I'll be flying with my CPAP soon for the first time in over a year. In the past I've had a variety of experiences at security. I know that at security I'm supposed to pull "the CPAP" out and put it separately into a bin so that it will be visible, but that hasn't always been required of me. My CPAP comes in 3 discrete parts: the CPAP machine itself, the separate power supply and cords, and the mask and tubing. I also travel with a compatible extension cord. These days, which of those pieces do the TSA folks actually want to see? It would be wonderful if I only have to pull out the machine itself as I also juggle my carry on bag (containing my jacket, hat, pocket contents, metal belt buckle, and my metal Medic Alert bracelet in addition to the other things I'll need to keep out of my checked bag), my 3-1-1 bag, my liquid meds bag, and my shoes.
Just roll with the flow on the CPAP. Homeland Security sees them every day, all day in carry on luggage. Just do as they ask, no more and no less.
When I flash my insulin pump, they often just send me through the fast line--not x-raying me.
We just left everything inside the carry-on case last trip, one way with TSA pre-check and the return without. Didn't have to do anything at all. Just put the bag on the belt; if they want more, they'll ask you.
During my European travels in 2010 and 2015, just to be safe I had a letter from my sleep doctor saying that I use this machine, and I printed up a laminated tag that said 'Medical Equipment'. I think once on all my flights I had to open the case up, but otherwise smooth sailing. And because it was carry-on (I would never check a CPAP case through) I could stash my meds and small items I had to have in the case as well. Worked great.