Pneumothorax II: Pathophysiology

Physiologically, the pleural space maintains a gentle negative pressure to keep the lungs expanded during breathing.

In a pneumothorax, this balance is disrupted, often due to a rupture in the lung surface or an injury to the chest wall, allowing air to enter the pleural space.

Loss of negative pressure causes the lung to recoil inward, resulting in partial or complete collapse.

When parts of the lung collapse, including the alveoli, oxygen exchange is reduced, leading to shortness of breath and chest pain.

If air continues to accumulate in the pleural space, pressure on the lungs increases, and a tension pneumothorax may develop.

With tension pneumothorax, the lung compresses, shifting the heart and major blood vessels to the opposite side.

Increased intrathoracic pressure compresses the great veins, lowering venous return in heart, leading to hypotension and signs of obstructive shock.