Mallampati Test Research Articles

Predictive Values of Preoperative Tests for Difficult Laryngoscopy and Intubation in Adult Patients at Tikur Anbessa Specialized Hospital.

Introduction The significance of difficult or failed tracheal intubation following induction is a well-recognized cause of morbidity and mortality in anesthetic practice. Nevertheless, the need to predict potentially difficult tracheal intubation has received a little attention. During routine anesthesia, the incidence of difficult tracheal intubation has been estimated at 1.5%–8% of general anesthetics. Difficulties in intubation have been associated with serious complications, such as brain damage or death, particularly when failed intubation has occurred. Occasionally, in a patient with a difficult airway, the anesthetist is faced with the situation where mask ventilation proves difficult or impossible. This is one of the most critical emergencies that may be faced in the practice of anesthesia. If the anesthetist can predict which patients are likely to prove difficult to intubate, he/she may reduce the risks of anesthesia considerably. In Ethiopia, there are no data on the magnitude of difficult laryngoscopic tracheal intubation and no standard guidelines for preoperative tests. The main concern of this study was to provide information on the magnitude of difficult laryngoscopic intubation and to determine valuable preoperative tests to predict difficult laryngoscopy and intubation in patients with apparently normal airways which can help anesthetists to improve preoperative airway assessment and contribute to decrease anesthesia-related morbidity and mortality. Objective The main objective of this study was to assess the magnitude and predictive values of preoperative tests for difficult laryngoscopy and intubation, among surgical patients who underwent elective surgery under general anesthesia with endotracheal intubation in Tikur Anbessa Hospital from February 1 to March 30, 2016. Study Design A facility-based cross-sectional study design was used. Result In this study, we found the magnitude of difficult laryngoscopy and intubation as 13.6% and 5%, respectively. 33.3% of patients with difficult laryngoscopy were found to be difficult for intubation. Mallampati test, interincisor distance, and thyromental distance were identified to be good preoperative tests to predict difficult laryngoscopic intubation when used in combination. Recommendation We recommend anesthesia professionals to use combination of MMC/TMD/IID for their routine preoperative airway assessment.

Comparision of airway assessment by Mallampati classification and cormack and lehane grading in Indian population

Introduction: This prospective cross-sectional observational study was undertaken to compare preanaesthetic predictive value of Modified Mallampati classification in relation to Cormac Lehane grades in Indian population. Materials and Methods: One hundred patients of either sex, who have underwent general anaesthesia were includes in the study. Inclusion criteria were aged between 18 to 60 years, ASA grades I and II, weighing between 45- 80 kg. The parameters observed were, Mallampati class (MMT) during pre anaesthetic assessment and their percentages, Cormack and Lehane grades (CL) at intubation and their percentages and correlation of Cormack and Lehane grading and Mallampati classification. Results: Out of 100 patients, men women ratio was 1: 2.1(32: 68), mean age of the patients were 43.15± 12.96yrs, mean BMI of the patients were 23.34 ± 1.34 kg/m?2;. The corrected chi square test showed a value of 76.8 with a P value of Conclusion: To increase predictive value of preassessment of difficult airway, Mallampati test should be supplemented by other airway assessment tools. Keywords: Mallampati test, Predictive value, Difficult intubation.

Bedside tests for predicting difficult airways: an abridged Cochrane diagnostic test accuracy systematic review.

