I have a similar lung problem and my Dr told me to stay away from smoking and just eat it if I must partake in said activity . I think you can up the capacity by working out and making an efor to breath in through your nose until you can't get anymore air then breath out your mouth. Our lungs are muscles so if we work them out a bit we can achieve better breathing. I've been doing tai chi and Buddhist meditation for five years now and I know that personally helps me, you should look into that hell even tantric sex is supposed to be good your you.....lung that is.

Good luck mate a please be careful make sure to keep us posted, Brit!