A small amount of pleural effusion usually does not directly affect the lungs; if there is too much pleural effusion, it will squeeze the lung tissues, resulting in chest tightness, dyspnea and other corresponding symptoms. 1. Small amount of pleural effusion: when the pleural effusion is less than 0.5L, the symptoms are not obvious, at this time will not produce the phenomenon of extrusion of alveoli and lung tissues, there is usually no uncomfortable symptoms, and the impact on the lungs is usually not obvious. 2. Excessive effusion: when the large pleural effusion reaches a certain level, it will cause compression of the alveoli of the lung tissues and cause incomplete expansion of the lungs, which will result in a rapid heartbeat often accompanied by panic, dyspnea, chest tightness, coughing, chest pain and other symptoms. When there is a small amount of pleural effusion, it can be left untreated for the time being and reviewed regularly. When there is a large amount of pleural effusion with corresponding symptoms, it should be further examined in order to clarify the cause of the disease and be treated positively so as not to delay the condition.