@sweethighland I get PulmoSal 7% from Sam's club. I also lie on my back as part of airway clearance, for me it is a very effective sputum producer. I do not believe sputum is acidic and would not cause damage to your airways. Make sure to have an empty stomach when you are lying on your back trying to get the sputum up. Less likely to have reflux come up and cause problems.