**Core Concept**
Positive End-Expiratory Pressure (PEEP) is a ventilatory strategy used to maintain alveolar recruitment and prevent alveolar collapse in mechanically ventilated patients. It involves maintaining a positive pressure in the lungs at the end of expiration, thereby improving oxygenation and lung compliance.

**Why the Correct Answer is Right**
PEEP plays a crucial role in maintaining lung volume, reducing atelectasis, and improving gas exchange. It also helps to prevent the collapse of small airways and alveoli, thereby improving lung mechanics. PEEP can be adjusted based on the patient's response, including changes in oxygenation, lung compliance, and hemodynamics.

**Why Each Wrong Option is Incorrect**
**Option A:** PEEP can be used to improve oxygenation in patients with acute respiratory distress syndrome (ARDS). This is a valid role of PEEP, so it is not the correct answer.
**Option B:** PEEP can also be used to improve lung compliance in patients with chronic obstructive pulmonary disease (COPD). This is another valid role of PEEP, so it is not the correct answer.
**Option C:** PEEP can be used to reduce the work of breathing in patients with respiratory failure. This is a valid role of PEEP, so it is not the correct answer.

**Clinical Pearl / High-Yield Fact**
PEEP should be titrated based on the patient's response to avoid overdistension of the lungs, which can lead to volutrauma and lung injury.

**Correct Answer: D.**