Nitrogen Narcosis

[Karel26]

Hello fellow bubble blowers. .

When i did my AOW course, my instructor asked me and my dive buddy
when does narcisis start. . I gave him my answer and he said i was his
second student in over 10 years who got the qeustion right. .

So my qeustion to you are when does narcosis start? ? :think:

Happy and safe diving Karel. .

[captain]

When does being drunk begin, when you drink the first drink. Narcosis begins when you take your first breath underwater, but just like being drunk when you begin to recognize its effects varies.

[AfterDark]

When does being drunk begin, when you drink the first drink. Narcosis begins when you take your first breath underwater, but just like being drunk when you begin to recognize its effects varies.

Like he said. The accepted depth where most divers start feel it and begin to have trouble is >100fsw

[BDSC]

The captain got it right.

[Walter]

He usually does.

[Bubbletrubble]

The smart-a$$ answer to your question is...no one really knows.

Being able to answer the question accurately presumes that we have a reliable, reproducible method for measuring narcosis in the first place. A separate but related issue is that we don't even know the precise mechanism responsible for the phenomenon. We know that it's correlated with the increased solubility of inert gas in body tissues at an elevated ambient pressure. We think it might have something to do with inert gas dissolving into neuronal membranes and interfering with electrical signaling from neuron-to-neuron.

I'd say that captain's answer is probably the most conservative answer one could give. It was likely the answer that your instructor was looking for. Hopefully, your instructor went on to discuss the common symptoms of narcosis and the "usual" depths at which it becomes noticeable. It can be observed in some individuals at relatively shallow depths, but it almost always becomes more conspicuous at depths in the range of 100 fsw.

[DCBC]

The narcotic effects of nitrogen begin at pressures exceeding atmospheric pressure. In other words, immediately upon descent.

[scubamountaingirl]

that is one reason we all feel so good when we dive :)

i say this tonuge in cheek. I know its a serious problem when out of control.

ww

[Bubbletrubble]

The narcotic effects of nitrogen begin at pressures exceeding atmospheric pressure. In other words, immediately upon descent.
@DCBC: Are you sure about this? (This should stimulate some discussion. :D )

[laurin]

@DCBC: Are you sure about this? (This should stimulate some discussion. :D )

Change in strategy of solving psychological tests:... [Undersea Hyperb Med. 2003] - PubMed result (http://www.ncbi.nlm.nih.gov/pubmed/14756232)

AFAIK there are multiple studies supporting this along with common sense.

HTH. Narcosis doesn't just appear out of nowhere @4atm, it starts shallow and just gets worse at depth...

//LN

[BDSC]

While nitrogen may begin to build immediately in the tissues upon descent, I would not agree that the narcotic effect takes place immediately.

[Bubbletrubble]

Change in strategy of solving psychological tests:... [Undersea Hyperb Med. 2003] - PubMed result (http://www.ncbi.nlm.nih.gov/pubmed/14756232)

AFAIK there are multiple studies supporting this along with common sense.

HTH. Narcosis doesn't just appear out of nowhere @4atm, it starts shallow and just gets worse at depth...

I read the abstract of your citation. In the study, the 15 divers (breathing air) were given a battery of psychomotor tests at pressures of 1, 2, 3, and 4 bars. Results indicated impaired performance on a subset of the tests from 2 to 4 bars, which presumably correlated more impairment with greater ambient pressure (not sure about this because I couldn't read the full paper).

The results of the study suggest that there is some detectable impairment when comparing 1 bar to 2 bar. No tests were conducted between these two pressures.

I guess that's my point. We really don't know the "threshold pressure" at which nitrogen narcosis manifests. Due to the variable nature of the condition, it would be hard to prove that it occurs immediately upon descent from the surface.

What is "common sense" anyway? If it's an opinion shared by many, then it has little do with what is accurate or correct.

[DCBC]

@DCBC: Are you sure about this? (This should stimulate some discussion. :D )

I can only speak from my personal experience and agree that it may generate some discussion. ;)

At DCIEM, I was involved in extensive hyperbaric (dry and wet) testing to determine the parameters of inert gas narcosis. Upon completion, the Researchers believed that the potential for narcosis existed as soon as the diver begins to descend.

There were measurable differences in most divers at 33 FSW (some at 10'). These same divers did not usually recognize the first symptoms of narcosis until 100 FSW. Clearly they were affected by it long before they recognized that they were being affected.

As you know, divers have varying levels of susceptibility; this varies day-to-day and in different conditions. Although the DCIEM testing was extensive, it only had a small control group.

The U.S. Navy has also tested this with similar results. They found that a definite alteration in thinking skills occurred when divers reached 33 feet FSW. I believe it's reasonable to conclude that the process starts upon descent.

[Bubbletrubble]

@DCBC: Thank you for sharing your personal experience. I'm glad that the US Navy and DCIEM are doing that type of testing. It challenges the notion that narcosis only manifests at a depth of about 100 fsw.

I think it's very instructive to note that cognitive skills may be impaired at depths as shallow as 33 fsw. I wouldn't be surprised if some subtle impairment were detected at even shallower depths.

