Fatality on Rosalie Moller wreck

[scubadada]

CO2 retention in hyperbaric conditions is the realm of @Dr Simon Mitchell
Read the articles here: Advanced Knowledge Series – Dive Magazine

It's a subject that is part of the knowledge required for technical diving.
And this accident unfortunately illustrates one of the reasons why recreational diving has a limit of 40m/130ft.

Thanks, excellent read

 

[ginti]

CO2 retention in hyperbaric conditions is the realm of @Dr Simon Mitchell
Read the articles here: Advanced Knowledge Series – Dive Magazine

It's a subject that is part of the knowledge required for technical diving.
And this accident unfortunately illustrates one of the reasons why recreational diving has a limit of 40m/130ft.

Thanks a lot, great material! I have finished the 3 articles not related to rebreather, but I couldn't find the graph you showed before, which I find interesting.

This!
Most (recreational) divers are not aware how effectively you can breathe out at depth, and thus get rid of CO2. At the surface our body reacts to elevated CO2 levels accurately, but not anymore under increased pressure.
View attachment 615019
At 50-55m, exercise will result in a rapid CO2 elevation, adding to an already increased narcosis level.

It's how effectively you can breathe out -> exhale carbondioxide

In the graph, the abscissa is a percentage... I was wondering, percentage of what? By any chance, of the CO2 we can effectively exhale at 1atm? Or something else?

Also, the graph is made assuming the diver is breathing air or another gas?

Thanks again!

 

[Miyaru]

I just looked through quite some documentation, but couldn't find it that quickly (when I do, I'll update this). I use that graph in my own course materials.
It origins from study by Gavin/Mitchell where the end-tidal CO2 levels were measured in CCR diving. The Work-Of-Breathing is slightly higher on closed-circuit than open-circuit, but the physiology of the lungs and trachea doesn't change.

Our body has evolved to effectively breathe at 1 atmosphere. The gasdensity is about 1.23 grams per liter at sea level in 15°C.
Once you descend, pressure increases and so does the gas density. And with increased pressure our physiology doesn't work flawless anymore. It becomes harder to breathe out, since the air is much denser. You're not breathing out as effective as on the surface. Because there's more residual CO2 in your lungs, the blood can off-gas less CO2 to the lungs.

On the surface, your brain stem would immediately send a signal to your lungs to breathe faster. Under pressure, that mechanism doesn't work at 100%. The urge to breathe faster is diminished and the CO2 levels keep rising.
It gets really problematic when the gas density exceeds 5.8 g/l (at 40m/130ft the air density is almost 6 g/l !!)

Anything that turns oxygen into carbondioxide adds to a CO2 hit. Your brain is the biggest oxygen consumer.
Add some excess muscle movements to this, like chasing a weightpocket down to 55m, grabbing it and then trying to ascend with strong fin kicks, and the requirements for a brain-shutdown have been met.
You simply fall asleep like a switch turns off the light.

 

[dmaziuk]

...Anything that turns oxygen into carbondioxide adds to a CO2 hit. Your brain is the biggest oxygen consumer.
Add some excess muscle movements to this, like chasing a weightpocket down to 55m, grabbing it and then trying to ascend with strong fin kicks, and the requirements for a brain-shutdown have been met.
You simply fall asleep like a switch turns off the light.

Also what @kelemvor said earlier: at .28 you're looking at ppO2 of 1.7 at 55 msw. Apparently CNS oxtox symptoms "at ppO2 over 1.6 can take from hours to minutes" to develop and "many external factors, such as underwater immersion, exposure to cold, and exercise will decrease the time to onset of central nervous system symptoms. Decrease of tolerance is closely linked to retention of carbon dioxide."
-- Oxygen toxicity - Wikipedia
Chasing the weight, she shouldn't have been down long enough but who knows.

 

[Vicko]

Why are we considering CO2 hits and O2 tox in divers that panicked almost on the surface and swam down to 50 meters when already close to a out of air situation?
I know that my opinion is unpopular and I don't have even half of the experience of some people in this conversation but this incident happened because of lack of training in recreational divers.
If her instructor during AOWD or even OWD did a deco simulation with her and if she did some backgass deco dives before this trip D. would still be alive. Every student that i passed in AOWD did a deco simulation, most of them after the course also did a light deco dive.
It's not hard, it's negligibly more dangerous then a 30+ meter NDL dive and it's frankly ridiculous how many people mythologize dives that are being done all over the world (mostly the Med and Egypt) with very little to no accidents in the last 30 years to back up the claims.
Air does not kill if you take 3 breaths of it at 40 meters, OxTox does not kill after a few minutes of exposure above 1.4, Co2 does not put you to sleep in normal conditions at such low densities and exposure times and you don't need advance trimix and 3 stages to do a deco dive that lasts less then 45 minutes including the deco.

