Patient Collection
Of the 593 patients who underwent RATS pulmonary resection between January 2020 and March 2022 at the Second Hospital Affiliated to Harbin Medical University, Harbin, China, we retrospectively collected data from 155 patients who underwent RATS segmentectomy in this study. The Ethics Committee of the Second Hospital Affiliated to Harbin Medical University approved this retrospective study (IRB-2019-188) and waived the need for individual informed consent. Research have been performed in accordance with the Declaration of Helsinki.
The indications for RATS segmentectomy in patients with lung cancer were as follows: 1. a peripheral nodule 2 cm or smaller in diameter with 50% or more ground-glass appearance on computed tomography (CT); and 2. poor cardiopulmonary function or other major comorbidities that contraindicate lobectomy.
Complete resection was defined as the resection of all macroscopic tumour tissue and a resection margin that was free of tumour cells upon microscopic analysis. For lung cancer, the clinical stage was determined according to the tumour–node–metastasis criteria from the 8th edition of the Union for International Cancer Control Classification. Histologic evaluation was performed according to the 4th edition of the World Health Organization classification of lung tumours.
Operative Procedure
Simple segmentectomy was defined as upper division (left S1+2 and S3), lingular (left S4+5), dorsal (S6), or basilar segmentectomy. Complex segmentectomy was defined as individual, bisegmentectomy or subsegmentectomy other than simple segmentectomy.
Robot portal segmentectomy-3 (RPS-3) procedures were used in this cohort11. After intravenous induction, the patient was anaesthetized and intubated with a double lumen endotracheal tube. The three arms of a Xi Da Vinci robot (Intuitive, Sunnyvale, CA) were used for all patients. Three 8-mm ports were used for the robotic instruments, and one 12-mm port was used for the assistant port. The first 8-mm port was created in the eighth intercostal space (ICS) at the level of the anterior superior spine as the camera port. The camera was used to ensure entry into the pleural space through the camera port. Warmed humidified CO2 was then insufflated into the chest to drive the diaphragm inferiorly. The pressure of CO2 insufflation was set to 8–10 mmHg. The posterior 8-mm port was placed in the angulus inferior scapulae line at the same level as the camera port at a distance of 8-10 cm. The anterior 8-mm port was placed in the sixth or seventh ICS at the same level as the camera port at a distance of 8-10 cm. The assistant port, placed in the fifth or sixth ICS midclavicular line, was used for insertion of a 12-mm individual trocar and was enlarged after the operation to extract the specimen.
During the operation, the targeted segment bronchus, artery, and intersegmental vein were identified and dissected by ligation or a stapler device. Then, the collapsed lung was re-expanded completely with controlled airway pressure under 20 cm H2O using pure O2. Then, single-lung ventilation was resumed. The untargeted segments were compressed with a sponge stick. With compression, a distinct inflation-deflation line was formed. The demarcation of the ISP was classified into two grades: if the targeted segment collapsed or the adjacent subsegments were inflated, the ISP was regarded as having “poor” demarcation; if the boundary was clear or the targeted segment was inflated, the ISP was regarded as having “good” demarcation. The grades were evaluated by two surgeons (X.H. and Z.L.Y.) independently, and disagreements were resolved by consensus.
After MID, ICG was injected intravenously. ICG was reconstituted in distilled water to produce a 2.5 mg/mL solution, and a volume of 0.25 mg/kg was injected into the peripheral vein9,12. After the intravenous injection, the surgical field was visualized by near-infrared fluorescence imaging using a robot camera (Intuitive, Sunnyvale, CA). The target segment exhibited no fluorescence, while the injected ICG allowed the remainder of the lung to become fluorescent green. The pre-existing ISPs was revised according to the boundary separating the nonfluorescent and fluorescent pulmonary parenchyma. Under the guidance of the ISP as depicted by MID and ICG fluorescence, the intersegmental plane was divided using endoscopic staplers, and segmentectomy was completed (video1).
After segmentectomy, an air leakage test was performed by inflation of the lung under water. If an air leak was observed, it was managed with manual sutures. After that, the lung was inflated again under water to confirm that there were no other obvious air leaks. A 36-Fr chest tube was placed through the camera port.
Postoperative Care
The chest tube was removed when the amount of drainage was <200 mL and there was no air leakage. Postoperative complications were recorded according to the Clavien–Dindo classification for surgical complications13. Intraoperative complications included bronchial injury, incorrect vein division, arterial injury and conversion. Postoperative complications included pulmonary complications (e.g. bronchopleural fistula, prolonged air leakage (>5 days), pneumonia, pneumothorax, haemothorax, respiratory insufficiency, and empyema), cardiovascular complications (e.g. atrial tachycardia, atrial fibrillation, and myocardial infarction), and wound infection.
Statistical Analysis
The data are presented as the means, medians, or counts and percentages, as appropriate. The clinical and surgical variables were compared among groups: simple segmentectomy versus complex segmentectomy and MID versus MID combined with ICG.
The average values of variables were evaluated using Student’s t test or the Mann–Whitney U test, as appropriate. For the statistical analyses of the relationships between groups, Pearson’s test was used. All tests were 2-sided. All statistical analyses were performed using SPSS 24.0 software (IBM Corp, Armonk, NY).