Narcosis

[MXGratefulDiver]

Good posts guys

I'll give my example from my AOW course:

My instructor wrote some simple math poblems on a slate, and handed it to me at ~30m. I didn't feel narc'd at all, and had done several dives to similar depths before

The problems were something like this:

23 + 12 + 34 =
27 + 34 + 11 =
18 + 27 + 39 =
41 + 13 + 28 =
16 + 15 + 29 =

Then I had to total the results

Oh, and I also had to write my name backwards

It took me longer than it would've on the surface, but after double checking, I handed the slate back to my instructor, feeling confident I had 'passed' the test

Back on the surface, my instructor gave the slate back to me. I noticed immdiately that I'd gotten one of the sums wrong by a fairly large margin, and also the total was out

So although I felt 'normal' I was in fact narc'd

... and what did all of that teach you? How do you relate what it taught you to your dive planning and execution?

... Bob (Grateful Diver)

 

[MXGratefulDiver]

Here is an excerpt from my AOW material relating to nitrogen narcosis ...

Nitrogen narcosis is not harmful to your body but it can have a strong influence on your diving performance. Narcosis affects everyone on deep dives and everyone is affected differently, especially psychologically. As a general rule it works on your psyche like alcohol does. In terms of diving it can lead to poor decision making or an inability for the diver to recognize or respond to a developing problem before it leads to a worse one. Divers generally agree that you can learn to recognize, anticipate and adapt to the effects of nitrogen narcosis so that your performance isn't as badly impaired. However, this adaptation takes time and exposure to the specific effects of nitrogen narcosis on you. If you or your buddy are being strongly affected by nitrogen narcosis then ascending slightly, 10 feet or more, will significantly reduce the symptoms.

Symptoms of narcosis will generally appear at a given depth, which will vary from diver to diver, and also will vary within the same diver from dive to dive. Generally the symptoms won't get any worse with prolonged exposure if the diver remains at the same depth but will progressively worsen if the diver continues to a deeper depth, or will progressively improve if the diver ascends to a shallower depth.

The chemical processes that cause nitrogen narcosis are not well understood. Nitrogen is considered an inert gas, and doesn't create any chemical reactions in our body. However, some diving scientists believe that the dissolved nitrogen in our body tissues somehow blocks impulses traveling between certain nerves in the brain. What we do know is that nitrogen narcosis reduces our ability to concentrate, and to perceive and respond to problems we might encounter. It should also be noted that oxygen is as narcotic as nitrogen, and that divers who breathe nitrox will have the same tendency toward narcosis as those on air.

The signs and symptoms of nitrogen narcosis have been compared to those experienced by alcohol or general anesthesia. The earliest symptoms affect brain functions such as concentration, memory and judgment. How those effects manifest themselves in the diver will depend on the individual. For example, a diver who is very confident in his or her ability might start feeling a sense of euphoria. But a diver who is not secure with their skills or surroundings may experience a sense of anxiety. In both cases, these symptoms may indirectly cause trouble the former may lead to poor decision-making, while the latter may lead to stress.

As we continue deeper, narcosis starts to affect motor functions. Movement becomes more difficult and coordination is reduced. A diver may experience difficulty reading or interpreting the display on a dive computer or making adjustments for buoyancy control. Furthermore, the diver may develop tunnel vision or have trouble remembering things such as the agreed-upon maximum depth, no-decompression limits, or turnaround pressure. The diver may react slowly to directions or visual cues from a buddy, or make serious errors in judgment that can lead to an accident.

As the diver continues deeper still, symptoms can become even more serious such as hallucinations or even unconsciousness.

When you first begin to experience symptoms of narcosis or recognize signs of it in your dive buddy a prudent thing to do would be to stop your descent and assess your ability to continue. If you feel any anxiety or loss of control or notice the same in your dive buddy ascending to a shallower depth is advisable.

Some divers are more susceptible to narcosis than others. Some divers will not recognize the symptoms in themselves, or will recognize them in their dive buddyÃÔ behavior before the dive buddy realizes that they are narced. Our physical and mental state can have a significant impact not only on our susceptibility to narcosis, but also on how the symptoms manifest themselves. Symptoms can vary within the same diver from dive to dive. Certain factors, however, appear to increase the effects of narcosis. These factors include:

• Inexperience, or a lack of confidence in oneÃÔ abilities
• Fatigue or exertion
• Cold water
• Rapid descent
• Poor visibility
• Carbon dioxide buildup (hypercapnia)
• Task loading

The good news is that narcosis can be managed by the diver. Ascending to a shallower depth will reduce the symptoms progressively as you ascend or will make them go away altogether. However, since narcosis is predominantly a mental disorder, even such things as focusing on your gauges or concentrating on a task will help make the symptoms more manageable. But keep in mind that if you are narced, the chances are very good that your dive buddy will be too. So a prudent thing to do would be to signal to your buddy to ascend a little bit to reduce the effects.

There is some evidence that prolonged exposure to narcosis helps a diver to mentally adapt to its effects. Many deep air divers use the technique of making progressively deeper dives to train themselves to perform under the effects of narcosis. This technique, however, is increasingly going out of favor as divers are learning better alternatives. One of those alternatives is the use of helium mixtures to reduce the level of nitrogen in our breathing mix (and therefore the effects of narcosis). Several scuba training agencies offer classes in the use of trimix for deeper recreational diving.

