CMS NCD 43 Modified: Oxygen and Carbon Dioxide Therapy for Inner Ear Disease — What Billing Teams Need to Know

CMS has issued a modification to National Coverage Determination (NCD) 43, which governs coverage policy for oxygen and carbon dioxide inhalation therapy used in the treatment of inner ear conditions. The Centers for Medicare & Medicaid Services — the federal agency administering Medicare and Medicaid — maintains a firm non-coverage position on this therapy, designating it as not reasonable and necessary. Billing teams submitting claims for this treatment under Medicare should expect denial, and practices offering this service need clear documentation protocols in place.

What NCD 43 Covers: CMS Policy on Oxygen Therapy for Inner Ear Disease

NCD 43 addresses a very specific clinical scenario: the use of inhaled oxygen (95%) and carbon dioxide (5%) as a therapeutic intervention for inner ear disorders. The conditions most commonly associated with this treatment include endolymphatic hydrops — a condition involving fluid imbalance in the inner ear — and fluctuant hearing loss, which is characterized by hearing that varies in degree over time.

CMS's position is unambiguous. The agency states directly that this therapy "is not reasonable and necessary," citing that "the therapeutic benefit deriving from this procedure is highly questionable." This language is significant from a billing standpoint. When CMS characterizes a treatment as not reasonable and necessary, it triggers a statutory non-coverage determination under Medicare, meaning claims will be denied regardless of clinical documentation provided.

This is not a coverage determination based on incomplete evidence pending further review — CMS has made an affirmative finding against coverage. That distinction matters for how your team communicates with patients and manages Advance Beneficiary Notices (ABNs).

How This Affects Medicare Billing for Endolymphatic Hydrops and Fluctuant Hearing Loss

Practices treating patients with Ménière's disease, endolymphatic hydrops, or fluctuant sensorineural hearing loss may encounter patient or provider interest in oxygen/CO₂ inhalation therapy, particularly in cases where conventional treatments have not provided relief. This is sometimes marketed or discussed in clinical literature as a vasodilatory approach to improving inner ear circulation.

Under NCD 43, no Medicare reimbursement is available for this therapy. If a provider believes the treatment is clinically warranted and a patient wishes to proceed, the practice must issue a properly executed ABN before the service is rendered. The ABN informs the patient that Medicare will not pay, and that the patient accepts financial responsibility if they choose to proceed.

Failure to issue an ABN in these circumstances leaves the practice unable to bill the patient for the service — meaning the work is rendered without compensation. This is a straightforward but easily missed compliance gap for ENT and audiology practices.

CMS Medical Necessity Standard: Why "Reasonable and Necessary" Matters

The phrase "reasonable and necessary" is the cornerstone of Medicare coverage. Under Section 1862(a)(1)(A) of the Social Security Act, Medicare does not cover items or services that are not reasonable and necessary for the diagnosis or treatment of illness or injury. When CMS codifies this determination in an NCD, it applies nationally — individual Medicare Administrative Contractors (MACs) cannot override it with a Local Coverage Determination (LCD) that grants broader coverage.

For oxygen/CO₂ therapy for inner ear disease, this means there is no pathway to Medicare reimbursement at the local level. A provider cannot argue that their specific MAC has different guidance, because the NCD takes precedence. Billing teams sometimes encounter confusion on this point when reviewing MAC websites, so the hierarchy is worth reinforcing internally: NCDs override LCDs when both exist on the same topic.

The evidentiary basis for CMS's determination reflects the agency's assessment that clinical evidence for the therapeutic benefit of this approach is insufficient. This aligns with how CMS has approached other vasodilatory and inhalation-based therapies where robust randomized controlled trial data is lacking.

Affected Codes

This policy does not list specific CPT or HCPCS codes. Per the official NCD 43 policy document, no procedure codes are enumerated under this determination.

For billing teams, this means the non-coverage determination applies to the procedure itself as described — oxygen (95%) and carbon dioxide (5%) inhalation therapy for inner ear disease — regardless of which code might be used to report it. If your practice uses a miscellaneous or unlisted code to bill this therapy to Medicare, expect denial based on NCD 43.

Related ICD-10 Diagnosis Codes (conditions addressed by this policy):

Note: The absence of specific codes in the policy does not limit its scope. NCD 43 applies to the procedure as described regardless of the diagnosis code submitted.

What Your Billing Team Should Do