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How to know if your CPAP pressure is well set
The pressure setting of your CPAP device is the most critical parameter of your therapy. Pressure that is too low lets apneas through. Pressure that is too high causes discomfort, leaks, and can even trigger complex central apneas. But how can you objectively tell if your setting is optimal? This guide explains the indicators to monitor.
The primary indicator: residual AHI
The residual AHI (Apnea-Hypopnea Index under treatment, also called treated AHI or AHI-T) is the number of apneas and hypopneas persisting despite CPAP therapy, per hour of sleep. It is the best single indicator of your pressure's effectiveness.
| Residual AHI | Interpretation | Recommended action |
|---|---|---|
| < 5 | Excellent - effective therapy | No change needed |
| 5 - 10 | Acceptable for some profiles | Monitor trends; consult if symptoms persist |
| 10 - 15 | Insufficient - sub-optimal treatment | Consult your doctor for adjustment |
| > 15 | Treatment not effective | Urgent consultation - pressure likely too low |
How to read your CPAP data
For a first estimate before you even look at your data, our CPAP pressure calculator gives an order of magnitude from your BMI, neck circumference and AHI.
Via the myAir app (ResMed)
The myAir app from ResMed (compatible with AirSense 11 and AirSense 10) gives you a morning sleep score out of 100 and key data:
- Treated AHI: your residual AHI for the night
- Leaks: leak volume in L/min (ideally < 24 L/min)
- Usage duration: hours with the mask on
- Median and P95 pressure: on auto CPAP devices
Via the OSCAR software (open source)
OSCAR (Open Source CPAP Analysis Reporter) is a free, open-source program that analyses the full data stored on your CPAP device's SD card. It gives a detailed night-by-night view:
- Real-time pressure curve
- Detection of apneas, hypopneas and RERAs (respiratory effort related arousals)
- Leak curve and excessive leak flagging
- Cheyne-Stokes periodic breathing, if present
- Trends over several weeks or months
Can you adjust your own CPAP pressure?
Let us be blunt: it is not illegal. A patient who bought their own device can technically reach the clinical menu, and the codes circulate in specialist forums. The real question is not permission, it is method.
We will not publish the procedure. If you are considering it, however, here is the safety framework recommended by the ApneaBoard patient community, which strikes us as the bare minimum.
- Get a sleep study first. Change nothing until you have lived several weeks with the prescribed pressure
- Never change by more than 0.5 cmH2O at a time
- Wait one to two weeks before any further change
- Keep a written log of how you feel morning, afternoon and evening
- Change no other variable at the same time, or you will not know what caused the effect
- Track your residual AHI, aiming to stay below 5
For the procedure itself, go to the source that documents it: ApneaBoard. And whatever you do, discuss the number with your doctor.
Signs your pressure is too low
- High residual AHI (above 5, especially regularly > 10)
- You still snore at night (confirmed by partner or app)
- You still wake up tired despite several hours of CPAP use
- Sensation of suffocation or air hunger during the night
- Data shows many residual obstructive apneas
Signs your pressure is too high
- Difficulty exhaling - feeling of resistance when breathing out
- Significant, frequent mask leaks (air escaping at the edges)
- Increase in central apneas (brain not receiving the signal to inhale)
- Morning bloating (swallowed air overnight - aerophagia)
- General discomfort or refusal to wear the mask
Auto CPAP vs fixed CPAP: the impact on settings
An auto CPAP (APAP) automatically adapts to your moment-to-moment breathing needs, night after night. It delivers the minimum pressure needed to eliminate apneas, generally improving comfort and reducing side effects from excess pressure.
A fixed CPAP always delivers the same pressure regardless of your state. If your pressure is correctly titrated it works well, but if your needs vary (position, congestion, alcohol), the fixed pressure may be insufficient some nights and too high on others.
