A chest tube (thoracostomy tube) is a flexible catheter inserted into the pleural space to drain air, blood, or excess fluid, allowing the collapsed lung to re-expand. Management requires continuous drainage and complication prevention. Clamping the tube—temporarily stopping the flow—is rare, reserved for specific short-term diagnostic or maintenance purposes, or used as a planned test before removal.
Understanding Chest Tube Function
The pleural space maintains negative pressure, keeping the lungs expanded. Disruption by air (pneumothorax), blood (hemothorax), or fluid (pleural effusion) causes lung collapse. A chest tube restores negative pressure by providing a one-way path for these substances to exit.
The tube connects to a closed drainage system, typically including a water seal chamber. The water seal acts as a one-way valve, allowing air and fluid to escape during exhalation while preventing outside air from entering the pleural space. Suction (often -10 to -20 cm H\(_{2}\)O) may be applied to accelerate removal and promote lung re-expansion. This continuous function maintains the necessary pressure gradient.
Situations Requiring Temporary Clamping
Temporary clamping is a high-risk procedure indicated only for brief, specific procedural interruptions, not for routine patient movement. A common indication is the need to quickly change the drainage system, such as replacing a full collection unit. The tube is clamped only for the few seconds required to maintain the seal and sterility while connecting the new unit.
Clamping is used diagnostically to locate the source of a persistent air leak visible in the water seal chamber. By momentarily clamping the tube at various points, staff isolate whether the leak originates from the patient’s chest, the insertion site, or a loose connection. If the leak stops immediately after clamping at the insertion site, the issue is confirmed to be from the patient’s lung or wound. This must be done quickly using specialized rubber-tipped clamps.
Clamping may be necessary if the tubing accidentally disconnects, causing immediate loss of the water seal. The tube is clamped for the minimal time needed to cleanse and reconnect the system, preventing air from rushing into the pleural space. Clamping may also be applied during patient transport if the drainage unit cannot be kept upright, preventing fluid backflow. This is generally avoided, however, as the risk often outweighs the benefit.
When Clamping is Dangerous and Strictly Avoided
Clamping a chest tube when not indicated creates risk by turning the drainage system into a closed container. The primary contraindication is an ongoing air leak, visible as bubbling in the water seal chamber. If the tube is clamped while air leaks from the lung, the air becomes trapped in the pleural space.
This trapped air rapidly increases pressure, leading to a tension pneumothorax. This emergency occurs when high pressure compresses the lung and shifts the mediastinum, including the heart and major blood vessels, to the opposite side of the chest. The compression impairs the heart’s ability to fill with blood, causing a sudden drop in blood pressure and oxygen saturation. Symptoms include acute shortness of breath, increased heart rate, and visible distension of the neck veins.
Clamping is also avoided when the tube is actively draining a large volume of fluid, such as blood (hemothorax) or a pleural effusion. Blocking the tube forces fluid to accumulate inside the chest cavity. This accumulation exerts pressure on the lung and heart, hindering expansion and cardiac function, defeating the purpose of the chest tube. The tube should generally be left open to gravity drainage or suction to ensure continuous evacuation.
The Protocol for Trial Clamping Before Removal
A “trial clamp” is a diagnostic procedure performed before removal, distinct from brief procedural clamping. This protocol is used only after the patient meets pre-removal criteria, including an absence of an air leak (e.g., 12 to 24 hours) and minimal fluid drainage (e.g., less than 200 milliliters over 24 hours). The purpose is to determine if the lung remains fully expanded and if the patient can safely tolerate having the tube blocked.
The procedure involves clamping the tube for a set duration, often 4 to 24 hours, while the patient is monitored for signs of respiratory distress. Symptoms assessed include shortness of breath, chest pain, or a drop in oxygen levels, which require immediate unclamping. A chest X-ray confirms that no fluid or air has reaccumulated. If the patient remains clinically stable and the X-ray is clear, the trial is successful, and the tube is removed.