EPR stands for Expiratory Pressure Relief. It is the setting on ResMed CPAP machines (AirSense 10, AirSense 11, AirMini) that drops the pressure by 1, 2 or 3 cm H2O every time you breathe out, so exhaling does not feel like pushing against a wall. That is the definition, and if that is all you wanted, you are done. But the questions people actually search for go further: which level should I use, does EPR lower my real pressure, does it make therapy less effective, why does it feel worse for some people, why is it greyed out on my machine, and how exactly do I change it? This guide answers those, with a clear line between what ResMed says, what experienced CPAP users report, and what is still debated.
Pressure settings are prescribed. EPR is a comfort setting that your provider may or may not have unlocked for you. If you are unsure whether you should change it, ask your sleep specialist or the supplier who set up your machine.
What EPR actually does to your pressure
Your prescription sets the pressure the machine delivers while you inhale. EPR subtracts a fixed amount during each exhale and restores it when you inhale again. The three levels are exactly what they sound like:
| EPR level | Pressure drop on exhale | Example: set pressure 10 cm H2O | Example: set pressure 5 cm H2O |
|---|---|---|---|
| Off | None | Inhale 10, exhale 10 | Inhale 5, exhale 5 |
| 1 | 1 cm H2O | Inhale 10, exhale 9 | Inhale 5, exhale 4 |
| 2 | 2 cm H2O | Inhale 10, exhale 8 | Inhale 5, exhale 4 (not 3) |
| 3 | 3 cm H2O | Inhale 10, exhale 7 | Inhale 5, exhale 4 (not 2) |
The right-hand column shows the one rule that trips people up: ResMed's user guides state that with EPR on, the delivered pressure will never drop below 4 cm H2O. If your pressure (or, on an AutoSet, your minimum pressure) is already 4, EPR does nothing at all. At 5 or 6, only part of the relief is delivered. EPR is most noticeable at pressures of 8 and above, which is exactly where people tend to want it.
On an AutoSet in auto mode, the machine still raises and lowers pressure through the night; EPR simply sits on top of whatever pressure it is delivering at the time.
Which EPR level should you use: 1, 2 or 3?
There is no medically "correct" level. ResMed describes EPR as a comfort feature, and the most experienced voices on CPAP forums say the same thing in plainer terms: it is personal, try it, and give each change a fair trial. A practical way to choose:
- Start at 1 or 2 if you are new to CPAP and the pressure feels like a lot. Level 3 is not "better," it is just more relief, and more relief is not always better (see the next two sections).
- Use 3 if you are on higher pressures (roughly 12 and up) and breathing out feels like work. Several long-term users report they settled on 3 and never looked back.
- Try turning it off if you feel rushed, "hyperventilated," or short of air on inhale, or if your therapy numbers got worse when it was switched on. One user described exactly that at level 2 with chest discomfort; switching EPR off fixed it and his AHI stayed under 2.
- Change one thing at a time and give it one to two weeks. A night or two is not enough to judge, because how you sleep varies more than the setting does.
A cautionary pattern from the forums: a lot of "EPR problems" turn out to be mask leaks or mouth breathing. If your numbers or comfort change right after altering EPR, check your mask seal score before concluding the setting is the cause. One AirSense 11 user who tried a higher minimum pressure with EPR 3 got headaches and a mask that would not seal; once the mask was sorted, he slept well again at his original settings.
Does EPR make CPAP less effective?
Honest answer: it can, for some people, and for others it makes no difference or helps. The mechanics are simple. Your airway is most likely to collapse at the end of exhale, and EPR lowers pressure at exactly that moment. If your prescribed pressure is just barely enough, subtracting 3 cm H2O on every exhale can let obstructions through. Experienced users on CPAPtalk describe seeing AHI move in either direction after changing EPR: some got better numbers with it off, others with it on 3.
There is a second, subtler effect: when EPR drops the pressure on exhale, it takes a moment to climb back on inhale, which some users describe as a "lag" that matters more at low pressures. And a third: for a small number of people, EPR appears to increase central or "clear airway" events (pauses where the airway is open but the breathing effort stops), possibly because breathing more easily blows off more carbon dioxide. A veteran forum moderator's view is that this concern is real but "blown way out of proportion," affecting a small minority, and that treatment-emergent central events usually settle over a few weeks anyway. Users who did see clear-airway events climb after enabling EPR 3 report that dropping to 1, or turning it off, brought them back down.
What to watch in myAir or OSCAR after changing EPR: your AHI, the split between obstructive and clear-airway events, your leak, and how you feel in the morning. If AHI rises and stays up for a week or more, the level is too high for your pressure. If you are on an AutoSet, some forum users compensate by raising the minimum pressure slightly, since EPR effectively lowers the pressure that keeps the airway open; that is a prescription change and belongs in a conversation with your provider, not a solo experiment.
For a deeper look at reading your numbers, see how to improve your AHI score.
EPR "Full time" vs "Ramp only"
Buried in the clinical menu is a setting most people never see: EPR Type. "Full time" applies relief all night. "Ramp only" applies it only during the ramp period at the start of the night, then removes it once you are asleep. Ramp-only is a sensible middle ground if you want help falling asleep but have found full-time EPR hurts your numbers. Note that on the AirMini, if Ramp is set to Off and EPR is Ramp only, EPR never activates, which is a common reason people think it is broken.
How to change EPR on the ResMed AirSense 11
- Tap the screen to wake it, or press the Home button.
- Tap My Options.
- Tap Comfort (on some software versions this section is labeled Pressure Relief).
- Tap EPR and choose Off, 1, 2 or 3, then confirm.
