Revised Certifications of Medical necessity of Oxygen

Contractors encourage treating physicians to file timely, revised CMNs or Form CMS-484s through the supplier if their order for oxygen changes.

A revised CMN is necessary when:

1. The prescribed maximum flow rate changes from one of the following categories to another: (a) less than 1 LPM, (b) 1-4 LPM, (c) greater than 4 LPM. If the change is from category (a) or (b) to category (c), a repeat blood gas study with the beneficiary on 4 LPM must be performed within 30 days prior to the start of the greater than 4LPM flow.

2. Portable oxygen is added subsequent to initial certification of a stationary system. In this situation, there is no requirement for a repeat blood gas study unless the initial qualifying study was performed during sleep, in which case a repeat blood gas study must be performed while the patient is at rest (awake) or during exercise.

3. The initial certification specified an estimated length of need that is less than lifetime and the physician wants to extend the certification.

4. There is a new treating physician (no new testing is required).

Contractors do not adjust payments on oxygen claims unless a revised certification documents the necessity for the change. Contractors timely adjust payments, if necessary, for services since the oxygen prescription was changed.