Another interesting point you raise is the diminished self-awareness that obscures one's recognition of the narcotic effect.

As a side note, I think that the question posed by Karel26's AOW instructor...was a stroke of genius. I can't think of a better way to introduce the concept in a class format. What a great way to stimulate discussion!

[M_Bipartitus]

Is there any evidence that no narcotic effects are present at 1atm? It's easy to say that the effect starts at elevated pressures, but are the mechanisms of nitrogen narcosis present at any concentration of Inert gas? Stated another way, are we always under some miniscule amount of narcosis, even on the surface? I suspect it would be difficult to ever measure if that were the case.

(just for discussion, I'm not making any claims)

[HEFFAY]

We're all narc'd right now.... at 1 atmosphere (assuming we're close to sea level)

[DCBC]

Is there any evidence that no narcotic effects are present at 1atm?

Interesting point! It would explain many of my inabilities... ;)

[DCBC]

@DCBC: I think that the question posed by Karel26's AOW instructor...was a stroke of genius. I can't think of a better way to introduce the concept in a class format. What a great way to stimulate discussion!

The following question is on the ACUC diver examination: When does the narcotic effects of nitrogen start to occur? The correct answer is "Immediately upon descent."

[Bubbletrubble]

Is there any evidence that no narcotic effects are present at 1atm? It's easy to say that the effect starts at elevated pressures, but are the mechanisms of nitrogen narcosis present at any concentration of Inert gas? Stated another way, are we always under some miniscule amount of narcosis, even on the surface? I suspect it would be difficult to ever measure if that were the case.

I guess it all depends on how you define presence/absence of the "narcotic effect." By convention, with respect to nitrogen narcosis, normal cognitive/psychomotor functioning occurs at 1 atm. This forms the comparative baseline.

Is it possible that having a lower level of inert gas dissolved in one's tissues might result in measurably improved cognitive/psychomotor testing? Sure, why not? Anything's possible. Likely? Not sure about that. ;)

[Bubbletrubble]

The following question is on the ACUC diver examination: When does the narcotic effects of nitrogen start to occur? The correct answer is "Immediately upon descent."
This may be one of those cases which distinguishes the answer sought by the examiners (or whoever constructed the test) from an answer that is evidence-based.

I'd take issue with that answer, but that's just me. :D

At the very least, the "correct" answer on the ACUC test is the most conservative one...and cannot be faulted for urging students to dive more safely, eh?

[DCBC]

At the very least, the "correct" answer on the ACUC test is the most conservative one...and cannot be faulted for urging students to dive more safely, eh?

That's my take on it as well. My youngest son stopped me on his AOW "deep water dive" and gave me a thumbs-up because he didn't like the feeling at 80'. I think that if a diver knows that it will affect him, they will be more inclined to be cautious when it comes to depth.

If I'd taught my son's class that nitrogen narcosis started at 100', he may well have continued, shrugging it off as an impossibility. It took him a couple of dives before he felt comfortable in deep water. Its been my experience that small steps are far better than giant steps when it comes to diving. :-)

[reefraff]

For what it's worth, I've been on quite a few chamber rides in a multi-man chamber packed with 10 - 15 divers at a time. In all of those dry dives, it has been my observation that everyone is showing signs of narcosis by the time we hit 3 ATA. Some folks a little shallower but nobody holds out past 70 feet. This doesn't mean that everyone is falling down stupid at 70 feet - they aren't - but their emotions and motor control are noticeably affected.

Sensible divers will assume they are narked long before they feel any signs of it.

[roturner]

There were measurable differences in most divers at 33 FSW (some at 10'). These same divers did not usually recognize the first symptoms of narcosis until 100 FSW. Clearly they were affected by it long before they recognized that they were being affected.



That's my experience too but it doesn't strike me as particularly relevant if it starts at the surface or not. Performance being "measureably" affected isn't the same as being "significantly" affected. I'd probably be measureably affected with one sip of wine but I"m not significantly affected until I've had a lot more. I'm significantly affected on most days at about 30 metres.

On another note, the narcosis seems to get worse a lot faster from 30 meters and deeper. The difference between 0 and 20 metres is a lot less significant than the difference between 30 and 50 metres.

Was there anything in the study that seemed to indicate that the effect gets exponentially worse? That's what it seems like.

R..

[knotical]

Is it possible that having a lower level of inert gas dissolved in one's tissues might result in measurably improved cognitive/psychomotor testing? Sure, why not? Anything's possible. Likely? Not sure about that. ;)
Right on ! I know I got smarter when I moved to Colorado. ;)

[DCBC]

That's my experience too but it doesn't strike me as particularly relevant if it starts at the surface or not. Performance being "measureably" affected isn't the same as being "significantly" affected. I'd probably be measureably affected with one sip of wine but I"m not significantly affected until I've had a lot more. I'm significantly affected on most days at about 30 metres.

