If you’ve been prescribed a CPAP machine, you’ve probably noticed a number on your device or paperwork representing your pressure setting. Maybe it says 8, or 12, or you’ve seen a range like 5-15. But what do these numbers actually mean?
Understanding your pressure settings can help you have better conversations with your sleep care team and recognize when something might need adjustment.
CPAP pressure is measured in centimeters of water pressure, abbreviated as cm H₂O. This unit describes how much force the air exerts as it flows through your mask to keep your airway open.
Most CPAP machines operate within a range of 4 to 20 cm H₂O. The lower end delivers a gentler stream of air, while higher numbers mean more forceful airflow to keep the airway open in cases of more significant obstruction.
When looking at common CPAP pressure settings across the broader population of users, the average tends to fall somewhere between 8 and 10 cm H₂O. However, this is just a midpoint in a wide distribution. Research indicates that most people with obstructive sleep apnea find effective treatment within a range of 6 to 14 cm H₂O.
Studies examining optimal pressure levels have found that settings vary by sleep apnea severity, with mild cases averaging around 6 cm H₂O, moderate cases around 7-8 cm H₂O, and severe cases around 9 cm H₂O. That said, individual variation is significant, and someone with mild apnea might need higher pressure than someone with severe apnea depending on their unique anatomy.
There are two main approaches to CPAP pressure delivery.
A fixed-pressure CPAP delivers one constant pressure throughout the night. Your provider prescribes a specific number, and the machine maintains that level regardless of sleep stage.
An auto-adjusting PAP machine (APAP) works within a prescribed range rather than a single number. The device uses sensors to detect changes in your breathing and automatically adjusts pressure up or down as needed. You might see this written as a range like 6-12 cm H₂O. The machine starts at the lower end and increases only when it detects airway resistance, then decreases when the airway is stable.
Many providers now prefer APAP machines because they can deliver the minimum effective pressure at any given moment, potentially improving comfort while still adequately treating apnea events.
Your prescribed pressure isn’t arbitrary. It’s determined through a process called titration, which aims to find the lowest pressure that effectively eliminates your breathing disruptions during sleep.
The traditional approach involves an overnight sleep study in a specialized lab. While you sleep connected to monitoring equipment, a technician gradually increases the pressure starting from around 4 or 5 cm H₂O until your breathing events are resolved. They observe your sleep across different stages and positions to find a pressure that works throughout the night.
For many people with uncomplicated obstructive sleep apnea, providers may instead prescribe an APAP machine for home use. The device collects data over days or weeks, and the provider reviews the recorded pressure patterns to determine optimal settings.
Several factors affect what pressure you’ll need, which is why two people with similar apnea severity might have very different prescriptions.
Body weight plays a role; people with higher body mass often require higher pressures. Sleep position matters too, since sleeping on your back typically requires higher pressure than side sleeping because gravity pulls soft tissues toward the airway.
Your individual anatomy is perhaps the biggest factor. Neck circumference, jaw structure, tongue size, and the length of your soft palate all influence how much pressure is needed. This is why titration is so valuable; it accounts for your specific physiology rather than relying on general predictions.
Even after initial titration, your pressure needs can change over time due to weight changes, aging, or shifts in health status.
If your pressure seems too low, you might notice continued snoring while using the machine, waking up feeling unrefreshed despite good usage hours, persistent daytime sleepiness, or an elevated AHI reading on your machine.
If your pressure seems too high, common signs include difficulty exhaling against the airflow, frequent mask leaks, dry mouth or nasal irritation, or bloating and excessive gas from swallowing air. This last symptom, called aerophagia, affects an estimated 16% of CPAP users and can sometimes be linked to pressure exceeding what your airway actually needs.
While it’s technically possible to access and change your CPAP pressure settings on most machines, doing so without guidance from your sleep care provider is generally not recommended. Pressure settings are part of your prescribed treatment. Setting the pressure too low means your apnea won’t be adequately treated, while setting it too high can cause discomfort and new side effects.
If you suspect your pressure needs adjustment, bring your CPAP machine to your next appointment. Your provider can review the recorded data and make informed adjustments based on how your therapy has been performing.
Common CPAP pressure settings for most users fall somewhere between 6 and 14 cm H₂O, with an overall average around 8 to 10. But “common” doesn’t mean “correct for you.” Your ideal pressure depends on your specific anatomy, sleep patterns, apnea severity, and other individual factors that only proper assessment can determine.
Understanding what these numbers mean puts you in a better position to engage with your treatment and recognize when something might be off. If you’re experiencing symptoms that suggest your pressure isn’t quite right, that’s valuable information to share with your sleep care team so they can help optimize your therapy.