Well it's not exactly a spell but it is energy workings.
Just close your eyes or keep them open and imagine green ( or whatever color that represents heal and life to you) swirling around your lungs. Imagine your lungs becoming cleaner and your breathing become more easy. Do this every day and I'm sure it'll get better.
I was going to say something similar. When I do it, I imagine the pain or whatever issue as black energy that I release into the air, for this you could probably breathe it out. It's a simple technique but very effective.