Too shallow to get narced?

[Scraps]

The Chairman is exactly right.
Aside from meeting the performance requirements, my main mission in teaching the deep dive in the AOW class is to demonstrate to students that they are narced at depth and their cognition is impaired even if they don’t feel it. I want them to know this so they will resolve in their hearts to change the plan of a deep dive only in a more conservative direction. I want to prepare them to reject out of hand any suggestion, regardless of its source, to make it longer or deeper because they know their cognitive impairment disqualifies them to make that decision at depth.

 

[Lorenzoid]

My understanding was that the latest dive science suggests that O2 probably isn't narcotic. See this post by @Dr Simon Mitchell :

Equivalent Air Depth question

Okay so I have a question. I’m currently working towards my ADCI card. (commercial diver card). On the commercial side we use Bimix so HeO2. Why on the TECH or REC side do we use TRIMIX? Wouldn’t it be easier and actually safer to take nitrogen out of the picture? I understand by using...

scubaboard.com

Fascinating experimental stuff. I missed that thread--thanks. It will be interesting to see how all that relates to actually diving with Nitrox.

 

[Bubble99]

Often when descending down to a wreck one descends quite quickly along a line and with the head down, then when at the wreck, pulls head up quite fast - this actually provokes narcosis more easily than if the same diver would descend vertically feet down head up and a bit more slowly, so even if it was not quite 30m - besides the point tha some a re a bit more susceptible than others - this could have contributed even more.
Digging aimlessly in the sand seems to be something quite typically for narcosis at least we learned it in our N3 course and our instructor played exactly that as narcosis scenario for the assisted ascent of narcotic diver exercise. I never noticed this is real but find it very interesting that you describe exactly that.

 

[Compressor]

I appreciate this. This was the first time I had this happen to me. I was well aware of NN, reading and hearing about it, how it feels like being increasingly drunk, but in retrospect, it is amazing how it creeps on you in such an unnoticeable manner. And the sleepiness - that is the part I forgot to mention, but it was a bit dream-like hanging over the wreck now that I think about it.
I think I will enrol in the Nitrox course to mitigate this in the future.

Excellent. A very positive attitude. Nitrox will not eliminate N2 narcosis but it will make your dive less prone to narcosis. Once you replace a portion the N2 in your gas with O2, you will have to keep an eye on N2 and O2. But you will learn about that in that course. But highly recommended course in my opinion.

 

[MaxBottomtime]

The three best ways to avoid narcosis are to breathe helium for deep dives, move slowly and take normal, deep breaths when diving air or nitrox, or take up another hobby. The easiest one is to slow down. Make slow descents, move slowly underwater (don't kick hard, it's not a race), and slow your ascents even more than you think you're making, especially the last fifteen feet. The slow ascents will not only reduce the risk of DCS or embolism, but it will also eliminate the fatigue some divers report.

 

[Eric Sedletzky]

I used to think that I had to go below 100’ to get narced. Even at 100’ I wouldn’t feel narced, there was no indication that I was Impaired. 150’ on air I was impaired for sure and felt it, ears ringing, felt like nitrous oxide.
Then one time we were diving in a rocky area off the Northern California coast, cold water, about 70’, and I got a shot off on a nice lingcod. Strung it up on the hoop, everything seemed fine, until I tried to figure out how to re-set the spear into the gun and re-wind the shooting line. I sat there staring at it drawing a complete blank. This is something I have done hundreds if not thousands of times, and I could not figure it out. This was at a depth that I thought was pretty benign. I ended up just wrapping the spear onto the gun with the loose shooting line and went up to about 40’ to a saddle that was on the rocky pinnacle and judt resting for a moment. Then it all came back to me crystal clear.
A combination of working hard and the excitement of spearing a big fish is what did it.

 

[Belzelbub]

Apparently I was under the wrong impression that reducing nitrogen content would fix the narcosis issue to an extent. I am glad to know it won’t before I tried that. Again SB saves me money, time and useless effort.

I wouldn’t say it’s useless.

Narcosis effects of N2 vs O2 does not exactly appear to be settled science. I’m not an expert, so I’ll just say I don’t know if O2 is as narcotic. I’ve heard arguments on both sides. So, I’m not sure.

Even if O2 is as narcotic as N2, that doesn’t mean that Nitrox is useless. If all your dives ar gas limited, then maybe not. However, in many cases, Nitrox can extend dives, shorten surface intervals, and/or increase safety buffer against DCS.

