Rebreather Discussion from Brockville Incident

[flots am]

How much do you know about anesthesia and our anesthesia machines?
My anesthesia machine is not responsible (very very rarely), but the operator may be.

You're correct. It's generally operator fault in both cases.

A major difference is that the patient does not operate his own anesthesia machine and it's not used underwater.

flots

---------- Post added July 5th, 2013 at 10:49 AM ----------

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).

An OC failure is obvious (you can't breathe) and can not be ignored, while a CCR failure can be completely silent and un-noticed as it puts you to sleep then kills you.

This is a difference in failure modes that can't be dismissed.

 

[gianaameri]

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

I have read this:

Functional Safety - TMD - Today's Medical Developments

and it seems to me that again there is a night and day difference between medical devices and rebreathers (same as there is night and day differences between airplanes and rebreathers).

Rebreathers do not meet Functional Safety (i.e. Clause 5.13.1 of the rebreather standard EN14143:2003) while anesthesia machines instead meet Functional Safety (and a host of other standards applicable to medical devices which are strictly enforced).

Put that in the context that rebreathers in addition are used underwater (more complex/harsher environment) and by a recreational diver (the "patient" is also the machine operator) and it is hardly surprising we have the fatality rates we have.

 

[peterbj7]

Rebreathers are extremely dangerous

I don't agree. Sure, you can kill yourself on a CCR with ease, just as you can kill yourself on OC or whilst driving. But used intelligently, such usage starting well before you get in the water, they can be at least as safe as OC. Certainly, if you don't AT ALL TIMES know the pO2 of the gas you're breathing you WILL die. Maybe not now, but eventually. And there are lots more things you can do that may kill you, such as not making sure the loop is physically secure (killed two friends of mine) or ignoring a mechanical malfunction (happened to me at 109 msw but I'm still here).

 

[shoredivr]

@gianaameri:

Can you provide links to substantiate what you are saying? Merely repeating a series of numbers and letters as fact doesn't support your statements.

 

[Tortuga68]

Rebreathers do not meet Functional Safety (i.e. Clause 5.13.1 of the rebreather standard EN14143:2003)

Maybe since you keep bringing that up, you could post a link?

 

[doctormike]

1- [Rebreathers] can be at least as safe as OC.

2- Certainly, if you don't AT ALL TIMES know the pO2 of the gas you're breathing you WILL die. Maybe not now, but eventually. And there are lots more things you can do that may kill you, such as not making sure the loop is physically secure (killed two friends of mine) or ignoring a mechanical malfunction (happened to me at 109 msw but I'm still here).

Hmmm... not sure that #2 supports #1 in this post..

Seriously, it's pretty clear that there is no experiment or study design that is going to accurately answer the question of CCR vs. OC safety for matched dive profiles, so we are stuck with abstracting information from incomplete reporting datasets.

It may not be statistically significant, but it's a little scary that in this small thread, one person had two friends die on CCR, another had at least 4 (?) (2 plus "several more"), and I myself had one (and was there for another potential one - the guy who passed out in 4 feet of water in the quarry). I don't know if any other posters here have more to add to the list, but for a recreational diver considering CCR from outside of the very well trained and experienced rebreather community, that just seems alarming.

I think that flots said it pretty well:

"An OC failure is obvious (you can't breathe) and can not be ignored, while a CCR failure can be completely silent and un-noticed as it puts you to sleep then kills you. This is a difference in failure modes that can't be dismissed."
​

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Maybe when the statistics are in, the extended gas advantage for entanglement and entrapment will outweigh the hazards of unrecognized hypoxia, hyperoxia and hypercarbia, but at this point, no one has really convinced me that CCR is "at least as safe" as OC, at least for recreational diving.​

 

[gianaameri]

Maybe since you keep bringing that up, you could post a link?

The rebreather standard and Clause 5.13.1 you can find here:

http://www.legrem.org/recycleurs/en14143_2003.pdf

Be aware that this is the current applicable standard, and that it will be replaced soon by a new standard (probably to be called EN14143:2013).

Because Clause 5.13.1 of the current standard could not be met by the rebreather industry (i.e. in respect of electronic rebreathers currently available to the general public), it was decided to remove such Clause altogether.

So, when you compare airplanes and anesthesia machines with rebreathers, now or in the future, you have to consider that the former meet strict Functional Safety requirements, while the latter don't.

Where a human is involved, you will always find human error (all divers make mistakes!!!), but the distinguishing element when comparing these different products is that airplanes and anesthesia machine meet strict Functional Safety requirements, while, for the aforementioned reasons in my prior post, the current rebreather generation does not (hence the commercial need to remove the unmet clause from the new rebreather standard soon to be adopted).

 

[Dsix36]

The rebreather standard and Clause 5.13.1 you can find here:

http://www.legrem.org/recycleurs/en14143_2003.pdf

Be aware that this is the current applicable standard, and that it will be replaced soon by a new standard (probably to be called EN14143:2013).

Because Clause 5.13.1 of the current standard could not be met by the rebreather industry (i.e. in respect of electronic rebreathers currently available to the general public), it was decided to remove such Clause altogether.

So, when you compare airplanes and anesthesia machines with rebreathers, now or in the future, you have to consider that the former meet strict Functional Safety requirements, while the latter don't.

Where a human is involved, you will always find human error (all divers make mistakes!!!), but the distinguishing element when comparing these different products is that airplanes and anesthesia machine meet strict Functional Safety requirements, while, for the aforementioned reasons in my prior post, the current rebreather generation does not (hence the commercial need to remove the unmet clause from the new rebreather standard soon to be adopted).

You always seem to get bogged down with the scematics of the written word and I have been reading this dribble on the other forums too.

Rebreathers do not kill people, people kill people!

Guns do not kill people, people kill people!

See the common denominator yet?

Regardless of how any standard is written, it will always be up to the people to keep their own arses alive. There will never be a perfect rebreather and no matter how much fuss you make about how the standards are written, you will always be able to find another loop hole to make a stink about.

I am not saying that your actions to attempt to get the manufacturers to improve upon safety is a bad thing, but CE standards still don't mean jack crap over here in the USA.

 

[shoredivr]

IEC 61508 Part 1 through 7 which is referenced in the link would be helpful also.

Thanks for the initial link.

 

[flots am]

It may not be statistically significant, but it's a little scary that in this small thread, one person had two friends die on CCR, another had at least 4 (?) (2 plus "several more"), and I myself had one (and was there for another potential one - the guy who passed out in 4 feet of water in the quarry). I don't know if any other posters here have more to add to the list, but for a recreational diver considering CCR from outside of the very well trained and experienced rebreather community, that just seems alarming.

I can add one more to the list. A guy I dive with is only alive because he happened to be near a really sharp OC diver who saw that he was going "lights out", grabbed him and did an air share.

flots.