A chest tube (thoracostomy tube) is a flexible catheter inserted through the chest wall into the pleural space, the area between the lung and the inner chest wall. The primary function of this procedure is to drain accumulated substances—air, fluid, or blood—to restore the negative pressure needed for the lungs to fully expand. The procedure requires connecting the tube to a specialized drainage system that incorporates a “water seal.” This water seal acts as a one-way valve, allowing air and fluid to escape the chest cavity while preventing atmospheric air from being sucked back in, which could cause the lung to collapse. This article provides educational insights into the placement and mechanics of this system, but it is not a substitute for professional medical instruction.
Essential Pre-Procedure Preparation
Chest tube insertion is indicated for conditions that compromise lung mechanics, such as a collapsed lung (pneumothorax), blood accumulation (hemothorax), or excessive fluid buildup (pleural effusion). Before the procedure, obtaining informed consent is required, along with implementing universal precautions and aseptic technique to minimize infection risk. Necessary equipment, including the chest tube, surgical instruments, antiseptic solution, and the drainage system, must be readily available and sterile.
The patient is positioned in a semi-Fowler’s position (about a 45-degree angle) with the arm on the affected side raised above the head. This positioning exposes the midaxillary area, the preferred insertion site, and spreads the ribs apart to widen the intercostal space. Proper positioning also lowers the diaphragm, reducing the possibility of misplacing the tube into the abdominal cavity.
Determining the Insertion Site and Anesthesia
Safe chest tube placement relies on identifying the “Triangle of Safety,” an anatomical zone that helps avoid damage to surrounding organs. This area is bordered by the lateral edge of the pectoralis major muscle anteriorly, the anterior border of the latissimus dorsi muscle posteriorly, and the level of the fifth intercostal space inferiorly. The standard insertion site falls within this triangle, typically at the fourth or fifth intercostal space along the anterior to mid-axillary line.
Local anesthesia, usually lidocaine, is administered to the skin and deeper tissues down to the parietal pleura, which is highly sensitive. The anesthetic needle must trace a path over the superior margin of the rib to avoid the neurovascular bundle (artery, vein, and nerve) that runs along the underside of each rib. While infiltrating the anesthetic, the clinician aspirates with the syringe to confirm the presence of air or fluid, verifying the depth and correct location of the pleural space before the incision.
Detailed Steps for Chest Tube Insertion
Once the site is anesthetized, a small transverse incision is made through the skin and subcutaneous tissue over the targeted intercostal space. The path to the pleural space is created using blunt dissection, where a closed instrument, such as a Kelly clamp, separates the muscle and fascia layers. The clamp is advanced over the top edge of the lower rib to ensure the neurovascular bundle is not injured.
The clamp is then used to pierce the parietal pleura with a controlled push, often resulting in a noticeable “pop” or a rush of air or fluid, confirming entry into the pleural space. The opening is stretched by opening and withdrawing the clamp, and the operator’s index finger is inserted through the tract. This finger sweep confirms entry into the pleural space and dislodges any adhesions that might prevent lung re-expansion.
The chest tube is grasped with the clamp and guided into the pleural cavity, using the inserted finger as a guide. For a pneumothorax, the tube is directed toward the top of the chest (apically); for fluid drainage, it is directed toward the back and bottom (basally). The tube is advanced until the last drainage hole, the “sentinel eye,” is entirely within the chest cavity. Tube position is confirmed by fluid or fogging condensation visible inside the tube.
Mechanics of the Water Seal Drainage System
The chest tube is immediately connected to a closed drainage system, which typically consists of three chambers. The first is the collection chamber, which serves as a reservoir for the air and fluid draining from the chest. This chamber is calibrated for measuring the volume of output, which is marked and monitored to assess the patient’s condition.
The second is the water seal chamber, containing sterile water that acts as the one-way valve. The tube from the patient extends below the water surface, creating a barrier that allows air to bubble out but prevents outside air from being drawn back into the chest. This chamber monitors air leaks; continuous bubbling indicates a leak from the lung or a break in the system.
The third component is the suction control chamber, used when controlled negative pressure is needed to evacuate the chest cavity faster. In a wet suction system, the depth of the water column (often 20 cm) determines the maximum negative pressure applied. Whether suction is active or the system is on gravity drainage, the water seal chamber exhibits “tidaling,” the normal rising and falling of the water level with the patient’s breathing, confirming connection to pleural pressure changes.
Securing the Tube and Initial Monitoring
After the chest tube is placed and connected to the water seal system, it must be securely fastened to the chest wall. A heavy, nonabsorbable suture material, such as silk, is used to secure the tube and partially close the incision. One common method involves tying a suture across the incision and then wrapping the long ends tightly around the tube multiple times to create a secure anchor.
An occlusive, airtight dressing is applied over the insertion site to prevent air leakage. A post-procedure chest X-ray is mandatory and obtained immediately to verify the correct position of the tube tip and ensure the lung has begun to re-expand. Initial monitoring includes tracking the patient’s vital signs and respiratory status for improvement or complications. The color and volume of the fluid draining into the collection chamber are also assessed and recorded regularly to track clinical progress.