Predicting difficult laryngoscopy in acromegaly: a comparison of upper lip bite test with modified Mallampati classification

Abstract

Upper lip bite test (ULBT) is a simple test for predicting difficult intubation. However, it has not been evaluated in acromegalic patients. The primary aim of this study was to compare ULBT with modified Mallampati classification (MMPC) to predict difficult laryngoscopy in acromegalic patients. Over a 5-year period, 64 acromegalic and 63 nonacromegalic patients presenting for excision of pituitary tumor were enrolled. Preoperative airway assessment was done using MMPC and the ULBT. Under anesthesia, laryngoscopic view was assessed using Cormack-Lehane (CL) grading. MMPC III/IV and ULBT grade III were considered predictive of difficult laryngoscopy that was defined as Cormack-Lehane grades III or IV. Difficult intubation was defined as more than 2 direct laryngoscopy attempts involving change of blade or use of bougie/fiberoptic bronchoscope/intubating laryngeal mask airway. Sensitivity, specificity, positive and negative predictive values, and accuracy of both tests in predicting difficult laryngoscopy were calculated. Incidence of difficult laryngoscopy and intubation in acromegalics were 24% and 11%, respectively. MMPC and ULBT predicted difficulty in 61% and 14% acromegalics, respectively. However, only 26% and 44% of the laryngoscopies predicted to be difficult by MMMC and ULBT, respectively, were actually difficult. MMPC failed to predict 33% of difficult laryngoscopies whereas ULBT failed to predict 73%. Neither test predicted difficulty in 33% laryngoscopies that turned out to be difficult. Twenty-seven percent of the difficult laryngoscopies were correctly predicted by both tests. In acromegalic group, MMPC was more sensitive, whereas ULBT was more specific. Sensitivity and accuracy of both tests were less in acromegalic patients compared with nonacromegalic controls.