Expiratory Positive Airway Pressure (EPAP) is a non-invasive respiratory support method. Unlike other common therapies, EPAP devices work by utilizing the individual’s own breathing mechanics to create pressure. Its primary function is to keep the upper airway from collapsing, a common event in OSA where the throat muscles relax and block the passage of air. This targeted support during the breathing cycle makes EPAP a simpler, machine-free alternative for managing the condition.
How EPAP Works to Maintain Airway Patency
The physiological mechanism of EPAP relies on generating a back-pressure that acts as a pneumatic splint to hold the airway open. When a person exhales against the device, the resistance created by the EPAP system causes a buildup of pressure within the upper airway. This pressure is generated specifically during the exhalation phase.
This temporary pressure increase physically resists the natural tendency of the soft tissues in the throat to collapse, which is the underlying cause of obstructive sleep apnea events. Maintaining this positive pressure throughout the exhalation phase prevents the airway from narrowing, thereby conditioning it to remain open. As the user begins the next inhalation, the pathway is already stabilized and less prone to obstruction.
The device’s design allows for nearly unimpeded inhalation. The critical action occurs when the user breathes out, forcing the breath through a restrictive opening or valve. This action effectively uses the patient’s own exhaled air to maintain the patency of the pharyngeal structure until the next breath is taken.
Key Differences Between EPAP and CPAP
The fundamental distinction between EPAP and Continuous Positive Airway Pressure (CPAP) lies in the timing and consistency of the applied pressure. CPAP delivers pressurized air throughout the entire breathing cycle, both when the user inhales and when they exhale. This continuous pressure acts as a consistent air splint to prevent the airway from collapsing.
EPAP, by contrast, applies significant positive pressure only during the exhalation phase. While the pressure remains low or near-atmospheric during inhalation, it increases substantially as the user breathes out against the device’s resistance. This difference means the user is not breathing against a high-pressure stream when trying to inhale, which some individuals find more comfortable.
In the context of Bi-level Positive Airway Pressure (BiPAP) machines, EPAP is the lower of the two pressure settings delivered. The higher setting is Inspiratory Positive Airway Pressure (IPAP), which actively assists the inhale. EPAP devices, however, typically do not include an active IPAP, relying instead on the residual pressure generated during the exhale to stabilize the airway for the next breath.
Common EPAP Delivery Systems
The most recognized forms of EPAP therapy are small, disposable nasal devices that use microvalve technology. These systems typically consist of small valves or plugs that fit into or adhere to the nostrils. They are designed to be lightweight and simple, avoiding the need for the hoses and motors associated with traditional machines.
These nasal devices create resistance to airflow, often involving a one-way valve or a series of small, restrictive openings. When the user inhales, the valve opens easily. As the user exhales, the valve closes or the air is channeled through a much narrower path, generating the required back-pressure.
EPAP can also be delivered as a pressure setting on a BiPAP machine, which features a motor and mask system. In this context, the EPAP level is the minimum pressure maintained in the circuit. However, when people refer to EPAP therapy as a stand-alone alternative, they are usually referring to the compact, non-powered nasal devices.
Indications and Patient Suitability for EPAP Therapy
EPAP therapy is generally prescribed for individuals diagnosed with mild to moderate Obstructive Sleep Apnea. Patients who have been unable to tolerate the bulk or continuous high pressure of a CPAP machine often find it a suitable alternative. The smaller size and machine-free operation of nasal EPAP devices often lead to better patient adherence to the treatment.
Good candidates for this therapy often include those who are primarily nasal breathers and who prefer a less intrusive solution. The portability and lack of a power requirement also make it a convenient option for frequent travelers.
However, EPAP is not suitable for all forms of sleep-disordered breathing. It is not recommended for individuals with severe OSA who require higher, actively delivered pressure levels. Furthermore, it is not an effective treatment for central sleep apnea, which involves a failure of the brain to signal the muscles to breathe, rather than a physical airway obstruction.