Fiona Sharp death in Bonaire

[Storker]

Facts sent to me from an Insider:

Fiona was diving 20/20, setpoint controller and computer set to air, dive to 91M with a 4M/min ascent/descent rate, and whatever happened to her happened at the 80
Foot stop.

91m on 20/20 is an END of 70m and a gas density of about 10 g/L. That's hotter than even some CMAS 3* certs allow for (60m on air). And that would be on OC, which has a lower WOB than an RB has.

 

[Brad_Horn]

Someone will correct me if I'm wrong, but I would dismiss the idea a gag strap would have changed the outcome. The purpose of the gag strap is largely for jaw fatigue during long deco and/or to buy time for a buddy to assist a diver that is toxing. You also have to remember that it takes a conscious human to control whether their airway is open or not. A gag strap would not do this for you and assuming you could get a perfect seal on the mouthpiece to keep water out while unconscious you would still likely embolize on the way up to the surface.

Worth reading Paul Haynes article, ‘Increasing the probability of surviving loss of consciousness underwater when using a rebreather’, page 253 https://www.spums.org.au/file/574/download?token=SLGDpN2q#page=59

Some form of gag strap has only been required for all rebreathers passing testing to EN14143 for CE since 2003……

I'm not up on the latest from that tragedy, but in that case the gag strap might have prevented the loop from flooding on the surface, causing him to sink after he lost consciousness, presumably from DCS, right? So they might have been able to recover him and resuscitate him if he were floating and unconscious.

If only divers could go a step further and have a BOV, that comes with a gag-strap, that triggered auto-bailout (by physically pulling on its necklace) to OC on removing the BOV from your mouth on the surface. Closing the loop, allowing instant access to a known safe gas and sealing the rebreathers inherent buoyancy in.
Thats right, this basic safety feature has been available for a while now, see: https://www.facebook.com/pg/OpenSafetyEquipment/photos/?tab=album&album_id=151310394898469

@doctormike has there been a documented study on loss of consciousness recovery while ccr diving with FFM?

NEDU at the DAN 2009 Tech Conference details the recovery of a couple of Hypoxic Mk16 divers. Also Ex19 recovery from water blocked cells.
pg249 https://www.diversalertnetwork.org/files/Tech_Proceedings_Feb2010.pdf

Yes, Rob Stewart's computer data leans toward DCS (12 minutes omitted deco + rapid ascent of 75 feet/minute or 23 meters/minute)/hypercapnia/dwelling.
His computer data shows the PPO2 never went below 1.0, so hypoxia is not supported.

How much opportunity for water blocked cells was there on the two units? Resulting in the dive computer then displaying a higher PPO2 than the actual gas contents of the loop the diver is breathing.
Note recent document updates about this risk in yellow http://www.deeplife.co.uk/or_files/DV_O2_cell_study_E4_160415.pdf

 

[Brad_Horn]

91m on 20/20 is an END of 70m and a gas density of about 10 g/L. That's hotter than even some CMAS 3* certs allow for (60m on air). And that would be on OC, which has a lower WOB than an RB has.

What's result on diving air; when the WOB as tested by NEDU of an Inspiration at 300ft on Heliox is 2.98J/L at 75lpm?

per NEDU - Work of Breathing limits for Heliox diving - TA 10-06

 

[doctormike]

Not necessarily, if you were working hard you would have to add more often than you normally would. And if you had a rather low bottom PO2 for whatever reason. If you had a needle valve and you hadn't opened it enough or it had accidentally closed, the addition rate wouldn't be what was expected. All of which could lead to a hypoxic scenario in not a long amount of time, although there would definitely be a failure on the divers part to allow any of that to happen.

Remember with an mCCR you either set your orifice size (CMF) below your metabolic rate, or with a needle valve, you tune it to your metabolic rate and depth. If your workload suddenly increases, you either have to add more often in the case of a CMF orifice, or you have to open your needle valve to compensate, and/or add more often. If you don't compensate for your increased workload, your usual addition cycle gets out of whack. Get too complacent and PO2 tanks too much.

Right, I understand, I was just saying that would involve a lack of PO2 monitoring.

But not diving an mCCR, I probably don't realize just how fast it can drop if you don't pay attention, if you start from a lower setpoint, and if the orifice is set for a lower workload and/or metabolic rate.

Thanks!

 

[tridacna]

The more I read about rebreathers, the happier I am with OC. Just saying.

 

[doctormike]

The more I read about rebreathers, the happier I am with OC. Just saying.

Adds some safety issues, removes others. And some of these accidents - OC or CCR - are caused by decisions, not gear.

C'mon, I need another New Jersey JJ buddy....

 

[The Chairman]

Unless @John Bantin is willing to share

I already did...

Facts sent to me from an Insider:

Fiona was diving 20/20, setpoint controller and computer set to air, dive to 91M with a 4M/min ascent/descent rate, and whatever happened to her happened at the 80
Foot stop.

Of course, if you have pertinent information you feel should be passed on, I am here for you. I will only pass on info at my discretion that I feel to be reliable.

 

[doctormike]

I already did..

Fiona was diving 20/20, setpoint controller and computer set to air, dive to 91M

So that means 20/20 dil, right? So leaving aside the hot loop issues, that's still an END of 218 FSW.

What does "setpoint controller and computer set to air" mean? Not sure I understand that in the context of CCR. Her decompression stress was calculated with her computer set to air OC bailout? What was the setpoint?

 

[runsongas]

to eliminate the helium penalty on the deco algorithm maybe?

 

[Storker]

to eliminate the helium penalty on the deco algorithm maybe?

So, basically to be able to run a more aggressive deco schedule?