Rebreather diver dies in 6 feet of water - Cyprus

[joshk]

One claimed advantages of a leaky valve is to act as a backup in this situation.

Strange testing methods described there. Am I correct to understand one unit had the O2 off and the manual unit had it on? I suppose the test for the case of a 10+ minute distraction while the electronics have failed but you were required to stay on the loop?

 

[doctormike]

Strange testing methods described there. Am I correct to understand one unit had the O2 off and the manual unit had it on? I suppose the test for the case of a 10+ minute distraction while the electronics have failed but you were required to stay on the loop?

I'm assuming two identical manual rebreathers, one with a leaky valve and one without. Neither test subject was allowed to add O2 via the MAV.

They don't give a lot of details, and I suspect that this wouldn't past the ethics committee of an Institutional Review Board! The test diver walking around with no O2 and only air dil was at some real risk - I don't know if they really let him get to 0.14. Apparently you can induce a stroke or heart attack even if you are doing this on dry land and "rescue" the subject with O2 once they pass out.

One of those hypoxia tests involved giving the test subjects a switch that would turn on the O2, all they had to do was throw it. Apparently they just sat there until they were unconscious, and later were under the impression that they had thrown the switch even though they never did.

I guess the point was to show you how quickly the PO2 decays as you metabolize the O2 from air without replacement. Like that case at the quarry with the disconnected O2 feed.

 

[joshk]

I guess the point was to show you how quickly the PO2 decays as you metabolize the O2 from air without replacement. Like that case at the quarry with the disconnected O2 feed.

My point is that operating a unit without O2 and a unit with a constant flow of O2 doesn't make for much of a test. This is like operating one without a scrubber and one with. Of course you will pass out far faster on the unit without the scrubber. With one in you will still pass out, however after many hours.

 

[doctormike]

My point is that operating a unit without O2 and a unit with a constant flow of O2 doesn't make for much of a test. This is like operating one without a scrubber and one with. Of course you will pass out far faster on the unit without the scrubber. With one in you will still pass out, however after many hours.

I guess the point was that the leaky valve gives you some backup in case you don't monitor your O2 and expect the unit to take care of it (i.e. eCCR). It's just to drive home the point that this can happen relatively quickly, and in at least one case that I know about (and maybe the OP case as well), this was what happened.

 

[diverintheflesh]

Analysis of recreational closed-circuit rebreather deaths 1998-2010. - PubMed - NCBI

"Analysis of recreational closed-circuit rebreather deaths 1998-2010 The 181 recorded recreational rebreather deaths occurred at about 10 times the rate of deaths amongst open-circuit recreational scuba divers. No particular brand or type of rebreather was over-represented. Closed-circuit rebreathers have a 25-fold increased risk of component failure compared to a manifolded twin-cylinder open-circuit system. This risk can be offset by carrying a redundant 'bailout' system. Two-thirds of fatal dives were associated with a high-risk dive or high-risk behaviour. There are multiple points in the human-machine interface (HMI) during the use of rebreathers that can result in errors that may lead to a fatality."

Every time I hear of another diving fatality, I'm saddened. On rebreathers in particular, while the machine is an amazing piece of hardware, the human operator still, is not.

 

[Kay Dee]

AJ, it seems you have developed lock jaw when it comes to answering my qustion as to whether you dive OC or CCR?

Any chance of ever getting an answer to that?

And although I liberated the following from the above post, may I respectfully say that you woud do well to reread it, and take note of what I have now highlighted, if for nothing else than educational purposes. (And my apologies to the original poster - diverintheflesh- that I 'liberated' it from.)

"Analysis of recreational closed-circuit rebreather deaths 1998-2010 The 181 recorded recreational rebreather deaths occurred at about 10 times the rate of deaths amongst open-circuit recreational scuba divers. No particular brand or type of rebreather was over-represented. Closed-circuit rebreathers have a 25-fold increased risk of component failure compared to a manifolded twin-cylinder open-circuit system. This risk can be offset by carrying a redundant 'bailout' system. Two-thirds of fatal dives were associated with a high-risk dive or high-risk behaviour. There are multiple points in the human-machine interface (HMI) during the use of rebreathers that can result in errors that may lead to a fatality."

AJ, If you would be so kind, would you mind answering the question from my first post, i.e. do you dive OC or CCR?

TIA

By the way, did you bother to read the following? Note the last line (now underlined). Like I said, and not just with this review, a PROVEN fact!