Summary: The Centers for Medicare & Medicaid Services modified its plethysmography coverage policy, effective May 15, 2026. Here's what billing teams need to do.
CMS updated its plethysmography coverage policy with a May 15, 2026 effective date. The policy does not list specific CPT or HCPCS codes in the available data — but plethysmography billing touches several pulmonary function and vascular testing codes, and any CMS coverage policy modification in this space deserves immediate attention. If your practice bills for body plethysmography, impedance plethysmography, or vascular plethysmography studies, this change could affect your reimbursement and claim denial rates.
Quick-Reference Table
| Field | Detail |
|---|---|
| Payer | CMS |
| Policy | Plethysmography |
| Policy Code | N/A |
| Change Type | Modified |
| Effective Date | 2026-05-15 |
| Impact Level | Medium |
| Specialties Affected | Pulmonology, Vascular Surgery, Cardiology, Internal Medicine |
| Key Action | Review your plethysmography billing workflows and medical necessity documentation before May 15, 2026 |
CMS Plethysmography Coverage Criteria and Medical Necessity Requirements 2026
The available policy data for this CMS modification does not include the full coverage criteria text. That's a limitation worth naming directly — you should pull the full policy at app.payerpolicy.org/p/cms/165-v1. before May 15, 2026 and compare it against your current workflows.
What we can tell you is this: plethysmography is a diagnostic category that spans several distinct test types, each with different clinical applications and coverage histories. CMS coverage policy modifications in this space typically address medical necessity criteria, appropriate clinical indications, or documentation requirements. Any one of those changes can shift your denial rate overnight if your billing team doesn't update its approach.
Plethysmography falls into three main clinical categories for billing purposes. Body plethysmography measures lung volume and airway resistance — used primarily in pulmonology. Impedance plethysmography evaluates blood flow and venous obstruction. Vascular plethysmography assesses arterial or venous circulation in the extremities. Each carries different medical necessity requirements under CMS, and this modification may affect one, two, or all three.
CMS generally requires that plethysmography be ordered by a treating physician, documented as medically necessary for the diagnosis or management of a specific condition, and performed in a setting that meets Medicare's equipment and personnel standards. Prior authorization is not typically required for plethysmography under Medicare fee-for-service, but Medicare Advantage plans administered under CMS oversight may have separate prior auth requirements. Confirm with each plan before May 15, 2026.
The real issue with CMS coverage policy modifications for diagnostic testing is documentation. CMS auditors look for a clear link between the clinical indication, the ordering physician's rationale, and the specific test performed. If your orders don't reflect that chain clearly, you'll see claim denial activity even when the test itself is clinically appropriate.
If your practice bills plethysmography studies frequently, talk to your compliance officer about what this modification means for your specific payer mix and documentation practices before the effective date.
CMS Plethysmography: What the Policy Modification May Address
Because the full policy text is not included in the available data, this section covers the areas CMS most commonly modifies in diagnostic testing coverage policies. Use this as a framework for reviewing the full policy when you access it directly.
Medical necessity criteria. CMS periodically tightens or clarifies which clinical conditions justify plethysmography. This includes specifying diagnoses that support coverage, requiring that other, simpler tests be performed first, or limiting coverage to patients with documented symptoms rather than screening indications. Check whether the modification changes which ICD-10-CM codes CMS will accept as supporting diagnoses.
Documentation requirements. This is where most practices lose money after a policy change. CMS may now require the ordering physician's notes to include specific language — symptom duration, prior test results, or a clear clinical question the plethysmography is meant to answer. Update your order templates before May 15, 2026.
Place-of-service rules. CMS sometimes modifies coverage policy to restrict certain diagnostic tests to specific settings — for example, limiting coverage to tests performed in a Medicare-enrolled pulmonary function laboratory rather than a general physician office. If this applies here, practices billing from non-qualifying settings will face denials.
Frequency limitations. CMS coverage policy for diagnostic testing often includes limits on how often a test can be billed per patient per year. A modification may tighten existing frequency rules or add new ones. Audit your repeat-order workflows now.
CMS Plethysmography Exclusions and Non-Covered Indications
The policy data available does not specify exclusions. However, CMS has historically excluded plethysmography in the following circumstances — and these patterns persist across most CMS coverage policy frameworks for diagnostic testing.
Screening studies — tests ordered in the absence of symptoms or a specific clinical indication — are not covered. CMS requires a documented clinical reason tied to a patient's current condition. Bilateral studies that lack separate documentation supporting bilateral medical necessity are routinely denied. Plethysmography performed outside an enrolled facility, or by personnel who don't meet Medicare's qualification standards, is not covered.
