Rebreather Discussion from Brockville Incident

[dfx]

Rebreathers have been sold in Europe as "meeting" the rebreather standard EN14143:2003 when this is completely untrue insofar no electronic rebreather available to the general public since 2003 meets the required "Functional Safety" (i.e. Clause 5.13.1 of the standard EN14143:2003). This is FACT

[citation needed]

 

[gianaameri]

[citation needed]

The source is from information obtained under the Freedom of Information Act from authorities in the U.K. and other direct enquiries.

It is a well known fact in the industry (it is just not publicised which is why you may have never heard about it).

 

[InTheDrink]

I'm not experienced on CCR - I had to abandon after ~20 or so hours after a near death experience.

I certainly was primarily to blame, for numerous reasons you can read on another thread here.

But @Chris, I think you're being disingenuous or naive if you don't think CCR carries a higher risk. We've dived together or same boat so this is not a personal attack - I have the utmost respect for you and you operation.

But I keep seeing CCR divers get into trouble. Perhaps, much like me, people are getting into CCR for a) the wrong reasons and b) when they're not ready for it

This is one of the reasons the MKVI scares me. I pray that I am wrong but stats so far aren't exactly promising.

 

[abnfrog]

The point surely is that in a number of forums and seminars over the years, the consensus among dive industry pros working on and with rebreathers has been:
Use a Checklist
Dive within your certification level (unit specific)
Carry off-board bailout

I no longer have to send Happy Birthday cards to two friends for failing to follow that last guideline... and several because they ignored one or both of the first two.

SIMPLE pieces of advice but they opted not to follow them and now are dead. Is that the rebreather's fault? I don't think so, do you?

speaking as a rb diver from 1978 till now ..AND IM STILL here despite myself .......i do all 3 so i must be doing somthing wright (and by the way teaching the same ................also by the way everything you do in life IS TRYING TO KILL YOU ..some more than others

 

[dfx]

The source is from information obtained under the Freedom of Information Act from authorities in the U.K. and other direct enquiries.

It is a well known fact in the industry (it is just not publicised which is why you may have never heard about it).

[dubious] [vague]

:tongue:

Sorry, but you're gonna have to try harder to make your claim credible. Simply stating that it's a "FACT" doesn't make it so, even if it's in caps.

 

[flots am]

Yet, nearly 10 years later we haven't seen any clear evidence of any of the mainstream commercially available rebreathers killing anyone due to a design flaw.

It's more insidious than a design flaw that you can point at and say "there it is!". The flaw is in the existence of SCUBA equipment that will silently become an underwater anaesthesia machine, if you don't do everything perfectly on every dive.

Since humans aren't perfect, the rebreathers just patiently wait for someone to screw up.

flots.

 

[TSandM]

I find the discussion fascinating.

I don't disagree at all that most rebreather accidents are human error, although I think we don't ever hear the end of a good many of them (just as we don't know the cause on many OC accidents, either).

If a system is designed to be sufficiently complex that the likelihood of a lethal human error reaches a certain threshhold, can the system be held blameworthy in the subsequent accidents? Human are inherently error-prone, particularly where operating in complex systems where perfect performance is required for safety. In many settings (operating rooms and cockpits being two I have some personal knowledge of) a lot of analysis has gone into how to streamline systems and how to incorporate fairly rigid cross-checking protocols to allow us to function in complex settings with minimal error. I do not believe that the same degree of scrutiny has been given to rebreathers.

I do think that it is possible to dive them with nearly perfect safety (as much as is possible when you are underwater) if the rebreather is simple enough, and the diver is sufficiently trained and has the right temperament and mindset. I have friend who do this. But I don't think that people who sell the units or instruct on them may be doing enough to filter the users to select for "rebreather-optimal" people -- and this may be an area, much as technical and cave diving are, where significant selection is critical.

 

[dreamdive]

It's more insidious than a design flaw that you can point at and say "there it is!". The flaw is in the existence of SCUBA equipment that will silently become an underwater anaesthesia machine, if you don't do everything perfectly on every dive.

Since humans aren't perfect, the rebreathers just patiently wait for someone to screw up.

flots.

How much do you know about anesthesia and our anesthesia machines?

