Examples are thoracocentesis to sample pleural fluid, and amniocentesis to sample amniotic fluid.

A thoracocentesis (pleural tap) is often performed here while a patient is in full expiration because of less risk of puncturing the lungs and thereby causing pneumothorax.

Reexpansion, i.e. post large volume thoracocentesis, resolution of pneumothorax, post decortication, removal of endobronchial obstruction, effectively a form of negative pressure pulmonary oedema.

Ultrasound must be used to confirm the presence of a pleural fluid collection and can be used to estimate the size of the effusion, differentiate between free and loculated pleural fluid and guide thoracocentesis if necessary.