Difficult Intubation: Prospective observational study to evaluate it’s key predictors

Introduction: Airway assessment to identify the predictors of difficult intubation (DI) during general anaesthesia is very important to maintain patient safety and prevent untoward events like hypoxia and brain damage. The aim of our study is to evaluate the occurrence of difficult tracheal intubation during general anaesthesia in elective surgeries and to find out the key predictors of difficult intubation. Materials and Method: A prospective study was conducted in 450 patients posted for elective general surgeries requiring general anaesthesia over a one year period. The screening tests for difficult intubation included the following: Mallampati classification (MPC), inter-incisor gap (IG), thyromental distance (TMD), subluxation of mandible (slux) and restricted neck movements (RNM). Risk factors assessed included obesity, neck circumference, short neck, buck teeth and poor dentition (loose / missing). Difficult intubation was defined when any one or more of these criteria were present: > 2 attempts at intubation; > 5-minutes duration of laryngoscopy; Cormack Lehane grade 3 or 4; use of intubating aids like McCoy laryngoscope and Frova (tracheal introducer). Multivariate analysis using a binary logistic regression was performed for the ten predictors. Predictive accuracy was assessed using sensitivity, specificity and positive predictive values. Result: Incidence of DI was 20.8%. It had strong correlation with MPC, RNM, TMD and poor dentition with an odds ratio of 9.2, 5.2, 4.8, and 2.58 respectively. TMD is most sensitive predictor (55.32%) and RNM is most specific predictor (97.2%). MPC, RNM, TMD are the key independent predictors of difficult intubation.