Comparison of four methods for predicting difficult intubation

Author(s): Javaher Foroosh Zadeh F, Safaii Sara

Abstract

Confirmation of endotracheal tube appointment is of critical importance, since unrecognized esophageal intubation can be rapidly lethal (death, brain damage). The aim of our study was to compare four different methods for prediction of difficult intubation: Mallampati, Thyro-mental distance, ULBT (Upper Lip Bite Test), and Inter incisicor gap. In a prospective study, 448 patients with a mean age of 53.5 who were scheduled for elective surgery were selected randomly and enrolled. Before induction of anesthesia, the airways were assessed by Mallampati test, Thyro mental distance, Upper lip bit test(ULBT) and Inter incisor gap. Laryngoscopic view according to the Cormack and Lehane grading system was determined after induction of anesthesia and Grades 3 and 4 defined as “difficult intubation.” Degree of observed difficulty of intubation was compared to predicted values. Sensitivity, specificity, positive and negative predictive values and accuracy of these tests and their combinations with the ULBT were calculated. Statistical analysis was performed using SPSS version 16. Data were analysis by using Fishers exact and McNemar's test, and a Pvalue. <0.05 was considered statistically significant. The prevalence of difficult intubation Cormack-Lehane in this study was 8.4%, Mallampati test had the highest sensitivity (47.3%) and Thyro-mental distance was most specific (96%). The ULBT (upper lip bite tests) had most positive and negative predictive value (37.9% & 93. 5%).Data also showed that power of these tests in predicting easy intubation is more than their ability in assessing the likelihood of difficult intubation. There was no significant difference regarding difficult intubation based on gender (P < 0.05), whereas there were significant differences between the older tests and laryngeal view (P < 0.05, Mc-Nemar test). Despite the validity of MMP, TMD, ULBT and IIG in predicting easy intubation is much greater than the value in prediction of difficult intubation; however, the simplicity of performing these tests and results of the four tests in evaluating patients before surgery by combination of tests in predicting difficult intubation will likely safe. It seems that best results are from applying combined test than a single one.

10.21746/ijbio.2016.01.005

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