Positive airway pressure (PAP) therapy is the gold standard treatment for obstructive sleep apnea (OSA) and several other respiratory conditions. The two most commonly prescribed devices — CPAP machines and BiPAP machines — are often confused, but they serve distinct clinical purposes. Understanding the differences helps clinicians, DME suppliers, and sleep center staff guide patients to the right device.
How CPAP Works
CPAP (Continuous Positive Airway Pressure) delivers a single, constant pressure throughout the entire breathing cycle — both during inhalation and exhalation. This constant pneumatic splinting keeps the upper airway open, preventing the collapse that causes apneic events in obstructive sleep apnea.
CPAP machines are prescribed at a fixed pressure (typically 5–20 cm H₂O) determined by an in-lab titration study or estimated by an auto-titrating CPAP (APAP) device. Modern CPAP machines include heated humidification, data tracking (AHI, leak rate, usage hours), and wireless connectivity for compliance monitoring.
Leading CPAP brands: ResMed (AirSense 11, AirSense 10), Philips Respironics (DreamStation 2), Fisher & Paykel (SleepStyle), and Löwenstein Medical (prisma SOFT).
How BiPAP Works
BiPAP (Bilevel Positive Airway Pressure) delivers two distinct pressure levels: a higher IPAP (Inspiratory Positive Airway Pressure) during inhalation and a lower EPAP (Expiratory Positive Airway Pressure) during exhalation. This bilevel approach offers two key advantages:
- It is easier to exhale against lower pressure, making BiPAP more comfortable for patients who find CPAP exhalation difficult.
- The pressure differential provides ventilatory support, assisting patients with hypoventilation syndromes.
Clinical Indications: When to Choose CPAP vs. BiPAP
CPAP is first-line therapy for:
- Obstructive sleep apnea (OSA) — the vast majority of sleep apnea patients
- Upper airway resistance syndrome (UARS)
- Mild-moderate CSA (central sleep apnea) in some protocols
BiPAP machines are indicated for:
- Patients who cannot tolerate CPAP due to high pressure or exhalation difficulty
- Obesity hypoventilation syndrome (OHS / Pickwickian syndrome)
- COPD with hypercapnia (elevated CO₂)
- Neuromuscular diseases (ALS, muscular dystrophy, post-polio) causing nocturnal hypoventilation
- Central sleep apnea and complex sleep apnea syndrome
- Required CPAP pressure above 15 cm H₂O
APAP: The Auto-Adjusting Middle Ground
Auto-titrating CPAP (APAP or AutoPAP) devices automatically adjust pressure breath-by-breath within a set range (typically 4–20 cm H₂O). APAP is increasingly used as the initial prescription for uncomplicated OSA, as it adapts to positional changes, REM sleep, and weight fluctuations. ResMed's AirSense 11 AutoSet and Philips DreamStation Auto CPAP are the market leaders.
Key Accessories for CPAP and BiPAP Therapy
Successful PAP therapy requires more than just the machine. Essential CPAP and BiPAP accessories include:
- Masks: Full face (oronasal), nasal pillows, nasal cradle, pediatric. Mask fit is the single most important factor in therapy adherence.
- Heated humidifiers: Reduce dryness and improve comfort. Most modern devices include integrated humidification.
- CPAP tubing: Standard 6-foot, 15mm or 22mm diameter; heated tubing reduces rainout condensation.
- Filters: Disposable fine filters (monthly) and reusable foam filters (bi-weekly cleaning).
- Cleaning equipment: CPAP mask wipes, brush cleaning kits, and UV sanitizers.
- Chin straps: For mouth breathers using nasal masks.
Medicare and Insurance Coverage for PAP Devices
CPAP and BiPAP devices are covered under Medicare Part B (HCPCS E0601 for CPAP, E0470/E0471 for BiPAP) with a 90-day compliance requirement (usage ≥4 hours/night, ≥70% of nights). Most commercial insurers mirror Medicare criteria. DME suppliers should document compliance data downloads at the 90-day follow-up to ensure continued coverage authorization.
Healix stocks CPAP machines, BiPAP machines, masks, tubing, humidifiers, and accessories from ResMed, Philips Respironics, Fisher & Paykel, and more. View our full respiratory equipment catalog.