Ccr Diver From Ohio Died In Ginnie Springs Today...

[JohnnyC]

It should be pointed out that no one has suggested that sanity breaths are going to resolve a CO2 hit..

You used the words sanity breaths, not me, so get salty with someone else.

Besides, sanity breaths do not exist. The idea that switching to open circuit will somehow restore mental capacity in the span of a few inhalation/exhalation cycles is not true. There are plenty of reasons to bail out, and many that will give you time to solve a problem and go back on the loop in one form or another. However, bailing out due to compromised mental acuity will do nothing in the span of several breaths to allow you to go back on the loop. If you bailed out because you recognized your mental state declining, you have a gas-compromised loop, and going back to a gas-compromised loop is a sure way to punch your ticket.

One of the theories that has been presented is that he had a CO2 hit and bailed. The fact that the symptoms of hypercapnia do not resolve themselves immediately, and the victim was still acting untoward, bolster the evidence that it is a possibility. It may not be at all, but it's a possibility. I am personally of the opinion that it was probably medical related, unless the timeline as presented has been miscommunicated. They had enough gas, especially with another team in the cave that turned the dive before they hit their turn pressure, so it seems that it was not an issue. If it was CO in his dil and his bailout, he wouldn't have lasted that long.

 

[The Chairman]

Ken, If this were actually true then why have there been multiple fatalities on eCCRs with 2 x current limited cells?

Laziness... you're supposed to do a check at 20 ft on pure O2 at the beginning of the dive. This was new protocol for me, but I think it's a great idea and only takes a few seconds.

Two people I knew personally have died on rebreathers because they dove with known flaws.

I can think of at least a half dozen over the years. That's way conservative too.

 

[The Chairman]

Besides, sanity breaths do not exist.

Sure they do... they don't work for CO2, but they have their place in sorting things out. Getting off the loop when you have a problem like hyperoxia or hypoxia (as well as hypercapnia) is the only sane thing to do. You might resolve those two but not hypercapnia... not even in scr mode.

 

[JohnnyC]

Sure they do... they don't work for CO2, but they have their place in sorting things out. Getting off the loop when you have a problem like hyperoxia or hypoxia (as well as hypercapnia) is the only sane thing to do. You might resolve those two but not hypercapnia... not even in scr mode.

Neither hypoxia nor hyperoxia are mind-altering states in the timeline of rebreather diving. They have warning symptoms just like anything else, but the level at which they cause mind-altering states is something entirely different and either quickly incapable of sustaining life, or oxtox. Switching to bailout from one of these conditions does not result in any corrected mental state, it does not "clear your head," which is the implication when someone uses the term "sanity breath." (Not to mention there's no real reason to bailout for hypoxia unless you legit can't squirt O2) Will it save your life? Abso-friggin-lutely. Will it turn you around from being in lalaland? Nope, because you're not there in those error conditions. You're either lucid, you're turning an awkward shade of blue, or you're biting through your tongue. Well, really you should have corrected either, things very rarely happen fast on a rebreather.

And really, with rebreathers these days, you'd really have to be off in wonderland to not notice either state. Even with mCCR's with very limited monitoring of PO2, it takes a bit to get there. You should have bailed long before your PO2 tanked since it takes a pretty long time at depth. 7 minutes I think it was in the article that Curt Bowen put together? Hyperoxia I can see happening fast since a stuck solenoid could spike PO2 fairly quickly, but at the same time, you notice things like that. The other potential is PO2 tanks on ascent, in which case you either catch it or you turn blue, and there's really not much time in between where you act funny.

Let's be frank about things, all rebreather fatalities (except medical) are due to user error, whether it's in assembly or operation. Complacency is what allows someone to dive with current limited cells. Complacency is what allows somebody to skip a checklist because they think they know better. Complacency is what allows someone to ignore their handsets and just assuming the electronics will take care of it. We've figured out how not to die on rebreathers, check your cells, change them regularly. Don't be cheap when it comes to sorb. Don't use gas that you can't ride all the way up unless you've got extra gas that you can. Carry more bailout that you think you need, and use the effing checklist EVERY.SINGLE.TIME.

I'm not advocating trying to stay on the loop. I'm not advocating that once you bail you've bailed for good. I'm just saying that nothing that alters your mental acuity is capable of being fixed and getting back on the loop (unless you've got one of those unicorn Cis-Lunar radials that's got the hydrophobic membrane...and you're carrying an extra one). If it's messed with your head, bailing out is for real and you ride the OC train as far as it will take you. Personally, my feeling is that unless there's an urgent pressing need to get back on the loop, you might as well stay OC the whole way back. You did plan your bailout with enough gas right?

