Predictive value of combined Mallampati and Sternomental distance for difficult laryngoscopy: a prospective study

Abstract

Purpose: Difficult airway prediction remains a challenging task as none of the predictors reported so far has featured satisfactory accuracy. Much of this poor accuracy may be due to the inability of predictors to assess the diverse anatomic structures involved in difficult airway management. This led us to investigate whether the Mallampati test, a parameter that assesses the upper region of the airway, along with the sternomental distance, a parameter which evaluates the lower region of the airway, would improve the preoperative airway assessment when bound together. Methods: A prospective study with 453 patients scheduled for elective surgery under general anesthesia was performed. At transitional waiting hall before transport to the operating room, we collected data on sex, age, weight, height, ASA physical status, Body Mass Index, modified Mallampati test, and sternomental distance. In the operating room, after the induction of the anesthesia, the Cormack-Lahane classification was noted by the assistant anesthesiologist. Uni and multivariable analyses were conducted and three logistic regression models were obtained. Results: Mallampati classification (OR=7.17; p=0.000) and sternomental distance (SMD) (OR=11.08; p=0.000) were both associated with difficult laryngoscopy. The OR was 25.95 (p=0.000) when both Mallampati and SMD were indicative of difficult intubation. Three logistic regression models were evaluated (Figure 1) and their AUC defined as follows: Mallampati alone 72.88%; SMD alone 65.0%; Mallampati and SMD together 78.51%. Conclusions: Mallampati test and sternomental distance have better predictive performance when evaluated together. Additionally, the chances of facing a real difficult airway are highly increased when both are indicative of difficulty.