To put this into context, a person's performance is dependent upon the situation. Keep in-mind that if you are diving with a buddy and if s/he requires your assistance, the affects of narcosis are compounded. Your buddy will react more slowly (even if this is only "measurably") AND you will react more slowly (than normal) as well.

How long in seconds is too long? Again this depends upon the nature of the problem. In some cases the extra seconds may be too long.

Was there anything in the study that seemed to indicate that the effect gets exponentially worse? That's what it seems like.

Performance decreases with depth. In one test we compared two sets of 3rd year medical students from the University of Toronto. We ran the first test in a similar way as the one previously described, to a depth of 150'.

The second group had foreknowledge of the fact that the nitrogen would lower their performance. They were asked to be serious, concentrate and be deliberate in their thought process from the moment of their descent. The overall results showed the second group to have a marked increase in performance (almost 20%).

We compared these results with 6 experienced Navy divers. The 150' results of these divers showed a performance increase of approx 50% over the second group, and almost 80% better than the first group.

We later joked about the fact that we would all be considered geniuses if the earth's atmospheric pressure ever increased. :-) Experience dealing with narcosis and familiarity with the environment were credited with the increased results.

Again these results are of limited value, in-that the numbers of those tested were small (26). It does demonstrate however why I feel that divers going deep should prepare themselves mentally and first gain several hundred hours of diving experience.

[NWGratefulDiver]

To put this into context, a person's performance is dependent upon the situation. Keep in-mind that if you are diving with a buddy and if s/he requires your assistance, the affects of narcosis are compounded. Your buddy will react more slowly (even if this is only "measurably") AND you will react more slowly (than normal) as well.

How long in seconds is too long? Again this depends upon the nature of the problem. In some cases the extra seconds may be too long.


To put that in different terms, depending on circumstances it may take you longer to recognize that there's a problem, it may take you longer to decide what to do about it, and it may take you longer to implement the solution you decide on. It's also possible that in an impaired condition you will decide on a course of action that may not be the one you would have chosen had you not been impaired. And, as noted, because your buddy is also narc'ed you may not be getting helpful responses from him or her to deal with the situation.

Most scuba accidents are not the result of one thing going wrong, but rather a series of cascading failures that were not recognized or handled at a point where the accident could have been avoided. Narcosis significantly increases the risks of that cascading series of events taking place.

Performance decreases with depth. In one test we compared two sets of 3rd year medical students from the University of Toronto. We ran the first test in a similar way as the one previously described, to a depth of 150'.

The second group had foreknowledge of the fact that the nitrogen would lower their performance. They were asked to be serious, concentrate and be deliberate in their thought process from the moment of their descent. The overall results showed the second group to have a marked increase in performance (almost 20%).

We compared these results with 6 experienced Navy divers. The 150' results of these divers showed a performance increase of approx 50% over the second group, and almost 80% better than the first group.

We later joked about the fact that we would all be considered geniuses if the earth's atmospheric pressure ever increased. :-) Experience dealing with narcosis and familiarity with the environment were credited with the increased results.

Again these results are of limited value, in-that the numbers of those tested were small (26). It does demonstrate however why I feel that divers going deep should prepare themselves mentally and first gain several hundred hours of diving experience.

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.

... Bob (Grateful Diver)

[Brian Sharpe]

For what it's worth, I've been on quite a few chamber rides in a multi-man chamber packed with 10 - 15 divers at a time. In all of those dry dives, it has been my observation that everyone is showing signs of narcosis by the time we hit 3 ATA. Some folks a little shallower but nobody holds out past 70 feet. This doesn't mean that everyone is falling down stupid at 70 feet - they aren't - but their emotions and motor control are noticeably affected.

Sensible divers will assume they are narked long before they feel any signs of it.

A little OT but a compelling argument in favour of using nitrox.:acid:

[Bubbletrubble]

That's my experience too but it doesn't strike me as particularly relevant if it starts at the surface or not. Performance being "measureably" affected isn't the same as being "significantly" affected. I'd probably be measureably affected with one sip of wine but I"m not significantly affected until I've had a lot more. I'm significantly affected on most days at about 30 metres.

@roturner: 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.
For what it's worth, I've been on quite a few chamber rides in a multi-man chamber packed with 10 - 15 divers at a time. In all of those dry dives, it has been my observation that everyone is showing signs of narcosis by the time we hit 3 ATA. Some folks a little shallower but nobody holds out past 70 feet. This doesn't mean that everyone is falling down stupid at 70 feet - they aren't - but their emotions and motor control are noticeably affected.

Sensible divers will assume they are narked long before they feel any signs of it.
A little OT but a compelling argument in favour of using nitrox.:acid:
@Brian Sharpe: Are you sure about that? Please explain what you mean by this. It is, in fact, quite relevant to the topic. (This should spark more good discussion. :D )

[DennisW]

A little OT but a compelling argument in favour of using nitrox.:acid:

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.

[NWGratefulDiver]

A little OT but a compelling argument in favour of using nitrox.:acid:

I have not, personally, experienced any noticeable difference in the degree of narcosis I feel on nitrox, as compared to just breathing air at the same depth. Both air and EAN30 will typically put me at a "whoa!" point at around 120 ... how much of that is due to the expectation of it happening I can't really say ...

