Lake Attersee fatality - Austria

[DandyDon]

I mean they will, as my instructor tactfully framed it:" if your dead anyway you may as well die on the surface where a body recovery is cheaper"

This thought has nothing to do with this incident, but in a lesser risk skipping less deco than described here or ascending faster than desired - it beats drowning. A bent or embolized diver can be treated after surface recovery still alive if the facilities are available. A diver who drowns at depth, not so much.

I remember another accident discussed here years ago in which two divers had incurred significant deco, one had a severe complication on ascent and essentially died there, and the other blew off a long deco obligation to get his buddy to the surface. The dead diver could not be revived, but the Coast Guard took the survivor to a hospital with a chamber. They checked him, then watched him for a couple of hours, but to his surprise, he didn't have to do a chamber ride as he expected. Always bet on the safer approach but don't argue with experts - generally.

 

[Akimbo]

A bent or embolized diver can be treated after surface recovery still alive if the facilities are available. A diver who drowns at depth, not so much.

The basic axiom that I live by is avoid drowning, embolism, and getting bent — in that order.

Each is progressively more treatable and less time critical.

 

[Mod63]

additional information, apparently based on computer read outs but not confirmed by official sources:

- diver was on a JJ Rebreather
- ppO2 was between 1.9 and 2.2 during accent, apparently to speed up decompression
- most likely diver convulsed, accent from 27m was straight up, ruptured lungs are supporting this theory

 

[J-Vo]

I would not assume that. Without looking at dive planning software, I would assume that those stops are where most of the decompression time is done.

I have done a number of dives to about the 275 feet/84 meters, not much more than half of this planned dive, with total run times of about 2 hours. When I reach the 30 foot/9 meter stop, I am generally about half way through the dive, planning to switch over to oxygen at the next stop, which would greatly accelerate the speed of off-gassing and shorten the dive time. The 3 meter and 6 meter stops on oxygen are therefore the most important in total dive time; they are where you do most of your real decompressing. If I had to ascend immediately from the 40 foot/12 meter stop, I would not expect a pleasant outcome.

My 2nd to last dive surface GF was >300% when I cleared my 40' stop if memory serves me well. I would not expect to survive a direct ascent at that point. This was pretty much the same dive as you describe. I'm pretty sure I still had 90 minutes of deco at that point.

EDIT: Checking my log, surface GF at the end of my 40' stop was >200% with 100 minutes of deco remaining. I still would not expect to survive a direct ascent.

 

[telemonster]

additional information, apparently based on computer read outs but not confirmed by official sources:

- diver was on a JJ Rebreather
- ppO2 was between 1.9 and 2.2 during accent, apparently to speed up decompression
- most likely diver convulsed, accent from 27m was straight up, ruptured lungs are supporting this theory

Was it common for the diver to run high ppO2 like that on every dive? Could have been a mishap or equipment issue?

 

[Brad_Horn]

Could have been a mishap or equipment issue?

As noted at rebreathers – John Clarke Online any pre-dive planning for a 3'C 150m dive on a JJ-CCR would have immediately identified a known issue.

Noting the JJ-CCR manual gives:

Running time: 120 min at a constant depth (40 m)
180 min with dive profile (40 m)
150 min with dive profile (100 m)

Dive profile: 40 min at 40 m, 5 min at 15 m, 9 m
(40 m) for the remaining time
Dive profile: 10 min at 100 m, 2 min at 40 m, 2 min
(100 m) at 15 m, 9 m for the remaining time

 

[KenGordon]

As noted at rebreathers – John Clarke Online any pre-dive planning for a 3'C 150m dive on a JJ-CCR would have immediately identified a known issue.

Noting the JJ-CCR manual gives:

Running time: 120 min at a constant depth (40 m)
180 min with dive profile (40 m)
150 min with dive profile (100 m)

Dive profile: 40 min at 40 m, 5 min at 15 m, 9 m
(40 m) for the remaining time
Dive profile: 10 min at 100 m, 2 min at 40 m, 2 min
(100 m) at 15 m, 9 m for the remaining time

Maybe he had the optional bigger scrubber? Or maybe the high ppO2 was deliberate to keep the dive within 150 minutes? Or maybe he had done such a depth and runtime before and not had co2 issues.

For non CCR people: these testing scrubber duration numbers are widely ignored with various justifications, mainly temperature (not applicable here) and breathing rate. The testing is performed with some ridiculously high worst case breathing rate and quite high co2 output.

CO2 breakthrough due to scrubber life would almost certainly not have happened inside an hour. Brad is just slagging off the divers involved in a “my pdf is better than your physical, delivered and widely used rebreather” style.

