***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 
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    ***EXAMPLES*** 
    Input: 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 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 Purpose We investigated the association between morbid obesity and difficult laryngoscopy ( DL ) .  Methods In a prospect i ve , controlled study we evaluated the impact of different variables on the prediction of DL in 200 morbidly obese ( study group-SG ) , and 1,272 non-obese ( control group-CG ) patients undergoing elective surgery .  Variables assessed included age , sex , body mass index ( BMI ) , protruding , loose , and missing upper teeth , thyro-mental distance , temporo-m and ibular joint ( TMJ ) function , neck extension , and Mallampati class . A Cormack grade III or IV was considered DL . Results The SG patients were younger ( P < 0.000 ) , there were more females in the SG ( P < 0.000 ) and more in the SG had teeth problems ( P = 0.026 ) . More patients in the SG ( 10%vs 1 % ) , had obstructive sleep apnea ( P < 0.001 ) with 90 % of them in the SG having a grade III laryngoscopy . High BMI did not affect the laryngoscopy difficulty ( P = 0.56 ) . Multivariable regression analysis revealed that morbid obesity , increased age , male sex , pathology of TMJ , and higher Mallampati class , were independent predictors of DL . When interaction between the predictors and the group was added to the multivariable model , the SG was no longer a predictor by itself , rather its association with abnormal upper teeth turned to be significant for prediction of DL . Conclusions Increased age , male sex , TMJ pathology , Mallampati 3 and 4 , a history of obstructive sleep apnea and abnormal upper teeth were associated with a higher incidence of DL . The magnitude of BMI had no influence on difficulty with laryngoscopy . RésuméObjectifNous avons examiné le lien entre l’obésité morbide et la laryngoscopie difficile (LD).MéthodeDans une étude prospect i ve et contrôlée , nous avons évalué l’impact de différentes variables sur la prédiction de LD chez 200 patients présentant une obésité morbide ( groupe expérimentai — GE ) et 1272 patients non obèses ( groupe témoin — GT ) devant subir une intervention chirurgicale réglée . Les variables évaluées ont été : l’âge , le sexe , l’indice de masse corporelle ( IMC ) , la protrusion , la mobilité et l’absence de dents supérieures , la distance thyromentonnière , la compétence de l’articulation temporo-m and ibulaire ( ATM ) , l’extension du cou et la classification de Mallampati . Une cote III ou IV de Cormack a été considérée comme une LD.RésultatsLes patients du GE étaient plus jeunes ( P < 0,000 ) , comprenaient plus de femmes ( P < 0.000 ) et présentaient plus de problèmes dentaires ( P = 0,026 ) . Un plus gr and nombre de patients du GE ( 10 % vs 1 % ) avaient une apnée du sommeil d’origine obstructive ( P < 0,001 ) do nt 90 % présentaient une laryngoscopie de classe III . Un IMC élevé n’a pas eu d’influence sur la laryngoscopie difficile ( P = 0,56 ) . Une analyse de régression multivariable a révélé que l’obésité morbide , l’âge avancé , le sexe mâle , une pathologie de l’ATM et une cote de Mallampati plus élevée ont été des prédicteurs indépendants de LD . Si on ajoute l’interaction entre les prédicteurs et le groupe au modèle multivariable , le GE n’est pius un prédicteur en lui-même , quoique son association avec une dentition supérieure anormale apparaisse significative pour prédire une LD . Conclusion Le vieillissement , le sexe masculin , une pathologie de l’ATM , une ciasse 3 ou 4 de Mallampati , des antécédents d’apnée du sommeil d’origine obstructive et des anomalies de la dentition supérieure ont été associés à une plus gr and e incidence de LD . Un IMC plus élevé n’a pas d’influence sur les difficultés laryngoscopiques OBJECTIVE Cardiac surgery patients might have a higher incidence of difficult laryngoscopy  than the general population because of older age , dental problems , and obesity . The authors estimated the incidence and predictors of difficult laryngoscopy in coronary artery bypass surgery patients . DESIGN Prospect i ve , controlled study . SETTING University setting . PARTICIPANTS Patients undergoing coronary artery bypass or general surgery . INTERVENTIONS Two hundred consecutive patients undergoing coronary artery bypass graft and 444 general surgery patients , all aged > 40 years , were compared for the incidence and predictors of difficult laryngoscopy , defined as a grade III or IV view . MEASUREMENTS AND MAIN RESULTS Predictors of difficult laryngoscopy were considered mouth opening < 4 cm , limited cervical mobility , thyromental distance < 6 cm , protruding or partially missing upper teeth , and Mallampati classes 3 and 4 . More cases of difficult laryngoscopy  were recorded in cardiac patients ( 10 % v 5.2 % , p < 0.023 ) . The cardiac patients were older , mostly men , and belonged to ASA III-IV risk classes . Mallampati classes 3 and 4 were more frequent in the control group . With univariate analysis , difficult laryngoscopy  correlated with 7 variables : older age , ASA-IV