Anticipating difficult tracheal intubation by observing Modified Mallampati Grade, Thyromental Distance and Upper Lip Bite Test. A prospective observational study

Abstract

Diagnostic accuracy of various difficult airway predictors in anticipating difficult intubation have been studied in literature. To identify the best combination of bedside difficult airway tests in anticipating difficult intubation.In this study 200 patients between the ages18 -70 years, of American Society of Anaesthesiologists grade I II, posted for elective surgeries under general anaesthesia with intubation were enrolled. Modified Mallampati Grade, Thyromental Distance, Upper Lip Bite Test were noted on airway examination. Intubation difficulty during general anaesthesia was assessed by observing Cormack Lehane Grade, number of intubation attempts, use of external laryngeal pressure, Gum elastic bougie. Airway parameters of 200 patients were analysed in SPSS 20 software for sensitivity, specificity, positive predictive values, negative predictive values in individual tests and in various combinations with each other.: Among 200 patients, incidence of difficult intubation was 7% (14 patients). Patients needing two or more attempts for intubation, gum elastic bougie, external laryngeal pressure were five, eight and 30 respectively. Modified Mallampati Grade had sensitivity 64.3%, specificity 79%. Upper lip bite test had sensitivity 71.4%, specificity 41.9%. Combination of Modified Mallampati Grade with Upper Lip Bite Test had sensitivity 64.3%, specificity 84.9%, positive predictive value 80.9% which were statistically significant. Modified Mallampati Grade, Upper Lip Bite test individually and as combination have better diagnostic value, compared to other airway parameters, in predicting difficult intubation.