I could not exercise for the past 8 months. My doctors told me not to, until I got better. Now, I have to wait until I recover enough from Nissen to start. Exercise became difficult last year following a bout with sinus/respiratory illness, too. It was never the same after that. I always had to use my emergency inhaler and take more breaks, work out less than I wanted.
Sorry - I'm no expert but I've learned a lot the past few months. I suggest avoiding it until you get your completed diagnosis and you are on your way to recover. Sorry - I know that is not what you want to hear, it surely was the same for me. As I sit here on day 6 post-op, I'd love to get on my Pilates reformer, but I won't.