What is the purpose of the water-seal chamber in a chest tube drainage system?

The water-seal chamber in a chest tube drainage system is designed primarily to create a one-way valve that allows air or fluid to escape from the pleural space while preventing the backflow of air into that space. When a patient has a pneumothorax or pleural effusion, it’s crucial to remove air or excess fluid to allow the lung to re-expand. The water-seal chamber fills with a sterile fluid, typically water, which establishes a seal. This setup allows air to exit from the chest but not to re-enter, thus maintaining negative pressure in the pleural space and promoting lung re-expansion.

While the other options mention functions related to gases and fluid management, they do not accurately capture the primary function of the water-seal chamber. The chamber does not sterilize gases, provide suction directly (beyond aiding drainage), or collect serous or sanguineous fluids; instead, it focuses on controlling the one-way flow of air and fluid. This function is vital in respiratory care and clinical management of thoracic conditions.