Positive end-expiratory pressure (PEEP) is a therapeutic method where the positive airway pressure at the end of expiration or exhalation that is necessary to prevent the alveoli from collapsing. Negative end-expiratory pressure (PEEP) or auto-PEEP is a complication of mechanical ventilation characterized by development of positive airway pressure in lungs because of the trapping of air inside it. During the passive expiration, complete emptying of lungs take place but sometimes incomplete emptying occurs due to trapping of air inside the lung. This trapped air causes increased positive pressure and ultimately Intrinsic Positive PEEP. Intrinsic Positive PEEP or auto-PEEP makes the work of breathing difficult. It is more common in patients with asthma, COPD and emphysema. This condition causes increases in intrathoracic pressure and volume and causing barotrauma.