Question Practicing Out Of Air ascent: good idea, or bad idea ?

[John C. Ratliff]

The weight belt should not be dropped in a controlled emergency swimming ascent. If your BCD is working and expanding as you ascent, there is no need for it, and there is no need for the resulting out of control speed. From the depths you are talking about, a CESA can be done easily.

Weight belts are dropped at really serious depths or if you are in some doubt about your ability to swim to the surface, perhaps because of injury or illness (like feeling you've had a heart attack).

When I passed my instructor exam, we were specifically told by the examiner that even though the language of the CESA calling for a "normal ascent rate" suggests no more than 60 FPM, in a real situation, an OOA diver is likely to go faster than that, and that is OK. We were told not to be too anal about that ascent rate. (If I were practicing this on my own, I would not do it too fast.)

The biggest danger is holding your breath. You MUST exhale all the way to the surface. People who are concerned about their ability to exhale all the way, especially if they have just exhaled, should understand that for submarine escapes, the Navy teaches to exhale fully before beginning the ascent, and then continue to exhale the expanding air as you go. This has been done from 300 feet.

I never practice this because it is so easy. Just remember to exhale while you ascend.

The U.S. Navy, at least in 1967 when I went through the U.S. Naval School for Underwater Swimmers at Key West, taught this, but for buoyant ascents. These were simulated submarine escapes.

I have simulated a CESA from 75 feet by starting in the deep end of the pool (16 feet, as it was a platform diving pool) and swimming horizontally. It works, and even from 16 feet there is some expansion during this ascent.

I’ve also had an occasion in 1975 during a series of working dives, to actually get OOA, and stayed down buddy breathing to get a few more photos and use up the last of the 36 frames (Nikonos II film camera), then do an CESA to the boat from about 35 feet in Yaquina Bay. It was not a problem.

SeaRat

 

[John C. Ratliff]

Being comfortable with a regulator out of your mouth (or one that is not functioning) is going to be a benefit to the diver should an emergency occur which brings about this condition. A person who is an accomplished freediver and who had quite literally swam 100 feet with no air supply THOUSANDS of times and has learned to be completely comfortable doing that, is most likely going to be calmer when this sort of situation occurs.

The amount (rate really) of oxygen consumption is going to be dependent on exertion level, physical condition, acclimation to exertion with high carbon dioxide loads, ability to stay calm and NOT overexert themselves and swim efficiently. These are ALL traits that are essential for a freediver. If these traits/skills are well developed, it is hard for me to imagine why they would not be advantageous in a OOA emergency, all things being equal.

The problem here is that the free diver may neglect to exhale. If doing a CESA from 99 feet, you have the equivalent of four lungs full of air. Swimming while breath holding 100 feet is not the same, as the expanding air will give the ascending diver more than enough air to reach the surface from 99 feet of depth (4 atmospheres equivalent).

SeaRat

 

[John C. Ratliff]

Your assumption is that people who smoke have better SAC rates because they smoke, something that flies in the face of the obvious damage being done to the lungs. I have doubted that it is true and said that these people could have had even better SAC rates if they had not smoked.

You are the one asserting a positive assertion, and I am doubting it. I am the one saying there is no proof of your positive assertion. In terms of logic, the burden of proof is on you. It is up to you to provide proof that smokers have better SAC rates to begin with. Since I am essentially saying that there is no proof to support your claim, I cannot provide evidence that there is no evidence. That would not be possible.

I’d like to chime in here about smoking. My Mom died of lung cancer and emphysema from smoking. It takes years to get the cumulative damage, but smoking does damage all the time. The other things is that, as an industrial hygienist, I understand the physiology of carbon monoxide (CO), and the poisoning of the blood stream it causes. CO adheres preferentially to the red blood cells, and displaces oxygen. So any smoking before a dive will load the divers blood with CO. How much will determine the amount of deficit he/she experiences in the water. But you don’t want any CO in the blood stream before diving, period. There are both short-term and long-term damages that occur because of smoking.

@VikingDives: I’m happy that you stopped smoking, but your statement about not experiencing any increase is because the short-term detriments were insufficient to see them. Long term, you’ve done yourself a favor, and perhaps increased your lifespan.

SeaRat

 

[johndiver999]

The problem here is that the free diver may neglect to exhale. If doing a CESA from 99 feet, you have the equivalent of four lungs full of air. Swimming while breath holding 100 feet is not the same, as the expanding air will give the ascending diver more than enough air to reach the surface from 99 feet of depth (4 atmospheres equivalent).

SeaRat

I don't know exactly where "you see a problem", but my statement (opinion) that it is quite likely that a decent freediver will be MORE comfortable swimming up from 50 than other people who have never freedived, even once to 50 feet is not something I would change my mind about. Certainly (being a freediver) does not ensure that a person will not "get stupid" and hold their breath on ascent. The key is to stay calm and be relaxed as possible on a CESA - and be mentally and physically prepared to ditch ballast should that be needed.

However, this nearly incessant insistence that it is easy to swim up from considerable depth with no air supply is tiresome, especially when the same people making the claim have never done it, or even practiced it, not even once from comparable depths.

The whole situation and the urgency and difficulty of an emergency ascent is hugely dependent upon how rested the diver is when the emergency occurs. If it starts when they are completed winded and out of breath, it is much harder and they might well NOT make it- assuming the tank really does not give them any more air.

The state of the divers buoyancy at the time of the emergency is also critical as well. If they are heavy and have no way to add air to the BC, it is much harder to swim up - this should be obvious, but apparently some people ignore or don't understand it.

