I don't notice it much in warm water but I've definitely had some short term memory loss at 100' in cold, dark Lake George.
Nitrox: Narcosis myth?
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DevonDiver
N/A
I don't believe I've ever seen a study that linked narcosis to temperature (or visibility?).
It does make me wonder whether there could be a link between core body temp and narcosis. Seems unlikely, as brain temp shouldn't (??) vary on the dive... if it did, you'd have more to worry about than narcosis, surely?
I doubt whether water clarity has ANY physiological impact. It may, however, have a psychological impact... possibly via placebo effect.
In regards to amnesia... this was very common back in the days I was wreck hunting in the Gulf of Thailand. Trimix wasn't readily available then, so deep air in the 60-90m range was usual.
On the deeper wrecks, multiple teams of divers took days to establish basic layouts etc... as very little information was retained by the time you surfaced. If it wasn't recorded on a slate, it generally wasn't remembered.
It took literally dozens of dives to achieve what could have been done in a single dive on trimix.
I doubt these effects occur even rarely within recreational ranges. At least, not via nitrogen partial pressures. I suspect that CO2 narcosis is actually to blame for many reported 'severe' narcosis events where ppN otherwise remains less than 4.
Nonetheless, if we assume a bell curve of susceptibility, there might be a small percentage of divers who do actually succumb to severe symptomatic narcosis within relatively benign inert gas partial pressures.
I'd suggest that frequency was much lower than stories suggest.
I'd also suggest that the placebo effect was rife in respect to reports of 'severe' narcosis symptoms.... whereas instances of narcosis degradation without severe symptoms (diver is compromised, but unaware or without perceptible symptoms) tend to be under-reported.
More: Nitrogen Narcosis - Perceptions of Susceptibility
It does make me wonder whether there could be a link between core body temp and narcosis. Seems unlikely, as brain temp shouldn't (??) vary on the dive... if it did, you'd have more to worry about than narcosis, surely?
I doubt whether water clarity has ANY physiological impact. It may, however, have a psychological impact... possibly via placebo effect.
In regards to amnesia... this was very common back in the days I was wreck hunting in the Gulf of Thailand. Trimix wasn't readily available then, so deep air in the 60-90m range was usual.
On the deeper wrecks, multiple teams of divers took days to establish basic layouts etc... as very little information was retained by the time you surfaced. If it wasn't recorded on a slate, it generally wasn't remembered.
It took literally dozens of dives to achieve what could have been done in a single dive on trimix.
I doubt these effects occur even rarely within recreational ranges. At least, not via nitrogen partial pressures. I suspect that CO2 narcosis is actually to blame for many reported 'severe' narcosis events where ppN otherwise remains less than 4.
Nonetheless, if we assume a bell curve of susceptibility, there might be a small percentage of divers who do actually succumb to severe symptomatic narcosis within relatively benign inert gas partial pressures.
I'd suggest that frequency was much lower than stories suggest.
I'd also suggest that the placebo effect was rife in respect to reports of 'severe' narcosis symptoms.... whereas instances of narcosis degradation without severe symptoms (diver is compromised, but unaware or without perceptible symptoms) tend to be under-reported.
More: Nitrogen Narcosis - Perceptions of Susceptibility
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Your thoughts mirror mine. It also supports my belief of why in trimix they include the O2 in the END
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Tassi Devil Diver
Contributor
But those factors can increase anxiety resulting in increased respiration and CO2 related issues which is very much linked to narcosis.
From my experience, 20 plus years of diving in cool temperate waters, there are two types of narcosis. First, the happy euphoric feeling one gets on deep air dives in good conditions that is bright, good vis, no current, where everything is going well and you are having a great dive. Second, the horrible feelings of impending doom I associate with exertion at depth, increased anxiety due to poor vis dark cold conditions, gear issues all leading to increased respiration rate. The first I associate with nitrogen narcosis, those happy euphoric feelings, the second I associate with narcosis more influenced by CO2 caused by the increased respiration rates due to exertion and or anxiety. The first can rapidly lead to the later should something happen that leads to an increase in respiration rate and the dive can go downhill quickly from there.
As I started to dive deeper I experienced the euphoric narcosis then from time to time the feelings of impending doom, these experience unnerved me, it took me sometime to associate these horrible feelings with CO2. Once I established the link with CO2 I altered my dive plan better to suit the conditions. Later I then went and did trimix training and got a rebreather and now for me narcosis is a thing of the past but I am still always vigilant to avoiding any sort of exertion at depth where I can and reduce any stress associated with a particular dive that may bring on anxiety.
DevonDiver
N/A
So the problem is anxiety... a psychological factor... not temperature... a physiological factor.
Aren't we supposed to dive within our comfort zone? This is the remedy for anxiety.
I do agree. CO2 narcosis presents differently, I believe, to nitrogen narcosis. CO2 narcosis also presents much quicker... near immediately. Which makes sense as CO2 will be produced directly in the brain as oxygen is metabolised.
Wheras nitrogen narcosis is suggested (by studies) to present more gradually as the dive progresses (and is suggested to persist on ascent).... which makes sense as we know that nitrogen takes time to diffuse into (and out of) our system.
DevonDiver
N/A
Also bear in mind that oxygen is metabolized. So the ppO2 in the brain will be lower than ambient pressure should dictate. PPO2 would be 'somewhere' dictated by FO2; between .21 and .18 depending on where you measured it.
The question raised in my mind is that:
Nitrogen is a CNS suppressant (?)... causing narcosis at elevated ppN.
Oxygen is a CNS stimulant (?).... causing toxicity at elevated ppO2.
There has been some suggestion that the physiological effects of these gases under hyperbaric conditions tend to counter-act each other. The nitrogen (narcosis) suppresses somewhat the CNS effect of oxygen (toxicity). Isn't that why extreme deep divers re-introduce a higher fraction of nitrogen?
If so, they definitely don't compliment eachother.... they balance eachother.
Caveeagle
Contributor
It would make sense that reduced visibility might affect motion sensitivity, and either contribute to either the root cause or just amplify the symptoms.
Eh, no? Nitrogen is used to try to counterbalance HPNS, which is due to helium as far as I understand it, since hydreliox is used against it.
Andy, that is an interesting way of looking at it. I'd like to read more about this and any studies that have been done. I suspect that it will be a very long time before we know definitively how this works and by then we will have gained a much better understanding of human physiology and internal medicine. It seems we are barely scratching the surface in that understanding at this point in our history. Still, an interesting discussion.
DevonDiver
N/A
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