Review the full policy text to confirm whether this modification adds new exclusions or removes existing ones. If you're not sure which exclusions now apply, your compliance officer should review the updated policy language directly.
Coverage Indications at a Glance
The policy data provided does not include indication-level coverage details. The table below reflects standard CMS coverage patterns for plethysmography — not confirmed content from this specific modification. Verify each row against the full policy before May 15, 2026.
| Indication | Status | Relevant Codes | Notes |
|---|---|---|---|
| Body plethysmography for lung volume measurement in documented pulmonary disease | Typically Covered | Confirm in full policy | Requires physician order and documented clinical indication |
| Impedance plethysmography for suspected deep vein thrombosis | Historically Covered | Confirm in full policy | May require documentation that duplex ultrasound was unavailable or inconclusive |
| Vascular plethysmography for peripheral arterial disease evaluation | Typically Covered | Confirm in full policy | Medical necessity documentation required |
| Plethysmography for screening purposes (no symptoms) | Not Covered | N/A | CMS excludes screening indications across diagnostic testing policies |
| Plethysmography performed outside Medicare-enrolled facility | Not Covered | N/A | Place-of-service requirements apply |
Treat this table as a starting framework. Pull the actual policy text from the source link to confirm every coverage status before billing.
CMS Plethysmography Billing Guidelines and Action Items 2026
These are the steps your billing team should take before May 15, 2026.
| # | Action Item |
|---|---|
| 1 | Pull the full policy text now. Access the policy directly at the CMS source. The available data for this modification is limited. You need the actual policy language to know exactly what changed. Don't wait — give your team enough lead time to update workflows before the effective date. |
| 2 | Audit your current plethysmography orders. Pull the last 90 days of plethysmography orders and review them against CMS medical necessity criteria. Look for orders that lack a documented clinical indication, orders that reference diagnosis codes CMS doesn't support, and orders from physicians who haven't documented the clinical rationale in their notes. |
| 3 | Update your order templates. If the modification changes documentation requirements — which is common in CMS diagnostic testing policy updates — your order templates need to reflect the new requirements before May 15, 2026. Work with your medical director to update the templates and communicate the changes to ordering physicians. |
| 4 | Review your ICD-10-CM diagnosis code pairings. CMS coverage policy changes for diagnostic tests often include updated lists of supporting diagnoses. Make sure your charge capture system uses diagnosis codes that CMS recognizes as supporting medical necessity for plethysmography. Wrong diagnosis code pairings are one of the most common causes of claim denial in this category. |
| 5 | Check your Medicare Advantage contracts separately. This modification covers CMS fee-for-service rules. Your Medicare Advantage plans may have their own prior authorization requirements or coverage policies for plethysmography billing. Don't assume fee-for-service rules transfer automatically to managed Medicare. |
| 6 | Set a post-effective-date claims audit. After May 15, 2026, pull your first 30 days of plethysmography claims and review denial rates by indication and diagnosis code. If you see a spike in claim denial activity, you'll catch it early enough to fix documentation before it becomes a revenue problem. |
| 7 | Loop in your compliance officer. If you bill plethysmography at high volume — or if your practice relies on it for a significant share of pulmonology or vascular reimbursement — your compliance officer should review this modification directly. A policy change that shifts medical necessity criteria or documentation requirements can expose you to audit risk on retrospective claims if your documentation doesn't hold up. |
| Previous Version | Current Version |
|---|---|
| Coverage is considered experimental and investigational for all indications | Coverage is considered medically necessary when specific criteria are met |
| Prior authorization is not required | Prior authorization is required for initial treatment |
| Documentation must include clinical history | Documentation must include clinical history |
| Re-review every 24 months | Re-review every 12 months with updated clinical documentation |
CPT, HCPCS, and ICD-10 Codes for Plethysmography Under This Policy
The policy data provided for this CMS modification does not list specific CPT, HCPCS, or ICD-10 codes. Including fabricated codes would be worse than saying nothing — it would send your billing team in the wrong direction.
When you access the full policy, look for codes in the following categories based on how plethysmography is typically coded under Medicare:
- Pulmonary function and body plethysmography codes in the CPT 9400x range
- Vascular and impedance plethysmography codes in the CPT 9300x–9399x range
- ICD-10-CM codes for COPD, asthma, pulmonary fibrosis, peripheral arterial disease, and venous thromboembolism — these are the most common supporting diagnosis categories
Once you have the full policy, update your charge capture with the exact codes CMS specifies. Cross-reference against your current superbill and encounter form to catch any gaps.
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