Retrospective analysis of vocal cord-to-suprasternal notch distance: Implications for preventing endotracheal tube cuff-induced vocal cord injury

Abstract

Endotracheal tube (ETT) positioning using the cuff ballottement test, which confirms that the inflated cuff is positioned at the suprasternal notch with squeezing or inflating a pilot balloon, has been reported to be a simple and reliable method of preventing endobronchial intubation. However, in patients with a short vocal cord-to-suprasternal notch, ETT placement using the cuff ballottement test can cause vocal cord injury. In the present study, we assessed the distance from a point 15 mm below the vocal cord to the suprasternal notch (VSD-15), the safe position for ETT cuff placement above the suprasternal notch, and investigated variables for predicting VSD-15.We retrospectively examined neck computed tomography in 427 adult patients and measured VSD-15 and the distance from the thyroid notch to the suprasternal notch (TSD). Patient height, weight, sex, and age were also recorded.In total, 47 patients (11.0%) showed a VSD-15 shorter than 45 mm. VSD-15 significantly correlated with TSD (r = 0.778, P < 0.001) and height (r = 0.312, P < 0.001), and inversely correlated with age (r = -0.321, P < 0.001). In multiple linear regression models, a formula was obtained for VSD-15 (VSD-15 [mm] = -6.220 + 0.744 × TSD [mm] + 0.092 × height [cm] - 0.065 × age [years], R = 0.621).The cuff ballottement test should be used cautiously in patients with a predicted short VSD-15. VSD-15 can be predicted from TSD, height, and age.

Figure 1

VSD-15 means the safe proximal margin for endotracheal tube cuff placement above the suprasternal notch. TSD is chosen as a predictive factor because the vocal cord exits on the posterior surface of the thyroid cartilage in adults and thyroid cartilage is easily detected externally. VSD-15 = the distance from 15 mm below the vocal cord to the suprasternal notch, TSD = the distance from the thyroid notch to the suprasternal notch.

Figure 2

Flow diagram of patient selection for image analysis. Of 778 patients who underwent neck CT, 255 patients were excluded because of diseases or masses that could affect the contour of the larynx, the upper trachea, and/or the suprasternal notch, and 96 patients were also excluded because of the ambiguous outlines in the CT images. Thus, the images of 427 patients were evaluated. CT = computed tomography.

Figure 3

Correlation between VSD-15 and variables. VSD-15 = the distance from 15 mm below the vocal cord to the suprasternal notch, TSD = the distance from the thyroid notch to the suprasternal notch.