Nitrogen Narcosis - Mathematical Model?

[Bubbletrubble]

@DiveNav: Modeling of the nitrogen narcosis effect in a computer simulation will be difficult. First, you would have to predict the appearance of the effect: at what depth, water temperature, physical exertion level?, gas mix, etc. Second, you would have to represent the effect that narcosis has on cognitive and behavioral performance in the user interface. Third, as others have mentioned, you would have to account for variability in the incidence and magnitude of the nitrogen narcosis effect from diver-to-diver and even from day-to-day for the same diver.

I think you need to ask yourself what you are trying to accomplish by incorporating nitrogen narcosis in your diving simulation software. Are you trying to develop a learning aid for newer divers to become aware of nitrogen narcosis? Or are you attempting to accurately simulate all aspects of a dive, including nitrogen narcosis on deeper dives? I suspect that you will find it easier to develop for the former rather than the latter.

In your computer program, you might be best served to incorporate, at 100+ fsw depths, a random "wonkiness" in visual perception (maybe fuzzing things out on the periphery?), a problem with depth/time info temporarily unreadable/fuzzed out, or maybe a short-lived mapping problem with respect to user-controlled buttons and the actions of those buttons. Although none of these suggestions could ever substitute for actually experiencing narcosis firsthand, it might make for some challenging fun from a user perspective.

For research on nitrogen narcosis, I recommend doing a search for the topic in the Rubicon Foundation Archives.

Good luck and let us know how it turns out...

 

[Matt S.]

Modeling and simulation would be hard because it's so poorly understood.

You may be able to illustrate the effects of narcosis by analyzing enough anecdotes.

 

[DiveNav]

............
I think you need to ask yourself what you are trying to accomplish by incorporating nitrogen narcosis in your diving simulation software. Are you trying to develop a learning aid for newer divers to become aware of nitrogen narcosis? Or are you attempting to accurately simulate all aspects of a dive, including nitrogen narcosis on deeper dives? ......

Both? As much as possible....
At least I would like to accomplish the second.
But, if I can find some good research papers that links somehow nitrogen narcosis to depth, water temperature, gas mix, physical exertion, etc .... then we could have a reasonable model good enough for both

...... Second, you would have to represent the effect that narcosis has on cognitive and behavioral performance in the user interface....[/URL].
I agree.
We do already something similar for the "chill effect" (diver getting cold) by a progression of shaking, blurring and blackout
For the Nitrogen Narcosis were thinking to create a "tunnel vision" effect and maybe add a progressively delayed response to keystrokes.

......Third, as others have mentioned, you would have to account for variability in the incidence and magnitude of the nitrogen narcosis effect from diver-to-diver and even from day-to-day for the same diver....

Agree.
Right now users enter their specific body data (height, weight and sex). From those we derive volume of human body, Surface, BMI and body lean body mass....
If we allow user to also enter age, then we could have quite enough data to account for different type of users.
But, again, I need to find some paper that links that data we have to Nitrogen Narcosis.
Regarding the Day-to-day variability .... we use a probabilistic approach (we do already the same for sensitivity to CNS).

....In your computer program, you might be best served to incorporate, at 100+ fsw depths, a random "wonkiness" in visual perception (maybe fuzzing things out on the periphery?), a problem with depth/time info temporarily unreadable/fuzzed out, or maybe a short-lived mapping problem with respect to user-controlled buttons and the actions of those buttons. Although none of these suggestions could ever substitute for actually experiencing narcosis firsthand, it might make for some challenging fun from a user perspective....

As a last resource we could always do this ... but it will be nicer if we could have some data to back-it up.
I like the "short-lived mapping problem" suggestion

..... For research on nitrogen narcosis, I recommend doing a search for the topic in the Rubicon Foundation Archives....

Thanks. I will check it out

.....Good luck and let us know how it turns out...

Sure. Will let you know.

Alberto

 

[MB]

Interesting... So far I'm reading a lot of replies that say why you can't do this, but far more complex phenomena have been understood by trying to develop or explain a model. This is an interesting question. It is a multivariate problem, so a host of variables will have to be isolated to indicate the relative contribution each might make. I like the question - sure wish I could figure out how to study it.

Given there is variability aross individuals in onset and intensity - seems like the next step would be to establish or assign a value for each of the usual knowns (exertion, temperature, PN2 or depth, etc), then try to set up the ratios of the knowns across a range of typical person-profiles. So now, to get started, you need some empirical literature (not magazine articles) to establish the variance for the known variables. I'm trying to recall a couple of papers... showed that narcosis was a continuum rather than a binary by giving some performance data at the surface, 40', 60' 80', 100', and 120'. If I remember, the performance included both motor and cognitive variables (altho the cognitive tasks were limited to "figure it out" variables rather than judgement scenarios - and that limits the value of the cognitive part of the model).

