I have a Philips Respironics, it is a 12v machine. My DW has a Resmed Ultra I believe, and it too is a 12v machine. What I did was install 2 12v outlets, 1 on each side of the bed to plug our machines into. The 12v service is 8 gauge wire running direct to 2 12v deep cycle batteries, with a 10 amp inline fuse. Haven't used it yet for more than 1 night. Hope to change that this summer, as DW has finished her chemo, and radiation treatments, so we can get out more!
So many campgrounds so little time!