Fear Of Narcosis

[Bob DBF]

I read about the martini effect when I started diving but since I was shallow for a long time I didn't experience it. Later I started diving deep, an old Navy diver told me it was crap since you know when you drink, narcosis will surprise you unless you always remember it is waiting for you to f'up so it can make things worse.

I was never told to fear narcosis, just be aware that it does happen and plan accordingly. I started diving when air was the only choice and deep air diving was done as necessary. I still dive air deep, but I don't dive as deep as I once did due to circumstance and age.



Bob
--------------
I may be old, but I'm not dead yet.

 

[drrich2]

Can't keep straight what I learned from PADI OW, AOW & Deep vs. on the forum, so didn't vote. I'd like to find out from more knowledgeable posters if my grasp of nitrogen narcosis is accurate. My understanding of itis along these lines:

1.) 50 feet to 80 feet - detailed testing may well pick up subtle impairment in cognitive function, unlikely to be subjectively noticed or important.

2.) 80 - 100 feet - As above, with more substantial subtle impairment in more people, and this is a range where some sensitive people start noticing it. Important in sensitive people, or coping with a demanding emergency.

3.) 100 - 130 feet - You are narc'd. Testing would likely reveal some impairment in a lot of people. Many can still dive air without subjectively noticing anything in good conditions. But low light, cold water & some current can push you over into significant impairment. You have less capacity for task loading, slowed mentation and diminished capacity to deal with emergencies. Some more than others.

4.) People seem to build resistance to the effect with repetitive diving, but I don't know how quickly this effect comes on, or how long the nitrogen tolerance lasts after you quit diving. Dr. Bill has posted before on his subjective experience deep diving on air regularly, then after a long hiatus, if memory serves.

The symptoms are a concern to me, since they seem so varied and often vague I don't know what to watch for. From what I understand, common symptoms are:

1.) Slowing/dulling of thinking speed and situational awareness. In advanced cases, this can lead to confusion, and a buddy pair diving down around 130 feet on a reef dive, not paying attention to their gauges, unaware of how deep they are or how low their gas is getting.

2.) Intense anxiety attacks, which can quickly remit by ascending as little as 10 or 15 feet. Questions: Since we don't off-gas that fast, why does the anxiety drop so quickly with the modest depth reduction? Are these attacks more likely later in the dive when our bodies are more nitrogen-loaded, nearer NDL, or do they come on earlier, a product of partial pressure of nitrogen independent of tissue nitrogen loading?

Less commonly or at greater depths, it's my understanding that people can get reduced peripheral vision (tunnel vision), ringing in the ears and hallucinations.

Richard.

 

[Nemrod]

2.) Intense anxiety attacks, which can quickly remit by ascending as little as 10 or 15 feet. Questions: Since we don't off-gas that fast, why does the anxiety drop so quickly with the modest depth reduction? Are these attacks more likely later in the dive when our bodies are more nitrogen-loaded, nearer NDL, or do they come on earlier, a product of partial pressure of nitrogen independent of tissue nitrogen loading?

Less commonly or at greater depths, it's my understanding that people can get reduced peripheral vision (tunnel vision), ringing in the ears and hallucinations.

Nitrogen toxicity (narcosis, rapture of the deep) has nothing to do with the Bends and nitrogen loading of tissue. The two are completely unrelated phenomena. Narcosis is an anesthetic effect of nitrogen at pressure, Bends is caused by the saturation of tissue by nitrogen as described by Laws of Partial Pressure and then the formation of bubbles when pressure is reduced, the likelihood of which increases as the tissues become saturated at depth. I really am not up to the complete or best explanation right now, my brain is feeling the effects of alcohol toxicity I do think. Maybe one of our SB physicians can step in, but if you insist, tomorrow.

I am more afraid of the boogie man under my bed than nitrogen narcosis.

N

 

[shoredivr]

Too tired to give a citation, but this reminds me of the study by Tom Mount and somebody else…sorry, Somebody Else, can't remember who you are..…about how telling one group OW divers during their training that they would be severely impaired by narcosis below X feet (maybe 100?) resulted in an inability to perform tasks; the next group was told they would be slightly impaired below X feet, and *were* only slightly impaired; and the third group were told about narcosis, what it was like, but not given any depth and fear information, and they were able to perform tasks with no impairment.

Point being that mental attitude around fear and narcosis resulted in fear and narcosis.

*edit* it's the Milner-Mount study.

 

[Michael Guerrero]

Too tired to give a citation, but this reminds me of the study by Tom Mount and somebody else…sorry, Somebody Else, can't remember who you are..…about how telling one group OW divers during their training that they would be severely impaired by narcosis below X feet (maybe 100?) resulted in an inability to perform tasks; the next group was told they would be slightly impaired below X feet, and *were* only slightly impaired; and the third group were told about narcosis, what it was like, but not given any depth and fear information, and they were able to perform tasks with no impairment.

Point being that mental attitude around fear and narcosis resulted in fear and narcosis.

*edit* it's the Milner-Mount study.

Virtual high-five!

 

[chillyinCanada]

I've often thought it was my familiarity with the martini effect on land that gave me an advantage dealing with narcosis at depth.

 

[Doomnova]

I don't like the wording of all the options. The closest thing to what I have been taught to do is to respect it. I don't fear nitrogen narcosis I do respect its effects. so while" My instructor taught me to be aware of narcosis beyond 130'/40m." is the closest to what I have been taught I I think it should be from all depths as different people are effected in different way and different depth based off what they are doing. Hence its something always to be respected and not feared. I don't like the use of the word fear because of its negative connotations. People tend to be with too much fear about many things and this stops them from trying stuff that can be quite safe (ie diving). That is not to say fearless is a good thing either as that leads to recklessness. A happy medium is a good thing and that leads to respect of the effects or events and to make a rational choice about them.

 

[drrich2]

Nitrogen toxicity (narcosis, rapture of the deep) has nothing to do with the Bends and nitrogen loading of tissue. The two are completely unrelated phenomena.

I realize that the bends are due to bubble formation and attendant damage to tissue (e.g.: by blocking small blood vessels), but nitrogen narcosis is presumably due to a narcotic effect of higher-than-normal nitrogen levels on the brain. So nitrogen build-up in the tissues over time would reasonably be expected to impact that.

Yet I've never seen anybody post to the effect that nitrogen narcosis is more apt to occur later in a long dive, and it's said intense anxiety attacks thought related to it may be relieved by going up in the water column maybe 10 or 15 feet, with the relief coming quickly.

While bubble formation is not the cause of nitrogen narcosis, it seems like nitrogen build-up over time ought to be a factor. Yet doesn't seem to be so much in the real world, just judging from the posts I've seen, and those I don't see.

Richard.