What is the Shallowest Depth at which You Notice Narcosis?

[100days-a-year]

4-5000 dives past 100' on spearfishing air or nitrox,probly more.I currently try to limit myself to 170' but will drop to 190 if I have to.I have spearfished deeper but do not like the level of impairment I experience,however I have successfully dove doubles and stages while spearfishing on air at 200' and well past that on mix.

My impairment is noticeable only if past 130ish or dark,cold or heavy currents.Last year I was commercially harvesting lionfish at 170' mostly without getting stung,quite a task @ any depth n any gas.I stay as shallow as possible every trip but you gotta go where the fish are.

I venture that narcosis is similar to alcohol and drugs in that individual tolerances vary as well as there being daily variability among individuals.I recall going to the enlisted club in Great Lakes at noon and still being drunk on the breathalyzer there after drinking the night before,I finished 2 years of Gas Turbine and Electrical Engineering schools with a 98 numerical grade doing that just about every night.With drugs I have often come to in the middle of an operation(usually resetting bones)while shot up with enough sodium pentathol or equivalent to stun NFL OL.

 

[Locus]

Isobaric counterdiffusion (Wikipedia)

DCS can also be caused at a constant ambient pressure when switching between gas mixtures containing different proportions of inert gas. This is known as isobaric counterdiffusion, and presents a problem for very deep dives.For example, after using a very helium-rich trimix at the deepest part of the dive, a diver will switch to mixtures containing progressively less helium and more oxygen and nitrogen during the ascent. Nitrogen diffuses into tissues 2.65 times slower than helium, but is about 4.5 times more soluble. Switching between gas mixtures that have very different fractions of nitrogen and helium can result in "fast" tissues (those tissues that have a good blood supply) actually increasing their total inert gas loading. This is often found to provoke inner ear decompression sickness, as the ear seems particularly sensitive to this effect.

Very interesting.

 

[scubadada]

I just started regularly going past 60' and I've been getting a peculiar feeling around 90', which seems a bit shallow for narcosis from what I've read. Maybe it's my imagination?

What is the shallowest depth at which you thought narcosis may have been creeping up on you?

Occasionally at sea level, but it's pretty predicatable

 

[Peter69_56]

Very interesting.

I see in Multideco the setting for the alarm for this is a 0.5 Atmosphere change of END for gas changes (IBCD N2 0.5 ATA, IBCD He 0.5 ATA)

 

[The Chairman]

It all depends on how you define narcosis. Perceptual narrowing is nigh to impossible for most people to detect. You can do a task, or maybe two or three and it might seem that your cognitive abilities have been unchanged. They have. Your ability to resolve unique problems has been diminished, even if you don't think they have.

I had a shoulder injury many years ago that damaged my rotator cuff. It's never been right, but when I hit about 80 fsw, I don't feel the pain anymore. That's the depth I use to figure out when I need to be extra careful.

 

[Peter69_56]

It all depends on how you define narcosis. Perceptual narrowing is nigh to impossible for most people to detect. You can do a task, or maybe two or three and it might seem that your cognitive abilities have been unchanged. They have. Your ability to resolve unique problems has been diminished, even if you don't think they have.

I had a shoulder injury many years ago that damaged my rotator cuff. It's never been right, but when I hit about 80 fsw, I don't feel the pain anymore. That's the depth I use to figure out when I need to be extra careful.

Stay down Obe One Kanobie, work with the force!

 

[ajduplessis]

Because Isobaric Counterdiffusion is usually only a problem at signficant depths(greater than 300ft and usually closer to 400ft). We switch from trimix to nitrox all the time at 100-120 coming back up on deco. On long deco dives, it can save quite abit in deco time/

ICD can happen as shallow as 120ft if you dont know what you are doing. I think you are refering to another helium problem - HPNS (high pressure nervous system). This could start at 400ft+

 

[Peter69_56]

ICD can happen as shallow as 120ft if you dont know what you are doing. I think you are refering to another helium problem - HPNS (high pressure nervous system). This could start at 400ft+

This was my understanding as well.

 

[wedivebc]

ICD can happen as shallow as 120ft if you dont know what you are doing. I think you are refering to another helium problem - HPNS (high pressure nervous system). This could start at 400ft+

Please site one case of ICD (or more correctly ICD induced DCS) that has occurred at 120ft. Or even shallower than 300ft for that matter. I have never heard of one.

 

[Peter69_56]

Please site one case of ICD (or more correctly ICD induced DCS) that has occurred at 120ft. Or even shallower than 300ft for that matter. I have never heard of one.

Using Multideco it alarms on it if I have the following conditions;

60m 22 min 18/40 then change to 32%Nx at 39 metres ppN2 of IBCD setting 0.5 ATA