What data about the fluid in the water-seal chamber indicates the chest drainage system is functioning correctly?

• A. Rises with inspiration and falls with expiration
• B. Rises with expiration and falls with inspiration
• C. Stays constant
• D. Fluctuates randomly

Answer: (A)

The data being tested is tidaling in the water-seal chamber—the water level should move with the patient’s breathing. When you inhale, intrapleural pressure becomes more negative, pulling air from the pleural space into the water seal and pushing the water level up. As you exhale, the pressure becomes less negative and air exits through the system, causing the water level to fall. So rising with inspiration and falling with expiration shows the chamber is allowing air to move as the lungs expand and contract, indicating the system is functioning properly. If the level stays constant or shows other patterns, that can point to a blockage or other issue, but the described rise with inspiration and fall with expiration is the hallmark of a working water-seal drainage system.