Today's 136ft CESA trial

[DogDiver]

Ya, make sure your life insurance is up to date. When commercial and navy divers encounter problems, there is a chamber on deck that they have only a few seconds to shed their gear and get into.

 

[Johnoly]

....This dive was on air. .....

...Particularly interested if shallow water blackout would be a realistic risk...

Nope because you were consuming some O2 at depth.

In SWB and freediving the majority of O2 consumption is from the kicking down and activity to reach depth in addition to an increased heart rate waiting/working at the bottom for a fish. This is what consumes O2 at/to depth. Coming back up and PPO2 with little or no O2 in the tissues and starving will set off SWB.

By breathing a percentage of O2 at depth, then holding to the surface, you have eliminated the O2 consumption on the way down and thus have plenty of O2 for ascent no matter what (A.G.E., lung embolism, etc aside). But SWB from lack of O2 is not going to be a problem in your exact scenerio.

 

[avatar]

Cameron and Sam, did you have the sensation that you needed to exhale, or did your lungs vent on their own since you kept your airway open ?

Sam, do you know of the deepest accidental CESA ?

 

[Akimbo]

George Bond , USN made a 300 + in the early days

For anyone interested in more information: Then Commander Bond and Chief Tuckfield made a buoyant ascent from 302'/92M in 52 seconds from the USS Archerfish's (SS 311) escape trunk on 2 October 1959.

Commander George Bond (later Captain) and Chief Cyril Tuckfield on the right.​

I feel fortunate to have know Chief Tuckfield, who everyone including the officers called Tuck. I was a 19 year old Third Class Petty Officer fresh out of First Class Diving School when we met. He was running the diving locker on his last tour of duty before retiring from the Navy in the early 1970s. I spent hours prompting him for recollections from his long career that included working on all three SeaLab projects. His modest and quiet demeanor was an inspiration. About all he said about that record setting ascent was "anybody could do it". I guess that was the point they were trying to prove, but impressive nonetheless.

I was 8 years old when they made that buoyant ascent to test emergency escape procedures. Please keep in mind that this is far from a diver making an emergency ascent because they didn't spend enough time under pressure to get bent.

 

[northernone]

Enjoying the historical context. Wow.

Cameron and Sam, did you have the sensation that you needed to exhale, or did your lungs vent on their own since you kept your airway open ?

I don't have a feeling of my lungs being "too full" No pain, no warning. At most there is a small feeling of pressure in my throat.

That said, I make my airways an open loop, head up, with an open throat and mouth, the gas flows out "automatically" as it expands. I'm neither not blowing out to increase the airflow nor locking my throat shut trapping the gas. I hold my body (explanation unclear, I apologize) at a fixed level of relaxation and let the expanding air "overflow" as it wants to as I ascend.

The same technique with a bcd if I'm using one. An air siphon develops, the bcd vent held open at a certain level. Whenever the air expands up to the hole it bubbles out. (Making the bcd function as an open bottom fixed volume lift bag)

In thick thermals I need to adjust the vent position as I near the surface because the more dramatic wetsuit expansion wants to speed my ascent (in the portion of the ascent I want slowest.)

Though my equipment configuration choices and deco obligations have outgrown my expected need for a CESA , I still swim up once annually as personal check in.

Thanks,
Cameron

 

[dmaziuk]

Interesting work. Early on I thought you could only do a CESA from shallower depths. Not figuring in the pressure change that would've allowed you those two big breaths during the ascent. I wonder how deep one could do a CESA by grabbing breaths due to decreasing pressure.

I think in this scenario the breaths are more for venting CO2 and keeping down the urge to breathe. The number I was given back when by a swimming coach is one minute of "stored" oxygen in the tissues and lungs, but here you'll need to add the dissolved oxygen and pressurized gas in the lungs. The pressure can easily triple that "one minute" without the extra breaths.

I strongly suspect sticking to 60 fpm or slower would be the problem if one has to do it for real. 60 fpm times 3 minutes is 180'.

But SWB from lack of O2 is not going to be a problem in your exact scenerio.

I think one of the proposed mechanisms is PPO2 drop in the brain, that could potentially happen if you ascend too far too fast. I.e. without the lack of O2 per se.

 

[Compressor]

Cameron is a dedicated individual as seen from his posts and techniques used in diving.
Sam thanks for your post.

Akimbo: thank you for the always great historical perspective as well.

 

[northernone]

5 months later did it again.

200ft up to 70ft. Modified the practice this time.

Started off with an empty bcd and fairly significantly negative (12lbs negative if I needed to guess). Narced more noticeably in the 180-140 range after the co2 build up from the effort of finning up got me.


Doing it for real I would have ditched 4lbs at least.

Once I hit 140ft it was comfortable again after passing the dark narc depth range. Being in brighter water feels better too.

Maintained a comfortable ascent rate (new slow suggested ascent).

Well. That's that.
Cameron

 

[rjack321]

2. Getting negative as the tank floods with water is another risk a catastrophic failure can cause. The buoyancy shift is dramatic and I haven't heard it addressed.

This doesnt really happen. Take a cylinder with 200psi in it to 100ft, take out a burst disk, the cylinder won't flood. The air will equalize to ambient pressure (4 bar, or 60psi) and that's about it. The opening is too small for the water to substantively exchange with the air inside. If the opening were "large" you would have far more important things to worry about - like where your organs went in the explosion.

 

[northernone]

This doesnt really happen. Take a cylinder with 200psi in it to 100ft, take out a burst disk, the cylinder won't flood. The air will equalize to ambient pressure (4 bar, or 60psi) and that's about it. The opening is too small for the water to substantively exchange with the air inside. If the opening were "large" you would have far more important things to worry about - like where your organs went in the explosion.

Flooded tank, now what?