I'm not trying to be confrontational, and we don't even need to agree, but we shouldn't hold on to disproven ideas. Diving is an evolution, and we're only going to get better, but it comes at the cost of tossing aside incorrect ways of thinking.

 

[The Chairman]

Neither hypoxia nor hyperoxia are mind-altering states in the timeline of rebreather diving. They have warning symptoms just like anything else,

Johnny, this is patently wrong.

From www.webmd.com Signs and symptoms of Hypoxia:

• Changes in the color of your skin, ranging from blue to cherry red
• Confusion
• Cough
• Fast heart rate
• Rapid breathing
• Shortness of breath
• Sweating
• Wheezing

Wikipedia gives these signs and symptoms:

• Cyanosis
• Headache
• Increased reaction time
• Impaired judgment time
• Euphoria
• Visual impairment
• Drowsiness
• Lightheaded or dizzy sensation
• Tingling in fingers and toes
• Numbness

Of course, when it comes to Hyperoxia we have all learned CONVENTID

• CONvulsions
• Visual
• Ears
• Nausea
• Twitching
• Irritability
• Disorientation and/or Dizziness

Both include mental disability: Confusion/Disorientation, Euphoria and Dizziness (Vertigo). All too often neither of these exhibit any symptoms except for the final ones. You can go from feeling fine to dead and never have a clue it's about to happen. That's why you HAVE to monitor your PPO2. You can't discount these or you end up dead.

 

[CuzzA]

It should be pointed out that no one has suggested that sanity breaths are going to resolve a CO2 hit.

In fact it was mentioned that a significant CO2 hit may well result in the diver blowing through all his bailout on the exit - with the result that divers who have experienced a CO2 hit tend to carry lots of bailout gas relative to divers who have not.



As noted by someone above, the technology has so far bene difficult to put in the moist environment of a rebreather.

The focus is however on prevention in terms of ensuring proper maintenance, properly packing the scrubber, and paying close attention to scrubber duration and factors that may shorten it, such as work load and water temperature. Colder temperatures significantly decrease scrubber efficiency, and thus duration.

Some companies also do scrubber tests under controlled conditions to determine scrubber duration under what are pretty conservative conditions, that then produce fairly conservative estimates that can be used for planning purposes.

----

The risks are different with CCR compared to OC and whether the total risk is greater or not probably depends on your diving, as well as on some personal traits of the diver.

CCR has some advantages over OC in terms of reducing decompression relative to OC, and knowing that gas isn't an issue, and that you have much more time to work a problem if needed is a big stress reliever.

A CCR diver can also drop stages with bailout gas that are never actually used on dives that would otherwise require those stages to be used (and replaced) on each and every dive, and if you're going to be diving in a system for awhile, pre-placing the bailout gas can greatly reduce the set up required for a series of dives, compared to OC stage diving and that reduction in set up dives, reduces some overall risk.

On the other hand, if you are not meticulous about maintenance, don't bother to fully understand how the unit works, don't fully understand the possible failure modes, don't conservatively plan for possible failures, and don't have the self discipline to turn a dive early, abort a dive, or call a dive on the surface at the last minute if the unit has a failure, then rebreather diving just isn't something you should be doing.

Two people I knew personally have died on rebreathers because they dove with known flaws. In that regard, their deaths were 100% preventable, yet they show as CCR deaths in the statistics. Do you blame the rebreather and conclude that CCR is just dangerous, or do you conclude that perhaps the potentially increased danger lies in how some people choose to dive the rebreather?

A related issue is that many divers are doing dives on CCR that they would never do on OC due to the logistics involved, so in one respect CCR may be more dangerous because it makes longer, deeper dives more practical, and thus more common. In other words, if more divers are doing longer, deeper dives that are more stressful and or carry greater risk in general, as those dives are more practical on CCR, then increased accident rates on CCR may be due in part to the greater risk overall on those dives, regardless of whether they were one on OC or CCR.

Good points and to answer your question, as I mentioned before, I don't blame the rebreather per se, it's just the nature of current rebreather design appears to come with a much higher risk of both operator error and failure of sensor data, thus increasing the risk of incident.

Again, I'm basing that completely from the Diver Mag. series of articles. I'm quite fascinated by CCR. I realize the amazing benefits in terms of both bottom time and the diving experience as a whole, it just troubles me to learn they (mfgs.) use O2 sensors (Richard Pyle's story is a little scary despite the use of 3 sensors) that aren't designed/calibrated for diving and there's no way to tell if you've had a co2 breakthrough.

