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 people who are able 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. CPAP is the most effective treatment for obstructive sleep apnea.