Filmmaker Rob Stewart dies off Alligator Reef

[St John the Diver]

None of the Columbia astronauts got their visors down and locked when Columbia depressurized. It's a very simple and fast procedure they were highly familiar with. And none of them got it done before they passed out.

That's entirely consistent with the TUC for the altitude they were at when the crew module depressurized. They were above the Armstrong Line (essentially where liquids boil at room temperature), never mind the low PP02. Remember (or know) that your brain will remain conscious for about 5 seconds without any 02 supply being provided to it (think decapitation). That's all the time they had, and it was complicated by very high G forces as well (it's likely that they were unable to move their arms as the vehicle broke up).

 

[oya]

I was just thinking of how terrified I'd be if I was at 20 feet breathing 10/50 with no access to a better gas for the final ascent.

The words "Shallow Water Blackout" would be echoing through my head.

But then I thought a) I never get in the water with trimix WITHOUT an O2 bottle anyway. b) could send a slate that says "NEED O2!" to the surface on a bag.

I know, Monday morning quarterbacking. I'm just saying.

 

[kensuf]

Yeah, if I go to a BOV I would have an OC second stage, just probably not under my chin. Would probably have it bungeed to my bailout tank. Still considering BOV plugged into dil vs bailout, but I guess this is topic drift...

This is immaterial to the discussion at hand, but I will say that having a second stage on a neck bungee was a very helpful thing this past summer when my BOV and ADV wasn't working and I needed a breath.

 

[venonguy]

There seems to be a great deal of speculation that both divers forgot all their years of training and ran out of O2 and their mix went Hypoxic and then or both failed to notice the low PPO2 while completing their deco stops, however the chances of this occuring concurrently with 2 experience CCR divers is so remote that its really a false flag on this thread. This combined with the type of CCR units they were diving enforces the point that low oxygen probable had little to do with the accident.

The more plausible explanation is actually Hyperoxia (Too Much O2)

Let me explain:
While not discussed openly on most internet forums there is a very commonly practiced deco procedure used by a growing number of "Experienced CCR Divers" to run Hyperoxic mixes when on long Deco stops , i.e. high PPO2 set points at the earlier stages in the decompression cycle , well before the 6m and 3m stops (and often as high as 1.8 to 1.9 PPO2. )

When you consider the above "trend" and given there had already been a number of repetitive dives that day both divers would have already breached their theoretical O2 thresholds, then combine a 3rd deep dive and running a high setpoint easily explains the blackouts upon surfacing , i.e. convulsions and drowning.

Until the facts finally come out I think the above is actually more likely the cause of the incident given the experience of the divers involved and a more particle explanation of events.

 

[kensuf]

I'm not for censorship, and I apologize if I came off that way. I'm all for an open discussion as well, with anyone giving their input. But I also think if you are going to make allegations against someone, you should own them and not hide behind anonymity. A man (or woman) should never be afraid to speak the truth. I'll bow out of this thread since I don't have a dog in this fight.

Sadly, an instructor speaking out against another instructor in any public forum is grounds for dismissal from many agencies. Even if what they are saying is true.

 

[oya]

Until the facts finally come out I think the above is actually more likely the cause of the incident given the experience of the divers involved and a more particle explanation of events.

I like this.
"Until we know better I'm going to believe an even less plausible bit of wild uniformed speculation."

You're right, we know dick and anything we guess at really is just a shot in the dark. But oxygen toxicity doesn't quite work like that, mate.

And knowing the Sotis profiles, he isn't the sort of guy to do looooong dives to depth. He bounces almost exclusively. It's the deco profiles that are reckless, not the O2 exposures.

And as for years of training: the deceased had been certified at that level for about three days.

 

[reefrat]

[QUOTE="

In a situation where a diver is at 20 feet with a perfectly functional (though hypoxic) RB and a bailout of e.g. 32% or such, I wonder how much subconscious resistance there would be to bailing out. In the Rec CCR world the mindset is "when in doubt, bailout" i.e. there is NO pressure to stay on the loop at all. Obviously staying on the loop is an important factor when deep in a cave etc etc but something to consider when diving more forgiving gas-situations.[/QUOTE]

Given that being on the loop at the surface, or close it, is a known high risk activity for hypoxia I find it curious that most divers stay on the loop until after climbing back aboard. Why not get plenty of lift in the wing as soon as you hit the surface then close and remove the ADV/BOV? Probably displaying my ignorance here!

Quote:
Just thinking out loud, in aviation we have a phenomenon where it is REALLY hard to abandon a "serviceable" piece of equipment even when its the best thing to do. CCR training is all about staying on the loop, mostly I suspect from the cave diving roots of much of the training where every meter longer on the loop is more OC gas reserve.

"When in doubt bail out"! To me "doubt" means anything that does not seem quite right and due to the emphasis in most CCR training of resolving multiple issues to keep the loop functional I wonder how many divers would stay on the loop in a doubtful situation when bailing out was a perfectly good option?
It reminds me of something my flying instructor told me many years ago while we where practicing emergency procedures in a single engine light aircraft- he said that statistically I had more chance of surviving an engine failure in a single than double engine aircraft. In a single there are limited options, establish glide and aim for a landing area, try engine starts on the way down if possible. In a double pilots would do everything they could to keep the plane in the air and cause they maybe didn't practice the procedure often enough tended to screw things up and get the plane out of shape.

 

[venonguy]

I like this.

And knowing the Sotis profiles, he isn't the sort of guy to do looooong dives to depth. He bounces almost exclusively. It's the deco profiles that are reckless, not the O2 exposures.

And as for years of training: the deceased had been certified at that level for about three days.

Your response actually confirms my point

 

[oya]

Your response actually confirms my point

Which part?

That when you're on the final ascent a loop (against all recorded experience, logic, and laws of physics) has an increasing PO2?

Or that a few minutes of exposure to a PO2 of .9 at the surface will be enough to finally kick the CNS clock over 100% (pft!!) and induce a seizure?

Or just that we don't know dick?

 

[cerich]

Given that being on the loop at the surface, or close it, is a known high risk activity for hypoxia I find it curious that most divers stay on the loop until after climbing back aboard. Why not get plenty of lift in the wing as soon as you hit the surface then close and remove the ADV/BOV? Probably displaying my ignorance here!

you are, they stay on the loop when the unit is delivering high ppo2 to aid offgassing, in fact most ccr at that stage are giving you 100% O2.

Even OC after a slightly bigger than "light" deco, staying on your oxygen and taking it easy on the surface/boat/shore is a good idea