**Question:** Which of the following is not seen in ARDS

A. Hypoxia
B. Hypercapnia
C. Increased lung compliance
D. Increased pulmonary vascular resistance

**Core Concept:** Acute Respiratory Distress Syndrome (ARDS) is a severe lung injury characterized by bilateral pulmonary infiltrates, hypoxia, and increased pulmonary vascular resistance. Its pathophysiology involves inflammation, alveolar edema, and impaired gas exchange. The primary aim of treatment is to maintain oxygenation and minimize lung injury.

**Why the Correct Answer is Right:** Increased lung compliance is a feature of pulmonary edema, not ARDS. In ARDS, lung compliance remains normal or is even decreased due to alveolar collapse.

**Why Each Wrong Option is Incorrect:**

Option A: Hypoxia - Hypoxia is a key feature of ARDS, with low oxygen saturation and low arterial oxygen tension.

Option B: Hypercapnia - Hypercapnia is less common in ARDS, but can occur if ventilation-perfusion mismatch is severe. ARDS primarily leads to hypoxia, not hypercapnia.

Option C: Increased lung compliance - As explained above, lung compliance is decreased in ARDS due to alveolar collapse, not increased.

Option D: Increased pulmonary vascular resistance - ARDS causes pulmonary hypertension due to hypoxia, which leads to increased pulmonary vascular resistance. This is different from the correct answer of increased lung compliance.

**Clinical Pearl:** In clinical practice, understanding the key features of ARDS helps in distinguishing it from other lung conditions and selecting appropriate treatment strategies.

**Correct Answer:** C. Increased lung compliance