- Definition
- Pneumothorax is the presence of air in the pleural space, resulting in loss of negative intrapleural pressure and partial or complete lung collapse.
- Normal pleural physiology
- The pleural space lies between the visceral and parietal pleura
- Contains a small amount of lubricating serous fluid
- Intrapleural pressure is negative relative to atmospheric pressure
- This negative pressure keeps the lung expanded against the thoracic wall
- Pathophysiology
- Breach in pleura allows air to enter pleural space
- Negative intrapleural pressure is lost, approaching atmospheric pressure
- Lung recoils due to elastic properties, leading to partial or complete collapse
- Alveolar ventilation in affected areas ceases → V/Q mismatch and hypoxia
- Mediastinal shift may occur in large or tension pneumothoraces, worsening cardiorespiratory compromise