Tehran University Medical Journal

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Background: Difficult intubation (DI), often unexpected, remains a primary concern for anesthesiologists. The purpose of this study was to compare the sensitivity and specificity of ULBT with sternomental, thyromental and interincisor distances in predicting difficult intubation.

Methods: In a prospective study, 380 patients undergoing general anesthesia were included. In all patients sternomental, thyromental and inter-incisor distances and the ULBT score were evaluated preoperatively. The Cormack grade was determined after the induction of anesthesia and grade 3 or 4 was considered as difficult intubation. The best points with highest accuracy were determined by ROC curve. Sensitivity and specificity of these tests in predicting difficult intubation were calculated and evaluated.

Results: In 19 (5%) patients, intubation was difficult. ULBT class III, inter-incisor distance less than 4.5 cm, thyromental distance less than 6.5 cm, sternomental distance less than 13 cm were considered as difficult intubation and there were significant differences between them and laryngeal view (P<0.05, McNemar) but there was no difference between laryngeal view in both sex. The sensitivity and specificity of ULBT is significantly higher than thyromental and sternomental and Inter-incisor distances (the specificity were respectively 91.96% vs. 64.77%, 70% and 82.27% and accuracy were respectively 91.05% vs. 76.58%, 71.32%, 81.84% and 59.53%)

Conclusion: We conclude that the specificity and accuracy of ULBT is significantly higher than inter-incisor, thyromental and sternomental distances and is more accurate in airway assessment.

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Background: Failed endotracheal intubation is one of the principal causes of morbidity and mortality in anesthetized patients. If the anesthetist can anticipate which patients may be more difficult to intubate, can reduce the risks of anesthesia greatly and be more prepared for any difficulties that may occur. The aim of this study was to investigate the inability of patients to protrude the lower jaw in predicting difficult intubation.
Methods: In this prospective study, we enrolled 300 patients, above 16 years of age or older, who were scheduled for elective surgery. For all of the patients, before each operation, a single anesthesiologist measured the temporomandibular mobility, which was defined as the difference between the distances, from the lower incisors to the upper incisors in a neutral position and at maximum mandibular protrusion. At the time of intubation, another anesthesiologist, blinded to the preoperative airway assessment test, performed a laryngoscopy in which the laryngoscopic view of the larynx was determined according to the Cormack and Lehane scoring system. Difficult intubation was defined as laryngoscopic views of grade III and IV.
Results: Twenty-one patients were identified as having difficult intubation. Only one patient could not be intubated. The forward movement of the mandible was significantly greater in patients with easy intubation compared to those with difficult intubation (6.42±1.95 mm vs. 3.58±1.26 mm respectively, P<0.001). The use of a cut-off point of less than 5 mm for prediction of difficult intubation showed a sensitivity of 92.86% and a specificity of 70.43%.
Conclusion: The forward movement of the mandible is significantly greater in patients with easy intubation compared those with difficult intubation Although infrequent difficulties may arise, most patients that do not have indicators of difficult intubation will be easy to intubate under anesthesia.