What Is EPR on CPAP?

Key Takeaways

• EPR stands for expiratory pressure relief, and this CPAP machine feature delivers slightly weaker air pressure when breathing out.
• Some people find that EPR helps make it easier to breathe with CPAP.
• You can adjust EPR settings by yourself, but be careful not to tamper with your actual CPAP therapy settings.

What Does EPR Mean on a CPAP Machine?

Expiratory pressure relief (EPR) on CPAP is a feature that lowers the air pressure during exhalation. This is in contrast to traditional CPAP therapy, which uses a fixed setting to maintain the same air pressure all the time, whether you’re inhaling or exhaling.

The CPAP EPR function is designed to make your therapy more comfortable, as you don’t have to fight against such strong incoming airflow every time you breathe out. EPR was developed a couple of decades ago and is now quite common.

Although the term is frequently used to refer to this function on any CPAP device, EPR is actually a trademarked name by ResMed, one of the main CPAP device manufacturers. The generic name for EPR is exhalation relief. You might also find it under the terms AirRelief/EZEX (Transcend), expiratory relief (Fisher & Paykel), Reslex Exhalation Relief (React Health, which makes the Luna G2), or Z-Breathe (Breas). 

Don’t Just Test Your Sleep. Understand It.

Measure key sleep metrics and review your results with a licensed sleep-care provider. Discuss sleep issues and options to make restless nights a thing of the past.

Results and data from the comfort of your own bed

Virtual consultation with a licensed sleep-care provider

Diagnosis, prescription, and personalized care plan

4.8

35,000+ tests sold

Get Started

How Does EPR Work?

CPAP EPR settings usually offer the option to lower air pressure during exhalation by one, two, or three levels. The amount of pressure corresponding to each level can vary between brands. 

With a ResMed machine, the three levels correspond to 1 cm H2O, 2 cm H2O, or 3 cm H2O, respectively. So, for example, if your regular therapy setting is 13 cm H2O and you set the EPR to level 2, the delivered airflow would be 13 cm H2O when breathing in and 11 cm H2O when breathing out.

To ensure effective therapy, the machine might not let you drop below a certain level, even on exhalation. For example, ResMed requires at least 4 cm H2O of pressure during exhalation.

Experts have observed that the airway is most likely to close at the moment when you’re almost finished breathing out, just before you take your next breath. Manufacturers may use proprietary EPR algorithms that specifically drop the pressure level when you start to breathe out, and increase it just before you inhale.

Your CPAP machine may offer additional choices, such as the option to use EPR exclusively during the “ramp” phase, which starts therapy at a lower pressure and then increases either after a set amount of time or once regular breathing is detected. Combining ramp and EPR settings allows you to ease into therapy with easier breathing as you drift off, then set therapy back to normal levels once you’re asleep.

Who Might Benefit Most From EPR?

EPR is largely a matter of personal preference. You might find this pressure relief feature helpful when you first start your CPAP journey, especially if you have trouble adjusting to the feel of the airflow. EPR may also be appealing for people with higher prescribed pressure setting, people with irritated airways, or those with obesity.

So far, results are mixed on whether EPR makes a difference to CPAP adherence, the official term for how likely it is that you’ll stick with CPAP therapy. Some experts argue that having two different air pressure levels could actually make breathing more difficult or lead to rebreathing exhaled air. Others say there’s a small risk that these pressure changes might lead to a different type of apnea, central sleep apnea (CSA). Ultimately, the decision lies with you and your doctor.

Many CPAP side effects are the result of a poor mask fit or inadequate humidity settings. You might find that a simple solution like switching your CPAP mask solves discomfort without needing to resort to EPR.

EPR vs. BiPAP: What’s the Difference?

APAP, BiPAP, and EPR are different forms of PAP therapy that adjust pressure levels in different situations. APAP machines monitor your breathing and adjust pressure on an ongoing basis. BiPAP machines deliver a higher pressure during inhalation and a lower pressure during exhalation. EPR is similar to BiPAP but usually works with smaller changes of not more than 3 cm H2O. 

All three modes share a common goal: to continue delivering effective therapy while minimizing the side effects that occur with high-pressure airflow, thereby making it easier to use CPAP therapy. Another commonality between these three modes is that some level of air pressure is always maintained during exhalation to keep the airway open.

Between EPR and BiPAP, it’s easiest to access EPR, since BiPAP therapy is usually only prescribed once you have unsuccessfully tried CPAP therapy. 

How Do You Adjust EPR Settings?

EPR settings generally offer a choice between three levels: 1, 2, 3, or off. You can access the EPR settings through the settings menu on your CPAP machine or smartphone app. When changing your EPR levels, move one number at a time, so you can evaluate if it’s working for you before jumping to the next number.

Even if your CPAP machine allows you to adjust the EPR settings by yourself, you should always proceed with caution and never adjust your normal therapy pressure levels without talking to your provider first. In fact, if you plan on using EPR, it’s a good idea to mention this to your provider during your titration appointment. This can help them set your therapy levels at the optimal levels, which may need to be slightly higher to compensate for the EPR.

As you make changes to the EPR, keep an eye on your CPAP data to make sure your apnea-hypopnea index (AHI) is not getting worse. You should also take note of any side effects, such as dry mouth, bloating, or nasal congestion, to get an idea of whether the EPR is helping.