Fiona Sharp death in Bonaire

[wedivebc]

Presuming a gag strap that has a lip shield (like the rEvo one), if the diver passes out as a result of toxing or hypercapnia (from overexertion - not a breakthrough), why would you not think they might live for an indeterminate amount of time, while passed out, simply because the loop is breathable, in their mouth, and not flooded?

I read the whole thread. I did not read anything that was at odds with the possibility that a gag strap could *possibly* have kept her alive until she was found.



As above. When people simply pass out, they don't usually stop breathing (I don't think). Why should it be different under water? If they loop stays in and sealed against the diver's lips, and the nose stays occluded by a mask, it seems entirely possible that SOME conditions could result in a diver passing out but continuing to live for an indeterminate amount of time.

In particular, for someone who toxes, even without a buddy, if they are found on the bottom at 80 feet, an hour later, but the loop is in their mouth and not flooded, why is it that unlikely for them to survive? Why is it that likely that they would embolize if they happened to float to the surface? DCS? Sure. Lung overexpansion? Why?

FWIW, the rEvo mouthpiece/lip shield/gag strap does a pretty good job of holding the mouthpiece in and maintaining a seal. When I want to vent gas from my loop, completely relaxing my mouth and exhaling does not work. The gag strap keeps the lip shield in place and the seal is maintained. I have to go head up, to get my mouth to be the highest point in the loop, THEN relax my mouth as much as I can, tilt my head to the side, and then exhale. Even then, I can't get all the gas out. I don't think I could flood the loop on purpose, with the gag strap in place.



The dil cylinder was air. But, is it confirmed that that cylinder was what she was actually using for her dil (versus using that for wing and using her offboard TX20/20 for dil)? Not that it makes a material difference to her ppO2....

Sorry to be blunt but anyone who enters the water intending to do a solo dive to 300ft carrying 2X40s of bailout and air diluent is not very likely to take the precaution of wearing a gag strap.

 

[doctormike]

Presuming a gag strap that has a lip shield (like the rEvo one), if the diver passes out as a result of toxing or hypercapnia (from overexertion - not a breakthrough), why would you not think they might live for an indeterminate amount of time, while passed out, simply because the loop is breathable, in their mouth, and not flooded?

I read the whole thread. I did not read anything that was at odds with the possibility that a gag strap could *possibly* have kept her alive until she was found.

I mean, hard to prove definitively that there is NO possible scenario where the gag strap could have helped a solo diver - you can always come up with these. But the point is that the gag strap benefit is mainly in the context of buddy diving. That seems pretty well documented by the French study.

As far as your specific scenarios, the overexertion one is most likely, and I believe was discussed upthread. With a functional scrubber, passing out would definitely reduce workload and the CO2 would drop. Not sure how often overexertion hypercapnea leads to LOC, though.

I actually don't know what happens to human brains with exposure to hyperoxia beyond the seizure threshold, and if eventually metabolizing the loop down would simply result in waking up, or hitting that sweet spot where you are rescued by a passing diver before your scrubber gives out. In that case, you would also have to assume that the hyperoxia was just from a rapid descent, and not from some ongoing thing like an internal O2 boom, or an eCCR with a stuck open solenoid or current limited sensors, that will keep pumping O2 into the loop.

So in answer to your point - a gag strap is probably associated with a non-zero decrease in risk for a solo CCR diver. But it seems fairly small, and dependent on some very unusual circumstances which I have never seen documented or discussed. It would be a pretty miraculous save; I think that at least one of us would have heard about it.

 

[JohnnyC]

Gag straps work when you have a buddy. Without a buddy, the confluence of circumstances the would have to occur for a gag strap to enable a self rescue are pretty close to impossible.

That's not a condemnation of gag straps, I have them on both rebreathers, but the idea that having a gag strap while solo diving is a benefit is probably statistically close to zero.

The odds of a rebreather self-correcting loop contents in a manner that allows a diver to regain consciousness are slim-to-none. The odds of a buddy being able to do so are significantly higher, hence the benefit of the gag strap.

Would it have made a difference here? Possibly, if the loop was viable and if she were alive, simply unconscious, long enough for someone to rescue her. That viable timeframe is probably pretty small though.

 

[JonG1]

TBF a gag strap fulfills other functions aside from protection of the airway in an unconscious situation, it's easier to avoid water ingress around the lips, takes the weight of the loop which again could assist in maintaining loop integrity late in a dive.

There is less likliehood of a surface flood because it's easier to set up prior to entry and remove post exit, this also reduces the risk of comprising the mushrooms in an environment with surface debris.

The reduced level of muscular tension required to retain the dsv/BOV may also improve WOB but this is pure conjecture.

 

[tursiops]

The dil cylinder was air. But, is it confirmed that that cylinder was what she was actually using for her dil (versus using that for wing and using her offboard TX20/20 for dil)? Not that it makes a material difference to her ppO2....

I have no info on which cylinder was being used for dil. I do know the 80% AL40 was untouched and the 20/20 had been used, but I don't know how much. I am no longer in Bonaire so cannot get much more info.

