Filmmaker Rob Stewart dies off Alligator Reef

[St John the Diver]

In this thread, I have already made a fundamental change to my RB diving in that I now make a BIG point of closing the DSV once Im on the surface and go off loop for ANY reason (possible buoyancy loss from CL

All of these are positive contributions to my own diving safety even if none of them end up being applicable to this incident!"

-+++++

Removed the quotes so as to make it a more global comment (and thanks for making the change. It might save your life one day):

Glad there is some value here.

As to closing the DSV: You weren't hammered on that on every dive in your rebreather training starting on day one? It's a basic rebreather survival skill. It's back to "w don't know what we don't know". What else did your instructor not teach you?

I'm not picking on you at all, but if your rebreather training didn't drive this skill home your training was inadequate. And that's the problem with rebreather training these days. Too many small things slip thru leaving a hole in knowlage. Now and then all the holes line up and a diver dies. I can't help but think that this was the case in this accident.

Advice? If/when you do MOD 3, find another instructor.

 

[eeel]

True in theory but generally irrelevant in the case of a rebreather diver.

Do some simple math:

Rebreather:

1: The divers carry ONE 2 litre cylinder of diluent.

2: That cylinder has 10% oxygen, 50% helium, and 40% nitrogen.

3: that has is "heliair", meaning it's blended very simply: fill the bottle half way with helium and then top off with air.

4: one litre of volume in the cylinder is then "occupied" by air.

5: let's imagine that they filled the cylinder to 200 bar. That's now 200 litres of free air available to the diver that was produced by a compressor.

6: that tiny amount of gas is used (blended with helium) as a diluent, and it's rebreathed again and again and again. And only a fraction of the cylinder volume is actually used on a dive series.

7: the percentage of carbon monoxide in that small amount of gas needed to impact a diver would be so extremely high as to be nearly impossible to obtain.


Contrasting:

Open circuit:

At even, say: 5 ATM (40 metres) a diver is honking thru 4x the surface volume consumed. It's likely he's chugging down the amount of gas a rebreather diver consumed as diluent on a complete dive ON EVERY BREATH and bonding whatever CO is in the gas mix to hemoglobin continuously.

Bottom line is that a CO level that would be lethal to an open circuit diver is an irrelevancy to a rebreather diver.

This is an red herring theory not developed by anyone who has actually thought it thru.

John

Thanks for taking the time to type out those examples. I agree it is unlikely that CO had anything to do with Rob's accident; I was just expanding on Tony's post about The affinity or CO to hemoglobin, and how high PO2 can mitigate that pathology.

 

[St John the Diver]

John

Thanks for taking the time to type out those examples. I agree it is unlikely that CO had anything to do with Rob's accident; I was just expanding on Tony's post about The affinity or CO to hemoglobin, and how high PO2 can mitigate that pathology.

Pleasure. The physiology is right but the amount of CO required would be off the scale.

 

[Storker]

True in theory but generally irrelevant in the case of a rebreather diver.

Do some simple math:

Rebreather:

1: The divers carry ONE 2 litre cylinder of diluent.

2: That cylinder has 10% oxygen, 50% helium, and 40% nitrogen.

3: that has is "heliair", meaning it's blended very simply: fill the bottle half way with helium and then top off with air.

4: one litre of volume in the cylinder is then "occupied" by air.

5: let's imagine that they filled the cylinder to 200 bar. That's now 200 litres of free air available to the diver that was produced by a compressor.

6: that tiny amount of gas is used (blended with helium) as a diluent, and it's rebreathed again and again and again. And only a fraction of the cylinder volume is actually used on a dive series.

7: the percentage of carbon monoxide in that small amount of gas needed to impact a diver would be so extremely high as to be nearly impossible to obtain.


Contrasting:

Open circuit:

At even, say: 5 ATM (40 metres) a diver is honking thru 4x the surface volume consumed. It's likely he's chugging down the amount of gas a rebreather diver consumed as diluent on a complete dive ON EVERY BREATH and bonding whatever CO is in the gas mix to hemoglobin continuously.

Bottom line is that a CO level that would be lethal to an open circuit diver is an irrelevancy to a rebreather diver.

This is an red herring theory not developed by anyone who has actually thought it thru.

Sorry, you don't provide enough data to make a credible claim. Before your argument (there isn't enough CO in a bottle of dil to saturate the hemoglobin) can be discussed, you have to provide the capacity of the diver's blood cells to bind CO. Your claim is that there isn't enough CO in a bottle of dil to make an impact on the diver's hemoglobin. That claim is invalid, untestable, unfalsifiable until you document that the hemoglobin in ~5L of blood can bind all the CO in a bad bottle of dil and still have ample spare capacity to bind O2.

 

[Patoux01]

Pleasure. The physiology is right but the amount of CO required would be off the scale.

Hmm, I'm not quite convinced.

From what I've read here, usually "bad air" turns out to be quite heavily spoiled, not by just 3ppm, so depending on the levels that could be involved, I wouldn't rule it out.

 

[St John the Diver]

Sorry, you don't provide enough data to make a credible claim. Before your argument (there isn't enough CO in a bottle of dil to saturate the hemoglobin) can be discussed, you have to provide the capacity of the diver's blood cells to bind CO. Your claim is that there isn't enough CO in a bottle of dil to make an impact on the diver's hemoglobin. That claim is invalid, untestable, unfalsifiable until you document that the hemoglobin in ~5L of blood can bind all the CO in a bad bottle of dil and still have ample spare capacity to bind O2.

>yawn<

Do your own math. And then share it.

One thing that AH has is good gas. It's not likely that this is the root cause. But it'll be an easy one to rule out. One if the first things that NEDU will do will be to analyze gas.

 

[KDAD]

AH has good gas. Until they don't. Since two divers may have been stricken during the dive it is understandable that bad gas is suspected.

May be that one diver dove a little too aggressive that day and stumbled a bit upon climbing into the boat and the other didn't close his DSV.

I do enough troubleshooting of things not to rule anything out, no matter how coincidental. The two incidents can be related or totally separate from each other.

 

[cerich]

>yawn<

Do your own math. And then share it.

One thing that AH has is good gas. It's not likely that this is the root cause. But it'll be an easy one to rule out. One if the first things that NEDU will do will be to analyze gas.

you're assuming there was any dil left to check...

 

[St John the Diver]

AH has good gas. Until they don't. Since two divers may have been stricken during the dive it is understandable that bad gas is suspected.

May be that one diver dove a little too aggressive that day and stumbled a bit upon climbing into the boat and the other didn't close his DSV.

I do enough troubleshooting of things not to rule anything out, no matter how coincidental. The two incidents can be related or totally separate from each other.

Yup. The good news is that (unlike most of the other theories mooted) gas analysis is both easy to do and certain to be done.

 

[St John the Diver]

you're assuming there was any dil left to check...I am leaning to there wasn't

Doesn't need to be. In the lab environment a sample can be pulled using a vacuum and analyzed. Piece of cake. Think lab gas chromatograph analysis, not silly Dreager glass tubes. NEDU has all of the resources.