OOA + Missing buddy + Breath hold safety stop?

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ScottB

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I was in the free diving forum reading aorund, and the following was said:

freediver:
Again, there is a strong degree of comfort knowing if i were out of air at 100 feet and I were able to get a decent breath I could ascend, while exhaling of course, and make it to the surface. My only concern would be that I could probably only do a three minute safety stop as opposed to five.:D

Which lead me to wonder, theoretically, if someone could do the CESA and then do a breathhold safety stop, would doing said breathhold safety stop allow off gassing to reduce the risk of DCS?

Just my under-medically-educated mind thinking, but without respiration to carry gasses out of the lungs, that the gases would not, to a large enough degree, transpire from the blood to the lungs..

-Confused

Scott
 
I didn't see the original post but is freediver talking about taking a couple breaths off a tank diver at depth while freediving or an actual OOA?

It kind of doesn't matter since my answer is the same either way, once you've committed to compressed air, you need to go up with the donor, IMO.

Rachel
 
How, if your out of air would one do a safety stop? Besides, this falls into the NDL catagory dive, time permiting of course. I would consider the source as a bone head and ignore the hypothetical ramblings of a non diver.
 
Sorry.. the post was here http://www.scubaboard.com/showpost.php?p=2093644&postcount=20 =)

Context was you are *scuba diving* and have an OOA, and are able to do 4-5 minute breath holds.. and do a CESA w/ exhale.

Bringing the theoretical question if a safety stop without breathing would be beneficial.

(which, .. somewhat similar to a lesser degree... during my basic cave course, my instructor and I were doing O2 deco.. and he was skip breathing it.. he told me that he would off gas just as efficiently doing short inhales and long drawn out exhales on 02, versus taking slow deep breaths..)

Thanks,
Scott
 
Would you actually off-gas without exhaling and inhaling? Surely you would off-gas to a minimal extent until the partial pressures of gasses in your body (and lungs) reach equilibirum. I can't see that stopping for three minutes would have an appreciable benefit.

But, to quote a famous Spaniard, "I know nothing".

Cheers,

Andrew
 
This would do very little per Ohms law. The partial pressure of N2 in the blood would equilibrate with the partial pressure of N2 in the air in the lungs. At this point there would be no pressure gradient, thus no driving force to move N2 out of the blood.
 
logos:
This would do very little per Ohms law. The partial pressure of N2 in the blood would equilibrate with the partial pressure of N2 in the air in the lungs. At this point there would be no pressure gradient, thus no driving force to move N2 out of the blood.
WHO? Where does Voltage, Current and Resistance come into play?

To the OP, if you aren't breathing you aren't off-gassing. Also, if you were breathing compressed gasses and are *holding your breath at a safety stop* (stupid concept but I'll go with it) if there is much of any wave action you are probably embolizing from the pressure changes.

Joe
 
Ohms law is heavily used in physiology....although sometimes they give it different names...

In physics Current (I) = Voltage/Resistance

Voltage is also called potential difference....which if I remember correctly is the difference between charges on the two sides of a resistor (or whatever component)...

Current is the flow of electricity.

For gas diffusion across a membrane

Flow = (P1-P2)/R

Where P1 is the partial pressure of a gas on one side of the membrane and P2 is the partial pressure on the other. R is the permeability of the membrane to that particular gas. (1/DLco might approximate it?? or not...probably not because CO and N probably are quite different???).

It applies here because at no net partial pressure difference (P1-P2 = 0), there should be no net flow.
 
ScottB:
...he was skip breathing it.. he told me that he would off gas just as efficiently doing short inhales and long drawn out exhales on 02, versus taking slow deep breaths..

How is this skip breathing? For that matter, how is anything skip breathing? Shallow breathing is a legitimate problem as it will allow CO2 to build up since you are not flushing dead air spaces. But if you are doing full inhales and exhales (and by definition if you do more than one of either, you have to be doing both), there ain't no problem. Variations in the timing of your inhalations and exhalations are simply immaterial.

Right?
 
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