To check for GERD they usually do a 24 hour PH test, which is basically a special tube like a NG tube that is connected to a small computer that you take home and wear for 24 hours, you eat and drink normally as well as doing normal activities, you also have a button to press if you experience reflux which marks on the computer so when they read the results it will have a mark against that time you pressed the button and they can see what exactly the acidity level was at that particular time that you experienced the reflux...
The problem with reflux especially chronic reflux is more so when you are sleeping if you regurg you have a greater chance of aspirating your stomach matter into your lungs and the acid soils/burns the lungs, which obviously is not a good thing...
If your 24 hour PH test comes back indicating a problem (servere enough that is not controlled by medication) they usually do a fundo thingy? where they do an operation that prevents the stomach acid from being regurged...
But yes, reflux if servere can damage the lungs, I know a good friend that had perfect lung function/health that lost some function and health due to the soiling of the lungs from acid reflux...
Hope this helps, and makes sense (I'm way tired)
fr3ak