**Core Concept**
Positive End-Expiratory Pressure (PEEP) is a ventilatory technique used to maintain a higher lung volume at the end of expiration, improving oxygenation in patients with respiratory distress. It involves the application of positive pressure to the airways during the end-expiratory phase of the respiratory cycle. This technique is commonly used in mechanically ventilated patients to prevent alveolar collapse and improve gas exchange.

**Why the Correct Answer is Right**
PEEP works by increasing the pressure within the alveoli, thereby preventing atelectasis (alveolar collapse) and improving the functional residual capacity (FRC) of the lungs. This increase in pressure also helps to recruit collapsed alveoli and improve oxygenation. PEEP is typically set between 5-15 cmH2O, with higher pressures required for more severe respiratory distress.

**Why Each Wrong Option is Incorrect**
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**Clinical Pearl / High-Yield Fact**
PEEP should be titrated carefully to avoid overdistension of the lungs, which can lead to ventilator-induced lung injury (VILI). A common mnemonic to remember the effects of PEEP is "PEEP: Prevents Atelectasis, Enhances Oxygenation, and Elevates Pressure".

**Correct Answer:** Correct Answer: .