Independent Swimming OOA

[verona]

Some of you have written that you have done swimming OOA ascents and referred to what the books also describe about air expanding in your lungs/tank etc as you come up.

Fortunately, I have never had to do one of these ascents , though maybe I should do a practice one.

Anyhow, what I was wondering was, presumably if you are OOA you notice when you take a breath in and find there is nothing. Temptation must be to hold your breath. But if you keep trying to breath, how soon on your ascent do you feel air coming and does it feel as this happens like you can breathe again? Or does it feel like it does when your air is turned off - you get a bit but it is hard going?? Just wondered and knock on wood, will never have to do it.

 

[Diver0001]

Some of you have written that you have done swimming OOA ascents and referred to what the books also describe about air expanding in your lungs/tank etc as you come up.

Fortunately, I have never had to do one of these ascents , though maybe I should do a practice one.

Anyhow, what I was wondering was, presumably if you are OOA you notice when you take a breath in and find there is nothing. Temptation must be to hold your breath. But if you keep trying to breath, how soon on your ascent do you feel air coming and does it feel as this happens like you can breathe again? Or does it feel like it does when your air is turned off - you get a bit but it is hard going?? Just wondered and knock on wood, will never have to do it.

Depends on how deep you started how fast you ascend and how empty the tank really was when you started ascending.

However, the point of keeping the regulator in your mouth during ascent isn't that you might get a little air on the way up. It's all about the urge to inhale. At some point the urge will win over and you'll try to inhale and it's better if you suck vacuum or even get a little air than if you take on water. I'd say visualize not getting any air and then anything you get will be a pleasant surprise.

And to answer your question directly. It will feel like a trickle. You have to make a slow controlled breath to sort of suck it out of the reg at those pressures. It doesn't feel normal.

R..

 

[H2Andy]

Fortunately, I have never had to do one of these ascents , though maybe I should do a practice one.

ok, not to be doom and gloom, but remember, this is a very
hazardous thing to practice simply because the results can
be so catastrophic if done wrong.

you must keep your airway open at all times so taht expanding
air can exit your lungs without tearing them up and causing
damage.

i have only had to do one of these for real once, and i screamed "Fudge" (the R version) all the way up to the surface, just to make sure my airway was open. i kept
the regulator in my mouth the whole time.

thankfully, it was only from about 50 feet, and i was able to
"last" all the way to the surface without the need to inhale
overpowering me.

 

[gchapman]

Some of you have written that you have done swimming OOA ascents and referred to what the books also describe about air expanding in your lungs/tank etc as you come up.

When you did your Open Water did you have to practice a CESA from 20ft or so? Perhaps this is just a PADI-ism...

 

[jbd]

You may have the urge to hold your breath but compliments of Boyle's law you pretty much won't be able to. As noted the idea is to keep your airway open and let the air escape from your lungs as you ascend.

While I understand H2Andy's point about the dangers, I do think that this is something that should be practiced from time to time during your diving season. I do a lot of my ascents like this accept I maintain the normal ascent rate of 30 feet per minute.

I have practiced with a faster ascent rate from 40 feet on several occassions.

Practice is what gives you the ability to do the right thing at the time it is the most important to you.

 

[FredT]

When starting up you are starting at the bottom of your tidal volume, since you don't know you're out until you try to inhale. When you inhale you get little or nothing. IF you are deep and open the airway without _trying_ to exhale you probably won't get much in the way of bubbles for the first 20-30'. The gas expansion in your lungs simply starts refilling them. As you come up the bubble stream increases a bit, then goes nuts the last 30'. Crunch the numbers using the gas laws on raising an inverted barrel half full of air from over 90' to see how this works.

As another hint the urge to breathe is translated in the braiin as "move air". The brain doesn't seem to care which way. Keep some air flowing and the throat spasms stay away. Forcing exhales when you are already "empty" is a fast track to throat spasms. Starting up empty from 130' you get about 4 lungfulls if you don't force the exhale, but keep a few small bubbles coming out. At the same time ANY fullness in the chest indicates it's time to start pushing to make the bubbles bigger!

 

[H2Andy]

While I understand H2Andy's point about the dangers, I do think that this is something that should be practiced from time to time during your diving season.

oh, i agree. this is definetely a skill you want to do well.

just think things through ahead of time and understand
the risks.

 

[verona]

Thanks, Fredt, that reply was really helpful.

H2Andy - I absolutely take your point. Thing is, as you know, practice is such a key thing in scuba to overlearn and so important in an emergency when you aren't thinking straight. It's one thing perfecting the CESA in a pool or in 20 feet of OW when there's air in your tank but another if you run out for real at 100 feet. But you are right - it would be ironic to burst a lung practising!! Not to mention potentially fatal.