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1.  Prediction of difficult laryngoscopy: Extended mallampati score versus the MMT, ULBT and RHTMD 
Preoperative using of anatomical landmarks 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.
Materials and Methods:
Four hundred seventy sixadult patients who candidate 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 randomized prospective double - blind. After that, laryngoscopy was performed by an anesthesiologist who didn’t involve in preoperative airway assessment and graded based on Cormack and Lehane's classification. We calculated sensitivity, specificity, and area under receiver-operating characteristic (ROC) (AUC) for each score.
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.
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.
PMCID: PMC4063103  PMID: 24949304
Difficult laryngoscopy; extended mallampati score; modified mallampati; ratio of patient's height to thyromental distance; upper lip bite test
2.  A comparison of between hyomental distance ratios, ratio of height to thyromental, modified Mallamapati classification test and upper lip bite test in predicting difficult laryngoscopy of patients undergoing general anesthesia 
Failed intubation is imperative source of anesthetic interrelated patient's mortality. The aim of this present study was to compare the ability to predict difficult visualization of the larynx from the following pre-operative airway predictive indices, in isolation and combination: Modified Mallampati test (MMT), the ratio of height to thyromental distance (RHTMD), hyomental distance ratios (HMDR), and the upper-lip-bite test (ULBT).
Materials and Methods:
We collected data on 525 consecutive patients scheduled for elective surgery under general anesthesia requiring endotracheal intubation and then evaluated all four factors before surgery. A skilled anesthesiologist, not imparted of the noted pre-operative airway assessment, did the laryngoscopy and rating (as per Cormack and Lehane's classification). Sensitivity, specificity, and positive predictive value for every airway predictor in isolation and in combination were established.
The most sensitive of the single tests was ULBT with a sensitivity of 90.2%. The hyomental distance extreme of head extension was the least sensitive of the single tests with a sensitivity of 56.9. The HMDR had sensitivity 86.3%. The ULBT had the highest negative predictive value: And the area under a receiver-operating characteristic curve (AUC of ROC curve) among single predictors. The AUC of ROC curve for ULBT, HMDR and RHTMD was significantly more than for MMT (P < 0.05). No significant difference was noted in the AUC of ROC curve for ULBT, HMDR, and RHTMD (P > 0.05).
The HMDR is comparable with RHTMD and ULBT for prediction of difficult laryngoscopy in the general population, but was significantly more than for MMT.
PMCID: PMC4162034  PMID: 25221769
Failed intubation; hyomental distance ratios; laryngoscopy; modified Mallampati test; ratio of height to thyromental distance; upper-lip-bite test
3.  The predictive value of the ratio of neck circumference to thyromental distance in comparison with four predictive tests for difficult laryngoscopy in obstetric patients scheduled for caesarean delivery 
Preoperative assessment of anatomical landmarks andclinical factors help detect potentially difficult laryngoscopies. The aim of the present study was to compare the ability to predict difficult visualization of the larynx from thefollowing preoperative airway predictive indices, in isolation and combination: Neck circumference to thyromental distance (NC/TMD), neck circumference (NC), modified Mallampatitest (MMT), the ratio of height to thyromental distance (RHTMD), and the upper-lip-bite test (ULBT).
Materials and Methods:
We collected data on657 consecutive patients scheduled for elective caesarean delivery under general anesthesia requiring endotracheal intubation and then evaluated all five factors before caesarean. An experienced anesthesiologist, not informed of the recorded preoperative airway evaluation, performed the laryngoscopy and grading (as per Cormack and Lehane's classification). Sensitivity, specificity, and positive and negative predictive values for each airway predictor in isolation and in combination were determined.
Difficult laryngoscopy (Grade 3 or 4) occurred in 53 (8.06%) patients. There were significant differences in thyromental distance (TMD), RHTMD, NC, and NC/TMD between difficult visualization of larynx and easy visualization of larynx patients (P < 0.05). The main end-point area under curve (AUC) of the receiver-operating characteristic (ROC) was lower for MMT (AUC = 0.497; 95% Confidence Interval = CI,0.045-0.536) and ULBT (AUC = 0.500, 95% CI, 0.461-0.539) compared to RHTMD, NC, TMD, and NC/TMD score ([AUC = 0.627, 95% CI, 0.589-0.664], [AUC = 0.691; 95% CI, 0.654-0.726], [AUC = 0.606; 95% CI, 0.567-0.643], [AUC = 0.689;95% CI, 0.625-0.724], respectively), and the differences of six ROC curves were statistically significant (P < 0.05).
