I also use 7% saline and a vest twice a day. The saline has kept my MAC knocked down. When I used it the first couple of times it was a bit irritating and caused me to cough right away. Now it doesn’t. I don’t have a constant cough either, so I don’t know how it may affect you. Others have said they mix 3% and 7% until they are able to tolerate the 7%. The knowledge I have gained from others on this site indicates that the saline does more than just thin the mucus. It helps keep the MAC knocked down too. I don’t think most pulmonologists know that. I had to stop using albuterol because it made my heart race and made me very jittery.