Neat project. I hope this pans out into something. I'm massaging the brain to see if I can remember where I've read relevant research that might help.:doctor:

 

[DiveNav]

.....So now, to get started, you need some empirical literature (not magazine articles) to establish the variance for the known variables. .....

EXACTLY !!! Research papers (not magazine articles) is what I am looking for

..... I'm trying to recall a couple of papers... showed that narcosis was a continuum rather than a binary by giving some performance data at the surface, 40', 60' 80', 100', and 120'. .......... I'm massaging the brain to see if I can remember where I've read relevant research that might help......

PLEASE .... keep massaging

If it was easy .... it would have been done already. I like challenges.

Alberto

 

[RickI]

In my experience narcosis was highly variable both in terms of depth of onset and severity. If I was in a reduced state, probably better off not diving in hindsight it can setup at a particularly shallow depth. Exertion, fatigue, cold, anxiety, manner of breathing are some of the more obvious variables that can influence expression of narcosis. As it can vary substantially in the individual, it varies even more so among a group of divers. It can be habituated to a degree, still there will be times even with a well experienced diver frequently exposed to narcosis in which early onset can occur.

Given all the variability and as you are talking about a simulator, it might be more practical to ascribe a criteria. Why not start with the old standby, "Martinis Law," it isn't that accurate but it has been around for quite a while. You might even have the diver input weight and use some intoxication index based on weight. You could even apply multiplying factors for experience and exertion. As so much of this is arbitrary, you have some license to make your own assumptions.

I wrote a paper about nitrogen narcosis when I was 18 for a college English class assignment, succession of symptoms, variables influencing severity, mitigation, etc.. It would be a hoot to see it again all these years later. I'll see if I can find it and will scan it and post it.

Have fun!

 

[DiveNav]

Hi RickI,
thank you for the post.

..... Why not start with the old standby, "Martinis Law," it isn't that accurate but it has been around for quite a while. You might even have the diver input weight and use some intoxication index based on weight.....

In the simulator using the diver real weight, height and sex, we build the mathematical model of the diver (buoyancy, Body Fat %, Lean Body Mass, Basic Metabolic Rate).
How the weight of the diver affects the onset of Nitrogen Narcosis?

.... I wrote a paper about nitrogen narcosis when I was 18 for a college English class assignment, succession of symptoms, variables influencing severity, mitigation, etc.. It would be a hoot to see it again all these years later. I'll see if I can find it and will scan it and post it....

Please find it

Alberto

 

[RickI]

You're welcome. As you are putting together the model you have a fair amount of freedom for making assumptions. You could even take a dimensional analysis approach in putting together your model. Regarding a weight correlation to intoxication, there is a lot of work out there on this. You might consider going with a blood alcohol correlation vs. body weight derived from "martini consumption." More at: Blood alcohol content - Wikipedia, the free encyclopedia

It seems there are a variety of interpretations out there about what "Martini's Law" states, i.e. each 33 ft. of descent = 1 martini, each 50 ft. of descent = 1 martini. There are still others. It has been a while since I've had any martinis but recall that saying I would have equivalent narcosis to 2 or worse, 3 dry martinis at 100 ft. is a severe over statement on a "normal" dive. Individual experience factors in again. I've been about blown away at 170 ft. on air when particularly susceptible for a variety of reasons (i.e. lack of recent exposure, physical exertion, foreign setting) and been less impacted at 250 ft. (familiar wall, no current/minimal exertion, excellent visibility) by comparison. At still other times I had intense narcosis merging into O2 toxicity at 265 ft. and 270 ft. again on air at still other times. As all this happened before I turned 20 in the 1970's, claim absolution of the stupidity of youth and the fact that I survived, not to be repeated. Finding a norm will take some thought but after all this is just a model with a credible basis. You could even factor in recent air dives to various depth brackets, say 50 ft. increments in the last 3 to 6 months. Don't want to make this too complicated and yet I guess you are trying to engage the participant in the modeling exercise with a reasonable quantity of realistic variables.

I think the paper is in storage, I will see if I can find it. Came across a worksheet tabulating a bunch of dives in terms of depth - narcosis response that I used in preparing the paper.

Hi RickI,
thank you for the post.



In the simulator using the diver real weight, height and sex, we build the mathematical model of the diver (buoyancy, Body Fat %, Lean Body Mass, Basic Metabolic Rate).
How the weight of the diver affects the onset of Nitrogen Narcosis?



Please find it

Alberto