Prediction of Difficulty in Endotracheal Intubation in Patients with Obstructive Sleep Apnea: Comparison of Modified Mallampati Test and Upper Lip Bite Test / 대한마취과학회지

ABSTRACT

BACKGROUND: Patients with obstructive sleep apnea (OSA) may exhibit difficult endotracheal intubation and mask ventilation because of anatomical abnormalities of their upper airway. Many anesthesiologists try to predict difficult endotracheal intubation using simple bedside screening tests. Among these tests, modified Mallampati test (MMT) is the most popular one, but a newer method, called upper lip bite test (ULBT) has been investigated. We compared the clinical accuracy of modified Mallampati test and upper lip bite test for patients with OSA. METHODS: 65 patients with OSA were included in the study. Preoperatively, anestheiologist not involved in endotracheal intubation evaluated patient's airway with MMT and ULBT. Another anesthesiologist assessed the direct laryngoscopic grade. Using Fisher's exact test, we analyzed the correlation of MMT and ULBT with direct laryngoscopic grade and calculated the sensitivity, specificity, positive predictive value and negative predictive value. Furthermore, AUC of ROC (area under a receiver operating characteristic) curve were used to estimate the predictive accuracy of each tests. RESULTS: MMT grade III, IV and ULBT class III was significantly correlated with Cormack-Lehane grade III, IV (P < 0.05). The ULBT showed higher specificity and positive predictive value, but sensitivity and negative predictive value were higher in MMT. AUC of ROC curve was poor for MMT (0.656) and ULBT (0.617). CONCLUSIONS: These results suggest that MMT and ULBT has a poor diagnostic accuracy for predicting difficult intubation in OSA patients as a single bedside screening test.