Current Views on Hypoxic bailout/BOV Configurations

[lermontov]

From the reports I’ve read and people I’ve talked too, that is the most common pattern. But a couple of people have reported just feeling more clumsy and and little bit off. And wondering why their teammates are shoving regulators at them. Not that a BOV isn’t perfectly usable is that situation, but a CO2 hit doesn’t always manifest in one way.

Both of the people involved were pretty confident that without their teammates intervention they wouldn’t have bailed out. While they were bouncing off the ceiling and floor of the cave, to the affected divers this wasn’t a big deal, while their their teammates knew something was horribly wrong with them.

Id like to have a realistic assessment of the risks of becoming incapacitated by a CO2 hit -out of the rmillions of hours of CCR diving around the world each year how many dives end in fatality or near fatality. i suspect its a risk that is incredibly remote as a percentage , one that is further reduced by checklist and maintenance procedures. eg not pushing scrubber times, not driving/travelling around with half used scrubbers getting vibratred.

 

[Wibble]

Id like to have a realistic assessment of the risks of becoming incapacitated by a CO2 hit -out of the rmillions of hours of CCR diving around the world each year how many dives end in fatality or near fatality. i suspect its a risk that is incredibly remote as a percentage , one that is further reduced by checklist and maintenance procedures. eg not pushing scrubber times, not driving/travelling around with half used scrubbers getting vibratred.

Isn't the problem best put another way: the outcome of a CO2 hit is so significant and life threatening that a BOV is worth the money in just the same way as an airbag is on a car?

A BOV makes switching to OC easier, so much so that you might just do it as opposed to listening to your idiot brain saying "I can't be arsed to switch over as it's so tedious to clean up afterwards"?

My idiot brain does things like that -- I listened my idiot brain when I forgot to test+validate+connect my drysuit hose and continued to 35m and my shoulder looked like a Stilton cheese afterwards...

 

[lermontov]

Isn't the problem best put another way: the outcome of a CO2 hit is so significant and life threatening that a BOV is worth the money in just the same way as an airbag is on a car?

A BOV makes switching to OC easier, so much so that you might just do it as opposed to listening to your idiot brain saying "I can't be arsed to switch over as it's so tedious to clean up afterwards"?

My idiot brain does things like that -- I listened my idiot brain when I forgot to test+validate+connect my drysuit hose and continued to 35m and my shoulder looked like a Stilton cheese afterwards...

yes good point , Im more interested in pinpointing what that risk actually is and its only calculable as a risk if you compare it with other risk percentages. Its not that its not a significant outcome its how likely is it? (like how insurance companies work) I mean let's compare it with other things. Is it more likely than say a burst wing or a fatal bite or a down current, DCS hit etc

Does anyone know how many have died because they had a co2 hit and didnt have a BOV and used all their gas

 

[Brad_Horn]

yes good point , Im more interested in pinpointing what that risk actually is and its only calculable as a risk if you compare it with other risk percentages. Its not that its not a significant outcome its how likely is it? (like how insurance companies work) I mean let's compare it with other things. Is it more likely than say a burst wing or a fatal bite or a down current, DCS hit etc

Does anyone know how many have died because they had a co2 hit and didnt have a BOV and used all their gas

On the CO2 hit leading to fatality about the best data / risk level you'd be able to work off is 1 in 5
As to the further caveats you'd have to do some digging into the only publicly released rebreather accident reporting.... https://deeplife.co.uk/or_accident.php

Then you could go a step further and also investigate if the unnecessarily high WOB of the specific BOV in question (if any was fitted) further contributed to the problem!

 

[cathal]

Unsubstaniated causes of death from an openly proven fault laden list of rebreather fatalities are not worth the amount of megapixels used in your pie chart tbh.

