A study of radiologic imaging techniques and airway grading to predict a difficult endotracheal intubation.

Study Objectives: To study whether a detailed radiographic examination of neck and upper airway can help identify normal looking patients in whom endotracheal intubation may be difficult; determine whether such parameters as identified by magnetic resonance imaging (MRI) can also be identified in a soft tissue radiograph; and to study the correlation between oropharyngeal appearance, based on Mallampati's classification, and laryngoscopic findings in a large number of patients requiring endotracheal intubation.

Design: Prospective.

Setting: University medical center.

Patients: 20 adult patients in whom an unanticipated difficult endotracheal intubation was encountered, and a control group of 20 patients in whom endotracheal intubation was easily accomplished.

Interventions: Difficult-to-intubate patients were identified according to prospectively established criteria. Control subjects, in whom the trachea was easily intubated, were matched for age, gender, height, weight, and oropharyngeal appearance.

Measurements And Main Results: In all 40 study patients, a soft tissue radiograph and an MRI scan of the neck were obtained. We measured 21 parameters from both radiographic studies. There were no significant differences between the two groups in 20 of 21 measured parameters on MRI scans and soft tissue radiographs. Only one measurement--the distance between the uppermost visible part of the airway and the posterior pharyngeal wall (measured from MRI scans only)--between the two groups achieved statistical significance. The values recorded from MRI and soft tissue radiographs were not significantly different. Airway grading system first suggested by Mallampati had a fair correlation with laryngoscopy findings associated with a difficult endotracheal intubation.

Conclusions: No significant difference between the two groups could be identified on soft tissue radiography or MRI scans.