Anatomical location of the vocal cords in relation to cervical vertebrae, a new predictor of difficult laryngoscopy: A descriptive cross sectional study

Abstract

Airway management is among the challenges faced by the anaesthesiologists. There are anatomical and clinical factors, which can predict the difficult laryngoscopy. In this study, the aim was to predict the easy and difficult laryngoscopy preoperatively by assessing the anatomy of patient’s head and neck. The objective was to assess the same by using the magnetic resonance imaging films of the neck. The study included 110 adult patients with existing preoperative magnetic resonance imaging scans of neck. Preoperative anaesthetic assessment was done by using the thyromental distance, sternomental distance, body weight, mouth opening, Mallampati classification and head neck movement. The magnetic resonance imaging scans were screened for slices to visualise the vocal cords. A projection line was drawn to determinethe topography of vocal cords in relation to the cervical vertebrae. The ease of laryngoscopy by Cormack-Lehane grade was then correlated with the vertebral level of the vocal cords.The laryngoscopy was difficult in over weight patients (p<0.001) and with smaller thyromental distance. It was also observed that the laryngoscopy was easy (p<0.001), when the topographical location of vocal cords were related to C5 and hard, when they are at the level of C4 and C6 (p<0.001). Magnetic resonance imaging films of neck could be used to evaluate the potential difficult laryngoscopy, preoperatively. It can be used along with the existing bedside tests like determination of thyromental distance, sternomental distance and modified Mallampati classification.