Pompano Beach Fatality Sunday April 16th

[doctormike]

No one on this thread has posted this, including the poster you quoted.

You are correct. In retrospect, my phrase "That CCR is SO inherently dangerous that it should never be used by anyone" was putting words into the OPs mouth, and I can't assume that. Point well taken.

I stand by the rest of the post, though.

 

[Joneill]

Your logic makes perfect sense. Rebreathers are inherently more complex and risky, there's a disproportionate amount of accidents and fatalities with rebreathers, therefore if there is a fatality and the diver was using a rebreather it's common sense to make the connection between the two.

Actually, common sense would dictate that one should not speculate about “connections” when there is not any meaningful information that supports a connection. It’s senseless and also disrespectful to the deceased diver to do so at this point.

 

[aue-mike]

If the earlier mention that he experienced an LOC during or shortly after descent is accurate then that is consistent with hypoxia due the loop PO2 not being maintained.

Mark-
You are a rebreather diver. Please think about your statement above and why your scenario is fundamentally problematic.
Mike

 

[Kay Dee]

Mark-
You are a rebreather diver. Please think about your statement above and why your scenario is fundamentally problematic.
Mike

I wondered when someone would point this out.

RIP Joe.

 

[doctormike]

Mark-
You are a rebreather diver. Please think about your statement above and why your scenario is fundamentally problematic.
Mike

You mean because PPO2 rises with descent? True, but if there is a problem with O2 (feed or supply), eventually you'll metabolize the O2 in the loop down to hypoxic levels, right? Especially with a lean dil.

I'm assuming that this diver would have picked that up, but at this point with very little known, no reason to rule that out. Especially from the point of view of discussing hypotheticals...

 

[aue-mike]

You mean because PPO2 rises with descent? True, but if there is a problem with O2 (feed or supply), eventually you'll metabolize the O2 in the loop down to hypoxic levels, right? Especially with a lean dil.

I'm assuming that this diver would have picked that up, but at this point with very little known, no reason to rule that out. Especially from the point of view of discussing hypotheticals...

Yes, your PO2 rises on descent...and because pressure on descent is increasing, gas volume in your loop decreases, necessitating the addition of diluent to compensate. Therefore, even with a lean dil, the possibility of going hypoxic on descent is unlikely because you are constantly adding gas with more O2 even if it's a "lean dil" and even with O2 supply off (which is unlikely given additional info below).
I will add that I know the individual in question, having dived with him regularly for 20 years, 15 years of which was on CCR. And it was standard practice for us to only add O2 while on the surface preparing to dive. This was a standard practice as it was used as a backup check that our O2 was on while pre-breathing and checking cell integrity, etc. Therefore, the loop PO2 on the surface upon splashing in would typically have been around 0.60-0.80. Using 10/50 trimix as diluent would also be typical. While considered a "lean dil", I am sure folks can work out the math to determine the shallow depth straight 10/50 would support life for an extended period of time.
I will also add that the incident occurred in the water column, at around 160 fsw and before reaching the wreck, and at around 2 minutes into the dive.
While not ruling out hypoxia, I wouldn't be looking at it as a primary, secondary, or even tertiary scenario given the above.

 

[Vicko]

Plenty of people took a breath of hypoxic dill and died before their body hit the bottom, cutting the o2 is not the only way of passing out.

 

[doctormike]

Yes, your PO2 rises on descent...and because pressure on descent is increasing, gas volume in your loop decreases, necessitating the addition of diluent to compensate. Therefore, even with a lean dil, the possibility of going hypoxic on descent is unlikely because you are constantly adding gas with more O2 even if it's a "lean dil" and even with O2 supply off (which is unlikely given additional info below).
I will add that I know the individual in question, having dived with him regularly for 20 years, 15 years of which was on CCR. And it was standard practice for us to only add O2 while on the surface preparing to dive. This was a standard practice as it was used as a backup check that our O2 was on while pre-breathing and checking cell integrity, etc. Therefore, the loop PO2 on the surface upon splashing in would typically have been around 0.60-0.80. Using 10/50 trimix as diluent would also be typical. While considered a "lean dil", I am sure folks can work out the math to determine the shallow depth straight 10/50 would support life for an extended period of time.
I will also add that the incident occurred in the water column, at around 160 fsw and before reaching the wreck, and at around 2 minutes into the dive.
While not ruling out hypoxia, I wouldn't be looking at it as a primary, secondary, or even tertiary scenario given the above.

Right, but the point of my post is that many people reading accident analysis threads are trying to learn about failure modes and avoiding the next accident. It's not a legal deposition trying to determine precisely what happened in this particular case to this particular diver.

