Wow, Rita, I had the same experience with metoprolol and my lungs.
In my case, it was an intractable asthma attack, at the time I was diagnosed with bronchiectasis & MAC, that led to the discovery - by the advisory pharmacist at my clinic - not a doctor. This was 4 years ago, when he was consulted to try to figure out a different combination of meds for the asthma. My primary & the pulmonologist were both surprised. But stopping the metoprolol controlled the asthma. Now I use a different med that doesn't control my heart rate as well, so have many episodes of too high heart rate, which brings on its own shortness of breath.
Sue