Continuous positive airway pressure (CPAP) is a form of
positive airway pressure ventilator, which applies mild air pressure on a continuous basis to keep the airways continuously open in a patient who is unable to breathe spontaneously on their own. It is an alternative to
positive end-expiratory pressure (PEEP). Both modalities stent the lungs'
alveoli open and thus recruit more of the lung's surface area for ventilation. But while PEEP refers to devices that impose positive pressure only at the end of the
exhalation, CPAP devices apply
continuous positive airway pressure throughout the breathing cycle. Thus, the ventilator itself does not cycle during CPAP, no additional pressure above the level of CPAP is provided, and patients must initiate all of their breaths.