CPAP vs BiPAP: What's the Difference?
Published 2026-07-20
CPAP and BiPAP are the two most common forms of positive airway pressure (PAP) therapy, and while they look similar, they work differently enough that one usually isn't a substitute for the other without a physician's sign-off.
CPAP — one constant pressure
CPAP (Continuous Positive Airway Pressure) delivers a single, steady pressure throughout the breathing cycle — the same pressure whether you're inhaling or exhaling. It's the standard first-line therapy for obstructive sleep apnea (OSA), where the goal is simply to keep the airway open with steady pressure.
BiPAP — two pressures, timed to your breath
BiPAP (Bilevel Positive Airway Pressure) delivers a higher pressure on inhale (IPAP) and a lower pressure on exhale (EPAP), which makes exhaling against the machine noticeably easier. It's typically prescribed when CPAP pressure needs are high, when a patient struggles to exhale comfortably against a single fixed pressure, or for conditions beyond straightforward OSA — such as COPD overlap, certain neuromuscular conditions, or central sleep apnea — where more nuanced pressure support helps.
Quick comparison
| CPAP | BiPAP | |
|---|---|---|
| Pressure delivery | Single fixed pressure | Separate inhale/exhale pressures |
| Typical use | Standard OSA | High-pressure needs, COPD overlap, some neuromuscular conditions |
| Comfort on exhale | Same pressure throughout | Lower pressure on exhale, generally easier |
| Cost | Lower | Higher |
Which one is right for you?
This is a decision for your sleep physician based on your diagnostic study, not something to self-select based on comfort alone. If you've been prescribed CPAP but find it hard to exhale against the pressure, that's worth raising at your next follow-up — it may be a sign BiPAP or a pressure-relief feature (like EPR) is worth discussing.