 

[Kendall Raine]

This is something I have done hundreds if not thousands of times, and I could not figure it out. This was at a depth that I thought was pretty benign.

That's the thing about narcosis. It hits you differently on different days/conditions. It shouldn't (lipid solubility-Meyer Overton-doesn't change), but it does. Stress-thermal (cold)/emotional (e.g. low viz, task loading), excitement, WOB/CO2, exertion, random events can all play in. Science can't even settle the question of narcotic potential of oxygen-it should be but it isn't, maybe. Only thing one can do is recognize it and manage it (e.g. limit depth/ascend, increase helium content, lower exertion, etc.).

 

[Steve Lawson]

Hi there.

So today I was doing my first wreck dive. I loved it immensely and I am going to pursue that further - found it much more exciting than observing reef fish.

One thing that took me by surprise today is the following. As I approached the bottom of the wreck which sits at around 80 feet I suddenly felt lightheaded and weird. There was no fear of depth, as I looked up and saw no surface, but my actions were uncoordinated and in retrospect a bit chaotic - I would approach the same window multiple times, then drop to the bottom and start digging in the sand. Then turn on and off my camera, lose my GoPro and forget to look for it, etc.

My breathing was also getting rapid and shallow, so once I hit 100 bar I signalled to the guide and we began to turn back.

Is it possible I could get narced that shallow? What was that in your opinion. I was perfectly normal as soon as I got to about 65 feet.

For what it’s worth I was diving on regular air.

Attaching some photos just to share my excitement

There are many factors that may contribute to narcosis and many people experience it differently.

Narcosis affects divers like alcohol—you feel fine, but actually experience progressive impairment beginning with the first drink (or couple of atmospheres).

Drinkers function with narcosis better than non-drinkers because they are used to being impaired.

CO2 build up due to exertion will greatly affect narcosis. It’s easy to see why when looking at the degree of narcosis based on gas:

Gas	Relative narcotic potency
He	0.045
Ne	0.3
H2	0.6
N2	1.0
O2	1.7
Ar	2.3
Kr	7.1
CO2	20.0

Note how CO2 is much higher than other gases. A slight increase in CO2 can significantly add to narcosis (and He significantly reducing it).

Narcosis adds to your baseline level of anxiety. If you’re nervous, a new diver or not fully comfortable in the underwater environment, narcosis only compounds one’s anxiety. Despite the tables and physiology being the same, the psychological burden is a contributing factor. For instance, drysuit diving with heavy weights in dark, cold water with low vis is quite different that diving in warm clear water wearing little more than a t-shirt and bathing suit. Experienced divers are more comfortable than newer ones, so the anxiety baseline is less.

Similarly, seasickness medicines, fatigue, drinking alcohol or not getting enough sleep the night before are contributing factors.

 

[tursiops]

There are many factors that may contribute to narcosis and many people experience it differently.

Narcosis affects divers like alcohol—you feel fine, but actually experience progressive impairment beginning with the first drink (or couple of atmospheres).

Drinkers function with narcosis better than non-drinkers because they are used to being impaired.

CO2 build up due to exertion will greatly affect narcosis. It’s easy to see why when looking at the degree of narcosis based on gas:

Gas	Relative narcotic potency
He	0.045
Ne	0.3
H2	0.6
N2	1.0
O2	1.7
Ar	2.3
Kr	7.1
CO2	20.0

Note how CO2 is much higher than other gases. A slight increase in CO2 can significantly add to narcosis (and He significantly reducing it).

Narcosis adds to your baseline level of anxiety. If you’re nervous, a new diver or not fully comfortable in the underwater environment, narcosis only compounds one’s anxiety. Despite the tables and physiology being the same, the psychological burden is a contributing factor. For instance, drysuit diving with heavy weights in dark, cold water with low vis is quite different that diving in warm clear water wearing little more than a t-shirt and bathing suit. Experienced divers are more comfortable than newer ones, so the anxiety baseline is less.

Similarly, seasickness medicines, fatigue, drinking alcohol or not getting enough sleep the night before are contributing factors.

Your table is a restatement of the Meyer-Overton Hypothesis about gas solubility in liquids being the source of narcosis. It is called a Hypothesis because it is not accepted an an explanation, i.e. not yet "proved" to be a theory. If anything, solubility has a very weak correlation to narcotic potential, which is not a "cause."