> That said, many of the tuning parameters require the doctor to set them

No, they don't. At least not on a Resmed machine. You just have to enter a special mode to change them. On my machine that's holding down 2 buttons for a couple of seconds.

> if you make an appointment you can talk over the problems and get them to adjust the pressure or whatever.

I'm glad you had a Dr that did this for you. It is not the universal experience, and it definitely wasn't mine.

Which two buttons?