Fiona Sharp death in Bonaire

[Peter69_56]

Man, you'll completely hate the units that only have 2 cells then.

You would be right in that statement, hehehe. I like redundency and two cells doesnt make me a happy chappy

 

[Peter69_56]

This makes me wonder as she ascent to 80’, not far of the slope, she would be either in neutrally or slightly positive buoyant and she went unconscious at that bottom of the slope at that depth. Her jaw dropped, the regulator fell out of her mouth, her lung and the CCR filled up with water. She drowned, became negatively buoyant and sank to the bottom of the slope. Had she put on a gag strap, would it be possible for her to still be floating motionless in mid water and even slowly floating towards the surface, alerting the rescue class divers who happened to be in the vicinity to rescue her?

How many of you CCR divers are wearing gag strap during CCR diving?

Good point. SInce I changed my mouthpiece for a BOV the loop strap has gone. Maybe time to get that sorted!

 

[Peter69_56]

I would say its not a CCR vs OC thing.
"lying" about your helium content is a holdover from the past (and it sounds like Fiona wasn't a new kid to deco or tech diving in general). The era of having an actual believable deco computer is pretty damn recent IMO. As recently as 8 years ago the options included units like the nitec-he which would generate 2 hrs at 10ft if it had the slightest wiff of helium entered.

I guess the point is that trimix divers of the 1990s and early 2000s eras have been "lying" to their computers for a long time and in many cases continue to do so because it has worked for them in the past.

For the risk in this look up articles on Normalised Deviation

"Worked for me in the past"

 

[Dan]

Interesting reading:
OXTOX: If You Dive Nitrox You Should Know About OXTOX — DAN | Divers Alert Network — Medical Dive Article

The Table 2, below, from the above article, shows it'll take an exceptional exposure of 30 minutes at PPO2 = 2.0, before OXTOX.

 

[doctormike]

For the risk in this look up articles on Normalised Deviation

"Worked for me in the past"

I’m normally the first one to play the normalization of deviance card, but to his specific point - remember that pretty much all of our tables and algorithms are based on an elaborate version of “worked for me in the past” with a large data set.

 

[Peter69_56]

I’m normally the first one to play the normalization of deviance card, but to his specific point - remember that pretty much all of our tables and algorithms are based on an elaborate version of “worked for me in the past” with a large data set.

Agreed Dr Mike, but at least we are using a large data set for these calculations.

For the person who says its worked for ME in the past, the data set is pretty tiny by comparison.

 

[doctormike]

Agreed Dr Mike, but at least we are using a large data set for these calculations.

For the person who says its worked for ME in the past, the data set is pretty tiny by comparison.

I agree. But as usual, the devil is in the details.

 

[wedivebc]

As I said, they don't normally dive that way and we weren't in a cave. I don't stare at their HUD, but I have never obseved them flash red momentarily let alone sustain red flashing for any length of time. I also doubt they had concerns about reducing CNS stress on a max 30 foot dive.

You're completely missing my point. You interpreted a red flash to indicate an abnormal condition when in fact there could be any number of reasons a person would allow the PO2 to drop slightly on a dive without any concern to the diver. Since you are obviously untrained in the operation of a rebreather that uses a smithers algorithm (which is quite a few differrent models) you perceived a problem where none existed. This is why I think buddy HUDs are not a good idea, which is the point I was trying to make.

 

[rjack321]

For the risk in this look up articles on Normalised Deviation

"Worked for me in the past"

I was pointing out why people, especially "old timers", lie to a computer.
Hell there weren't really even commercial tables that people actually dove as recently at 2000, they were constantly experimented and tweaked with. "Normal" is not a static thing and it sure as heck isnt defined by bulhmann and gfs which everyone seems to think it is lately

 

[doctormike]

You're completely missing my point. You interpreted a red flash to indicate an abnormal condition when in fact there could be any number of reasons a person would allow the PO2 to drop slightly on a dive without any concern to the diver. Since you are obviously untrained in the operation of a rebreather that uses a smithers algorithm (which is quite a few differrent models) you perceived a problem where none existed. This is why I think buddy HUDs are not a good idea, which is the point I was trying to make.

Right. But the scenario where a buddy light would be helpful wouldn't be the one that they described - non-rebreather divers observing some random CCR diver. I agree, they have no business trying to interpret a HUD that they are not trained to use.

The idea (as implemented by JJ and on some Meg models) is that there is a unique alert that indicates a PO2 out of range, that is visible to a buddy. All that means is that it's not a bad idea to check to see if your buddy is normally responsive, and responding to the alert. I don't see the problem with that. I really wish that Shearwater would stick one of those on the back of the NERD, that's the one downside of swapping out the stock HUD.

In the case shown in this video, the fact that the buddy noticed an alert (on the wrist controller) may have saved a life. If the diver had his controller rotated to face him, it might not have been noticed until it was too late: