Multivariate Analysis Of Predictive Factors For Difficult Laryngeal Exposure Under Suspension Laryngoscope

Endolaryngeal microscopic surgery using suspension laryngoscopies commonly performed in diagnosis and removal of lesions of the larynx or hypopharynx.An adequate laryngeal exposure may lead to exact diagnosis,removal of lesions completely,or avoid the complications during the surgery.To date,no anticipatory physical or radiologic indicators have been formally noted as reliable predictors of difficult laryngeal exposure (DLE).ObjectiveThis pilot study was designed to 1) evaluate a new laryngeal exposure score,which is suitable for suspension microlaryngoscopy surgery;2) identify useful and reliable indicators by which to predict,with acceptable accuracy,the occurrence of DLE following suspension laryngoscope;3) develop strategies for efficient microlaryngosurgery visualization of the glottis.MethodsDuring 1-year period,seventy-three patients,each of whom had undergone a suspension microlaryngoscopy surgery with complete documents.For purposes of this prospective study,we classified the patients into 2 groups:one is the DLE group(n=7),the other is the control group(n=66).We collected the infomation including age,gender.The measurements including body mass index(BMI),the neck circumference,the extent of neck extension,the size of full mouth opening,the Friedman grade(FTP),the angle of neutral-to-extension(NEA).We also measured some indices of distance while the patients' head both in neutral and extension position,and collected them both in physical examination and radiography examination,which encompassed the following six measures: the hyoid-mental distance(HMD),the thyroid-mental distance(TMD),the sternum-mental distance(SMD),hyoid-upper incisor distance(UIHD),the thyroid-upper incisor distance(UITD),the sternum-upper incisor distance(UISD).Besides,some special angles were mearsured in radiography examination,which included the thyroid-mandible angle(TMA),the thyroid-incisor angle(TIA).During suspension laryngoscopy,the new laryngeal exposure score were obtained for each patient and compared with the paramenters.Logistic regression was employed on patients' data to identify those with DLE.ROC curve was used to assess the predictive factors which had screened from logistic regression.ResultsThe study group consisted of 73 patients.In the DLE group,ages ranged from 34 to 57 years,with a mean of 46 years,including 2 female patients and 5 male patients.In the control group,ages ranged from 21 to 66 years,with a mean of 43 years,including 23 female patients and 43 male patients.Comparisons between difficult cases and control cases on each of all the potential predictors,significant differences were found in four predictors,namely TMD,which measured while the patients' head in extension position, and collected them both in physical examination and radiography examination;the angle of neutral-to-extension(NEA) and the Friedman grade(FTP).Among the four predictors,only TMD(in radiography examination with the patients' head in extension position) and the FTP were selected by stepwise logistic regression with a significant level of P＜0.05.The ROC curve indicated that the cuoff values were defined as follows:the TMD＜5.95cm,the FTP＞3 grade.Conclusions1.We evaluated a new laryngeal exposure classification according to the extent of vocal fold visualization during suspension laryngoscopy,which could help us to detected the predictive factors for difficult laryngeal exposure.2.Based on our comparison of case results,we found that anatomic challenges during difficult laryngoscopy included the TMD and the FTE 3.Combining these indices is an effective method for predicting difficult laryngeal exposure.4.Otherwise,the optimal head and neck position,the special type of laryngoscope and the external manual compression of the larynx will affect the laryngeal exposure score and the efficiency of predictiors of difficult laryngeal exposure.