The NC/TM Discomparable with NC, RHTMD, and ULBT for the prediction of difficult laryngoscopy in caes are an delivery.
PMCID: PMC4202503  PMID: 25337530
Caesarean delivery; difficult laryngoscopy; modified Mallampati test; neck circumference; neck circumference to thyromental distance; ratio of height to thyromental distance; upper-lip-bite test
4.  Predictive value of upper lip bite test and ratio of height to thyromental distance compared to other multivariate airway assessment tests for difficult laryngoscopy in apparently normal patients 
Various anatomical measurements and non-invasive clinical tests, singly or in various combinations can be performed to predict difficult intubation. Recently introduced “Upper lip bite test” (ULBT) and “Ratio of height to Thyromental distance” (RHTMD) are claimed to have high predictability. We conducted a study to compare the Predictive Value of ULBT and RHTMD with Mouth opening (Inter-Incisor gap) (IIG), Modified Mallampatti Test (MMT), Head and neck movement (HNM) and Thyromental Distance (TMD) for Difficult Laryngoscopy.
Materials and Methods:
In this prospective, single blinded observational study, 480 adult patients of either sex, ASA grade I and II were assessed and graded for ULBT, RHTMD, TMD, MMT, IIG, and HNM according to standard methods and correlated with the Cormack and Lehane grade.
ULBT and RHTMD had highest sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratio, i.e., 74.63%, 91.53%, 58.82%, 95.7%, 31.765 and 71.64%, 92.01%, 59.26%, 95.24%, 8.96 respectively, compared to TMD, MMT, IIG and HNM.
ULBT is the best predictive test for difficult laryngoscopy in apparently normal patients but RHTMD can also be used as an acceptable alternative.
PMCID: PMC3713666  PMID: 23878440
Airway assessment tests; difficult laryngoscopy; ratio of height to thyromental distance; upper lip bite test
5.  Anatomic features of the neck as predictive markers of difficult direct laryngoscopy in men and women: A prospective study 
Indian Journal of Anaesthesia  2014;58(2):176-182.
Background and Aims:
Difficult airway assessment is based on various anatomic parameters of upper airway, much of it being concentrated on oral cavity and the pharyngeal structures. The diagnostic value of tests based on neck anatomy in predicting difficult laryngoscopy was assessed in this prospective, open cohort study.
We studied 341 adult patients scheduled to receive general anaesthesia. Thyromental distance (TMD), sternomental distance (STMD), ratio of height to thyromental distance (RHTMD) and neck circumference (NC) were measured pre-operatively. The laryngoscopic view was classified according to the Cormack–Lehane Grade (1-4). Difficult laryngoscopy was defined as Cormack–Lehane Grade 3 or 4. The optimal cut-off points for each variable were identified by using receiver operating characteristic analysis. Sensitivity, specificity and positive predictive value and negative predictive value (NPV) were calculated for each test. Multivariate analysis with logistic regression, including all variables, was used to create a predictive model. Comparisons between genders were also performed.
Laryngoscopy was difficult in 12.6% of the patients. The cut-off values were: TMD ≤7 cm, STMD ≤15 cm, RHTMD >18.4 and NC >37.5 cm. The RHTMD had the highest sensitivity (88.4%) and NPV (95.2%), while TMD had the highest specificity (83.9%). The area under curve (AUC) for the TMD, STMD, RHTMD and NC was 0.63, 0.64, 0.62 and 0.54, respectively. The predictive model exhibited a higher and statistically significant diagnostic accuracy (AUC: 0.68, P < 0.001). Gender-specific cut-off points improved the predictive accuracy of NC in women (AUC: 0.65).
The TMD, STMD, RHTMD and NC were found to be poor single predictors of difficult laryngoscopy, while a model including all four variables had a significant predictive accuracy. Among the studied tests, gender-specific cut-off points should be used for NC.
PMCID: PMC4050935  PMID: 24963183
Height-to-thyromental distance ratio; laryngoscopy; neck circumference; sternomental distance; thyromental distance
6.  A comparison of the upper lip bite test with hyomental/thyrosternal distances and mandible length in predicting difficulty in intubation: A prospective study 
Indian Journal of Anaesthesia  2011;55(1):43-46.
