Uncontrolled ascent

[MXGratefulDiver]

With regard to posts 2, 3, & 6, there is a difference between a one or two line statement about how bad the decision was to make the dive and analysing the dive and providing some insight as to why it was a bad decision and how the safety of future dives could be improved.

I see it all the time at work, quick to criticize, slow to provide alternate solutions.

Cheers,
Bill.

As the author of post 6, I'll point out that (a) I didn't criticize, and (b) I did provide an alternate solution.

Could you perhaps be either misreading what I said or referencing the wrong post?

... Bob (Grateful Diver)

 

[ShakaZulu]

My little friend Narcosis always plays a role in deep dives, don't under estimate his madness..........it's important for both buddies to monitor each other's air. I know the GI Dive Guru's may not like that, but for us dewds with less than 5000 dives, it adds a level of comfort, knowing that too crazy people is checking each other. Just make a video of yourself doing something at depth and then watch it with your non-narced state. Some interesting observations will appear.

 

[Lightning Fish]

As the author of post 6, I'll point out that (a) I didn't criticize, and (b) I did provide an alternate solution.

Could you perhaps be either misreading what I said or referencing the wrong post?

... Bob (Grateful Diver)

Bob, I enjoyed reading your post. To clarify what I was trying to say and to be blunt, post #2 stated that the dive should never have been made but provided no insight as to why or what possible corrections could have been made. The post was two sentences long. New divers reading this post won't learn anything from it.

Posts 3 & 6 were several paragraphs long, provided some really good insight as to why a problem developed, and what possible corrections could be made for future dives. Skills that should be worked on before attempting a dive of this depth were highlighted. Very helpful. As for subsequent posters that provided more helpful information, they were posting as I was typing my original post.

Cheers,
Bill.

 

[stu_in_fl]

:06:

They spotted the surfacing diver and asked him if he needed assistance. He declined their offer of a tank to return below the surface and do his deco (CMAS procedure here is to extend deco times by 50% after an uncontrolled ascent).

They then took him on the boat and provided O2. They also called emergency services on their cell phone. Within 10 min, an ambulance and a police patrol were on the spot. The diver was taken to the nearest hospital and took a ride in the chamber. He was released the next morning, free of any DCS symptoms.

I should preface this by saying I don't (generally) do deco diving (and was never trained in it) and don't know CMAS procedures.....(so this is more of a question from me for my own understanding)

.....but I was under the impression that if you'd had an uncontrolled ascent from depth and broke all your deco stops, you were at extremely high risk of DCS (even if no immediate symptoms visible), but if I am reading the above correctly it states the CMAS procedure is to go back down to de-gas ??

I thought the usual procedure would be to get to O2 and not go back down (as you'd run the risk of the DCS happpening when you were underwater which makes you difficult to rescue)?
..or am I misreading the above (or incorrect in my assumption)

...from the post, the guy didn't go back down and was immediately put on O2 [but had been given the option of another tank]

 

[WJL]

Dunno how much I agree with this one WJL, at the beginning of each dive year after a couple months off, i find the first time i hit 22-25metres, i can definitly feel the narcosis effects, but by the end of the season i'm at 40-45metres on air with no narcosis symptoms, and I don't feel that I handle the symptoms better, i just dont have the symptoms at all.
But I would be interested in reading any research if you know where to find it?

SF

Here are some links to research papers on this subject. Some of the links point to abstracts, and you will have to pay a fee to see the whole paper.

These two studies find no adapability to repeated exposure to nitrogen:

Subjective and behavioral effects associated with repeated exposure to narcosis.

Effect of brief, repeated hyperbaric exposures on susceptibility to nitrogen narcosis.

This study looked at neurotransmitters in the brains of rats, and found some change in the metabolism of these chemicals after 9 repeated exposures to high pressure nitrogen in a short time period:

EFFECTS OF THE INCREASE OF INERT GAS PRESSURE ON THE NERVOUS SYSTEM.

This article surveys several studies and suggests that adaptation may occur after 4 -5 days of continuous exposure.

Nitrox Saturation: The Road Not Taken

This paper reports a British study of psychological adaptation effects, and suggests that divers may learn to overcome the effects of narcosis in performing repetitive tasks:

Investigating the relationship between simulated depth,
cognitive function and metacognitive awareness.

There are many more papers, but this should get you started.

The general concensus seems to be that through repeated exposure to the effects of nitrogen, divers can learn accomodating behaviors to allow them to perform familiar tasks, but that basic cognition remains impaired. To me, this is much like learning to deal with drinking too much alcohol.

 

[ScubaFreak]

There are many more papers, but this should get you started.

Phew!
Better get readin
Although i still reckon that i feel fine once i've dived up as opposed to dealing with the effects of narcosis...but thats just me.

thanks for the links though, seem pretty interesting

 

[dbulmer]

LightningFish,
Your point is taken.
New divers wanting to dive to 50/60 metres should be talking to instructors on how to do it properly - I'm a novice diver so I am not going to suggest to anyone how they should have planned that dive but if a novice like me can see the danger in it and suggest not doing it then why couldn't they?

 

[Lightning Fish]

LightningFish,
Your point is taken.
New divers wanting to dive to 50/60 metres should be talking to instructors on how to do it properly - I'm a novice diver so I am not going to suggest to anyone how they should have planned that dive but if a novice like me can see the danger in it and suggest not doing it then why couldn't they?

That, I think, is the million dollar question. If you can recognize the danger in a dive, and make the right decision, whatever thay may be, then you are one step ahead. There are lots of examples on this board of divers who dive well out of their limits and are stunned to be told they shouldn't have. The same happens while on the surface, look at how many drivers run red lights. Then are stunned to find themselves in the morgue.

