Stepwise versus one-step intubation strategy for tracheal injury in thoracic surgery: a multicenter randomized controlled trial protocol based on a combined visual lung isolation tube versus a video double-lumen tube

Tracheal injury remains a clinically relevant complication during lung isolation for thoracic surgery. Although video double-lumen tubes (VDLTs) improve visualization during intubation and bronchial positioning, visualization alone may not sufficiently reduce airway trauma if post-glottic rotational manipulation remains necessary. A combined visual lung isolation tube (combined tube) was developed to enable a predefined stepwise insertion strategy while maintaining an external diameter comparable to that of a double-lumen tube. This trial aims to compare a stepwise strategy based on the combined tube with a conventional one-step strategy based on a VDLT. This multicenter, prospective, randomized controlled trial will enroll 192 adult patients undergoing elective thoracic surgery requiring left-sided one-lung ventilation. Participants will be randomized 1:1 to either the combined-tube group or the VDLT group. The primary outcome is the incidence of moderate-to-severe tracheal injury, defined as moderate or severe mucosal injury at the subglottic region, tracheal shaft, carina, or bronchus. Secondary outcomes include site-specific tracheal injury, vocal cord injury, postoperative sore throat, hoarseness, intubation-related variables, lung isolation quality, hypoxemic events, airway pressure variables, and perioperative adverse events. Bronchoscopic recordings will undergo centralized blinded review by two independent assessors. The primary analysis will be conducted in the full analysis set using mixed-effects regression models to account for center effects. This trial will evaluate whether a predefined stepwise intubation strategy can reduce tracheal injury during lung isolation. By comparing two strategies represented by devices with comparable external diameters, the study may help distinguish the effect of insertion pathway from that of device size and provide mechanistic insight into the role of post-glottic rotational manipulation in airway injury. This study was registered with the Chinese Clinical Trial Registry (ChiCTR; Registration number: ChiCTR2600125149) on 21 May 2026. Details of the trial are publicly accessible at: https://www.chictr.org.cn/showproj.html?proj=321664 .