You may not necessarily increase your lung function, but you can make what you have much more efficient and effective by daily exercise. You should include at least 30 minutes of non-stop aerobic activity (walking, jogging, jumping rope, biking, whatever trips your trigger) and at least 30 minutes of weight/resistance activity aimed at strengthening the upper, lower and core muscle groups three times a week. If you do this, you will find that things that are difficult today will be much easier as you get in better shape. Your lung function may not increase, but if things are easier to do, you get sob less often and you can do more, it's well worth the effort.

People have done it before with steady, challenging exercise, so I guess the walking should be real work and not just strolling. It helps in lots of ways. I hope you do it.