Nitrogen Narcosis

[Bubbletrubble]

While we don't truly understand the mechanics of narcosis, we do know that psychology plays a significant role in how effectively it's dealt with ... people who are insecure in their skills or lacking the experience to have adapted to dealing with it typically won't handle it well, regardless of the severity of physical effects. The majority of casual or recreational divers would fall into this category.

To add a little bit to NWGratefulDiver's thought and DCBC's experiences, it's entirely possible that the mechanism of narcosis in scuba diving is amenable to some type of neurophysiological adaptation occurring at a cellular or subcellular level. We already have a few ideas about how learning and memory occurs in neural networks. It doesn't take too much imagination to come up with ways in which repetitive exposures may "desensitize" a person to the effects of narcosis, e.g., "pruning" of excitatory/inhibitory inputs, increase/decrease expression of certain ion channels, activation of certain signal transduction pathways, modulation of transcription factor activity, etc.

 

[watboy]

Nitrox does decrease the effects of nitrogen narcosis...but it does increase the effects of oxygen narcosis, making it a wash. At least according to my nitrox manual (pg 19, padi enriched air diving). Yes, semantics...

i've been telling people I enjoy diving for the calm, relaxed yet focused, zen like state it puts me in. When really, its just a high... one that could be more efficiently induced with a beer.

Nitrox does not decrease the effects of Nitrogen Narcosis. Many people think that it does, but in reality it does not. People that say they have never been under the effects of Nitrogen Narcosis either don't understand the physiological effects of diving, or they have never dived. Brian, go back to your Nitrox manual and re-read that section.

 

[SDAnderson]

To add a little bit to NWGratefulDiver's thought and DCBC's experiences, it's entirely possible that the mechanism of narcosis in scuba diving is amenable to some type of neurophysiological adaptation occurring at a cellular or subcellular level. We already have a few ideas about how learning and memory occurs in neural networks. It doesn't take too much imagination to come up with ways in which repetitive exposures may "desensitize" a person to the effects of narcosis, e.g., "pruning" of excitatory/inhibitory inputs, increase/decrease expression of certain ion channels, activation of certain signal transduction pathways, modulation of transcription factor activity, etc.

A healthy imagination often comes up with ideas that don't hold up to further scrutiny. Many experienced divers will tell you they have learned to handle narcosis or that it doesn't affect them anymore. I've seen a bunch of them in a chamber and watched how they react - it's usually very entertaining.

 

[DCBC]

A healthy imagination often comes up with ideas that don't hold up to further scrutiny. Many experienced divers will tell you they have learned to handle narcosis or that it doesn't affect them anymore. I've seen a bunch of them in a chamber and watched how they react - it's usually very entertaining.

Experience is without question a mitigating factor in how narcosis affects the diver. Improved performance as a result of experience is accepted within the commercial and hyperbaric communities (as well as with recreational divers who have gained considerable experience using "deep air").

 

[DCBC]

Nitrox does decrease the effects of nitrogen narcosis...but it does increase the effects of oxygen narcosis, making it a wash. At least according to my nitrox manual (pg 19, padi enriched air diving).

Your right, nitrogen narcosis is directly related to PN2. Personally, I don't believe that O2 Narcosis exists. If it did, why would a diver experiencing Oxtox not feel any narcotic effect? There are however mysteries that are not understood; especially the role of CO2 in Inert Gas Narcosis.

 

[Bubbletrubble]

Experience is without question a mitigating factor in how narcosis affects the diver. Improved performance as a result of experience is accepted within the commercial and hyperbaric communities (as well as with recreational divers who have gained considerable experience using "deep air").

@DCBC: The phrase "without question" conveys an impressive certainty.

What do you think of this 1995 study by Hamilton et al.? A serial choice-reaction time task showed no significant adaptation (above and beyond typical learning) over the course of the 5 day experiment...yet the divers' self-assessment of their performance revealed perceived improvement. Figures 1 and 2 tell an interesting story.

 

[Bubbletrubble]

A healthy imagination often comes up with ideas that don't hold up to further scrutiny.

What a pessimistic attitude! :geek:

Fortune favors the prepared mind. -- Louis Pasteur

 

[Diver0001]

@Diver0001: The issue of whether narcosis starts at shallow depths is relevant to the question posed by the OP. The question was: "When does narcosis begin?" I interpreted the question to be: "At what depth (or ambient pressure), do the effects of narcosis manifest?" I think others approached the question similarly. I agree, however, that the distinction between mild/barely detectable effect and severe/significant impairment is of great practical importance.

That's all I was trying to say. In my experience, although I'm sure Wayne is right about it being measureable, the risk most divers run from narcosis shallower than about 30 metres is pretty small. I'm sure there will be some cases of people getting badly narced shallower but I wouldn't expect them to be in the 95% part of the curve.

Deeper than 30, however, and the risk posed by narcosis seems to grow fairly quickly. In my mind there really are two zones. I know PADI defines deep as 18 metres or deeper but my subjective feeling about it is that deep starts at about 30 and it's for this reason.

R..

 

[DCBC]

@DCBC: What do you think of this 1995 study by Hamilton et al.? A serial choice-reaction time task showed no significant adaptation (above and beyond typical learning) over the course of the 5 day experiment...yet the divers' self-assessment of their performance revealed perceived improvement. Figures 1 and 2 tell an interesting story.

The this study tested "eleven very experienced Navy divers from DCIEM" (many members of my old team no doubt). There is no comparison between these very experienced divers and inexperienced ones.

The only mention of this is on page 47 of this study. The author states "The strong adaptation effect observed in the present study contrasts with the unreliable effect observed by Hamilton et al (7). This difference could be explained by the substitution of experienced divers for inexperienced non-divers..... we favor the experienced hypothesis..." Improved performance was observed after day 3.

Table one shows a definite drop in the number of errors as the test proceeded. On the last two days the error rate started to increase. This may have been caused by the divers getting bored of the tests (perhaps it was the end of the week and they were looking forward to Beer call).

 

[gcbryan]

Like most subjects, I think the two sides start to agree if you take it far enough. One side says that you don't adapt to narcosis. The other side says that with experience you do somewhat.

One side says that sure, for something that you're practiced you might be OK but what about the novel, unexpected situation.

The other side could well respond that if you have enough experience there is very little that you haven't experienced already.

The same outcome simply viewed differently by the two sides.