Anterior neck soft tissue thickness for airway evaluation measured by MRI in patients with cervical spondylosis: prospective cohort study

OBJECTIVES: Anterior neck soft tissue thickness, usually measured by ultrasound, is increasingly being investigated to predict difficult laryngoscopy, but the results have not been validated. Considering the conflicting measurement data, different measuring body positions and lack of a standard ultrasound procedure, we used MRI to verify the efficacy of these popular ultrasonographic parameters. DESIGN: Prospective cohort study. SETTING: A tertiary hospital in Beijing, China. METHODS: We enrolled 315 adult patients who underwent cervical spinal surgery in Peking University Third Hospital from April to October 2016. We analysed MRI data to predict difficult laryngoscopy. Cormack–Lehane scales were assessed during intubation, and patients with a class III or IV view were assigned to the difficult laryngoscopy group. RESULTS: Univariate analysis showed that male sex (p<0.01), older age (p=0.03) and body weight (p=0.02) were associated with difficult laryngoscopy. MRI data consisted of five common ultrasonographic variables used to predict difficult laryngoscopy, but none was a valuable predictor: skin to hyoid (p=0.18), skin to midpoint of epiglottis (p=0.72), skin to thyroid cartilage at the level of the vocal cords (p=0.10), skin to vocal cords (p=0.44) or skin to anterior to the trachea at the level of suprasternal notch (p=0.92). Adjusted by sex, age and body weight, none of the five MRI indicators had predictive value (p>0.05). CONCLUSION: The five most commonly studied ultrasonographic indicators of anterior soft tissue thickness appeared unreliable to predict difficult laryngoscopy in patients with cervical spondylosis. Further study is needed to validate the most valuable indicator to predict difficult laryngoscopy. TRIAL REGISTRATION NUMBER: ChiCTRROC-16008598; Pre-results.