What is the primary purpose of Positive End-Expiratory Pressure (PEEP)?

The primary purpose of Positive End-Expiratory Pressure (PEEP) is to maintain a preset positive airway pressure during expiration. By doing so, PEEP helps to keep the alveoli open and improves oxygenation. When the patient exhales, instead of allowing the pressure in the lungs to drop to zero, PEEP keeps a baseline pressure, which helps prevent the collapse of alveoli that could lead to atelectasis.

This mechanism enhances gas exchange and maintains functional residual capacity, thus reducing shunting and improving oxygenation. It is particularly beneficial in patients with conditions like acute respiratory distress syndrome (ARDS) or other forms of hypoxemia, allowing for better ventilation and oxygenation strategies without requiring excessively high airway pressures.

Other choices focus on different aspects of ventilation but do not capture the core role of PEEP in managing airway pressure during expiration, which is crucial for lung function and oxygenation in critical care settings.