Trapped Lung (Hydrops Ex‑Vacuo) – Evidence‑Based Guideline Summary

Definition & Pathophysiology

Trapped lung is a mechanical condition in which the lung cannot fully expand to fill the hemithorax because a fibrous visceral pleural peel, formed after remote inactive pleural inflammation, restricts expansion. European Respiratory Society 1
The fibrous peel prevents the visceral and parietal pleura from opposing each other, creating a persistent pleural space that fills with fluid solely by hydrostatic equilibrium. European Respiratory Society 1

Trapped lung: fibrous peel resulting from past, inactive inflammation (e.g., old parapneumonic effusion, prior cardiac surgery, chest trauma). European Respiratory Society 1
Lung entrapment: visceral pleural peel produced by an active pleural process such as malignancy or ongoing infection. European Respiratory Society 1

Dyspnea is the most common symptom; a subset of patients may be asymptomatic. American Journal of Respiratory and Critical Care Medicine 2
A key radiographic clue is the absence of contralateral mediastinal shift despite a large effusion volume. American Journal of Respiratory and Critical Care Medicine 2

Initial pleural fluid pressure < 10 cm H₂O at thoracentesis strongly suggests trapped lung. American Journal of Respiratory and Critical Care Medicine 2
Pleural manometry demonstrating abnormal (incomplete) lung expansion during drainage supports the diagnosis. European Respiratory Society 1

Pleurodesis is contraindicated and will fail in trapped lung because the visceral and parietal pleura cannot appose. Praxis Medical Insights 3

The European Respiratory Society and the European Association for Cardio‑Thoracic Surgery recommend indwelling pleural catheters (IPCs) as the primary treatment for trapped lung. Praxis Medical Insights 4
IPCs achieve symptomatic improvement in >94 % of patients. Praxis Medical Insights 4
Use of IPCs is associated with shorter hospital stays and reduced morbidity compared with alternative interventions. Praxis Medical Insights 4

Catheter longevity: IPCs can remain in situ until death in most patients. European Respiratory Journal 5
Serious complications (though rare) include empyema and catheter fracture. European Respiratory Journal 5

Video‑assisted thoracoscopic decortication may be considered for younger, high‑performance‑status patients with benign trapped lung, although supporting evidence is limited. Praxis Medical Insights 4
Pleuroperitoneal shunts are no longer recommended because of high complication rates. Praxis Medical Insights 4

Failure to recognize trapped lung before attempting pleurodesis leads to procedural failure, unnecessary patient suffering, and wasted resources. Praxis Medical Insights 3
Prior to pleurodesis, always assess for complete lung expansion by (1) checking for absence of contralateral mediastinal shift on imaging and (2) measuring initial pleural pressure < 10 cm H₂O during drainage. American Journal of Respiratory and Critical Care Medicine 2

Pleurodesis should not be performed in patients with trapped lung because the fibrous visceral peel prevents apposition of the visceral and parietal pleura, making the procedure inevitably unsuccessful. 6

In patients who exhibit only partial lung re‑expansion and are unsuitable for surgical decortication, pleurodesis may still be considered; a small study reported symptomatic relief in 9 out of 10 such patients. (Evidence based on a single‑center case series.) 6

Do not postpone therapeutic intervention until pleural fluid output falls below 150 mL/day; radiographic confirmation of lung expansion should guide timing instead. 6
When draining large effusions, limit removal to ≤ 1–1.5 L per session and maintain a drainage rate of approximately 500 mL/hour or slower to avoid re‑expansion pulmonary edema. (Guidance derived from observational data.) 6

Immediately discontinue aspiration if the patient experiences chest discomfort, persistent cough, or signs of a vasovagal reaction, as these may indicate complications. 6