Int J Clin Exp Med 2016;9(2):2184-2192 www.ijcem.com /ISSN:1940-5901/IJCEM0017279 Original Article Lateral neck radiography in prediction of difficult laryngoscopy in Chinese patients Guang-Yu Liu1, Yan-Yan Shen1, Yan-Hong Yan2, Meng-Nan Yao3, Ji-Xiu Xue1 1Department of Anesthesiology, Xuan Wu Hospital, Capital Medical University, Beijing, China; 2Department of An- esthesiology, Tongren Hospital, Capital Medical University Beijing, China; 3Department of Anesthesiology, Beijing Children’s Hospital, Capital Medical University, Beijing, China Received October 4, 2015; Accepted December 8, 2015; Epub February 15, 2016; Published February 29, 2016 Abstract: Several tests of radiology have been designed to predict difficult laryngoscopy, but there were few relative studies of Chinese patients. Our study is to investigate the accuracy of lateral neck radiography in predicting difficult laryngoscopy in Chinese patients. The operative database of Xuanwu Hospital, Capital Medical University, was re- viewed and all the patients who had performed lateral neck radiography before thyroid surgery from February 2014 to February 2015 were recruited. The results of Modified Mallampati test (MMT) and Thyromental distance (TMD) of the patients were obtained from the Database. Two trained reviewers independently measured α’ (the angle between hyoid cartilage, root of epiglottis and arytenoid cartilage) and several other angles and parameters on the X-ray. Receiver operating characteristic curves (ROC) were drawn and the areas under curves (AUC) were calculated to analyze the accuracy of each indicator. The cut off points were determined by maximizing the Youden index. In the study, 114 patients were included. The most accurate indicator of lateral neck radiography was α’, of which AUC was 0.896 (95% confidence interval [0.813, 0.979]). The cut off point of α’ was set as 85.52. The clinical test MMT (47% and 75%) has lower sensitivity and specificity than α’ (87% and 86%) and other indicators have lateral neck radiography. The diagnostic accuracy of lateral neck radiography in prediction of difficult laryngoscopy in Chinese patients may be superior to MMT and TMD. However, the method of lateral neck radiography is not perfectly precise. Keywords: Intubation, difficult laryngoscopy, prediction, radiography, sensitivity and specificity Introduction mental distance [9] have considerable false- positive and false-negative rates in prediction The management of difficult airway is one of of difficult laryngoscopy [10-12]. the most challenging tasks for anesthesiolo- gists. The incidence rate of difficult intubation The role of radiography in prediction of difficult in surgical patients under going general anes- intubation had been analyzed in some studies thesia is estimated to 1.5%-13%, approximate- [5, 13, 14]. Interestingly, the study of Kamalipour ly [1-4]. An unanticipated difficult endotracheal [13] showed that several angles in lateral neck intubation or failed endotracheal intubation is radiography can be used in the prediction of dif- frequently cited as a cause of anesthesia-relat- ficult tracheal intubation of Iranian patients, ed morbidity in otherwise healthy patients [5]. and the accuracy of his method was 100%. So it is crucial to predict difficult intubation before the induction of anesthesia and intu- On one hand, the weight [15] and Body Mass bation. Index [16] of patients, which may effect the inci- dence of difficult laryngoscopy, varies between Current bedside tests have limited and incon- Chinese and Iranian patients [17]. Without rela- sistent capacity to discriminate between pati- tive study or data of Chinese patients, the appli- ents with difficult and easy intubation [6]. It is cation of lateral neck radiography in prediction generally accepted that the clinical tests such of difficult laryngoscopy in Chinese patients as Modified Mallampati test [7, 8] and thyro- was limited. On another hand, it was suspected X-ray film in prediction of difficult intubation Exclude criteria are listed as following: 1) Patients had congenital cranial and maxillofa- cial deformities; 2) Patients had large tumor in the upper airway or adjacent areas: oral tumor, laryngeal cancer; 3) Thyroid neoplasms of pa- tients were more than 4 cm in length under ultrasound examination, or compressing the airway or inducing airway displacement; 4) Patients had oral and maxillofacial deformities which were generated by Trauma, infection or tumors; 5) Patients had small mouth deformi- ties or sternomental adhesions which were generated by burn scar adhesions; 6) Patients were with abnormalities anatomical structures near the airway which were generated by the surgery or radiotherapy; 7) Patients were with Figure 1. Lateral X-ray of the neck in a patient. E: tip mandibular joint ankylosis; 8) Patients were of epiglottis; E’: base of epiglottis; A: arytenoid; T: thy- with cervical spondylosis; 9) Patients were ed- oid cartilage; H: hyoid bone; O: the intersection of HA entulous or anisodont; 