If you cannot afford a different CPAP, consider then an oximeter. Supplier #19 has some good ones. A lot of us have the CMS 50D Plus. Since I have a dumb machine, I use the oximeter to monitor my therapy, especially when starting a new medication or when I think my sleep is off.
There's some reviews of several different models in the Review section here.
Apnea Board Moderator
Breathe deeply and count to zen.