Rebreather Diver dies in Pool in Oregon

[wedivebc]

My question to all you rebreather experts out there is why, if this was envisioned for the future by one of the big names in diving, hasn't this occurred? Why do you continue to accept gear which doesn't have these characteristics, when this is possible and was envisioned in 1970?

John

When I was a kid in the 60s we thought we would be visiting mars on a regular basis by the 1990s. This idea was supported by many "experts" in the field of space travel. Unfortunately no crystal ball is infallable. We are continually attempting to improve the safety of all forms of diving. Unfortunately us laymen are not privey to the finding of coroners and accident investigators and the conclusions reached by these "experts" are not seen as the best ones by those of us who use the equipment regularly.

 

[caveseeker7]

The envisioned closed circuit scuba by Bev Morgan is an engineering control. That very specialized scuba (closed circuit with life-saving abilities to breath and signal) would probably have prevented this kind of fatality, as the gear would have sensed the lack of oxygen (if that was the problem), and added it automatically. ...

My question to all you rebreather experts out there is why, if this was envisioned for the future by one of the big names in diving, hasn't this occurred? Why do you continue to accept gear which doesn't have these characteristics, when this is possible and was envisioned in 1970?

You mean like three sensors in every electronically controlled rebreather being read by a computer to measure the pO2 in the inhalation side of loop, and maintain that pO2 by injecting O2 through a solenoid valve to replenish the metabolized O2?

Not only has it occured, it had occured when Bev Morgan visualized it. It's something that has been done since Biomarine's CCR1000 in 1969. In 1970 that vision was in the rearview mirror.

Since then, warning lights constantly within the peripheral vision of the diver have been added, audible alarms and vibrating alarms. At least one military rebreather also measures and warns of CO2, auto flushes the loop and even has been equiped with the means to return an unconcious diver to the surface.

But the unit in this case was not electronically controlled, it was not a CCR, and the monitor and alarm for the pO2 were turned off.

Last but not least, even Bev Morgan couldn't envision getting gas out of an empty tank. If there isn't any supply to add, even the best engineered machine won't be able to do so automatically.

 

[JonnyB]

Last but not least, even Bev Morgan couldn't envision getting gas out of an empty tank. If there isn't any supply to add, even the best engineered machine won't be able to do so automatically.

Yet...
"Soon" the day will be there, we will get O2 form H2O and we will have gills, i have seen it, I saw the move waterworld and Kevin Costner had it, so it must be true. They dont lie on TV :06:

/Jonny

 

[O2BBubbleFree]

The apparatus will supply intake and exhaust breathing gasses at over and under pressures. If the diver passes out, the apparatus will automatically take over the breathing cycle and signal for assistance.

I'm all for electronically-controlled CCRs (for those that want them) with multiple O2 sensors and CO2 monitoring, but I think taking over the breathing cycle is way over the top.

Besides, how would this dream machine maintain an open airway? Is it going to have a pneudraulic device to tilt your head back? Are you going to trust it?

In the technology R&D world, it’s common to hear, “there’s only so much you can do to protect the user from himself.” It’s pointless to discuss technology shortcomings using an example where the diver made at least two critical mistakes:

1. Violation of the ‘cardinal rule’ of RB diving, “always know your PO2." As mentioned, the diver had a perfectly good monitor, that was shut off.

2. Never dive a RB solo. Chances are a proper buddy, who was monitoring the diver, would have detected the problem and intervened.

 

[caveseeker7]

The whole point of manual, mechanical rebreathers is to work without electronics and the problems that came with their use in marine environment. An OC regulator doesn't breath for you either. Nor do they supply gas from empty tanks.

The Aquapilot was introduced a few years back. An automatic bouyancy control system preventing fast ascent, maintaining target depths, preventing plunging past MOD, by using electro pneumatic valves. All integrated into a gas integrated deco computer (yep, it does the stops for you, too) and usable with most any BCD. According to a dive mag test it actually works, too. From what I gather it wasn't very successful ... . Just because it's possible doesn't mean people will embrace it.

Another company suggests implanting microchips that can log dive profiles, c-card info,
integration with a device like the Aquapilot to prevent diving past training limits, even medical history for emergencies and banking info for dive shops ... .
Not for me, that much I tell ya.

Yet...
"Soon" the day will be there, we will get O2 form H2O ...

You may be laughing, Johnny, but some Israeli outfit has been fiddling with that.
Somewhere there ought to be a thread or two about an article describing it.

The problem is that the amount of O2 in H2O is small and that unit needs to use up a lot of water volume to generate the amount of O2 needed by the diver ... if memory serves me right the water is sucked in one end, depleted of O2 and H2 expelled on the other. Due to said high volume, there were plenty of 'rpcket man' and 'human torpedo' jokes in that thread, and one of the Aussies did the math for immense volume.

The other problem there, as well as with forced ventilation, is the needed power supply. There are limits in size, weight and of course price. Who wants a 50 - 70 lbs rebreather and haul a 50 lbs battery around?