The incidence of difficulty in tracheal intubation has been reported to range from 0.5 to 18% in patients undergoing surgery. We aimed to elucidate the role of upper lip bite test (ULBT) with other prevailing tests, hyomental/thyrosternal distances (HMD/TSD), and the mandible length (ML) and their possible correlation in predicting difficulty in intubation. After institutional approval and informed consent were obtained, 300 consecutive patients aged 20–60 years of ASA physical status I and II, scheduled for elective surgical procedures requiring tracheal intubation and meeting the inclusion criteria, were enrolled in this study. Each patient was evaluated regarding ULBT, HMD, TSD and ML. Laryngoscopy was assessed by an attending anaesthesiologist blinded to the measurements. The laryngoscopic result was graded according to Cormack and Lehane’s Grading system. The negative predictive value (NPV) and positive predictive value (PPV) of ULBT were found to be 94 and 100%, respectively. These corresponding figures for TSD were 88.5 and 0%, respectively. Specificities for ULBT, HMD, ML and TSD were 100, 98.9, 98.9 and 98.1%, respectively. ULBT class and laryngoscopic grading showed the greatest agreement (kappa = 0.61, P < 0.001). An agreement between laryngoscopic grading and HMD and ML also existed (0.003 and <0.001, respectively), but was comparatively weaker. The high specificity, NPV, PPV and accuracy of ULBT as revealed in this study could be a good rationale for its application in the prediction of difficulty or easiness in intubation. ML > 9 cm and HMD > 3.5 cm were good predictors of negative difficult intubation.
PMCID: PMC3057244  PMID: 21431052
Difficult intubation; difficult laryngoscopy; endotracheal intubation; predictive airway tests
7.  Predictors of difficult intubation defined by the intubation difficulty scale (IDS): predictive value of 7 airway assessment factors 
Korean Journal of Anesthesiology  2012;63(6):491-497.
The intubation difficulty scale (IDS) has been used as a validated difficulty score to define difficult intubation (DI). The purpose of this study is to identify airway assessment factors and total airway score (TAS) for predicting DI defined by the IDS.
There were 305 ASA physical status 1-2 patients, aged 19-70 years, who underwent elective surgery with endotracheal intubation. During the pre-anesthetic visit, we evaluated patients by 7 preoperative airway assessment factors, including the following: Mallampati classification, thyromental distance, head & neck movement, body mass index (BMI), buck teeth, inter-incisor gap, and upper lip bite test (ULBT). After endotracheal intubation, patients were divided into 2 groups based on their IDS score estimated with 7 variables: normal (IDS < 5) and DI (IDS ≥ 5) groups. The incidence of TAS (> 6) and high score of each airway assessment factor was compared in two groups: odds ratio, confidence interval (CI) of 95%, with a significant P value ≤ 0.05.
The odds ratio of TAS (> 6), ULBT (class III), head & neck movement (< 90°), inter-incisor gap (< 4 cm), BMI (≥ 25 kg/m2) and Mallampati classification (≥ class III) were respectively 13.57 (95% CI = 2.99-61.54, P < 0.05), 12.48 (95% CI = 2.50-62.21, P < 0.05), 3.11 (95% CI = 0.87-11.13), 2.32 (95% CI = 0.75-7.19), 2.22 (95% CI = 0.81-6.06), and 1.22 (95% CI = 0.38-3.89).
We suggest that TAS (> 6) and ULBT (class III) are the most useful factors predicting DI.
PMCID: PMC3531526  PMID: 23277808
Anesthesia; Evaluation studies; Intubation
8.  Difficult laryngoscopy and intubation in the Indian population: An assessment of anatomical and clinical risk factors 
Indian Journal of Anaesthesia  2013;57(6):569-575.
Background and Aim:
Differences in patient characteristics due to race or ethnicity may influence the incidence of difficult airway. Our purpose was to determine the incidence of difficult laryngoscopy and intubation, as well as the anatomical features and clinical risk factors that influence them, in the Indian population.
In 330 adult patients receiving general anaesthesia with tracheal intubation, airway characteristics and clinical factors were determined and their association with difficult laryngoscopy (Cormack and Lehane grade 3 and 4) was analysed. Intubation Difficulty Scale score was used to identify degree of difficult laryngoscopy.
