on nitrogen narcosis

one of the most insightfull descriptions of nitrogen narcosis i've ever read is here

"The impairment is in perception... awareness... your frame of active attention is diminished!

And that is why it is insidious... you can concentrate and function normally within an ever decreasing circle of awareness and this tricks you into thinking that everything is fine... well it isn't... you are peripherally impaired!

This is not the same as tunnel vision but similar. Think of it in terms of tunnel awareness. That is why you will miss the subtle cues that things are starting to go sideways... little things going wrong that you would be able to pick up on if you were not impaired... and the cascade of failures begins.

You can function almost normally in the center of attention but are unaware that the walls are closing it. The better divers are the ones who can sense what is happening at the earliest stages by first of all knowing the truth about nitrogen narcosis and secondly by noticing what is not perceived... they recognize the holes in awareness... then the need to over-concentrate... finally the difficulty of shifting attention from one task to another... ect.