Diver dead on the Andrea Doria

[boulderjohn]

I am writing this from the standpoint of someone who believes the future of deep diving really is the rebreather, but who is afraid to use one. On my last deep dive, I was helped to standing, labored my way to the back of the boat with more than 200 pounds of tanks and gas, jumped into a heavy current, and thought, "A rebreather really would be nice right now." So why don't I use one?

This may be true, but (Risk level on dives taken by CCR divers) >> (Risk level on dives by OC divers).

The annual DAN fatality report a couple of years ago included two rebreather divers who died while testing their rigs in swimming pools.

The problem I see there is that CCR failures can lead to loss of consciousness without warning, a failure from which it is hard to recover at any depth.

CCR's are the future of tech diving, however we have to start addressing the unacceptable deaths.

I agree, and it is the unacceptable deaths that scare the beejeezus out of me.

I fear that CCR design has not caught up what appears to be the rather low level of technical acumen of much of the recreational diving community, not many of whom seem to be willing or able to dedicate the time and energy required to become a good rebreather technician as well as a competent rebreather pilot.

So who is it that is working on rebreather design?

I actually know some. I know where some rebreather design now being used originated, and I know some people working on technical changes to them. In the cases I know, I would describe the work as being done by people whose true expertise lies elsewhere and who are doing this work in their spare time on a very limited budget. I know nothing about other rebreather designs, so I can only speak for that small minority. I would like to know that somewhere, somehow, some company is dedicating real experts and real funding to R & D.

 

[AfterDark]

The problem I see there is that CCR failures can lead to loss of consciousness without warning, a failure from which it is hard to recover at any depth.

This is the root of the CCR issue IMO and why until it's addressed I'll never dive with one. Seems to me it's safer to hold your breath for a spell if you want to enjoy a little silence.

 

[Jax]

I've considered rebreathers a bit, and read a bit about them. From an engineering standpoint, I see them as intricate pieces of machinery with very good redundancy, but designed to the level that the user must be extraordinarily disciplined, focused, and must not make a mistake. Even the eCCRs must be constantly watched.

There is nothing wrong with that machine-man interface as long as the users are carefully selected, trained, and held to standards. Consider the Blue Angels or Thunderbird precision flight teams. They are performing standard flight maneuvers to extraordinarily close tolerances where the slightest mistake can kill them.

I love the saying "This machine is constantly trying to kill you." It's a good way to put the danger in the forefront of one's mind.

The problem with all this is that sometimes, the user cannot put on and maintain that excruciatingly precise attention to detail the entire time they are on the machine. A moment's lack of focus may be that moment the PPO₂ goes too high. There is NO recovery from that mistake.

Lastly, should one have a medical issue while diving a CCR, it seems to this never-dived-with-anyone-diving-one newb that it would be much harder to recognize issues in a partner who is possibly having a stroke or heart attack, due to the hoses and such removing any facial feedback except for the eyes.

Then, if one spits out the loop, flooding it . . . Recovering from a medical issue underwater just seems too complicated.

 

[Rhone Man]

I think I'm on pretty safe ground to suspect that the (number of CCR fatalities)/(number of CCR dives) > (number of Open Circuit fatalities)/(number of Open Circuit dives).

I remember reading a reasonably well put together article which suggested that the formulae:

(number of CCR fatalities)/(number of CCR dives) = 800 * (number of Open Circuit fatalities)/(number of Open Circuit dives)​

was accurate. Could probably find it again with judicious Google searching.

 

[Thalassamania]

I'd love to have that reference, if it would not be too much trouble.

 

[ScubaSteve]

Take it for what it is worth.....

From: Rebreather - Wikipedia, the free encyclopedia

The percentage of deaths that involve the use of a rebreather among United States and Canadian residents increased from approximately 1 to 5% of the total diving fatalities collected by the Divers Alert Network from 1998 through 2004.

 

[Jax]

Take it for what it is worth.....

From: Rebreather - Wikipedia, the free encyclopedia

The percentage of deaths that involve the use of a rebreather among United States and Canadian residents increased from approximately 1 to 5% of the total diving fatalities collected by the Divers Alert Network from 1998 through 2004.

As you say, FWIW . . .

If the number of rebreather divers increased by at least 5% during that same period, one would say the fatality rate stayed the same. If the number of rebreather divers increased any MORE than 5%, then their fatality rate actually decreased.

 

[gsk3]

As you say, FWIW . . .

If the number of rebreather divers increased by at least 5% during that same period, one would say the fatality rate stayed the same. If the number of rebreather divers increased any MORE than 5%, then their fatality rate actually decreased.

You mean 400% increase (a 5-fold increase), and the measurement should be relative to the increase in open water divers.

Even then, it's best done as a rate (per unit of time dove or per dive), and you would have to control for the depth/complexity of dives.

 

[jkaterenchuk]

I've considered rebreathers a bit, and read a bit about them. From an engineering standpoint, I see them as intricate pieces of machinery with very good redundancy, but designed to the level that the user must be extraordinarily disciplined, focused, and must not make a mistake. Even the eCCRs must be constantly watched.

There is nothing wrong with that machine-man interface as long as the users are carefully selected, trained, and held to standards. Consider the Blue Angels or Thunderbird precision flight teams. They are performing standard flight maneuvers to extraordinarily close tolerances where the slightest mistake can kill them.

I love the saying "This machine is constantly trying to kill you." It's a good way to put the danger in the forefront of one's mind.

The problem with all this is that sometimes, the user cannot put on and maintain that excruciatingly precise attention to detail the entire time they are on the machine. A moment's lack of focus may be that moment the PPO₂ goes too high. There is NO recovery from that mistake.

Lastly, should one have a medical issue while diving a CCR, it seems to this never-dived-with-anyone-diving-one newb that it would be much harder to recognize issues in a partner who is possibly having a stroke or heart attack, due to the hoses and such removing any facial feedback except for the eyes.

Then, if one spits out the loop, flooding it . . . Recovering from a medical issue underwater just seems too complicated.

Reading and diving them is somewhat different. You seem to point out some issues of which you are not familiar with except from a 3rd party perspective.

In fact at least one of your commenst is inaccurate. "A moment's lack of focus may be that moment the PPo2 goes too high. There is NO recovery from that mistake." You make it sound like if you take your eyes off the PO2 readout for a millisecond you might die. That is complete nonsense. If the PO2 goes too high then there is a reason. The CCR diver would hear the solenoid firing and Oxygen injecting into the loop constantly and they would notice that they would become very buoyant all of a sudden or they would notice the loop volume become difficult to breath. Any one or all three of these results would be noticeable by the CCR diver. If in fact it did happen the CCR diver could simply shut the Oxygen valve, vent the loop and do a DIL(diluent gas) flush. They should be able to do that within a few seconds. It is a core skill of the course and practised many times just like a malfunctioning LP inflator on a BCD is practised in a OW diver course. The DIL would bring the PO2 down immediately. Any trained technical diver knows a high PO2 is unlikely to kill you in a short period of time.

I hope that provides some real clarity and correct information to your post.

 

[Jax]

True . . . my point was from MY perspective -- and that "moment" of inattention could be longer, of course. As you say, an experienced CCR diver would notice all those things.

*I* simply am incompatible with the amount of attention such a machine requires. I'm afraid the period to get to the point of experience would be quite dangerous for me. Lastly, as a computer engineer, I don't have the faith in the electronics. Just me.