Although bedside screening tests are routinely used to identify people at high risk of having a difficult airway, their clinical utility is unclear. We estimated the diagnostic accuracy of commonly used bedside examination tests for assessing the airway in adult patients without apparent anatomical abnormalities scheduled to undergo general anaesthesia. We searched for studies that reported our pre-specified bedside index screening tests against a reference standard, published in any language, from date of inception to 16 December 2016, in seven bibliographic databases. We included 133 studies (127 cohort type and 6 case-control) involving 844,206 participants. Overall, their methodological quality (according to QUADAS-2, a standard tool for assessing quality of diagnostic accuracy studies) was moderate to high. Our pre-specified tests were: the Mallampati test (6 studies); modified Mallampati test (105 studies); Wilson risk score (6 studies); thyromental distance (52 studies); sternomental distance (18 studies); mouth opening test (34 studies); and the upper lip bite test (30 studies). Difficult facemask ventilation, difficult laryngoscopy, difficult intubation and failed intubation were the reference standards in seven, 92, 50 and two studies, respectively. Across all reference standards, we found all index tests had relatively low sensitivities, with high variability, but specificities were consistently and markedly higher than sensitivities. For difficult laryngoscopy, the sensitivity and specificity (95%CI) of the upper lip bite test were 0.67 (0.45-0.83) and 0.92 (0.86-0.95), respectively; upper lip bite test sensitivity (95%CI) was significantly higher than that for the mouth opening test (0.22, 0.13-0.33; p<0.001). For difficult tracheal intubation, the modified Mallampati test had a significantly higher sensitivity (95%CI) at 0.51 (0.40-0.61) compared with mouth opening (0.27, 0.16-0.41; p<0.001) and thyromental distance (0.24, 0.12-0.43; p<0.001). Although the upper lip bite test showed the most favourable diagnostic test accuracy properties, none of the common bedside screening tests is well suited for detecting unanticipated difficult airways, as many of them are missed.

Acromioaxillosuprasternal Notch Index and Old Head and Anatomic Neck Criteria in Predicting Difficult Laryngoscopy in Tracheal Intubation in Children under General Anesthesia

Introduction: Currently, various methods are being used for determining difficult laryngoscopy. The present study aimed to compare the acromioaxillosuprasternal notch index function with the old head and neck anatomic criteria in predicting difficult laryngoscopy with respect to trachea intubation under general anesthesia in children. Materials and Methods: In this cross-sectional study, 379 children under intubation with general anesthesia entered the study. Patients were divided into two groups: easy laryngoscopy (grades 1 and 2) and difficult laryngoscopy (grades 3 and 4) based on Cormack-Lehane score. The thyromental distance systems, height to thyromental distance, Upper-Lip-Bite test, neck circumference, and acromioaxillosuprasternal notch index were studied and compared. Results: Laryngoscopy was difficult in 48 subjects (38 were grade 3 and 10 were grade 4). Interestingly, no significant difference was detected between easy and difficult laryngoscopies based on the thyromental distance, neck circumference, height to thyromental distance, and acromioaxillosuprasternal notch index (P&gt;0.05). height to thyromental distance , acromioaxillosuprasternal notch index , and neck circumference have a sensitivity of 32.2%, 47.9%, 51.1%, respectively, and the specificity was 52.7%, 45.6%, and 48.9%, respectively. Conclusion: Neck circumference and acromioaxillosuprasternal notch index outperform the height to thyromental distance. On the other hand, Modified Mallampati test is better than Upper-Lip-Bite test in determining difficult laryngoscopy in children.

Reliability of the thyromental height test for prediction of difficult visualisation of the larynx: A prospective external validation.

Background and Aims:Thyromental height (TMH) has been reported to be useful for prediction of difficult visualisation of the larynx (DVL), defined as Cormack--Lehane (C&L) grade III or IV. The aim of this study was to compare the diagnostic accuracy of the TMH test for DVL with that of other clinically used tests in Japanese patients.Methods:Six hundred and nine surgical patients undergoing endotracheal intubation under general anaesthesia were enrolled in this prospective observational study. TMH, thyromental distance (TMD), and Samsoon and Young's modified Mallampati (MMT) tests were performed in all patients. The C&L grades for the laryngoscopic view with and without external backward, upward, rightward pressure (BURP) were determined by designated airway assessors. The cutoff value for the TMH test was calculated using receiver-operating characteristic (ROC) curve analysis. The sensitivity, specificity, positive predictive value, accuracy, positive likelihood ratio, and area under the ROC curve (AUROC) for each predictive test were calculated and compared.Results:ROC curve analysis indicated that 54 mm is the optimal cutoff value for the TMH test. However, both this value and the conventional cutoff value of 50 mm, which has been reported as having good diagnostic accuracy in the literature, had poor diagnostic accuracy. The AUROC for the TMH test was 0.631 without BURP and 0.592 with BURP; these values were not superior to those for the TMD test or MMT.Conclusion:The TMH test is not a good predictor of DVL in Japanese patients.

