Originally Posted by alice md

The proper respiratory tests that should be done, at the least, are:

routine spirometry (which measures the volumes your lungs can generate and may be completely normal).
MIP/MEP (which measure the force your respiratory muscles can generate against resistance)
MVV-which measures your respiratory muscle endurance. It is the volume you can create by breathing as hard and fast as you can for a minute.

A sleep study with measurement of oxygen and CO2 (this can detect subtle but significant abnormalities which will not be apparent during waking hours).

There are other more elaborate tests that can be done, if those tests are suggestive of a respiratory muscle problem, but do not give a definite answer.
But, those require special expertise and equipment, are not done routinely in most places in the world and their accuracy is not agreed upon.