"Do everything PERFECTLY" on EVERY dive"????? I wish I would be as "perfect" as the machine I am diving! Looking and learning from "Root-Cause-Analysis" in anesthesia, I will tell you that it is RARELY ONE event that caused a death. More likely, (as in aviation and CCR diving), it is a multitude of events that finally lead to a total UNRECOVERABLE failure. The drugs we use will perform very well in the right patient. Giving the wrong drug/amount to the right patient or right drug/amount in the wrong patient can lead to adverse outcome. My anesthesia machine is not responsible (very very rarely), but the operator may be.

I am also a parachute rigger and it is rarely a parachute failure that kills a skydiver. Over 90% of adverse outcomes are directly related to the user. Whether we are skydiving, hang-gliding, OC or CCR diving, motorcycling, or driving to work.....it all carries an inherent risk. Driving a car and not expecting to be ever in an accident is exhibiting unrealistic thinking. Jumping out of a plane and not having considered that equipment failures may lead to death is unrealistic (FYI, sport jumpers have two parachutes: a primary and a reserve plus they may have an AAD (automatic activation devise) that will deploy a reserve chute in case the jumper did not activate his/her primary chute).

Engaging in diving and not considering that (unless we develop gills) we are dead without our life support equipment (being OC or CCR) is unrealistic. What I am getting at is that we all, on a daily basis, engage in some form of risk and CHOSE to accept it or else not engage in it.

As a CCR diver I have a heck of a lot more options available than when I was Tech OC. That being said, I don't think a direct comparison is makable. I dive a lot deeper than I would ever been able to do on OC. Thus my total risk profile is greater CCR and OC. I dive caves a lot more comfortably knowing I don't have a "clock"(i.e. backgas supply) ticking. YES, diving CCR is more complex than diving OC BUT it also gives me more options than I have OC in case of a failure! That being said, I still hear about how CCR diving is causing all these deaths.

WERE ARE THE NUMBERS RELATED TO OC DEATHS????

A few months ago I was on a dive boat and we heard on the radio how they pulled an OC female diver out of the water dead. I kept looking for a report in the local paper and could not find ANYTHING! Guess it lacked the sensationalism, since if she had been CCR, it would have been reported for sure. Right? It's called reporting bias.

If we were to conduct an analysis on cave diving deaths between OC and CCR, I wonder what the numbers would be. About 1.5 to 2 years ago, a well known female cave diver died in a cave on OC. She was certified on an Optima unit but on her sad day, was OC. Although this is my personal speculation, I wonder if the CCR unit would have given her sufficient time to find herself out of the cave. Her back gas supply certainly did not. What a shame! What a waste! Thinking about this makes me so sad! I am so sorry it happened to her!

There are people who are trying to make an argument AGAINST recreational CCR diving. The pro's and con's and relevance would need to be discussed elsewhere. People die on OC and considering that lobster season is coming up, soon, I wonder how many will die trying to catch bugs this year.

Sorry if I appear to be ranting, but there are so many different things and ways to approach and think about this. Please stop comparing apples with starfruits. Unless you can conduct a randomized controlled study with a sufficient sample size to have OC and CCR divers of all different rebreather manufacturers dive the same type of dives and THEN look at the outcome data, you will continue guessing and conjecturing about NOTHING.

Let's face it: if you jump into the water without turning your tank on (OC or CCR) you could die! A rebreather has a few more checks to go through than a OC set-up, but we also have check-lists. The only thing that can kill you is YOU (not the unit).

There are Pro's and Con's to diving CCR. Focusing on rebreather deaths is definitely not a Con!

Thank you!

Claudia Roussos MD

---------- Post added July 4th, 2013 at 10:29 PM ----------

I find the discussion fascinating.

I don't disagree at all that most rebreather accidents are human error, although I think we don't ever hear the end of a good many of them (just as we don't know the cause on many OC accidents, either).

If a system is designed to be sufficiently complex that the likelihood of a lethal human error reaches a certain threshhold, can the system be held blameworthy in the subsequent accidents? Human are inherently error-prone, particularly where operating in complex systems where perfect performance is required for safety. In many settings (operating rooms and cockpits being two I have some personal knowledge of) a lot of analysis has gone into how to streamline systems and how to incorporate fairly rigid cross-checking protocols to allow us to function in complex settings with minimal error. I do not believe that the same degree of scrutiny has been given to rebreathers.

