Calculation estimation of Residual Volume

[Bill]

I'm re-thinking the exhale at 10 meters. First Eric suggested using less depth. Now it appears that with full exhale at 10, the measured full exhale at the surface will then produce Vr + air in mouth + air in sinuses + air in mask + air in trachea +/- any blood shift/un-shift or VR + ?.

 

[baiyoke]

I was thinking the same yesterday, but actually found that as long as you keep epiglotis closed, when you ascent the air can get out of mask, and when you surface, you open your mouth just before blowing and get a neutral pressure... So I would say that from epiglottis and up things are pretty neutral, except maybe for the small amount you can get out from tensing the mouth and throat etc. Theoretically... because I can't actually remember if I did keep the epiglotis closed, or if I inhaled air from above epiglottis :-/

I'd still like to try it again some time, just for fun, perhaps doing it variable-weight being very buoyant.

Btw the 0,9 L where donee after a series of dives, 2 of them to 30m, so don't know if that's too shallow for bloodshift or not... it was in cold water and total darkness, so maybe the added stress could facilitate bloodshift. Nevertheless, the tmeasurement did not seem reliable at those trials...