Hi, my O2 saturation is in the low 90's at rest, but drops to the low 80's with standing or mild exertion. My heart rate is in the 60-70 bpm range at rest, but jumps up to over 100 bpm with standing. I feel SOB with exertion and have been given a Xopenex inhaler, which provides some relief. This has been particularly noticeable for the last 4-5 months, but I don't know how long I've had the problem. I'm 57, overweight (190 lbs./5'6"), but work out very vigorously in water aerobics 3 times a week (for many years).I underwent a thorough battery of both pulmonary and cardiac testing, with no other abnormal results. I am a former smoker who quit 20+ years ago. I have also been diagnosed with sleep apnea and have had O2 sat's as low as 70 while asleep. Help!