Hoi - according to the technical specifications of the instruction manual (page 17), your sleep apnea device has a typical consumption of 53W(att) and a peak consumption of 104W(att) - would therefore mean: it consumes between 53Watt(hour) and 104Watt(hour) per hour. The Jackery can deliver 518 watt hours (i.e. either 512 hours 1 watt) or e.g. 10 hours with 51 watt - let's deduct a little from the 518 power (power losses, marketing air etc.). - Let's say a generous 10%) - minus 51 watts, then we have the Jackery (518-52) 466 watt hours.
This gives a running time with the RedMed of between 4.4 hours (full power 466/104) and 8.7 hours. I don't know what the average consumption of your Resmed is, but you could measure it with an ammeter (something like this: https://www.digitec.ch/de...)...

Keep in mind: The morning after, when the device is fully used, it could be quite discharged, and over the long term, that might not be so great for the batteries that are built in. At best, you will be happier with a power station with LFP chemistry for longer (it is a bit more expensive and a bit (little) heavier than lithium).

How do you want to charge it? In the bus on 12v while driving? Solar? On camping with shore power? LG

Thank you for your answer! I would use both options for charging.