I have one that is battery operated so when we camp without electricity I can go for 3 days (got a prescription for it from the doc) when I needed a new machine..with Medicare you're entitled to a new machine every 5 yrs, which was nice as when they tested my old machine it wasn't putting out the proper level!
If you use the search feature there are lots of threads about cpap on here and it will give you more support...I had an awful time getting used to mine. I would use it only a little and it bothered me, my doc said to use it as much as possible so I always at least try it every night and also use the ramp feature..it starts off lower so you can get to sleep and then in about 20 to 40 mins it gets stronger