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Exhale Diving

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
I think by 'passive' it means that you let the diaphram and intercostals to return to their natural place, without using them. As in what you have between unconscious breaths.
I think PASSIVE exhale confuses people as well. My approach to passive exhale is to breathe all the way in (your lung pressure is now greater than the surrounding air ie you feel full). If you then open your mouth and relax, your chest and stomach will collapse a bit as the air naturally rushes out until your lung pressure equals that of the surrounding air. You have now completed a 'passive exhale' and as long as you don't exhale further by raising your diaphragm you are at FRC.

there's also a noticable difference whether your body is flat on the surface or upright, and whether you exhale through a snorkel or into the water. being vertical and exhalig through a snorkel means less air for the frc as the water pressure can compress your lungs more.

I understand passive as relaxation of muscles versus exertion of muscles. It seems like FRC is kind of abstract, and subject to much variance. Is there any data on how much air a person has left in their lungs when they have obtained FRV? Or even better, data relating this amount to Reserve Volume?
Sebastien Murat said he has 5.25L of air left at FRC. I have 2.85L to 3.5L, depending on how 'passive' my exhale is.

However, your ability to exhale every last bit into the spirometer will change your numbers a lot.
Are those numbers including RV?
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Not including RV. If it included RV, then it wouldn't matter how hard/how well you exhaled into the spirometer.
There is no way to measure RV or FRC with a spirometer.
You need a pletysmograph or gas dilution
Yes Frank,

FRC is the sum of RV and ERV which is impossible to measure with a spirometer.

If one like Eric can blow 2,85L (which actually is ERV) from FRC to RV, most likely his FRC~4,5L. (Given that RV is normal 1,5-2L)
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- On the forum, most people often use FVC as equivalent to lung capacity (TLC) (Where TLC = FVC + RV)
- Similarly, we often use FRC as equivalent to ERV (FRC = ERV + RV)

So, when I say I have an FRC of 2.85L, this is not the 'true' FRC.

The reason people use these simplifications is because no one has the capacity (at home) to measure RV with dilute gas. I think Bill found a method of doing it with buoyancy changes in the ocean, still complicated.

For the most part it is acceptable, for the purpose of the discussion, to ignore the RV.

So, we might say that with a full inhale, I get 10.8L, and at FRC I get 2.9L, both neglect RV.
Oh yeah, and are there any links to discussions pertaining to a complex method of measing residual volume via bouyancy changes? Just thinking about it, I can not figure out how that would be possible. As one's residual volume is relatively incompressible, it should have no effect on bouyancy.
Bill's method, I believe, was to descend to 10m, exhale fully WHILE AT 10M OF DEPTH, then ascend, and exhale into a spirometer at the surface. Then, do the same to 5m and 15m.

From that info you can calculate RV.
Tyler, Apnea Gang,

I assume "passive exhale" means breathing out normally?
Oh, BTW--Tyler, have you given any more thought to writing a novel? Maybe we could collaborate, at least help each other with research???
Water Rat, who may or may not have broken 7--but *Seriously Doubts* she's even come close to 8! <Some of her characters WILL>
Kars wants me to write a script for a Freediver Movie--one that's about the feeling of the sport--instead of the usual competition thingie. I have practically NO competition experience--NONE--except the Church Camp Underwater Swim--wherein I came in--DEAD LAST! :( I was on a swim team, though....maybe doing so badly in the Church Camp thing motivated me--shamed me, actually--LOL!--into joining the team--to improve my skills! Ha! But mostly, I joined the team just because I wanted to! For BOTH slimy reasons, and pure ones. :)
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