@nanamillie
Does he have a regular sleep dr he can talk to and say that he’s still having symptoms? The machine may not be set to the right pressures or some other parameter. Or, are you sure he’s actually using it?
I too use a CPAP and I’ve learned that what looks correct in the sleep lab doesn’t always work out in the real world. He may in fact have a machine that’s wrong for him. I titrated to a bipap twice in sleep studies, but in the real world it was a disaster. My ahi went way up, etc. I went back to my CPAP set in apap mode and things got better again even though it wasn’t technically ideal.
Finally, I know this is frowned on, but I only started making progress when I learned how to get into my clinical settings and (carefully)experiment with pressures.
Just my thoughts on the subject-good luck