Deep CESA Practice Okay?

[boulderjohn]

heres a tried out theory(Done in the pool i hasten to add!) A DM said to me when i was doing my rescue course, "where else do you have air if you run out"? threw me, BCD he says! as you ascend the air expands, it might taste like the proverbial but its air, so we tried it, got neutrally buoyant in the pool (3 mtres) and sucked off the BCD! we got about 3 good lung fulls before it gave up. would this be poss do to in a emergency?

You will probably get more than that from your tank by inhaling through your regulator as you ascend, and it will be nice, clean air coming through a device designed to give it to you. Remember, your tank is not out of air. It just can't give it to you at your present depth because it has to have more PSI than your ambient pressure. I hope your experiment didn't put too much unpleasant stuff that has been hanging around inside your BCD into your lungs.

This idea has been discussed quite a few times, and I agree with the majority who say there is no point in it when the alternatives (breathing from your tank and CESA) are readily available and easy to do.

 

[LeadTurn_SD]

heres a tried out theory(Done in the pool i hasten to add!) A DM said to me when i was doing my rescue course, "where else do you have air if you run out"? threw me, BCD he says! as you ascend the air expands, it might taste like the proverbial but its air, so we tried it, got neutrally buoyant in the pool (3 mtres) and sucked off the BCD! we got about 3 good lung fulls before it gave up. would this be poss do to in a emergency?

A long time ago I was told it was/is "possible", if you don't accidently inhale water, remembered it, etc. I was taught you could possibly breath / rebreath the air in the BC as you ascended.

Not something I ever have (or would) practice. Seems like a wonderful way to get a serious bacterial or fungal lung infection.

Probably (as boulderjohn mentioned above) it is better just to keep the reg in your mouth.

Best wishes.

 

[stargost]

Assuming the 100ft cesa test would be a good idea, before jumping there and test this, I may carry on the following:
- Get in a Olympic pool (50meters) and see if I can do a back and forward swim at the bottom, starting with a normal breath and continuously exhale a little bit (baaaaaa stuff like I was told )
- Manage a Free dive back and forward down to 50ft,
Only fining in both cases

I know it is not comparing apple with apple, and in theory, the cesa could be easier from physics point of view (while in the pool, you don’t have the stress, nor the gear)

But as of now, I know I cannot do easily any of the above (I use to for the free dive when I could stay 2minutes under water, certainly not any more :depressed
So I’ll make sure I won’t stay at 100ft with low gas or without a good buddy

 

[boulderjohn]

Assuming the 100ft cesa test would be a good idea, before jumping there and test this, I may carry on the following:
- Get in a Olympic pool (50meters) and see if I can do a back and forward swim at the bottom, starting with a normal breath and continuously exhale a little bit (baaaaaa stuff like I was told )
- Manage a Free dive back and forward down to 50ft,
Only fining in both cases

I know it is not comparing apple with apple, and in theory, the cesa could be easier from physics point of view (while in the pool, you don’t have the stress, nor the gear)

But as of now, I know I cannot do easily any of the above (I use to for the free dive when I could stay 2minutes under water, certainly not any more :depressed
So I’ll make sure I won’t stay at 100ft with low gas or without a good buddy

From a physics point of view, the 100 foot CESA in the open water is much, much easier than what you describe in either a pool or a free dive to 50 feet.

The key is the expanding air.

When you are at 100 feet on scuba, you have 4 times as many air molecules in your lungs as you do on the surface. As you ascend, that air expands rapidly and comes bubbling out. In a pool, there is no benefit from expanding air. The same is true of free diving.

I have, in fact, argued about this in the past with the way we teach presently. A CESA from even 30 feet is much easier than a horizontal 30 foot CESA in a pool. Students who struggle to do the current 30 foot required pool CESA usually have no trouble with that same distance in the open water. I argue that this training is in some ways detrimental because the 30 foot horizontal exercise gives students the idea that it is much harder than it really is, and I fear that it will make them doubt their ability to do it in the open water and so hold their breath instead in a real emergency.

 

[LeadTurn_SD]

.....I have, in fact, argued about this in the past with the way we teach presently. A CESA from even 30 feet is much easier than a horizontal 30 foot CESA in a pool. Students who struggle to do the current 30 foot required pool CESA usually have no trouble with that same distance in the open water. I argue that this training is in some ways detrimental because the 30 foot horizontal exercise gives students the idea that it is much harder than it really is, and I fear that it will make them doubt their ability to do it in the open water and so hold their breath instead in a real emergency.

Thanks for posting that John.

I think doing "horizontal" or "lateral" practice as CESA training is really deceptive, and gives the wrong idea about what a real CESA feels like. I know from experience I can CESA much further than I can "lateral" on a single breath.

