CPAP vs BiPAP — What’s the Difference and Which Do You Need?
By Yash, RRT — Licensed Respiratory Therapist & Owner, MyRespCo
CPAP and BiPAP are both positive airway pressure therapies for obstructive sleep apnea — but they work differently, are prescribed for different reasons, and cost differently. If you've been told you need one but aren't sure which, this guide explains exactly how a Licensed Respiratory Therapist thinks about this decision.
What Is CPAP?
CPAP stands for Continuous Positive Airway Pressure. It delivers a single, fixed (or auto-adjusting) pressure throughout your entire breath cycle — both when you inhale and when you exhale. That constant pressure acts as a pneumatic splint, keeping your airway open so apneas and hypopneas cannot occur.
CPAP is the first-line treatment for obstructive sleep apnea for the vast majority of patients. If your physician has prescribed CPAP, that is what you need unless there's a specific clinical reason to escalate to BiPAP.
What Is BiPAP?
BiPAP stands for Bilevel Positive Airway Pressure. It delivers two distinct pressures: a higher pressure during inhalation (IPAP — inspiratory positive airway pressure) and a lower pressure during exhalation (EPAP — expiratory positive airway pressure). The pressure drops when you exhale, making breathing out significantly easier — particularly at higher pressure settings.
When Is BiPAP Prescribed Instead of CPAP?
BiPAP is typically prescribed when one of the following applies:
- CPAP intolerance: Patient cannot tolerate CPAP pressure — particularly the difficulty exhaling against a constant high pressure. BiPAP's pressure relief on exhalation resolves this for many patients.
- High required pressure: Patients requiring CPAP pressures above 15 cmH₂O often benefit from BiPAP's exhalation pressure relief.
- COPD with hypoventilation: BiPAP provides pressure support that assists the breathing effort itself, not just airway patency. This is critical for COPD patients with CO₂ retention.
- Complex or central sleep apnea: Some patients have central apnea components (brain fails to signal breathing) in addition to obstructive events. BiPAP with backup rate (BiPAP-ST) can treat both.
- Severe OSA (AHI 30+): High-severity patients sometimes respond better to bilevel therapy, though this is individually assessed.
CPAP vs BiPAP — Side by Side
| Feature | CPAP | BiPAP |
|---|---|---|
| Pressures | One (single or auto) | Two (IPAP + EPAP) |
| Exhalation comfort | Standard | Significantly easier |
| Primary indication | Obstructive sleep apnea | OSA + CPAP intolerance, COPD, complex apnea |
| Prescription required | Yes | Yes |
| Cost (refurbished) | Lower | Slightly higher |
| Data recording | Yes — CDL/DOT capable | Yes — CDL/DOT capable |
| Most common machines | ResMed AirSense 10/11, S9 | ResMed AirCurve 10 VAuto |
Which Should You Buy?
Buy what your physician prescribed. If your prescription says CPAP, buy CPAP. If it says BiPAP or BPAP, buy BiPAP. If you're on CPAP and struggling with exhalation comfort or high pressure discomfort, an RT Consultation is the right next step before deciding to switch — there are CPAP settings (EPR, pressure relief) that solve this for many patients without requiring a BiPAP upgrade.
If you're unsure whether your symptoms suggest CPAP intolerance or whether BiPAP might be appropriate, our $49.99 RT Consultation gives you clinical perspective before you spend money on the wrong equipment.
→ Shop Refurbished ResMed AirSense 10 AutoSet CPAP
→ Shop Refurbished ResMed AirCurve 10 VAuto BiPAP
→ Book an RT Consultation — $49.99
→ Complete Refurbished CPAP Buyer's Guide