What is your working definition of "CPAP failure" - number of weeks, mask trials, structured adherence intervention - before you move a patient to HGNS, OAT, or pharmacotherapy?

I have a hard time with this because my personal definition is not the current definition for payment. However, I try to determine what the patient is willing to accept for therapy before even testing them. I work at the VA, and a lot of the patients have claustrophobia and are, therefore, averse to...