The incidence of difficult laryngoscopy and intubation was 9.7% and 4.5%, respectively. Univariate analysis showed that increasing age and weight, male gender, modified Mallampati class (MMC) 3 and 4 in sitting and supine positions, inter-incisor distance (IID) ≤3.5 cm, thyromental (TMD) and sternomental distance, ratio of height and TMD, short neck, limited mandibular protrusion, decreased range of neck movement, history of snoring, receding mandible and cervical spondylosis were associated with difficult laryngoscopy. Multivariate analysis identified four variables that were independently associated with difficult laryngoscopy: MMC class 3 and 4, range of neck movement <80°, IID ≤ 3.5 cm and snoring.
We found an incidence of 9.7% and 4.5% for difficult laryngoscopy and difficult intubation, respectively, in Indian patients with apparently normal airways. MMC class 3 and 4, range of neck movement <80°, IID ≤ 3.5 cm and snoring were independently related to difficult laryngoscopy. There was a high incidence (48.5%) of minor difficulty in intubation.
PMCID: PMC3883391  PMID: 24403616
Airway evaluation; difficult intubation; difficult laryngoscopy; intubation difficulty scale
9.  Sensitivity of palm print sign in prediction of difficult laryngoscopy in diabetes: A comparison with other airway indices 
Indian Journal of Anaesthesia  2014;58(3):298-302.
Background and Aims:
Diabetic patients are prone for the limited joint mobility syndrome. The atlanto-occipital joint involvement limits adequate extension of head and neck during laryngoscopy making intubation difficult. The collagen glycosylation starts in the fourth and fifth inter-phalangeal joints. The degree of inter-phalangeal involvement can be assessed by scoring the ink impression made by the palm of the dominant hand (palm print [PP] sign) The aim of our study was to evaluate the PP sign as a screening tool for predicting difficult laryngoscopy in diabetic patients.
A total of 60 diabetic patients undergoing general anaesthesia with endotracheal intubation were assessed pre-operatively for their airway indices using the modified Mallampati test, thyromental distance, degree of head extension, the PP test and the prayer sign and their corresponding Cormack–Lehane scores were noted. Statistical analysis was performed using Fischer exact test.
Of the 60 patients, 15 had positive PP sign. Of the 13 difficult laryngoscopies encountered, 10 patients had a positive PP sign. PP sign was the most sensitive index in predicting difficult laryngoscopy. P =0.000 was obtained and considered as statistically significant. The sensitivity was 76.9%, specificity 89.4%, positive and negative predictive value 71.4% and 91.3% and accuracy 86.7%, respectively. The other signs were not significant in predicting difficult laryngoscopy.
The PP test appears to be the most sensitive and specific in the prediction of difficult laryngoscopy in diabetic patients.
PMCID: PMC4090996  PMID: 25024473
Diabetes; difficult intubation; limited joint mobility
10.  The prediction of difficult intubation in obese patients using mirror indirect laryngoscopy: A prospective pilot study 
The incidence of difficult laryngoscopy and intubation in obese patients is higher than in the general population. Classical predictors of difficult laryngoscopy and intubation have been shown to be unreliable. We prospectively evaluated indirect mirror laryngoscopy as a predictor of difficult laryngoscopy in obese patients.
Materials and Methods:
60 patients with a body mass index (BMI) greater than 30, scheduled to undergo general anesthesia, were enrolled. Indirect mirror laryngoscopy was performed and was graded 1-4 according to Cormack and Lehane. A view of grade 3-4 was classified as predicting difficult laryngoscopy. Additional assessments for comparison were the Samsoon and Young modification of the Mallampati airway classification, Wilson Risk Sum Score, neck circumference, and BMI. The view obtained upon direct laryngoscopy after induction of general anesthesia was classified according to Cormack and Lehane as grade 1-4.
Sixty patients met the inclusion criteria; however, 8 (13.3%) patients had an excessive gag reflex, and examination of the larynx was not possible. 15.4% of patients who underwent direct laryngoscopy had a Cormack and Lehane grade 3 or 4 view and were classified as difficult. Mirror laryngoscopy had a tendency toward statistical significance in predicting difficult laryngoscopy in these patients.
This study is consistent with previous studies, which have demonstrated that no one individual traditional test has proven to be adequate in predicting difficult airways in the obese population. However, the new application of an old test - indirect mirror laryngoscopy - could be a useful additional test to predict difficult laryngoscopy in obese patients.
