Original ContributionDetermination of the diagnostic value of the Modified Mallampati Score, Upper Lip Bite Test and Facial Angle in predicting difficult intubation: A prospective descriptive study
Introduction
A no ventilate-no intubate scenario is one of the most dreadful situations that could be encountered by an anesthesiologist. Difficult intubation (DI) still remains as one of the anesthesia-related mortality and morbidity contributors. Although most intubations are easy, DI might be faced in 1.5–13% of the general anesthesia cases which could be associated with serious morbidities and mortality [1], [2], [3], [4], [5]. Numerous methods have been introduced to overcome DI; yet, no standard test has been proposed to evaluate and predict DI [3], [4], [5]. Nevertheless, some methods are routinely used by anesthesiologists as follows: Upper Lip Bite Test (ULBT), Modified Mallampati Score (MMS), Hyomental distance, Thyromental distance, Neck movement, Body mass index (BMI), Palm print, Head extension, Jaw protrusion, Wilson Score, and Lemon method [3], [6], [7].
Most researchers believe that no single test is able to predict DI and a combination of these tests rather than a single test should be used [8], [9]. Anatomical evaluation of the airway includes the visible (e.g. mouth, teeth, tongue and neck) and invisible (e.g. tongue base, larynx and epiglottis) parts. One of the contributing factors to DI is the Facial Angle (FA); its being less or more than the usual degrees would lead to backward or inward displacement of the jaw which in turn would cause DI. Consequently, to improve the quality of the airway evaluation, all above-mentioned factors ought to be considered simultaneously. In this study, we aimed to answer the question of whether measuring the FA would be optimum for the prediction of DI. Mallampati Score and ULBT were measured in all subjects.
Section snippets
Methods
After the approval of the study by the Ethics Committee of Tabriz University of Medical Sciences (date: 2012/6/5, President of Ethics Committee, Dr. Ostadrahimi, Protocol Number: 91107), 132 patients scheduled to undergo elective maxillofacial surgeries under general anesthesia were included in this study from 2012 June till 2013 July. Sample size was calculated based on the following formula: n = p(1 − p)z2/d2. (z = 1.96, p = 9% according to the previous studies with absolute error of 5%).
Results
Of the studied subjects, 16 people (12%) were considered as DI based on the Cormack and Lehane grading system. We managed this problem with inserting LMA or using fiberoptic bronchoscope or the method which was explained by Parish et al. [5] in their study. There is no significant statistical relationship between the demographic findings (age and BMI) and DI but the intubation time and Facial Angle were relevant to DI (Table 1). Sensitivity and specificity of a high Modified Mallampati Score
Discussion
The ability to evaluate and manage the airway has always been a major concern for physicians [2]. Based on the data obtained from our study, patients with an FA of < 82.5° will probably face DI with a sensitivity of 87.5% and patients with an FA of higher than 82.5° will probably face easy intubation with a specificity of 88.8%. ULBT with a sensitivity and specificity of 81.3% and 89.7%, respectively (PPV = 52, NPV = 97.2) and Mallampati with a sensitivity and specificity of 87.5% and 94.5%,
Conclusion
Considering the fact that using tests with low sensitivity for the prediction of DI could lead to missing some cases, it seems that we could use FA for the prediction of DI, thanks to its high sensitivity. Since our study is the first to introduce this test, it could be considered a novelty in the field of maxillofacial surgery airway management. Nevertheless, further studies with a larger sample size on heterogenous patients focusing on the predictive value of FA in the prediction of DI are
Competing interests
The author(s) declare that they have no competing interests.
Authors' contributions
Hassan Soleimanpour, Ata Mahmoodpoor and Samad EJ Golzar drafted the manuscript. Arezoo Nejabatian, Tannaz Pourlak, Masoumeh Amani, Saeed Hajmohammadi, Hamzeh Hosseinzadeh and Robab Mehdizadeh Esfanjani designed the study and performed statistical analysis. All of the authors were involved in patient management or the writing of the manuscript. All the authors read and approved the final manuscript.
Acknowledgments
The authors are grateful to all the health staff and patients who participated in the study, in addition to the staff of the Imam Reza Hospital. This article is based on a dataset forming part of Arezoo Nejabatian's specialty thesis, entitled “Determining of sensitivity of Facial angle, Modified Mallampati Score and Upper Lip Bite Test in prediction of difficult airway”. It is registered at Tabriz University of Medical Sciences (No: 92/3-3/2) and was presented in June 2015.
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