Narcosis -- insidious and subtle

[TSandM]

I know this is a cave diving story, but I'm putting it in Basic Scuba because the lesson involved is relevant to all diving.

Several days ago, I was diving a cave in Florida. The plan for the dive was to follow the main line of the cave, which runs along a shallow corridor, and then follow that line down through a fissure to a deeper section of cave (approximately 100 feet). This line runs around a loop, and ascends through another fissure, to return to T into the mainline at the first fissure. (So it's a closed loop -- if you keep swimming, you end up where you started.)

Part of the plan was to put in a jump for a brief foray down a side tunnel. In cave diving, when you leave the main line to go onto a side line, you tie a spool into the mainline and run it to the side line, so that you have a continuous line to your exit. You also mark the exit side of the intersection you created, so that when you come back out, you know which way to turn to go home. I am not only compulsive about this marking, but I insist that EVERY member of the team mark the intersection, not just the leader, so that everybody on the team knows that we turned there, and has to think about which way we turn to go home.

On this dive, we got to the jump, and the leader put in the spool (as is normal practice). I watched him do it, and then we all swam into the side tunnel. Not only did I not mark the intersection, I didn't pay any attention to whether anybody else did, either. My husband, who was behind me, thought it odd that I didn't place a marker, but he didn't put one down either, because it didn't MATTER which way we turned when we came back. Either would take us home, and going forward was actually shorter than going back (and we knew that, from the distance markers, and I had dived the cave before, as had the leader).

At any rate, when my husband commented on this after the dive, I was horrified. I have had situational awareness problems in the past, but I have never, ever failed to mark an intersection -- I've never even had to remind myself, or be reminded by anyone else. This is just not something I forget.

When I last dove in Florida, I had problems with perceptual narrowing in the deeper section of cave, but I thought a lot of it was exertion and CO2, as well as sleep deprivation, stress, and poor morale. I felt confident that on this trip, well rested and comfortable, and in low flow, the problem wouldn't recur.

But it did. And my point for telling this story is that I didn't feel drunk, I didn't feel woozy or anxious or anything at all that would tell me that my brain wasn't working the way it should be. The only evidence is that I made a mistake I simply haven't ever made before, and it was an important mistake.

The (expensive) lesson I learned is that I will no longer dive deep Florida caves without helium in my breathing gas. I am too stupid to be safe at 100 feet without it. And the lesson for the rest of you is that you don't necessarily need to feel any different at all to be stupid at depth. You can manage your buoyancy and your equipment and your navigation, but still miss things that are important. Don't underestimate the effects of nitrogen!

 

[scubamarketing]

Thanks for the great reminder. I've been to 130' with students plenty of times, frequently with students and have personally never realized if I've ever felt narced. It's important to remember that although it hasn't happened before, that doesn't mean it can't happen.

 

[Kevrumbo]

On adaptation to Deep Air and Nitrogen Narcosis:

"Moreover, our results suggest that experienced divers can discriminate between the behavioral and subjective components of narcosis. . .It has been proposed that the intensity of narcotic symptoms could be used by divers to gauge the extent of performance loss (10). The present results indicate that this advice is inappropriate for adapted divers because the two components of narcosis [behavioral and subjective] uncouple in a direction that could lead to an overestimation of performance capabilities --a potentially dangerous situation. On the other hand, the question arises as to whether adaptation confers any benefits on the diver, since performance efficiency is not directly improved and could be overestimated. In this regard, it could be argued that a reduction in symptom intensity reduces the possibility that attention will be focused on subjective sensations rather than the task at hand." [i.e. Subjective, sensations awareness vs. Situational, objective task-at-hand awareness??]
From:
p.9, Hamilton K, Laliberté MF, Fowler B. Dissociation of the behavioral and
subjective components of nitrogen narcosis and diver adaptation. Undersea Hyperb
Med. 1995 Mar;22(1):41-9. PubMed PMID: 7742709.

 

[Garrobo]

A couple years ago a DM had me about halfway convinced I had been narced on a dive on the Eagle. I swore that I had seen a lionfish hanging around a railing on the ship. He yucked it up quite a bit and said I'd probably seen a 'horny' puffer. I appreciated his humor but out of over 200 dives I have never had the feeling that I was narced. Did I say lionfish?