The doctor's role in pressure setting
- Analyse your downloaded data to identify problems
- Modify the minimum or maximum pressure on an auto CPAP
- Adjust the fixed pressure of a conventional CPAP
- Enable or adjust EPR (Expiratory Pressure Relief) for better exhalation comfort
- Change device type (CPAP to BiPAP) if necessary
Mask leaks: a key factor
Excessive mask leaks can distort your CPAP data and reduce therapy effectiveness. The acceptable leak value is generally below 24 L/min (per ResMed) or equivalent depending on the brand. Beyond this, your device works harder, pressure may increase unnecessarily, and your residual AHI may be overestimated.
CPAP devices with data tracking at VivaRespire
- ResMed AirSense 11 AutoSet - myAir app, Bluetooth, cloud data
- Philips DreamStation 2 - DreamMapper app, detailed reports
- Löwenstein Prisma SMART Auto - data analysable via prismaTS software
Browse our full range: auto CPAP and fixed CPAP.
Frequently asked questions about CPAP pressure settings
The main indicator is your residual AHI (Apnoea-Hypopnoea Index under treatment): it should be below 5 events per hour. You find this value on your device's screen on waking, in the myAir app or in OSCAR. Combine it with your subjective experience: if you wake rested, without morning headaches or daytime sleepiness, your pressure is probably correct. If the AHI remains high or symptoms persist, discuss with your doctor.
The recognised clinical target is a residual AHI below 5. Between 5 and 10, it is acceptable but improvable depending on your subjective state. Between 10 and 15, treatment is sub-optimal and a consultation is needed. Above 15, CPAP is not delivering its benefit: see your doctor quickly to adjust pressure or explore other causes (central apnoeas, major leaks). This scale applies to ResMed, Philips and Löwenstein devices.
Not necessarily, and especially not without medical advice. Persistent fatigue has several possible causes: genuinely insufficient pressure, mask leaks distorting the data, central apnoeas that standard CPAP does not treat, poor sleep hygiene, or simply ongoing adaptation. That adaptation can take two to three months. Inspect your data first (AHI, leaks, usage hours), fix what can be fixed, then discuss with your doctor if nothing improves.
Yes, several:
- Difficulty exhaling against the pressure
- Morning bloating, from air swallowed overnight
- Significant leaks at the edges of the mask
- Paradoxically, more central apnoeas, as the brain stops triggering inhalation
General discomfort often leads to unconscious mask removal during the night. If you have these symptoms, consider switching EPR on from the myAir app, and discuss a lower maximum pressure with your doctor.
Yes, it is possible with modern connected CPAPs. The AirSense 11 transmits your data via the ResMed AirView portal, which your doctor or provider can access with your consent. They can adjust minimum and maximum pressures, EPR, ramp and other parameters without you having to travel. The new configuration applies from the next session. This telemedicine is widely used in Belgium under the INAMI convention.
Auto-CPAP (APAP/AutoSet) is not "more accurate" but more adaptive. It delivers, at each moment, the minimum pressure necessary based on your respiratory events. If your needs vary (position, alcohol, cold), it adjusts on its own. A properly titrated fixed pressure can be equally effective, but it does not adapt to night-time variations. For a purchase without formal lab titration, auto-CPAP is clearly preferable. See our guide auto CPAP vs fixed CPAP.
Four indicators to monitor, in this order of priority:
- Residual AHI, target below 5
- Mask leaks, target below 24 L/min nasal and 36 L/min full face
- Usage hours, target at least 4 hours per night
- P95 pressure on auto devices. Close to the ceiling, consider raising the maximum
If these four metrics look good, your therapy is on track. If one drifts, address it before the others.
An AHI of 8 is acceptable but improvable. It is better than the untreated patient average but below the optimal target (< 5). First check leaks: if they are high, your displayed AHI is probably overestimated - fix the mask and re-measure. If leaks are low and AHI stays around 8 over several nights, discuss with your doctor: a moderate pressure increase may bring this figure into the optimal zone. Do not modify anything yourself.