What are the steps for setting up a chest tube to water seal?

Setting Up a Chest Tube to Water Seal

All chest tubes must be connected to a unidirectional flow drainage system (underwater seal bottle) that is kept below the level of the patient's chest at all times. 1

Essential Setup Steps

1. Prepare the Underwater Seal System

• Place the drainage tube under water at a depth of approximately 1–2 cm in the underwater seal bottle 1
• Ensure the side vent either allows escape of air to atmosphere or connects to a suction pump 1
• Verify the system allows unidirectional flow of air or fluid out of the chest only 1

2. Position the Drainage System

• Keep the underwater seal bottle below the level of the patient's chest at all times 1
• This positioning is critical and must be maintained during all patient activities, including transport 1
• Secure the bottle in a stable location to prevent it from being knocked over 1

3. Connect the Chest Tube

• Attach the chest tube directly to the underwater seal drainage system after securing the tube to the patient 1
• Ensure all connections are secure and airtight 1
• Verify the tube is not kinked or obstructed 2

Initial Management Decisions: Suction vs. Water Seal Alone

Water Seal Without Suction (Preferred Initial Approach)

• Start with water seal alone (gravity drainage) for most patients 1
• This approach is supported by evidence showing water seal is superior to suction for stopping air leaks after pulmonary resection 3
• Water seal alone is safe for most patients with air leaks and pneumothorax 4

When to Add Suction

• Apply suction if the lung fails to reexpand quickly with water seal alone 1
• If suction is used, apply it via the underwater seal at a pressure of 5–10 cm H₂O 1, 2
• Suction may be applied immediately after chest tube placement as an alternative approach, though this has less consensus 1
• Appropriately trained nursing staff must supervise the use of chest drain suction 1, 2

Monitoring the System

Assess for Proper Function

• Look for respiratory swing in the fluid within the chest tube—this confirms tube patency and proper pleural cavity position 1, 2
• Observe for bubbling in the water chamber:
  • Bubbling indicates air in the pleural space (pyopneumothorax) 1, 2
  • Continuous bubbling suggests an ongoing visceral pleural air leak 1, 2
  • Continuous bubbling in patients on suction may also indicate the drain is partly out of the thorax with a tube hole open to atmosphere 1

Critical Safety Rule

• Never clamp a bubbling chest drain 1, 2
• Clamping a bubbling drain can lead to the potentially fatal complication of tension pneumothorax 1, 2
• If a drain must be clamped for specific indications (e.g., after fibrinolytic instillation), it should be immediately unclamped if the patient develops breathlessness or chest pain 1

Special Considerations

Initial Drainage Limits

• Limit initial drainage to 10 ml/kg body weight to prevent re-expansion pulmonary edema 1, 2
• After draining this amount, clamp the drain for 1 hour if not bubbling 1, 2
• In adults and larger children/adolescents, drain no more than 1.5 liters at one time or slow drainage to approximately 500 ml/hour 2

Disconnecting Suction Temporarily

• Brief disconnection from suction for radiographs or mobilization is acceptable if the underwater seal bottle remains below chest level 1
• Ensure all staff (nursing, portering, patient, family) understand the bottle must stay below chest level 1

Risk Factors for Water Seal Failure

• Large air leaks (expiratory leak ≥4/7 on leak meter scale) predict failure of water seal alone 4, 3
• Pneumothorax >8 cm in size increases risk of requiring suction 4
• In these cases, consider applying suction earlier rather than waiting for water seal to fail 4, 3