I have been traveling with cpap for years. My only problem was on the Osterdaam this year. I did not receive my bag so I had to go to Guest services for help. It was confiscated because of 2 extension cords that I carry in the bag. I was told they were not acceptable. Now, I have used both on over 200 days cruising, one is heavy duty UL approved 15 ft. Yet they were not allowed. What was really crazy, is they provided 6 ft. surge protected power strip for me to use instead!
The room steward was kind enough to find a simple extension cord just before bedtime.
I suggest you carry, not only your machine and mask, but also your extension cord in your carry on luggage.