Inter-observer agreement of tests used for prediction of difficult laryngoscopy/tracheal intubation

Guidelines recommend pre-operative airway evaluation for the prediction of airway management difficulties. Combining tests for evaluation increases the accuracy of the assessment. One model including seven parameters transformed into a simplified airway risk index (SARI) has been proven to be valid. We determined the inter-observer agreement of the specific test combinations included in SARI as well as of the total score.

Four observers assessed 136 patients, 120 without and 16 with a difficult airway history. Two residents and two specialists in anaesthesia performed the airway assessment consisting of the measurement of the mouth opening, the thyromental distance (TMD), the ability to protrude the mandible and an evaluation of the Mallampati class and head and neck mobility. Body weight was also recorded. Inter-observer agreement between specialists and residents, separately, was analysed using kappa statistics and Spearman's correlation analysis and the limits of agreement were evaluated using the 95% confidence interval. The agreement between pairs of assessors was also evaluated.

The inter-observer agreement was good to excellent for both specialists and residents when measuring mouth opening (Spearman's correlation coefficient R=0.88-0.97) and the horizontal distance between the upper and lower incisors during jaw protrusion (R=0.56-0.97). The Mallampati classification assessment demonstrated satisfactory to complete inter-observer agreement (kappa=0.41-1). The assessment of TMD and neck mobility showed considerable discrepancies between observers.

We demonstrated good inter-observer agreement using three tests from SARI and recommend the Mallampati classification, mouth opening and ability of jaw protrusion for pre-operative airway evaluation. A simplification of the assessment of TMD and neck mobility is warranted.