 

[Dan]

CCR diving is just more complicated than OC, as shown in the result of the paper, below, where CCR death is about 10x of OC death.

https://www.divegearexpress.com/pub/media/Documents/miscellaneous/Fock-Rebreather_deaths.pdf

 

[Vicko]

As noted at rebreathers – John Clarke Online any pre-dive planning for a 3'C 150m dive on a JJ-CCR would have immediately identified a known issue.

Noting the JJ-CCR manual gives:

Running time: 120 min at a constant depth (40 m)
180 min with dive profile (40 m)
150 min with dive profile (100 m)

Dive profile: 40 min at 40 m, 5 min at 15 m, 9 m
(40 m) for the remaining time
Dive profile: 10 min at 100 m, 2 min at 40 m, 2 min
(100 m) at 15 m, 9 m for the remaining time

I was present in the water when a 300 minute dive was done on a JJ (5 or 6 of them actually), deeper than 100 meters in high current and storm conditions on the last 3 stops. Could you explain why those divers, along with hundreds of divers diving JJ and similar scrubber capacity rebreathers are not dropping dead due to scruber failure?

 

[Brad_Horn]

Maybe he had the optional bigger scrubber?

A valid consideration. For reference https://jj-ccr.com/wp-content/uploads/2017/08/151030_xrc_product_sheet.pdf

And which for a pre-dive planning a 150m dive in 3-4’C water for a 180min run time, the XRC scrubber breaks through at what depth/time?

Or maybe the high ppO2 was deliberate to keep the dive within 150 minutes? Or maybe he had done such a depth and runtime before and not had co2 issues.

I believe the dive planning was for 180min, which is when the buddy safely surfaced, but happy to be corrected.

and noting rebreathers – John Clarke Online your second point is worthy because Russian Roulette works the same way I assume!

For non CCR people: these testing scrubber duration numbers are widely ignored with various justifications, mainly temperature (not applicable here) and breathing rate. The testing is performed with some ridiculously high worst case breathing rate and quite high co2 output.

If you consider the 40L/min breathing rate used for scrubber duration testing ridiculously high? What do ‘you’ figure the norm for a rebreather dive is under stress, swimming?
Assuming one plans for their scooter or buddies to maybe not work on such a dive.
Maybe factor in needing to rescue ones buddy as well potentially, or not, as suits.

Noting that the JJ-CCR testing wasn’t done at the mouth either, so you’d also need to take into account the relevant deadspace of the DSV or BOV, as fitted. And the impact on the %SEV of CO2 breathed. When looking at what your safety margin isn’t pre-dive.

CO2 breakthrough due to scrubber life would almost certainly not have happened inside an hour.

Unless perhaps the majority of that hour, call it 48min, was spent deeper than 40m, perhaps doing a dive to 150m in 3-4’C water…..

You might be surprised how quickly certain scrubber break through at depth in cold water. There’s a reason why a profile for scrubber duration is quoted in marketing literature by every rebreather manufacturer.

Using the 3rd party VMS RedBare performance, which would appear to be the largest single scrubber option available on the market with robust testing, I still don’t believe you could have used it’s longer quoted endurance to plan such a dive. The only possible safety buffer is workload as you’ve exceeded all other parameters: temp colder than CE test criteria, depth 150% greater……
“ VMS RedBare Manual v2.0.3
CARBON DIOXIDE ENDURANCE
During CE testing the Unit achieved the following minimum results for carbon dioxide endurance:
100m - 47 minutes (using 10/80 diluent)
40m - 144 minutes (using an air diluent)
This is the breakthrough time to 5 mB of CO2 in 4 degrees of water, at a breathing rate of 40 l/min and a CO2 injection rate of 1.6 l/min.”

I was present in the water when a 300 minute dive was done on a JJ (5 or 6 of them actually), deeper than 100 meters in high current and storm conditions on the last 3 stops. Could you explain why those divers, along with hundreds of divers diving JJ and similar scrubber capacity rebreathers are not dropping dead due to scruber failure?

What was the water temp?
Where they finning, towed behind a scooter or chilling on a deco station?
How much deeper than 100m and for how long?
How much did they flush their loop during deco…. purging Co2.
Were they using DragerSorb that might offer better duration than that used in the quoted scrubber duration….
Any stressors or equipment failures….

Look at that units scrubber duration testing and work out where their safety margins were…… and weren’t.
The safe diving envelope of a rebreather is pre-set by its engineering design. If you stay inside that boundary you stay alive, exceed it and you’ll almost certainly keel over.
It’s worth understanding rebreathers – John Clarke Online as that safe envelope boundary isn’t necessarily fixed. And also varies from diver to diver based on their variability.