If you've been diagnosed with a sleep breathing disorder, your doctor has likely mentioned either CPAP or BiPAP therapy. Both devices deliver pressurized air to keep your airway open during sleep, but they work differently — and Medicare treats them differently, too. Here's what you need to know to understand your options.

How CPAP Works

CPAP stands for Continuous Positive Airway Pressure. It delivers a single, constant pressure of air throughout the entire breathing cycle — both inhalation and exhalation. Think of it as a continuous column of air that acts as a pneumatic splint, preventing your airway from collapsing.

CPAP is the most prescribed PAP device in the world and is the first-line treatment for obstructive sleep apnea (OSA) — a condition where the muscles of the throat relax during sleep, causing the airway to narrow or fully close.

The pressure setting is prescribed by your doctor based on your sleep study results. Most CPAP machines also offer an "auto" or "APAP" mode (automatic positive airway pressure) that adjusts the pressure in real time based on your breathing patterns.

How BiPAP Works

BiPAP stands for Bilevel Positive Airway Pressure. Unlike CPAP, BiPAP delivers two different pressure levels:

  • IPAP (Inspiratory Positive Airway Pressure) — higher pressure when you inhale
  • EPAP (Expiratory Positive Airway Pressure) — lower pressure when you exhale

This bilevel design makes it easier to breathe out against the pressure, which is why BiPAP is often prescribed for patients who find it difficult to exhale against a constant CPAP pressure. It also makes BiPAP more effective for conditions that affect breathing in both directions.

Who Needs CPAP?

CPAP is typically prescribed for:

  • Obstructive sleep apnea (OSA) — the most common sleep breathing disorder
  • Patients with mild to moderate apnea who tolerate constant pressure well
  • Patients who don't have significant COPD, neuromuscular disease, or hypercapnia

Most people with OSA start with CPAP. It's simpler to use, generally less expensive, and effective for the vast majority of obstructive apnea patients.

Who Needs BiPAP?

BiPAP is typically prescribed when:

  • The patient cannot tolerate the exhalation pressure of CPAP (a condition sometimes called "expiratory pressure intolerance")
  • The patient has central sleep apnea (CSA) — where the brain fails to signal the breathing muscles properly
  • The patient has both obstructive and central apnea (complex or "mixed" apnea)
  • The patient has COPD, congestive heart failure, or another condition causing hypoventilation
  • The patient has a neuromuscular disease (ALS, muscular dystrophy) affecting breathing muscle strength
  • The patient has obesity hypoventilation syndrome

BiPAP is also used in clinical settings for acute respiratory distress as non-invasive ventilation (NIV) support.

Medicare Coverage: CPAP vs. BiPAP

Medicare covers both devices under Part B as durable medical equipment — but with different documentation requirements and coverage thresholds.

CPAP Coverage

  • Requires a qualifying sleep study showing an apnea-hypopnea index (AHI) ≥ 5
  • Medicare covers a 3-month trial period followed by a face-to-face re-evaluation
  • Compliance data must show the device is being used at least 4 hours/night for 70% of nights over a 30-day period
  • Coverage continues if compliance is demonstrated at the 90-day check
  • Reimbursed under HCPCS code E0601 (CPAP) or E0562 (humidifier) as capped rental

BiPAP Coverage

  • BiPAP without backup rate (E0470) requires documented CPAP failure or a diagnosis (e.g., COPD, CSA) requiring bilevel pressure
  • BiPAP with backup rate (E0471 — also called BiPAP ST) requires documentation of a condition causing hypoventilation
  • The 90-day compliance requirement applies to BiPAP for OSA as well
  • For ventilatory support indications, compliance rules differ — check with your supplier

The key takeaway: switching from CPAP to BiPAP requires a new prescription, updated clinical documentation, and often prior authorization. Don't assume your supplier will automatically substitute one for the other.

See detailed Medicare coverage rules for CPAP and BiPAP in our Coverage Hub →

Machine Maintenance: CPAP vs. BiPAP

Both devices require regular cleaning and supply replacement. Medicare covers replacement supplies on a schedule:

  • Mask cushions/pillows — 2 per month
  • Full mask or nasal interface — 1 every 3 months
  • Tubing — 1 every 3 months
  • Disposable filters — 2 per month
  • Headgear and chinstrap — 1 every 6 months

BiPAP machines themselves are more expensive than CPAP machines, so you may pay a higher 20% coinsurance during the rental period.

Finding the Right Supplier

Whether you need CPAP or BiPAP, your supplier should be accredited, accept Medicare assignment, and have respiratory therapists on staff who can help with mask fitting and compliance tracking. Compliance data — downloaded from your device — is required to continue coverage, so working with a supplier who actively monitors your compliance is a real advantage.

Browse Medicare-accredited CPAP and BiPAP suppliers near you →

Frequently Asked Questions

Can I request a BiPAP instead of a CPAP?

You can discuss this with your prescribing doctor. However, Medicare will only cover BiPAP with appropriate clinical documentation. If you have difficulty exhaling against CPAP pressure, tell your doctor — this is a documented indication for BiPAP.

Is BiPAP harder to use than CPAP?

Many patients find BiPAP more comfortable because the lower exhalation pressure feels more natural. Both devices require the same basic care and mask fitting process.

Does my Medicare Advantage plan cover BiPAP the same way?

Not necessarily. MA plans can impose stricter prior auth requirements or different cost-sharing than Original Medicare. Always check your plan's DME benefit before ordering.