I have a modern CPAP machine that can do both. At first I found it quite hard to stay asleep with my initial prescription. Altering the machine to use APAP mode

I have a modern CPAP machine that can do both. At first I found it quite hard to stay asleep with my initial prescription. Altering the machine to use APAP mode with a lower max pressure fixed things right up (with the doctor's approval of course). APAP, for readers who are blissfully able to sleep without issue, automatically alters pressure depending on whether you're breathing in or out, so you aren't breathing against high pressure. It's a lot more comfortable. CPAP machines are quite interesting from a computing perspective. They record a ton of data that can be visualised with an open source tool, and they use a lot of predictive algorithms to figure out how you breath and when to increase/decrease the pressure.