I have just got rid of a chronic cough - have had two bouts of bronchitis during the last three months,(without having a cold), phlegm ran into my lungs, had x-rays taken which showed pleural thickening. To shorten a very long story of wrong medication which didnt work .... eventually found out that the phlegm came from my stomach due to low stomach acid !!
So believe it, your stomach can cause bronchitis, asthma etc etc ...
When the "valve" for a better description, above your stomach becomes faulty, contents of your stomach pushes up your throat. (GERD) Mostly acid which ends up with heartburn, but I never had heartburn in my life and in my case it was phlegm which was pushed up, at night running down my bronchial tubes.
There is a very interesting article on the grandtimes.com website, : "Gerd: the surprising cause of many physical disorders", from which I learnt a lot.
So with low stomach acid, bought "Bio-Enzymes" and after three days my phlegm is gone and so is my cough, just like a miracle. So you never know!
good luck ...