... Bob (Grateful Diver)

[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.

[reefraff]

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. (http://archive.rubicon-foundation.org/dspace/handle/123456789/2199)? 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

[roturner]

@roturner: 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. (http://archive.rubicon-foundation.org/dspace/handle/123456789/2199)? 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.

[DCBC]

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.

I don't really think that anyone disagrees with the statement that experience is a mitigating factor when it comes to nitrogen narcosis. This has long been accepted by the hyperbaric research community, the military and the commercial diving industry. I don't see two sides here. :-)

[Garth]

there is something that has bit me from scuba, im wondering if narcosis is it?

.. at first I wanted to see the reefs and fish, .. now I just love being underwater however cold, or visable the environment is. Its possible the good feeling I feel when i'm under water is related to this discussion but as for now I've only been below 100' a handfull of times.

thanks everybody

[Bubbletrubble]

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). :-)
@DCBC: (Sorry I didn't reply to this yesterday.)

Regardless of whether the diver is experienced or inexperienced, his performance in the reaction test will be worse at depth. What is open for debate is whether the reaction test is a good objective measure for narcosis. One could also criticize the study for being too small (not many subjects).

To clarify, the authors discuss adaptation within two separate contexts: the objective serial choice-response time test AND the subjective measures consisting of a global magnitude estimate (How narc'ed do I think I am?), work capability adjectives (Am I able to concentrate? Am I able to work hard? Am I alert?), and body sensation adjectives (Am I uninhibited? Am I dreamy? Am I intoxicated?).

Adaptation (beyond the expected learning from repeating the task) was not observed in the objective measure. However, it was observed in the subjective measures of global magnitude estimate and body sensation adjectives. It's interesting to note that the divers in this study seemed to be aware that their ability to accomplish a task was impaired at depth -- this is evidenced by no adaptation occurring in the work capability adjectives. The authors point out that perhaps the experience of the divers in this study was what made this task-oriented self-awareness possible.

In the discussion (pg. 47), the authors mention the contrasting findings of the 1992 study by Hamilton et al. because it used inexperienced non-divers and, unlike the current study, showed adaptation in the work capability adjective measure. The authors suggest that experienced divers simply have better self-awareness than non-divers when it comes to gauging how narcosis affects their work. I think that's a reasonable statement. It's pretty interesting that despite having this self-awareness as it relates to task-related work...the experienced divers still thought that they weren't quite as narc'ed with each successive day (represented by the global magnitude estimate trending down over time). The authors conclude that the experienced divers could be mistaking waning body sensation changes for "behavioral" adaptation to narcosis. In other words, the divers were probably thinking: "I don't feel quite as narc'ed now, so I must be adapting to narcosis."

Unfortunately, the authors failed to investigate the effect of whether the divers were looking forward to beer call. Huge mistake IMO. Canadians love their beer, eh? ;)

Hope this clears up a few things...

[roturner]

@DCBC: (Sorry I didn't reply to this yesterday.)

Regardless of whether the diver is experienced or inexperienced, his performance in the reaction test will be worse at depth.
...

Ok.... so..... just translating this into ga-ga-goo-goo: People thought things were getting easier but the people watching them couldn't see any improvement, right?

If that's the case then you can't argue with it, I guess. A fact is a fact. But man-o-man am I surprised.

If I make a series of say 10 deep dives over a short period of time, by the time dive 10 happens I don't feel the narcosis nearly as much as by the first dive. I could swear that I've adapted. Maybe not in terms of what it's doing to my body. I believe that part stays the same, but I could swear that I "got used to it". To be honest, I'd be very surprised to hear that my performance on dive 10 isn't any better than it is on dive 1. I would have even put money on it.

R..

[Bubbletrubble]

Ok.... so..... just translating this into ga-ga-goo-goo: People thought things were getting easier but the people watching them couldn't see any improvement, right?

If that's the case then you can't argue with it, I guess. A fact is a fact. But man-o-man am I surprised.

If I make a series of say 10 deep dives over a short period of time, by the time dive 10 happens I don't feel the narcosis nearly as much as by the first dive. I could swear that I've adapted. Maybe not in terms of what it's doing to my body. I believe that part stays the same, but I could swear that I "got used to it". To be honest, I'd be very surprised to hear that my performance on dive 10 isn't any better than it is on dive 1. I would have even put money on it.

A few points that might be helpful...

If you do a repetitive task at 150 fsw or at 10 fsw, you'll improve a little over time. See Figure 1 -- with each successive day, a small but measurable improvement is seen as represented by slightly shorter response times at each depth.
Over time, with this reaction-based test, performance on Day 5 at 150 fsw improved enough to be about equal to performance on Day 1 at 10 fsw. However, this is not evidence of adaptation to narcosis. It is only evidence of learning.
Other studies show similar results. It's important to note what objective test is used in comparing studies, though. One study used a "standing-steadiness task" (whatever that is), which is different from the serial choice-reaction time task used in this study.

