The difference I noticed after I started using it again was a gradual lessening of the amount of sputum. I don't have near as much sputum as some people seem to have and no cough, but apparently there was enough kind of "stuck" in my smaller airways that I did not realize was adding up over time. I noticed it was getting harder to breath deeply in my spin class at the gym and it was becoming a chore. It is an intense class anyway, but this was clearly different. After a couple of weeks of using the vest and clearing out some of what seemed to me to be a variety of old crud, my performance and ease of doing the spin class improved and my sputum is now minimal. I'm not quite Lance Armstrong but I can outspin a lot of my classmates my age and younger! Ha-ha! 🙂