What is the halacha for using a CPAP machine for sleep apnea, that must be used daily, on Shabbat? A CPAP machine for sleep disorders obviously would be switched on before retiring to bed and off again when one awakes but it cannot be left on without actually being in use, but on Friday evening that would violate Shabbat.
Unfortunately the only source I can provide is my Rabbi, and not a hard ruling in the Sefarim. If someone can find such a Sefer that concurs with the below, feel free to edit in sources.
He ruled that if a person will be unable to function properly (not necessarily life-threatening) on Shabbos without using the PAP device on Friday night, it would be a case of a Choleh She’ein Bo Sakanah, for which we permit Rabbinic prohibitions. Therefore, one should use his foot, etc., to start and stop the machine, in order that it be a Shinui.
He further ruled that obviously anything that can be done before Shabbos (ex. presetting the pressure and humidity, if the machine doesn’t do it automatically) should, but if one forgot (or another one is), then one may adjust those settings with a Shinui as well. Whether one meets the benchmark of a Choleh She’ein Bo Sakanah should probably be best addressed by one’s LOR and LOD (local orthodox Rabbi and local orthodox doctor).
If a person is able to function normally without his CPAP for one night, it should go without saying, based on the above, that he should forgo the CPAP for one night.