A normal tidaling pattern is observed in the water-seal chamber. Which statement best describes this finding?

• A. Tidaling is the water level remaining completely still.
• B. The water level fluctuates with breaths, indicating an open pleural space.
• C. There is continuous bubbling in the suction chamber only.
• D. The collection chamber is full.

Answer: (B)

Tidaling in the water-seal chamber shows the chest tube is allowing air to move with breathing, so the pleural space remains connected to the atmosphere. As you inhale, intrapleural pressure becomes more negative and air shifts through the chest tube into the water-seal, causing the water level to move; as you exhale, the pressure relaxes and the water level rises. This breath-driven fluctuation indicates an open pleural space and a functioning drainage system. If tidaling were absent, it could mean the tube is kinked or blocked, the lung has fully re-expanded, or another obstruction is present. Continuous bubbling in the suction chamber reflects suctioning, not tidaling in the water-seal chamber. Continuous tidaling with breaths is therefore the hallmark of a normal, open pleural space.