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

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.

The Evaluation of Predictability of Difficult Intubation Using Upper Lip Bite Test / 대한마취과학회지

BACKGROUND: The unexpected difficult endotracheal intubation is a significant contributor to mortality and morbidity in clinical practice. Although there are many methods to predict difficult intubation, modified Mallampati test (mMT) and airway score were popular tests. The authors wanted to compare upper lip bite test (ULBT) with those two tests and also explored the possibility that ULBT could be a good sole predictor for difficult intubation. METHODS: 322 patients who were ASA I or II, aged > 16yr were enrolled in this study. Three residents visited patients to obtain airway measurements such as 1) ULBT, 2) mMT, 3) airway score (inter-incisor gap, mMT, thyromental distance, head & neck movement, history of difficult intubation, buck teeth). They were not involved in the intubation of patients they evaluated. The accuracy, specificity, positive and negative predictive values were calculated from the data of three tests, and three tests were compared with patient's laryngoscopic view grade according to Cormack & Lehane criteria by using Chi-square test. RESULTS: The incidence of Cormack & Lehane grade III, IV was 14.6% (not applied external laryngeal pressure). ULBT showed significantly higher specificity, positive predictive value than mMT, but sensitivity was lower than other tests. There were significant correlations between ULBT class III and Cormack & Lehane laryngoscopic grade III, IV (P< 0.001). CONCLUSIONS: ULBT is good for predicting difficult intubation as a simple, single test. But because of it's low sensitivity, it seems better to incorporate ULBT as a factor of airway score tests for more reliable prediction.

Endotracheal Intubation Using Laryngeal Mask Airway in a Patient with a Difficult Airway: A case report / 대한마취과학회지

Laryngeal mask airway (LMA) was designed as a new concept of airway management in anesthetic practice and has been successfully used in patients with difficult endotracheal intubation due to an abnormal upper airways. When It is in good position, one can cannulate the trachea either blindly or fiberoptic brochoscopically. In a patient with short neck and large breast, we were forced to use an emergency LMA because couldn't insert the laryngoscope. We decided to replace the LMA with an endotracheal tube to secure a definite airway. A fiberoptic bronchoscope was passed through both the endotracheal tube and the LMA to achieve endotracheal intubation. Then we attempted to remove the LMA for safe and smooth awakening. But the LMA coudln't be removed while keeping the LMA and the endotracheal tube in position. Therefore, surgery had to be proceeded with both the LMA and the endotracheal tube in place and all of which were removed after the surgical procedure. We conclude that the LMA is very useful as an aid of endotracheal intubation in patients with difficult airway.