... Bob (Grateful Diver)

 

[Rhone Man]

I know people get different symptoms of narcosis, and I had always had "euphoric" narc whenever I went deep, and I assumed that would always be the case.

However, the other day I went deeper than normal and for the first time got "paranoid" narc, as well as tunnel vision for good measure.

My instructor said that although someone might have a predisposition to a certain type of narcosis, there is a random element to it all, and the effect can be different every time.

I haven't been deep enough often enough to draw my own conclusions: but going through the paranoid narcs is a lot less fun (although possibly marginally safer) than the euphoric narcs.

 

[boulderjohn]

Thanks, Bob. That is an excellent summary.

This part is one that people rarely consider:

As we continue deeper, narcosis starts to affect motor functions. Movement becomes more difficult and coordination is reduced.

Last week I was on an extended deep dive in cold water. We found an interesting crystal formation on a rock wall and stopped to examine it. I started to drift a little closer to it than I wanted and began to back fin so I could draw back to a safer distance, but my legs were not obeying me. It wasn't like they were going crazy--I just could not get them to do the exact maneuver I wanted. I had to switch to a safer escape strategy to avoid contact with the crystal. I felt perfectly fine otherwise.

 

[solensdotter]

One thing that I missed in this thread, although it hsas been alluded to, is the fact that narcosis can and will also vary from dive to dive. Not just the difference between a "martini effect" and a "paranoid" narc, but also the intensity.

The most narced I have ever felt was on an easy 85' dive. No idea why; it was a sunny day, vis was great, no stress, ... Definitely had a few martinis going, though.

So, in addition to conditions (several people have mentioned darker dives or lack of visual reference), there is also the less quantifiable "what kind of day are you having" physiological factor. Would assume that fatigue, dehydration, and other physical, and perhaps mental, stresses factor in. Perhaps one of our medical experts can provide more info?

 

[textilet]

I dont have enough experience to make definitive statements but here's what I've noticed:
I understand the idea that since oxygen has a narcotic effect similar to nitrogen, replacing some of the partial pressure of nitrogen with a higher PP of Oxygen might in theory be like replacing 4 martinis with two matinis and two shots of tequila. That makes sense to me. I am sure though that whatever narc effect I have felt from dives on EANx is at least distinct from what I feel on air. When I was at Cozumel last month i had the opportunity to dive some of the same sites, day after day under nearly identical conditions. On wall dives to about 90ft I felt a very real difference in perception of small details. Compared to air, diving on EANx 32 was like watching the dive in HD. That in itself may be a result of oxygen narcosis. Its worth noting that i dont feel especially impaired at 90 ft on air OR nitrox, its just that i felt a very real difference on Nitrox. I wonder if anyone else has noticed this difference. And isn't it possible that since nitrogen narcosis sensitivity varies from person to person, that sensitivity to Oxygen vs. Nitrogen narcosis might vary from person to person? that is, couldnt diver A be more likely to feel nitrogen narcosis while diver B might be more likely to feel oxygen narcosis?

 

[bamamedic]

I don't know if the actual "sensitivity" varies from person to person; I think it's the same physiological mechanism. I think that it's more that someone's perception of narcosis is different from another persons perception.

Quoting from my TDI Advanced Nitrox manual, "Narcosis or anesthesia is basically described as the gas dissolving in the fatty substances of cells and mechanically interfering with the nervous system. The amount of narcosis is related to the degree of solubility in those fatty substances. Nitrogen is not the only gas that can be narcotic. The solubility of oxygen closely approximates that of nitrogen and is believed that excess dissolved oxygen also contributes to narcosis. Some divers believe that they have les narcosis when using nitrox, however that may simply be a placebo effect."

According to a really boring GUE video, oxygen is actually more soluble in lipids, and thus may actually be even more narcotic than nitrogen.

However, it's amazing how little is actually known about how the human physiology responds to gasses under pressure.

Even one's perception of narcosis can change from day to day. CO2 buildup and anxiety can also contribute to the feeling of "narcosis". I've done the very same dive, with the very same gas mixture, on the very same day, and felt noticably less "narced" from one dive to the next. It wasn't that I was somehow absorbing less nitrogen; rather, it was that I was more comfortable with the dive, less anxious, and felt less "narced", even though there really wasn't any change to my actual physiology.

Hope this helps!

 

[Kern]

http://www.gap-software.com/staticfiles/hpb-7-rostainfinal-5-31.pdf


http://www.bioportfolio.com/indepth/Inert_Gas_Narcosis.pdf

 

[textilet]

if there was a "thank you very much" button I'd have used it.

 

[textilet]

Those papers deal mostly inert gas narcosis. I wonder if there are any on the narcotic effects of oxygen? The main reason i'd expect a difference between the effects of nitrogen at pressure and those of oxygen at pressure would be that oxygen isn't inert, regardless of its similarity to nitrogen with regard to lipid solubility...any one know of anymore papers on the subject?