Breathing and buoyancy

[Solly]

Agree more diving will improve performance, however thinking and understanding the mechanism of how things go is a good thing that helps one to respond to any emergency if he knows how things work.

 

[gypsyjim]

This should not be based on huge gasps for air just as it should not be based on you forcing every last ounce of breath from your lungs. .

I hope this was not the image I was giving. Nothing is done in extremes, just small adjustments in patterns have noticable but gradual results.
It all comes with experience, and having fun underwater without over complicating things.

 

[ScubaSteve]

I hope this was not the image I was giving. Nothing is done in extremes, just small adjustments in patterns have noticable but gradual results.
It all comes with experience, and having fun underwater without over complicating things.

NOPE! We are saying the same things. I was just making sure I was clear that breathing normally is where it is at. If a little extra upward is required, breathe deeper, if a little extra downward is needed, exhale more. To maintain neutral, just breathe. That's all

 

[jtpwils]

You're an engineer right? Just guessing as I'm one too so while your question may seem odd to some, it isn't to me. It's just how our brains work and I'm familiar with V=Vo + 1/2 at^2 (LOL) I'm far, far, far from an expert but let me try to explain the same thing the others said above in a way our minds work. This is the way it was explained to me.

Because things take time to happen in water there is a hysteresis between lung volume change and ascent/descent. You can use a lung change like deeper exhale or inhale to make a depth change but when you breath normally you will only "just start" to rise before you begin exhaling and "just start" to sink before inhaling again. Thus your normal breathing may make you go up and down "just a bit" but not really enough to affect your buoyancy. If you try and "breath right" by adjusting your breathing rate and depth you're bound to mess it up and by simply diving more you'll find it just comes naturally. Same thing on land - sit there and think about breathing, it won't take long until you start to feel "weird" or yawn, etc.

 

[captain]

depth will affect your analysis, when you breath near the surface the volume of your lungs are large as there is not a lot of pressure around hence your analysis about breathing and buoyancy is correct, however once you get deeper, your lung volume change with breathing will not have that effect over your buoyancy.
That is why when diving shallow you can dispense with your BCD inflating/deflating action and just use your lung volume to control your depth, however once you get to below 15m (in my case) I have to use the BCD to control my buoyancy.

Incorrect, lung volume does not change with depth. It is possible to use lung volume to control buoyancy at any depth. It was done that way before BC were invented. Naturally if you are wearing a wet suit that compresses and loses buoyancy as you go deeper you will reach a point where lung volume alone will not be enough to provide enough buoyancy to maintain a neutral state.

 

[Solly]

You're an engineer right? Just guessing as I'm one too so while your question may seem odd to some, it isn't to me. It's just how our brains work and I'm familiar with V=Vo + 1/2 at^2 (LOL) I'm far, far, far from an expert but let me try to explain the same thing the others said above in a way our minds work. This is the way it was explained to me.

Because things take time to happen in water there is a hysteresis between lung volume change and ascent/descent. You can use a lung change like deeper exhale or inhale to make a depth change but when you breath normally you will only "just start" to rise before you begin exhaling and "just start" to sink before inhaling again. Thus your normal breathing may make you go up and down "just a bit" but not really enough to affect your buoyancy. If you try and "breath right" by adjusting your breathing rate and depth you're bound to mess it up and by simply diving more you'll find it just comes naturally. Same thing on land - sit there and think about breathing, it won't take long until you start to feel "weird" or yawn, etc.

Am an engineer and this way makes me understand better

Incorrect, lung volume does not change with depth. It is possible to use lung volume to control buoyancy at any depth. It was done that way before BC were invented. Naturally if you are wearing a wet suit that compresses and loses buoyancy as you go deeper you will reach a point where lung volume alone will not be enough to provide enough buoyancy to maintain a neutral state.

this requires a thought, I had the notion it was both issues, losing positive lift from your compressed wetsuit makes you feel more heavy and need more volume to compensate for. On the other hand your lung max volume at surface is not the same max volume at 10m, as pressure increases the volume will tend to decrease, or am I missing something?

 

[Razz]

In normal respiration there is more time spent in exhalation than in inhalation. Of course we can and do change this temporarily to adjust our buoyancy during a dive as we need to. To rise up over a structure and then descend back to the prior level, I may temporarily breathe with relatively more air in the lungs. In doing this, I am consciously making a change. As others have said, at all other times one should just breathe normally.

 

[RJP]

I am sure others will have far better comments than mine.

You're comments are dead on: it ain't that hard unless you overthink it.

 

[Kern]

Am an engineer and this way makes me understand better



this requires a thought, I had the notion it was both issues, losing positive lift from your compressed wetsuit makes you feel more heavy and need more volume to compensate for. On the other hand your lung max volume at surface is not the same max volume at 10m, as pressure increases the volume will tend to decrease, or am I missing something?

It's not a closed system. On SCUBA you're breathing gas at ambient pressure.

 

[it_mike]

On the other hand your lung max volume at surface is not the same max volume at 10m, as pressure increases the volume will tend to decrease, or am I missing something?

You missed the focus of volume in your question. Your lung max volume is consistent. The volume of air that can fit into that space changes with depth due to air density (result of increase in pressure / equalization). Your lung capacity did not change, the air pressure in your lungs changes to equalize to off-set the water pressure at depth.

Mike