How should you lower the water seal height when the chest drainage system is connected to suction?

• A. Temporarily depress the manual vent located on top of the drain until the water column lowers to the desired level
• B. Increase the suction regulator to maximum
• C. Remove the chest tube
• D. Close the drainage bottle valve

Answer: (A)

Lowering the water seal height while the system is on suction is done by briefly depressing the manual vent on top of the drainage unit. Opening the vent briefly allows air to escape from the suction-control chamber, which reduces the suction effect on the water column and lets the water level in the seal drop to the desired height. After achieving the target level, stop venting and maintain the suction as calibrated.

Raising suction to the maximum isn’t a direct way to control the water seal height and can risk tissue injury. Removing the chest tube or closing the drainage bottle valve would stop drainage or disrupt the system rather than adjust the water seal height.