Background: Several anatomical factors, such as prognathism, sex, short thyromental distance and others are known to make direct laryngoscopy difficult.
Objective: We investigated the hypothesis that the anatomical position of the vocal cords in relation to the cervical vertebrae correlates with difficult laryngoscopy. Existing MRI was used to identify the position of the vocal cords relative to the cervical spine in patients with and without difficult laryngoscopy.
Design: Observational study with adaptive enrichment.
Setting: University hospital.
Patients: A total of 142 adult patients, 91 with easy (Cormack-Lehane class 1 or 2) and 51 with difficult (Cormack-Lehane class 3 or 4) laryngoscopy.
Main outcome measures: Position of the vocal cords relative to cervical vertebrae in patients with easy vs. difficult laryngoscopy.
Results: In patients with difficult laryngoscopy, we found a higher incidence of cranial position of the vocal cords in relation to the cervical spine compared with patients with easy laryngoscopy (P < 0.001).
Conclusion: Anaesthesiologists should take advantage of existing imaging of the cervical spine when assessing the patient's airway.