Never hold your breath, except...

[Bopper]

One thing I've always wondered, personally- is lung over expansion something you feel immediately (like a pop and you're screwed) or a feeling relative to your ascent rate where you can feel the uncomfortable pressure building and can accommodate by exhaling deeper.

I was reading a book recently about decompression theory and the author noted that humans have never developed nerve structures in the lungs to warn of air expansion. Makes sense as why would we ever have had the necessity to evolve such a system?

My personal expectation if I'm in a rapid ascent would be that I simply exhale as much as possible and try not to inhale until you get to the surface. For me, it seems that the single most dangerous threat in diving is an embolism, followed by convulsions due to oxygen toxicity, then the bends. I'm sure some might switch the first two, but for me I think a rapid ascent is more likely than violating the max operating depth.

 

[nimoh]

I was reading a book recently about decompression theory and the author noted that humans have never developed nerve structures in the lungs to warn of air expansion. Makes sense as why would we ever have had the necessity to evolve such a system?

My person expectation if I'm in a rapid ascent would be that I simply exhale as much as possible and try not to inhale until you get to the surface. For me, it seems that the single most dangerous threat in diving is an embolism, followed by convulsions due to oxygen toxicity, then the bends. I'm sure some might switch the first two, but for me I think a rapid ascent is more likely than violating the max operating depth.

I respectfully disagree. With proper dive planning and procedures, you should have about a 0% chance of an embolism, same with oxygen toxicity. As for the bends, scubaboard is littered with posts of "undeserved" hits.

 

[Lorenzoid]

If you're diving on air, you have a 0% chance of oxygen toxicity within recreational depths. I have to assume Bopper is presuming he's diving on Nitrox.

I'm pretty sure that statistics show the "single most dangerous threat in diving" is simply running out of gas. Of course, someone might use up their gas due to another underlying cause.

It's complicated. That's why we have SB

 

[Bopper]

If you're diving on air, you have a 0% chance of oxygen toxicity within recreational depths. I have to assume Bopper is presuming he's diving on Nitrox.

Yep I was talking Nitrox.

I'm pretty sure that statistics show the "single most dangerous threat in diving" is simply running out of gas. Of course, someone might use up their gas due to another underlying cause.

LOL.Yeah I guess I overlooked the most obvious threat.

 

[Bob DBF]

I'm pretty sure that statistics show the "single most dangerous threat in diving" is simply running out of gas. Of course, someone might use up their gas due to another underlying cause.

It's complicated. That's why we have SB

It absolutely amazes me that any diver runs out of air in this age of the SPG. There are situations where you watch the the needle go to zero and evaluate your luck, but as a recreational diver you should be trained to avoid this.



Bob
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I may be old, but I'm not dead yet.

 

[Griffo]

It's a shame that the only reference I have ever seen to learning to keep your glottis open, is here on scubaboard.

 

[Osric]

I'm surprised nobody has answered the OP's question with the simplest and most common reason to hold your breath which most divers do on every dive - to equalize. The Valsalva maneuver is, I believe, the most common equalization method. It even seems plausible to me that newbie divers who are descending too fast would start to kick upward and apply the valsalva maneuver erroneously at the same time when they feel pain in their ears during descent.

Osric

 

[dallaskincaid]

Agree. If I'm going up OOA I want to keep as much remaining air as possible.

Remember though, it's not the air in your lungs that keeps you from needing to breathe, it's the level of carbon dioxide. So, breathing out that co2 might actually help you to stay conscious longer.

 

[Griffo]

Remember though, it's not the air in your lungs that keeps you from needing to breathe, it's the level of carbon dioxide. So, breathing out that co2 might actually help you to stay conscious longer.

How so? Unless you can breathe in again, you've got no gas in your lungs for the CO2 to exchange into, so on breathing out you are stopping any CO2 removal at all.

 

[dallaskincaid]

I'm using logic, which always gets me into trouble! haha The girlfriend is a Dr and a diver. I'm checking with her now to see if my theory is correct.