Question: Our pulmonologist is interested in performing a lung compliance study on a patient, but we can't determine if it's payable in her situation. What are the criteria? Codify Subscriber Answer: The answer depends on which insurer you plan to bill, but many Medicare payers won't cover lung compliance studies until you've already performed other pulmonary function tests and you still need more information even after getting those results. For instance, Noridian Medicare's policy, which was updated in December 2017, states, "Lung compliance studies are performed only when all other PFTs give equivocal results or results which must be confirmed by additional lung compliance testing. Lung compliance measures the elastic recoil/stiffness of the lungs. It is more invasive than other PFTs, because the patient is required to swallow an esophageal balloon." If you do meet the criteria for reporting lung compliance studies, you'll report 94750 (Pulmonary compliance study (eg, plethysmography, volume and pressure measurements) for the service.