10) Patients were not and ET. intubated with Macintosh laryngoscopy; 11) Ra- diographs of patients could not be interpreted that lateral neck radiography could predict dif- (e.g. because of thyroid calcification or techni- ficult tracheal intubation so perfectly. Therefore, cal problems or vague). this study was designed and conducted. During the period from February 2014 to Fe- Material and methods bruary 2015, all eligible patients were included consecutively in the study. Study ethics The following data were collected from the da- This study was approved by the ethics commit- tabase. Demographic variables included age, tee of Xuanwu Hospital Capital Medical Uni- sex, height, weight, Body Mass Index (BMI), and versity (XWHCMU), and the written informed ASA physical status. Modified Mallampati test consent was waived by the ethics committee. (MMT): Samsoon and Young’s modification of the Mallampati test [8] recorded oropharyngeal Data collection structures visible upon maximal mouth open- The operative database of XWHCMU was re- ing. While seated, each patient was asked to viewed, and all the patients who had performed open his or her mouth maximally and to pro- lateral neck radiography before thyroid surgery trude the tongue without phonation. The view between February 2014 and February 2015 was classified as I: good visualization of the were recruited. soft palate, fauces, uvula and tonsillar pillars; II: pillars obscured by the base of the tongue Sample size was calculated using the method but the soft palate, fauces and uvula visible; III: of Arkin and Wathtel [18]. The confidence lev- soft palate and base of the uvula visible; and VI: el α was set as 0.05, and power was set as soft palate not visible. Thyromental distance 0.80. Sensitivity was estimated approximately (TMD): TMD was measured from the bony point as 0.8. The result of sample size of difficult of the mentum while the head was fully extend- laryngoscopy was calculated as 15. ed and the mouth closed. Difficult laryngoscopy was defined as laryngoscopy Grades III and IV Inclusion criteria are listed as following: Pa- according to Cormark and Lehane’s [19] gra- tients were more than 18 years old. They have ding. had elective thyoid surgery with endotracheal intubation in XWHCMU. Their lateral neck rad- Radiological measurements iological images were performed within one month before the operation. Their intubations Two anesthesiologists were trained by a radiol- were performed by anesthesiologists with more ogist before measurements. The two reviewers than three years experience. were blinded to other information of patients 2185 Int J Clin Exp Med 2016;9(2):2184-2192 X-ray film in prediction of difficult intubation Figure 2. Flowgram of the study. Difficult laryngoscopy de- fined as laryngoscopy Grades III and IV according to Cormark and Lehane’s grading. Easy laryngoscopy defined as laryn- goscopy Grades I and II accord- ing to Cormark and Lehane’s grading. Table 1. Demographic data of the patients of the epiglottis (E) and the midline of the hyoid Easy laryn- Difficult la- bone (H), which was referred to as HE. 3. The goscopy ryngoscopy distance between the highest point of the epi- Gender (male/female) 15/84 11/4 glottis (E) and the connection point of the true vocal cords at the posterior surface of the ary- Age 48±11 48±10 tenoid bone (A), which was referred to as AE. 4. Height (cm) 162±7 172±7 The true vocal cords, which was referred to as Weight (Kg) 66±11 80±12 TA. 5. Two angles, HOE (α) and HOT (β) which 2 Body mass Index (BMI, Kg/m ) 25±4 26±3 are formed by the connection of the two diam- ASA status (I/II/III) 13/83/3 3/12/0 eters in the square. We only measured the Difficult laryngoscopy defined as laryngoscopy Grades III and angle β. 6. The angle HTA (α’). 7. A line from IV according to Cormark and Lehane’s grading. Easy laryn- point H and parallel to TA was drawn (HE’) and goscopy defined as laryngoscopy Grades I and II according to Cormark and Lehane’s grading. the angle formed between HE and HE’ was called β’ (EHE’). 8. Difference between lines HT and AE, which was referred to as HT-AE. 9. and measured independently. The X-ray was Difference between lines HE and TA, which was analyzed with the following measurements referred to as HE-TA. according to the study of Kamalipour [13] in the Picture Archiving and Communication Systems Statistical methods of XWHCMU (Figure 1): Statistical analysis was performed by SPSS 1. The distance between the middle of the software (Version 17.0, SPSS Inc., Chicago, IL, hyoid bone (H) and the junction of the true vocal USA). It was considered statistically significant cords at the posterior surface of the thyroid (all 2-tailed) if P-value is less than 0.05. Av- bone (T) and this was referred to as distance erages of each X-ray indicators by the two re- HT. 2. The distance between the highest point viewers were calculated to be statistically ana- 2186 Int J Clin Exp Med 2016;9(2):2184-2192 X-ray film in prediction of difficult intubation Table 2.