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], R2 = 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.