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Carbogen Inhalation Therapy
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This Clinical Policy Bulletin addresses the use of carbogen (5% CO2 / 95% O2) inhalation therapy and states Aetna's coverage stance for various indications; intended for providers submitting claims or prior authorization requests to Aetna.
No material clinical or coverage changes in this revision.
Coverage Criteria for Carbogen Inhalation Therapy
Experimental and Investigational indications
Carbogen inhalation therapy is considered experimental and investigational for the following indications because effectiveness has not been established:
Carbogen inhalation therapy is designated experimental and investigational for multiple indications because peer‑reviewed evidence has not established effectiveness. The policy lists specific conditions for which carbogen is considered investigational, including bladder cancer, central retinal artery occlusion, cervical cancer, head and neck cancers, optic nerve damage/degeneration, prostate cancer, retinal artery occlusion, seizures, stroke, and sudden hearing loss. Corresponding ICD‑10 diagnosis code ranges for these noncovered indications are provided in the policy (e.g., malignancy ranges C00.x–C76.x, retinal vascular occlusions H34.x, optic nerve disorders H46–H47, sudden idiopathic hearing loss H91.20–H91.23, epilepsy/seizures G40.x, and cerebrovascular disease I60–I69).
The policy states there is insufficient evidence to support carbogen inhalation as an effective therapy for retinal artery occlusion; case reports and small series have not established benefit and the document explicitly notes that carbogen has not been proven effective for RAO. For cervical cancer, randomized and nonrandomized studies evaluating carbogen with nicotinamide (CON) did not demonstrate clear improvements in survival or local control, and major reference sources (UpToDate and NCCN) do not list carbogen inhalation as a therapeutic option, so effectiveness for cervical cancer is not established.
For idiopathic sudden sensorineural hearing loss (SHL), the policy explains that clinical studies of carbogen inhalation have shown no improvement in recovery rates compared with standard care or the rate of spontaneous recovery. A systematic review concluded carbogen inhalation is no more effective than heparin or standard care, and steroid therapy remains the only medical treatment with demonstrated benefit in selected patients with idiopathic SHL.
Additional evidence notes reiterate insufficient data for retinal artery occlusion, where isolated case reports have not established reliable treatment benefit and routine use of carbogen is unsupported. In cervical cancer, trials of carbogen with nicotinamide did not show superior survival or control and guideline sources (UpToDate, NCCN) do not recommend carbogen inhalation as a therapeutic option; therefore its effectiveness for cervical cancer remains unestablished.
Coding and Diagnosis Mappings
| C00.0 - C00.9 | Malignant neoplasm of lip |
| C01 - C06.9 | Malignant neoplasm of oral cavity |
| C07 - C08.9 | Malignant neoplasm of other and unspecified major salivary glands |
| C11.0 - C11.9 | Malignant neoplasm of nasopharynx |
| C30.0 - C31.9 | Malignant neoplasm of nasal cavities, middle ear, and accessory sinuses |
| C32.0 - C32.9 | Malignant neoplasm of larynx |
| C43.0 - C43.4 | Malignant melanoma of head and neck |
| C53.0 - C53.9 | Malignant neoplasm of cervix uteri |
| C61 | Malignant neoplasm of prostate |
| C67.0 - C67.9 | Malignant neoplasm of bladder |
Provider Actions, Prior Authorization & Billing Notes
Prior authorization / coding note
No specific CPT or HCPCS codes exist for carbogen inhalation therapy. When submitting claims, providers should document the clinical indication and relevant ICD-10 diagnosis codes. The ICD-10 diagnosis ranges listed in this policy correspond to the indications for which carbogen is considered experimental/investigational and may be subject to claim denial.
- No CPT/HCPCS code specific to carbogen inhalation therapy.
- ICD-10 codes not covered for indications listed in this CPB (not all-inclusive): C00.0–C00.9, C01–C06.9, C07–C08.9, C11.0–C11.9, C30.0–C31.9, C32.0–C32.9, C43.0–C43.4, C53.0–C53.9, C61, C67.0–C67.9, C76.0, D03.0–D03.4, G40.001–G40.919, H34.00–H34.9, H46.00–H47.9, H91.20–H91.23, I60.00–I69.998, I97.810–I97.821, S04.011+–S04.019+
Prior authorization not specified in excerpt
Prior authorization is not specified within the excerpt of this Clinical Policy Bulletin. Providers should check member-specific benefit documents or contact Aetna provider services for any plan-specific prior authorization requirements before initiating carbogen therapy.
Step therapy context
Standard treatment for idiopathic sudden sensorineural hearing loss (SHL) is corticosteroid therapy; carbogen inhalation has not been shown to provide additional benefit over standard care or spontaneous recovery. Clinicians should follow established treatment guidelines and consider steroids as first-line therapy for SHL rather than carbogen.
- Steroid therapy is the only medical treatment proven to have significant benefit in selected patients with idiopathic SHL.
- Clinical studies and a systematic review (Hender et al., 2002) found no improvement with carbogen compared with standard care.
Experimental/Investigational — denial risk
Claims for carbogen inhalation therapy for the conditions listed in this policy may be denied as experimental and investigational. Providers should ensure documentation supports medical necessity and be prepared for possible denial when treating these indications.
- Listed experimental/investigational indications include: bladder cancer; central retinal artery occlusion; cervical cancer; head and neck cancers; optic nerve damage/degeneration; prostate cancer; retinal artery occlusion; seizures; stroke; sudden hearing loss.
Informational / policy scope
This Clinical Policy Bulletin is informational and intended to assist in administering benefits; it does not constitute an offer of coverage. Providers remain responsible for treatment decisions and should consult plan documents for coverage specifics and authorization procedures.
Background on Carbogen and Mechanism
Carbogen is a premixed gas consisting of 5% carbon dioxide and 95% oxygen. It is proposed to improve tissue oxygenation by combining increased arterial oxygen content with CO2‑induced vasodilation to enhance local blood flow and oxygen delivery.
Definitions
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