So what would be evidence of adaptation? Well, in this study, in Figure 1, we would expect the slope of the performance line at 150 fsw to be steeper than the slope of the trials conducted at 10 fsw. That's not the case, though. The slopes are similar.

What's confusing is the distinction between "adaptation" and "learning."

To summarize:
In this study, over time, the experienced divers thought they were less narc'ed with regard to "body sensation" but they did have an awareness that their "work capability" was still impaired. Results of the reaction test confirm that they were still impaired.

The take-home message is:
We probably can't trust our subjective assessment of adaptation to narcosis.

Hope this clarifies things a little...

[roturner]

Er.... yeah. Summary: adaptation is a myth.

R..

[Bubbletrubble]

@roturner: To apply this knowledge to your previous example...
If you did 10 deep dives over a short period of time, by the time you do Dive #10, you probably won't feel as narc'ed, but your performance on reaction-based tests will still show impairment.

[DCBC]

@DCBC: Regardless of whether the diver is experienced or inexperienced, his performance in the reaction test will be worse at depth.

Thanks for the response. I might best describe what I'm trying to say, by using an analogy:

STUDY 1 (as presented by DCBC)

Group 1

A group of non-drinkers were tested to see how Beer affected them. This group was instructed to relax and enjoy the experience. Their performance was tested. The results after 2 Beers: X, after 6 Beers: Y, after 12 Beers: Z

Group 2

A group of non-drinkers were tested to see how Beer affected them. This group was instructed to concentrate and remain in their seats. Their performance was tested. The results after 2 Beers: F, after 6 Beers: G, after 12 Beers: H

Group 3

A group of Navy drunks were tested to see how Beer affected them. No additional instruction was given. Their performance was tested. The results after 2 Beers: A, after 6 Beers: B, after 12 Beers: C

Study 1 Findings

1. The performance of all Groups was reduced as alcohol consumption increased.

2. The performance of non-drinkers in Group 1 was lower than non-drinkers in Group 2.

3. The performance of the Navy drunks in Group 3 was much better than both Groups 1 and 2.

Study 1 Observations

1. Group 3 performed to satisfactory standards after 12 beers.

2. Researcher's believe that the increased performance of the NAVY drunks in Group 3 was attributable to the fact that they were more accustomed to alcohol and better able to cope with its debilitating effects.

3. It was observed that the NAVY drunks were eager to finish the testing so they could go to the Bar for more Beer.


Study 2 (as presented by Bubbletrubble)

Results on file.


The results of study 1 and study 2 were never compared.


The performance of all people is reduced when subjected to inert gas narcosis. This is without question. It is also without question, that the performance of diver's experienced with nitrogen narcosis is better than those who are not experienced in dealing with its effects.


Unfortunately, the authors failed to investigate the effect of whether the divers were looking forward to beer call. Huge mistake IMO. Canadians love their beer, eh? ;)


Absolutely; even when Canadians try to come up with an analogy, they cannot help but talk about Beer. ;)

[roturner]

@roturner: To apply this knowledge to your previous example...
If you did 10 deep dives over a short period of time, by the time you do Dive #10, you probably won't feel as narc'ed, but your performance on reaction-based tests will still show impairment.

I get it.... equal impariment, check.

Surprising.

R..

[Bubbletrubble]

@DCBC: BTW, I want to say that I found your study design very entertaining. When I was in college, one of my roommates was a Psych major who wrote his thesis on the effects of alcohol consumption on the perception of pain. We all got paid to drink, have a weight pressed against a thumbnail, and rate how much pain we were in. Then we all went to a local bar and made a$$es of ourselves. Afterwards, another roommate of mine proposed writing his thesis on the effects of alcohol consumption on the perception of beauty (beer-goggling). Good times! :)

[-]That being said, it probably isn't fair to compare inert gas narcosis to alcohol intoxication. For all intents and purposes, they are two separate beasts. When you drink alcohol, that alcohol is broken down by liver enzymes. We know that experienced alcohol drinkers have upregulated expression of the liver enzymes that break down alcohol. Moreover, there is probably a desensitization which occurs in brain cells that makes an experienced drinker feel less buzzed when his brain is exposed to the same amount of blood alcohol. These two effects are actually forms of adaptation. It explains why a naive tea-totaler might get hammered by one glass of wine whereas an alcoholic might not feel buzzed at all after drinking that same glass of wine.[/-]

Based on what I've read, there doesn't appear to be adaptation for reaction-based tests in inert gas narcosis.

If your personal experience suggests that adaptation might occur, I'm not saying that's wrong. I'm just saying that your subjective assessment might not be the best indicator of adaptation, since it's easy to confuse learning with adaptation. I think the door's still open for the possibility of adaptation...especially in tasks that are unrelated to reaction time.

[DCBC]

Bubbletrubble, you're discussing an individual's measurable performance decrease when dealing with nitrogen narcosis in repetitive dives over a five day period. I'm discussing how performance for these tasks are increased through years of experience dealing with nitrogen narcosis.