I'm glad your students have an instructor that can bring that point home.

CESA's are surviveable from much deeper than many of us think, and while I sincerely hope one is never necessary for anyone reading this thread, I know that even from the very edge recreational depths most folks have a better than 50/50 chance of "making it" unhurt.

Best wishes.

 

[Thalassamania]

From a physics point of view, the 100 foot CESA in the open water is much, much easier than what you describe in either a pool or a free dive to 50 feet.

The key is the expanding air.

When you are at 100 feet on scuba, you have 4 times as many air molecules in your lungs as you do on the surface. As you ascend, that air expands rapidly and comes bubbling out. In a pool, there is no benefit from expanding air. The same is true of free diving.

I have, in fact, argued about this in the past with the way we teach presently. A CESA from even 30 feet is much easier than a horizontal 30 foot CESA in a pool. Students who struggle to do the current 30 foot required pool CESA usually have no trouble with that same distance in the open water. I argue that this training is in some ways detrimental because the 30 foot horizontal exercise gives students the idea that it is much harder than it really is, and I fear that it will make them doubt their ability to do it in the open water and so hold their breath instead in a real emergency.

I might point out that a 75 foot underwater swim as a watermanship prerequisite for your class sorta renders this entire question mute.

 

[dumpsterDiver]

You will probably get more than that from your tank by inhaling through your regulator as you ascend, and it will be nice, clean air coming through a device designed to give it to you. Remember, your tank is not out of air. It just can't give it to you at your present depth because it has to have more PSI than your ambient pressure. I hope your experiment didn't put too much unpleasant stuff that has been hanging around inside your BCD into your lungs.

This idea has been discussed quite a few times, and I agree with the majority who say there is no point in it when the alternatives (breathing from your tank and CESA) are readily available and easy to do.

If you have ever practiced ascending with a very nearly empty tank, you would probably NOT recommend sucking on the regulator to get the last bit of air. Sucking on a regulator that is delivering just a trickle of air, makes the diver feel air starved, plus if they suck too hard they could mess up the exhaust valve and then they will get water.

If you are comming up on an empty tank it is much, much better to gently press the purge button and passively "drink in" the meager air flow. This is much less stressful and does not have your diaphgram in a spasm as you try to create a deep space-like vacuum in the second stage. You can normally get a number of very slow breaths from an "empty" tank and the cheaper and less well maintained the regulator is, the more air you can slowly milk from the tank before the air stops.

The difference between sucking on a reg in panic versus training yourself to accept a very gentle freeflow/purge sounds inconsequential, but it is not. The key to making an emergency ascent with little air is to minimize physical activity and try to be as calm as possible. Reducing the feeling of air starvation from a low flow rate from the regulator makes a big difference in psychological comfort and I think a lower stress level reduces oxygen consumption. Talk to any freediver who has learned to do a lot with very little air, the two key points are minimal use of oxgen consuming muscles and also mental calmness or psychological control of the situation.

You can simulate the feeling pretty easily in your home. Get one or two straws and try to inhale very fast and forcefully though them getting as much air as fast as possible and then exhale out your mouth. I think most people will find that this desperately hard sucking action makes them feel very uncomfortable in probably less than 2 minutes. Then do the exact same experiment and try to very slowly and gently sip the air through the straws with slow realxed and deep inhalations. The effects of the straws is much less this way and you can do it for a longer time.

 

[stargost]

I have, in fact, argued about this in the past with the way we teach presently. A CESA from even 30 feet is much easier than a horizontal 30 foot CESA in a pool. Students who struggle to do the current 30 foot required pool CESA usually have no trouble with that same distance in the open water. I argue that this training is in some ways detrimental because the 30 foot horizontal exercise gives students the idea that it is much harder than it really is, and I fear that it will make them doubt their ability to do it in the open water and so hold their breath instead in a real emergency.

As I commented, I'm with you with the physics. I guess my point was that if you can do successfully a more difficult exercise in the pool, you'll feel more comfortable at depth that you can actually do this CESA in an emergency.
But I see your point above, and indeed wrong perception would have the opposite effect, + risking the 'holding breath' - which you needed not to do when doing the exercise in the pool (making it really difficult)

thanks for pointing this out!

 

[Belce]

Aren't you supposed to get a near full breath during such an ascent from a reg system? It would also be a bad moment in a diver's career to discover the deficiencies of split fins..:shocked2:.

Inappropriate reply and shows poor knowledge of split fins vs flippers, fins are always better than flippers.

 

[Scott L]

Inappropriate reply and shows poor knowledge of split fins vs flippers, fins are always better than flippers.

Huh? Do you wish to elaborate on your fins vs flippers comparison?