Not an inverter, but a converter. IMHO. If your CPAP machine has a 12v mode of running it nether would be needed.
My CPAP machine doesn't have the 12v option, but it has a Flight Mode setting which drops the power used to 75 W, which is low enough for a 12v to 110v converter to be use my CPAPA through a night.
A simple converter can be used to plug into a 12v outlet, then the CPAPA can be plugged into the 110 side of the converter.
Nice to have a 12v outlet nearby, I'm planning on doing one closer to the bed.
Here's what my Fisher & Paykel instructions say:
Flight Mode allows for the device to operate on a reduced power (75 W). Situations for use in this mode might include long-haul air flights and camping.
NOTE: Humidity output will be significantly reduced in this mode and is not recommended for long-term use.
• Turn the SmartDial to the Flight Mode setting (airplane symbol)
and press to enter. Turn to select On (a check mark) or Off X and press again to accept the change.
• The Flight Mode symbol will be displayed continuously on the Home Screen while the Flight Mode is activated.
*the symbol did not copy to be pasted, nor the check mark.
I used a inverter for two weeks while camping in Alaska this past summer. My son had a generator to help keep the battery up on the rented TT.