???Future of Open Circuit Mixed Gas and Rebreather Diving???

[AJ]

Here's for one: Effects of Hyperbaric Nitrogen Narcosis on Cognitive Performance in Recreational air SCUBA Divers: An Auditory Event-related Brain Potentials Study

Although nitrogen narcosis is claimed to be completely reversible within several minutes by ascending to a shallower depth (Emerson, 2002), Balestra et al. (2012) and Germonpré et al. (2017) reported that cognitive impairment continued after surfacing from in-water dives by recreational divers

Article referring to the 30m depth myth: Executive Functions of Divers Are Selectively Impaired at 20-Meter Water Depth

One can somewhat learn to deal with narcotic impairment and you will certainly feel less impaired when ascending. That's where the good advice of ascending comes from. But, although you may feel less impaired you still are and it's good to know that.

Knowing this made me decide to dive CCR and trimix on 30 meter plus dives.

 

[Celt]

Science says otherwise. Narcosis does not go away immediately when you ascend. You may feel less affected when going up, but you're still affected. So please be careful and take it easy when affected seriously.

Immediately may have been the wrong word. But ascending to a shallow depth relieves narcosis was what I meant.

 

[Nick_Radov]

Although nitrogen narcosis is claimed to be completely reversible within several minutes by ascending to a shallower depth (Emerson, 2002), Balestra et al. (2012) and Germonpré et al. (2017) reported that cognitive impairment continued after surfacing from in-water dives by recreational divers

I don't have any hard evidence for this but I suspect some of that residual impairment was due more to hypercapnia than to nitrogen narcosis. CO2 is more narcotic than nitrogen, and once the levels build up it can take a while to clear. The risk of hypercapnia increases with depth due to higher work of breathing, hence the importance of using enough helium to keep the gas density low.

 

[lostsheep]

I don't have any hard evidence for this but I suspect some of that residual impairment was due more to hypercapnia than to nitrogen narcosis. CO2 is more narcotic than nitrogen, and once the levels build up it can take a while to clear. The risk of hypercapnia increases with depth due to higher work of breathing, hence the importance of using enough helium to keep the gas density low.

I want to throw in my personal anecdote here, take it for what it's worth.

CO2 narc feels different than nitrogen narc. CO2 in me starts with a feeling of anxiety, narcosis feels more like I am just slow.

Anybody else?

 

[Nick_Radov]

I want to throw in my personal anecdote here, take it for what it's worth.

CO2 narc feels different than nitrogen narc. CO2 in me starts with a feeling of anxiety, narcosis feels more like I am just slow.

Anybody else?

Yes, I agree. But either gas (nitrogen or CO2) can cause cognitive impairment of the form mentioned in the papers cited by @AJ above.

 

[lostsheep]

On one occasion (and it only took one) I got a CO2 hit from over exertion at depth but I was able to make it stop by really forcing myself to relax, no ascent required. I've never been able to make a nitrogen narc go away without ascending.

 

[berndo]

Here's for one: Effects of Hyperbaric Nitrogen Narcosis on Cognitive Performance in Recreational air SCUBA Divers: An Auditory Event-related Brain Potentials Study

Although nitrogen narcosis is claimed to be completely reversible within several minutes by ascending to a shallower depth (Emerson, 2002), Balestra et al. (2012) and Germonpré et al. (2017) reported that cognitive impairment continued after surfacing from in-water dives by recreational divers

Article referring to the 30m depth myth: Executive Functions of Divers Are Selectively Impaired at 20-Meter Water Depth

One can somewhat learn to deal with narcotic impairment and you will certainly feel less impaired when ascending. That's where the good advice of ascending comes from. But, although you may feel less impaired you still are and it's good to know that.

Knowing this made me decide to dive CCR and trimix on 30 meter plus dives.

When you take 20 people with a median of 61 dives I would expect to see results that show people are hammered in relatively shallow water and more impairment. I already mentioned that some people are really hammered at 30 m. In my experience those tend to be nervous/out of shape/beginner type people. Some people are clearly much more impacted than others. I would be interesting to see a difference between people's scores when comparing people like Celt and a beginner.

CO2 narc feels different than nitrogen narc. CO2 in me starts with a feeling of anxiety, narcosis feels more like I am just slow.

How do you know it's CO2 when in it's dark narc?

 

[Tassi Devil Diver]

Anybody else?

Yes, I get feeling of impending doom, exertion at depth, retention of CO2 brings it on. I have not experienced those feeling for over 10 years, predominantly dive a rebreather with Tx dill for anything over 30m.

 

[lostsheep]

When you take 20 people with a median of 61 dives I would expect to see results that show people are hammered in relatively shallow water and more impairment. I already mentioned that some people are really hammered at 30 m. In my experience those tend to be nervous/out of shape/beginner type people. Some people are clearly much more impacted than others. I would be interesting to see a difference between people's scores when comparing people like Celt and a beginner.


How do you know it's CO2 when in it's dark narc?

I don't understand your question but I'll take a stab at what I think you are asking. The two factors that can be controlled that affect co2 / n2 narc are exertion and depth. When I am really calm and I go deep I get a different feeling than when I am less deep and exert myself. It's not definitive but makes me suspect different gasses are causing the effects.

Yes, I get feeling of impending doom, exertion at depth, retention of CO2 brings it on. I have not experienced those feeling for over 10 years, predominantly dive a rebreather with Tx dill for anything over 30m.

I dive with helium dil for anything beyond about 110' and I have learned my lesson about exertion and the importance of really forcing myself to relax especially at depth when wob and co2 elimination become harder

 

[lukeb]

I want to throw in my personal anecdote here, take it for what it's worth.

CO2 narc feels different than nitrogen narc. CO2 in me starts with a feeling of anxiety, narcosis feels more like I am just slow.

This has been my experience too, I personally have come to notice a big difference between being narced by the depth, or when it is exertion induced at depth and brought on more by CO2 retention. I have learnt I have to go slow and really control my breathing at depth.