PMCID: PMC3713664  PMID: 23878438
Difficult airway; mirror indirect laryngoscopy; obesity; prediction
11.  Diagnostic value of the upper lip bite test in predicting difficulty in intubation with head and neck landmarks obtained from lateral neck X-ray 
Indian Journal of Anaesthesia  2013;57(4):381-386.
Unanticipated difficult tracheal intubation remains a primary concern of anaesthesiologists and upper lip bite test (ULBT) is one of the assessments used in predicting difficult intubation. In this study, we aimed to check the utility of lateral neck X-ray measurements in improving the diagnostic value of the ULBT.
In a prospective study conducted from January 2007 until December 2010, we recorded personal and demographic data of 4500 patients who entered the study and subjected them to standard lateral neck radiography. Before the induction of anaesthesia, clinical examination and ULBT results were recorded and during induction of anaesthesia laryngoscopic grading was evaluated and recorded in questionnaires. All the compiled data were analysed by SPSS 14.0 (SPSS Inc., Chicago, IL, USA) software. Diagnostic value for each test was calculated and compared.
Negative predictive values (NPVs) were high in all tests. ULBT had the highest specificity and NPV compared with the other tests. The positive predictive value for all the tests had been low, but marginally high in the ULBT.
Although all the tests used had relatively acceptable predictive values, combination of tests appeared to be more predictive. Highest sensitivities were observed with ULBT, mandibulohyoid distance and thyromental distance respectively. Use of radiological parameters may not be suitable as screening tools, but may help in anticipating and preparing for a difficult scenario.
PMCID: PMC3800331  PMID: 24163453
Airway assessment; difficult intubation; lateral neck radiography; predictive tests; upper lip bite test
12.  Predicting difficult laryngoscopy in acromegalic patients undergoing surgery for excision of pituitary tumors: A comparison of extended Mallampati score with modified Mallampati classification 
There are numerous reports of difficult laryngoscopy and intubation in patients with acromegaly. To date, no study has assessed the application of extended Mallampati score (EMS) for predicting difficult intubation in acromegalics. The primary aim of this study was to compare EMS with modified Mallampati classification (MMP) in predicting difficult laryngoscopy in acromegalic patients. We hypothesized that since EMS has been reported to be more specific and better predictor than MMP, it may be superior to the MMP to predict difficult laryngoscopy in acromegalic patients.
Materials and Methods:
For this prospective cohort study with matched controls, acromegalic patients scheduled to undergo pituitary surgery over a period of 3 years (January 2008-December 2010) were enrolled. Preoperative airway assessment was performed by experienced anesthesiologists and involved a MMP and the EMS. Under anesthesia, laryngoscopic view was assessed using Cormack-Lehane (CL) grading. MMP and CL grades of I and II were defined “easy” and III and IV as “difficult”. EMS grade of I and II were defined “easy” and III as “difficult”. Data were used to determine the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MMP and EMS in predicting difficult laryngoscopy.
Seventy eight patients participated in the study (39 patients in each group). Both MMP and EMS failed to detect difficult laryngoscopy in seven patients. Only one laryngoscopy was predicted to be difficult by both tests which was in fact, difficult.
We found that addition of neck extension did not improve the predictive value of MMP.
PMCID: PMC3713665  PMID: 23878439
Acromegaly; airway; extended Mallampati score; Mallampati classification
13.  Role of Anterior Neck Soft Tissue Quantifications by Ultrasound in Predicting Difficult Laryngoscopy 
The aim of this study was to determine if ultrasound (US) measurements of anterior neck soft tissue thickness at hyoid bone (DSHB), thyrohyoid membrane (DSEM), and anterior commissure (DSAC) levels can be used to predict difficult laryngoscopy.
We included 203 patients age 20–65 years scheduled to undergo general anesthesia in this prospective observational study. Correlation analysis and receiver operating characteristic curve (ROC) analysis were used to determine the roles of screening tests [interincisor gap (IIG), thyromental distance (TMD), modified Mallampati score (MMS)] and US measurements (DSHB, DSEM, DSAC) in predicting difficult laryngoscopy.