Comparison of upper-lip bite test with other four predictors for predicting difficulty in intubation

Background: Unanticipated difficult tracheal intubation remains a primary concern of anaesthesiologists. The aim of the present study was to compare upper-lip bite test (ULBT) with other four predictors namely modified Mallampati test (MMT), thyromental distance (TMD), sternomental distance (SMD) and interincisor distance (IID) for predicting difficulty in intubation. Methods: Airway assessment indices were evaluated and compared in 60 American Society of Anesthesiologists physical status Grade I and II patients undergoing general anaesthesia at a tertiary care teaching hospital in South India. The cut-off points for defining the difficult intubation (DI) were as follows: for ULBT, Class III; MMT, Classes 3 and 4; TMD Results: DI was observed in 26.7% of all patients studied. Sensitivity, specificity, PPV, NPV and accuracy for ULBT were 6.3%, 97.7%, 50%, 74.1% and 73.3%, respectively, whereas those for MMT were 25%, 86.4%, 40%, 76% and 70%, respectively. MMT showed 50% sensitivity and 84.5% specificity in assessing difficulty in intubation when compared with ULBT, whereas all the other methods have shown 0% sensitivity. MMT is a better predictor of difficulty in intubation when compared with ULBT due to its high sensitivity, better specificity, PPV and accuracy. Conclusions: No single airway predictor was accurate in predicting DI. A combination of at least two or more airway predictors has to be analysed to arrive at a near-ideal difficult airway prediction.

Comparison of thyromental height test with ratio of height to thyromental distance, thyromental distance, and modified Mallampati test in predicting difficult laryngoscopy: A prospective study.

Background and Aims:Preoperative airway assessment to predict patients with difficult laryngoscopy is always crucial for anesthesiologists. Several predictive tests have been studied by various authors in quest of finding the best airway predictor. Recently, a new airway predictor, thyromental height test (TMHT) has been reported to have good predictive value in assessing difficult airway. We conducted this study with primary aim to evaluate the diagnostic accuracy of TMHT and to compare it with other established airway predictors, such as ratio of height to thyromental distance (RHTMD), thyromental distance (TMD), and modified Mallampati test (MMT) for predicting difficult laryngoscopy.Material and Methods:This prospective, observational study was conducted in 550 patients of either sex aged >18 years scheduled for elective surgery under general anesthesia. The patients’ airway was assessed preoperatively by two anesthetists. Standard anesthetic protocol was followed in all the patients. The laryngoscopic view was graded according to Cormack–Lehane scale. The receiver operating characteristic (ROC) curve was used to calculate the ideal cut off values for TMHT and RHTMD. Standard formulae were used to calculate validity indexes.Results:The incidence of difficult laryngoscopy was 10%. The cut-off value for TMHT and RHTMD were 5.1 cm and 19.5, respectively. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of TMHT were 78.18%, 93.94%, 58.90%, and 97.48%, respectively. The highest sensitivity, PPV, and NPV were observed with TMHT as compared with RHTMD, TMD, and MMT (P < 0.0001).Conclusions:TMHT is the best predictive test with highest accuracy and odds ratio for predicting difficult airway out of all predictive tests evaluated.

Predictive performance of a multivariable difficult intubation model for obese patients.

BackgroundA predictive model of scores of difficult intubation (DI) may help physicians screen for airway difficulty to reduce morbidity and mortality in obese patients. The present study aimed to set up and evaluate the predictive performance of a newly developed, practical, multivariate DI model for obese patients.MethodsA prospective multi-center study was undertaken on adults with a body mass index (BMI) of 30 kg/m2 or more who were undergoing conventional endotracheal intubation. The BMI and 10 preoperative airway tests (namely, malformation of the teeth in the upper jaw, the modified Mallampati test [MMT], the upper lip bite test, neck mobility testing, the neck circumference [NC], the length of the neck, the interincisor gap, the hyomental distance, the thyromental distance [TM] and the sternomental distance) were examined. A DI was defined as one with an intubation difficulty scale (IDS) score ≥ 5.ResultsThe 1,015 patients recruited for the study had a mean BMI of 34.2 (standard deviation: 4.3 kg/m2). The proportions for easy intubation, slight DI and DI were 81%, 15.8% and 3.2%, respectively. Drawing on the results of a multivariate analysis, clinically meaningful variables related to obesity (namely, BMI, MMT, and the ratio of NC to TM) were used to build a predictive model for DI. Nevertheless, the best model only had a fair predictive performance. The area under the receiver operating characteristic curve (AUC) was 0.71 (95% confidence interval 0.68–0.84).ConclusionsThe predictive performance of the selected model showed limited benefit for preoperative screening to predict DI among obese patients.

