Which option describes the function of the water seal chamber in the chest drainage system?

• A. Maintains negative pressure
• B. Maintains positive pressure in chest
• C. Stores collected blood
• D. Delivers oxygen to patient

Answer: (A)

The water-seal chamber functions as a one-way barrier that preserves negative pressure in the pleural space. As air and fluid leave the chest through the chest tube, the water seal allows air to escape to the atmosphere but prevents atmospheric air from flowing back into the chest. This keeps the intrapleural space subatmospheric, helping the lung to expand and aiding drainage. The other parts of the chest drainage system have different roles—the collection chamber stores drained fluid or blood, and the suction control chamber applies suction when needed. Oxygen delivery is not a function of the drainage system.