I urge you to ask for imaging that can show blood clots in the lungs. My brother had this as a side-effect of a med he was on. It was a mystery for weeks/months until an ER doc saw him and got the right answer. (More than 12 other visits to various docs had already occurred.) Good luck
The description that you have provided suggests that your son does not suffer from asthma. Having hypotonia in addition to a breathing problem may make it more difficult to find treatment that will help your son.
Generally testing for a breathing problem starts with a simple breathing test called spirometry. You would exhale into a machine called a spirometer. The spirometer would measure how much air is exhaled in the first second and the total amount of air exhaled. The information gathered from this testing requires that the person being tested gives their best effort when exhaling. Your son
I urge you to telephone the LUNG LINE nurses, at 800-222-LUNG(5864) on Monday, to get some advice about your son's situation.
If your son can be seen at Nat'l Jewish Medical & Research Center, in Denver, Colorado, that would be great. If not, the LUNG LINE nurses may be able to recommend some good doctors in your area.
Good luck to you & your son. You can call the LUNG LINE, and see if you can leave a message, if no-one is in, on the weekend.
Sincerely, Concerned lady