Which of the following is the most common cause of death in patients with tension pneumothorax if not promptly relieved?

Explanation

## Pathophysiology of Tension Pneumothorax **Key Point:** Tension pneumothorax is a life-threatening emergency characterized by progressive accumulation of air in the pleural space under positive pressure, causing mediastinal shift and cardiovascular compromise. ### Mechanism of Death in Tension Pneumothorax **High-Yield:** The primary cause of death is **cardiovascular collapse**, not hypoxemia. This occurs through the following sequence: 1. **Progressive air accumulation**: Air enters the pleural space during inspiration but cannot escape (one-way valve effect from the injury). 2. **Increased intrapleural pressure**: Pressure rises above atmospheric, exceeding venous pressure. 3. **Mediastinal shift**: The mediastinum shifts away from the affected side, kinking and compressing the superior and inferior vena cava. 4. **Impaired venous return**: Compression of the vena cava reduces venous return to the right atrium. 5. **Cardiovascular collapse**: Decreased preload leads to decreased cardiac output, hypotension, and shock. ### Clinical Progression | Stage | Finding | Mechanism | |-------|---------|----------| | Early | Dyspnea, chest pain | Lung collapse, mediastinal irritation | | Progressive | Hypotension, JVD, tracheal deviation | Mediastinal shift, impaired venous return | | Decompensation | Cardiac arrest, shock | Complete cardiovascular collapse | **Clinical Pearl:** Tension pneumothorax is a **clinical diagnosis** — do not wait for imaging. Immediate needle decompression (14-16G needle at 2nd intercostal space, midclavicular line) is life-saving and takes precedence over chest X-ray. ### Why Hypoxemia Is Secondary Although the collapsed lung contributes to hypoxemia, the contralateral lung can usually maintain adequate oxygenation if ventilation is preserved. The **cardiovascular compromise** is the lethal factor because it causes shock and tissue hypoperfusion regardless of oxygenation. [cite:ATLS 10th Edition Ch 4]