Cozumel Incident 9/4/11

[Texas Torpedo]

Sorry I missed that, James.. And you are the super "nerd" guru diver... Mostly kidding, and with all due respect, of course..
Now, back to the Benchmark... Some of us have been refreshing TBM Home Page numerous times a day..
(I know it's off topic but thanks for all the hard work you and everyone have put into it..)

 

[lamont]

I finally seem to have a grasp of what it is showing and this version (of three posted) seems like a reasonable plan. Perhaps it is a minute too long at depth but seems close had nothing gone wrong. It would be nice to see how the gas requirement changes with a 400' bottom.

If the assumed air consumption rate is close for the woman and DM, then they started out with too little gas. 120 cu ft tanks may have helped substantially.

That makes me wonder how much experience they had deep. Surely they must have had some experience in the 250-270' range to know how they would react to nitrogen and that they had plenty of air. I don't see someone with only knowledge of how they react at 130' suddenly deciding to go to 300'.

If they did have enough exposure at 250'-270' to know that going a bit deeper may not have increased the risk dramatically...and IF people react about the same to nitrogen under similar conditions, what is the likely explanation for one diver apparently becoming narced and slowly descending or swimming deeper?

A second issue was the site. Further south are sites that have sloping bottoms. My view is that doing a risky dive in that area may have been better. Should a diver become narced, "maybe" they will just drop a few feet and hit the sloping ocean floor. That would make a rescue far easier. I don't know if this sloping characteristic applies at 300'. Most likely it does to at least 250' in some places.

This is not a tutorial on making 300' dives on air. On the continuum of safety for a 300' dive, where on one end you have two divers who come out of Devil's Throat and decide to drop to 300' to the accepted way of doing a 300' (gas mixture, equipment, support, pre-planning ,etc), this dive was not on the safe side of that continuum. It could have been better.

I still believe that in time a release of the dive computer data by at least one of the people who ended up around 400' will be useful. The bad outcome may discourage some deep diving but I doubt that it will end. A complete airing of the events will hopefully prevent a recurrence. I had no desire to dive to 300' on air before this. That is reinforced by the serious medical problems encountered.

you are really crunching all the wrong numbers and kind of missing the bigger picture.

218 feet is a ppO2 of 1.6 for 21%, at 300 you're at a ppO2 of 2.1 and at 400 you're at a ppO2 of 2.7 and running a significant tox risk.

at 300-400 feet air becomes thick and viscous and WOB increases, significantly increasing the risk of a CO2 hit on top of the nitrogen narcosis (helium is much less viscous).

at 300-400 feet there's a significant risk of deep water blackout due to nitrogen narcosis, which is probably the root cause of why the one diver dropped below the planned depth (and if they did have a lot of experience in the 250-270 range on air, that would just show that deep water blackout is a risk that can't be mitigated by prior conditioning).

the way to mitigate all these risks is with helium - 10/70, and the training to use it properly.

others in this thread have compared this incident to climbing which is pretty stupid -- this is like bungee jumping without even knowing how to safely secure the bungee.

there's people who solo CCR to 300' with insufficient bailout gas of too high a ppO2 and i think they're running a high risk, and we could get into at least a halfway useful argument as to if there's a comparison to be made there with aggressive technical climbers that are on the edge. this dive was just a dumb ego stunt though, pure and simple.

 

[Tortuga68]

If they did have enough exposure at 250'-270' to know that going a bit deeper may not have increased the risk dramatically...and IF people react about the same to nitrogen under similar conditions, what is the likely explanation for one diver apparently becoming narced and slowly descending or swimming deeper?

Narcosis doesn't work like that... not only is there huge variation between people in how they are affected, there can be big variations in one person from day to day or even dive to dive on the same day. You can be quite functional & aware at 50m one day and narc'd off your head at 45m the next. Also the effect tends to be non-linear so the difference in effect between 250 and 300 can be much more than 20% 'worse'

 

[Brules]

I'm curious if heading straight to the chamber on oxygen vs IWR would have made a difference in the extent of the injuries? Yes the dive plan was bad and went horribly wrong, but they made it to the surface somehow - just how big of a mistake was the idea to do IWR?

 

[Jax]

I'm curious if heading straight to the chamber on oxygen vs IWR would have made a difference in the extent of the injuries? Yes the dive plan was bad and went horribly wrong, but they made it to the surface somehow - just how big of a mistake was the idea to do IWR?

Asked and answered already.

The subject was touched on . .

After TSHTF, what should have been the right decision?

They decided to try some recompression at 60-70fsw.

They could have gone to the chamber.


What should have been the right decision, and why? What was the time to travel to the chamber, and surely the risky in-water recompression could have done SOME good?

Returning back to the water to attempt to decompress only made this worse. Unless you are breathing 100% O2, you are still loading nitrogen that will have to be off gassed later. With 100% O2 you reach 1.6 pp at about 20 feet, after 45 minutes you will have reach 100% O2 exposure. It is always better to breathe O2 on the boat on the way to the chamber than to attempt "in water recompression".

In more simple words -

Once you reach the surface, you are bent. Getting back in the water is really just another dive. The result is time wasted in getting to a chamber, and possibly even more bent than if you had just gone to the chamber right away.

the reason for going back in the water has nothing to do with the nitrogen gradient. The purpose is the same as going into the chamber--to use the increased pressure to reduce the size of the bubbles that are already there or are forming.

