Rebreather Discussion from Brockville Incident

[doctormike]

I believe we are talking at cross purposes. There is no question that rebreathers are more complex than say OC. The point of my post was to mention that there are some simple "best practices" that the rebreather community has endorsed to help alleviate operator error.

Absolutely, I totally agree. I just feel that there should be some recognition that the underlying activity is more complex and the consequences of variation from those practices are more severe with CCR than with OC. That's why I posted that link to a fairly large study in the Diving and Hyperbaric Medicine Journal. As you will see, despite the significantly increased risk they found for recreational CCR (about 10 x the mortality as OC), this was mostly due to operator error, and their conclusion was that the "major emphasis should be on reducing human error"

And the rebreathers made that decision? I do not follow the logic. Sorry.

Not sure what you mean by rebreathers making the decision. I said that it sounded like (based on the limited information that you gave me) that the decision of those divers to dive a rebreather (as opposed to OC) contributed to their deaths, because of the increased likelihood of human error causing catastrophic consequences.

It seems that you are saying that rebreathers are just as safe as OC as long as you always follow this exact and extensive set of procedures. My point is that we are all human, and we know that we will someday make a mistake. It's OK to choose dive gear that makes the cost of a mistake so high, but we should make that choice with open eyes, and not be reassured that there is no risk difference between OC and CCR.

THANKS but their deaths... more than two sadly... have to be used as an object lesson for those of us that continue to dive and teach on rebreathers. Not to do so would be, in my opinion, disrespectful.

Again, we are in total agreement.

 

[Chris Brown Tech]

" to imply that the technical complexity of rebreathers plays no contributing role in facilitating operator error is wrong.

Hi Mike, sorry, but I couldn't disagree more in the context of TECH OC and TEC CCR, (although I would tend to agree comparing a rec no stop dive to CCR.) People are dying on rebreathers NOT because of any complexity associated with the machine, they are primarily dying because they have a physiological issue or they did not use a check list or carry bailout. After that, there are some that died because of lack of maintenance, using old cells or not monitoring their equipment.

All of the above is directly comparable in complexity to tech open circuit where divers die primarily form physiological issues, breathing the wrong gas or diving beyond their level of competence.

But there is evidence to support this.

Steve and I are both living and breathing CCR's on a daily basis as our job and have good visibility of all the expert data, research, common understanding, best practice and information from accident investigations that cant always be shared. The paper you linked to does not support your conclusion IMO. It is also highly controversial both in its source data (which is flawed) and the statements drawn from it. The paper does clarify that there are no real conclusions, so in a way it makes statements and then withdraws them as being a best effort based on the scant data available. I would recommend you have a look at the debates raging on rebreather world and CCR explorers forums for the full debate on that paper if you are not already involved. Your medical background would be useful

Regarding the warning messages posted on a CCR, thats just common sense and good for risk management / liability protection. Im sure if a scuba manufacturer built a complete OC tech rig including double tanks, manifolds, stages, deco tanks, regs, hoses, harness and wing and sold it as a single unit - then they would have a sticker with very similar warning

 

[Garth]

I tend to think this discussion might benefit from a separate thread. I am a newer CCR diver 6-7mo. 30-35 hours and I find myself completing my checklist multiple times prior to my dives because for some reason it makes me feel better and more at ease when I enter the water. I don't think it is trying to kill me and I must stop it. I do however acknowledge that humans are at times unreliable when it comes to monitoring, and our perceptions are easily affected by environmental stimulation. Has anyone seen the The brain games show on Discovery?

I assemble my gear at home with a checklist, review the assembly a second time with a checklist prior to placing it in my truck, go over an abbreviated jump checklist and even have a standard disassembly routine with cleaning/drying/storing. This seems to work for me when running through a checklist at the very least touch the device to be checked and ensure function.

From my understanding the manufacturer has little to do with the safety of the CCR as long as it is dove in the intended way, in the intended depth rating of the manufacturer, for the intended duration of the rebreather.

I agree with Chris that the symbol is certainly a risk management warning for a machine that is fully assembled and sold as a "unit."

I love diving my CCR and find myself more aware while diving it due to the absence of extremely loud bubble exhaust.

Cheers
Garth

 

[doctormike]

People are dying on rebreathers NOT because of any complexity associated with the machine, they are primarily dying because they have a physiological issue or they did not use a check list or carry bailout. After that, there are some that died because of lack of maintenance, using old cells or not monitoring their equipment.

...

The paper you linked to does not support your conclusion IMO. It is also highly controversial both in its source data (which is flawed) and the statements drawn from it.

Again, you obviously know far more than I do about this, and I will take your word for it if there are methodological problems with that paper.

I guess all I'm saying is that complexity in any activity makes human error more of a factor, and makes the consequences of human error more severe. So again, if you are saying that CCR is just as safe as OC for equivalent dives as long as these specific steps and practices are followed every time, without variation, than you certainly aren't convincing me to give CCR a try, because I know that someday I will skip a step or make a mistake or whatever (as in the cases I mentioned above).

