Pleural Cavity

cavitas pleuralis

The pleural cavity is the potential space between the visceral pleura (covering the lung surface) and the parietal pleura (lining the thoracic wall, diaphragm, and mediastinum). Normally it contains 5-15 mL of pleural fluid providing lubrication. The subatmospheric intrapleural pressure (-5 cmH2O at rest, -8 cmH2O during inspiration) maintains lung expansion. The pleural recesses — costodiaphragmatic (most dependent) and costomediastinal — are potential spaces that fill last as lung expands.

Region: Chest

Clinical Relevance

Clinical Notes

Pneumothorax (air in the pleural cavity) equalises the intrapleural pressure, collapsing the lung. Tension pneumothorax occurs when air accumulates under positive pressure, shifting the mediastinum and impeding venous return. Pleural effusion fluid accumulates in the dependent costodiaphragmatic recess, detectable by ultrasound or CXR. Thoracocentesis targets the costodiaphragmatic recess for fluid drainage. Malignant pleural mesothelioma arises from pleural mesothelial cells. Pleurodesis obliterates the pleural cavity to prevent recurrent effusion or pneumothorax.

Pathology

Common Injuries & Conditions

Tension Pneumothorax from Pleural Cavity Air Under Pressure

Penetrating chest injury or mechanical ventilation creates a one-way valve causing progressive air accumulation in the pleural cavity under positive pressure, compressing the lung and shifting the mediastinum contralaterally impairing venous return; immediate needle decompression at the second intercostal space mid-clavicular line followed by chest drain insertion is life-saving.