Filmmaker Rob Stewart dies off Alligator Reef

[RainPilot]

There was an article linked by Dr Sotis the other day here that discussed the benefits of staying on the loop (or O2 for OC divers) for a couple of minutes after surfacing in order to reduce bubble growth and increase off gassing etc.

Whether one agrees with the article (I do) or not, it is very likely that her husband would subscribe to the practice and hence his students as well. This may go partway to explaining why it seems that Rob didn't close the DSV and go atmospheric as soon as possible. " I'm on the surface, I'm fine, muscle memory says keep the loop in, no rush here "

 

[cerich]

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?

not if you ran out of Oxgyen because you had planned a quick third dive and entered the water trying to get three dives out of your oxygen...and didn't.

 

[Capt Jim Wyatt]

I agree with staying on the loop after surfacing *IF* the loop has a higher PO2 than .21

Routinely I do and teach to conduct an O2 flush on the surface to prevent a hypoxic event -- the surface is the most dangerous place for a RB IMO because of the potential for hypoxia.

EDIT: This edit is late but I wanted to add that we TEACH students to have a loop PO2 of at least .7 before they even jump into the water for a dive.

 

[cerich]

Your response actually confirms my point

your point assumes they had enough oxygen to do the dive, I am leaning to they did not because they thought they could get a third dive in on a far less than full o2 cylinder

 

[RainPilot]

Sent this in response to a pm earlier:

I suspect that it's unlikely that two very different physiological specimens would be identically affected by CNS toxicity at the same time. Also, it would present as convulsions not simply passing out. Oxtox is really violent and I'm sure someone would have commented on it, it's pretty distinctive.

While I'm sure it is possible, I think that a 3rd semi unplanned dive would be likely to run out of O2 "we will be fine it's just a quick bounce..."
If they had identical units and identical dive times it's likely they would both run out at the same time leading to both of them being hypoxic at the same time.

They would know this at the last stop with a PPO2 of 0.16 from dil and no way to raise it, from there it's a case of emptying lungs and getting up as fast as possible before passing out, buddy went symptomatic first and got helped, Rob a few seconds later unnoticed.

That's what my money is on anyway.

 

[cerich]

Sent this in response to a pm earlier:

I suspect that it's unlikely that two very different physiological specimens would be identically affected by CNS toxicity at the same time. Also, it would present as convulsions not simply passing out. Oxtox is really violent and I'm sure someone would have commented on it, it's pretty distinctive.

While I'm sure it is possible, I think that a 3rd semi unplanned dive would be likely to run out of O2 "we will be fine it's just a quick bounce..."
If they had identical units and identical dive times it's likely they would both run out at the same time leading to both of them being hypoxic at the same time.

They would know this at the last stop with a PPO2 of 0.16 from dil and no way to raise it, from there it's a case of emptying lungs and getting up as fast as possible before passing out, buddy went symptomatic first and got helped, Rob a few seconds later unnoticed.

That's what my money is on anyway.

me too

 

[Slow]

Question on the TUC numbers.

The attachments show TUCs of <30 minutes minutes at altitudes like 18,000 feet and drop quickly above that. This must be for humans who go suddenly from sea level to those altitudes because mountain climbers routinely go above those altitudes while working very hard. Occasionally, some remarkable humans can even go to what is essentially 30,000 feet under their own power over days of hard work.

So, how do these TUC numbers apply to divers? Is it really the same as it would be for a suddenly-depressurized pilot or is the right TUC for a diver a bit longer because it's not quite as sudden?

 

[RainPilot]

Question on the TUC numbers.

The plots show TUCs of <30 minutes minutes at altitudes like 18,000 feet and drop quickly above that. This must be for humans who go suddenly from sea level to those altitudes because mountain climbers routinely go above those altitudes while working very hard. Occasionally, some remarkable humans can even go to what is essentially 30,000 feet under their own power over days of hard work.

So, how do these TUC numbers apply to divers? Is it really the same as it would be for a suddenly-depressurized pilot or is the right TUC for a diver a bit longer because it's not quite as sudden?

I suspect it would be pretty close to the pilot numbers. It's really easy to go from 0.21 to 0.10 PPO2 diving in a few seconds , that would be close to a 18000 foot change for atmospheric PPO2

 

[CuzzA]

On the question of "why don't people tell us what happened?" perhaps this ~hour-long lecture can be of some help to those not understanding why those involved find it a good idea to not say anything.


That's a long discussion of why you shouldn't talk to the police in the US. When you consider that in addition to all of that, the standard of proof is much higher in criminal court cases than it is in civil suits, hopefully it'll become obvious why making any statements on a public forum (which would also include statements to any police officer or lawyer for the opposition) would be a bad idea, even if you're completely innocent of any wrongdoing.

I agree; however, the risk in a situation like this is you look like you're hiding something and so the only option is to file a lawsuit to get the facts through discovery. Whereas if you believe you truly did everything right and it was just a freak accident then you could prevent the lawsuit from ever being filed. It's a gamble, but if you're innocent of wrong doing you might be better served getting the truth out there.

Also, I'm curious how this works with Captains and the USCG. In a situation such as this, are there repercussions from the USCG for boat captains not talking to the USCG? @Wookie?

 

[oya]

If they had identical units and identical dive times it's likely they would both run out at the same time leading to both of them being hypoxic at the same time.

Doesn't even have to be at "the same time."

After three ascents from 230, having to bump up the O2 from a 3L bottle? That uses up a LOT of makeup gas.

At any point during that last 5... 10... 20 minute ascent the manual O2 button could have started to hiss slower and slower.