[DCBC]

I think it's unfair to compare inert gas narcosis to alcohol intoxication.

As I mentioned, this was an analogy of testing that was undertaken and I had previously described. I'm aware that drunkenness and nitrogen narcosis are different.

If your personal experience suggests that adaptation might occur, I'm not saying that's wrong. I'm just saying that your subjective assessment might not be the best indicator of adaptation, since it's easy to confuse learning with adaptation. I think the door's still open for the possibility of adaptation...especially in tasks that are unrelated to reaction time.

I have been involved in many hyperbaric tests over the years (not subjective assessments). Not all of these are in electronic format, nor are all available on the Internet. I would also not expect that all of them would be made available to the public sector. I think I've described my experiences.

Notwithstanding peer reviewed journals, there are things that are commonly known by many people. Several people have experienced themselves becoming more accustomed to nitrogen narcosis. Historically divers increased their depth over time and were able to accomplish jobs like underwater welding at ever increasing depths. Individuals that understood their inability to complete a task eventually gave way to something that was doable for them.

If this is not your experience, I understand. Safe diving.

Wayne

[Bubbletrubble]

Bubbletrubble, you're discussing an individual's measurable performance decrease when dealing with nitrogen narcosis in repetitive dives over a five day period. I'm discussing how performance for these tasks are increased through years of experience dealing with nitrogen narcosis.
It really depends on what kind of tasks you're talking about. If those tasks are heavily reaction-based, then even an experienced diver will still be impaired. AFAIK, one cannot increase his reaction time through practice.

With regard to adaptation to narcosis, perhaps the commercial diving community is focused on performance in tasks that do not rely on reaction time.

I am completely ignorant about what a commercial diver does. I can only draw conclusions based on what's been published.
Are most/any of your under water tasks reaction-based?
Could under water welding be considered a reaction-based task?
I suspect that deep sea welding is something that one can practice. If so, then I can definitely see the value in doing deep dives to acquire that skill.

[roturner]

So you mean that the tests were done using tasks requiring high levels of reactive action?

That's not like diving at all.

A good test for diving would be to test divers for slower reaction times while engaged in walking meditation.

That's the problem with comparing apples with oranges. You can conclude whatever you want to see .....

R..

[Bubbletrubble]

@roturner: Wait a sec. Did you read the paper? Read the Methods section for a description of the reaction-time task.

I'm only interpreting what was in the article.

Of course, one can argue that a different type of task might not yield the same results.

FWIW, I do think that reaction time is relevant to sport diving.

Consider the following scenario: You are at 150 fsw, and your buddy has an entanglement issue at that depth. Do you think that the time it takes for you to recognize and resolve the situation will be longer or shorter than if you had experienced the same situation at 10 feet? To isolate the depth variable, let's assume that all other things are equal (light, temperature, can't surface to get help, gear, distance between divers, etc.). I'm not offering this as proof...just that reaction time may be relevant to sport diving under certain circumstances.

[Bubbletrubble]

DCBC and roturner, I owe you guys a beer. :)

[roturner]

DCBC and roturner, I owe you guys a beer. :)

Can't object to that, eh? :beerchug:

As for your scenario.... yeah. I understand that it's the internet and we can always invent a scenario that can't be handled and I would fully agree with you that nobody wants to die gruesomely.

On the other hand, maybe one of the things that separates highly experienced divers from teh ones who "die gruesomely" is their ability to recognise danger (despite, in the case of narcosis, their depth) and the handle that adequately. (ie. situational awareness).

I think you said before that the tests are relevant. But they are not. They measure the wrong variable. They need to measure judgement (or common sense) and situational awareness and not just pure choice reaction time.

The latter (what they measured) is like measuring calculation speed.

The former (what I'm saying) is measuring making the *right* calculations.

The difference is that someone making the wrong decision quickly isn't as effective as a diver as someone who makes the right decision but takes 10 seconds longer. Hardly anything happens during diving that is so threatening and immediate that "calculation speed" is the determining factor for survival. 99.99998% of situations require the *right* decision, not the *fastest* decision.

R..

[Bubbletrubble]

I didn't say that reaction time is the only important variable in effecting a rescue. I also didn't say that it was the most important factor in effecting a rescue. I stand by my statement that it does contribute to resolving the situation.

Of course, good judgment, planning, training, experience, situational awareness, and many other things go into making the rescue in the given scenario. Something to consider is that some or all of those things might be impaired simultaneously along with reaction time.

Reaction time is easy to measure. It's quantifiable and was known to be affected by narcosis. That's why it was used in the study in question.

I realize that we all want a simple, clear-cut answer. Unfortunately, this rarely happens in science.

If one read the article, it would probably be incorrect to conclude that adaptation to narcosis is a myth. It's probably better to phrase it as follows: "The findings of the study suggest that reaction-based tasks do not show adaptation in the context of inert gas narcosis." After all, adaptation can occur in many different kinds of tasks. And not all of those tasks were tested.

