Use code 94664 when teaching patients how to use a nebulizer or inhaler.  The CPT® definition is:

Demonstration and/or evaluation of patient utlization of an aerosol generator, nebulizer, metered dose inhaler or IPPB device.  The service may only be reported once/day. It is not a code defined by time. Some payers may have frequency edits built into their systems to prevent payment of the instruction more than once in a time period. 

It is an active code in the Medicare Fee Schedule.  It has a PC/TC status indicator of 5, incident to.  That means, a staff member may perform the service incident to a physician.  Incident to is a Medicare concept.  (Review the Codapedia article on incident to.)  In short, the physician must order the service and be present in the suite of offices when the service is provided to a Medicare patient. The 2009 National Medicare Fee Schedule amount is just under $15.

When provided on the same day as an office visit, CPT® rules do not require a modifier.  Some payer's claims editing systems, however, will require a 25 modifier on the E/M service performed on the same day.

Three common diagnosis codes used when submitting this service are 496, chronic airway obstruction, 466, acute bronchitis, and 493.90, asthma, unspecified.