The extended Mallampati score and a diagnosis of diabetes mellitus are predictors of difficult laryngoscopy in the morbidly obese.

Background: The modified Mallampati (MMP) classification is a standard method of oropharyngeal evaluation for predicting difficult laryngoscopy. Previous studies have demonstrated that the predictive value of the MMP is improved when the patient's craniocervical junction is extended rather than neutral (Extended Mallampati Score, EMS). In the present study, we compared the predictive value of the MMP and EMS in the morbidly obese.

Methods: We performed a prospective study of adult patients with a Body Mass Index (BMI) > or = 40 over a 12-mo period comparing the MMP and EMS. The performance of the MMP, EMS, and other commonly used tests was compared for the ability to predict difficult laryngoscopy, defined as a Cormack-Lehane grade of 3 or 4. Positioning and direct laryngoscopic techniques were not standardized. The incidence of difficult laryngoscopy and difficult intubation was compared in patients with BMI > or = or < 40.

Results: Three-hundred-forty-six patients with a BMI > or = 40 were evaluated with both the MMP and EMS and received direct laryngoscopy. On average, craniocervical extension decreased the MMP class (P < 0.0001). Compared to the MMP, the EMS improved specificity and predictive value while maintaining sensitivity. Compared to the MMP and other tests, an EMS class of 3 or 4 and a diagnosis of diabetes mellitus were the only statistically significant predictors of difficult laryngoscopy in the morbidly obese. There was no difference in the incidence of difficult laryngoscopy or intubation in the morbidly obese compared to patients with a BMI < 40.

Conclusions: The EMS was superior to the MMP in the prediction of difficult laryngoscopy in the morbidly obese population. A diagnosis of diabetes mellitus also warrants further investigation as a predictor of difficult laryngoscopy in this population. Finally, this study supports previous findings that morbid obesity is not itself a predictor of difficult laryngoscopy or intubation.