Risk factors assessment of the difficult intubation using intubation difficulty scale

Background: The major responsibility of anaesthesiologist is to maintain adequate gas exchange in his patients in all circumstances and this require that patency of upper airway is constantly maintained. Problems with upper airway management are among the most frequent causes of anaesthetic mishaps. Using intubation difficulty scale (IDS) we made an attempt to objectively assess the predictors of difficult intubation. We assessed classical bedside tests such as modified Mallampati test, Thyromental distance test and also neck extension test. Methods: We prospectively observed 400 patients undergoing general anaesthesia with endotracheal intubation, for each patient intubation difficulty score was recorded during intubation. Risk factors assessment of difficult intubation done using intubation difficulty scale. Risk factor assessed includes modified mallampati class III and IV, thyromental distance ≤ 6cm and neck extension < 5cm. Patients were categorised as Easy intubation (IDS, 0 to 2), slightly difficult intubation (IDS, 3 to 4) and difficult intubation (IDS 5). Preoperative airway assessment was done by thyromental distance measurement, neck extension measurement and modified mallampati test. Data was analysed using Receiver operating characteristic curve (ROC) and area under curve (AUC) for each test computed. p<0.05 was considered significant. Results: The incidence of difficult intubation was 8% and there were no failure to intubate the trachea. The AUC were as follows: modified Mallampati test 0.473 (p<0.005), Thyromental distance test 0.753 (p<0.005) and neck extension test 0.768 (p<0.005). Conclusion: The results indicate that neck extension test is strongest predictor of difficult intubation (IDS≥5) in comparison to Thyromental test and modified mallampati test.