Also terribly important is if the diver begins the ascent with full or empty lungs. Don't believe me, try walking casually up the steps without inhaling on empty lungs - see how easy it is or how far you get before panic sets in. I used to practice this daily, just to remind myself how bad it feels and how weak I am.

I had a buddy this week do a CESA from 120 + while solo and he says he barely made it. Judging by the way he looked when I got the boat to him, I have no reason to doubt his self assessment; plus he said he had just barely enough air to suck a little all the way up. It was not a complete loss of air.

This incident (and other things) I have witnessed and experienced, leads me to be extremely skeptical of the assurances "that the expanding air will make everything alright".

Sorry for the rant, but the close call with death yesterday still kinda bugs me.

 

[boulderjohn]

Also terribly important is if the diver begins the ascent with full or empty lungs. Don't believe me, try walking casually up the steps without inhaling on empty lungs - see how easy it is or how far you get before panic sets in. I used to practice this daily, just to remind myself how bad it feels and how weak I am.

The US Navy teaches divers to exhale completely and then begin the ascent, still exhaling all the way.

Your reply indicates that you won't believe it, but there is a difference between ascending in water with lungs filled with pressurized air that is rapidly expanding and walking casually up a flight of steps with a normal breath.

 

[Beau Holden]

Practicing CESA...bad idea. Practicing not running out of gas...good idea. No excuse for running out of gas. When learning to fly, it was said the two worst things were "gas you wish you had in your tanks and altitude you wish you had above you" same in diving " gas your wish you had in your tanks and surface you wished you had above you"

 

[TMHeimer]

Practicing CESA...bad idea. Practicing not running out of gas...good idea. No excuse for running out of gas. When learning to fly, it was said the two worst things were "gas you wish you had in your tanks and altitude you wish you had above you" same in diving " gas your wish you had in your tanks and surface you wished you had above you"

Then you are in the camp of eliminate CESA being taught I assume.

 

[TMHeimer]

The problem here is that the free diver may neglect to exhale. If doing a CESA from 99 feet, you have the equivalent of four lungs full of air. Swimming while breath holding 100 feet is not the same, as the expanding air will give the ascending diver more than enough air to reach the surface from 99 feet of depth (4 atmospheres equivalent).

SeaRat

You only have the equivalent of 4 lungs full of air at 99 feet if you start up will lungs full. I practice CESA from 30 feet starting with half empty lungs, figuring if I ever had to do it that might be what I can get into my lungs after whatever accident happened at depth.

 

[Tom_Ivan]

Bad idea I think.

The risks (gas embolism) outweighs the potential benefit (Not panicking when OOA).

Better to spend you time on other measures;
-Get a pony bottle and learn how to use it.
-Get a Y valve and learn how to use it.
-Take a freediving course. Not to teach any sort of CESA technique but simply to train your brain to recognize that the urge to breath is a CO2 buildup not a lack of O2. Will help with not panicking if an OOA happened.

 

[John C. Ratliff]

You only have the equivalent of 4 lungs full of air at 99 feet if you start up will lungs full. I practice CESA from 30 feet starting with half empty lungs, figuring if I ever had to do it that might be what I can get into my lungs after whatever accident happened at depth.

Remember above where I wrote:

I have simulated a CESA from 75 feet by starting in the deep end of the pool (16 feet, as it was a platform diving pool) and swimming horizontally. It works, and even from 16 feet there is some expansion during this ascent.

I simulated that ascent after doffing my scuba in the deep end, turning off the air, and exhaling. I was able to make it 75 feet from 16 feet deep of water. I did also exhale toward the end.

@johndiver999 I understand your objections and concerns, but there is the fact of physics, and even without a full lung full of air, there will be expansion. There is what is known as “residual volume” in the lungs even on an exhalation. There is always air in the lungs that you cannot exhale. That air will expand as the ascent happens. The air left in the lungs is between 1 and 2.5 liters of air. From 99 feet, that will expand four times, which means that 1 liter will become 4 liters, and 2.5 liters will become 10 liters. That is enough to get a person to the surface. You say you,

However, this nearly incessant insistence that it is easy to swim up from considerable depth with no air supply is tiresome, especially when the same people making the claim have never done it, or even practiced it, not even once from comparable depths.

Oh, but I have done it, in the U.S. Navy School for Underwater Swimmers in 1967 at Key West, and actually through my LA County scuba course in 1963, where we did a controlled emergency swimming ascent (CESA) from beneath the Yaquina Bay Bridge, Oregon at about 35 feet depth.

If I can easily swim 75 feet on an exhalation from a depth of 16 feet, it should be fairly easy for a diver to swim up from 75 feet as that person will have much more expansion than I experienced. Now, that doesn’t mean that someone experiencing that swim will do it relaxed, and that it would be “easy.” But it does mean that the person, if no where near the no-decompression limits (NDL) will most probably survive. Now, this does assume the person is neutral in the water, and not unduly exerting.

For those of you who have never read J.Y. Cousteau's The Silent World, here is a short exerpt, talking about how Frédérick Dumas taught scuba to French Navy divers in the early 1950s.

...At the end of the course the honor students swim down to a hundred feet, remove all equipment and return to the surface naked. The baccalaureate is an enjoyable rite. As they soar with their original lungful, the air expands progressively in the journey through lessening pressures, issuing a continuous stream of bubbles from puckered lips...

Cousteau, J.Y., with Frédéric Dumas, The Silent World, Harper & Brothers Publishers, New York, Copyright 1953, page 180.

SeaRat