Physiology of pleural space after pulmonary resection

The pleura is a serous membrane which includes the lungs and the adjoining structures. In the treatment of several lung diseases, a radical or partial lung resection may occur. Though thoracic surgery can solve or improve the symptoms, it alters the lung and the pleural physiological mechanisms, the fluid setting and the water balance. Post-operative residual pleural space depends on both the pre-surgery pulmonary compliance and the pleural lymphatic vessels absorption pressure. The disease that required surgery may play a significant role in the formation of the residual space. In a fibrotic lung, after pulmonary resection, pleural pressure becomes more sub-atmospheric overcoming the lymphatic draining activity; this leads to an enhanced hydrothorax risk. In addition, fibrosis may narrow parenchymal re-expansion due to fibrotic scars and residual granulomas. On the contrary, the emphysematous lung reduces the elastic recoil and increases pleural pressure implying a higher risk of air leak. Patients undergoing surgery to treat lung cancers present a residual air space less often than the afore mentioned diseases. Finally, the type of resection can influence the mechanism of persistent air spaces. The air leak tends to be more important and persistent after operations more complex and invasive. Thus, the resulting volume is the consequence of the new equilibrium between filtration and absorption of the pleural fluid and of the new mechanical coupling between the lung and the chest wall. Complications that may occur after surgery procedures are: persistent air leak (PAL), hydrothorax and lung oedema. An intensive early post-operative assessment may be useful to diagnose possible post-surgery initial complications. It may be also of crucial importance to know the elastic properties of the lung parenchyma, in order to set an appropriate pleural pressure which may prevent over distention and post-surgery complications.