Comparison of five bedside airway screening tests in predicting difficult intubation

Abstract

There is a need for at least sensitive test (so that majority of difficult cases can be identified) but also highly specific test (so that the false positive will be low in whom the test is used routinely). In the present study, an attempt is made to evaluate the value of the five bedside test namely modified mallampati test, sternomrental distance, thuromental distance interincisor gap and degree of head extension in predicting difficult intubation.The present cross-sectional study was carried out in general hospital at Mumbai for three months duration. One hundred patients undergoing elective surgery under general anesthesia requiring endotracheal intubation were studied with reference to preoperative airway evaluation using five bedside parameter to anticipate difficult intubation. Preoperative airway assessment included five bed side parameters namely modified mallampati test, sternomental distance, thyromental distance, intercisor gap and degree of head extension. After induction of general anaesthesia laryngoscopic view was graded as per Cormack and lehane classification. The incidence of difficult intubation in our study was 9%. Thyromental test had a sensitivity of 88.9%. Mallampati test had a sensitivity of 44.4% with the highest positive predictive accuracy of 66.7%. Sternomental distance has the lowest 
sensitivity 11.1%. Intercisor gap did not correlate well with laryngoscpic view. Degree of extension has sensitivity 66.7% better than mallampati test and sternomental distance. Thyromental distance of ≤6.5cms has the highest sensitivity and specificity and is the best predictor of difficult intubation. 
Sternomental distance had the lowest sensitivity and is not a 
reliable parameter for predicting difficult intubation. Mallampati 
test is modestly sensitive test to predict difficult intubation. Head 
extension has better specificity but is less sensitive than 
thyromental distance in predicting difficult intubation.