It's up to the reader to decide the relevance of the study to sport and/or commercial diving. I would hope that people would take a look at the methodology and understand the limitations of the findings.

Is it happy hour yet?

[DCBC]

Are most/any of your under water tasks reaction-based? Could under water welding be considered a reaction-based task? I suspect that deep sea welding is something that one can practice. If so, then I can definitely see the value in doing deep dives to acquire that skill.

Yes. In this example, the diver has to maintain control of the torch, in-that he doesn't cut his umbilical, support lines, a piece of his equipment, or his leg. You often work in high current and varying visibility and have to react to unplanned movement or loss of vision. The commercial diver works in a construction site which is fraught with hazards over and above the "diving aspects" of the job.

When communicating topside, the diver may have to give moment-by-moment information to a crane operator which involves movement of a load that presents a potential danger to the diver or the construction being undertaken. Setting or removing explosive charges is another action that requires a high degree of diver situational awareness. As does hot tapping a natural gas line. Not a lot of room for error. :-)

[DCBC]

I agree with Roturner. In the military and commercial field if nitrogen narcosis is a factor, it's understood that the performance of the diver will be degraded. Through increased experience and exposure, the goal is to increase situational awareness and improve the decision making process.

The area of recognition of nitrogen narcosis isn't stressed enough in sport diving imo. The time it takes to react to a situation may be decreased by preparation.

One example is an inexperienced "driver" sees a red light, realizes he's close to the intersection and slams on his brakes (the reaction time is the time it takes him to recognize the problem and move his foot off the gas pedal to the brake).

An experienced "driver" pays more attention to the light as it cycles and can predict that it will turn red. He may have to brake as well, but his "critical reaction time" has been eliminated. This is a result of experience.

I think a diver who's attuned to himself, his equipment and the environment is better prepared to deal with a situation than another diver who's caught by surprise, or never knew what hit him until it was too late.

[gbray]

wow, I think that I just proved that nitrogen narcosis does occur at 1ATA. My reaction time to interpret these results just went from very quickly after reading the first page of response to a near drunkenness state after reading six pages of responses. I'm glad I wasn't operating heavy equipment while reading this.:D

I'm wondering if nitrogen narcosis compounded or complimented the drunk navy divers condition mentioned earlier.

Seriously though armed with all this information what exactly should I as a fairly new diver do with it? I don't see how it will change any of my diving protocol. Knowing that the monster is out there watching me either makes me continue to dive with indifference to it, dive paranoid of it, or stay out of the water. I sure don't intend on staying out of the water.

[wedivebc]

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.

I agree with this statement about O2 narcosis but at the same time I believe that since oxygen comprises a relatively smaller percentage of a breathing mix at least at a depth where narcosis is noticeable by divers that the concept of oxygen reducing narcosis is moot.

[Bubbletrubble]

Seriously though armed with all this information what exactly should I as a fairly new diver do with it? I don't see how it will change any of my diving protocol. Knowing that the monster is out there watching me either makes me continue to dive with indifference to it, dive paranoid of it, or stay out of the water. I sure don't intend on staying out of the water.
I agree with Roturner. In the military and commercial field if nitrogen narcosis is a factor, it's understood that the performance of the diver will be degraded. Through increased experience and exposure, the goal is to increase situational awareness and improve the decision making process.

The area of recognition of nitrogen narcosis isn't stressed enough in sport diving imo. The time it takes to react to a situation may be decreased by preparation.

One example is an inexperienced "driver" sees a red light, realizes he's close to the intersection and slams on his brakes (the reaction time is the time it takes him to recognize the problem and move his foot off the gas pedal to the brake).

An experienced "driver" pays more attention to the light as it cycles and can predict that it will turn red. He may have to brake as well, but his "critical reaction time" has been eliminated. This is a result of experience.

I think a diver who's attuned to himself, his equipment and the environment is better prepared to deal with a situation than another diver who's caught by surprise, or never knew what hit him until it was too late.
@gbray: I think Wayne's last post is very insightful. His driving analogy highlights the advantages of experience.

We can all agree that certain aspects of our reaction time or our cognitive ability are significantly degraded by narcosis at depth. There may or may not be some physiological adaptation which occurs over repetitive deep exposures with respect to those measures. Gaining experience allows the diver to increase his awareness of the effect, anticipate it, and plan his responses accordingly.

If there's stuff that you want to see at 100+ fsw, then I'd recommend gradually extending your depth limits. Take a deep diving course to learn about the risks of deep air diving, narcosis, gas management, and exposure protection issues. Learn about decompression procedures. Master buoyancy control. Dive with a responsible buddy team and practice safety skills. Learn about the advantages and disadvantages of helium-containing breathing mixes.

It all boils down to managing the risks. If you do the things mentioned above, then you have significantly decreased the chance that something bad will happen during your deep dive. If you are an overweighted novice diver with an insta-buddy who decides to do a bounce dive to 160 fsw in cold, dark water while using an AL80...then the chance that something bad will happen is significantly higher.

[RikRaeder]

Hello fellow bubble blowers. .

