Your Dr would best know if you should use an expectorant, and it is good of you to be cautious and careful. This is very wise. There is a nice tea I really like for my lungs called "Breathe Deep" by Yogi Tea. I mention it because it is gentle, made for lung health, and supports healing. It is so wonderful and tastes so good, people without lung damage ask me for some when they visit, or when I carry some with me in a thermos say it smells so good what is it!!! Also, the warmth and the vapors from the essential oils in the herbs are very good for the respiratory system and nasal passages. I sometimes see it at Target, but always Whole Foods and some other big grocery stores. The ingredients are listed on the side and are pretty gentle - none should be an issue unless someone drank like 20 cups in one day! : )
Always good to check all the ingredients anyway. Greens tea has natural antibiotic properties and also natural caffeine, which opens up the airways a little bit. It also has antioxidants that help heal the lungs and keep you well in general. This is a small thing a person can do that is not expensive, but can make a difference in comfort and healing! We need strong lungs to live a good life! : )