Comparison of upper-lip bite test with other four predictors for predicting difficulty in intubation

Abstract

Background: Unanticipated difficult tracheal intubation remains a primary concern of anaesthesiologists. The aim of the present study was to compare upper-lip bite test (ULBT) with other four predictors namely modified Mallampati test (MMT), thyromental distance (TMD), sternomental distance (SMD) and interincisor distance (IID) for predicting difficulty in intubation. Methods: Airway assessment indices were evaluated and compared in 60 American Society of Anesthesiologists physical status Grade I and II patients undergoing general anaesthesia at a tertiary care teaching hospital in South India. The cut-off points for defining the difficult intubation (DI) were as follows: for ULBT, Class III; MMT, Classes 3 and 4; TMD <6 cm; SMD <11 cm and IID <3.5 cm. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for each of the predictive tests. Results: DI was observed in 26.7% of all patients studied. Sensitivity, specificity, PPV, NPV and accuracy for ULBT were 6.3%, 97.7%, 50%, 74.1% and 73.3%, respectively, whereas those for MMT were 25%, 86.4%, 40%, 76% and 70%, respectively. MMT showed 50% sensitivity and 84.5% specificity in assessing difficulty in intubation when compared with ULBT, whereas all the other methods have shown 0% sensitivity. MMT is a better predictor of difficulty in intubation when compared with ULBT due to its high sensitivity, better specificity, PPV and accuracy. Conclusions: No single airway predictor was accurate in predicting DI. A combination of at least two or more airway predictors has to be analysed to arrive at a near-ideal difficult airway prediction.

Keywords

• airway predictors
• difficult airway
• modified mallampati test
• upper-lip bite test