Restrictive pattern on PFTs essentially fall into three categories, unfortunately you've had them all investigated. It can be the lungs themselves (i.e. fibrosis, or stiff lungs), chest wall noncompliance (think of terrible scoliosis, severe obesity, etc), or neuromuscular disease. The first two are typically pretty easy to diagnose, neuromuscular disease can be very difficult. There is no gold standard for how to determine if restriction is related to neuromuscular disease, but the sitting/supine spirometry is often done as one piece of data (as it appears you have done).Have you done a MIP/MEP (maximal inspiratory pressure and maximal expiratory pressure)? A low MIP tends to indicate diaphragmatic problems, and a low MEP indicates problems with chest wall strength. Like the sitting/supine spirometry, these must be interpreted with caution, as they are not truly gold standard for anything.If all else fails, there is always the Cardiopulmonary Exercise Test (CPET). It's basically a test that measures your heart and lung function through maximal exercise to determine where exercise intolerance may be coming from. It's not always available in all places and can be very difficult to interpret.All in all, with your story I would put my money on a neuromuscular issue. I think the neurologist ruling it out based on the positional spirometry alone is premature. Bring up the MIP/MEP and CPET to your pulmonologist and see what he/she thinks.Mind if I ask where you are being evaluated? You would likely benefit from going to a tertiary care center, such as affiliated with an academic or university medical center. Depending on where you are located I could suggest some places to find docs who'd be interested in you.
Respiratory restrictive pattern, unknown cause please help.I am 21 years old male.I have started having bad shortness of breath the past 4 months. I have seen so many doctors and this is the results so far.The originally test to prove there is something going on is the respiratory function test, I cant interpret all the results but the pulmologist said my breathing shows a restrictive pattern with 65% of expected lung capacity and velocity. This test has been repeated every month with similar results. Gas transfer was 95-100% not indicating lung disease.Got a ct scan of chest with dye to rule out lung disease or to see if anything else is on my lungs but it came back clear other than enlarged thymus gland.They thought it might be respritory muscle weakness although the neurologist said unlikely as when I am lying down the respiratory test shows similar results as to standing.Cardiac possibilities cleared by cardiologist.The cardiologist, pulmologist and neurologist are at a loss and have determined to just hope it doesnt get worse. Please help.