Same here. I can only nebulize 3% once a day for 10 minutes. If more than that my lungs got really irritated and bleed. Some days, I have to take a break. Mucinex helps thin the mucus, but it triggers cough and often gives me coughing fits. That is my experience.

@cate123456 I was not aware that hypertonic saline caused inflammation and potential bleeding. What does your doctor say? I wonder if the osmotic action of the hypersonic saline makes it feel as though your lungs are congested and inflamed? Hypertonic saline helps to draw out the accumulated phlegm in your lungs so it can be coughed out. Are you using a bronchodilator before the hypertonic saline?

If you tolerate mucinex and it does not trigger a cough like it does in me and also @sweethighland then that's great. Some people also like NAC. Some take NAC and mucinex together. The only real way to figure it out is to experiment. Fortunately, both are safe for most people as long as you stick to the recommended doses but neither are substitutes for hypertonic saline.

For a while I took both NAC and 12-hour mucinex together. That combo seemed to work well until I started coughing at night. Once I took myself off NAC and later mucinex the coughing subsided. Now, I use levalbuterol followed by 7% saline via nebulizer and then airway clearance.

This paper on "Mucolytics, Expectorants, and Mucokinetic Medications" explains the mechanism of these medications on mucus on the lungs. Lung mucus is quite complex stuff with multiple factors at play. It leaves me with more questions than answers!
https://rc.rcjournal.com/content/respcare/52/7/859.full.pdf