***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Management of the airway is central to the practice of anesthesia . Several bedside airway assessment methods have been proposed for preoperative identification of patients who are difficult to intubate . The modified Mallampati test ( MMT ) remains a time-tested technique to date for recognizing an anticipated difficult tracheal intubation as assessed by Cormack – Lehane grade . Both Mallampati and its further modification by Samsoon and Young evaluate patients in the seated position . Recently a study mentioned a change in MMT score from sitting to supine position toward the higher side . However , there is a lack of data regarding the relationship of positional change in MMT with Cormack – Lehane grade . The aim of this prospect i ve study was to assess if MMT score observed in sitting or supine position is a better predictor of difficult tracheal intubation .  One hundred and twenty-three patients of ASA physical status I and II , aged 18–60 years , who were scheduled to undergo various neurosurgical procedures were enrolled for the study . We found that the  MMT  in supine position has a higher positive predictive value and is associated with more true positives as compared to MMT in the sitting position Background : Preoperative using of anatomical l and marks detects potentially difficult laryngoscopies . The main object of the present study was to evaluate the predictive power of Extended Mallampati Score ( EMS ) in comparison with modified Mallampati test ( MMT ) , the ratio of height to thyromental distance ( RHTMD ) and the Upper-Lip-Bite test ( ULBT ) in isolation and combination . Material s and Methods : Four hundred seventy sixadult patients who c and i date for elective surgery under general anesthesia requiring endotracheal intubation  were included in this study and evaluated based of all four factors before surgery . This study was r and omized prospect i ve double - blind . After that , laryngoscopy was performed by an anesthesiologist who didn′t involve in preoperative airway assessment and grade d based on Cormack and Lehane′s classification . We calculated sensitivity , specificity , and area under receiver-operating characteristic ( ROC ) ( AUC ) for each score . Results : The AUCof the ROC was significantly more for the ULBT ( AUC = 0.820 , P = 0.049 ) and RHTMD score ( AUC = 0.845 , P = 0.033 ) than the EMS ( AUC = 0.703 ) . This variable was significantly higher for the EMS compared with MMT ( 0.703 vs. 0.569 , P = 0.046 respectively ) . There was no significant difference between the AUC of the ROC for the ULBT and the RHTMD score ( P = 0.685).The optimalcut-off point for the RHTMD for predicting difficult laryngoscopy was 29.3 . Conclusion : EMS predicted difficult laryngoscopy better than MMT while both ULBT and RHTMD had more power than EMS and MMT in this regard . ULBT and RHTMD had similar predictive value for prediction of difficult laryngoscopy in general population We explored the possibility that a simple and single test could replace the modified Mallampati score for either a difficult or an unaccomplished tracheal intubation in an impending hypoxic patient . Three hundred adult patients were enrolled in this study . They were subjected to the following assessment s : 1 ) oropharyngeal class according to the modified Mallampati criteria ; 2 ) the new , upper lip bite criteria —class I = lower incisors can bite the upper lip above the vermilion line , class II = lower incisors can bite the upper lip below the vermilion line , and class III = lower incisors can not bite the upper lip ; and 3 )  laryngeal view grading according to Cormack ’s criteria .  The incidence of difficult intubation was 5.7 % . The  upper lip bite test  showed significantly higher specificity and accuracy than the modified Mallampati test ( P < 0.001 ) . Comparisons of sensitivity , positive and negative predictive values , between the two tests , however , did not reveal any significant differences ( P > 0.05 ) . In conclusion , the upper lip bite test is an acceptable option for predicting difficult intubation as a simple , single test Purpose The ability to ventilate and oxygenate a patient using a bag-mask breathing system may be lifesaving in the case of failure of the initial intubation attempt . In this study , we aim ed to determine the incidence of  difficult mask ventilation ( DMV )  and to find preoperative risk factors for this procedure . Methods Based on methods used for overcoming some difficulties with bag-mask ventilation ( MV ) , classification has been made into four categories : easy MV , awkward MV , difficult MV , and impossible MV . A univariate analysis was performed to identify potential risk factors predicting DMV , followed by a stepwise forward binary logistic regression , and the odds ratio and 95 % confidence interval were calculated . Results A total of 576 patients were studied .  