Wiki NP's performing procedures in hospital setting

[Sefstratis]

We employ ACNP's to work along side physicians in the hospital setting. We are currently billing shared visits, and have the documentation perfected. We are billing e/m under the MD's name. It was recently brought to my attention that the ACNP's were also performing simple procedures such as central lines, while under the direct supervision of the providers. The providers have been billing these services under their own name, and not the ACNP's name. I informed them shared services do not apply to procedures, only e/m, and the physicians insist that since they are in the room, directly supervising the ACNP that it is a billable service by the MD. They insist this falls under similar guidelines as being a proctor. They are simply supervising, rarely even touch the patient. Can anyone point me to something from CMS or any other entity that explains proper coding in this scenario? I am uncomfortable billing these services under the MD name, am I wrong? thanks