Continuous Positive Airway Pressure (CPAP) therapy is the standard treatment for obstructive sleep apnea (OSA), delivering a constant flow of pressurized air to keep the airway open during sleep. Many users find the fixed pressure difficult to breathe out against, leading to discomfort and reduced adherence. To address this challenge, manufacturers developed Expiratory Pressure Relief (EPR), a comfort feature designed to make exhaling feel more natural.
Understanding Expiratory Pressure Relief (EPR)
EPR temporarily reduces the pressure delivered by the CPAP machine only during the user’s exhalation phase. Operating on a breath-by-breath basis, the machine senses when the user begins to exhale and momentarily drops the air pressure. This reduction alleviates the sensation of “breathing against a wall” that many new users experience.
The feature is typically adjustable, often offering three distinct levels of relief, measured in centimeters of water pressure (cmH2O). For instance, an EPR setting of 1 means the pressure drops by 1 cmH2O during exhalation, and a setting of 3 provides the maximum drop of 3 cmH2O. If a machine is set to deliver 10 cmH2O and the user selects an EPR setting of 2, the pressure will fluctuate between 10 cmH2O on inhalation and 8 cmH2O on exhalation.
Different CPAP manufacturers use proprietary names for this similar comfort feature. ResMed calls its version Expiratory Pressure Relief (EPR), while Philips Respironics refers to its suite of exhalation relief technologies as FLEX, which includes names like C-Flex and A-Flex. Despite the different branding, the core function remains the same: to mitigate the physical effort required to breathe out against the positive airway pressure.
The Primary Benefits of Using EPR
EPR significantly enhances the user’s comfort during sleep therapy. By reducing the resistance against exhalation, the feature allows for a more natural breathing pattern, easing the transition into long-term CPAP use. This improved comfort is especially beneficial for individuals sensitive to higher pressure settings.
Comfort is directly linked to how often and how long a person uses their CPAP machine each night. Higher comfort levels translate to better adherence to the prescribed therapy, which is important for the successful management of obstructive sleep apnea. EPR helps prevent users from prematurely abandoning treatment due to the physical discomfort of forced exhalation.
Pressure relief can also indirectly reduce issues such as mask leaks. When a user struggles to exhale against high pressure, they may involuntarily push the mask away from their face or attempt to breathe out through their mouth. The temporary pressure reduction from EPR minimizes these movements, helping to maintain a consistent mask seal throughout the night.
Potential Trade-offs and Considerations
While EPR improves comfort, it introduces a trade-off that users must consider regarding therapy efficacy. Since EPR drops the air pressure during exhalation, it temporarily reduces the effective minimum pressure delivered to the airway. This momentary drop may compromise the machine’s ability to keep the airway open during the exhalation phase.
For individuals requiring high pressure to prevent airway collapse, this pressure reduction can lead to an increase in the Apnea-Hypopnea Index (AHI). The AHI measures the number of apneas and hypopneas recorded per hour and is the primary measure of therapy effectiveness. An increased AHI after activating EPR suggests the comfort feature is reducing the therapeutic benefit.
If EPR is needed for comfort, the overall prescribed pressure may need to be increased to compensate for the reduction. For example, a user needing 10 cmH2O to control OSA who uses EPR level 2 (a 2 cmH2O drop) is effectively reducing pressure to 8 cmH2O during exhalation. The sleep specialist may recommend increasing the prescribed pressure to 12 cmH2O to ensure the minimum pressure during exhalation remains at the necessary therapeutic level of 10 cmH2O.
Guidance on When and How to Use EPR
The decision to use EPR should always be made in consultation with a qualified sleep physician or respiratory therapist. They can analyze your existing sleep data and determine if the feature is appropriate for your specific pressure needs and OSA severity. Activating EPR without professional guidance risks compromising treatment effectiveness.
If you are new to CPAP or struggling with the sensation of exhaling, start with the lowest EPR setting, typically level 1. This provides minimal relief while allowing you to gauge the impact on your comfort and sleep quality. You can then gradually increase the setting one level at a time, if necessary, while monitoring your results.
After activating or changing the EPR setting, check the efficacy metrics reported by your CPAP machine, notably the AHI. If the AHI increases significantly, it indicates that the pressure relief is interfering with the primary goal of the therapy. The setting should be adjusted or deactivated. The sleep specialist can review this data to decide if the overall pressure needs to be raised or if the EPR setting is too high.