Re-using air from BCD in dire emergency?

[stefo2]

I've also tried breathing from my BC just as part of my emergency "bag of tricks." I thought about it in case of a "out of air" situation on a deco dive where all you had was your deco gas and needed to get to your first stop.

I'm not a deco diver, nor am I Nitrox certified, so correct me if I'm wrong - but isn't oxtox a gradual process? If so, I think taking a breath or two from your deco gas while ascending to your first stop, even at a depth which exceeds the safe limits for that gas mix, would be preferable to breathing from your BCD (while at the same time trying to control your ascent).

 

[Web Monkey]

I don't know squat about submarines, but wouldn't rocketing to the surface in a "survival suit" from 600' leave the user laying on the surface fizzing like a hot can of coke?

Terry

Edit: Just thinking about it. Are subs pressurized to ambient or surface pressure?

 

[Rick Inman]

I'm not a deco diver, nor am I Nitrox certified, so correct me if I'm wrong - but isn't oxtox a gradual process? If so, I think taking a breath or two from your deco gas while ascending to your first stop, even at a depth which exceeds the safe limits for that gas mix, would be preferable to breathing from your BCD (while at the same time trying to control your ascent).

Yup, if it was me and I was so silly as to find myself OOG and without a buddy on a deco dive, I would grab a breath from my first deco gas and plow up to 2.0, then slow to the first stop. For example, on a 150' dive, you'd have a breath of 50% with a PPO2 of 2.7. But almost instantly you'd be drooping that PPO2 as you ascend, and in no time at all you'd be at 100' at 2.0 and moving up to your 70' stop.

 

[TSandM]

If I found myself out of gas on a deco dive with no buddy in sight, I'd hope I'd wake up soon.

 

[Gene_Hobbs]

Hope you don't mind that I reversed the order to answer...

Edit: Just thinking about it. Are subs pressurized to ambient or surface pressure?

Subs are pressurized to surface pressure for normal operations. The problem in a Disabled Submarine (DISSUB) situation, the pressure inside the sub may very well be rising. There is a significant amount of work that is done to look at care and treatment of these submariners before, during and after an escape.

I don't know squat about submarines, but wouldn't rocketing to the surface in a "survival suit" from 600' leave the user laying on the surface fizzing like a hot can of coke?

In a best case, the sub will remain pressurized to 1 ATA and the submariner would rapidly compress and exit. The rapid ascent should allow for a VERY limited inert gas exposure. This gets more difficult should something delay the exit. In a worse case, the submariners would be saturated to some pressure greater than 1 ATA and exit pre-breathe procedures will be taken to facilitate inert gas elimination prior to exit.

A good history of DISSUB by David Elliott can be found here (short, interesting read):
Elliott, D. A short history of submarine escape: The development of an extreme air dive. South Pacific Underwater Medicine Society Journal 1999 Volume 29 Number 2. RRR ID: 6001

Additional reading on pre-breathe, incidence of decompression sickness, treatment, ect. is available with the keyword DISSUB.

 

[SteveAD]

I don't know squat about submarines, but wouldn't rocketing to the surface in a "survival suit" from 600' leave the user laying on the surface fizzing like a hot can of coke?

Terry

Edit: Just thinking about it. Are subs pressurized to ambient or surface pressure?

Subs operate at 1atm so submariners are not nitrogen saturated. The only pressure concern on a submarine escape is direct barotrauma so they can ascend at speeds that divers would consider suicidal so long as they maintain an open airway.

Gene beat me to the punch with a much more comprehensive answer.

 

[boulderjohn]

By following the same principle, then a diver does not need to know, much less practice, CESA just to make another classic example.

This is an excellent point and well worth its own response.

TS&M's example was of someone near to the exit point of a cave, with no CESA available as a consequence. Once clear of the cave exit, a CESA is available to you.

The reason I would not bother with breathing from my BCD is that I know how to do a CESA, which makes that kind of breathing unnecessary. In any kind of situation where I am able to ascend directly to the surface, the CESA will do the job. If I am in any other kind of situation (like TS&M's example), breathing from the BCD will give only a marginal and short-lived advantage.

Even if you are somehow completely OOA with nothing in your lungs, you have enough O2 in your blood to get you to the surface in almost any situation without a need for another breath. If you do need another breath, you will get it from your tank. Your tank is not OOA at depth--it is just unable to deliver it at ambient pressure. When you ascend to a lesser pressure, you will get air from your regulator--provided that you still have it in and are not instead sucking on your inflater hose.

 

[KMD]

It can be a sanity breath.

In an overhead envionment if you are sharing gas, the other diver is in front of you and breathing off your long hose on your right post. You are breathing off for backup on the left post which is susceptable to rolling off.

If you in a restriction you might not be able to get to your left post right away. In this case you could get a breath or two by activating your power inflator which runs off your right post.

 

[Codyjp]

CO2 toxicity is gradual. The first symptoms are air hunger and anxiety, and as CO2 builds, you get lethargic and eventually lose consciousness. One of the nasty toxicities of CO2 is acidosis, which builds very quickly and can lead to cardiac arrhythmias. However, if I were 100 feet from the exit to the cave and completely out of gas, I'd try it. I'd try anything; wouldn't you? And if I made it out, I'd sell all my gear because I was clearly much too stupid to continue to dive, for having gotten myself into that bad a situation.

Brilliant! I love it! Thanks Lynn.

 

[AfterDark]

Tell us more! You had a sudden reg failure where the reg failed closed, not open? One breath was perfect then the next - nothing? And no buddy? This is so extremely rare for a reg to fail closed suddenly like that and be buddy-less at the same time... What brand of reg was it? What caused the failure? Were you solo diving?

Here's the link with a little more info::
http://www.scubaboard.com/forums/vintage-equipment-diving/269229-scubapro-mark-v-10.html Thank God it's extremely rare, scared the crap outa me followed by rage.