DETERMINATION OF THE DISTANCE BETWEEN THE LARYNGOSCOPE BLADE AND THE UPPER INCISORS DURING DIRECT LARYNGOSCOPY - COMPARISONS OF A CURVED, AN ANGULATED STRAIGHT, AND 2 STRAIGHT BLADES

We compared visibility and dental complications from a variety of blad es during tracheal intubation. Ninety-eight patients who received trac heal intubation were enrolled. They were divided into two groups: Stud y 1 (n = 50) and Study 2 (n = 48). Four laryngoscopic evaluations were planned for each patient using Miller and Wisconsin straight blades w ith different heel heights, a Macintosh curved blade, and a Belscope a ngulated straight blade (Study 1: Miller No. 3, Wisconsin No. 3, Macin tosh No. 4, and Belscope medium; and Study 2: Miller No. 2, Wisconsin No. 2, Macintosh No. 3, and Belscope medium, respectively). All laryng oscopies were performed by the same anesthesiologist. The distance bet ween the blade and the upper central incisors was measured when the op timum visibility of the glottis was obtained. The visibility was deter mined according to the Cormack and Lehane grading. Analysis of the dis tance between the blade and upper incisors was performed using the res ults of the 44 patients (166 distances) in Study 1 and the 48 patients (181 distances) in Study 2 who had a visibility of two or better. The Belscope blade provided a significantly greater visual field than the other types of blade. Two patients sustained a fracture of the centra l incisor and subluxation of the central incisor, respectively, during laryngoscopy in which a Wisconsin blade was used. The average inciden ce of dental injury was 1/191. The Belscope blade may contribute to a reduced likelihood of upper dental injuries during laryngoscopy.