My daughter is turning 21 on Nov 19. She has been experiencing severe shortness of breath...taking a flight of steps leaves her gasping for air. Her heart rate increases sometimes to 200 bpm from very little activity.just going from lying down to standing doubles her heart rate. She was in the er and had a multitude of tests done. She has seen 2cardio doctors and a pulmonologist. She has had an echo with Doppler, chest X-ray, blood work, cortisol levels, holter monitor, breathing tests...nothing is showing up. Any ideas?