Predictors of difficult airway in a Chinese surgical population: the gender effect.

Compared with men, women often have a shorter interincisor distance and a shorter thyromental distance but are less likely to have difficult airway. The hypothesis is that the prediction criteria of difficult airway differ between men and women. The aim of this study was to investigate differences in the prediction criteria of anatomic predictors for difficult airways in men and women. We enrolled adult patients who underwent general anesthesia and tracheal intubation. The interincisor distance, thyromental distance, modified Mallampati test results, upper lip bite test results, and tongue thickness of each patient were evaluated prior to the initiation of anesthesia. The primary outcome was difficult tracheal intubation. Receiver operating characteristic (ROC) curve analysis and Youden's index were used to determine the criteria for predictors in men and women. In total, 1059 men and 1195 women were examined. Compared with women, men had a higher incidence of difficult tracheal intubation (P<0.001). The cut-off values for predicting difficult tracheal intubation of the interincisor distance, thyromental distance, modified Mallampati test results, upper lip bite test results, and tongue thickness determined by Youden's index were ≤38 mm, ≤70 mm, >3, >2, and >62 mm, respectively, for men, and ≤33 mm, ≤65 mm, >2, >1, and >60 mm, respectively, for women. The optimal cut-off values of predictors of difficult airway differ between males and females.

Prediction of Difficult Airway by Correlating Physical Indices with Maxillo-Pharyngeal Angle, Measured on Lateral Cervical Radiograph-an Analytical Study

Background: The ability to predict difficult laryngoscopy preoperatively allows anaesthesiologists to take precautions to reduce the anesthesia-related risks but till now, no single airway test can provide a high index of sensitivity and specificity for prediction of difficult airway. The present analytical study was aimed to correlate the various physical indices with maxillo-pharyngeal angle, measured on lateral cervical radiograph, for preoperative prediction of difficult airway. &nbsp;Subjects and Methods: After approval from Institutional Ethical Committee and written informed consent, 200 patients of ASA physical status I and II, aged between 18 to 58 years of either gender with BMI &lt;25 Kg/m2, were studied. Patients with any obvious airway related abnormality, restricted mouth opening, short and thick neck, fixation of the trachea, malformation of the skull, teeth or mandible were excluded. Preoperatively, they were assessed for Modified Mallampati grading, thyromental distance, protrusion of jaw and head-neck movements along with Maxillo-pharyngeal angle, measured on lateral cervical radiograph. These parameters were correlated with Cormack Lehane grading during direct laryngoscopy. The observed data were analyzed by using one way analysis of variance (ANOVA) and Pearson’s correlating co-efficient. Results: Modified Mallampati test sensitivity and specificity was found as 39.29% and 65.12% respectively with accuracy of 61.5%. The sensitivity and specificity of Maxillo- Pharyngeal Angle was 85.71 % and 97.09% respectively with accuracy of 95.50 %. Conclusion: The combination of various physical indices along with maxillo-pharyngeal angle in parallel is more sensitive and specific with clinically relevant higher discriminative power.

Prediction of difficult airway by thyromental height test- a comparison with modified mallampati test.

