Keep in mind a cpap may not deliver the same pressure in the air as on the ground.. most are calibrated for the approx altitude around where you live, while an aircraft internal pressure is much higher. Then, of course, there's the noise/power/space constraints.. Some are pretty loud, plus where will it sit while you sleep? Possibly the floor, but there's a risk of stuff being sucked in through the vents..
I flew that flight in may in business. There was plenty of room for it to sit by your head with the seat in the bed position, and the outlet is right there.