Fig. 6. ( A ) and ( B ): Bland and Altman plots for all 100 adults (○= men; •= women). The means of the differences between the two lengths were −0.81 cm (95% CI −1.10 ∼−0.52) with the formula of Cherng et al. ,13 and 0.00 cm (95% CI −0.16 ∼ 0.15) with our formula. The incisor-carina neutral length is the length from the upper incisor to the carina after intubation with a flexible fiberoptic bronchoscope through the endotracheal tube in neutral position. Cherng et al. ’s length = 0.1977 × height (cm) − 7.7423. Lee’s length = 0.868 × the incisor-MSJ extension length (cm) + 4.260. The incisor-MSJ extension length is the straight length from upper incisor to the manubriosternal joint (MSJ) in extended position.