Pleural effusion is a condition in which the amount of fluid in the pleural cavity is greater than the physiological level. A small increase in fluid may not cause mild difficulty breathing, but a large amount of effusion is life-threatening.

The consequences of pleural effusion affect the patient's respiratory function. Even if detected and treated promptly, pleural effusion can still leave sequelae. Especially for the elderly, the sequelae are even more severe.