The higher the numbered column through which bubbling occurs, the greater the degree of air leak.By documenting the number, the clinician can monitor air leak increase or decrease.To maintain an effective seal, it is important to keep the chest drainage unit upright at all times and to monitor the water level in the water seal to check for evaporation.Bubbling in the water seal chamber indicates an air leak.
The relief chamber automatically vents excessive negative pressure, thus preventing respiratory compromise from accumulated negativity.
A manual high negativity relief valve is located on top of chest drainage systems (figure 15).
Depressing the high negativity relief valve allows filtered air into the system, relieving negativity and allowing the water level to return to baseline in the water seal. If suction is not operative, or if operating on gravity drainage, depressing the high negativity relief valve can reduce negative pressure within the collection chamber to zero (atmosphere) with the resulting possibility of a pneumothorax.
At the top of the water seal chamber is a high negativity float valve and high negativity relief chamber (figure 13, C).
These safety features maintain the water seal in the event of high negative pressures.