I'm challenged with: Deep Yoga-Style 'Diaphragm' breathing vs Buoyancy Control.

[Charred]

So I am struggling with this idea that a long exhale leads to CO2 retention. Where is this coming from?

I've always been taught that the exhale, particularly a long slow one, helps reduce the heart rate.

To the OP: When relaxed, my exhale is ~15 seconds with a 5-6-7 sec inhale. I never try to control the inhale - I inhale what I need. The "problem" is that since the cycle is not even, you tend to sink slightly since the exhale is much longer. To balance this, I run myself ever so slightly positive. I target neutral about 3 seconds after the start of exhale.

If you are in a situation where sinking a bit too much is a problem, you simply finish the exhale and inhale.

 

[Coztick]

What's always works for me is to set neutral bouyancy at 1/2 lung capacity once on the bottom.
I spend most of the dive breathing slowly and shallow near this point.
I will breathe deeply but only after a few shallow, slow breathes.
When I do fully inhale or exhale, I do it quickly and then slowly back to center.
This doesn't seam affect my bouyancy much at all.

 

[lowviz]

What's always works for me is to set neutral bouyancy at 1/2 lung capacity once on the bottom. ...//...

I spend most of the dive breathing slowly and shallow near this point.
I will breathe deeply but only after a few shallow, slow breathes. ...

Sounds to me like you are right on the edge of carbon dioxide buildup, thus the periodic need for a deep breath.

...//... When I do fully inhale or exhale, I do it quickly ...

Exhale, no prob. But a sharp inhale is a signal to your bod that something is threatening you. (look up the autonomic/parasympathetic nervous system if you want to go nuts with this like I did in the past.)

To the OP, I thought breathing was some Eastern secret to low gas consumption, but I now believe that efficient dive skills will beat the pants off any form of breath control. Just breathe.

 

[rsingler]

I've held off posting, as most of the suggestions have been on point.

Medically speaking, almost everything has been covered well. But let's look at what the determinants are of minimizing your RMV.

Decreased Exercise/CO2 production - covered
Trim - covered
Dead space ventilation - hinted at, but let's talk about it more.

Your mouth, throat, trachea and brochii play no role in gas exchange. Your second stage adds a touch more dead space that makes it worse.
Now, getting your RMV divided into just two breaths per minute is indeed a very effective way to minimize dead space ventilation, but at already-described costs to buoyancy, especially in confined spaces. And possible CO2 retention has been mentioned several times.
Breathing technique is more important, and shallow breaths with a second stage in your mouth are the wrong approach, because they merely exchange a larger fraction of your breath that is not coming from deep in the alveoli, but rather just exchanging back and forth in the "dead space". Worse, that dead space gas acquires CO2 by diffusion from adjacent molecules and traps oxygen that should be going all the way down to your alveoli.

So, the primary things that matter are to dump as much CO2 as you can by a full exhalation, and minimize the fraction of your breath wasted as dead space (fixed size, maybe 150-250cc) by using a full breath (1000-2000cc), instead of a shallow breath (400-600cc).

Lying here asleep, the average 70kg guy's RMV is about 0.14CFM (4000 cc/min)
Mathematically, if your RMV is an excellent 0.4CFM, you can see already that there's a lot extra going on: exercise/CO2 production and exchanging dead space biggest among them. With that wasted ventilation, it makes sense to do it as little of it as possible. But the difference in dead space ventilation between 4 big breaths/min and 12 somewhat smaller bpm is just not the biggest piece of your RMV.
Exercise production of CO2, and getting rid of it, is bigger. And you can't decrease your RMV by breathing less (CO2 retention).

So my 2 cents?
Go slow, go flat, breathe deeply as often as you need to, and enjoy the dive.

Diving Doc

 

[scrane]

What's always works for me is to set neutral bouyancy at 1/2 lung capacity once on the bottom.
I spend most of the dive breathing slowly and shallow near this point.
I will breathe deeply but only after a few shallow, slow breathes.
When I do fully inhale or exhale, I do it quickly and then slowly back to center.
This doesn't seam affect my bouyancy much at all.

This is exactly what I do. Works for me too. I usually go for that big breath when I need to float over that big coral head looming ahead.

 

[Jack Hammer]

I naturally diaphragm breath, so doing it underwater too comes easy. When you are actually neutral your breathing will not have as big of an affect as you'd imagine. I've seen a lot of people use their breathing to control buoyancy by constantly changing up their inhale and exhale rates and believing this is neutral bouyancy. With actual neutral bouyancy you should just breath naturally. Even maintaining depth in shallow cold water, wearing a drysuit, and with tech gear becomes simple.

 

[scubafanatic]

Who is supposed to be your buddy on this trip? What's your buddy like on air? Is your buddy the female dive op owner?

I think it's great that you're in the pool refreshing your skills before a big trip after too long out of the water.

Really seems like your ex buddy left you feeling inadequate, as you said, lol.

What will be best for you and not holding up the team, will be having a well matched buddy, both in air consumption and experience. From what I understand the crew are all experienced so that shouldn't be a problem.

Have you discussed this concern with any of the crew or just us?

I have no pre planned dive buddy, and sometimes buddies end up being loose associations of assorted groups, not specific buddy pairs. It's rather annoying that some women do scuba 'backwards' though.......they seem to put air into their tanks through the dive, when the whole point is to suck air out of the tank! I haven't troubled the boat crew with any of this drama, I'm not worried about being an underwater disaster or anything, I should at least be able to rank 'midpack' in endurance once I've broken the ice with a few dives. But it would be nice to be able to hang with the cool kids!

 

[scubafanatic]

I was diving in Belize years ago and at 60' I was amazed to see the dive master with just a mask and fins swimming from diver to diver and grabbing their octopus for a couple of breaths and then swimming to the next. I was thinking, gee, this guy is pretty cool, but soon learned he forgot to bring his regulator set on the boat.
The moral of the story is he only hit on the women divers, knowing they'd be the ones with extra air.

The more you think about it the worse it will be. Just have fun.

Hopefully I won't have to resort to trying that!

 

[scubafanatic]

Not sure how this might work for you on your trip. I'm sure every DM/location will vary, but...

On my last vacation to Scuba Club Cozumel, drift diving, after the first couple of days, the DM was obviously satisfied with our skills and experience. Instead of the group ending when the first diver went bingo, he learned/guessed who was next, and shuffled buddies on-the-fly so a pair surfaced while everyone else continued the dive.

I understand that this might not be appropriate for everyone, but our group seemed very competent and able to surface safely without the DM. The dive boat was ALWAYS attentive and nearby for a fast and convenient pickup.

I won't over stress over it, usually folks sort out who reasonably belongs with who, I just don't want to be at the back of the bus, so to speak.

 

[scubafanatic]

So I am struggling with this idea that a long exhale leads to CO2 retention. Where is this coming from?

I've always been taught that the exhale, particularly a long slow one, helps reduce the heart rate.

To the OP: When relaxed, my exhale is ~15 seconds with a 5-6-7 sec inhale. I never try to control the inhale - I inhale what I need. The "problem" is that since the cycle is not even, you tend to sink slightly since the exhale is much longer. To balance this, I run myself ever so slightly positive. I target neutral about 3 seconds after the start of exhale.

If you are in a situation where sinking a bit too much is a problem, you simply finish the exhale and inhale.

My hope is that the deeper I am, the full vs empty lung contrast will be reduced such that I don't have to partially abort my deep breathing technique and spoil the full effect.