Breath holding?

[RainPilot]

Did I say something funny?

 

[JamesBon92007]

Did I say something funny?

I thought it was funny. You said you hold your breath when you take your regulator out of your mouth.

 

[Vicko]

Yes you're right of course. I don't think that breathing compressed air would make any difference. I recall reading about it once--that you'd have to go to extreme depths to be subject to lung squeeze. Wonder why that is--If going up only a little (particularly close to the surface) can cause a rip in lungs, why would you have to go to like 700' or something for them to collapse? Doesn't air contract at the same rate that it expands? Can't recall the reason.

It's called blood shift effect, the blood saturates your lungs after they compress to a certain point

 

[RainPilot]

I thought it was funny. You said you hold your breath when you take your regulator out of your mouth.

No, I stop breathing at the neutral point and remain there. If I need to, I might blow a bubble or two if I find I am ascending.

This is a video of me doing my first "Basic 6" demo for my IDC. Note the (mostly) lack of bubbles when the reg is out of my mouth. At the 0:38 mark you see me pointing to my lips and giving a "no" sign. This is to point out that I am NOT blowing bubbles while the reg is out.


And yes, I know I'm sculling way too much, bane of my existence. I am a work in progress in all things...

 

[crookshanky]

...Is holding a medium breath while maintaining depth for a minute or so in order to position and frame a shot more common then I'd expect? Beyond breaking the #1 rule of diving are there other disadvantages you've encountered?..

The two concerns I would have during the breath hold are ascending and the build up of CO2. I would ensure I was neutral to start and that I stayed at depth (ascending even a few meters during a breath hold may cause lung injury). A short period of hyperventilation afterwards might help eliminate the build up of CO2.

Yes you're right of course. I don't think that breathing compressed air would make any difference. I recall reading about it once--that you'd have to go to extreme depths to be subject to lung squeeze. Wonder why that is--If going up only a little (particularly close to the surface) can cause a rip in lungs, why would you have to go to like 700' or something for them to collapse? Doesn't air contract at the same rate that it expands? Can't recall the reason.

Earlier speculation on depth limits for freediving were based on ratios of total lung capacity to residual volume (lung volume after exhalation) but has since been proven incorrect. As @Vicko mentioned, blood shift, among other effects, prevent lung damage during deep breath hold dives. On the other hand, as you ascend, while holding your breath, the gas in your lungs expands and can cause barotrauma (metistinal emphysema, pneumothorax, aertial gas embolism, etc.). The body has no mechanism to prevent the over expansion of the lungs. From my understanding, just a few meters is enough to cause injury. And you are correct, gas compresses and expands the same volume amount for a given change in pressure.

The problem comes from rapid expansion of lungs after you take a breath from your reg, just a few meters won't matter, but when you do it after 10 m or so you have a serious chance of massive barotrauma, this is why freedivers need to be taken to the surface after they have a deep blackout...

If you hold your breath and descend, the pressure in your lungs will be the same as the ambient pressure. Talking a breath from your reg that is supplying gas at ambient pressure would not cause your lungs to rapidly expand.

Freedivers that blackout at depth need to be taken to the surface because they need oxygen.

 

[Vicko]

If you hold your breath and descend, the pressure in your lungs will be the same as the ambient pressure. Talking a breath from your reg that is supplying gas at ambient pressure would not cause your lungs to rapidly expand.

Freedivers that blackout at depth need to be taken to the surface because they need oxygen.

It's not about the pressure it's about lung volume at depth. Because of the blood saturation of the alveoli a full breath of air can seriously bruise them. Few cases occur when people dive 16%oxygen mixes, to avoid travel gass they dive down on air to 15 meters and start breathing from their regs and after the dive realize they have a bit off blood in their spit.

If you could do it safely freedivers in trouble could get help from support divers under the surface.

 

[crookshanky]

It's not about the pressure it's about lung volume at depth. Because of the blood saturation of the alveoli a full breath of air can seriously bruise them..

Interesting. I had not thought of that. I suppose the reversal of pulmonary engorgement and reduction of thoracic blood volume may have to be done relatively slowly in order to avoid damage to the alveoli. Do you know of any research articles or case studies on this topic?

...Few cases occur when people dive 16%oxygen mixes, to avoid travel gass they dive down on air to 15 meters and start breathing from their regs and after the dive realize they have a bit off blood in their spit...

Breath holding, and subsequent accumulation of CO2, during any point in a technical dive seems quite unsafe. Why not use deco gas as a travel mix?

...If you could do it safely freedivers in trouble could get help from support divers under the surface.

I see what you mean. Once the freediver breathes compressed gas, they become a SCUBA diver and would have to ascend as such.

 

[Vicko]

Unfortunately I have nothing concreat. All I know abut this has been from my own experience (when I do deep dives with overpacked lungs I can almost guarantee a lung squeeze), anecdotal stories and conversations with some physicians that are currently researching effect of freediving.
However I do believe I am right about what happens, even if why it happen might not be exact.

 

[dmaziuk]

The problem is not holding your breath, its ascending while you are holding it.

I always though the problem was closing your epiglottis while holding it while ascending. I would think as long as you keep it open you should be fine -- speaking purely hypothetically, don't try it at home & I don't intend to myself and all that.

 

[RainPilot]

I always though the problem was closing your epiglottis while holding it while ascending. I would think as long as you keep it open you should be fine -- speaking purely hypothetically, don't try it at home & I don't intend to myself and all that.

Hence the second part of my post. There is a definite difference between a "stopped" breath and a glottal hold.

As an experiment get a family member to stand behind you and hold you in a bear hug pose. Breathe in and halfway stop. DON'T force a hold. Let them squeeze you and you will find the air goes out of your lungs easily as it's only tension in your diaphragm holding the air in.

Then do a proper breath hold, you will notice that in order to do that you will need to inhale and then exhale slightly to lock the epiglottis. A little like locking an inertia reel seatbelt. Then when they squeeze your ribs will give way before your breath does. This is where the LOI comes in.