CESA from 40ft

[ccx2]

I'm the last person to be handing out advice on this, but during our pool dives the instructor closed our tank valves so we can feel what it feels like when you run out of air fairly suddenly. You can actually feel it coming for a breath or two. That said, I'm sure there are situations where you won't even have the luxury of a breath or two and at 80" down, that's going to suck.

We practiced with the tank shut off also,and I realize that in most cases you would have a warning,so even if you did get a lung full at depth,let's say 60', would it expand enough you could exhale the whole way to the surface at a normal accent rate without convulsing and clawing ,rocketing for the surface?

 

[ccx2]

I'm the last person to be handing out advice on this, but during our pool dives the instructor closed our tank valves so we can feel what it feels like when you run out of air fairly suddenly. You can actually feel it coming for a breath or two. That said, I'm sure there are situations where you won't even have the luxury of a breath or two and at 80" down, that's going to suck.

We practiced with the tank shut off also,and I realize that in most cases you would have a warning,so even if you did get a lung full at depth,let's say 60', would it expand enough you could exhale the whole way to the surface at a normal accent rate without convulsing and clawing ,rocketing for the surface?

 

[Moerby]

We practiced with the tank shut off also,and I realize that in most cases you would have a warning,so even if you did get a lung full at depth,let's say 60', would it expand enough you could exhale the whole way to the surface at a normal accent rate without convulsing and clawing ,rocketing for the surface?

That's a good question. Just trying it here at my desk while timing myself I suspect yes since I can keep going (saying ahhhh) for around 60 seconds with a full set of lungs which should be enough time considering you also you have a few seconds after fully exhaling all the air from your lungs before you will pass out. But add in water pressure and panic and I'm guessing it's going to be less in a real OOA emergency.

 

[Moerby]

We practiced with the tank shut off also,and I realize that in most cases you would have a warning,so even if you did get a lung full at depth,let's say 60', would it expand enough you could exhale the whole way to the surface at a normal accent rate without convulsing and clawing ,rocketing for the surface?

BTW, this is one of the reasons I'd love to try this sometime when I'm with experienced divers - it will give me a good idea of what my limits are as well.

 

[ccx2]

OK, so at 60'you try it ,you ufcourse still have the reg in your mouth ,can't exhale anymore so you start sucking on your regulator, convulsing, and say your still 20' from the surface ,wouldn't getting rid of nitrogen be the last of your worries? I think one would want to be getting to the surface as quickly as possible with the feeling of a blackout coming and would not be able to slow your accent?

 

[Akimbo]

There is actually a fairly long period between the feeling that you are blacking out and when you actually black out. It is also not difficult to control what feels like an impending convulsion, which passes. It is an interesting phenomenon many freedivers discover. The key is experiencing it in controlled conditions so that overwhelming urge to breath induced by carbon dioxide does not evolve into panic when it is not an exercise.

A related conversation that you might find interesting started on this subject started at:
http://www.scubaboard.com/forums/ad...ck-oxygen-during-free-ascent.html#post5919680

 

[Moerby]

There is actually a fairly long period between the feeling that you are blacking out and when you actually black out. It is also not difficult to control what feels like an impending convulsion, which passes. It is an interesting phenomenon many freedivers discover. The key is experiencing it in controlled conditions so that overwhelming urge to breath induced by carbon dioxide does not evolve into panic when it is not an exercise.

A related conversation that you might find interesting started on this subject started at:
http://www.scubaboard.com/forums/ad...ck-oxygen-during-free-ascent.html#post5919680

Very informative thread, thank you. This is exactly the kind of info I need to put my mind at ease.

 

[boulderjohn]

OK, so at 60'you try it ,you ufcourse still have the reg in your mouth ,can't exhale anymore so you start sucking on your regulator, convulsing, and say your still 20' from the surface ,wouldn't getting rid of nitrogen be the last of your worries? I think one would want to be getting to the surface as quickly as possible with the feeling of a blackout coming and would not be able to slow your accent?

1. Understand first that your tank is not out of air. It must deliver air at a greater pressure than you are under at that depth. As it approaches that level, breathing gets difficult, so you have a warning.

2. As you ascend, the air in your lungs expands, so as you exhale slowly you can keep doing it for much, much longer than you can hold your breath when not ascending. Unless you forcefully exhale, you should make it to the surface from almost any depth at a decent ascent speed.

3. You will not go into convulsions under any circumstances unless you have a seizure for an unrelated reason. You may feel a panicky urge to breathe if you exhale too much.

4. If you feel an urge to breathe, then inhale. What will happen? You will get a breath of air, because you are now shallower than you were before and your regulator can deliver air at that reduced ambient pressure.

5. Your blood has enough O2 in it to keep you conscious for about a minute to a minute and a half, so even if you had absolutely nothing to start with you should make it to the surface.

 

[dumpsterDiver]

1.

3. You will not go into convulsions under any circumstances unless you have a seizure for an unrelated reason. You may feel a panicky urge to breathe if you exhale too much.
.

How ridiculous! Not under any circumstances???? What if it is the typical over weight, out of shape American scuba diver whose heart is absolutely pounding and they have been struggling at depth BEFORE starting the CESA.......

How long can you stop breathing for in the middle of a jog?


I can do 20 seconds, but I loose color vision and I am dizzy and the legs become very weak. Serioulsy, what can you do?

 

[flots am]

I will be definitely be diving with a group the first several dives, but I know where you're coming from though.

WIthout trying to sound alarmist, I probably will anyway.

Humans are hard-wired to perceive safety in numbers, however underwater, numbers aren't good for anything except confusion and a false sense of security.

Each SCUBA diver needs an actual, well-trained, individual buddy to rely on for things like sharing air and dealing with problems. This only works when someone specific is responsible for you and you're responsible for them. When mob-diving, you don't have 8 buddies, you have no buddies. You can't rely on some random stranger 100' away if you're having problems, and you certainly can't rely on the divemaster who may not even be able to see the back of his group.

If you're not diving with a specific buddy, you're dving solo (which isn't actually a problem if you're trained and prepared for it).

While it's OK to dive with others, you need to also have a specific, well trained buddy. If, not, you really don't have anything.

flots.