risk class , protruding or partially missing upper teeth , limited mouth opening , limited neck movement , thyromental distance < 6 cm , and diabetes mellitus . Multivariate analysis adjusted for propensity score identified older age ( odds ratio = 1.05/yr , 95 % confidence interval = 1.005 - 1.09 , p < 0.03 ) and limited neck movement ( odds ratio = 9.5 , 95 % confidence interval = 2.2 - 41 , p < 0.003 ) , but not cardiac surgery per se , as independent predictors of difficult laryngoscopy . CONCLUSIONS Difficult laryngoscopy  was more frequent in cardiac surgery patients ( 10 % v 5.2 % ) . Older age and limited neck movement , but not cardiac surgery per se , were independent predictors of difficult laryngoscopy The best view obtained by levering the tip of the McCoy laryngoscope blade with or without modified cricoid pressure was studied in 100 patients presenting for general surgery . The airway was assessed pre‐operatively ( Mallampati score , thyromental distance , mouth opening , protrusion of the jaw and weight ) in an attempt to identify the patients who might benefit from the use of the McCoy laryngoscope .  The vocal cords were visible at laryngoscopy with the blade in the neutral position in 32 cases . In the 68 remaining patients the vocal cords were partly visible in 48 . The epiglottis only was seen in 18 patients and in two not even the epiglottis could be visualised . Elevation of the blade or modified cricoid pressure improved the view in 38/68 cases and 57/68 cases , respectively ( p < 0.001 , Wilcoxon signed rank ) . Using our method of pre‐operative assessment we were unable to identify those patients who might benefit from either manipulation PURPOSE To determine inter-observer reliability of ten preoperative airway assessment tests used for predicting difficult tracheal intubation . METHOD We prospect ively assessed 59 patients undergoing elective surgery requiring tracheal intubation at a large metropolitan teaching hospital . Two experienced observers independently conducted the airway assessment tests on the same group of patients . Inter-observer reliability was examined using Kappa ( K ) and intraclass correlation coefficient ( ICC ) . RESULTS Two tests -- mouth opening ( ICC = 0.93 ) and chin protrusion ( ICC = 0.89)--had excellent inter-observer reliability . Seven tests -- thyromental distance ( ICC - 0.74 ) , subluxation ( K = 0.66 ) , atlanto-occipital extension distance ( ICC = 0.67 ) and angle ( K = 0.66 ) , profile classification ( K = 0.58 ) , ramus length ( ICC = 0.53 ) , oropharyngeal best view ( K = 0.49)--were moderately reliable . One test -- Mallampati technique of assessing oropharyngeal view ( K = 0.31)--had poor reliability . CONCLUSION Many of the preoperative airway tests have only moderate inter-observer reliability . This may provide some insight into why previous research has failed to show that the tests accurately predict difficult tracheal intubation Over the last decade , there has been a heightened awareness and an increase in the amount of literature being published on recognition and prediction of the difficult airway . During the preoperative evaluation of the airway , a thorough history and physical specifically related to the airway should be performed . Various measurements of anatomic features and noninvasive clinical tests can be performed to enhance this assessment . In this study we correlated the  Mallampati modified score  and several other indexes with the laryngoscopic view to identify anatomical and clinical risk factors related to the difficult airway . We prospect ively collected data on 1956 consecutive patients scheduled to receive general anesthesia requiring endotracheal intubation for elective surgery . The  Mallampati classification  versus the Cormack-Lehane ( C-L ) linear correlation index was 0.904 . A Mallampati Class 3 correlated with a C-L Grade 2 ( 0.94 ) , whereas a Mallampati Class 4 correlated with a C-L Grade 3 ( 0.85 ) and a C-L Grade 4 ( 0.80 ) . Operator evaluation , performed by a simplified tracheal intubation difficulty scale , showed a linear correlation of 0.96 compared with the C-L groups . Although there is a correlation between oropharyngeal volume and difficult intubation , the  Mallampati score by itself is insufficient for predicting difficult endotracheal intubation STUDY OBJECTIVES To study whether a detailed radiographic examination of neck and upper airway can help identify normal looking patients in whom endotracheal intubation may be difficult ; determine whether such parameters as identified by magnetic resonance imaging ( MRI ) can also be identified in a soft tissue radiograph ; and to study the correlation between oropharyngeal appearance , based on Mallampati 's classification , and laryngoscopic findings in a large number of patients requiring endotracheal intubation . DESIGN Prospect i ve . SETTING University medical center . PATIENTS 20 adult patients in 
    Output:
    
The Mallampati tests were poor at identifying difficult mask ventilation .
Used alone , the Mallampati tests have limited accuracy for predicting the difficult airway and thus are not useful screening tests