How to Test for Air Leak in a Chest Tube
The definitive method to test for an air leak in a chest tube is visual assessment of the underwater seal collection system—continuous or intermittent bubbling confirms the presence of an air leak, while observing the respiratory swing of fluid confirms tube patency and proper positioning. 1
Primary Assessment Method
- Observe the underwater seal chamber for bubbling, which is the gold standard sign of an air leak in the pleural space 1
- Continuous bubbling indicates an ongoing visceral pleural air leak, while intermittent bubbling (occurring only during certain phases of respiration like coughing or deep breathing) suggests a smaller air leak 1
- Check for respiratory swing (tidaling) of fluid in the chest tube, which confirms the tube is patent and properly positioned in the pleural cavity 1
Systematic Testing Approach
When assessing a chest tube for air leak, follow this algorithm:
- Connect the chest tube to a unidirectional flow drainage system positioned below the patient's chest level at all times 1
- Observe the water seal chamber at rest during normal breathing 1
- Have the patient cough or take a deep breath to provoke any intermittent air leaks 2
- Ask the patient to breathe out against resistance (Valsalva maneuver) to maximize detection of smaller leaks 2
Distinguishing Parenchymal from Peri-Tube Air Leaks
A critical but often overlooked pitfall is that bubbling may result from air entering around the chest tube insertion site rather than from the lung itself:
- Attach a CO₂ monitoring device (capnography) to the chest drain to differentiate between parenchymal air leak (which will show CO₂) versus air entering from the insertion site (which will not show CO₂) 3
- This simple test guides whether the problem is a true pulmonary air leak requiring continued drainage versus an inadequate seal at the insertion site requiring local management 3
Quantification Methods
For more precise assessment, particularly in postoperative settings:
- Digital airflow measurement devices can quantify air leaks in ml/breath or ml/minute, with values ranging from 0.25-45 ml/breath and 5-900 ml/minute 2
- These systems allow objective tracking of air leak resolution and inform timing of chest tube removal without requiring clamping tests 2
Critical Safety Considerations
- Never clamp a bubbling chest tube, as this can cause tension pneumothorax, which is potentially fatal 1, 4, 5
- If there is sudden cessation of drainage or bubbling, check for tube obstruction by flushing with normal saline, and inspect for kinking (especially with small soft drains in mobile patients) 1
- All chest tube management should occur on specialized wards with trained staff 1
Clinical Decision Points Based on Air Leak Duration
- At 48 hours: If air leak persists or pneumothorax fails to re-expand, refer to a respiratory physician for complex drain management decisions 1
- At 4 days: A persistent air leak beyond this point warrants surgical evaluation rather than continued conservative management 1, 4
- For patients with underlying lung disease (COPD, secondary pneumothorax), consider earlier intervention at 2-4 days due to higher risk of persistent air leak 4
Optimal Drainage Settings During Air Leak
- Water seal is superior to wall suction for stopping most air leaks 6, 7
- Apply suction (-10 to -20 cm H₂O) only if the patient has a large leak (>expiratory grade 3), develops subcutaneous emphysema, or experiences an expanding pneumothorax causing hypoxia 1, 6, 7
- Even in patients with both a pneumothorax and an air leak, water seal is safe and effective in 84% of cases 7