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Auto CPAP vs Fixed CPAP: what's the difference?
When your doctor prescribes continuous positive airway pressure (CPAP) therapy, they must choose between two main device types: fixed CPAP and auto CPAP (APAP). Both treat sleep apnea effectively, but they work differently. This guide explains the differences, respective advantages, and which type suits which patient profile.
How does a fixed CPAP work?
A fixed-pressure CPAP delivers a constant air pressure set in advance by your doctor following a titration study. Throughout the entire night, the device blows at exactly that pressure - whether you are in light sleep, deep sleep or REM sleep. The pressure remains identical regardless of your body position, alcohol intake or seasonal nasal congestion.
This mode is simple, robust and has been proven over decades. It is well suited to patients whose pressure needs are stable and predictable.
How does an auto CPAP (APAP) work?
An automatic CPAP (APAP) measures your upper airway resistance in real time and adjusts the delivered pressure continuously throughout the night. If your airways are open and clear, the device lowers pressure for comfort. If it detects apneas, hypopneas or snoring, it increases pressure just enough to eliminate those events.
This continuous adaptation offers concrete benefits: the average pressure delivered is often lower than that of a fixed CPAP set to its maximum, improving comfort and reducing mask leaks. Patients who struggle to exhale against a high fixed pressure often find auto CPAP far more tolerable.
Comparison table: fixed CPAP vs auto CPAP
| Criterion | Fixed CPAP | Auto CPAP (APAP) |
|---|---|---|
| Pressure | Constant (e.g. 8 cmH₂O all night) | Variable to meet needs (e.g. 6-12 cmH₂O) |
| Algorithm | None - pressure set by physician | Proprietary algorithm (AutoSet, DreamMapper…) |
| Adapts to variations | No | Yes - position, alcohol, nasal congestion |
| Exhalation comfort | Moderate if pressure is high | Better (lower average pressure) |
| Data reporting | Limited (overall AHI) | Detailed (pressure curve, leaks, AHI) |
| Titration required | Yes, in lab or ambulatory | Often no - pressure range set by physician |
| Best for | Stable, known pressure needs | Most patients, variable pressure needs |
| Indicative price | From ~€400 | From ~€550 |
Who should choose a fixed CPAP?
- Patients with a stable, well-established titration pressure
- Simple obstructive apnea with little nocturnal variability
- Patients who tolerate their prescribed pressure well
- Situations where budget is a primary constraint
Who should choose an auto CPAP?
- First-time CPAP users (optimal pressure not yet determined)
- Patients whose pressure needs vary by sleep position (back sleepers who snore)
- Patients whose AHI fluctuates with alcohol intake or nasal congestion
- Patients who struggle to exhale against a high fixed pressure
- The majority of adults with obstructive sleep apnea
Top auto CPAP devices at VivaRespire
VivaRespire offers a selection of the best auto CPAP devices available for direct purchase, without convention, with delivery across Belgium:
- ResMed AirSense 11 AutoSet - the benchmark AutoSet algorithm, connected via myAir
- Philips DreamStation 2 - compact, detailed data, DreamMapper app
- Löwenstein Prisma SMART Auto - prismaLINE algorithm, very quiet
- SEFAM EcoStar - reliable French device, excellent value
Top fixed CPAP devices at VivaRespire
- ResMed AirSense 11 Elite - connected fixed version of the AirSense 11
- Löwenstein Prisma SOFT - quiet, reliable fixed CPAP
Browse our full range: auto CPAP and fixed CPAP.
RIZIV/INAMI convention or buy from VivaRespire?
In Belgium, the RIZIV/INAMI convention gives you access to a CPAP device on loan from an accredited centre - you never own the device and remain dependent on the provider. VivaRespire offers direct purchase: you own your device, choose the model that suits you and benefit from responsive after-sales support. For full information on both options, see our CPAP reimbursement Belgium page.
Frequently asked questions about Auto CPAP vs fixed CPAP
If you buy your CPAP directly from VivaRespire, Auto-CPAP (APAP) is usually the best choice. It automatically adjusts pressure night after night to your needs, without requiring laboratory titration. You also access detailed data (AHI, leaks, actual pressure) via the myAir or DreamMapper apps. Fixed CPAP remains relevant only if your doctor has determined an optimal stable pressure during titration polysomnography.
Yes. The device's proprietary algorithm (AutoSet at ResMed, Auto-Adjusting at Philips) measures your airway resistance in real time, detects snoring, hypopneas and apneas, then adapts pressure every few seconds. If your airways are well open, pressure decreases for more comfort. If respiratory events appear, pressure rises just enough to eliminate them. Result: a lower average pressure than fixed CPAP at the same efficacy level.
Slightly, but the gap is narrowing. Modern Auto-CPAPs cost between €600 and €1,000, against €450 to €800 for an equivalent fixed CPAP. Most new models sold at VivaRespire (AirSense 11, DreamStation 2, Prisma Smart) are Auto-CPAPs, with fixed mode activatable through settings on these same devices. You therefore get versatility for both modes at moderate extra cost.
Fixed CPAP remains recommended in several specific situations. When the optimal pressure is very stable and well identified by titration. For some patients who find Auto-CPAP pressure variations bothersome. In cases of central apneas where automatic pressure variation can be contraindicated. And under strict medical follow-up with precise prescription. Your pulmonologist decides based on your profile.
Yes, this is one of the great advantages of modern Auto-CPAPs. All ResMed AirSense, Philips DreamStation and Löwenstein Prisma models can operate in fixed CPAP mode by setting a single pressure in the clinician menu. You (or your doctor) thus have a single device covering both uses. This flexibility is particularly useful if your prescription changes over time.
Yes. Under the INAMI/RIZIV convention, the accredited sleep centre can provide either a fixed CPAP or an Auto-CPAP, depending on the medical decision. You do not choose the model yourself: the centre provides the device available and adapted to your prescription. If you want to freely choose your model (ResMed AirSense 11, DreamStation 2, Prisma Smart), direct purchase outside the convention remains the recommended option.
Yes, this is a key advantage. Auto-CPAPs record night by night your residual AHI, leaks, average and P95 pressure, usage duration. This data is visible via myAir (ResMed), DreamMapper (Philips) or prismaTS (Löwenstein). You thus monitor your therapy efficacy daily and can share this data with your doctor. See also our page on OSCAR CPAP software.