Nitrogen Narcosis: What It Is and How It Affects You - Maluku Diving

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Nitrogen Narcosis is such a bad name for this effect. Oxygen is believed to be as narcotic or even more so than nitrogen.

Based on Mayer-Overton theory of lipid solubility. However, that's become less proven in recent years, as 'newer' gasses didn't fit the model.

Also, with O2, we must remember that ppO2 in the brain is decreased due to metabolism. This may explain why narcosis studies of nitrox failed to prove any +/- influence.

What divers often fail to appreciate is the Narcotic potential of CO2.... and how that narcosis presents ('dark narc'). I believe that CO2 narcosis represents a lot of the 'on a given day' narcosis events. Especially when high workload/respiration at the outset of a dive / on the surface is followed by rapid pressurisation (fast descent) and consequently PpCO2 spike.
 
ah, not in RAID. Also not with every dive operator I've used in 4 countries (not a huge sample I'll admit but 100% so far)

The question of how "hard" the limits are on certifications and whether or not an OW diver can go do dives they are not certified for is a different issue. In my case, my life insurance will NOT pay out if I'm killed at 41m if I'm not certified deeper than 40m

From RAID site:
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All my RAID cards have a hard depth limit on them.
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And then I have different limits on my rebreather diving

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Nope. I've done 40m on air. What I'm saying is that if the WKPP and others strongly advocate a max END of 100' then there may be some fire under that smoke. The fact is that narcosis does occur at depths shallower than 150', but individual tolerances etc may vary. To say that someone diving to 130' does not need to be aware of narcosis is IMO just plain wrong.
i guess i should clarify. my PADI OW is good to the recreational limit of 130 feet. And my life insurance and travel insurance companies both agree.

We have never run into any operator issues, but we mostly dive the Caribbean on LOBs. I do realize there are some Florida operators that want to sell me an AOW course...
 
Fair enough. I'm not really familiar with the PADI system of "recommended" depths and how they will affect your insurance etc. I suspect its all about liability in the long run. Also maybe a lot to do with the US aversion to regulation, as far as I know all the non-US agencies put a depth limit on the cards.
 
Is anybody else convinced that narcosis starts shallower than most people think? I have been to almost 150' without a problem but I'm pretty sure that I don't think as clearly at 50' as I do at the surface. The only times I've felt really narced was from CO2 at less than 100'.
 
60 feet? Seriously? Did the laws of physics change since I took classes? Maybe 120 feet but not 60. And probably more like 140 to 160
From my own experiences, 25m to 60m on air.
Depth is NOT the only factor that will trigger narcosis for me.
Quick descend is the worst.
 
Is anybody else convinced that narcosis starts shallower than most people think? I have been to almost 150' without a problem but I'm pretty sure that I don't think as clearly at 50' as I do at the surface. The only times I've felt really narced was from CO2 at less than 100'.

Nitrogen narcosis begins when you leave the surface. It doesn't become significantly debilitating until you reach a depth of 30m/100ft to 40m/130ft.

What confuses people are the signs and symptoms of narcosis. Often these signs and symptoms are incorrectly educated - being focused only on sensations associated with intoxication. These symptoms present in only a very small number of narcosis events, which leads many divers to believe that they aren't experiencing narcosis on their deeper dives.

In fact, nitrogen narcosis is a form of anesthesia, not intoxication. Many of those effects/symptoms are not noticeable to the individual diver. If accompanying divers are equally narc'd, those signs will not be apparent to them either.

The easiest way to appreciate the more insidious effects of narcosis would be to assume you lose IQ. Put simply, you get more stupid as ppN2 rises. As it gets more severe, you lose cognition, memory function and, eventually at extreme depth, you lose consciousness.

Losing IQ... losing intelligence... as depth increases is rarely identifiable by the individual or the (equally compromised) divers around them. You get stupid... you stop processing information... and you're entirely unaware of it.

CO2 narcosis presents slightly differently. Often it is, what divers call, 'Dark Nark'... feelings of anxiety or panic. CO2 narcosis, I believe, is what often presents after a fast descent because any CO2 retention occurring during water entry etc results in a ppCO2 'spike' on rapid pressurization. It hits you as soon as you get deep. I've seen it in action a few times.

Nitrogen narcosis takes longer to present. A study has shown that mental debilitation from nitrogen narcosis occurs progressively over the bottom time.... it 'creeps' up. It is also suggest that it's effect can persist even after ascent.

In the (distant) past I completed some very extreme deep air dives - circa 260-300ft (80-90m). I didn't feel 'intoxicated' on any of those dives and all of the requirements for complex technical dives were achieved without drama. Nonetheless, it required immense mental focus and was reliant on all of the dive skills, procedures and habits being completely ingrained and instinctive. In short, the dives were performed unconsciously, not by intelligence and problem solving.

Interestingly, most of those dives involved considerable post-dive amnesia... it's hard to remember what happened at depth. A team of 8 experienced technical divers using air needed a week to identify and survey a wreck - a task that could be completed in day if using trimix.

