What is the primary purpose of a chest drainage system attached to a chest tube?

• A. To re-establish negative pleural pressure
• B. To drain cerebrospinal fluid
• C. To monitor blood glucose
• D. To measure arterial blood gas levels

Answer: (A)

The main idea here is restoring the negative pressure in the pleural space so the lung can re-expand. A chest tube connected to a drainage system removes air or fluid from the pleural space, allowing intrapleural pressure to become negative again. The water-seal and suction components help ensure one-way flow and prevent air from re-entering, which supports the lung's expansion and improves ventilation. The other options describe activities unrelated to chest drainage—cerebrospinal fluid drainage, blood glucose monitoring, or arterial blood gas measurement.