Buoyant ascents

[Iralub]

The thread about amount of air you should come up with had got me thinking about the padi guidance that if you are ooa at a depth greater than 18m you should ditch weight and do a buoyant ascent.

My question is, should you actually do that or should you do a cesa, not releasing weight until you get to the surface?

Assuming you are neutrally buoyant at 18m or more and wearing some sort of thermal protection, chances are you'll have a bit of air in your bc and as soon as you start kicking up, you'll be positive and become increasingly more positive as you ascend. If you have ditched weight, it will be next to impossible to have any control underwater and, I assume, more difficult to control the speed of your ascent.

Is ditching weights really the safest course? I know that bends are usually fixable, while drowning isn't, but an embolism may not be fixable either.

By the way, I know that the first answer is "watch your air and don't go ooa". The second answer is, "stick close to your buddy, so if you are ooa, you have a source of air". I do both of those things religiously, but let's assume you have an equipment failure and your instabuddy is an idiot who can't execute an air share (I know 2 people that this happened to, one did a buoyant ascent from 18m, one did a cesa from close to 50m, both were fine, although the former gave up diving).

Please just humour me with your opinion on the best approach

 

[CuracaoJ]

Assuming I'm deep, have no buddy, no alternate air source and am ooa (something I can't fathom but will for the sake of your question). You would have two options. Keep your weights and do a Cesa using your wing or bcd as a rebreather for a few breaths (likely to result in a possibly leathal lung infection), or, ditch weight. A shockingly huge percentage of scuba accidents resulting in death involve people with their weights still on. This would suggest ditch weights.

 

[ontdiver]

"...if you are ooa at a depth greater than 18m..." is a bit open ended in terms of a "ditch weight or cesa" discussion. The thought of coming up from 30m like a cork is a bit off-putting. I'll take my chances on a cesa....and ditch at the surface.

 

[Macan]

Given your scenario:

1. Sart CESA.
2. Right hand on weight belt poised to release.
3. Left hand on inflator raised ready to dump air to control ascent.
4. When surface is reached, dump weights and orally inflate BCD.

5. If surface is still a long way off, ascent is slow, and no more breath, try breathing from reg.
6. If still no air from reg, no more breath, ascent is slow, and surface is still ways off, dump weights.
7. Continue emit ahhh or eeee sound. Any remaining air in your lungs will continue to expand as you ascend.

No matter what, never remove reg throughout the UW ordeal and dump weights upon reaching surface (this is why PADI has now included emergency weight release in the new OW curriculum).

The decreasing ambient pressure will likely permit the higher pressure from your tank/reg to deliver a breath or two as you ascend.

 

[The Chairman]

Please just humour me with your opinion on the best approach

The best approach is to not run out of air or buddy and certainly not both at the same time!

When I first started diving back in 1969, I did not own an SPG. Instead, I relied on the then, ubiquitous J-valve. My J-valve's detente did not work very well, so I often had to do a CESA. Since I was very neutrally weighted (no BC), I simply did a CESA without ever a thought to dropping weights. But that's the point: I was neutral on the bottom, which made me progressively buoyant as I surfaced. None of how to do a CESA was taught to me when I first learned to Scuba. Kicking like mad to the surface was a pretty natural solution when I was out of air. No, neither my buddy or I had an 'octo' either, so when you were out you simply scrambled to the surface. It's really not that hard.

Then I started using an SPG. Thousands of dives later with an SPG, and I have yet to run out of gas. Moreover, my buddies have yet to run out of gas since I'm responsible for their air too. My preference, and my decision is to simply never to run out of gas or buddy. It's worked well so far!

 

[CuzzA]

Hand on the weight belt buckle on the way up definitely seems like the best thing to do, but for the sake of this conversation, if you've just perfmormed a CESA and orally inflated your BCD what benefit is there to ditching weights once you're at the surface? Also, once on the surface I would assume due to the expansion of gas in your tank you would probably be able to power inflate your BCD, right?

I know weights aren't worth your life, but I would think the first thing to do once you're on the surface is inflate your BCD. If for whatever reason you had a snag removing your weights or it got caught on something, even for just a second, that could change the outcome of the event. Whereas as soon as you take that first big breath on the surface you dump it into the BCD then at least you've removed the possibility of re-submerging and potentially aspirating water.

Thoughts?

 

[Iralub]

The best approach is to not run out of air or buddy and certainly not both at the same time!