Also, complexity and additional failure points would be added.

Last but not least, it reminds me of one of my favorite post, by 'bubbleboy':
I reckon if I bolt enough sh!t to my Inspiration I end up with a Newtsuit.

By the way, Nuytten's Exosuit is a 1 ata hardsuit with a 48 hr O2 rebreather, good for 100 or 200 meters without any deco. Tried the arm at DEMA last year, range of motion is amazing. Prelim price estimate for the 100 m version was $100 K.

 

[JonnyB]

You may be laughing, Johnny, but some Israeli outfit has been fiddling with that.

I know, that is why i said it, i remember reading about it, i think i have the link somewhere as well...

/Jonny

 

[padiscubapro]

I have been contacted by several people to comment on this thread so here goes...

Rebreathers are just tools, but each RB design does have specific failure modes. In the hands of an untrained or poorly trained diver they are more risky than OC, but in the hands of an experienced RB diver, they allow more freedom and options than OC.

I do many dives that I would never dream about doing on OC because of the required gas volumes.

Skipping predive checks is a recipe for disaster. The one thing that all RB divers should be aware of and treat as the Bible, is that just because you can comfortably breathe on the loop doesn't mean the loop is breathable (life sustaining).

ALWAYS, ALWAYS KNOW YOUR PO2!

The types of rebreathers in use today are that of SCR and CCR.

The SCR rebreathers fall into two main categories, CMF and RMV-keyed. CMF rebreathers are simple designs, and are relatively safe when the proper mixes are used. The RBs are designed in a way that if you use the proper mixes, in theory, PO2 monitoring is not needed. This is true as long as the system is operating correctly and the proper mix is selected, but the orifices do get clogged and people do screw up setting the flow rate and mix selection. It is my opinon that a PO2 monitor should always be used, This feeling is
so strong with my primary agency (ANDI) that our certifications specifically require PO2 monitoring, and it's required during training.

CMF units have the most risk when they are used on the surface, but as you descend, the risk decreases until you start approaching the design limits of the unit, or MOD of the gas you are using. CMF units vent gas when the breathing loop + divers lungs is more than the loop can hold, and
if no new gas is added, the loop won't vent and the mixture will go hypoxic.

RMV keyed units are a more efficient SCR, they vent gas on every breath, so loss of gas addition becomes evident after just a few breaths. This should be well ahead of the loop going hypoxic (assuming the proper gas is chosen). These units maintain a fairly stable fo2, but if the one way valve between the two chambers fails, no gas will be vented and the loop will go hypoxic.

CCR rebreathers come in 2 basic flavors, electronic and manual.. Each has its own advantages and disadvantages. The general operation is the same in that no gas is vented on breathing, loop
volume decreases as oxygen is metabolized. Depending on how full the loop is to start with, the loop may or may not become difficult to breathe before becoming hypoxic. Electronic units typically have some kind of alarm mechanism to warn the diver when the loop is becoming dangerous; i.e. either too low on O2 or too high. Mechanical/manual units depend solely on the skill and observations of the diver.

Hypoxia (low ppO2) is less likely on a CCR unit because of the usual multiple oxygen sensors and alarm mechanisms present. Hyperoxia (high ppO2) is more likely, in that as oxygen sensors fail,the PO2 many be considerably higher than indicated. The biggest risk of an ECCR is not turning on the oxgen or electronics.Gas selection with SCR's is absolutely critical, as is calibrating the flow rate.

This death makes the second SCR death in a pool this year. During shallow water training or testing the hottest mixes available should be utilized. Ideally in a pool, 100% oxygen is the best choice since few pools have depths that can cause problems with oxygen. Pools used for competitive diving (platform, springboard ect), are deeper than oxygen could be used but 80% would be an ideal choice in that case.

My gut feeling is that the diver did not do a predive check, and had the flow rate too low for the mix that was present, causing the loop to go hypoxic, leading to unconsciousness, and then death. It is a gentle way to die. It just sneaks up on you!

 

[John C. Ratliff]

PADISCUBAPRO,

Thanks for this post. It is most informative.

I had a duel purpose in bringing up the topic of the state of the art. One was to divert us away from what I felt was not a good topic for this situation, the intellegence of the diver involved. To me it is simply another way of saying, "It can't happen to me."

The other was to learn more about the state of the art of rebreathers. As I said, I've been diving a long time, but am not a rebreather diver. I can see the advantages, but also see the disadvantages for me. I'm an underwater photographer, and they would be a real advantage for this, but I also do a lot of solo diving. This thread has convinced me that solo on a rebreather is not a good idea.

Again, thanks for the input.

SeaRat

 

[jepuskar]

When it comes to rebreather information, he is the person to go to.

 

[ShoalDiverSA]

I have been contacted by several people to comment on this thread so here goes...
...

A very interesting and informative post - thanks! It puts the differences in technology and design into perspective nicely.

Cheers,

Andrew