This multicenter, prospective, randomized, controlled clinical trial is initiated by the First Affiliated Hospital of Zhejiang University School of Medicine, with participation from Peking Union Medical College Hospital, the Fourth Affiliated Hospital of Harbin Medical University, Harbin Medical University Cancer Hospital, and Shanxi Bethune Hospital. The study aims to compare the first-attempt placement success rate between visual bronchial blockers (VBB, test group) and conventional bronchial blockers (CBB, control group) during anesthesia for thoracic surgery, and to evaluate operational efficiency, lung isolation quality, and safety profiles.

A total of 652 patients aged ≥18 years with ASA physical status I-III, scheduled for elective pulmonary, esophageal, or mediastinal surgery requiring lung isolation, will be enrolled in a 1:1 ratio (326 per group), with a 10% anticipated dropout rate. Key exclusion criteria include anomalous right upper lobe bronchial origin, severe airway anatomical abnormalities, bronchial sleeve resection, empyema, bronchopleural fistula, previous thoracic surgery altering bronchial anatomy, severe cardiopulmonary dysfunction (metabolic equivalent <4), severe psychiatric disorders, and concurrent participation in other clinical trials.

Following standardized anesthesia induction with rocuronium (2-3 × ED95), patients undergo tracheal intubation using a video laryngoscope. In the CBB group, placement is guided by blind probing and auscultation, with confirmation via fiberoptic bronchoscopy (FOB). In the VBB group, placement is performed under direct vision using the integrated camera, with FOB rescue allowed only if visualization fails (rescue cases are counted as failures). Placement success is defined as the cuff located in the ipsilateral main bronchus with the proximal cuff edge immediately below the carina.

Primary endpoint: First-attempt placement success rate. Secondary endpoints: Time to successful first placement, lung collapse grade (Likert 3-point scale), cumulative number and duration of FOB use, intraoperative blocker displacement, hypoxemia (SpO₂ <90% or <85% for ≥5 seconds), airway injury, hemodynamic changes, postoperative sore throat, hoarseness, hospital length of stay, ICU admission rate, postoperative pulmonary complications, and 30-day all-cause mortality. Operator and surgeon satisfaction will be rated on a 0-10 scale.

Randomization is centralized, stratified by center, using variable block sizes (4, 6, or 8) to ensure allocation concealment. Outcome assessors and patients are blinded to group assignment, while operators are not. An independent Endpoint Adjudication Committee will review imaging data for blinded verification.

Statistical analysis will be performed using SPSS 27.0 and R software. Baseline characteristics will be compared using independent samples t-test, Mann-Whitney U test, chi-square test, or Fisher's exact test as appropriate. The primary endpoint (binary variable) will be analyzed using generalized linear mixed models (GLMM) with center as a random effect and logistic regression as a sensitivity analysis. A two-sided P<0.05 is considered statistically significant. Full Analysis Set (intention-to-treat), Per-Protocol Set, and Safety Set will be defined for efficacy and safety evaluations.

The trial timeline includes registration and training (June 2026 - August 2026), patient recruitment and data collection (September 2026 - September 2027), and data analysis, manuscript preparation, and publication (October 2027 - Dec 2028). Adverse events will be monitored, documented, and reported in accordance with CTCAE v5.0; serious adverse events will be reported to the ethics committee within 24 hours.

This study is the first randomized controlled trial evaluating a visual bronchial blocker worldwide. The investigators hypothesize that VBB improves first-attempt placement success, shortens positioning time, reduces FOB reliance, enhances lung collapse quality, decreases intraoperative displacement and hypoxemia, and lowers airway injury and postoperative complications. The results will provide high-level evidence for the clinical application of VBB in thoracic anesthesia and promote the visualization and standardization of one-lung ventilation techniques.

Inclusion Criteria:

• Age ≥ 18 years old
• ASA physical status I-III
• Scheduled for elective thoracic surgery (pulmonary, esophageal, or mediastinal procedures) requiring one-lung ventilation and lung isolation
• Able to understand and sign the informed consent form

Exclusion Criteria:

• Anatomical abnormalities of the tracheobronchial tree, including anomalous right upper lobe bronchial origin, severe airway stenosis, or distortion
• Planned bronchial sleeve resection or carinal surgery
• Empyema, bronchopleural fistula, or severe pleural adhesions affecting bronchial anatomy
• Previous thoracic surgery that altered bronchial anatomy
• Severe cardiopulmonary dysfunction with a metabolic equivalent (MET) < 4
• Severe psychiatric disorders or inability to cooperate with anesthesia procedures
• Current participation in another interventional clinical trial
• Contraindications to bronchial blocker placement (e.g., known allergy to materials used, high risk of airway trauma)