A non-expandable lung (PNE) is a mechanical complication whereby the lung does not expand until it contacts the chest wall, which prevents a normal apposition between both pleural blades. The main mechanism involved is the restriction of the visceral pleura to form a fibrous layer throughout this pleural leaf. It occurs due to the presence of an active pleural disease (lung in the process of entrapment [PPA]), which can be resolved if appropriate therapeutic measures are taken, or remote (trapped lung [PA]), in which the Irreversible pleural fibrous layer. The clinical suspicion is given by the presence of a post-thoracocentesis hydropneumothorax or a pleural effusion that can not be drained by the onset of chest pain. Its diagnosis is based on the analysis of the pleural fluid, in the determination of the pleural pressures as we drain the effusion, and on chest CT with air contrast. Since both represent the continuity of the same process, the results will depend on the moment in which we carry out these procedures. If appropriate therapeutic measures are not taken promptly in the PPA, the final result will be a PA. In this, most patients are asymptomatic or have a small dyspnea of exertion, so they usually do not require treatment but, in cases of incapacitating dyspnea, it may be necessary to perform a pleural decortication to achieve resolution of symptoms.