What is EPR? That "Comfort" Setting on Your CPAP

Hey Sleep Warriors, have you ever looked through the settings on your CPAP machine and seen something called EPR or pressure relief? On some machines it's called C-Flex.

EPR, or C-Flex, stands for expiratory pressure relief. It's basically a comfort feature designed to make CPAP easier to breathe with.

So here's how it works. Normally, CPAP delivers pressure to help hold your airway open while you sleep. But some people feel like they're having to push against that pressure when they breathe out, or exhale. EPR temporarily drops the pressure when you exhale.

On a ResMed machine, for example, EPR can generally be set from 1 to 3. An EPR of 1 drops the pressure by about 1 centimeter of water when you breathe out, while an EPR of 3 drops it by about 3. For many people, that feels much more natural and comfortable, especially when they're first getting used to CPAP.

But there's an interesting catch.

A new study published in CHEST looked at people with severe obstructive sleep apnea and found that lowering the pressure during exhalation could actually allow the airway to narrow more. With expiratory pressure relief turned on, patients required higher CPAP pressures, and the residual apnea hypopnea index was somewhat higher. In other words, EPR helped with comfort, but in some people it made CPAP slightly less effective.

Now, this doesn't mean everyone should turn their EPR off. If you're comfortable, sleeping well, and your sleep apnea is well controlled, there's probably no reason to change anything.

But if you're using CPAP consistently and your numbers are still higher than expected, or you're still having snoring, flow limitation, or symptoms, EPR is one setting worth looking at.

On some CPAP machines, pressure relief is available right in the comfort settings on your machine, although your equipment provider or clinician may control whether or not you can adjust it yourself. If it's available, you could discuss trying EPR at a lower setting, or turning it off completely, and seeing whether your CPAP data improves.

And if you're not sure what your settings mean, talk with your sleep doctor or your CPAP provider before making any changes.

Sometimes, improving CPAP isn't about adding more pressure. It may simply be understanding what all those little settings are actually doing.

Thanks so much for being here. Sleep well and I'll see you next week!

Source: Grad GF, et al. Impairment of upper airway patency and CPAP effectiveness during obstructive sleep apnea treatment with expiratory pressure alleviation: a randomized study. CHEST. Published online September 3, 2026. DOI: 10.1016/j.chest.2026.08.041

Music: Daily Beetle by Kevin MacLeod is licensed under a Creative Commons Attribution 4.0 license.