Background: Management of airway is central to the Practice of anaesthesia. One of the anaesthesiologist fundamental roles is to maintain a patent airway at a all times.Maintaining a patent airway is essential for adequate oxygenation and ventilation and failure to do so, even for a brief period of time, can be life threatening. Recently, thyromental height test (TMHT) has been proposed as one of the highly sensitive and specific bedside tests to predict difficult airway.Objective: To assess the predictivity of thyromental height test in comparison to modified Mallampati test.Methods: This cross sectional study was carried out in Anesthesiology department of ISMCH during the period of January, 2015 to December, 2016. A total number of 139 consecutive patients scheduled for elective surgical procedure under general anaesthesia requiring intubation having American Society of Anesthesiologists grading I-II. Statistical analyses of the results were obtained by SPSS-20. Sensitivity, specificity, accuracy, positive predictive value and negative predictive value of Thyromental height test and Modified mallampati scoring in diagnosis of difficult airway were calculated.Results: Most (74.4) of the patients belonged to age ≤50 years. Male to female ratio was 1.01:1. Majority 91(65.5%) patients had thyromental height of ≥50 mm. In the diagnosis of difficult airway, Thyromental height test was 92.7% sensitivity, 93.5% specificity, 93.5% accuracy and 85.4% positive predictive values, 97.8% negative predictive value, 13.1% positive likelihood ratio, 0.05 negative likelihood ratio. On the other hand Modified mallampati scoring was 48.8% sensitivity, 92.7% specificity, 79.1% accuracy, 75.0% positive predictive values, 80.2% negative predictive value, 6.7% positive likelihood ratio, 0.55 negative likelihood ratio for prediction of difficult airway.Conclusions: It can be concluded that the thyromental height is useful diagnostic modality for predicting difficult airway.Bangladesh Journal of Medical Science Vol.17(3) 2018 p.455-461

Airway physical examination tests for detection of difficult airway management in apparently normal adult patients.

Airway physical examination tests for detection of difficult airway management in apparently normal adult patients.

Difficult laryngoscopy and tracheal intubation: observational study

Since anesthesia complications associated with unexpected difficult airway are potentially catastrophic, they should be avoided. The modified Mallampati test and jaw-thrust maneuver enable the identification of difficult airway. The aim of this study was to associate the modified Mallampati test and the jaw-thrust maneuver with laryngoscopy (Cormack-Lehane) in an attempt to identify a better predictor of difficult airway in an adult population undergoing elective surgery. A cross-sectional study in which 133 adult patients undergoing elective surgery requiring tracheal intubation were analyzed. The accuracy and specificity of the modified Mallampati test and jaw-thrust maneuver were assessed by correlating them with difficult laryngoscopy (Cormack-Lehane Degrees 3 and 4). In the 133 patients evaluated the difficult intubation rate found was 0.8%; there was association between the two predictive tests proposed (p=0.012). The values of 94.5% for specificity and 95.4% for accuracy were found for the jaw-thrust maneuver and for the modified Mallampati test, the values found were 81.1% and 81.2%, respectively. Kappa agreement identified a result of 0.240 between jaw-thrust maneuver and Cormarck-Lehane, which was considered reasonable. On the other hand, a poor agreement (κ=0.06) was seen between modified Mallampati test and Cormarck-Lehane test. The jaw-thrust maneuver presented superior accuracy and agreement than the modified Mallampati test, showing the ability to identify a difficult airway. It is necessary to emphasize the association of tests in the evaluation of patients, emphasizing their complementarity to minimize the negative consequences of repeated laryngoscopies.

Difficult laryngoscopy and tracheal intubation: observational study

IntroductionSince anesthesia complications associated with unexpected difficult airway are potentially catastrophic, they should be avoided. The modified Mallampati test and jaw-thrust maneuver enable the identification of difficult airway. The aim of this study was to associate the modified Mallampati test and the jaw-thrust maneuver with laryngoscopy (Cormack–Lehane) in an attempt to identify a better predictor of difficult airway in an adult population undergoing elective surgery. MethodA cross-sectional study in which 133 adult patients undergoing elective surgery requiring tracheal intubation were analyzed. The accuracy and specificity of the modified Mallampati test and jaw-thrust maneuver were assessed by correlating them with difficult laryngoscopy (Cormack–Lehane Degrees 3 and 4). ResultsIn the 133 patients evaluated the difficult intubation rate found was 0.8%; there was association between the two predictive tests proposed (p=0.012). The values of 94.5% for specificity and 95.4% for accuracy were found for the jaw-thrust maneuver and for the modified Mallampati test, the values found were 81.1% and 81.2%, respectively. Kappa agreement identified a result of 0.240 between jaw-thrust maneuver and Cormack–Lehane, which was considered reasonable. On the other hand, a poor agreement (κ=0.06) was seen between modified Mallampati test and Cormack–Lehane test. ConclusionThe jaw-thrust maneuver presented superior accuracy and agreement than the modified Mallampati test, showing the ability to identify a difficult airway. It is necessary to emphasize the association of tests in the evaluation of patients, emphasizing their complementarity to minimize the negative consequences of repeated laryngoscopies.

