Yikes! I've been diagnosed with sleep apnea. I tried the CPAP and hated it and, like your SIL, refuse to use it. All I could think of was this...
Same issue as full time oxygen needs. Just different equipment. With a cpap's smaller electricity requirement need, even just a automotive or marine battery kept charged by a 50watt solar panel and a power inverter for the cpap would be minimal cost. When your life depends on a piece of equipment working you have to plan for failures. My sister in law died in her sleep not because her cpap failed, but she refused to use it and her oxygen levels fell to a point finally one night that it killed her.
Yikes! I've been diagnosed with sleep apnea. I tried the CPAP and hated it and, like your SIL, refuse to use it. All I could think of was this...