NAC (N acetyl Cysteine) is a supplement - that has both anti-inflammatory and anti-mucolytic properties. So it is thought reduce inflammation in the lungs of people with bronchiectasis and help loosen mucus.
Here is an article about its use:
https://bronchiectasisnewstoday.com/2019/05/09/n-acetylcysteine-potentially-beneficial-bronchiectasis-patients/
There is a large multi-year study underway in China right now where scientists hope to reach conclusions as to long-term effectiveness, dosage, etc,
Sue