Fluid in the chest refers to pleural effusion, part of which is physiological manifestation. After excluding physiological factors, disease factors mainly include inflammation, tuberculosis, tumor and trauma. 1. Physiological factors Normal people have a small amount of pleural fluid in the chest cavity itself, play a lubricating role, in pregnancy or after strenuous exercise, may lead to a slight increase in the amount of fluid, but can be relieved with the circulation, belonging to the physiological changes. 2. Pathologic factors (1) Inflammation: mainly including pneumonia and pleurisy, after inflammation stimulation, it will lead to tissue exudation and cause pleural effusion. (2) Tuberculosis: tuberculosis is one of the most common causes of pleural effusion, which is closely related to pleural irritation and metamorphosis. (3) Tumor: Tumor causes pressure or invasion of adjacent tissues, which will lead to abnormal circulatory condition and also cause pleural effusion. (4) Trauma: Trauma directly leads to rupture of blood vessels and lymphatic vessels, causing pleural injury, which may lead to pleural effusion. If there is obvious pleural effusion accompanied by obvious respiratory limitation, it is necessary to consult a doctor in time and carry out standardized treatment under the guidance of a clinician.