I have difficulty inhaling sufficient air. Several pulmonary function tests, with consistent results, confirmed the diagnosis. I ve had numerous tests for neuromuscular diseases with negative results. Yet, I still find it extremely difficult to perform activities with exertion such as singing, exercising, climbing stairs, etc. I first experienced this difficulty after a serious car accident in 1997 and has gotten progressively worse - to the point where it is limiting my ability to do the things I love.