Quiz - Skills & Environment - Diving at Altitude

[NAM001]

Why would nitrogen narcosis happen at shallower depths at altitude?

I would giess that if it takes say p;urely a 4 atm change to cause it then the base teh atm change is the controlling factor.

Just trying to make this work if you get narced at 100 ft it is then a change from 1atm to 4 atm that does it and not the result of a pressure of 60 psi ambient on the body. 4 atm at sea level would be 60 psi. I have always assumed that it would take,,,, in the 100 ft case,,,, 60 psi to bring it on and as the ambient pressure dropped it would take for arguments sake 110 ft to get to 60 psi. I like questions like this. As in this question so much taken for granted because we always dive in the same altitude more or less.

Higher altitude rules always made sense to me for deco because the end result is using the current surface pressure as a measurement base for what the ratio you would be experiencing when you got out of the water.

 

[Edward3c]

In general most questions do not have an all of the above unless that is the answer but I am with those wondering about he narcosis answer. Is not narcosis driven by hard presure and that PPN2 is related to sea level as a standard? Then since you have a lower ambient you would have to go deeper. Based on the answer It would say that narcosis is the same PPN2 but based on the shore ambient pressure of the higher altitude as opposed to sea level. Puzzeling to me because if at sea level it takes say 4 atmospheres to begin to have it which would be 100 ft does that mean if the ambient is now say .8 of sea level atmosphere it will not occur at say 70 ft or 4 times the .8 atmosphere. If that is true then it must be the body adjusting from the surface pressure to the water pressure making a 4 atm change the key. That would make me wonder if the body would first have to be adapted for high altitude over some period of time rather than a quick trip from the beech to a high altitude for the body to function in that altitude as a norm. . Does the body acclimate that fast to altitude change? Then if not so someone that lives in high altitude is already on their way to the narcosis PPN2 by nothing more than the drive to the beech. Would that body be experiencing a PPN2 of something like 1.3 atmospheres going form a .8 altitude compares to sea level to sea level simply by gong to the beech. Sports people do not adapt immediately to playing in higher altitudes. and those in say denver going to san diego to play a game get an advantage from the lower altitude and thicker air.

Great question for thought

From the BSAC altitude tables a change from sea level (level 1) to 1,000m (level 3) - at 1,000 millibar. Changes the tissue code from A to B, there is a 5 hour wait to return to an A code.

 

[NAM001]

From the BSAC altitude tables a change from sea level (level 1) to 1,000m (level 3) - at 1,000 millibar. Changes the tissue code from A to B, there is a 5 hour wait to return to an A code.

I agree. just did not know it changed when narcosis came on. those groups you cite effect deco. So let me add too the crap in the fan how dies higher altitudes effect MOD with nitrox if it effects the PPN2 for narcosis. Is the ppO2 now reached at a different depth also??? It should if narcosis depth changes.

 

[Angelo Farina]

Why would nitrogen narcosis happen at shallower depths at altitude?

I do not know, but it is definitely true. I had bad narcosis in several dives in mountain lakes, at depths where in the sea I am sure I had no problems, like 24 meters...
There are probably a number of factors, some physical, some physiological, and some psychological.
Among the latter ones I certainly identified the water colour (brown instead of blue), the bottom made of brown mud, instead of sand and corals, the lack of light (at 20m it is completely dark), the water turbidity (you cannot see more than 1m away), the water temperature, etc...

It must also be said that the type of narcosis is the bad one, making you feel little and poor and scared. Not pleasant at all!
At the sea, at 50 meters or more, I usually experienced a completely different type of narcosis, making you happy, hilarious and feeling invincible... Very nice, albeit, of course, much more dangerous...

 

[BlueTrin]

High altitude impairs performance, leading to the urban myth of alcohol having a stronger effect at altitude, is it related ?

 

[Angelo Farina]

High altitude impairs performance, leading to the urban myth of alcohol having a stronger effect at altitude, is it related ?

Possible. I always remember how badly I got drunk during a campfire at altitude. It wast last day of the year, and we did spend the evening near a mountain lake (Lago dei Caprioli, Fazzon in the Dolomites, at approximately 2000m altitude). There was more than 1 meter of snow, but we were wearing hot clothes, there was a nice hot fire, and we were drinking vin brule' (a typical local mixture of wine and organic flavours) and eating pork sausages roasted on the fire. At midnight I was really badly drunk, something I never experienced drinking wine at the sea...

 

[BRT]

High altitude impairs performance, leading to the urban myth of alcohol having a stronger effect at altitude, is it related ?

But, at depth you are not at reduced pressure like you are at the surface.

 

[BlueTrin]

But, at depth you are not at reduced pressure like you are at the surface.

That’s what I was wondering.
This is why I made sure I put a maybe

 

[tursiops]

But, at depth you are not at reduced pressure like you are at the surface.

Yes, you are. Say you are at 66 ft at sea level. Your pressure at depth is two atmospheres of water, plus one of atmosphere, or 3 atm total pressure on you. At altitude, you still have two atm of water, but LESS than one atmosphere of air above you, so you are at (say) 2.8 atm at maybe 4000 ft altitude (just making up numbers).

Added: I interpreted your comment as being about reduced pressure at depth. Did you mean reduced even lower than at the surface? No, certainly not. All that water above you is heavy....

 

[BlueTrin]

Yes, you are. Say you are at 66 ft at sea level. Your pressure at depth is two atmospheres of water, plus one of atmosphere, or 3 atm total pressure on you. At altitude, you still have two atm of water, but LESS than one atmosphere of air above you, so you are at (say) 2.8 atm at maybe 4000 ft altitude (just making up numbers).

Added: I interpreted your comment as being about reduced pressure at depth. Did you mean reduced even lower than at the surface? No, certainly not. All that water above you is heavy....

I think he meant to say that the pressure is reduced so the increased narcosis is unintuitive.
But I will let him speak for himself.