A chest tube (thoracostomy tube) is a flexible catheter inserted into the pleural space, the narrow area between the lung and the chest wall. Its primary purpose is to drain accumulated air, blood, or excess fluid that disrupts the normally negative pressure within the chest cavity. Conditions such as pneumothorax (air), hemothorax (blood), or pleural effusion (fluid) can cause the lung to collapse. The chest tube restores the pressure balance needed for the lung to fully inflate, operating as a one-way valve that allows substances to exit while preventing atmospheric air from re-entering.
How the Drainage System Functions
The chest tube connects directly to a closed chest drainage system, typically a sterile, disposable unit. This modern unit integrates three distinct chambers to manage drainage and pressure regulation: the collection chamber, the water seal chamber, and the suction control chamber. The entire system must be kept upright and below the level of the patient’s chest to facilitate drainage by gravity and prevent fluid backflow.
Fluid and air from the patient first enter the collection chamber, which is calibrated to allow clinicians to measure the volume and assess drainage characteristics. Air then proceeds to the water seal chamber, the component responsible for the bubbling phenomenon. This chamber contains a specific amount of sterile water, often filled to the 2 cm line, into which a tube from the collection chamber is submerged.
The submerged tube creates a water seal that functions as a one-way valve. This permits air to escape from the pleural space and bubble out through the water, while blocking atmospheric air from moving back into the chest cavity. If suction is applied, air then enters the suction control chamber, which regulates the amount of negative pressure applied to the chest.
Interpreting Expected Bubbling and Fluid Movement
Bubbling in the water seal chamber is a specific sign that air is moving out of the patient’s chest and through the drainage system. When a patient has a pneumothorax, intermittent bubbling in this chamber is an expected and positive sign. This bubbling typically occurs when the patient coughs, exhales forcefully, or performs deep breathing exercises, indicating successful air evacuation from the pleural space.
Another sign of a properly functioning system is tidaling, or oscillation, which is the visible rise and fall of the water level in the water seal chamber. Tidaling corresponds precisely with the patient’s respiratory cycle, reflecting continuous pressure changes within the pleural cavity. For a spontaneously breathing patient, the water level rises slightly with inhalation (as intrapleural pressure becomes more negative) and falls with exhalation.
The presence of tidaling confirms that the tube remains patent (open and not blocked by clots or kinks) and is correctly positioned in the intrapleural space. As the lung re-expands and the air or fluid leak resolves, the tidaling movement gradually decreases. The eventual cessation of tidaling is a favorable indication that the lung has fully re-expanded and is filling the pleural space.
Identifying Excessive or Absent Bubbling
While intermittent bubbling is expected with a pneumothorax, continuous, vigorous bubbling in the water seal chamber signals a persistent air leak requiring immediate attention. This continuous stream means air is entering the system constantly, which may indicate a large leak from the patient’s lung (such as a bronchopleural fistula) or a leak within the drainage apparatus itself. Distinguishing the source of the leak is necessary for troubleshooting.
A systemic air leak, caused by a loose connection, a crack in the drainage unit, or a fault in the tubing, can be located by momentarily clamping the tube close to the insertion site. If the bubbling stops immediately upon clamping near the patient, the leak originates from the patient’s chest, signifying a continuing problem with the lung or insertion site. If the bubbling continues, the leak is located in the system connections between the clamp and the drainage unit.
The complete absence of bubbling or tidaling can signal either resolution or a complication. The most desirable reason for cessation is that the air leak has resolved and the lung has fully re-expanded, typically confirmed with a chest X-ray. However, the sudden absence of tidaling is also a warning sign that the chest tube may be blocked by a blood clot, fibrin, or a kink in the tubing.
An obstructed tube is dangerous because it traps air or fluid within the chest, potentially leading to a life-threatening tension pneumothorax. When bubbling or tidaling suddenly stops, the tubing must be immediately inspected for kinks or dependent loops that could be impeding drainage flow. The gentle, continuous bubbling seen in the suction control chamber is a different phenomenon, simply indicating that the wall suction is active and set to the prescribed level.
Patient Monitoring and Safety Guidelines
Maintaining the safety and effectiveness of the chest drainage system requires constant vigilance and adherence to specific protocols. The fundamental safety rule is ensuring the drainage unit remains below the level of the patient’s chest at all times, even during ambulation, to prevent fluid backflow into the pleural space. All connections between the chest tube and the drainage system must be securely taped and checked regularly for tightness.
It is generally not recommended to clamp an actively bubbling chest tube, especially in a patient with a pneumothorax, as this action can rapidly lead to a tension pneumothorax. This life-threatening condition occurs when trapped air builds pressure in the chest, pushing the heart and major blood vessels to the opposite side. Clamping is reserved only for brief troubleshooting moments to locate an air leak or for specific, physician-ordered procedures.
Caregivers should frequently monitor the amount, color, and consistency of the fluid in the collection chamber, noting any sudden increase in drainage, particularly bright red blood exceeding 100 milliliters per hour. Any observed changes in the system, such as a sudden shift from intermittent to continuous bubbling, or the onset of patient distress (like increased shortness of breath or chest pain), warrant immediate notification of the medical team. The patient’s respiratory status and the drainage system function are constantly assessed to ensure the restoration of normal lung function.