You have added specifics which I didn't know before. Furthermore, I didn't know Joe, but simply stating that LOC on CCR raises the question of hypoxia isn't meant to be a slight against his skils or reputation. I hope you don't take it that way.

Maybe I read too much into the last two posts. But I do think that implying that hypoxia is not something to be considered isn't helpful.

 

[aue-mike]

Right, but the point of my post is that many people reading accident analysis threads are trying to learn about failure modes and avoiding the next accident. It's not a legal deposition trying to determine precisely what happened in this particular case to this particular diver.

You have added specifics which I didn't know before. Furthermore, I didn't know Joe, but simply stating that LOC on CCR raises the question of hypoxia isn't meant to be a slight against his skils or reputation. I hope you don't take it that way.

Maybe I read too much into the last two posts. But I do think that implying that hypoxia is not something to be considered isn't helpful.

I have not taken anything you posted in here as a slight against Joe. And I did not state nor imply hypoxia is not something to be considered. I considered hypoxia, but based on the information I posted (and additional information not for public dissemination) and my lengthy personal experience with Joe, considered it to be unlikely over other scenarios.
Over the past 3+ years, Joe had focused on diver education. Over that time he instructed numerous technical divers, be it for cave diving classes, CCR classes, etc. I know Joe would want to know what happened, and would want to educate other divers on the accident circumstances for their benefit. Which is why I opted to now wade into this to try to provide some useful context and information.
The universe of potential CCR failure modes and diving accident/incident causes is well documented. If one wants to simply consider/conclude the cause of death was due to either: 1) hypoxia; 2) hyperoxia; 3) hypercapnia; 4) medical issue; 5) gear issue; 6) human error; 7) some combination of the above; 8) etc., -- especially before any detailed gear analysis or coroner report (which 99/100 are unhelpful) has been conducted or released -- then we don't need to have this forum as it will always be covered by something within this spectrum. And per your statement: "It's not a legal deposition trying to determine precisely what happened in this particular case to this particular diver." If we are not trying to determine the particulars of the incident, just what is the point of this forum?

The best way to learn about failure modes and how to avoid the next accident is to take quality diver training and surround yourself with solid, like-minded, safety-conscious divers. It's that simple.

 

[mderrick]

Mark-
You are a rebreather diver. Please think about your statement above and why your scenario is fundamentally problematic.
Mike

Mike,
I believe you are thinking that as the diver descends on CCR, the loop PO2 will normally increase and can even spike high during a rapid descent typical of technical dives. However, my statement is not at all "problematic". I've investigated several accidents and personally observed one where LOC occurred during or shortly after descent. While descent does cause a relative increase in the PPO2, at the same time the diver is burning oxygen out of the loop if oxygen is not being replaced by the rebreather.

Here is a specific example, one of many possible: The CCR diver has properly prepped their unit including a pre-rebreathe during the transit to the dive site. During the transit, the oxygen valve is 'rolled off' as the rebreather bounces against a tank rack and bench designed for AL-80's. The loop PO2 is stable at the expected set point, say 0.7 ATA from the pre-breathe and indicated pressure on the SPG is as expected as well (from the charged hoses, which may be quite long on some units and hold a surprising amount of oxygen).

Once the dive boat reaches the site the diver dons the CCR, runs an abbreviated pre-jump list, then enters the water and makes a very rapid descent. In our area, this is a typical occurrence especially if the diver is "smart bombing" the wreck. While the loop PO2 is initially increasing, and the solenoid initially injects some oxygen (from the hose residual), eventually the loop PO2 will begin to drop and will more rapidly drop if the diver pauses their descent for any reason. The first diver jumping on a technical wreck dive in our area often has the task of chaining in a descent/ascent line for others to follow. That diver is exceptionally task loaded with navigating to the wreck and tying in. If the task loaded diver fails to notice their setpoint is not being maintained (the usual concern being a brief hyperoxic spike, not hypoxia), then LOC follows.

Note, this isn't a hypothetical example, it's has happened to me personally exactly as I described and I was lucky enough to notice dropping PO2 before it became dangerously low. I've caught two more roll offs over the years, but before gearing up as I now always manually check the valve immediately before gearing up. I've also personally observed several CCR divers actually perform their pre-breathe and then close the valve as a result of a deeply ingrained OC habit. Just to be clear, I'm not proposing the circumstance I've just described above as what happened in the case of the accident being discussed. I'm simply describing my findings in more than one case where LOC on CCR happened during or very shortly after rapid descent. If setpoint is not being maintained, a rapid descent quickly after entry will delay LOC rather than occurring at or near the surface.