Application of Flexible Bronchoscope with Different Outer Diameters in Orotracheal Intubation: An Observational Study

Background Flexible bronchoscope(FB) intubation is an important technique for anesthesiologists in airway management. Nonetheless, endotracheal tube(ETT) impingement against laryngeal structures during railroading frequently results in intubation failure. This study aimed to improve the success rate of FB intubation by increasing the outer diameter of the FB. Methods This prospective observational study included ASA I–II patients aged 18–60 years undergoing non-cervical surgery with FB intubation. Patients were stratified into three groups by FB outer diameter: 2.8, 3.8, and 4.8 mm. Exclusion criteria included difficult airway, airway anomalies, and refusal of FB intubation. The FB was advanced orally to carina visualization, followed by ETT railroading (maximum 4 attempts; 90° rotation for resistance). Primary outcomes included primary intubation success rate, intubation attempts, and intubation time. Secondary outcomes comprised postoperative sore throat and hoarseness. Results A total of 75 patients were included in the study.The primary intubation success rate were 28% (7/25), 48% (12/25), and 72% (18/25) in the 2.8, 3.8, and 4.8 mm groups, with a significant difference ( p  = 0.011) and significant difference between the 2.8 and 4.8 mm groups ( p  = 0.004). Median (IQR) total intubation time was 28 (23–35.5) s, 27 (21.5–34.5) s, and 21 (18–28)s in the 2.8, 3.8, and 4.8 mm groups. Overall difference p  = 0.018; significant between 2.8mm and 4.8mm groups ( p  = 0.013). Median (IQR) tube advancement time was 16 (11–41)s, 8 (6–15)s, 8 (6–9) s in the 2.8, 3.8, and 4.8 mm groups. Overall difference p  = 0.018; significant between 2.8mm and 4.8mm groups ( p  = 0.013). The number of intubation attempts differed significantly among groups ( p  = 0.041), with a significant difference only between the 2.8 mm and 4.8 mm groups ( p  = 0.006).No significant intergroup differences were noted in FB carina visualization time( p  = 0.272), operative duration( p  = 0.422), ETT dwell time( p  = 0.496), or the incidence of sore throat ( p  = 0.119)and hoarseness( p  = 0.125) in the post-anesthesia care unit. Conclusion A larger-diameter FB is preferable for intubation, as it improves first-pass success, reduces intubation attempts, and shortens procedure time. Trial registration Chinese Clinical Trial Registry.gov, ChiCTR2400091804, Retrospectively registered (date of registration November 4, 2024).