I've used a CPAP for 10 years, and recently moved to Medicare from my company insurance. The company that provided my supplies went out of business at the same time I went on Medicare.
All the local suppliers told me I had to have a Face2Face meeting with my doctor and a new prescription or they couldn't sell me supplies any longer. After about 6 months, and a few mistakes with my family physician, I discovered the F2F has a special form and is easily completed by a sleep doctor. After a short visit with the sleep doctor, they sent the correct form along with a new prescription to a new supplier for me, and everything is now working well. I had the notes from my original sleep study (original data no longer available), and they were all the new sleep doctor wanted to see. Also took the data chip from my CPAP machine for him to read.
The sleep doctor said I should see him every year from now on, but I don't believe that. I never saw another sleep doctor after the first review when originally starting use of the CPAP. Over the years, just a prescription from my family doctor was fine to buy supplies.