If EPR is missing from My Options, or you can only turn it on and off but not change the level, your provider has restricted it in the clinical menu. That is deliberate on their part, so ask them rather than looking for a workaround. The full range of options (EPR on/off, type, and level 1 to 3) lives in the clinician settings, which ResMed's guide marks as "features enabled by your care provider."
How to change EPR on the ResMed AirSense 10
- Press the dial to wake the screen and turn it to highlight My Options; press to select.
- Turn the dial to EPR and press.
- Turn the dial to choose Off, 1, 2 or 3, and press to confirm.
The AirSense 10 patient menu shows EPR Level only if your provider enabled it. The clinical menu (hold the dial and the Home button together for three seconds) contains EPR Enable, EPR Type (Full time or Ramp only) and EPR Level. We show you where the clinical menu is because you will find it on any forum, not to encourage changing prescribed settings; if you go in there, change only EPR, and tell your provider.
Where the clinical menu is on the AirSense 10, which is where EPR Type and EPR Enable live.
EPR on the ResMed AirMini
The AirMini does have EPR (some guides, including an older version of this one, got that wrong). Because the AirMini has no screen, you change it in the AirMini app on your phone: open the app with the machine connected over Bluetooth, go to the settings or comfort section, and select the EPR level. As on the larger machines, the levels are 1 to 3 and the 4 cm H2O floor applies. Remember the Ramp-only quirk above. The AirMini AutoSet travel CPAP runs the same AutoSet algorithm as the AirSense, so EPR behaves the same way.
EPR vs Flex vs BiPAP: what is the actual difference?
- EPR (ResMed) drops the exhale pressure by a fixed 1, 2 or 3 cm H2O.
- Flex (Philips: C-Flex, A-Flex) does a similar job but scales the relief with how hard you breathe out, so it feels slightly more dynamic. Levels 1 to 3, similar effect. Other brands have their own names (React Health calls it Reslex; travel machines from other makers use EZEX, Z-Breathe and so on). They are all variations on the same idea.
- BiPAP (bilevel) is a different class of machine. Instead of a comfort tweak of up to 3 cm H2O, a bilevel machine delivers two separately prescribed pressures, and the gap between them (pressure support) can be 4, 6, 8 cm H2O or more. If you are on high pressure and EPR 3 still leaves you fighting to exhale, that is the point where sleep specialists start talking about bilevel. The ResMed AirCurve 11 VAuto is the bilevel counterpart of the AirSense 11 and behaves like a much more capable EPR: same touchscreen, same humidifier, but with adjustable pressure support instead of a 3 cm ceiling. It needs a bilevel prescription.
Read more in AirCurve 10 vs AirCurve 11 and is your CPAP pressure too high?
EPR for specific problems people ask about
Swallowing air (aerophagia) and bloating
Lowering the exhale pressure is one of the first things users try for aerophagia, on the theory that less pressure means less air forced down the esophagus. Some report it helps; there is no study confirming it, and if the machine has to run a higher inhale pressure to compensate, it can cut the other way. Our aerophagia guide covers the full list of things to try.
Dry mouth and mask leaks
EPR does not fix dry mouth directly, and there is a wrinkle: because pressure swings between inhale and exhale, a marginal mask seal can leak more with EPR on. One user saw his leak rate jump when he turned EPR off, though, so this goes both ways. If your leak is high, sort the mask first (see common CPAP problems and fixes), then revisit EPR.
Feeling like you are not getting enough air
Counterintuitively, this is often reported with EPR on, particularly at level 2 or 3 and lower pressures: the drop on exhale makes the return of pressure on inhale feel abrupt, and some people describe it as being rushed or hyperventilating. Try level 1 or Off for a week.
Flow limitation and UARS
People who track their data in OSCAR sometimes use EPR to reduce flow limitation, since a bigger inhale-to-exhale gap can smooth breathing. It can work, but it also lowers effective pressure and can raise AHI; one user saw flow limitation fall and AHI rise at the same time. This is bilevel territory, and worth discussing with a sleep specialist who will look at your data.
Frequently asked questions
What is the best EPR setting?
Whichever one you sleep best on. Start at 1 or 2, use 3 on higher pressures if exhaling feels hard, and try Off if you feel rushed or your AHI went up. Give each change one to two weeks.
Does EPR lower my pressure?
Only on exhale, by 1, 2 or 3 cm H2O, and never below 4 cm H2O. Your inhale pressure is unchanged.
Can EPR cause central apneas?
In a small minority of people, EPR seems to increase clear-airway events, and lowering the level or turning it off brings them back down. Most users see no change. If you notice a rise in clear-airway events after enabling EPR, mention it to your provider.
Why can't I change EPR on my AirSense 11?
Your provider has locked it in the clinical menu. Ask them to enable it or to change the level.
Does the AirMini have EPR?
Yes, set through the AirMini app. Make sure EPR Type is Full time if you want it all night; Ramp only with Ramp off means it never activates.
Is EPR the same as BiPAP?
No. EPR is a comfort feature capped at 3 cm H2O of relief. A BiPAP delivers two prescribed pressures with a gap that can be much larger. If EPR 3 is not enough, bilevel is the next step, and it needs a prescription.
Should I turn EPR off?
If you feel fine with it on and your numbers are good, leave it. If you feel rushed, short of air, or your AHI rose after turning it on, try Off for a week and compare.
The bottom line
EPR is a comfort dial, not a therapy setting, but it does change the pressure you are treated with on every breath, so it is worth setting with a little care: one change at a time, a week or two per change, and an eye on your numbers. If you are shopping for a machine and want EPR, every current ResMed unit has it, including the AirSense 11 AutoSet, the AirSense 10 AutoSet and the certified refurbished AirSense 11. If EPR at 3 still is not enough relief, that is the signal to ask your doctor about bilevel, and the AirCurve BiPAP lineup is where that conversation ends up.