#1 Rule In Scuba, Don't Hold Your.....

[dmaziuk]

So am I correct in that exhaling slowly amounts to the same thing as sitting in a chair at home holding your breath (other than as you say dmaziuk, that some CO2 is escaping, which may slightly reduce your urge to breathe)?

You'll have your muscles working and burning a bit more oxygen than you would just sitting in a chair, but I expect the main problems to be the urge to breathe and slowing down.

When I do freestyle pull, I start with a good breath and swim just keeping my epiglottis open (looking forward helps with that) and letting air escape on its own. I breathe out some in the turn, to keep pool water out of my nose, and I need to inhale after 30 metres or so. Main problem is I can't do 30 feet per minute that way, more like 60 metres per minute if I go slow.

 

[rob.mwpropane]

As I said seveal times before, it is easier when you are ascending than it is when going horizontal. There are other ways to do it than saying "aaahhh."

Agreed.

 

[BoozerWS]

As a caveat, there is a story of an instructor candidate during their IDC in Miami debating about how deadly holding your breath can be. To prove his instructor trainers wrong, he took a deep breath at the bottom of the pool and surfaced. He embolized, went into a coma and never woke up.

Wow that was dumb. He sure showed them. Anyway, you can embolize or cause some other overpressure syndrome from a pressure change of as little as 3 ft.

And BTW, the Navy stopped testing people's ability to withstand oxygen toxicity in the chamber years ago, when they realized that for reasons that are not well understood, people can endure much greater PPO2s in a chamber than they can under water.

3) PP O2 of 2.4 is ok in specific circumstances for short periods under supervision such as in a chamber and even then air breaks are normally included

This is very true. Science doesn't know why this is but a "dry" diver (chamber, NOT dry suit) can withstand a much greater ppO2 than a "wet" diver. The max ppO2 in a chamber is 2.8. There are a few times when this is appropriate but not often at all. Too dangerous. However, for clinical hyperbarics I put people in all day long at 2.4 for 130 minutes. Anyone put in at 2.4 or deeper needs to have two 5 min air breaks during the dive to lessen the chances of toxicity. When treating divers things are a bit different but the 2.8 ppO2 still applies in all instances. If they need to go deeper than 60 ft they will come off O2 and go with air or another mixture. Also if you need to extend the treatment beyond the normal table they will have to have additional air breaks.

 

[BoozerWS]

Question: If you are doing a CESA from say 60', does the expanding lung air do anything good for you--ei. getting more 02 to your tissues? My guess would be no, since when the air expands is also becomes "thinner". Perhaps just

Your guess is correct. You don't get more O2 to the tissues. While the gas percentage remains the same the gas density decreases which then is delivering less O2 molecules with each breath.

 

[TMHeimer]

Your guess is correct. You don't get more O2 to the tissues. While the gas percentage remains the same the gas density decreases which then is delivering less O2 molecules with each breath.

There are no breaths when doing a CESA--other than after ascending a while and then being able to grab a breath due to the reduced pressure. But inhaling is not taught to students when they do the CESA in the OW course.

 

[wildbill9]

Didn't read entire thread but what jumped to mind was "don't hold ur tallywacker when u per in ur wet suit"

 

[billt4sf]

which then is delivering less O2 molecules with each breath.

Very interesting -- never thought of that!

("Fewer" molecules with each breath.)

 

[boulderjohn]

Very interesting -- never thought of that!

("Fewer" molecules with each breath.)

As was pointed out, though, you are not taking breaths during a CESA, and the word "fewer" is relative. When you inhale in shallower water than you were in previously, you are indeed getting fewer molecules than you did when deeper, but you are still getting more molecules than you do at the surface, and you are still getting more than you need.

 

[dmaziuk]

("Fewer" molecules with each breath.)

Only in a purely hypothetical sense.