Incidence of easy MV , awkward MV , and difficult MV were found to be 75.5 % ( n = 435 ) , 16.7 % ( n = 96 ) , and 7.8 % ( n = 45 ) , respectively . Height , weight , age , male gender , increased Mallampati class , history of snoring , lack of teeth , and beard were found to be DMV risk factors ( P < 0.05 ) . Using a multivariate analysis , Mallampati class 4 , male , history of snoring , age , and weight were found to be significantly associated with DMV . Although the incidence of DMV in general was 7.8 % ( n = 45 ) , the incidence of DMV among patients with difficult intubation ( n = 123 ) was found to be 15.5 % ( n = 19 ) . Conclusions Mallampati class 4 , male patients , history of snoring , increasing age , and increasing weight were found to be risk factors for DMV in our study Using readily available and objective airway risk criteria , a multivariate model for stratifying risk of difficult endotracheal intubation was developed and its accuracy compared to currently applied clinical methods .We studied 10,507 consecutive patients who were prospect ively assessed prior to general anesthesia with respect to mouth opening , thyromental distance , oropharyngeal ( Mallampati ) classification , neck movement , ability to prognath , body weight , and history of difficult tracheal intubation . After induction of anesthesia , the laryngeal view during rigid laryngoscopy was grade d and the ability of experienced anesthesia personnel to ventilate via a mask was determined . Poor intubating conditions ( laryngoscopy Grade IV ) and inability to achieve adequate mask ventilation were identified in 107 ( 1 % ) and 8 ( 0.07 % ) cases , respectively . Logistic regression identified all seven criteria as independent predictors of difficulty with laryngoscopic visualization . A composite airway risk index ( derived from nominalized odds ratios calculated from the multivariate model ) as well a simplified ( 0 = low , 1 = medium , 2 = high ) risk weighting exhibited higher positive predictive value for laryngoscopy Grade IV at scores with similar sensitivity to Mallampati class III , as well as higher sensitivity at scores with similar positive predictive value . Compared to Mallampati class I fewer false-negative predictions were observed at a risk index value of 0 . We conclude that improved risk stratification for difficulty with visualization during rigid laryngoscopy ( Grade IV ) can be obtained by use of a simplified preoperative multivariate airway risk index , with better accuracy compared to oropharyngeal ( Mallampati ) classification at both low- and high-risk levels . ( Anesth Analg 1996;82:1197 - 204 BACKGROUND Oxygenation and ventilation by means of bag-mask and ambubag play a significant role in maintaining an optimal oxygen saturation of blood and hence the essence of life itself . Predicting difficulty in mask ventilation is again of paramount importance at the time of induction of anesthesia , and in emergency situations . In this study we aim ed at evaluating factors that could help in predicting the difficulty of bag-mask ventilation . METHODS In a prospect i ve study , 200 patients were allocated into two groups , 100 each . First group with a ULBT class I  , and the other group with ULBT class II and III . Factors such as height , weight , gender , past history of snoring , neck circumference , Mallampati class , sternomental and thyromental distances were then evaluated in each of the patients in the two groups in order to arrive at their impact on the incidence of difficult mask ventilation . Data were analyzed using Chi-square , student t-test and Fisher 's exact tests depending upon the situation . A p < 0.05 was considered to be statistically significant . RESULTS The results revealed that negative predictive value ( NPV ) of ULBT class , history of snoring and neck circumference were 86 % , 83 % , 81 % , respectively . A combination of these three predictors had an NPV of 95 % . CONCLUSION ULBT class alone was of value in predicting difficulty in mask ventilation , but a combination of the three tests significantly improved the predictive value OBJECTIVES To assess the difficulty in both  laryngoscopy and tracheal intubation related to goitre and to identify factors predictive of difficult intubation due to this condition . STUDY DESIGN Prospect i ve observational . METHODS We used the  Intubation Difficulty Scale ( IDS ) in 80 consecutive patients with large goitre ( defined by the inability to palpate the cricoid cartilage , the presence of endothoracic goitre , tracheal deviation of more than 1 cm or tracheal stenosis on the chest x-ray ) and 77 control patients . RESULTS Cormack grade s 3 - 4 were more frequent at initial laryngoscopy in patients with goitre ( 23/80 vs. 9/77 ; p<0.05 ) , but the difference was no longer significant after application of an external laryngeal pressure ( 8/80 vs. 5/77 ) . IDS scores ( median [ 25th-75th percentiles ] ) were higher in the goitre group ( 1 [ 0 - 4 ] ) than in the control group ( 0 [ 0 - 1 ] ; p=0.001 ) , corresponding to an increase in slightly difficult intubation ( IDS 1 - 5 : 36/80 vs. 15/77 ; p<0.05 ) . However , incidence of moderate to major difficulty in intubation ( IDS>5 : 8/80 vs. 7/77 ) as well as time to completion of intubation were similar in both groups . Tracheal stenosis ( > or = 30 % ) and reduced mouth opening ( < 4.4 cm ) were the only significant predictors of increased difficulty in intubation in patients with a goitre . CONCLUSION Large goitres are usually associated with slight difficulty in intubation only . Increased difficulty should be expected when severe tracheal stenosis is present on chest x-ray , especially when associated with a reduced mouth opening Background and objective Preoperative evaluation is important in the detection of patients at risk for difficult airway management . It is still unclear whether true prediction is possible and which variables should be chosen for evaluation . The aim of this prospect i ve , multi‐centre study was to investigate the incidence of difficult intubation , the sensitivity and positive predictive values of clinical screening tests and whether combining two or more of these tests will improve the prediction of difficult intubation in Turkish patients . Methods Seven study sites from six regions in Turkey participated in this study . One thous and six hundred and seventy‐four ASA physical status I‐III patients , scheduled to undergo elective surgery under general anaesthesia , were included . Results The incidence of difficult intubation was 4.8 % and increased with age ( P < 0.05 ) . The incidence of difficult intubation was significantly higher in patients who had a Mallampati III or IV score , a decreased average thyromental and sternomental distance , decreased mouth opening , or decreased protrusion of the m and ible ( P < 0.05 ) . Mouth opening and Mallampati III‐IV were found to be the most sensitive criteria when used alone ( 43 % and 35 % , respectively ) . Combination of tests did not improve these results . Conclusions There is still no individual test or a combination of tests that predict difficult intubations accurately . Tests with higher specificity despite low positive predictive value are needed OBJECTIVES The rate of difficult intubation  in prehospital emergency medicine varies greatly among studies already published and depends on several factors . The authors ' objective was to determine the rate of difficult intubations and to determine factors associated with prehospital difficult airways when a st and ard protocol for sedation and intubation was applied . METHODS This 30-month clinical , observational , prospect i ve study was performed in a suburb of Paris , France ( Val de Marne , population 1,300,000 ) by a prehospital emergency medical unit . Airway management for patients who needed tracheal intubation  was st and ardized . The pharmacological procedure recommended rapid sequence intubation for patients with spontaneous cardiac activity . In cases of difficult , laryngoscopy-assisted intubation , a predefined algorithm was proposed . The Intubation Difficulty Score ( IDS ) was calculated for all patients requiring tracheal intubation , and factors associated with difficult intubation , defined by IDS of > 5 , were identified by using multivariate statistical analysis . RESULTS During the study period , 1,442 patients were included ; 640 ( 44 % ) were in cardiorespiratory arrest , and 802 had a spontaneous cardiac activity . Deviation from the pharmacological and airway management procedures occurred in 1 % of cases . When the predefined difficult airway management algorithm was followed , failure to intubate was encountered twice ( 0.1 % ) . One hundred six ( 7.4 % ) patients had an IDS of > 5 , and 60 ( 4.1 % ) required first ( n = 5 
    Output:
    
Screening tests are expected to have high sensitivities .
We found that all investigated index tests had relatively low sensitivities with high variability .
In contrast , specificities were consistently and markedly higher than sensitivities across all tests .
Among the tests we examined , the upper lip bite test showed the most favourable diagnostic test accuracy properties .