Evaluation of Efficacy and Safety of Hyperangulated and Standard Curvature Blade Video Laryngoscopy Versus Direct Laryngoscopy for Double-Lumen Endobronchial Tube Intubation

Background and Rationale:

Double-lumen endobronchial tubes (DLTs) are the primary airway device for one-lung ventilation (OLV) in intrathoracic surgery. Their use enables lung isolation, which is essential for surgical exposure in procedures such as lobectomy, pneumonectomy, esophagectomy, and thoracoscopic interventions. Despite their widespread use, DLT placement is technically more demanding than standard single-lumen endotracheal intubation due to the tube's larger outer diameter, greater length, increased rigidity, and the presence of a distal bronchial cuff. These structural characteristics make laryngoscopy and tube advancement through the glottis considerably more challenging and are associated with a higher incidence of oropharyngeal, laryngeal, and tracheobronchial trauma compared to standard intubation.

Airway injuries related to DLT placement span a wide spectrum, ranging from minor mucosal lacerations of the lips, tongue, and pharynx to temporary or permanent vocal cord damage. In rare but serious cases, tracheobronchial perforation has been reported, a potentially life-threatening complication. The increased structural difficulty of DLT intubation translates into a higher likelihood of multiple intubation attempts, each of which independently increases the risk of airway trauma, hemodynamic instability due to prolonged laryngoscopy, and desaturation. Minimizing the number of attempts and the total intubation time is therefore of direct clinical importance in this patient population.

Videolaryngoscopy (VL) has become increasingly integrated into routine and difficult airway management over the past two decades. By providing an indirect, magnified view of the glottis transmitted via a camera mounted at the tip of the blade, VL improves glottic visualization compared to direct laryngoscopy (DL), particularly in patients with anticipated or unanticipated difficult airways. Multiple meta-analyses and randomized controlled trials have demonstrated the superiority of VL over DL in terms of first-attempt success rate, Cormack-Lehane grade, and rate of esophageal intubation in both routine and difficult airway scenarios.

The Storz C-MAC system is one of the most widely studied videolaryngoscopes and is available in two blade configurations relevant to this study: the Macintosh-geometry blade (C-MAC M-blade), which allows both direct and indirect laryngoscopy and preserves familiar hand mechanics, and the hyperangulated D-blade (C-MAC D-blade), which provides a more acute viewing angle and is specifically designed for cases where standard geometry blades fail to achieve adequate glottic exposure. Both blades transmit a high-resolution image to an external monitor, and the C-MAC system has been shown to improve first-attempt success rates and glottic visualization in a range of clinical settings.