Max optimal depth on air, narcosis related

[CamG]

Greetings Elan and good question with some great posts. In my opinion and observation diver reaction to narcosis is dependent upon the divers mental/physical state, training and comfort level. Any dive once you descend narcosis is present but the level to which it impairs a diver depends on the afore mentioned criteria not to mention the depth.
I have experienced narcosis at the 130' level not to point of any catastrophic consequence but I have spent time training and preparing for deep dives and the conditions you encounter. I have been training for my up coming Adv. Nitrox / Deco class to make way for the Tri mix in the near future. I love deep dives and research as well as train to be able to enjoy them. It sounds like you have a good training philosophy already. Take your time and gain experience to work your way to wards your training goals. I have found the wisdom in planned small progressions as you have stated. I have found that when I am planning deep dives my buddy choices are very limited to a few members of our team. I know that sounds rude but I would rather dive solo or above 60' than not have 100% confidence in my buddy! We train for self rescue and buddy is the last resort! We are all on the same page and have logged many hours underwater together. In some ways I know them better under water than above. We dive with in our limits and training and have frank conversations about our abilities "weakness and strengths". I have dove with insta -buddies but would never consider doing a challenging dive with out a shallow check out dive before hand. IF that is not acceptable I would rather go solo or shallow.
I know I sound like a snob but trust me I am not, my goal is to promote safe diving.
I hope to not have offended anyone that is not my intent.
Train hard, dive harder, always dive safe with in your limits! CamG

 

[DevonDiver]

It's also possible to some extent to 'acclimatise' to narcosis - it seems that regular deep diving and training will decrease your susceptibility - again, a rather unpleasant analogy to use but - in the same way a person who drinks regularly will build up a tolerance to alcohol.

I was under the impression, that 'acclimatisation' was more psychological than physical. That the diver develops a better ability to function whilst impaired - but that there is no way to reduce the impairment itself.

 

[BDSC]

The human mind is very suggestible, if you expect or anticipate a result the human mind often delivers. There are often suppressed fears, when you are alone, deep, dark, cold, anxious, and expecting a result (narcosis) your mind will comply and release the demons. The demons are your own manufacture but we have to have something to blame it on beyond ourselves so we choose Rapture of the Deep. We need demons. That doesn't mean that narcosis is not a real effect but I think it is often highly exaggerated, especially at moderate (less than 130ish feet) sport diver depths, for our own purposes, we need a demon, so our minds give us one.

N

Well said! I have suggested this very thing on SB and of course got flamed like other have said. But you are right on.

 

[martzak]

Can anyone recommend a quick cognitive test one can perform at depth to check for the presence/severity of narcosis?
I've been down to 165ft and felt most definitely narc'ed (strongly euphoric, loopy etc.). But then another time at 175ft I felt quite in control and 'fairly' clear headed, however the bubbles from my regulator made a high pitch sound (a possible auditory hallucination or the result of increased gas density) and my body was definitely tingling, nothing bad just noticeable. That's been my experience with narcosis. I've also made numerous dives in the 100' -130' range without any noticeable change in my perception and behavior but that's not a guarantee that I was not narc'ed. My judgment and reaction time could have been impaired without me even knowing.

 

[wedivebc]

Can anyone recommend a quick cognitive test one can perform at depth to check for the presence/severity of narcosis?
I've been down to 165ft and felt most definitely narc'ed (strongly euphoric, loopy etc.). But then another time at 175ft I felt quite in control and 'fairly' clear headed, however the bubbles from my regulator made a high pitch sound (a possible auditory hallucination or the result of increased gas density) and my body was definitely tingling, nothing bad just noticeable. That's been my experience with narcosis. I've also made numerous dives in the 100' -130' range without any noticeable change in my perception and behavior but that's not a guarantee that I was not narc'ed. My judgment and reaction time could have been impaired without me even knowing.

The test is easy, if you are at 175 and you don't feel narced, you are
Actually I agree, one symptom of narcosis is lack of awareness to your present state of impairment.

 

[Diver0001]

Can anyone recommend a quick cognitive test one can perform at depth to check for the presence/severity of narcosis?
I've been down to 165ft and felt most definitely narc'ed (strongly euphoric, loopy etc.).

An easy one is spelling.

Ask your buddy to write down two similar words of the same length on a slate.

(like "teeter" and "totter" -- they don't need to be this similar but you get the idea)

Then when you're at depth get him to show you one and try spelling it *backwards*

Then when you surface do it with the other word.

Time it.

R..

 

[boulderjohn]

One of the reasons math is not a good test to compare skills at the surface and at depth is that many people use math regularly and will be able to do it with relative ease even when narced, and others use it so rarely that they can actually improve at depth because of the practice they got doing an unfamiliar process on the surface.

Here is one I have used with students because it is a task everyone can do but no one ever practices. I give them a letter of the alphabet and have them give me the preceding 5 letters in reverse order. I time it at the surface and at depth, with a different starting letter. The best I have ever had anyone do is about twice as long while at about 80-90 feet.

 

[Blackwood]

Can anyone recommend a quick cognitive test one can perform at depth to check for the presence/severity of narcosis?

One of the most dangerous effects of narcosis is the effect it has on your ability to multitask.

Task loading will break you if you are heavily narced. Next time you're at 100 feet, practice shooting a bag or running line and ask your buddy to ping you a variety of tasks (OOG, post failure, etc.). Task loads you can handle shallow become increasingly difficult with depth.

It also (in my case, anyway) kills the attention. Have your buddy flash you random numbers at random intervals, and try to keep track. On the surface, see if you can relate "at 12 minutes, you flashed me an 8, and at 19 minutes you flashed me a 14".




Edit: in retrospect, perhaps enticing you to fail with line out isn't the best idea. So instead of shooting a bag or running line, do something else that actually has to do with diving. Both of my suggestions relate to actual diving, whereas I rarely find myself spelling words backwards, opening combination locks, or putting square pegs in round holes while diving.

 

[scubadiver888]

Can anyone recommend a quick cognitive test one can perform at depth to check for the presence/severity of narcosis?
I've been down to 165ft and felt most definitely narc'ed (strongly euphoric, loopy etc.). But then another time at 175ft I felt quite in control and 'fairly' clear headed, however the bubbles from my regulator made a high pitch sound (a possible auditory hallucination or the result of increased gas density) and my body was definitely tingling, nothing bad just noticeable. That's been my experience with narcosis. I've also made numerous dives in the 100' -130' range without any noticeable change in my perception and behavior but that's not a guarantee that I was not narc'ed. My judgment and reaction time could have been impaired without me even knowing.

I was told a quick and simple check is, on the surface you agree to add or subtract. Underwater you hold my a random number of fingers and the person being tested has to respond by adding/subtracting and showing the correct number of fingers.

For example, we agree to add 2. Underwater I hold up 5 fingers. You respond with 7 fingers. Another example, I hold up 9 fingers and you flip me the bird.

If you fail this, you are narc'd. If you pass this you might want to try something a little harder.

 

[scubadiver888]

One of the reasons math is not a good test to compare skills at the surface and at depth is that many people use math regularly and will be able to do it with relative ease even when narced, and others use it so rarely that they can actually improve at depth because of the practice they got doing an unfamiliar process on the surface.

Here is one I have used with students because it is a task everyone can do but no one ever practices. I give them a letter of the alphabet and have them give me the preceding 5 letters in reverse order. I time it at the surface and at depth, with a different starting letter. The best I have ever had anyone do is about twice as long while at about 80-90 feet.

Some days I'd have a hard time doing this on the surface. At 130' I might just run out of air before I get this one done.