Radiologic indicators for prediction of difficult laryngoscopy in patients with cervical spondylosis.

BackgroundWe identified the most useful variables for prediction of difficult laryngoscopy in patients with cervical spondylosis according to physical indicators and preoperative skeletal X‐ray and soft tissue MRI measurements. We hypothesized that there was a closer association between difficult laryngoscopy and radiologic indicators.MethodsWe randomly enroled 315 patients undergoing elective cervical spine surgery and analysed the radiological and physical data in predicting difficult laryngoscopy.ResultsWe identified five variables that were most useful in predicting difficult laryngoscopy: the inter‐incisor gap (P = 0.006), modified Mallampati test score (P = 0.004), distance from the highest point of the hyoid bone to the mandibular body (P < 0.001), most antero‐inferior point of the upper central incisor tooth (P < 0.001), and length of the epiglottis (P = 0.002). Binary multivariate logistic regression analyses identified three factors that were independently associated with difficult laryngoscopy: the Mallampati score, distance from the hyoid bone to the mandibular body, and the anterior–inferior point of the upper central incisor tooth. The odds ratios and 95% confidence intervals were 1.547 (1.029–2.327), 1.222 (1.139–1.310), and 1.224 (1.133–1.322), respectively. The AUC for hyoid bone distance to mandibular body (0.832) was larger than that of anterior‐inferior point of the upper central incisor tooth (0.802, P > 0.05) and that of modified Mallampati test (0.602, P < 0.05).ConclusionDistance from the highest point of the hyoid bone to the mandibular body appears to be the most accurate indicator for difficult laryngoscopy in patients with cervical spondylosis.

Comparison of Modified Mallampati Test and Upper Lip Bite Test in Prediction of Difficult Endotracheal Intubation: A Prospective Study

Comparison of Modified Mallampati Test and Upper Lip Bite Test in Prediction of Difficult Endotracheal Intubation: A Prospective Study

Ratio of height to thyromental distance as a predictor of difficult laryngoscopy: A prospective observational study.

Background and Aim:Various airway indices are used either singly or in combination to predict difficult laryngoscopy. Recently introduced ratio of height to thyromental distance (RHTMD) is reported to have better predictability. We aimed to assess the prediction of difficult laryngoscopy by RHTMD and compared it with other indices.Material and Methods:In this prospective, single-blinded comparative observational study, 300 adult patients of either gender scheduled to receive general anesthesia were assessed. Airway indices, like RHTMD, thyromental distance, modified Mallampati test, and upper lip bite test, were assessed and correlated with Cormack and Lehane's laryngoscopic grading. The validity parameters like specificity, sensitivity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated for each test. Effect of combining all the indices was also analyzed. Receiver operating characteristic curves were constructed and optimal cutoff value for the quantitative indices was calculated.Results:The incidence of difficult laryngoscopy in our study was 5.33%. Of the four indices, the single best test was RHTMD, with better sensitivity, high specificity, NPV, and accuracy and with good PPV. A combination of all the indices resulted in 100% sensitivity and higher specificity.Conclusions:RHTMD is a single best preoperative test for predicting difficult laryngoscopy. A combination of tests has higher sensitivity and specificity with better discriminative power. Therefore indices should be used in combination in the preoperative airway assessment of adult patients.

