Feeling the OOA

A question for those of you who've had an OOA situation:

How long did you need to react? (Were you distracted and on hindsight you think you could have felt the pressure change a little before?)

How much air did you have in you when it happened? (deep inspiration and even some more in the bottle? Or right at the beginning of an inspiration)

How much time can you hold your breath on surface and how much time do you estimate you had after being conscious of the OOA situation?

As the bonus question: Is this the correct forum for this question? Or should it be moved to accidents or somesuch.

The amount of 'warning' you get (in terms of breathing resistance) will vary depending on the type of regulator you are using. Depth can also play a part in the 'suddeness' of OOA.

I can free-dive down and back up to (at the moment) around 24m. That experience gives me some confidence in my ability to perform a CESA from recreational depths up to the surface at a rate of 18mpm.

Proper training with a professional freediving instructor would give you far better capability than that.....and could be a lifesaver some day.

However, the capacity to perform CESA also involves reacting immediately, minimizing exertion and panic.

My only OOA experience was from a blocked first stage, and it wasn't a 100 percent shutoff (I was getting perhaps 20 percent...but believe me, that's NOWHERE near enough!). However, I can remember distinctly exactly what I did. I immediately looked at my gauges to see that I still had over 1500 psi, I switched to my octo and got the same almost-no-air-at-all result, I checked my depth and saw I was at 65 feet, and I vividly remember looking up at the surface and thinking "I BELIEVE I can make that...but I really don't want to have to try." All of this took perhaps 15 sec from the moment I realized I had a problem. Trust me, it doesn't take long to get a lot done when you know it's kinda important.

Thanshin:

How long did you need to react? (Were you distracted and on hindsight you think you could have felt the pressure change a little before?)

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I have run out of air on two occasions ... and both times it was a conscious decision, so reaction was immediate. The first time I was a fairly new diver, and wanted to find out what it would be like. So I did it in a very shallow location, and when I ran out of air, I stood up. The second time was last year in Indonesia, and I decided to stay down till I ran out of air because there was a manta ray in the vicinity I wanted pictures of. I was at about 10 feet taking pictures, and when I took the last breath, I surfaced.

In neither case did I feel any pressure change until I took the last breath.

Thanshin:

How much air did you have in you when it happened? (deep inspiration and even some more in the bottle? Or right at the beginning of an inspiration)

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In both cases, the bottle went dry on a partial inhale ... so my conclusion is that it rarely happens like in practice, where you take a full, deep breath first. That may be a good thing, as less air in your lungs will reduce the risk for an accidental lung injury as you do your CESA.

Thanshin:

How much time can you hold your breath on surface and how much time do you estimate you had after being conscious of the OOA situation?

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The calmer you remain, the more time you'll have. When I did my instructor training, they had us do this skill called "skin, ditch and recover". In a pool and snorkeling gear you had to swim to the bottom, remove your gear, surface briefly, swim back down, put on your gear, and surface clearing mask and snorkel on the way up. The purpose of the exercise wasn't the skill, it was to show you how easy it was to do when you remained calm ... and how difficult it was when you didn't. On the surface, most normal humans can hold their breath for a minute or more. Underwater, and in a stressful situation, you will start to feel discomfort after only a few seconds ... and that will create even more stress, causing the situation to cascade to uncontrollable urges rather quickly.

There is a HUGE difference between doing an OOA skill in practice and experiencing one that isn't planned and expected. Remaining calm is usually the difference between surviving and not.

Thanshin:

As the bonus question: Is this the correct forum for this question? Or should it be moved to accidents or somesuch.

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I think so ... and I think they're good questions ...

DevonDiver:

The amount of 'warning' you get (in terms of breathing resistance) will vary depending on the type of regulator you are using. Depth can also play a part in the 'suddeness' of OOA.

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Ironically, you'll get less warning with a high-performance reg than you will with a low-performance one ... because high-performance regs are designed to continue operating smoothly as the pressure in your cylinder decreases.

... Bob (Grateful Diver)

I've never told this story (too embarrassed I guess, but I'm over that now). It's not exactly what you are asking, but I think it fits.

I did a dive a couple years ago where my mind must have been somewhere else entirely.

Mistake number 1: my manifold was isolated. Either I did it myself, or someone else did it. Point being, I didn't check it.
Mistake number 2: I was diving air in the 100-110 foot range in a cold dark site where I know I've been narced before at 90.
Mistake number 3: Possibly due to narcosis, although I was checking my gas at regular intervals and never saw the number change (hmm), I didn't have the a'ha moment.

So we're diving at about 100 feet. I start to take hard pulls from my regulator (Mk25:S600). I check my SPG: 3500PSI. I think, that's weird. A couple more pulls and it cuts me off. I flash my light and like clockwork my buddy donates his long hose. We turn the dive and start moving (quickly: this is a dive site with a very slight slope, so you gotta move fast unless you want to come up in midwater and end up on the surface in boat traffic).

Things are going through my head like: my gauge must be stuck on full. For whatever reason, it never dawned on me that just maybe I was breathing off 1/2 of my gas, isolated from the other 1/2 which just happened to be connected to the SPG. At about 80 feet, my chin hit the purge valve on my necklaced backup reg. Air came out.