When i did my AOW course, my instructor asked me and my dive buddy
when does narcisis start. . I gave him my answer and he said i was his
second student in over 10 years who got the qeustion right. .

So my qeustion to you are when does narcosis start? ? :think:

Happy and safe diving Karel. .

Narcicis starts when he looks into the pool and sees his own reflection. Or perhaps that's when he finishes...I'm not much for philosophy...or am I...?

[wedivebc]

A group of Navy drunks were tested to see how Beer affected them. No additional instruction was given. Their performance was tested. The results after 2 Beers: A, after 6 Beers: B, after 12 Beers: C


I was part of that study and group C ended up back at the ship with really ugly dates

[gbray]

Very nice summary Bubbletrubble. Thank you

[DCBC]

I was part of that study and group C ended up back at the ship with really ugly dates

They may have been ugly, but the beauty of Beer is that:

1. They don't look ugly at the time; or

2. You don't really care. LOL

[NWGratefulDiver]

I was part of that study and group C ended up back at the ship with really ugly dates

I believe, Dave, the conclusion was "I never went to bed with an ugly woman ... but I sure woke up with a few" ... :shocked2:

... Bob (Grateful Diver)

[Valhalla]

I should know this question by now but are post dive headaches & slight nausea indicative of nitrogen narcosis or CO2build-up or possiably both?

[Valhalla]

I was part of that study and group C ended up back at the ship with really ugly dates


At 10:00pm she was a 2 but at 2:00am she was a 10...Old but still funny IMO...:)

[oren413]

at 30msw/100fsw the partial pressure of the nitrogen we breathe is 3.2.. assuming breathing 20/80 air... other than that its physiological differences in people that effects when exactly it happens

[wedivebc]

I should know this question by now but are post dive headaches & slight nausea indicative of nitrogen narcosis or CO2build-up or possiably both?
Classic CO2 symptoms. But CO2 is believed to intensify narcosis symptoms.

[DCBC]

I should know this question by now but are post dive headaches & slight nausea indicative of nitrogen narcosis or CO2build-up or possiably both?

Post-dive headaches and nausea are not factors of nitrogen narcosis, as once the increased PN2 is reduced, all narcosis symptoms disappear before the diver reaches the surface. As has been mentioned, this sounds like an increase in CO2, resulting most likely from poor ventilation.

Carbon Dioxide levels can increase the severity of narcosis at depth in a similar way as cold water temperature, anxiety (largely due to cold water and poor visibility), rapid descent (which causes a momentary CO2 build-up), and fatigue.

[OneBoatNut]

No the discussion was started as a fellow diver asked me what would be the issue with a bounce dive to 220?
I have had many deep dives and he was asking the possible dangers, I wanted to advise him that it isn’t the Partial Pressure that is the danger (at least not at 1.6) it is the narcosis and to attempt anything you are not trained for is risky at best.
I said along with training you must be in good shape as physiology is a great factor in many things on a dive.
Also adipose cells can harbor more micro-bubbles and being overweight doesn’t help.
Not that overweight divers shouldn’t dive so don’t get offensive if you are over weight, it is a fact cardio is a major factor in any activity.
Also the more efficient the cardio vascular system the more efficient off gassing.

Anyways my thoughts were on narcosis and getting in shape will increase your capabilities should the need arise.

[DCBC]

...my thoughts were on narcosis and getting in shape will increase your capabilities should the need arise.

I agree that divers should keep in-shape. Fitness reduces a diver's chance/severity of DCS and provides him/her with enhanced physical ability in the event of an emergency.

I don't believe that the weight of an individual is a reliable indicator of cardiovascular fitness. It's true that these often go together, but people can have one without the other.

Unless you're referring to a working diver, excellent cardiovascular fitness offers no protection against narcosis.

[DiveNav]

.....Unless you're referring to a working diver, excellent cardiovascular fitness offers no protection against narcosis....

To reverse this .... does diver fitness level affects - or not - Nitrogen Narcosis ?

AM (aka eDiver)

[DCBC]

To reverse this .... does diver fitness level affects - or not - Nitrogen Narcosis ?

As I understand it, the mechanics behind nitrogen narcosis is largely unknown and there are many theories that have manifested themselves over the years. One theory is that when the PPN2 increases, the nerve transmissions are altered in various areas of the brain which result in the presence of gas molecules that have been dissolved in the nerve cell's fatty membranes causing narcosis.

If a diver works hard, it is believed that increased gas is manifested in the nerve cell's fatty membranes causing nitrogen narcosis symptoms to intensify. A working diver's fitness is felt to be a mitigating factor. It's worthy of mention that light work has not intensified the narcotic affect. At least this has not been the case from my personal experience.

As an aside, it has long been accepted that hard work at depth results in gas pockets being formed (believed to be the result of a vacuum effect caused by tendon use) which has contributed to decompression sickness. The commercial diving and military sectors factor this into the appropriate decompression profile. Fitness is a mitigating factor and high fitness is expected when using U.S. Navy and DCIEM military tables. If your not a Navy SEAL, give yourself lots of leeway. :-)