Assessment of the effect of supine posture and phonation on modified mallampati grading and its applicability in prediction of difficult airway

Introduction: As it is not always possible to do Modified Mallampati Test (MMT) in sitting position, this study was designed to test the effect of supine position and phonation on classical MMT and use of such effect in predicting difficult laryngoscopical view or difficult intubation. Aim: To know the effect of phonation and supine position on classical MMT grade and to establish usefulness of modification in predicting difficult laryngoscopy or intubation. Objectives: 1. To compare classical MMT grades with those obtained in supine position with or without phonation. 2. To correlate MMT gradings obtained in all the three variations with Modified Cormack Lehane (MCML) grading and actual difficult intubations to obtain their powers in predicting difficult laryngoscopic view and difficult intubations. Material and Methods: A prospective observational study, conducted at a tertiary care hospital.Consenting, 130 adults, undergoing elective surgical procedures were included. MMT score in sitting position, in supine position with or without phonation was recorded in the preoperative area and MCML grading and actual difficulty for intubation were noted at the time of intubation. Emergency cases and patients with altered airway were excluded.Statistics: 'Kappa' agreement analysis was done to compare the agreement between various scores. Sensitivity, specificity, positive predictive value and negative predictive values were calculated. Results: Supine posture without phonation worsens the classical Mallampati grading whereas supine posture with phonation improves it. MMT in sitting and in supine position without phonation have very good agreement with each other in predicting difficult laryngoscopy and intubation. Conclusions: When the patient cannot sit for examination, MMT scoring can be done in supine position without phonation. Mallampati score in supine position with phonation is not recommended due to high false negatives.

Modified Mallampati Test, Sternomental Distance, and Thyromental Distance for Prediction of Difficult Intubation in Patients Undergoing General Anaesthesia

Modified Mallampati Test, Sternomental Distance, and Thyromental Distance for Prediction of Difficult Intubation in Patients Undergoing General Anaesthesia

The Importance of Neck Circumference to Thyromental Distance Ratio (Nc/Tm Distance Ratio) as a Predictor of Difficult Intubation in Obese Patients Coming for Elective Surgery under General Anaesthesia in a Teritatry Care Hospital - A Prospective Observational Study

BACKGROUND AND OBJECTIVES : This study was done to assess the ability of neck circumference to thyromental distance ratio (NC/TM distance ratio) for predicting difficult intubation among obese patients coming for surgery under general anaesthesia. It enabled us to compare NC/TM distance ratio to routinely used Mallampati score and neck circumference as reliable tests for predicting difficult intubation. This study also identified incidence of difficult intubation among obese individuals. PATIENTS AND METHODS : After approval of institutional review board and ethical committee of Christian Medical College Vellore, 250 obese patients (body mass index greater than or equal to 30) within time frame of September 2014 and March 2015 was assessed preoperatively with the help of performa after obtaining informed consent. Neck circumference / thyromental distance ratio (NC/TM distance ratio) was calculated from the performa. Validated Intubation difficulty score (IDS score) for each obese patient was assessed intra operatively by the anaesthetist who performed intubation . The entire study population were divided into easy and difficult intubation groups based on the IDS score. IDS score greater than or equal to five was considered as difficult intubation. NC/TM distance ratio greater than or equal to five was correlated with IDS score greater than or equal to five. The study assessed the statistical significance of NC/TM distance ratio and difficult intubation by univariate and multivariate logistic regression analysis and its comparison with Mallampati score and neck circumference with respect to sensitivity / specificity/ positive predictive value and negative predictive value. The study also calculated the incidence of difficult intubation among obese patients. RESULTS : Binary univariate logistic regression analysis of predictors of difficult intubation showed age greater than sixty, increased neck circumference, decreased thyromental distance, modified Mallampati test, NC/TMD ratio ≥ 5 as statistically significant variables that were associated with a difficult intubation (p ≤ 0.05). Binary multivariate logistic regression analysis showed only neck circumference (p=0.030 [odd ratio 2.519 (1.094-5.802)] and NC/TMD ratio (p <0.001 [odd ratio 23.680 (10.638-52.713)] independently predicted difficult intubation. However NC/TMD ratio had higher specificity / PPV and larger AUC on an ROC curve compared to neck circumference. The incidence of difficult intubation among obese patients was 20.8 %. INTERPRETATION AND CONCLUSIONS : Among obese patients, NC/TMD ratio can be considered as a better preoperative predictor of difficult intubation and incidence of difficult intubation among them was as high as 20.8 percent.