The normal range of positive end-expiratory pressure is 3-6 cmH2O. Positive end-expiratory pressure is used clinically to control breathing with a ventilator, or to maintain a certain positive pressure in the airway at the end of expiration when breathing is assisted, and is mainly used to treat hypoxemia and respiratory distress syndrome. Patients are ventilated with a ventilator, which transmits a certain flow of gas into the lungs, and the airway and alveoli are under positive pressure during inspiration. The type of mechanical ventilation in which the oral, airway, and alveolar pressures are above atmospheric pressure during expiration until the airway opens at the end of expiration, it improves the patient’s ventilation and oxygenation and increases the arterial partial pressure of oxygen.