94660 is the cpt code for CPAP initiation and management. This is a poorly understood code; there is always disagreement when someone asks about it at an American Academy of Sleep Medicine business seminar.
I used to bill this along with a level 3 (99213) evaluation and management code when I saw someone in the office, prescribed CPAP, and the patient's CPAP machine was set up on site. Usually on-site CPAP set up was done only for patients with Blue Cross/Blue Shield plans; it was done by a DME company that I had no ownership interest in.
I did find a mention of this code in an article in the American College of Chest Physicians. Although BC/BS payed for both codes (99213/94660) in Mississippi, apparently most insurers won't recognize both codes by the same provider on the same day: the 94660 code
is mutually exclusive of all E/M services during the same session by the same provider, according to the article (see the evaluation and management services section).
I do recommend that physicians not use the code 94660 with medicare/medicaid patients. If CPAP is being set up on site at your office (while the physician is present in the office complex), most insurers will not pay both codes at the same time. I do advise checking with the major insurers in your state to find out their policies for reimbursement of the 94660 code.