If the chest tube system is functioning properly, what pressure is reestablished in the pleural space?

• A. Zero pressure in the pleural space
• B. Positive pressure in the pleural space
• C. Negative pressure in the pleural space
• D. No change in intrapleural pressure

Answer: (C)

Lung expansion relies on a negative intrapleural pressure keeping the lung stretched against the chest wall. A functioning chest tube system restores that negative pressure in the pleural space by removing air or fluid and, if needed, applying suction. When the system is working, the intrapleural pressure becomes negative again (negative relative to atmospheric pressure), which allows the lung to re-expand. Zero or positive pressure in the pleural space would not support expansion and could worsen collapse, and no change in intrapleural pressure means the lung wouldn’t re-expand.