Far too often on this board, posters preface their post with comments like "I know I shouldn't have done this so don't flame me", "I'm looking for positive input not a flaming", etc. I don't think this should happen. It reminds me of a puppy who cringed everytime someone opened up a newspaper to read. There are a lot of posters, experienced divers and novice, who are quick to criticize but don't actually help. Then there are other posters who go out of their way to provide some helpful feedback. Granted, some divers need to be 'slapped around' , but not always.

Bill.

 

[Shasta_man]

I preface this by the now obligatory disclaimer that I'm not providing any solutions here. just admiration

Just wanted to say I admire the courage of your divers that have adapted to the available diving to go to 40-60m regularly. Wow, that is serious depth. You guys have to get some shallower fish. I would question using a single cylinder in view of the safety margin that diving should include but I don't have the technical knowledge of diving at such depth.

I'll hold your wallet for you back on the boat, then we go for some great Hefeweizen!

The incident I want to describe happened 10 days ago at the Castle of Chillon, in the lake of Geneva. I was not there myself, but several of my buddies from the dive club were present and told me about it.

This requires a little introduction: The lake is very cold (6 C at 30 m all year), and deep (over 300 m at its deepest). Most divers here have been trained by CMAS, and therefore learned deco diving on air. This is not considered "tech" diving by local standards. While many dive doubles, the majority of divers here carry single 15l steel tanks. It is not unusual to dive beyond 50 m (170 ft) for relatively short times, and to do a basic deco schedule on the way up. This all means that proper air management is a real issue. Also, because of the cold water, most divers wear dry suits.

The site has claimed a number of lives, mostly because it is one of the few places in the lake where one can dive very deep close to shore. There is a place where fish ("ombles" in French, I don't know the English name) are fraying in November-December, at 40-60 m depth, which is a favorite goal for divers.

Now to the story: A buddy team was diving to 50-60 m to look at the fish. They were wearing dry suits and diving singles. One of the two suddenly realized that he was down to 50 bar and still at depth. He signaled his buddy and started ascending, too fast. The ascent rapidly became uncontrolled. His buddy tried to slow him down by dumping all of his own air and hanging on to him, to no avail. He finally let go. The diver became a surface-bound rocket, completely out of control, and a prime candidate for a serious case of DCS. The buddy, not wanting to become a casualty himself, made a normal ascent and did all of his deco stops.

Very fortunately, there was a small dive boat at the surface (not a common sight on the lake, where most diving is from shore). They spotted the surfacing diver and asked him if he needed assistance. He declined their offer of a tank to return below the surface and do his deco (CMAS procedure here is to extend deco times by 50% after an uncontrolled ascent). They then took him on the boat and provided O2. They also called emergency services on their cell phone. Within 10 min, an ambulance and a police patrol were on the spot. The diver was taken to the nearest hospital and took a ride in the chamber. He was released the next morning, free of any DCS symptoms.

When his buddy surfaced, the diver was already breathing O2 and an ambulance was on the way.

The accident analysis is obvious: poor air management, lack of experience with a dry suit, plus a panic response when he realized he was running out of air. He could have made it to the surface safely by breathing off his buddy's secondary during the deco stops.

To me, there are a few lessons to be learned, though:

- do not dive a dry suit deep until you are completely comfortable with its operation
- always have a small tank of oxygen near your point of exit
- have a cell phone handy as close as possible to your point of exit, or even carry one in a dry container

This guy was lucky to surface near a boat that was properly equipped. I don't know if he had the O2 and phone in his car. Our club does, and this will certainly encourage us to always make sure that someone is carrying the emergency case.

 

[DA Aquamaster]

.... 1. Diving to 50-60 meters on air uniformly will cause all divers to experience significant narcosis. Claims that divers can overcome the effects of narcosis through repeated exposure have been proven untrue - repeated exposure makes divers believe they are better able to manage narcosis, but testing shows that their reactions remain impaired to the same degree.

The research on the subject is inconclusive and unfirtunately many people and agencies seem to cherry pick the data and only quote the studies that support theire views.

The reality is that there are a large number of variables that must be controlled before an accurate study of the effectiveness of adaptation and/or accomodation can be studied.

There is both subject and experimenter bias due to the beliefs and training they may have regarding the effects of narcosis as well as a plethora of individual differences in divers that affect their individual abilities to function with varying degrees of exposire to nitrogen at depth.

Impairment certainly occurs but due to differing physiology the effects occur aliong a continuum rather than as an absolutle and unvarying effect on all divers across all settings. The variables in human performance are important as well. A diver who has higher cognitive functioing or dexterity at the surface has more room to accomodate deficits than a diver who already functions in the low average range anyway befor ethey even start the dive.

Experience is also a key issue, as an experienced diver who has things down to the point where they are automoatic and requires little or no concious effort (bouyancy control etc) is also at an advantage at depth compared to a new diver who is going to be overloaded managing the basics in addition to the objectives of the dive even thouigh they may have similar cognitive abilities.

In short, a definitive study will have to be very carefully designed and will have to control for several factors other than just exposure to nitrogen.

Moreover, a relatively inexperienced diver is both more likely to panic, and to be less experienced with the effects of narcosis. All divers experiencing narcosis will be impaired in reacting to a real or perceived emergency.

You kind of allude to that here where you cite the advantage of experience. If you are not unintentionally admitting to the possibility of adaptation, you are at a minimum admitting to the potential for and value of accomodation for the effects of narcosis.