Would I be wrong in stating if they (mfgs) solve those two issues it would prevent many CCR deaths? Perhaps putting CCR death statistics slightly closer to OC death statistics. I say slightly, because I believe the nature of CCR diving puts humans in an environment and physical state that will still be a higher risk of incident than recreational diving or even technical diving on OC.

Also, let me ask this question and I'll use an example.... IME, with packing my own DE resin cartridges for RO/DI water for reef tanks, despite my best efforts (literally fist pounding resin into the cartridge) I've had channelling occur allowing higher than intended TDS (Total Dissolved Solids) water breath through, however, I've found that rarely happens with factory prepackaged DE cartridges. Can the same be said about scrubber cartridges? Are there any known documented incidents/fatalities due to CO2 breakthrough on factory prepackaged scrubber cartridges?

In addition, sticking with my RO/DI analogy, we usually replace the DE resin once we get a TDS reading indicating the resin is spent. But in terms of diving, doing the same with soda lime could be fatal, so what is the exact procedure to calculate scrubber life? Assuming it's packed right, it would have to be based roughly on the number of exhales you made during use, right? Certainly no operators are counting their exhales, so are there any units out there that are calculating this? Perhaps just a simple pressure clicker that sense your exhale and has a running total? I suppose you could guesstimate based on your SAC rate, but it would just be a guess, unless you were actually tracking it through a computer. And even that seems like a challenge since unlike OC AI, you have a known pressure/cu.ft. starting point, where as on CC you really can't calculate that based on tank pressure or volume.

I'm also curious how is NASA measuring CO2 in their space suit rebreathers? Are they too just operating in the blind in terms of CO2? Or is the tech there, but too expensive for civilian rebreather use?

 

[JohnnyC]

You missed the important part where I pointed out "in the rebreather timeline." The 3 main insidious bailout scenarios are about the only thing on a rebreather that happens in an instant. You even pointed it out yourself in your last paragraph. Hell, my Meg head has it written on the inside, in two places no less.

I purposely went hypoxic on a table dive just to see what happens. I literally went from perfectly lucid to blacked out without any warning whatsoever. It was a purposely designed experiment and there was no warning whatsoever. And this was sitting on my couch where metabolic rate was the cause for PO2 drop. The most significant cause of hypoxia on a rebreather is low PO2 during an ascent. It happens so fast that there is no length of time for the symptoms to take place. That's why they say the most dangerous part of a rebreather dive is shallow. Of the couple people I've talked to who have gone hypoxic on actual dives, all of them echoed the same sentiment, they were there, then they weren't. Two were lucky in that they didn't lose the loop (gag straps ftw!!!) and one solenoid/one leaky valve pumped enough O2 into the loop to bring them back to consciousness. The other thought he was smart and decided that running 10/50 for dil all the time was a good idea. He passed out on ascent and started turning blue. He was positive enough that he broke the surface and the boat pulled him in and gave him O2 and resuscitated him. All 3 were complacent as hell, once.

As for hyperoxia, having an oxtox event can display some or all of those symptoms some of the time, but like a CO2 hit, a couple breaths from lower PO2 gas will not head it off, especially if you're right on the edge, and especially if you tox at a lower PO2. That's one of the reasons that the IANTD MOD1 standards for this year changed from dil flush to bailout (at least as explained to me). Not to mention, any mental symptoms are very closely mirrored by nitrogen narcosis too. Someone running air dil may not be able to differentiate the two, and neither is helped by going to bailout unless it's high helium and your actually making your END shallower by bailing out.

We do agree that you can go from hero to zero without warning, and we both agree that you HAVE to always monitor PO2. We can just agree to disagree about so-called "sanity breaths."

 

[The Chairman]

They have warning symptoms just like anything else,

I literally went from perfectly lucid to blacked out without any warning whatsoever.

You can say I missed the biggest point, but what you posted was misleading and patently false. Without the appropriate caveats, your two quoted statements are mutually exclusive and I want to make sure that everyone is clear about this. You are not guaranteed any warnings at all.

Divers, if you're so intellectually broke that you can't pay attention to your PPO2, you should stay away from rebreathers. A few minutes of inattention and bang, you're dead.

 

[muzikbiz22]

Some units do, and the opinions out there are varied as to their value, and whether they work & are dependable. My particular unit has one, and works just perfectly. There is a great article on CO2 sensors in the current Alert Diver mag from DAN.

Here is the article i was referring to in my earlier post, click here. CO2 Sensing in Rebreathers.

 

[Jack Hammer]

Thanks for bringing that up Kelly, maybe we'll get back on track