Three acronyms, one goal: keep your airway open with air pressure. Here’s how they differ and what the guidelines say.
How each one works
| CPAP | APAP (auto-CPAP) | BiPAP / bilevel | |
|---|---|---|---|
| Pressure | One fixed pressure | Varies between a min and max | Two pressures: IPAP (in) and EPAP (out) |
| Set by | Prescription, often from an in-lab titration | Prescription with pressure limits | Prescription with IPAP and EPAP |
| AASM view for routine adult OSA | Recommended (strong) | Recommended (strong) | CPAP or APAP suggested over bilevel |
| Medicare HCPCS | E0601 | E0601 | E0470 (no backup rate), E0471 (backup rate) |
| Medicare for OSA | Covered when criteria are met | Covered when criteria are met | E0470 only after E0601 tried and proven ineffective; E0471 not covered for OSA |
| Example machine | ResMed AirSense 11 (CPAP mode) | ResMed AirSense 11 AutoSet | ResMed AirCurve 11 VAuto |
Sources: AASM 2019 PAP guideline, AASM titration guideline, CMS LCD L33718, AirSense 11 user guide.
What the AASM recommends
From the AASM’s 2019 clinical practice guideline on PAP for adult OSA (Patil et al., J Clin Sleep Med 2019):
| Recommendation | Strength |
|---|---|
| Use PAP, vs no therapy, for OSA with excessive sleepiness | Strong |
| Start PAP with either APAP at home or in-lab titration in adults with OSA and no significant comorbidities | Strong |
| Use either CPAP or APAP for ongoing treatment of OSA | Strong |
| Use CPAP or APAP over bilevel in routine OSA treatment | Conditional |
| Give education when starting PAP | Strong |
| Use telemonitoring-guided interventions early in therapy | Conditional |
In short: CPAP and APAP are equal first choices. Bilevel isn’t the default for plain OSA.
When bilevel comes in
The AASM’s manual titration guideline says that if a patient is “uncomfortable or intolerant of high pressures on CPAP, the patient may be tried on BPAP”, and that if obstructive events continue at 15 cmH₂O of CPAP during titration, the patient may be switched to BPAP. It recommends an IPAP–EPAP difference of 4 to 10 cmH₂O, and a maximum IPAP of 30 cmH₂O for patients 12 and older (AASM titration guideline).
Bilevel devices are also used for conditions other than OSA, such as neuromuscular disease, central sleep apnea and hypoventilation. Those have their own Medicare rules, explained in BiPAP and ASV: Medicare rules.
APAP vs CPAP in practice
Most modern home machines do both. The AirSense 11 runs CPAP mode or AutoSet, each at 4–20 cmH₂O, with optional EPR, which lowers pressure by up to 3 cmH₂O on exhale (AirSense 11 user guide). EPR isn’t true bilevel, but it can ease breathing out. Your clinician decides the mode and the limits. The AASM’s 2019 guideline supports starting with APAP at home for adults without significant comorbidities.
Medicare and cost
- CPAP and APAP are both billed as E0601 and follow the same rules: a 90-day trial, and use of at least 4 hours a night on 70% of nights in a consecutive 30-day period (Medicare CPAP guide).
- For OSA, a bilevel without backup rate (E0470) is covered only if CPAP was tried and proven ineffective. A bilevel with backup rate (E0471) isn’t covered for OSA (LCD L33718).
- Cash prices for auto CPAPs are in CPAP cost without insurance. The AirSense 11 AutoSet was $1,004 at cpap.com. HHZ didn’t verify current US bilevel prices for this guide.
Which one fits you
| Situation | Usual starting point |
|---|---|
| New OSA diagnosis, no major other conditions | APAP at home or CPAP after titration |
| Can’t tolerate high CPAP pressure | Ask about EPR first, then bilevel |
| Central sleep apnea, hypoventilation, neuromuscular disease | Specialist assessment; bilevel or ASV may be considered |
Verdict
For plain obstructive sleep apnea, start with CPAP or APAP. The AASM treats them as equals. Bilevel is the step up when high pressure can’t be tolerated or CPAP fails, and Medicare covers it for OSA only after CPAP has been tried. Choosing between modes is a prescription decision; the machine just follows it.
Related: AirSense 11 settings explained, high AHI on CPAP, best auto CPAP machine.
Model reviews: AirSense 11 AutoSet, AirCurve 11 VAuto.