Cervical spine motion during tracheal intubation with King Vision™ video laryngoscopy and conventional laryngoscopy: a crossover randomized study

BACKGROUND: The King Vision T (KVL) videolaryngoscope with a wide field of view could potentially reduce cervical spine motion during intubation. We aimed to compare the extent of cervical spine movement during laryngoscopy using the KVL and Macintosh laryngoscopes. METHODS: Following ethical approval, 29 patients with a normal cervical spine requiring general anesthesia and tracheal intubation were randomly subjected to both KVL and Macintosh laryngoscopy in a crossover. Cervical spine motion during each laryngoscopy was radiologically examined by measuring changes in cumulative spine motion and changes from the neutral position in the C0-C5 angles formed by the adjacent vertebrae. Time to tracheal intubation, laryngoscopic view, and ease of intubation were also recorded. RESULTS : Compared with direct laryngoscopy, the KVL resulted in significantly less movement of the C-spine at the C0-C1, and C3-C4, C4-C5 segments (mean differences: C0-C1: 3.01 degrees [95% CI: -4.74 degrees to -1.28 degrees]; C3-C4: 1.81 degrees [95% CI: -3.19 degrees to -0.43 degrees]; C4-C5: -0.88 degrees [95% CI: -1.61 degrees to -0.19 degrees], P<0.02) and cumulative C-spine movement (mean 36.1 degrees [95% CI 32.72 to 39.51] vs. 44.1 degrees [95% CI: 39.54 to 48.75]; P=0.001). There was significant movement in the C0-C3 segment from baseline using both devices. Tracheal intubation took longer with KVL (mean difference: 12.7 s [95% CI: 9.15 to 16.13 s]; P=0.001) even though laryngeal visualization was improved (Cormack Lehane Grade I was reported in 100% KVL vs. 65.5% Macintosh laryngoscopies; P=0.001). CONCLUSIONS: In patients with normal cervical spine, KVL resulted in less extension of the cervical spine than direct laryngoscopy.