Can GERD cause an abnormal spirometry test? My doctor asked me if I have heartburn a lot and I do. He said it could be GERD instead of asthma causing my problems. My PFT was low. But another test after I had been on meds for GERD was normal (PFT). Could this have been GERD all the time? But sometimes I am still short of breath...Thanks !!!

GERD can produce some weird reactions on spirometry tests.

It is an irritant to your lungs, and will make your lungs react like any other strong irritant -- with some inflammation and some bronchoconstriction.