All patients undergo lateral thoracotomy or video-assisted thoracoscopic surgery (VATS) and are operated on by the same thoracic surgical team. All patients are managed with gravity drainage (water seal only, without suction) on the day of operation. Eligible patients are randomized to control group or clamping group at a 1:1 ratio before 3pm on the postoperative day. Patients in control group and those in clamping group are managed with different protocols after 3pm on the postoperative day.

All patients undergo lateral thoracotomy or video-assisted thoracoscopic surgery (VATS) and are operated on by the same thoracic surgical team. At the end of operation, the lung parenchyma is submerged in sterile saline to test for air leakage, and a single 24-Fr chest tube is placed in each patient. All patients are managed with gravity drainage (water seal only, without suction) on the day of operation.

Once a radiograph is confirmed re-expansion of the lung on the morning of the first postoperative day and no air leak is detected, the patient is a candidate for inclusion in the trial. Eligible patients are randomized to control group or clamping group before 3pm on the postoperative day.

Patients in control group are managed with gravity drainage unchangeably, while patients in clamping group are managed with clamping protocol after 3pm on the postoperative day as follow: the chest tube will be clamped, and the nurses will check the patient every 6 h. If the patient has no problems with compliance, the clamp will be removed for half an hour in the morning to record the drainage volume every 24 h. If patients develops intolerable abnormal symptoms, such as dyspnea, pneumothorax, and severe subcutaneous emphysema after chest tube clamping, the clamp will be removed for 30 min and be reapplied after the symptoms have been resolved. Such patients will be placed under more rigorous surveillance after re-clamping, which requires the medical staff to check on the patients every 2-4 hours in order to promptly detect abnormal symptoms. If abnormal symptoms occur frequently, this clamping protocol will be continued until another radiograph excluded the presence of pneumothorax.

The daily output of pleural fluid was recorded. The criteria for chest tube removal were as follows: (a) drainage volume≤250 mL in 24 h, (b) absence of air leakage and intrathoracic hemorrhage, and (c) absence of signs of purulent pleural effusion and atelectasis.

Inclusion Criteria:

Pathological diagnosis of lung cancer Treated with lobectomy and systematic mediastinal lymph node dissection/ systematic sampling Managed with gravity drainage (water seal only, without suction) Re-expansion of the lung confirmed on the morning of the first postoperative day

Exclusion Criteria:

Thoracic cavity infection Prolonged air leakage Reoperation due to chylothorax Atelectasis Liver cirrhosis Renal insufficiency Wound infection