here's an idea - cough up some sputum into a paper cup. not saliva. a good honk of sputum.
turn it upside down and see how long it takes for it to slide down the side of the cup.
that's why Children's Hospital of Los Angeles uses the term "postural drainage" meaning laying on a slant while clapping. and why it didn't even occure to me that someone would just lay on a slant to drain mucus out of their lungs. man if it were only that simple.....
if laying on a slant were effective to get mucus up from the depths of your lungs, insurances wouldn't pay $16,000 for a Vest.
but using gravity to assist with legitimate CPT of any form (HFCC, manual, etc) can only help <img src="i/expressions/face-icon-small-smile.gif" border="0">