand off will occur or the OOA. Since this is done in our Northeast locations, at 90 ft it is in many cases like a night dive. It's dark, they need to use lights, it may be cold, and they may be in drysuits or 7 mils.

So all of this is going on along with the reel task loading when I signal the OOA and time the response, or in some cases the lack of one.

In case anyone is wondering what happens if I have 4 students, the answer is I don't. I take no more than 2 people on the deep dive. Ever.

As a human being with only two hands more than 2 to 1 is an unsafe ratio for a deep dive on the AOW course in my opinion. I used to have an exception if the divers had proven that they were damn good and then I would only take three. One of which would be my buddy.

However I have since decided to drop that as too much risk. If there is another person on the dive with us that person is my buddy and will be very well trained and not a student. Preferably they would be another person with tech experience or the equivalent.

Off the top of my head there are perhaps 5 people I normally dive with that I'd be ok with. 3 are instructors and the other 2 have rescue and solo certs.

 

[Bennno]

Why do you drop the stage in OW? Why would you even bring a stage for a dive to 100'?

 

[guruboy]

I think he said to simulate a deco stop.

 

[Jim Lapenta]

Pony may have been a better choice of words but because it is a redundant air supply and this is about learning new skills. Securing and retrieving the bottle are part of the task loading I put into the course. Students carry the bottle on all dives in the course. I don't teach a typical AOW class.
I have seen students take AOW, hear about pony bottles, then go out and buy one with zero training and experience. This gives them the experience should they decide to get one later on.
When they leave my class they have ALL the necessary skills to do the dives they have just experienced along with detailed knowledge.
I won't offer a "taste" or "tour" of advanced dives. IMO it's unsafe to do that, it insults the students intelligence, it demeans me as an educator, and if it is going to give them access to advanced dives, to do any less than I do is unethical.

 

[Rich Keller]

The chamber is the best way to go safely. While you are there do an O2 tolerance test as well if you dive nitrox.

 

[claymore]

I find being narced has a lot to do with the conditions of the dive. Warm water with lots of light and good vis tends to have less of the stressfull narcs. Dark or low/no vis and cold water can make for a lot more stressfull narc.

 

[lowviz]

I find being narced has a lot to do with the conditions of the dive. ...//...

For sure.

I'll probably get some flak for this, but forget the chamber if you want the real experience. Doesn't have to be all that deep, either. Just make sure that you are being watched by someone who can handle a "situation".

The link below may appear to be a bit off-topic, but it isn't. I was right properly narced on that bitterly cold and low visibility dive and I knew it. Everything came at me in slo-mo.

How women measure up as divers compared to men

 

[tursiops]

Pony may have been a better choice of words but because it is a redundant air supply and this is about learning new skills. Securing and retrieving the bottle are part of the task loading I put into the course. Students carry the bottle on all dives in the course. I don't teach a typical AOW class.
I have seen students take AOW, hear about pony bottles, then go out and buy one with zero training and experience. This gives them the experience should they decide to get one later on.
When they leave my class they have ALL the necessary skills to do the dives they have just experienced along with detailed knowledge.
I won't offer a "taste" or "tour" of advanced dives. IMO it's unsafe to do that, it insults the students intelligence, it demeans me as an educator, and if it is going to give them access to advanced dives, to do any less than I do is unethical.

Jim, it does not seem like a good idea or good muscle memory to have someone carry a pony on a deep dive, but drop it at 50 ft, and do the deep part of the dive without the access to the pony. That misses the point entirely of a redundant gas supply on a deep dive. Sure, I understand you want them to be task-loaded on the dive, but dropping your redundant gas does not seem like the right task. Any why do it at 50 ft? Where is the narcosis involvement at 50 ft? Bottom line: ponys do not get dropped, they get carried. Stages? That's different, but ought to come later. Jeez, it is just AOW....not AN/DP!

 

[tursiops]

I once took three students on the PADI Deep Specialty dive #3 (130 ft) in Bonaire, in front of Buddy Dive. Our task was to settle out and hover at 130 (over about a 140 ft bottom), do our mandatory timed-task, but also to turn around, face the deep water, and see how many garden eels we could count in 2 minutes, while holding hover. After we'd done the simulated emergency deco stop and surfaced, as part of the debrief, I asked "How many eels did you count?" One guy said, "At least 200; I counted 20 in a little square, and estimated at least 10 such squares were visible." The lady said, "At least 150; I just counted until I ran out of time." The other guy said, "What garden eels?"

I'm like the third student; my narcosis typically consists of feeling like it is hard to focus, but then finding it really hard afterwards to remember any of the dive. At 184 ft on air, I dived a really cool wreck, or so I was told. Later, when I did the same dive on trimix, I saw it was a really cool wreck.

I'm not sure how this would have come across on a chamber dive.

On the other hand, I did do a chamber dive for LOW pressures with the Navy while qualifying to ride a P-3 for some science work. We went up to altitude and took off our oxygen masks, for a max of 4 minutes. The hypoxia really got me, as it did the others. We lost cognitive and physical functions, but thought we were just fine until we saw the video afterwards. I had no idea during the exercise.