So George, I do more believe the effects you feel with metoprolol are more related with the cardiovascular effects of dilating arteries, lowering blood pressure (and yes, heart rate which is why this is a good drug in controlling a-fib), which can decrease overall stamina (but not effecting lung dynamics). I do believe rather a weight lifting program focused on chest wall and abdominal respiratory muscles may be in your best interest.
.... AND you are in luck, as I am running a special for a limited time where you can purchase the workout manual "Better Trumpet Playing Through the Bowflex System" in just 14 easy lessons for the special, low low price offer of $9.95. What a value considering the regular purchase price of $59.58 at local Planet Fitness stores! A collection compiled by Gary M. Onady MD, PhD, best selling trumpet fitness author and widely know for being the greatest individual in spewing a LOT of HOT AIR!