'Clinically dead' rebreather diver dragged from quarry - and then revived

[Diver0001]

I dive a rebreather - the main point I was trying to make (which I obviously did not make) - is that CCRs are often seen as more deadly than OC, yet there are often other factors contributing to the deaths.

I sincerely appreciate this point of view and I think you're right to point it out.

That said, OC does not have a failure mode that can cause the user to suddenly lose consciousness with little to no warning. I think the population of divers generally is aging and we're seeing more medical issues on OC as well but rebreathers have a couple of devilish hazards that, in my opinion, cannot easily be mitigated by anything other than an obsessive attention to detail.

.... and human beings are notoriously bad, in general, in obsessing about details over a long period of time. Eventually we all start to lose concentration, especially when things have gone as expected over many hundreds of iterations. We don't seem to have sufficient automation in rebreathers at the moment to ensure that the details are being "obsessed over" with machine like diligence. Perhaps that will come, but it will come with a body count.

Having said all that, if I dived trimix on a very regular basis I would probably buy a rebreather too, just because diving trimix on OC is a hassle and very expensive. This is the ONLY application for a rebreather that makes any sense to me at all.

R..

 

[aquacat8]

In my NSVHO, the fact that rebreathers seem to be more dangerous than open circuit is less about CCRs actually *being* more dangerous, and more about them *seeming* more dangerous.

The differences (again, my opinion) boil down to three general areas. I will acknowledge that one of these areas speaks to a difference that is actual rather than perceived, so I highlighted it first:
A. Frankly, CCRs are more complicated than OC and rebreather operators do have to pay more attention or they have the potential to screw up - and there is less room for error on a CCR than OC (mistakes can be deadly on CCR or OC, but there is more potential to make mistakes on a CCR).
Now, on to the other two "buckets" that are differences but that I feel contribute unfairly to CCRs being perceived as unsafe:
B. The average age of the CCR diver is likely decades older than the average age of the OC diver. *As a general rule,* with increased age comes decreased fitness. All other things being equal - for every 100 CCR dives and 100 OC dives, it's likely one would see a higher prevalence of medical issues on the CCR dives. Through no fault of the CCR!
C. A significant portion of people who buy CCRs do so bc they want to do deeper/longer dives - in other words, dives with more inherent risk to start with. (I know my then-buddy and I started diving rebreathers bc the amount of gas to support a three-day weekend at Eagles Nest/Diepolder was crazy - see the comparison below). The point is, in general, the nature of dives done on CCR is likely to be more complicated/risky - but that is the dive itself, not the fact that it's a CCR dive.

6 sets of 104s vs 2 CCRs, 2 sets of SM bailout
4 AL80s O2, 2 AL40s O2 vs 2 AL80s O2
4 AL80s 50%, 2 AL40s 50% vs 2 AL80s 50%
4 AL80s 32% vs -- 1 AL80 21/35
4 AL80s 18/45 vs 2 AL80s 18/45
4 AL80s 15/55 vs 2 AL80s 15/55
Or something like that....

Hope this makes sense. Been meaning to post something like this -but more well-written - for some time.

Holy Carp that a lotta gas!

 

[Frontpointer1000]

This is great news. Accolades to all those involved.


I found an online dive log for someone who was diving Dosthill this last January. Coldest temp was 5.5 degrees C. Other quarries in the region may get to around 10 degrees C by end of April, this temperature spread equals between 41 and 50°F. The cold temperature certainly has been a factor in Increasing one’s chances of return of spontaneous circulation after resuscitation. Another interesting fact is this Divers age of 71. It is impressive to do any form of resuscitation and have an individual respond well and by reading between the lines, I assume this patient had no negative hypoxic or anoxic brain injury. That’s pretty awesome. Especially in a 71-year-old.


A couple of points that I would want to illustrate for clarity‘s sake: The patient was reported as being blue, and this was thought to be because the patient had been hypoxic. Well that certainly may be the case, I would tend to think that it was more because of the temperature, but the article did say he pinked up after receiving rescue breaths. Maybe it was because of hypoxemia. And the other thing is most patients who drown typically do not have any significant amount of fluid in their lungs. And certainly it’s extremely difficult to appreciate fluid in the Lungs by physical auscultation.


There is no literature to support 20 to 25 rescue breaths as part of a resuscitation especially in a 90 second interval. The article says the patient was not breathing nor was his heart beating which would therefore indicate CPR-Meaning chest compressions and rescue breaths (and the instructor did state that he was performing CPR). I read this as the patient was getting Cardiac compressions as well.


The new literature for CPR indicates cardiac compressions prior to rescue breaths. However I would agree that clinically this patient needed oxygen in his cardio pulmonary system because he had been clinically depleted of any oxygen and obviously the results speak for themselves.


Again the article stated that the event occurred at or near the exit steps on the platform and I read this as being at a very shallow level. Being unfamiliar with rebreathers, I would reach out to those more informed than myself. Is there any process that occurs at shallow water at the end of the dive that someone should do with the rebreather that may not have been done? Or an easy to miss step?

 

[hroark2112]

If I'm ever found unresponsive on a dive...please revive my ass and know I'll never sue you for not having a current Red Cross card or for doing the compressions & rescue breaths out of order. Just bring me back to life and I'll be forever in your debt!!

 

[lv2dive]

Agreed, which is why I listed point A first.

...That said, OC does not have a failure mode that can cause the user to suddenly lose consciousness with little to no warning...

but rebreathers have a couple of devilish hazards that, in my opinion, cannot easily be mitigated by anything other than an obsessive attention to detail.

.... and human beings are notoriously bad, in general, in obsessing about details over a long period of time. Eventually we all start to lose concentration, especially when things have gone as expected over many hundreds of iterations. We don't seem to have sufficient automation in rebreathers at the moment to ensure that the details are being "obsessed over" with machine like diligence. Perhaps that will come, but it will come with a body count...

 

[lv2dive]

Yes it was! Hence the beginning of the path to the rebreathers

Holy Carp that a lotta gas!

 

[Jack Hammer]

I hate to rain on the scary new rebreather concept parade... rebreathers have been around longer than our current demand fed open circuit regulators. The original concepts are known to date to the 1600's with working models 200 years ago. Space suits, space stations, the guys who went to the moon, submarines, etc use the same type of technology. It's been done for well over 100 years. Where they become "dangerous" is when not respected, maintained, or when abused.

 

[lv2dive]

Yes, as one ascends on a rebreather, all things being equal, the partial pressure of oxygen in a gas mix will go down - there will be less oxygen in the breathing mix. This is combated by adding oxygen as one ascends. If, however, a diver had been deep enough and did not add oxygen on the ascent, it is theoretically possible that the gas mix in the loop could become hypoxic.

...
Again the article stated that the event occurred at or near the exit steps on the platform and I read this as being at a very shallow level. Being unfamiliar with rebreathers, I would reach out to those more informed than myself. Is there any process that occurs at shallow water at the end of the dive that someone should do with the rebreather that may not have been done? Or an easy to miss step?

 

[Frontpointer1000]

Yes, as one ascends on a rebreather, all things being equal, the partial pressure of oxygen in a gas mix will go down - there will be less oxygen in the breathing mix.

I think that quarry’s max depth is 20 m. That seems pretty shallow to have a miss adventure as you described above. Would that be accurate?

 

[lv2dive]

It depends on how low they let their PPO2 get to at depth.

I think that quarry’s max depth is 20 m. That seems pretty shallow to have a miss adventure as you described above. Would that be accurate?