CPAP vs APAP vs BiPAP: What Is the Difference?

CPAP: one steady pressure

CPAP delivers a single fixed pressure all night. The pressure is set by your clinician, usually based on an in-lab titration study or data from an auto-adjusting machine. It is simple, effective and has decades of evidence behind it for obstructive sleep apnea.

APAP: auto-adjusting pressure

APAP, sometimes called auto CPAP or AutoSet, adjusts pressure breath by breath within a range set by your clinician. When it senses airway narrowing, snoring or flow limitation, it raises pressure; when things are stable, it lowers it.

The AASM 2019 guideline recommends that adults with obstructive sleep apnea and no significant other conditions can start therapy either with APAP at home or with an in-lab titration, and that either CPAP or APAP can be used for ongoing treatment. Many new users now start on APAP.

BiPAP: two pressures

Bilevel PAP, often called BiPAP (a Philips trademark that has become a common name), uses a higher pressure when you breathe in (IPAP) and a lower pressure when you breathe out (EPAP). It can help people who need high pressures, who cannot tolerate CPAP, or who have conditions that affect breathing such as some lung diseases, neuromuscular conditions or hypoventilation.

Some bilevel machines include a backup breathing rate for people whose breathing drive is reduced. Those are used for specific conditions under specialist care.

Other devices you might hear about

Adaptive servo-ventilation (ASV) is a specialised device for certain types of central sleep apnea. It is not suitable for everyone; for example, it is not recommended for people with heart failure with reduced ejection fraction and central sleep apnea, based on a large trial that found harm in that group. Your specialist will decide if it is appropriate.

How insurers approach it

For obstructive sleep apnea, Medicare covers CPAP or APAP first. Bilevel without a backup rate is generally covered only after CPAP has been tried and documented as ineffective despite proper mask fit and appropriate settings. Private insurers often follow similar rules. If you are struggling on CPAP, the first steps are usually fit, comfort settings and pressure review rather than an immediate switch.

Which is best for you?

There is no universally better machine. The right one is the one that keeps your airway open, that you can wear comfortably all night, and that suits your medical conditions. Share your experience and data honestly with your clinician; that is what drives good decisions.