Needless to say, those dives were successful as a result of completely ingrained diving competencies, in divers who had thousands of hours practice and practical experience at a high level. However, if anything unexpected had occurred that was beyond the scope of ingrained skill and procedural response, I remain absolutely convinced that achieving a safe resolution would be far from guaranteed. That is why I would never do very deep air dives any more.

To summarize, people who deny they are influenced by narcosis are either in denial, or simply ignorant of how narcosis actually effects them. They are searching for symptoms that only represent a 'tip of the iceberg' in respect to their actual mental impairment. Where those limited symptoms don't present, they incorrectly believe that narcosis is not present.

I learned a lot about narcosis from my history of deep air diving. I also learned a great deal when I switched to making trimix dives. In particular, through two incidents that allowed a direct comparison between compromised and uncompromised mental ability:

1. Diving trimix on a 36m/120ft wreck that I had previously dove for years on air or nitrox. I was shocked at how 'clearly' I could understand the wreck layout when clear-headed on trimix. Despite hundreds of dives on that wreck using air/nitrox, I really hadn't managed to 'put the pieces together' with any significant level of granularity. I had never felt narc'd diving the wreck - but a single dive on trimix demonstrated to me exactly how little information had been absorbed from my eyes to my brain.

2. Diving trimix with an experienced technical diver who was diving air. I dove a 55m/180ft wreck on trimix and was able to observe significant mental impairment in the air diver; a divers who is at a very elite level of technical diving and whom I respect immensely. I'd never noticed any impairment previously, when we had both dived air to those depths. However, once I was uncompromised by narcosis, it was very easy to recognize the severe impairment in my buddy's cognition and faculties.

I take narcosis very seriously nowadays. Yes, it's possible to compensate for narcosis by having very ingrained dive skills and procedures. But there's no way to compensate for narcosis if unexpected or unforeseen events occur that require solutions beyond your ingrain competencies. The more narc'd you are, the less likely you are to resolve your situation safely.

Don't kid yourself that you don't suffer impairment at depth/high ppN2 folks....
 
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Based on Mayer-Overton theory of lipid solubility. However, that's become less proven in recent years, as 'newer' gasses didn't fit the model.

Also, with O2, we must remember that ppO2 in the brain is decreased due to metabolism. This may explain why narcosis studies of nitrox failed to prove any +/- influence.

I'm not sure how you're making those 2 statements, they seem in contradiction to me.

Furthermore, nitrox does reduce N2, therefore, according to one that "doesn't believe in O2 being narcotic", there would necessarily be less narcosis. This, to this day, AFAIK, has not been proven, although it has been tested. Impairment from gas narcosis when breathing air and enriched air nitrox underwater. - PubMed - NCBI
 
I'm not sure how you're making those 2 statements, they seem in contradiction to me.

Furthermore, nitrox does reduce N2, therefore, according to one that "doesn't believe in O2 being narcotic", there would necessarily be less narcosis. This, to this day, AFAIK, has not been proven, although it has been tested. Impairment from gas narcosis when breathing air and enriched air nitrox underwater. - PubMed - NCBI

Oxygen, according to Meyer-Overton is more lipid soluble than nitrogen. However, the anesthetic property of a gas is partial pressure dependent. If we descend in depth, then the partial pressure of respired gasses increases. With inert gasses, the partial pressure of the gas inside the blood/brain will increase to equalization as gas is dissolved into the body. It won't decrease until that gas is respired out of the body, due to super-saturation on ascent.

Gas narcosis in diving isn't merely a product of lipid-solubility (Meyer-Overton), but also determined by the partial pressure of the gas in question - in the brain.

Oxygen isn't an inert gas. It is actively metabolized by the body; especially by the brain. As I understand it, ppO2 in the brain will always be lower than ambient pressure. So, whilst narcotic potential is higher, it's effect on the brain is necessarily lower because of constant reduced partial pressure.

Obviously, we don't expose ourselves to very high partial pressures of oxygen; because of CNS toxicity. For the relatively low ppO2 that divers encounter, the effect of O2 metabolism might be suggested to keep the brain ppO2 (and consequent narcotic effect) of oxygen very minimal.

Thus, Meyer-Overton prove that O2 is more narcotic that nitrogen due to it's higher lipid-solubility. However, the narcotic properties of oxygen differ from other inert gasses in respect to divers, as narcotic effect is driven entirely by elevated gas partial pressures. Oxygen, being a metabolized gas, doesn't elevate absolutely in partial pressure inside the body. When ppO2 is necessarily maintained at a low level, it has resulted in no clear indication of narcotic impairment when studied (as per the trial you referenced).
 
Oxygen, being a metabolized gas, doesn't elevate absolutely in partial pressure inside the body. When ppO2 is necessarily maintained at a low level, it has resulted in no clear indication of narcotic impairment when studied (as per the trial you referenced).

What do you make of the reduced amount of N2 that still results in narcosis in that study?
 

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