It was like instant clarity. Everything suddenly made sense. I reached back and opened the isolator, and enjoyed the very odd sound of a full tank equalizing pressure with an empty tank. I stopped my buddy, signaled: I am OKAY, purged my primary to show him I had air, and gave him back his hose and ended the dive on mine.

It was certainly a learning experience. I've since become much more diligent about doing flowchecks (i.e. reaching back and manipulating my valves to ensure they're all in the proper position), even in open water with nothing to disturb them.


How long did you need to react?

Not long. My buddy afterwards told me he knew something was wrong from the puzzled look on my face as the breathing resistance increased (i.e. before I was "OOA"). As soon as I flashed the light, I had his reg. Speaks volumes about having a good buddy/team.

How much air did you have in you when it happened?

As in, were my lungs full? No.

After the many great responses I still have in my mind a doubt:

If I find out I'm OOA right at the beginning of an inspiration with the lungs completely empty, I've got 25-30 seconds being somewhat relaxed before my vision turns blurry.

The first time I get into OOA, I'll probably need 2-5 seconds to realise what's happening.

The stress will probably cut my remaining 20-25 seconds to 10-15.

Will I have time in 10-15 seconds to reach my buddy and take his reg?

Intuitivelly, I think I will; but I can't be sure.

That thought, together with the idea that eventually every diver gets an OOA, is pretty scary.

Not scary enough to stop me from entering the diving world, but I hope it's scary enough to make me check the tank thoroughly, every single time.

Thanshin:

After the many great responses I still have in my mind a doubt:

If I find out I'm OOA right at the beginning of an inspiration with the lungs completely empty, I've got 25-30 seconds being somewhat relaxed before my vision turns blurry.

The first time I get into OOA, I'll probably need 2-5 seconds to realise what's happening.

The stress will probably cut my remaining 20-25 seconds to 10-15.

Will I have time in 10-15 seconds to reach my buddy and take his reg?

Intuitivelly, I think I will; but I can't be sure.

That thought, together with the idea that eventually every diver gets an OOA, is pretty scary.

Not scary enough to stop me from entering the diving world, but I hope it's scary enough to make me check the tank thoroughly, every single time.

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So the solution is as follows:

1. Start with a mentality that running out of air is almost always preventable, given appropriate attitude, skills and awareness.
2. Work on developing the skills and awareness in yourself.
3. Be choosy about diving with people who have a similar attitude about the importance of good skills and awareness.
4. Develop good gas management habits, and keep in mind that those habits begin in the planning stages of the dive ... not when you start the dive. And they CERTAINLY don't consist of "end the dive with 500 psi" ... that's not gas management.
5. Practice your skills regularly. Developing confidence in your ability to get yourself out of trouble will not only help you out in a jam ... it'll help you learn how to avoid that jam in the first place.

I think by now you're familiar with my web site ... if not, click the link in my sig line and click the Articles tab. There are a few articles in there that'll give you some helpful info on developing good buddy and gas management skills.

As a last resort, consider carrying a redundant air supply. If you choose to do this, please keep in mind that it is NOT a substitute for good planning and diving skills ... it is insurance to be kept in reserve for those rare moments that exceed your best efforts to plan and execute your dive safely.

... Bob (Grateful Diver)

Given the right team and the right training, your buddy should be there ready to shove a regulator in your mouth in a matter of seconds. Read what Blackwood wrote again....his buddy knew something was wrong long before he gave the OOA signal....his buddy gave him a breathing source and they started making their way in at that time.

I have a couple suggestions for you. The first is to get very good training and find very good buddy teams. Practice situations like this, be ready, and always be aware of what's going on around you (like I mentioned above, Blackwood's buddy knew something was going on before the OOA signal was given....having this kind of buddy awareness goes a long way).

My second suggestion to you is to read NWGratefulDiver's Gas Management / Rock Bottom article. If you were to run out of air, have your buddy donate to you, would you buddy have enough to get both of you to the surface? If you follow the guidelines set out in the article, you will always ensure that you can get your buddy to the surface if an OOA situation occurs (as a bonus, if you follow rock bottom, there is very little chance that you will ever face an OOA situation).

Thanshin, Rather than spending time worrying about what it feels like to be out of air it might make more sense concentrating on prevention. One answer would be to carry a small pony bottle with independent regulator - this would give you time to either reach your buddy or the surface. And it might give you some peace of mind and confidence. The need to actually use this should be nearly negligible with proper gas planning and common sense. The purpose of this redundant gas supply for you is not to extend your dive - it is merely insurance against equipment failure. I have over 1400 dives and have never had to use the pony nor have I ever run out of gas or come anywhere close (have done so on purpose just to see). Depleting gas supply accidentally, by not watching gauges and by not planning properly, is generally considered inexcusable by most divers.

In addition to the good advice you have already received, you should know that when you are out of air at depth, you are not really out of air. There is still air in your tank, but your regulator cannot give you what is left at your depth. If you have to ascend because you were not close enough to a buddy or other alternate air source, your regulator should be able to give you some of the remaining air when you have gone up to a shallower depth. That is one of the reasons you are told to keep your regulator in your mouth during a CESA.