Hello -
this is what we follow for the 94640
Chapter 11
National Correct Coding Initiative Edits
Revision Date (Medicare): 1/1/2019
Page XI-25 thru XI-26
8. CPT code 94640 (pressurized or non-pressurized inhalation treatment for acute airway obstruction...) describes either treatment of acute airway obstruction with inhaled medication or the use of an inhalation treatment to induce sputum for diagnostic purposes. CPT code 94640 shall only be reported once during an episode of care regardless of the number of separate inhalation treatments that are administered. If CPT code 94640 is used for treatment of acute airway obstruction, spirometry measurements before and/or after the treatment(s) shall not be reported separately. It is a misuse of CPT code 94060 to report it in addition to CPT code 94640. The inhaled medication may be reported separately.
An episode of care begins when a patient arrives at a facility for treatment and terminates when the patient leaves the facility. If the episode of care lasts more than one calendar day, only one unit of service of CPT code 94640 shall be reported for the entire episode of care.
If a patient receives inhalation treatment during an episode of care and returns to the facility for a second episode of care that also includes inhalation treatment on the same date of service, the inhalation treatment during the second episode of care may be reported with modifier 76 appended to CPT code 94640.
If inhalation drugs are administered in a continuous treatment or a series of “back-to-back” continuous treatments exceeding one hour, CPT codes 94644 (continuous inhalation treatment with aerosol medication for acute airway obstruction; first hour) and 94645 (...; each additional hour) may be reported instead of CPT code 94640.
Link to National Correct Coding Initiative Edits (NCCI edits)
https://www.cms.gov/Medicare/Coding/NationalCorrectCodInitEd/index.html