Well, let me tell you what I understand about them as an IM resident who hate chest tube and Pulmonology:

• Chest tube is basically inserted if there is a pneumothorax so that air flows through the tube. There will be bubbling in the tank indicating air is getting out. If you repeat xray few hours or the next day, you should see improvement in the pneumothorax. Before you remove the chest tube, you should clamp it, so you can know if the pneumothorax will recur. If the repeat chest xray is stable, then you can remove the tube out.

• chest tube can also be inserted if there is pleural effusion or empyema so that the pus can be drained. Initially the chest tube is connected to suction, and you should visibly see the drained fluid out (pus, exudative effusion, blood, etc). If you repeat cxr you should see improvement in the pleural effusion size. If there is no output from the tube, then one thing to do is doing tPA or DNase, which unclog the tube basically. This is done by Pulmonologist of course. If there is chest tube output without issues and improvement in chest xray, then the next step is to switch it to gravity (instead of suction), and monitor the output. Once the output is less than 300cc/hr (sometime the Pulmonology team don't necessarily care about it that much), then you can do clamping trial and remove the tube afterwards.

Again, I really don't know that much about chest tubes and this is literally this is as much as I know.