Buoyancy during inhalation

[The Chairman]

This thread may help

Master Neutral Buoyancy: The Importance of Horizontal Trim (Simple Vector Physics)

Who hasn't admired those effortless divers. They're in perfect control and seem to use no energy during their dives, adjusting their depths magically, never creating a silt out, never scull and their air seems to last forever! Some say, this takes at least a hundred dives, but I've got a few...

scubaboard.com

Hmmmnnnn, I resemble that. Thanks for posting the link.

Please don't skip breathe. That will cause you to need to breathe more.

 

[Rilelen]

I think this is implicit in most people's answers, but breath control is part of good buoyancy skills when diving open circuit. It's not a bad thing that you go up when you inhale, and go down when you exhale - many of us use this to actively control our buoyancy during the dive without relying overly much on the inflator/dump valves.

That does make it tricky to transition to a rebreather when you're accustomed to controlling your buoyancy with your breath, but it conversely also means that it's entirely possible and doable to control your buoyancy with your breath.

When you breathe in, you expand the air in your lungs - it's like your body is a balloon, and you are filling it up with air. When you exhale, you release this air, and your body "deflates" (and sinks a little). You can control your buoyancy by taking advantage of this, and inhaling deeply to move "up" in the water column, and exhaling deeply to drop down.

You can also maintain a level buoyancy using long slow inhales and exhales - this is hard to describe but easy to practice. Grab your gear and go find a nice training spot in relatively shallow water - head down to twenty feet, find a reference point, and try to stay there without moving too far up or down in the water column. You'll probably bounce up and down a bit at first, experiment and play around with your breathing - long slow inhale, pause, long slow exhale - until you're staying more or less level. It takes time and practice to learn to calibrate your breathing, and even longer to make it second nature, but you can def do it!

 

[justinthedeeps]

Try to breathe more shallowly. It’s difficult because you feel like you’re not getting enough air. Sip the air, gently let it out.

I caution against this. An easy to get CO2 retention and post-dive headaches. Ask me how I know!
Especially when moving around.

A deeper breath with a pause after inspiration is the most efficient for gas exchange and may improve your RMV.

Can we get a respiratory physiologist to comment?

Holding at the top of the breath seems a common habit in open circuit divers for a few reasons, but I'm not sure if it because that is ideal for gas exchange. We have a tendency towards fuller lungs underwater by instinct (from swimming etc). There is also a small positive pressure on open circuit regulators. They breathe for you, making the full lungs 'pause' seem natural.

Hop onto a CCR at ambient pressure, and the 'deep then pause' thing completely goes away (unless it's a chestmount unit, perhaps). The breathing is far more natural (or should be, with a proper unit and trim)

Dynamic flow and the expansion and contraction of alveoli is important for gas exchange. Pausing/holding is doing neither. Static diffusion is not sufficient or optimal. Fully exhaling is important too.

You may indeed consume less gas by introducing pauses at various stages of the breathing cycle, but I don't think it is improving gas exchange. CO2 issues once again.



The SCUBA tank breathing guru mantras get silly! No matter how practiced, there is nothing much natural about being a human squeaktoy on a compressed cylinder of gases at pressures far exceeding anything our bodies were made for. It totally works out, but let's not get too philosophical!

 

[clownfishsydney]

When I learnt to dive 36 years ago, using your breathing to change your depth was taught to me. It has become natural to breathe in deeply if wanting to go over a boulder. I have never noticed it being a problem when doing decompression or safety stops.