I use a CPAP and have used in Europe twice. Not only do you need a converter for the plug but my machine also needs to have the voltage switched in the machine. There is actually a fuse type thing that pulls out and flips over. Also for CPAPs I carry 2 or 3 extesnion cords as hotels sometimes don't have the best plug placement in the room. I also use a humidifier with my CPAP and I carry a Nalgene bottle that I got at a travel store to bring the distilled water instead of trying to find it when I get there.
Hope this helps.