EPAP

Expiratory Positive Airway Pressure (EPAP) is a parameter used in noninvasive ventilation systems to maintain a baseline positive airway pressure during expiration. EPAP is most commonly encountered in BiPAP therapy, where it is applied concurrently with an additional inspiratory pressure (IPAP). The pressure is measured in centimeters of water (cm H2O) and is typically set lower than IPAP.

Role and mechanism: EPAP serves to stent the upper airway and improve patency by preventing collapse during exhalation, which can enhance gas exchange and reduce the work of breathing in patients with obstructive sleep apnea or COPD with hypoventilation. By maintaining a positive pressure during expiration, EPAP reduces pharyngeal airway collapsibility; the amount of pressure influences airway resistance and patient comfort.

Clinical use and settings: In BiPAP, IPAP provides inspiratory support and EPAP maintains expiration pressure; adjusting EPAP can help treat obstructive events, but excessive EPAP can cause discomfort, mask leaks, aerophagia, and reduced tidal volume. CPAP therapy uses a single continuous pressure rather than IPAP/EPAP; some devices label their baseline pressure as EPAP.

Safety and considerations: EPAP levels are individualized based on tolerance and therapeutic goals. High EPAP improves airway patency but may impair spontaneous breathing effort or hemodynamics in certain patients. Regular monitoring and mask fit are important to minimize side effects and optimize adherence.

See also: BiPAP, CPAP, IPAP, obstructive sleep apnea, noninvasive ventilation.