The established in-water recompression procedures I know--and I have three friends who recovered when using them in remote areas where rapid medical evacuation was not available--include breathing pure O2 during the dive so that both problems can be addressed. My friends used O2 and full face masks as a safety factor in addition to the divers who were monitoring them.

Dr. Richard Pyle, the author of one of the accepted protocols, has himself been saved via the process twice. He has written eloquently about both experiences, and a Google search will lead to some interesting reading.

In-water recompression is indeed controversial, and even its most ardent advocates, I believe, would agree that in this case breathing O2 on the surface while going as fast as possible to the chamber would have been a much better decision.

 

[Brules]

Thanks for posting those!

 

[fdog]

I'm curious if heading straight to the chamber on oxygen vs IWR would have made a difference in the extent of the injuries? Yes the dive plan was bad and went horribly wrong, but they made it to the surface somehow - just how big of a mistake was the idea to do IWR?

That depends on what the exact circumstances were. I could have sworn I had read they had no symptoms when surfacing (but for the life of me I can't find it now...? Dang.).

****** No symptoms=Omitted Deco *****

If that's true - no symptoms when surfacing or during their time on the surface - then executing Omitted Deco correctly (descending to the first missed stop and completing the missing deco, plus extra time shallow) would have, in all likelyhood, had a good enough outcome that we would have never heard about this. They more than likely would not have been symptomatic after surfacing the second time.

The issue here is correctly. Personally I'd have started my missing stops at at least 120', more than likely 160'. I'd have been hanging under a bag so more gas can be slid down the line. These folks started at only 60'. (If it was Omitted Deco)this allowed them to get bent because they were way above the start-offgassing depth, so as Omitted Deco, it was performed grossly incorrectly, and allowed bubbles to grow while under pressure. Thus bubble pumping occured (the bubbles were made small enough the lungs would not filter them out) and the bubbles went places they shouldn't be - like the brain and spinal cord, where they became large and necrotic upon re-surfacing.


******* Symptoms=IWR ***********

If, however, they were symptomatic on surfacing (or became symptomatic before re-submerging), then they attempted IWR without the resources or knowledge to execute it. For example, it takes almost a whole T cylinder of O2 for a single diver to complete a USN IWR cycle. What they did, again, allowed bubble pumping, except with greater bubble production in their bodies, and a much stronger type II hit.

***********


So in summary, whether OD or IWR, the proceedure selected by these divers (with the best of intentions) simply made a bad situation much worse than a 30 minute sprint to the chamber on O2. In the latter case at least they'd have had lung filtration.

There are so many missing elements that would have prevented this, and (lack of) correct training is at the core of it.



All the best, James

 

[boulderjohn]

There are so many missing elements that would have prevented this, and (lack of) correct training is at the core of it.

With all these posts and all these threads, I hope this one message is the one that comes through to the dive world in general.

Many and perhaps most recreational divers (by that I mean people whose training and experience is within traditional recreational limits for depth, time, and environment) believe that when they have achieved the top levels of skill in that area, they have achieved all they need to progress to what is commonly called technical diving (by that I mean diving that exceeds recreational diving in depth, time, and environment--such as caves and wrecks). Without that training, a highly skilled recreational diver may not realize that such diving calls for knowledge, skills, and equipment not normally known at the recreational level. They may not realize how slim the margin of error is on those dives, and how easily what would normally be a minor error becomes a catastrophe from which there is no recovery without proper training and equipment. That is why so many skilled recreational instructors fall victim to accidents in caves, for example.

That is why I feel it is important that the myth about the downcurrent be dispelled. If that story persists, then the message might be that it is OK for skilled recreational divers to plan dives to 300 feet on a single tank of air--just make sure you are in an area where there are no downwellings.

 

[cicopo]

I've been wondering why some consider this an accident. To me it would seem to be the sad but predictable end of an experiment. I strongly feel that either Opal or Gabi, and maybe both have been making progressively deeper dives over time adding more depth as things played out after 1 or maybe a few successful dives to any given depth. If everything seemed fine at (random number used, no evidence it applies here specifically) say 225 feet, then it's time to try doing 230 -235 feet next trip. As time goes by the depth gets deeper thinking that all is well & there weren't any after effects. Like every such experiment the risks get bigger, and eventually the risks win. Had Opal stopped at the planned depth & the dive gone as they expected it to we might not have heard about this particular dive, but we might have read about one of the next dives in the series when it fell apart. Just like an elastic band breaks when stretched too far, or a car goes off a curve when driven too fast bad things do happen when people refuse to believe the rules of common sense apply to them.
On top of that idea I also think they may have been far too confidant in their skill set, because they had the resources to at least have extra air waiting for them at depth, yet they skipped doing it. Based on the calculations I've seen as examples of what could be done in an ideal situation they seem to have cut it way too tight in their plan, omitted any back up plan, and did a dive knowing it had to go EXACTLY RIGHT, or they'd be in trouble.

 

[Dave Dillehay]

For the record, all diving in Cozumel is drift diving and it would be a practical impossibility to drag a tank under a boat that had to stay near the wall.


Dave Dillehay
Aldora Divers