Under-Water Seal Drainage (UWSD) is a specialized medical system used to re-establish normal negative pressure within the intrapleural space. The normal pleural cavity has sub-atmospheric pressure, which keeps the lungs expanded against the chest wall. When air, blood, or fluid enters this space due to trauma, surgery, or disease, the lung collapses. The UWSD acts as a one-way valve, allowing air and fluid to escape from the chest cavity while preventing anything from flowing back inside.
The system relies on gravity and water seals. The basic setup involves a collection chamber, a water seal chamber, and sometimes a suction control chamber. The distal end of the drainage tube sits beneath 2 centimeters of sterile water. This water column creates a seal: positive pressure from the patient's chest (during expiration or coughing) pushes air out through the water, bubbling it away. When the patient breathes in, the water rises slightly in the tube but cannot enter the chest because the suction or the water level blocks the return path.
Chest tubes connected to UWSD systems are inserted when the integrity of the pleural space is compromised, disrupting normal respiratory mechanics.
Chest drainage systems have evolved from traditional glass three-bottle setups to modern, compact disposable plastic units.
| System Type | Structure & Function |
|---|---|
| Traditional Three-Bottle System | Uses separate bottles for collection, water seal, and suction control. Heavy and prone to breakage. |
| Disposable Three-Chamber System | Combines collection, water seal, and dry or wet suction control into one plastic unit. Most commonly used in modern wards. |
| Dry Suction Systems | Uses a mechanical regulator instead of water to control suction intensity, allowing higher negative pressure levels. |
Modern units simplify nursing care by integrating clear calibration markers on the collection chamber, making fluid volume measurement straightforward and accurate.
Preparing a patient for chest tube insertion requires both physical readiness and psychological reassurance. Nurses must ensure informed consent is signed and gather all necessary equipment, including the drainage system, sterile water, local anesthetic, suture materials, and a dressing kit. Baseline vital signs and oxygen saturation levels must be recorded.
During the procedure, position the patient semi-Fowler's or upright to facilitate access to the pleural space and prevent injury to the diaphragm. Support the patient emotionally and monitor their vital signs continuously for signs of shock, vagal response, or severe pain. Once the doctor inserts the tube and connects it to the UWSD, immediately secure all tubing connections with adhesive tape or plastic cable ties to prevent accidental disconnection. Tape all junctions securely, as an open joint allows atmospheric air to rush into the pleural space.
Regular assessment prevents complications and tracks the patient's recovery. Monitor respiratory rate, breath sounds, and oxygen saturation every four hours or as ordered. Auscultate both lung fields to confirm bilateral air entry; diminished breath sounds on the affected side may indicate persistent lung collapse or a blocked tube.
Observe the water seal chamber closely. Normal tidaling—the rise and fall of the water level with the patient's breathing—indicates that the chest tube is patent and communicating with the pleural space. If tidaling stops abruptly, check for a kinked tube, dependent loops, or complete re-expansion of the lung. Measure drainage output every shift, noting the color and consistency of the fluid. Report any sudden surge of bright red blood exceeding 100 mL per hour immediately, as this signifies active hemorrhage.
Proper day-to-day management ensures the drainage unit functions efficiently. Always keep the drainage system below the level of the patient's chest to prevent gravity from pushing fluid back into the pleural space. Secure the unit to a stable stand or hook it to the bed frame to prevent accidental tipping.
Ensure tubing remains straight without loops or coils that can pool fluid and obstruct airflow. Never clamp a chest tube routinely during patient transfer or ambulation; clamping can quickly cause a tension pneumothorax by trapping accumulating air. Clamping is reserved only for specific moments, such as changing the drainage unit or assessing for an air leak. Maintain the fluid level in the water seal chamber at the 2 cm mark, adding sterile water if evaporation occurs over time.
Emergency situations can arise rapidly with chest drainage systems, requiring swift nursing action.
Chest tubes are removed when the lung has fully re-expanded, air leaks have ceased, and drainage drops to minimal levels (typically less than 100-200 mL per 24 hours). The procedure is usually performed by a doctor, with the nurse assisting.
Explain the procedure to the patient and administer prescribed analgesics 30 minutes beforehand to ease discomfort. Instruct the patient to take a deep breath, hold it, and bear down (Valsalva maneuver) during removal. This increases intrathoracic pressure and prevents air from entering the pleural space as the tube is pulled out. The clinician applies an airtight petroleum jelly gauze dressing immediately over the insertion site, secured with heavy adhesive tape. Post-removal, monitor the patient for recurrence of respiratory distress, check vital signs, and observe the dressing for signs of bleeding or air leakage.