 

[TSandM]

Yes, my point is that I didn't KNOW I was narced. If you had asked me, at the end of the dive, if I felt as though I was impaired at depth, I would have said I was fine. I wasn't. People who are waiting to see if they get narced are looking for something they can FEEL, and it may not be there. Not only that, but it was only because a buddy noticed I'd screwed up that I ever found out about it, because I didn't notice at all. So unless you mess something up that a buddy will tell you about, you may be missing all kinds of things and not aware of it.

 

[redacted]

Yes, it is easy to become complacent about narcosis. I can recognize the symptoms when I go deep (at 140 ft my face goes numb), but I thought I was pretty free from narcosis above 100 ft. Last year in Bonaire we were dropping down early in a few of the dives to see corals and sponges that were spared the storm effects. On one dive as we past through 95 ft I felt a pain in my chest (on the outside). I though briefly that something hit me or that I was experiencing a heart incident. But I saw nothing and felt fine so we turned to work our way shallow and finish the 1 hour dive. On the way back to the hotel, I stopped to get bread and went for my money in my waterproof case that I had on a string around my neck. The case had imploded and was half full of water. But I had totally forgotten about the incident and was quite surprised that I did not even think of the case and had forgotten what had happened until I got to the store. It actually took me a moment to fully realize at that point that the case had a number of hairline cracks from an implosion.

With enough practice, you can usually work the planned, routine things through a bit of mild narcosis. But even mild narcosis may handicap you when the unusual pops up.

 

[LiteHedded]

that's why god invented 30/30

 

[DevonDiver]

I've had a very simular experience. It was on a deep-air dive shocked2 to a wreck in the Gulf of Thailand. Bottom depth was 75m (246ft).

Our shot line was tied onto the wreck on a spar that ran across an open topped forward hold (wreck was upright). The dive was fine and included mapping the rear of the vessel, hacking away some growth to try and find a 'name' and some penetration (zero viz - silt accumulated to within 3 feet of the ceiling) of top deck compartments.

The dive had gone well... and I felt very in control and calm.

At the end of the dive, my buddy and I returned to the forward hold and swam around the outside of the hold knowing that we would sight the shot line on one of the spars that ran close to the sides of the hold. We had 3 minutes of planned bottom time left. Any delays would force us into a contingency deco plan (it was already in excess of 45 mins deco on 32% and 100%), After completing two 'laps' of the open hold space - looking along the spars for the shot line we stopped and just stared at each other confused. There was no sign of the shot line. Our 3 minutes was very nearly up. I began considering our options. The shot line must have separated from the wreck? Strong current meant that I needed to start prepping my DSMB for a very deep deployment. Or should I just reel up from the wreck?

As I was going through this decision making process, my buddy tapped me on the shoulder. "look behind you". Right there...less than 3 meters away.... was the shot line. It was actually tied to a fallen mast, that ran across the top of the open hold space. At no point during our 2 1/2 minutes of searching had either one of us thought to look across the hold, rather than just along the edges, where the spars were.

Anyway, with seconds to spare, we got our ascent started.

At no time did I feel narced. The dive was demanding...penetration, the physical tasking of clearing growth from the hull... mapping the rear section on our slates... It was real eye-opener that our problem solving and awareness was so inhibited when it came to the simple unexpected problem that our shotline wasn't where we expected it to be ("but it HAS to be here").

Oh yes... our 'maps' were cr@p too. We couldn't even agree about the number of rear portholes we counted.... frankly, by the time I got to the surface, I couldn't even remember counting the portholes!

 

[TSandM]

Thank you, Andy!

My whole point in posting this (which is embarrassing and distressing to me) is to point out that you don't FEEL narced when you are. By the time you feel drunk or off kilter, you are so far beyond impaired that it's frightening. The first signs are failure to perceive important pieces of data, and making bad decisions. So many people post here and say, "I've never been narced!" The manifestations are way too subtle to be recognized, a lot of the time.

And yes, 30/30 is now my Florida gas. Florida trips just got much more expensive.

 

[LiteHedded]

once you start scootering you'll love that 3030 for different reasons