 

[stuartv]

I actually don't know what happens to human brains with exposure to hyperoxia beyond the seizure threshold

This is a very uneducated, lay understanding - but I thought that it was pretty well understood through data from hyperbaric chambers that continued exposure to high ppO2 after a seizure was not harmful. At least, not significantly and not in the timeframes we would be talking about for rescuing a diver.

I have been taught (and teach) that the real danger of an OxTox hit is not the seizure itself. It is the loss of the regulator from one's mouth during the seizure. That is what has led me to think that a good-sealing gag strap might enable the diver to survive the hit and remain alive for an indeterminate amount of time afterwards.

In this particular case, I had the impression that Dr. Sharp was found well within the timeframe that her CCR would have still had O2 and been functioning. And, since she was on the bottom at 80' (not on the surface or at some extreme depth), if the loop had stayed in her mouth the whole time, it would have been *possible* (depending on exactly what actually happened in the first place, of course), that she would have still been breathing on the loop but unconscious when found. Or, who knows, possibly she would have passed out briefly and come to and rescued herself. Or maybe she didn't even pass out and, if she had not lost the BOV during a seizure (TOTAL speculation), she would have been conscious the whole time and able to continue her ascent unaided.

There are a crap-ton of unknowns, including whether it was even an event where a gag strap and a buddy would have had any chance of making any difference.

My only real question to you and @CuzzA was about the basis of the assertions that a gag strap would have made no difference.

I understand that the French study showed benefit when combined with a buddy. But, lack of proof does not constitute proof of non-existence. In other words, there is not a study (that I know of) that suggests that a gag strap is of zero value if you do not also have a buddy. However, that is kind of how y'all's comments came across (to me).

I hope that someday I am able to be as knowledgeable and experienced as Dr. Sharp was. I hope that someday I will be competent to safely do a 300' dive while solo on CCR. And I really hope that if and when I achieve that, I also have the wisdom and self-restraint to not actually do it.

 

[doctormike]

My only real question to you and @CuzzA was about the basis of the assertions that a gag strap would have made no difference.

I can't speak for any other poster, but I virtually NEVER say never. Maybe it's because I'm wishy-washy by nature. But the most important sentence in med school is "there is a bell curve for everything", so I'm pretty sure that I didn't say that it would have made NO difference. That's simply not provable, as you implied. Of course you can come up with hypothetical scenarios where people survive for hours unconscious on the loop until they are rescued. Hey, remember the infinite improbability drive? Eventually, even unlikely things happen...

Here is what I said:

"[a gag strap is ] Definitely helpful if there was a BOV (there was), but not so sure of the benefit for a solo diver.

The French military rebreather study showed an amazing survival rate (94% of divers who lost consciousness!), but it depended on a buddy being present. If you are solo diving and lose consciousness, I guess there might be a scenario where the diver could recover spontaneously. But for the most part, I don't think that the gag strap would make a huge difference. If you pass out from toxing or hypoxia when you are alone, that's probably not survivable even if the mouthpiece stays in."

I understand that the French study showed benefit when combined with a buddy. But, lack of proof does not constitute proof of non-existence. In other words, there is not a study (that I know of) that suggests that a gag strap is of zero value if you do not also have a buddy. However, that is kind of how y'all's comments came across (to me).

I think that @JohnnyC said it pretty well upthread. If you read my comments as saying that a gag strap is of zero value to a solo diver, then go back and read them again.

But it sounds to me as if you are parsing the difference between the legal concept of de minimis and the mathematical concept of zero.

 

[Roz]

Trouble with the theory of her wanting to join the '300 Club' is that Fiona Sharp was Australian, and we finally fully adopted the Metric system nationwide in 1988.
So she would have originally trained in metres and BAR/kPa and then used the Metric system in her routine OC/RB diving not feet and psi...

Good point well made about the metric system and Fiona being an Ozzie. I was told a corking story that relates to that. This is taken from my tribute that was published by X-Ray Mag.

There is genuine sadness that she has died, and lot of fond memories being discussed, and of course some cannot be published. Dr Christine Penny very generously shared this oh so typical tale with me. "Fiona and I were at a joint Diving and Hyperbaric Medicine and Aviation Medicine conference at Heathrow many years ago. The last speaker was a dual qualified doctor astronaut from NASA who was part of the team tasked with looking at the challenges of getting man to Mars. He gave an amazing talk with lots of information and stunned the audience into silence. At the end 'any questions? Are you sure no questions?' Cue loud Australian voice from the back of the room – ‘When are you Yanks going to turn metric?” The whole conference was in stitches."

**

I think it is pretty fair to say that the cultures that work in metric would not consider joining the 300' club, it really doesn't come into our mind at all. If we are doing that kind of depth of dive, then it's more likely to be the 100 m club, ie 328 ft.

 

[Roz]

From the Bonaire ReporterView attachment 547495

Thanks for posting this. When is the mainstream media ever going to get it right? CO poisoning?!

 

[homerdoc]

yeah...I feel bad about posting it without context in this thread based on the thread spin off.

The Bonairereporter is a local paper that is mostly about social events, crimes, feel good articles, selling real estate and govt updates.

I always read it before a trip to see if something is going on.

I wouldn't use it for anything scientific or think of it as in depth analysis of any particular subject.