What does PEEP stand for in mechanical ventilation?

• A. Positive End-Inspiratory Pressure
• B. Positive End-Expiratory Pressure
• C. Peak End-Expiratory Pressure
• D. Pressure End-Expiratory

Answer: (B)

PEEP stands for Positive End-Expiratory Pressure, a ventilator setting that maintains a small amount of pressure in the lungs at the end of each exhalation. This positive pressure keeps the alveoli from collapsing after expiration, preserving open airways and increasing functional residual capacity, which improves oxygen exchange and helps treat hypoxemia often seen with lung injury or ARDS. By preventing end-expiratory collapse, PEEP reduces shunt and can make oxygen delivery more effective. It does, however, raise baseline intrathoracic pressure, which can decrease venous return and affect cardiac output, so clinicians adjust it carefully and monitor hemodynamics. Typical starting values are around 5 cm H2O, with adjustments up or down based on oxygenation status and lung mechanics. The other phrases describe wrong timing or nonstandard terminology, since PEEP specifically refers to the pressure maintained at the end of expiration, not during inspiration or as a generic pressure term.