 

[runsongas]

@KenGordon well if you were going to snuff it otherwise on a dive, they should have a DM nanny you. getting certified as a european diver doesn't mean you get issued a license to kill yourself on dives beyond your skill and experience level.

 

[ginti]

Why are we considering CO2 hits and O2 tox in divers that panicked almost on the surface and swam down to 50 meters when already close to a out of air situation?
I know that my opinion is unpopular and I don't have even half of the experience of some people in this conversation but this incident happened because of lack of training in recreational divers.
If her instructor during AOWD or even OWD did a deco simulation with her and if she did some backgass deco dives before this trip D. would still be alive. Every student that i passed in AOWD did a deco simulation, most of them after the course also did a light deco dive.
It's not hard, it's negligibly more dangerous then a 30+ meter NDL dive and it's frankly ridiculous how many people mythologize dives that are being done all over the world (mostly the Med and Egypt) with very little to no accidents in the last 30 years to back up the claims.
Air does not kill if you take 3 breaths of it at 40 meters, OxTox does not kill after a few minutes of exposure above 1.4, Co2 does not put you to sleep in normal conditions at such low densities and exposure times and you don't need advance trimix and 3 stages to do a deco dive that lasts less then 45 minutes including the deco.

There is never a single cause to a death like this one. It is more an escalation of factors. There are two important things to do in such cases (imho):
1 - identify the physical cause; in this case, some people here assumed it is about CO2, maybe combined with O2 toxicity, and maybe not enough gas (btw, O2 toxicity gets worst under hypercapnia)
2 - human factors, namely "why this person did something so dangerous?", which often is an analysis of the escalation I mentioned before; in this case, several factors have been mentioned, including lack of training... it doesn't seem that your opinion is unpopular

However, I do not understand the advantage of exposing AOW students to deco; out of curiosity, why do you think it is an added value for them? I am not criticizing you, I am just genuinely curious, since my perception is different (I think she shouldn't have done this dive; personally, I didn't jump in the water for way less in the past)

EDIT: as far as I understand, CO2 is supposed to increase the risk of seizures associated to O2 toxicity; this happens because, with high level of CO2 in the blood, more blood goes to the brain and the risk of neurological toxicity caused by O2 increases. If she had the regulator in her mouth, I guess seizures are unlikely... then, I do not know if other possible effects of O2 toxicity could have played a role and, if yes, whether the CO2 played a role in increasing the toxicity itself... more info in the links posted before by @Miyaru

 

[Vicko]

However, I do not understand the advantage of exposing AOW students to deco; out of curiosity, why do you think it is an added value for them? I am not criticizing you, I am just genuinely curious, since my perception is different (I think she shouldn't have done this dive; personally, I didn't jump in the water for way less in the past)

Because sooner or later they will encounter a deco dive. Either because of the dive the dive shop is doing on those days or like in the case of this incident due to bad planning and unfortunate circumstances. I would prefer that they try it out in a controlled environment and prepare themselves at least mentally. Around 30% of dives you do in Croatia, Spain or Italy will have a group of divers going into deco, intentionally with only a single tank and I don't see hundreds of reports from those areas involving DCS or worse incidents (actually Croatia has an average of less than 10 reported DCS incidents a year and we dive like lemmings)

 

[ginti]

Because sooner or later they will encounter a deco dive. Either because of the dive the dive shop is doing on those days or like in the case of this incident due to bad planning and unfortunate circumstances. I would prefer that they try it out in a controlled environment and prepare themselves at least mentally. Around 30% of dives you do in Croatia, Spain or Italy will have a group of divers going into deco, intentionally with only a single tank and I don't see hundreds of reports from those areas involving DCS or worse incidents (actually Croatia has an average of less than 10 reported DCS incidents a year and we dive like lemmings)

Ok, got it. Personally, I do not agree, since people use to go for AOW classes very soon and it may be wiser to wait before to do deco dives, even in the condition you described. But I don't have the experience neither the knowledge for arguing about it... this is a task for you instructors

However, I do not think that, in a case like this one, knowledge of decompression could have helped

 

[Mod63]

@KenGordon well if you were going to snuff it otherwise on a dive, they should have a DM nanny you. getting certified as a european diver doesn't mean you get issued a license to kill yourself on dives beyond your skill and experience level.

I think Ken was alluding to the fact that a lot (not all of course) of European divers are trained differently and do "unsupervised" dives most of the time. To those (including me) having to follow a DM is a no go, unless we specificly ask for a guide - and then it is a guide and not a nanny. I was on trips where the guides had days off on end and usked us if they were allowed to come along, because nobody on the boat needed/wanted a DM. And those that have come up in BSAC/CMAS/VDST haven been trained in deco theory from an early stage.