According to a CMS bulletin, for the purpose of processing claims for replacement of essential accessories for CPAP, the medical necessity for the beneficiary-owned base CPAP device or RAD is assumed to have been established.

This does not mean that the Centers for Medicare & Medicaid Services (CMS) or its contractors cannot determine that the payments for the equipment were inappropriate based on additional information or investigations related to auditing previously processed Medicare claims.  This assumption is merely made so that initial claims for essential accessories used with a beneficiary-owned CPAP device or RAD purchased by Medicare following 13 months of continuous use can be processed timely to ensure beneficiary access to these items.

Read the full bulletin at cms.gov