I do think that it is possible to dive them with nearly perfect safety (as much as is possible when you are underwater) if the rebreather is simple enough, and the diver is sufficiently trained and has the right temperament and mindset. I have friend who do this. But I don't think that people who sell the units or instruct on them may be doing enough to filter the users to select for "rebreather-optimal" people -- and this may be an area, much as technical and cave diving are, where significant selection is critical.

I can attest to this: Peter Sotis, ADDHELIUM, will not certify unless he thinks you met his standards - OC or CCR! You cannot buy your C-card from him. You will have to earn it!

 

[doctormike]

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.

Hi, Claudia…


Fair enough, and perhaps I should have done a more thorough critical analysis of the paper, and a wider literature review to truly gauge the validity of the authors conclusions. SInce you are well qualified in this particular field, I'll take your word for it about the biases, etc… you are right that I shouldn't cite weak data here.


But I do have some experience in academic medicine (40 peer reviewed papers, 30 books, chapters and review articles, and on the editorial board of an AMA journal for 10 years). So yes, I totally agree with you that not everything that is published is valid. However, peer reviewed journals (like DHM) do tend to weed out many of the statistically poor studies.


The one problem that you mention with the Fock paper is the phrase "fatality rates … ranging from one in ten users", implying that the authors are suggesting that the fatality rate for CCR is 10%. That sentence fragment is taken from the discussion section of the paper, where authors review the background literature about the topic at hand. It seems totally reasonable to set the stage by stating the range of previous conjecture in the discussion, since this is not actually used to support the conclusions of the paper. Their actual relative risk numbers are drawn from other published data.


I also know enough about study design to know that you would never be able to accurately answer the question about relative fatality rates, because of the very nature of the question. Your study would be tainted by inclusion bias, inadequate datasets and design issues. To accurately answer the question of relative risk of OC and CCR, and to screen out the dive profile variable, you would need to have matched cohorts of divers, randomly assigned to dive OC or CCR on matched dives, and you would need a VERY large number of dives to achieve statistical significance. Obviously, you can't do such a study. So we are stuck with a review of fatality databases and necessary assumptions, with all the unavoidable data reporting contamination. There will always be insufficient data to answer this question. But that doesn't mean that the paper is useless… Like any published paper, it doesn't exist in a vacuum, but is one piece of a larger puzzle.


You do make a good point, however, that there are some situations where CCR may be more safe than OC (entanglement, entrapment, or any other time where gas reserves suddenly become an unanticipated limiting factor).

---------- Post added July 4th, 2013 at 11:51 PM ----------

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.

Hi, Chris...

Thanks, and I do appreciate what you are saying. I guess to really answer this question, we would need to compare injury and fatality rates for matched cohorts of dives (see my response to Claudia), and that's just something we will never be able to do.

I think that the best analogy that i can think of for my point here is tightrope walking. Which is more dangerous - walking across a rope 12 inches off the floor, or the same rope across the Grand Canyon? It's the exact same activity, the exact same opportunities for error, but in the latter situation, the price of error is much higher. That's the impression that I get about rebreathers, where you can make one small omission and it can be fatal (like that guy who passed out in 4 feet of water in the quarry).

Maybe OC and CCR are just as safe for deep technical diving, where the benefits of much greater gas reserves and of the variable O2 mix offset any CCR specific risks. But for me (a recreational diver), it doesn't seem that the same tradeoff is there...

 

[gianaameri]

[dubious] [vague]

:tongue:

Sorry, but you're gonna have to try harder to make your claim credible. Simply stating that it's a "FACT" doesn't make it so, even if it's in caps.

It is a fact because it simply is.

Everybody in the industry knows about it.

No electronic rebreather available to the general public meets the "Functional Safety" requirements of the rebreather standard EN14143:2003 (i.e. Clause 5.13.1 of EN14143:2003).

I am not surprised you find it hard to believe as this is something you won't read in any rebreather advertisement or manual, but you pay $10k or so for a machine which does not have the "Functional Safety" required by the standard against which the machine you purchase is benchmarked and certified (i.e. against the EN14143:2003 rebreather standard).

Manufacturers say that they either cannot meet such requirement (i.e. it is impossible for rebreathers to be built to meet the "Functional Safety" requirement) or that it would be too expensive to do so (i.e. consumers would not be willing to pay the price required for such level of safety or sophistication).

It is what it is.

Rebreathers are extremely dangerous and it is either the case that they cannot be made safer than they are or that it is not economical for the industry to do so.