What indicates an air leak in a chest tube?

Continuous bubbling in the water seal chamber of a chest tube system is indicative of an air leak. This occurs because the presence of air in the system disrupts the normal function of the water seal, creating bubbles that consistently rise. In a properly functioning chest tube system, any bubbling should be intermittent rather than continuous. Continuous bubbling suggests that air is entering the system from an external source, which could compromise the effectiveness of the chest drainage and indicate a potential problem with the chest tube placement or integrity.

The other options do not signify an air leak. The absence of drainage may reflect other issues, such as a blockage or the lung fully re-expanding, rather than an air leak. A decreased respiratory rate is related to the patient's overall respiratory status, but it does not directly indicate an air leak. Intermittent bubbling, on the other hand, can be a normal finding when a patient is breathing and may reflect changes in intrathoracic pressure rather than a significant air leak. Therefore, the presence of continuous bubbling is the key indicator that suggests an air leak is occurring.