Points of observation of closed chest drainage, including the following aspects. I. Observe carefully whether the mouth of the drainage tube in the drainage bottle is below the horizontal plane. Second, observe whether the drainage tube fluctuates with water column when the patient coughs. Third, observe the overflow rate of liquid and gas in the drainage tube, which should not be too fast. IV. Observe whether there is gas or liquid overflow around the chest drainage port. V. Squeeze the chest tube at regular intervals to keep the chest tube open and ensure smooth drainage of fluid and gas. Sixth, check the chest tube regularly to prevent the chest tube from breaking and prevent gas from entering the chest cavity abnormally.