High PO2 near miss

[CuzzA]

From the comment section on YT...

László Mocsári3 days ago
Thank you for commenting! The HUD was not disconnected, probably his vision was overshadowed by the light of the video because that is very strong (2 x 3700 lumens). The flow of the open stuked solenoid is very high, a few seconds of free flow are sufficient to raise PO2 greatly. Marcelo told me that when he realized the PO2 was in 2.0, that is, a few seconds after the end of the sena of the film of shows the computer blinking. I already went through similar situation and finished the dive doing manual flight in the same way.​

 

[doctormike]

The one complaint I had on the NERD was SW's mounting bracket for the Prism 2. It was the cloth strap. I know the JJ has a rigid bracket. I ended up printing one for my unit which works very well.

Yeah, the HUD / NERD mount on the stock JJ DSV is really sweet, locks it in place perfectly. That was one concern I had about switching to the shrimp BOV, I would lose that hard mount. Might ask you to print me one someday!

 

[doctormike]

Are there not audible alarms on the Shearwater for high or low po2?

I know that this is somewhat of a controversial issue in OC diving on SB. I don't think that you will find many rebreather divers with an audible alarm on their computers. One exception that I know about is the Hollis Explorer which has some sort of vibrating alert in the mouthpiece.

One argument against audible alarms is that they promote complacency - the idea that if the alarm isn't going off, then everything is OK. CCR divers have "always know your PO2" drilled into them pretty thoroughly, but obviously (from the video), not everyone does that.

 

[doctormike]

There is a possibility that he had bailed out at a lower PPO2 (why not dil flush instead if it was that bad?)

This came up on CCRExplorers.

I'm a new CCR diver, mod 1 TDI. In my training, we did different drills for high PO2 up to 1.8 and for high PO2 over that. We did dil flush for the first scenario, and an initial bailout/shut down O2 the the second scenario before diagnosing. Are there other standards that recommend dil flush first no matter what the PO2?

 

[RainPilot]

Two observations that I made (also as a non-CCR diver)..

1. His computers appeared to be mounted in a sub-optimal way. This is very obvious at the point where the camera picks it up. The diver has both arms in a natural relaxed position, and his computers are pointing away from him. I orient my computer so it is on the inside of my forearm, so when my arms are relaxed the screen is facing towards me, not away from me. Yes, his HUD should have warned him too...

2. He didn't see to be particularly aware and comfortable in the water. Especially at the stop, hanging vertically, grabbing onto the anchor line with his legs? Yes, he was probably out of sorts and task loaded, but still.... Also, hanging onto his BO 2nd stage? Is that standard protocol? I would've thought the preference would be to clip it off?

Neither of these observations may have anything to do with why this all occurred, but IMO they speak volumes to his general comfort, experience and situational awareness..

He is holding the bailout reg so he can transition immediately if the loop has an issue. Also he is very task loaded, if there's something to hold onto by all means. I'd rather not go hyperoxic because I'm too busy trying to maintain depth.
It's one thing to be able to do something, doesn't always mean it's the best choice.

 

[doctormike]

He is holding the bailout reg so he can transition immediately if the loop has an issue. Also he is very task loaded, if there's something to hold onto by all means. I'd rather not go hyperoxic because I'm too busy trying to maintain depth.
It's one thing to be able to do something, doesn't always mean it's the best choice.

Yeah, exactly. Those GUE instructional videos are great where someone is demonstrating a skill, when they look like they are embedded in Jello, in perfect trim. Actually doing it in an emergency is another thing entirely, especially when you are feathering your O2 on and off, which is filling the loop, etc...

I don't think that his method of dealing with an ascent, a deco obligation, a stuck open solenoid and the potential need to bail out again is so bad. Using his legs to hold the line frees up both hands. He doesn't have a BOV or a necklace bungee - I would probably hold my bailout reg as well in that situation as well, rather than clipping it off. Fine motor control goes quick in hypoxia / hyperoxia / hypercapnea - I wouldn't assume that I could deftly unclip and redeploy my reg if I needed it.

 

[Bob DBF]

Preface by saying I have nothing but academic interest in rebreathers, and also I am no fan of audible alarms, underwater or anywhere, having heard my share long ago.

I know that this is somewhat of a controversial issue in OC diving on SB. I don't think that you will find many rebreather divers with an audible alarm on their computers. One exception that I know about is the Hollis Explorer which has some sort of vibrating alert in the mouthpiece.

One argument against audible alarms is that they promote complacency - the idea that if the alarm isn't going off, then everything is OK. CCR divers have "always know your PO2" drilled into them pretty thoroughly, but obviously (from the video), not everyone does that.

It would seem to me that having an audible alarm for missing visual alarms, by not correcting the issue, would warn the diver that if he is not dead he will be soon, and may warn his buddies as well. The alarm being after the visual alarms, not instead of them. An audible alarm for a near(?) death experience is not the same as having one for every parameter imaginable on the wrist of an OW diver that does not know it was even set, or what it is for.


Bob
-------------------------------------
... just thinking.

 

[doctormike]

It would seem to me that having an audible alarm for missing visual alarms, by not correcting the issue, would warn the diver that if he is not dead he will be soon, and may warn his buddies as well. The alarm being after the visual alarms, not instead of them. An audible alarm for a near(?) death experience is not the same as having one for every parameter imaginable on the wrist of an OW diver that does not know it was even set, or what it is for.

Not totally unreasonable. I'm too much of a CCR newbie to have a strong opinion one way or the other, and I know that there are technical issues with this, but I can see this being like a stall alarm on an aircraft. If even 747 pilots have them, maybe not a bad idea?

The Inspiration rebreathers have an audible alarm, I don't know any others that do. One issue with an alarm is that if it goes off a lot, sometimes it gets ignored with tragic results. An example of this is Phil Gray.

 

[RainPilot]

My unit (Poseidon) has an audible alarm for critical failures along with a vibrating mouthpiece and a flashing HUD. When the audible alarm goes off the big red buddy light on the back flashes to let everyone know you have an issue in case you are incapacitated. Slight issues have a flashing HUD and vibration to prompt you to look at the display to see what's cooking.

 

[Bob DBF]

One issue with an alarm is that if it goes off a lot, sometimes it gets ignored with tragic results.

Yeah, I was in one that put several thousand gallons of salt water inside a submarine. Ours was not tragic, but we were trained for a bad day.


Bob