I get the sense that you think that I am just dismissing CCR out of hand. I'm not, and I appreciate all of the science, engineering and training that go into letting people like you dive them safely and teach them to others. But I don't think that it serves your cause well to imply that there is no risk difference between OC and CCR, which is the impression that I'm getting.

Regarding the warning messages posted on a CCR, thats just common sense and good for risk management / liability protection. Im sure if a scuba manufacturer built a complete OC tech rig including double tanks, manifolds, stages, deco tanks, regs, hoses, harness and wing and sold it as a single unit - then they would have a sticker with very similar warning

Don't know about that, but I have never seen a statement like that on any piece of OC gear, training manual or other published material. It's the "without warning" thing that gets me...

 

[Garth]

Most of the issues I have heard of from those that I dive with and those that have dove with those I dive with.. Are related to improper assembly, pushing the limits of the sorb, improper maintenance or issues related to the solenoid failing.

I feel confident that I have been trained to accept and manage the issues likely to occur during a dive... It is certainly my responsibility to maintain those skills and awareness of those issues.

---------- Post added July 4th, 2013 at 09:05 AM ----------

Those that tend to forget to maintain the safety skills are most likely more at risk although that would probably be opinion with the lack of evidence.

 

[Chris Brown Tech]

I totally get where you are coming from and Im struggling to give a medical analogy that would both get my point across and not be technically incorrect so I wont bother

Take flying commercial jets as an example. Its obviously a far more complex task than flying a small light aircraft and demands more training and the ability to manage greater amounts of information. Yet the accident rate in PPL light aircraft is much higher than commercial jets. Why is that? It is also true to say that a light aircraft pilot cant get in a jet and fly it without training just the same as an OC diver cant dive a CCR without training.

The difference between flying and diving is one of control and regulation. If you are flying a commercial jet it is maintained to the highest standard and the pilots have continuous training checks and ratings. Not so in rebreather diving. The 'pilot' is free to dismiss as many checks as he deems necessary and to conduct zero maintenance should he wish. Its the ATTITUDE that causes the problem, or the lack of training or both.

The complexity of the unit doesn't really figure that much, as its not complicated to use. Not when trained and used properly within your diving abilities. Is it more dangerous than OC? Well it depends on the context in which it is used. A rec diver with basic training on a single tank in a cenote in Mexico is arguably in a more dangerous position that a well trained CCR diver at 60 feet on a reef in Cozumel in 100' viz with a buddy with both carrying adequate bailout.

So yes, Im comfortable and quite confident saying CCR is no more dangerous than OC. Both have lead to numerous fatalities. Theres no one conclusion that applies to both disciplines in all situations.

 

[dreamdive]

Mike, I am not sure as to your medical background, but if you have training in analyzing published medical papers, you will have to agree that not all that is published is valid or even good! Please go back and critically analyze Fock's paper. It is full of errors, conjectures, and biases. Surely, one cannot accept the opinion of one diver that fatality rates "range from one in 10 users". Likewise, there is insufficient data to conclude and compare death rates between OC and CCR diving.

Studies like these gall the heck out of me, because now that it is published, everybody thinks it has validity and things like "CCR diving is ten times more deadly than OC diving" are being proclaimed as the new mantra.

 

[nadwidny]

my test flights on a rEvo and an Inspiration a few years ago...... pre-flight checklists .....

Planes and pilots fly. Rebreathers and divers dive.

 

[gianaameri]

Planes and pilots fly. Rebreathers and divers dive.

Planes are properly certified to meet Functional Safety and proper investigation and accident analysis is carried in accordance to established protocols.

Rebreathers are precisely the opposite.

Rebreathers lack Functional Safety (and this has been kept hidden to the end-user).

Rebreathers fatalities are not properly investigated (and many times are brushed under the carpet so we do not really know much about a fatality even occurring). Once it is established that no foul play was involved, police drops the investigation, and unlike in commercial airlines, there is little social and economic pressure to get to the bottom of cause of the incident.

Pilots and rebreather divers background and training are also very different.

Comparing flying and rebreather diving is a bit like comparing apples and oranges.

As to some other comments I have read, they are more like posts by vested parties interested more in selling/promoting rebreathers than to discuss a fatality and learn something from it.

Looking at the data to compare OC to CC the fact is when using a rebreather:

1. Equipment Operating Issues (including machine failure) is the largest fatality trigger
2. Inappropriate Gas is the leading disabling injury (i.e. hypoxia, hyperoxia, hypercapnia)

Rebreather diving is extremely dangerous relative to OC and hopefully with a Poseidon being involved in this fatality at some point in the future the black-box data can tell us more about what actually happened.

Source: https://www.youtube.com/watch?feature=player_detailpage&v=B5TfJCDnzpc#t=1109s

 

[Pedro Burrito]

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