Positive end-expiratory pressure (PEEP) is a critical aspect of mechanical ventilation used in the treatment of patients with respiratory failure. PEEP is a level of pressure applied at the end of expiration to keep the airways open and prevent the collapse of alveoli in the lungs. This helps improve oxygenation and prevents atelectasis (lung collapse). PEEP is commonly used in conditions such as acute respiratory distress syndrome (ARDS), pneumonia, and other forms of respiratory failure. Research in this area focuses on determining the optimal level of PEEP, its effect on gas exchange, lung compliance, and patient outcomes. Several studies have shown that appropriate use of PEEP can improve patient outcomes and reduce the risk of complications associated with mechanical ventilation.