I have been on a cpap for the last 7 years.
Best thing I ever did is to get the 12volt dc cables for my machines.
There is too much power loss using an inverter.
While I was a scoutmaster I tent camped with no power available, so I had to make do a 35amp battery and a 30 watt solar panel
My current travel/backpack machine is a Z1, with the 12volt cord. It’s great, don’t buy the “power shell” it’s a lot of bucks for a small amp hour battery.
My mom is a copd patient, she uses a portable oxygen consecrator, it has a 2hr battery, and will run off a 12vdc power source. Can’t recall the name of it. But it’s the Medicare approved one.
She had a several hour power outage and plugged it in to a 12vdc deep cycle battery and it worked well.