Respirology/ ICU

Trapped Lung vs. Lung Entrapment

Though often used synonymously; Trapped Lung and Lung Entrapment technically describe separate entities along the same clinical spectrum.

Trapped lung refers to the sequelae of inflammatory or malignant processes which has resulted in the formation of a thick fibrous peel involving the visceral pleura. The pleural peel (in the absence of active inflammation) is now the primary clinical problem. These patient are often asymptomatic despite their unexpanded lung, indicative of a chronic process often due to a remote insult. Dyspnea will often worsen with thoracentesis due to rapid drops in pleural pressure.

Lung entrapment denotes an unexpandable lung despite adequate drainage due to an ACTIVE infection, malignancy or inflammatory process (i.e hemothorax, rheumatoid pleuritis). In these instances, the underlying inflammatory or malignant process is the primary problem, which may or may not be complicated by visceral pleural involvement. There also exist non-pleural lung entrapment such as endobronchial lesions or bronchogenic carcinoma causing increased elastic recoil of the lung and resultant atelectasis. Dyspnea will typically improve with thoracentesis.

*Again, many clinicians use these terms synonymously. Both may result in hydropneumothorax being present post drainage due to pneumothorax ex vacuo.


  1. Huggins JT, Doelken P, Sahn SA. The unexpandable lung. F1000 Med Rep. 2010;2:77. Published 2010 Oct 21. doi:10.3410/M2-77
  2. Saha BK, Hu K, Shkolnik B. Non-expandable lung: an underappreciated cause of post-thoracentesis basilar pneumothorax. BMJ Case Rep. 2020 Sep 7;13(9):e238292. doi: 10.1136/bcr-2020-238292. PMID: 32900756; PMCID: PMC7478004.
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Dr. C Humphreys

Internal Medicine

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