Narcosis, Sudden hit or gradual increase?

[DavidCarleton]

Dear Doc,

I read recently that Nitrogen Narcosis is more of a gradual and cumulative process (i.e. like drinking one Martini on an empty stomache per atmosphere) rather tha a sudden hit occuring at approx 100 feet (per my NASDS open water class).

Which of the two cases is closer to reality?

 

[blacknet]

Hello,

In my experience I would say it can be both depending upon the case. I.e. gas switching it may hit you at once vs gradual with one gas.

Ed

 

[Dr Deco]

Dear David:

With anesthetic gases that are poorly soluble (e.g., nitrogen or nitrous oxide), the onset is quite rapid, as is recovery. For the more soluble anesthetics (ether and chloroform), onset and recovery is slow (It requires a long time for the anesthetic concentration to build up in the tissues). The onset of narcosis with nitrogen would be fast. Now, the depth of narcosis might well alter your perception on it, and it might appear to have a slow onset. This would be especially true if you were to perform a slow descent from, say, fifty feet to 100 feet.

Narcosis for recreational limits is not generally all too great for most divers. This is not the case for deep (technical) diving. The story of the deep excursion in The Last Dive is very sad.

Dr Deco