Question Ever experienced Nitrogen Narcosis?

[boulderjohn]

You just described my experience at the Blue Hole in Santa Rosa, NM. I was one of the first divers in that morning, hanging out and enjoying the crystalline water, when a n00b came hurtling past me, bottom-bound, and smacked the dirt. Aaaand there went the viz for the entire day...

I have seen that happen exactly there.

 

[tomh1972]

johndiver999:
It's more like a bong hit than a beer,

Well, he's not wrong. My experience with narcosis usually amounts to 1) the "wrong" things look inexplicably interesting; and 2) short term memory suffers tremendously (i.e., checking my spg for depth instead of my computer, making a note of it, then a minute later making exactly the same mistake.

 

[johndiver999]

Or looking at the time or air pressure, confirming that they look “ok” but immediately realizing that you failed to actual read or place into short term memory the actual numerical values. You can do it 2 times in a row, while you are swimming fine, controlling buoyancy and ostensibly feel like you are relatively unimpaired and in control of the dive. Being able to recognize, anticipate and ameliorate these effects are some of the coping skills that can apparently be enhanced with practice. For example, on normal dives of 130 ft or less, I will just run my single computer. For dives that are planned significantly deeper, I try to remember to also run the stop watch function on my gshock watch, so I know my elapsed time and have another, simple and independent sanity check on when I should be outta there.

 

[steinbil]

Rapid descent can contribute to CO2 retention, which significantly exacerbates NN. Rapid compression itself "might" also be a contributing factor but would be very hard to quantify. I can't recall experiencing it myself but it is more likely because I am conditioned to breathe deeply and concentrate on deep air dives.

Sorry to dig up an old thread, but in what way does a rapid descent contribute to CO2 retention? I'm interested because of a recent incident I had.

 

[Akimbo]

Sorry to dig up an old thread, but in what way does a rapid descent contribute to CO2 retention? I'm interested because of a recent incident I had.

Rapid descents can (not always) contribute to NN because of exertion compounded by a tendency not to breathe as deeply. I don't know if this tendency somehow relates to a delayed response to CO2's breathing stimulus or increasing PPO2.

This phenomenon is observable when supervising surface-supplied air dives. It is routine for dive supers to monitor the divers breathing over the comms (hard-wire communications system), which is much louder underwater in a hat or FFM. It is not unusual to have to remind experienced military and commercial divers to "ventilate" (breathe deeply and purge the hat) when reaching the bottom. You can often hear their respiration getting unusually shallow.

I first learned this in US Navy First Class Diving School, which was the first step from working air diver to dive super. We never got an explanation of the cause but were trained to look out for it.

I even saw a Master Diver candidate get dinged for not responding fast enough to unusually shallow breathing on descent when being observed during our training. Earning your "Master pin" is (was?) a pretty rigorous performance evaluation, far more than learning additional material.

 

[Fred Tagge]

Narcossis, which can also include the Oxygen in your tank is primarily a function of depth, but a lot of other things come into play as well. How hydrated are you? How much Ethanol did you consume last night, or this morning? Did you get enough sleep last night? Are you still a bit whupped from the first dive? How much work are you having to do during THIS dive (caught in a current, down welling, fighting a heavy job or a big fish?) All of those can cause an increase in your narcosis level that dive or for several dives.
I can recall getting seriously narced at 30 ft after a particularly intense bachelor party, to the point I called off all diving for the day as it seemed any increase in nitrogen partial pressure kicked it in. OTOH I have also been relatively free of the effect at depths of around 150 feet. When spearfishing I normally won't shoot at a large fish beyond 160 feet since past experience has proven to me I am usually narced enough at that depth to miss a kill shot, thus bringing in the heavy workload factor into play.
BTW all of those variables can effect oxygen toxicity too. Narcosis is relatively easy to identify when it gets intense enough but there is quite a wide "safe" window between first effect and life threatening. Oxtox has a much narrower window between "first effect" and can "the body be recovered?" with a much more subtle first effect that varies widely between individual divers, and the onset depth which can vary for the individual diver on any given day.

 

[Akimbo]

I can recall getting seriously narced at 30 ft after a particularly intense bachelor party, to the point I called off all diving for the day as it seemed any increase in nitrogen partial pressure kicked it in.

I have not seen any evidence that NN can be perceptible at such a low pressure. However, excess Carbon Dioxide, which shares many symptoms with NN, can easily occur at 30'/10m.

 

[Belzelbub]

I can recall getting seriously narced at 30 ft after a particularly intense bachelor party, to the point I called off all diving for the day as it seemed any increase in nitrogen partial pressure kicked it in.

I’m sure the hangover you were most likely experiencing had a lot to do with the effect.

 

[GiraffeMarineSalvage]

I wouldn't fully trust a self-assessment of mild nitrogen narcosis, but in a safe and controlled setting it's possible to individually quantify gradation of "how narced are you?" at a given depth with wetnotes and writing answers to simple questions (obvious disclaimer above should be done slowly with experienced support and don't do anything stupid while narced...).
I strive to be very self-aware on every dive but personally the way I would describe it is that it's similar to being drunk in that the gradation between degrees of intoxication is not always readily apparent to the intoxicated person and it may sneak up on you..

 

[Centrals]

My own experiences only:
I have never met anyone admitting narcosis after the dive.
But I have quite a few and would not hide it from my buddy.
It is very difficult to describe the "sensation" because the onset is very subtle and take time to develop to more serious level(tunnel vision once and Wow!). Most importantly is to know your own body and realize what narcosis is all about! I could have the symptom as shallow as 20m on descent especially on the first dive of the trip.
To cut the long story short, this is my routine:
1. Shallow dive on the first dive of the trip. I believe my body needs time to get used to high PPN2.
2. Slow descent. There is no rush even on negative descent.
3. Mentally alert. Good sleep the night before ie. self control on holiday.

Just be careful. It is REAL.