Trapped Lung (Lung Entrapment): Diagnosis and Management
Immediate Answer
Place an indwelling pleural catheter (IPC) as first-line treatment for trapped lung—pleurodesis is contraindicated and will fail because the visceral and parietal pleura cannot appose. 1, 2
Definition and Pathophysiology
Trapped lung is a mechanical condition where a fibrous visceral pleural peel from remote, inactive pleural inflammation prevents the lung from expanding to fill the hemithorax, creating a persistent pleural space that fills with fluid by hydrostatic equilibrium alone. 1, 3
Lung entrapment differs in that the visceral pleural peel results from an active pleural process—malignancy, ongoing infection, or active inflammation—where the underlying disease is the primary problem. 1, 4, 5
Diagnostic Approach
Key Clinical Clues
- Absence of contralateral mediastinal shift despite a large effusion volume is the hallmark radiographic finding. 1, 6
- Dyspnea is the most common symptom, though some patients remain asymptomatic. 1
- Post-thoracentesis chest pain preventing complete drainage or development of pneumothorax suggests unexpandable lung. 4, 5
Diagnostic Confirmation
- Initial pleural fluid pressure <10 cm H₂O at thoracentesis strongly suggests trapped lung. 1, 6
- Pleural manometry demonstrating abnormal (incomplete) lung expansion during drainage supports the diagnosis. 1, 4, 5
- CT chest with pleural contrast (venous phase) demonstrates visceral pleural thickening and the fibrous peel. 2, 4
- Pleural fluid analysis should exclude active malignancy or infection (cell count, differential, protein, LDH, glucose, pH, cytology). 2
- Bronchoscopy is indicated when endobronchial obstruction is suspected (hemoptysis, atelectasis, or large effusion without mediastinal shift). 2, 6
Management Algorithm
First-Line Treatment: Indwelling Pleural Catheter
The European Respiratory Society and European Association for Cardio-Thoracic Surgery recommend IPCs as primary treatment for trapped lung. 1, 2
Evidence Supporting IPC Use:
- Symptomatic improvement in >94% of patients across five studies (133 patients total). 1, 2
- Shorter hospital stays and reduced morbidity compared to alternative interventions. 1, 2
- Higher effusion control rates and better dyspnea-free exercise scores than talc pleurodesis. 2
- IPCs can remain in situ until death in most patients. 1
IPC Complications (Rare but Important):
What NOT to Do: Avoid Pleurodesis
Pleurodesis is contraindicated in trapped lung and will fail because the visceral and parietal pleura cannot appose—the fundamental requirement for successful pleurodesis. 7, 1, 2
- Attempting pleurodesis subjects patients to unnecessary procedures, prolonged hospitalization, and significant pain without therapeutic benefit. 2
- Before any pleurodesis attempt, always confirm: (1) complete lung expansion radiographically, (2) absence of contralateral mediastinal shift, and (3) initial pleural pressure <10 cm H₂O. 7, 1, 6
Exception for Partial Expansion:
- In patients with partial lung re-expansion who are unsuitable for surgery, pleurodesis may still be attempted and can provide symptomatic relief in select cases (9 of 10 patients in one study). 7
- However, this applies to incomplete expansion from other causes, not true trapped lung with a mature fibrous peel. 7
Alternative Treatment Options
Video-Assisted Thoracoscopic Decortication (VATS):
- May be considered for younger, high-performance-status patients with benign trapped lung, though supporting evidence is limited. 1, 8
- Surgical decortication is the only definitive therapy but is reserved for symptomatic patients with incapacitating dyspnea. 3, 9
Pleuroperitoneal Shunts:
- No longer recommended due to high complication rates. 1
Intrapleural Fibrinolytic Therapy:
- Remains investigational with limited evidence. 2
Critical Pitfalls to Avoid
- Failure to recognize trapped lung before attempting pleurodesis leads to procedural failure, unnecessary patient suffering, and wasted resources. 1
- Do not wait for pleural fluid drainage to decrease to <150 mL/day before intervening—radiographic confirmation of lung expansion is more important than drainage volume. 7
- Controlled drainage of large effusions is essential: avoid evacuating >1–1.5 L at one time or drain at ~500 mL/hour to prevent re-expansion pulmonary edema. 7
- Discontinue aspiration if the patient develops chest discomfort, persistent cough, or vasovagal symptoms. 7