Chris, I have what the dr. described as a severe case of sleep apnea. I cannot sleep anymore without my CPAP. I keep an inverter and an 18 AH battery stored near the bed in case of a power outage. I had to use them just recently when someone took out a power pole near our house. It works just fine. I have a friend that has a CPAP that is very similar to the one you are describing and he uses it every summer at a church camp on an island in the middle of Dale Hollow lake. He just takes the battery out of his van when they leave the dock and he tells me it lasts the whole week, he just has to get someone to give him a jump start when he gets back to the van. Once she gets used to it, she will not want to sleep without it...
Tom