 

[Wibble]

yes good point , Im more interested in pinpointing what that risk actually is and its only calculable as a risk if you compare it with other risk percentages. Its not that its not a significant outcome its how likely is it? (like how insurance companies work) I mean let's compare it with other things. Is it more likely than say a burst wing or a fatal bite or a down current, DCS hit etc

Does anyone know how many have died because they had a co2 hit and didnt have a BOV and used all their gas

Today’s dive…

English Channel the spring algae bloom has started with a vengeance. Visibility now 1m/3ft with all the snot in the water and dark from 20m/65ft.

Was thinking today that I just didn’t want to bail out and get all that crap in my mouth, same for a silty environment. Now dreaming of a BOV where at the flick of a switch I’m breathing clean gas and can switch back to the loop without a mouthful of crap.

 

[Big-swede]

Today’s dive…

English Channel the spring algae bloom has started with a vengeance. Visibility now 1m/3ft with all the snot in the water and dark from 20m/65ft.

Was thinking today that I just didn’t want to bail out and get all that crap in my mouth, same for a silty environment. Now dreaming of a BOV where at the flick of a switch I’m breathing clean gas and can switch back to the loop without a mouthful of crap.

I can think of an even worse situation.

What if you are cave diving and are going through a tight restriction. Your mate who's diving nude today are right in front of you. Second before you realise you have to bail out your mate gets a bad case of diarrhoea.

 

[KevinNM]

There were a couple of retired seals talking on youtube about funny stuff that had happened and one mentioned getting the runs while doing a many hours-long SDV mission. Hilarity ensued…

 

[Gareth J]

Doesn't that violate the first principle: must be self sufficient?

Of course if you suddenly need it and there's a swimming bailout beside you, use it!

However, your first "muscle memory" reaction should be to grab your own bailout regulator. IMHO this should be practised on every dive, not least to confirm the thing's turned on and is in the right place, possibly with the secondary action to drag the cylinder forwards against the bungee (mine are sidemount bungeed) and pull out the reg.


That's a great point and supports the "check bailout on every dive" principle.

I think there is a misunderstanding here.

I do a lot of club diving.
Whilst we have a high ration of members diving twinsets or single and 3l pony, this is not all members.

So if I am diving with an OC buddy, who is on a 'standard' scuba rig (single cylinder, regulator and octopus). I am by default their emergency gas supply. In exactly the same manor if they where diving with another OC buddy on a standard rig. In the even of a gas failure, the OC diver would take their buddies octopus. In my case they take the bailout regulator from the side slung cylinder.

 

[rsingler]

Isn't the problem best put another way: the outcome of a CO2 hit is so significant and life threatening that a BOV is worth the money in just the same way as an airbag is on a car?

It's quite a conundrum. I can't argue with what you've just said, yet I have stayed with a necklaced bailout second stage.

My (?flawed?) reasoning this far has been
1) if I plumb it to my 3l, I've got very little time
2) I've got extra weight and hoses and connections right where I don't want them
3) I've gotta plan how to plumb my extra bottles to plug in soon after the stress of my bailout

Yet... how nice to just flick a switch in an emergency.

To continue the train of justifying a decision that many disagree with, I've also convinced myself I won't get into that situation without  early warning.
Because I realized that (its shortcomings aside), it was an extremely fast solution to a big problem, if I were to consciously reject a BOV, how was I going to recognize a hit? Dr. Simon Mitchell teaches us that fully 25% of divers don't sense their hypercarbia.
So I did this:
Post in thread 'Overshooting NDL and mandatory deco stops' Overshooting NDL and mandatory deco stops

And that's how I justified keeping my simple necklace...

But I think I'm going to try it one more time. I think next time I'll push it as high as I can, and then, instead of just pulling out the mouthpiece and sighing nice, clean air, I'll see if I can hold my breath long enough to purge and place the mouthpiece of a bailout bottle. I've repeatedly read of folks that say they couldn't bear to stop breathing long enough to switch. I think it's a psychological phenomenon (since my O2 sat should be fine at depth), but practicing it can't hurt should I let it go so long before bailout that I'm really panicking.
Or maybe it'll prove that I  have to recognize it early enough to be able to switch. Or maybe it'll prove that I should buy that 12-pound BOV...