I have right phrenic nerve damage from radiation to abdomen and chemotherapy. I have known this for 7 years. I have used a BiPap since that diagnosis but find that over time my activity level has dropped due to shortness of breath. I was on Metoprolol XL for a long time but had to be taken off of it when I began using inhalers for asthma/COPD. I keep an oximeter at hand to monitor my oxygen levels. It is discouraging to be so limited, but still life is good.