When I first started diving back in 1969, I did not own an SPG. Instead, I relied on the then, ubiquitous J-valve. My J-valve's detente did not work very well, so I often had to do a CESA. Since I was very neutrally weighted (no BC), I simply did a CESA without ever a thought to dropping weights. But that's the point: I was neutral on the bottom, which made me progressively buoyant as I surfaced. None of how to do a CESA was taught to me when I first learned to Scuba. Kicking like mad to the surface was a pretty natural solution when I was out of air. No, neither my buddy or I had an 'octo' either, so when you were out you simply scrambled to the surface. It's really not that hard.

Then I started using an SPG. Thousands of dives later with an SPG, and I have yet to run out of gas. Moreover, my buddies have yet to run out of gas since I'm responsible for their air too. My preference, and my decision is to simply never to run out of gas or buddy. It's worked well so far!

Geez, I can't imagine diving without an spg, I check mine every 5-10 min, more often if I'm deep! Guess we have it easy now.

As a general rule, if I'm diving with a group, I'll be the last person to be low on air, even if I'm on a slightly smaller tank (there had been two exceptions) and am religious about checking air. I'm not really worried about inadvertent ooa, but guess equipment failure can happen?

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[Macan]

Hand on the weight belt buckle on the way up definitely seems like the best thing to do, but for the sake of this conversation, if you've just perfmormed a CESA and orally inflated your BCD what benefit is there to ditching weights once you're at the surface? Also, once on the surface I would assume due to the expansion of gas in your tank you would probably be able to power inflate your BCD, right?

I know weights aren't worth your life, but I would think the first thing to do once you're on the surface is inflate your BCD. If for whatever reason you had a snag removing your weights or it got caught on something, even for just a second, that could change the outcome of the event. Whereas as soon as you take that first big breath on the surface you dump it into the BCD then at least you've removed the possibility of re-submerging and potentially aspirating water.

Thoughts?

The scenario given by the OP is OOA at 18 meters. A CESA from that depth or deeper, upon reaching the surface will leave an inexperienced diver completely spent, gasping for air, threading madly, possibly still no air to inflate BCD, need to orally inflate BCD, etc. Task loading at that critical moment can be fatal.

Establishing positive Buoyancy is the most critical task upon surfacing. A well trained diver will instinctively act and Drop the weights upon reaching the surface in that situation.

 

[tbone1004]

Cuzza, your tank is a rigid vessel, no pressure change will alter the contents of the tank. That said you should never practice power inflating your BC at the surface, both a waste of gas and potentially inhibits your muscle memory for an incident like this. You'll likely get an extra breath coming up from depth due to the release of pressure from the hoses, but that's about it.

Now, here is why I think ditching weights at depth is idiotic if you're just out of air. If you have air in your BC, which you do because you're diving in a wetsuit and it has to compensate for the loss of buoyancy while at depth, you start your ascent and now you have an increasing volume of gas in your BC which will require venting to maintain a steady ascent rate, compounded with the increase in buoyancy of the exposure protection. This all adds up to, unless your BCD also failed, you should only have to give 1-2 kick cycles to start your ascent, and you should be able to make it all the way up and have to flare out/vent your bc to slow your ascent for the last 30ft. Will it suck? Absolutely, but it's better than shooting to the surface like a rocket. All you need to do is initiate the ascent and both of these things will work with you to help get you back to the surface. This is why I don't advocate diving thick wetsuits *any farmer john/semidry* below about 80ft because in a wing failure, they are liable to lose more buoyancy than you can kick up at the surface, which requires dropping weights, which is a scary situation to be in especially if you are pushing NDL's on a computer, at which time you'll have quite high tissue loading which can put you at risk of a DCS incident, but more pressing is the increased risk of embolism when making a rapid ascent from that deep. Remember that people have died from AGE's in 1m of water due to lung overexpansion....

 

[M-diver]

While I agree that gas management and awareness during the dive are key to safe practice of the sport, the question posed by the OP is still relevant. OOA can happen and not due to neglecting monitoring your SPG. Last year I was on a dive with my son when I saw him switching to his pony at about 60ft. When I got closer I was able to read his SPG on his hip D-ring and it showed 1100 psi left. I assumed he was practicing but when I got on board it turned out that all his low pressure ports shut off, primary, secondary, BC inflator and drysuit inflator. HP port was working though. Later, during one of the dive shows I ran into a technician from the reg manufacturer and as we discussed this he told me that based on this case they had to change the servicing kits as some teks will confuse and perform incorrect service. Anyhow, OOA can happen and buddy is not always the option for variety of reasons (think insta buddy as one of examples). It is good to discuss the question since if one finds himself/herself in this situation at least some idea on the proper reaction already exists and that's the best value of this board


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