OUT OF AIR - Last ditch effort breath from you BCD

[redacted]

Previous discussion of the subject: http://www.scubaboard.com/showthread.php?t=32002&highlight=breath

Probably has undergone a bit of cleanup as many hackles were raised.

 

[Sideband]

In an emergancy situation there is no reason why not. Even if there is only 1 lung full (or should that be a pair of lungs full) you can always exhale back into your BC to give you bouancy and rebreath it again as your lungs will not take all the O2 out of the air. I think Id rather do this than ascent from 20m kicking as quick as I can. That sounds like a sure fire way to an embelizim of some kind.

Huh? Moving air from the BC to the lungs or lungs to the BC will not change buoyancy at all so I'm not sure where you were going with that.
Rebreathing the air is a great way to black out and die.
Exhaling or keeping the airway open on ascent will prevent an air embolism.

Joe

 

[wdlk]

Interesting discussion. Just my two cents worth. Kicking as fast as I can to the surface would burn O2 at a higher rate than a slow controlled ascent. Same principle as slow swim at depth. Swim slower = conserve air = more time. Given a 60ft/min ascent rate, you can get to the surface in one minute from 60ft, minute and a half from 90ft. Not a long time to hold your breath (with slow exhale), given that as you ascend the air in your lungs would expand.

I would not spend time practicing breathing from my BC, but would practice slow exhale until I could do it for more than a minute. Seems that would serve as better use of my training time and I could practice this anywhere/anytime. With a little practice, you can hold our breath for 2-4 minutes (takes practice, but easily achievable). More than enough time to surface from rec dive depths (or swim to your buddy if needed, better solution).

Even better solution, plan your dive with redundant air source (Octo, BUDDY, Pony bottle, etc.). Even if total failure of your air source, you would have alternate to get the surface without holding your breath.

With proper planning, the only possible situation that should put you in an OOA situation on a rec dive would be that your tank explodes. This however would eliminate the requirement for you to breath underwater, because you would be so occupied feeding the fish.

 

[O2BBubbleFree]

I would not spend time practicing breathing from my BC, but would practice slow exhale until I could do it for more than a minute. Seems that would serve as better use of my training time and I could practice this anywhere/anytime. With a little practice, you can hold our breath for 2-4 minutes (takes practice, but easily achievable). More than enough time to surface from rec dive depths (or swim to your buddy if needed, better solution).

That sounds like a bad idea to me. Several who posted on a thread wrt long CESAs said that their experience showed that it takes quite a 'quick' exhale to vent the expanding gas (one guy described it as yelling!). If you practice as you described, you are not accounting for gas expansion, and could be practicing an exhale rate that is too slow to be safe.

As the agencies teach, the 'ahhhhh' sound keeps the throat open so expanding gas can escape as necessary. You DO NOT want to try to limit that rate.

 

[rockjock3]

That sounds like a bad idea to me. Several who posted on a thread wrt long CESAs said that their experience showed that it takes quite a 'quick' exhale to vent the expanding gas (one guy described it as yelling!). If you practice as you described, you are not accounting for gas expansion, and could be practicing an exhale rate that is too slow to be safe.

As the agencies teach, the 'ahhhhh' sound keeps the throat open so expanding gas can escape as necessary. You DO NOT want to try to limit that rate.

You also have to remember some additional things. The need to breath is not just lack of oxygen but also need to rid the body of carbon dioxide. Also, holding your breath longer doesn't mean you will get much. more oxygen out of it as it expands.

With a CESA you don't continue to ascend at 30FPM you ascend to the surface and possible and chances are you will ascend faster than 60fpm. You still need to try and keep control though and not just swim as fast as you can (as noted that will use up the oxygen in you blood faster).

 

[cummings66]

One thing not directly mentioned in this thread is air management. To be on the surface with 500 psi tells me that you have not considered your buddy. Imagine if you will that you have 500 psi in an 80 cf tank and now your buddy has none. That 500 psi will be gone within a blink of an eye and you'll both be doing a CESA. 500 psi on the surface is not planning if you've gone beyond basic OW, unless of course you're diving solo.

One other item not covered, or rather it was but it doesn't accurately reflect all diving situations and that is your wing will be nearly empty at depth. If you have a thick wetsuit on as you get deeper you will have more air in your BC than you would if you dive as I do in a Viking drysuit. I really do have almost no air at all in my wing at 100 feet, but in a 7mm wetsuit I have more air than that. I could see getting a breath off it if I had a 7mm on and was 100 feet down, but it would not be my first choice and in my current config I know there would not be enough air in it to help.

Honestly, I believe the intent of the question was along the lines of is it possible and yes it is under the right conditions.

Is it advisable? That's for another thread because we've covered the reasons not to quite well.

 

[tjmills]

One thing not directly mentioned in this thread is air management. To be on the surface with 500 psi tells me that you have not considered your buddy. Imagine if you will that you have 500 psi in an 80 cf tank and now your buddy has none. That 500 psi will be gone within a blink of an eye and you'll both be doing a CESA. 500 psi on the surface is not planning if you've gone beyond basic OW, unless of course you're diving solo.

What does this mean exactly? 500 psi is hardly gone in a blink of an eye but I am unsure what you are trying to say here. If I am on the surface with 500 psi....seems ok to me.

 

[Tom Winters]

I almost drowned twice surfing - never diving though. Both times I thought I was a goner - I just could not make it to the surface, and I was out of air. But amazingly enough, there is a small reserve of air in the top of your lungs that will get you up...maybe, even when the CO2 buildup is screaming in your ears.
I did one out-of-air ascent from around 70' once. No rush for the surface - I was going to make it or not make it - whatever. I had a good lungfull at 70' and never felt like I was a dead man rising. The two times surfing though, I was dying.
The breathing off a bc is sheer nonsense though, unless the bc is brand new. The junk that grows inside there, especially in the tropics, is not what I'd want in my lungs period. The time that you would spend messing with the corrugated hose and switching hoses - that would kill you for sure.
Also, if you're going to post here, at least let people know who you are also.

 

[Kim]

The junk that grows inside there, especially in the tropics, is not what I'd want in my lungs period.

Which is another very good point. If it was to be in any way useful you need to practice the skill. Practicing this particular skill could land you in hospital really quickly! :11:

 

[dumpsterDiver]

I think the whole idea sounds stupid. If you are in that much trouble (and out of good options) you should ditch lead, keep the reg in your mouth and hope you can sip a little air out on the ascent and swim as slow as you think possible that will get you to the surface before passing out.

However, I have a friend who was diving solo and quitely catching tropical fish at around 80 feet. He was negatively bouyant and due to his very slow and relaxed breathing rate, when he first sensed a reduced air flow on inhalation, he swears he was basically completely out of air. He carries no ditchable weight with a thin suit and a big steel tank. He immediately started to swim up, I'm not sure if he did (or could inflate the BC) and he ran desperately out of breath. He recycled his exhalations by breathing in and out of the BC on the ascent and he said that he just barely maintained conciousness. He swears that this technique saved his life.

He now ALWAYS uses a pony bottle.