CESA theory

[dmaziuk]

Thank you very much. But one thing disappointed me. You are one of my heroes in SB. I follow all your posts. I was sure that you were in fact a Tech diver. That I will never be.
I have started free diving training. Went from 30 seconds to 3 minutes but only in static and perfect conditions. I need to practice further.

There is a third point of concern: the "fast" tissues. They're typically kept "in check" by the safe ascent rate which you probably can't be expected to maintain during emergency OOG ascent. 30m isn't difficult with a bit of practice, the difficult part is doing it in 3+ minutes. Hence "better bent than drowned" rule and the reason you don't want to practice CESA from more than 10m (assuming of course you can keep yourself from blowing a lung -- something a random instructor won't necessarily expect from a random OW student).

 

[Blackcrusader]

Umm. Don't do that. The point at which you feel the effect may be beyond the point at which you are capable of removing the bag. Thanks.

You will feel the CO2 buildup effect early on and the urge to breathe. Also a large bag fits loosely enough that it is quickly removed. you seal it using your hands not using duct tape. No one wrote try and keep in place until you blackout. A little commonsense here.

 

[Blackcrusader]

Exactly. I just did a 40 second exhale with no problem. My normal exhale when diving is longer than 15 seconds. I kind of just dribble the air out through the reg. I was a competitive swimmer and trumpet player, both of which require short inhales and relatively long exhales so it's a breathing pattern I'm used to. It also conserves gas.

Yeah I do the same thing and often have 15 - 20 seconds between breaths on a dive. I also wrote I played wind instruments and was used to the long exhales. I see in many photos or videos that people take of my a wispy bubble trail coming out of my regulator or sometimes my mask if I clear that. I played Euphonium and Trombones.

 

[NW Dive Dawg]

So WTF is anyone's issue with diving a back mounted, 100% redundant pony. For us solo hunting folks up here in the PNW...... there are no downsides to having a pony that I can think of....

 

[Blackcrusader]

But I haven’t used GF as I don’t do deco.

GF is also relevant for NDL dives not just for Deco dives. I always check my dive buddies NDL on dives as many people who use Suunto have very conservative NDL times. I have to dive brief them to pay attention to their own NDL times and not just follow me. Some divers have not paid attention and gone into deco on their Suunto, not cleared the deco obligation and then got locked out by their computer. All the while saying my DC isn't working properly after the dive lol. Even if my dive partner is using a shearwater I will ask what GF setting they are using.

Gradient Factors and recreational diving

I am looking at transitioning into a computer that uses Gradient Factors. I have superficially read some data on the theory and have a basic idea of theory. I currently use an Oceanic computer set to DSAT and run it pretty close with EAN. Last week in CZM I did 24 dives (26 hours) with most...

scubaboard.com

 

[Blackcrusader]

I beg to disagree that you should want to do the same.
If you are on single cylinder, unless it’s closed shut or leaking extremely fast, just breathe from it and ascend. That’s a lot less risky than doing a cesa.

Well the tank has plenty of air so it's only a question of how to use that air for yourself. I do not dive with a pony on recreational NDL dives. My first redundancy is sorting myself then after that asking my dive buddy for assistance. Dody really just wants to know the science of the air in his lungs as he ascends how much is there and how will it expand. Some people want to science the hell out of everything whereas I just want to know how to get to the surface alive without all the science.

I just remembered breath hold diving techniques were taught in my BSAC sports diving classes. In novice classes we covered the Human Life Support System and learned about CO2 buildup etc. Training covered Lung Volumes and residual volumes, tidal volumes. Emergency ascents also covered. Maybe I should send Dody a copy of my manuals as it has all the scientific things he would like to read about. It also covers hypoxia anoxia hyperventilation and other things. Also important is both physical and mental fatigue.

It's good for me to go through my manuals and remember where I learned about such things. As I have not dived a lot recently re-reading my dive manuals is a good thing.

 

[Diver With Altitude]

That I don’t want to test because I am afraid. I wanted the to give me comfort or to tell me to forget about it.

Try it from 11m. then try it from 12m. Expand your comfort zone.

I met a Navy physician many years ago who talked about ascending from the deck of a submarine from 200 feet (61 meters) on a single breath of air (I was a kid who had just done a resort course dive and it wasn’t a very technical discussion). He didn’t mention exhaling at the start of the ascent, but then again, he didn’t go into details. He wasn’t a Navy diver, he was the ship’s surgeon and just looked like a regular guy, not some super fit Navy Seal.

 

[Blackcrusader]

So WTF is anyone's issue with diving a back mounted, 100% redundant pony. For us solo hunting folks up here in the PNW...... there are no downsides to having a pony that I can think of....

Better yet have your dive buddy bring a pony bottle.

 

[Searcaigh]

Better yet have your dive buddy bring a pony bottle.

That's not a pony it's a horse

 

[barth]

Thanks for your answer. I may be a lousy diver as some here think but this is a question that has bugged me for weeks. It should not happen if you do everything right but what if it does anyway? I was trying to make a scientific analysis of CESA and I know there are alternatives.

It depends on your choices. If one thing goes wrong you don’t need cesa.

1 Plan your dive and agree with your buddy. If the distance between you and you buddy is to big, get closer to your buddy. Check gas, check where your buddy is. If you don’t like your buddy and/or dive, cancel the dive or go shallower.

2 If you want to do a solodive, use a pony, sidemount or doubles.

3 If you want to do a dive with a unknown buddy and don’t want to cancel a dive if you don’t like and don’t feel safe with that buddy, change plan, dive shallow or use a pony, sidemount or doubles.

4 If you don’t want to bring redundanc and don’t want to cancel a dive, want to go to 30 meter, then there is a very small risk you should use cesa. You should have a failure and that should also be a failure with al gas directly unavailable.

I wouldn’t chose option 4. Because of that the scenario I should use cesa is not realistic for me I think.

For diving I do also plan for failures. But it’s all about risk, how much risk do you think that is acceptable? How much gear do you want to bring and how much time and money do you want to spent at training?

If you think that cesa is a realistic scenario for your dives you could accept it or you could change things to made cesa a not realistic scenario and don’t care about cesa. But if you will be in a scenario were cesa is the only option you should use it and hope you will not get injured.