The aim of this study is to perform a prospective, single-center, randomized controlled study to explore whether closed insufflation technique is not inferior to dilatation and collapse technique in segmentectomy, and to provide a new option for establishing intersegmental plane in segmentectomy.

This is a single-center, prospective, randomized controlled study. A total of 200 subjects undergoing segmentectomy are scheduled to be enrolled within 1 year, and the subjects are randomly divided into closed insufflation group or dilatation and collapse group using a random number table generated by the computer, with 100 cases in each group. Intersegmental plane resolution grading, perioperative complications, operative time, intraoperative blood loss, postoperative hospitay stay, and pulmonary function 3 months and 1 year after surgery will be extracted and compared between the groups.

Inclusion Criteria:

1. Patients voluntarily join and sign a written informed consent;
2. The age of the subjects is 18-75 years old, regardless of gender;
3. The ECOG PS was 0 or 1;
4. Three-dimensional visualization was performed before surgery, and the surgeon judged that the tumor could be completely removed by segmentectomy, and surgical margin was expected to be greater than 2cm or the maximum diameter of the nodule;
5. Thin-slice CT suggests any of the following: ① The diameter of pulmonary nodules is 2-3cm and the consolidation-tumor ratio (CTR) is less than 0.25; ② Pulmonary nodule diameter ≤2cm and 0.25 < CTR < 0.5; ③ Non-peripheral pulmonary nodule diameter ≤2cm and CTR≤0.25;
6. cN0 and no distant metastasis;
7. Intraoperative freezing examination or postoperative paraffin examination suggest early lung adenocarcinoma;
8. Intraoperative freezing disease of station 12 lymph nodes showed no cancer metastasis;
9. Preoperative anesthesia risk assessment: American Society of Anesthesiologists (ASA) Level I-III;
10. Has no history of lung resection;
11. Has not received anti-tumor therapy such as radiotherapy, chemotherapy, targeted therapy and immunotherapy.

Exclusion Criteria:

1. The subject did not understand the study protocol, did not cooperate or refused to sign the informed consent;
2. The subject has a history of malignant tumor or has previously received anti-tumor therapy;
3. 3D visualization was not received before surgery;
4. The surgeon judged that segmentectomy could not ensure complete resection of the tumor;
5. has a history of lung resection, or chest trauma or surgery on the affected side of chest cavity;
6. Extensive intraoperative dense thoracic adhesion;
7. Conversion to thoracotomy;
8. Intraoperative frozen examination of intrapulmonary lymph nodes indicated cancer metastasis;
9. Pulmonary nodules are located in the right middle lung;
10. Suffered from chronic bronchitis, emphysema, asthma and other chronic lung diseases;
11. Other conditions unsuitable for inclusion in this study deemed by the researcher.