Two divers critical - Hawaii

[doctormike]

Wow, thanks so much for posting that.

That's really wonderful of her to do that writeup, it shows how much respect she has for the rebreather community, and she seems to understand that her husband would have wanted people to learn from what happened to him.

Attached is the accident report, in case you have any trouble getting it from Facebook.

 

[devildog12210]

I came to make sure this post was updated with the info from FB. That first picture of his newborn daughter was certainly moving. Task loading is a real thing and not just a phrase from a text book or instructor. I wish reporting of this nature was more common.

 

[doctormike]

We were discussing this in another thread, but this accident also demonstrates the value of the "preflight" checklist. This is often confused with other checklists that involve building the unit, positive and negative tests, etc... When I posted my checklist sticker on Facebook, lots of people didn't get that difference, but it's an important one.

The preflight checklist is properly done after you have donned the unit. Doing it and then putting the unit on makes it possible for things to change - valves can roll off, LP feeds can become disconnected, etc...

It's not a long checklist, but distracted by the camera or not, doing it would have caught the O2 being off and the unit not holding a 0.7 setpoint during the pre-breathe. Some people question the utility of the pre-breathe because it might not catch CO2 breakthrough, but that's not all it is for. It's nice to watch your unit hold that setpoint for five minutes before you splash. If you are going to pass out from hypoxia, it's better to do that on the deck of the dive boat than in the water.

 

[Compressor]

Very sad and tragic. Condolences to family and friends of the diver.

 

[Compressor]

Someday RBs will have inductive pickups to measure the divers O2 and CO2 blood levels in real time. IMO until then these tragedies will continue to happen. Any device that can put a diver asleep while diving is a device that requires a lot of attention.

Let's hope so AfterDark.

Right now in the field of anesthesiology, one can measure tissue oxygen levels but its invasive (skin is violated). Indirect methods are commonly used. In anesthesia cicuit while you the patient is asleep, carbon dioxide is measured on every breath. These usually correlated with blood levels (they are not exact nor do they have to be). Insurance liability costs have decrease significantly because of intense monitoring by the silent heros of the operating room: anesthesiologists.

 

[doctormike]

Someday RBs will have inductive pickups to measure the divers O2 and CO2 blood levels in real time. IMO until then these tragedies will continue to happen.

His RB (and all modern CCRs) have multiple devices that reliably measure loop PO2 in real time. Reading that report, all four sensors showed severe hypoxia, presumably ringing the visual and tactile alarms. This tragedy was not because rebreather technology is not sufficiently advanced. It was because a distracted diver was allowed to splash alone on a training dive, hadn't turned on his O2, became hypoxic, lost the loop and drowned. Not sure how future technology could fix that problem.

 

[Jeremy Williams]

His RB (and all modern CCRs) have multiple devices that reliably measure loop PO2 in real time. Reading that report, all four sensors showed severe hypoxia, presumably ringing the visual and tactile alarms. This tragedy was not because rebreather technology is not sufficiently advanced. It was because a distracted diver was allowed to splash alone on a training dive, hadn't turned on his O2, became hypoxic, lost the loop and drowned. Not sure how future technology could fix that problem.

I’m not sure that was the case. Perhaps a Liberty diver can clarify, but the report indicates that the unit was in “surface” mode. This caused sensor levels not to be recorded. I infer that perhaps there were not alarms occurring at that point either. The report makes no mention of alarms until the unit hits a depth activation at which point the damage has already been done.

 

[doctormike]

I’m not sure that was the case. Perhaps a Liberty diver can clarify, but the report indicates that the unit was in “surface” mode. This caused sensor levels not to be recorded. I infer that perhaps there were not alarms occurring at that point either. The report makes no mention of alarms until the unit hits a depth activation at which point the damage has already been done.

Interesting point. @Superlyte27 is, I believe, a Liberty instructor, maybe he can clarify. But even in surface mode I’m assuming that the PO2 readings would be visible to the diver. And I still don’t see how more advanced direct monitoring of systemic PO2 would have fixed this problem.

 

[KenGordon]

I’m not sure that was the case. Perhaps a Liberty diver can clarify, but the report indicates that the unit was in “surface” mode. This caused sensor levels not to be recorded. I infer that perhaps there were not alarms occurring at that point either. The report makes no mention of alarms until the unit hits a depth activation at which point the damage has already been done.

The point being made is that no amount of technical help can fix an ignored hypoxic loop. Jump in with the O2 off and there is nothing that can be done by the machine.

Personally, I at least press all the buttons that let in gas before I stand up. The most important is the o2 manual add. However, the core mistake is the same one made by lots of OC divers and to be expected. The mitigation is paying attention so I’d say the camera killed him.

 

[Jeremy Williams]

Interesting point. @Superlyte27 is, I believe, a Liberty instructor, maybe he can clarify. But even in surface mode I’m assuming that the PO2 readings would be visible to the diver. And I still don’t see how more advanced direct monitoring of systemic PO2 would have fixed this problem.

The blame game is a loose-loose exercise. It’s clear that the diver made a grave mistake. Probably more than one. But I also think the Divesoft guys reading their own report are thinking...

1. Need to keep the 10 (15?) minutes of o2 sensor data immediately before descent begins

2. Alarms for hypoxia need to occur in surface mode if they aren’t already and they need to be logged

There are systematic improvements that can be learned here.