This IS an interesting question. Never worked in the specialty, but my understanding is the physician needs to specify all sorts of information- type of mask, pressure, etc. and that incorrect settings can cause additional issues, or not help the apnea.
If I was reviewing documentation that specified all of this, and maybe even some of the risks, then I would count it as moderate risk. If it just said "CPAP machine nightly. Rx issued" and no other information, then I would count it as low risk.
Simply my opinion, as I was unable to find any specific reference for this.