There were 28 out of 203 patients categorized as difficult laryngoscopy. DSHB, DSEM, DSAC, and MMS were greater in the difficult laryngoscopy group (P<0.0001). There was a strong positive correlation between DSEM and DSHB (r=0.74); moderate positive correlations between DSEM and DSAC (r=0.60), DSHB and DSAC (r=0.69); small positive correlations between MMS and DSHB (r=0.32), MMS and DSEM (r=0.27), MMS and DSAC (r=0.32), all P values ≤0.0001; very small positive correlation between TMD and IIG (r=0.18, P=0.0089); small negative correlation between IIG and MMS (r=−0.27, P=0.0001); and very small negative correlations between MMS and TMD (r=−0.20, P=0.004), IIG and DSAC (r=−0.18, P=0.011), IIG and DSHB (r=−0.15, P=0.034). The areas under the ROC curve (AUCs) of MMS, DSHB, DSEM, and DSAC were significantly larger compared with the reference line (P<0.0001).
Anterior neck soft tissue thicknesses measured by US at hyoid bone, thyrohyoid membrane, and anterior commissure levels are independent predictors of difficult laryngoscopy. Combinations of those screening tests or risk factors with US measurements might increase the ability to predict difficult laryngoscopy.
PMCID: PMC4247231  PMID: 25403231
Airway Management; Anesthesia; Critical Care; Laryngoscopy; Ultrasonography
14.  Comparison of Mallampati test with lower jaw protrusion maneuver in predicting difficult laryngoscopy and intubation 
Failure to maintain a patent airway is one of the commonest causes of anesthesia-related morbidity and mortality. Many protocols, algorithms, and different combinations of tested methods for airway assessment have been developed to predict difficult laryngoscopy and intubation. The reported incidence of a difficult intubation varies from 1.5% to 13%. The objective of this study was to compare Mallampati test (MT) with lower jaw protrusion (LJP) maneuver in predicting difficult laryngoscopy and intubation.
Materials and Methods:
Seven hundred and sixty patients were included in the study. All the patients underwent MT and LJP maneuver for their airway assessment. After a standardized technique of induction of anesthesia, primary anesthetist performed laryngoscopy and graded it according to the grades described by Cormack and Lehane. Sensitivity, specificity, accuracy, and positive predictive value (PPV) and negative predictive value (NPV) were calculated for both these tests with 95% confidence interval (CI) using conventional laryngoscopy as gold standard. Area under curve was also calculated for both, MT and LJP maneuver. A P < 0.05 was taken as significant.
LJP maneuver had higher sensitivity (95.9% vs. 27.1%), NPV (98.7% vs. 82.0%), and accuracy (90.1% vs. 80.3%) when compared to MT in predicting difficult laryngoscopy and intubation. Both tests, however, had similar specificity and PPV. There was marked difference in the positive and negative likelihood ratio between LJP and MT. Similarly, the area under the curve favored LJP maneuver over MT.
The results of this study show that LJP maneuver is a better test to predict difficult laryngoscopy and tracheal intubation. We recommend the addition of this maneuver to the routine preoperative evaluation of airway.
PMCID: PMC3788227  PMID: 24106353
Airway; difficult intubation; lower jaw protrusion maneuver; Mallampati test
15.  Validation of modified Mallampati test with addition of thyromental distance and sternomental distance to predict difficult endotracheal intubation in adults 
Indian Journal of Anaesthesia  2014;58(2):171-175.
Background and Aims:
Intubation is often a challenge for anaesthesiologists. Many parameters assist to predict difficult intubation. The present study was undertaken to assess the validity of different parameters in predicting difficult intubation for general anaesthesia (GA) in adults and effect of combining the parameters on the validity.
The anaesthesiologist assessed oropharynx of 135 adult patients. Modified Mallampati test (MMT) was used and the thyromental distance (TMD) and sternomental distances (SMD) for each of the patients were also measured. The Cormack and Lehane laryngoscopic grading was assessed following laryngoscopy. The validity parameters such as sensitivity, specificity, false positive and negatives values, positive and negative predictive values were calculated. The effect of combining different measurements on the validity was also studied. Univariate analysis was performed using the parametric method.
The study group comprised of 135 patients. The sensitivity and specificity of MMT were 28.6% and 93%, respectively. The TMD (<6.5 CM) had sensitivity and specificity of 100% and 75.8%, respectively. The SMD (<12.5 CM) had sensitivity and specificity of 91% and 92.7%, respectively. Combination of MMT grading and TMD and SMD measurements increased the validity (sensitivity of 100% and specificity of 92.7%).
MMT had high specificity. The validity of combination of MMT, SMD and TMD as compared to MMT alone was very high in predicting difficult intubation in adult patients. All parameters should be used in assessing an adult patient for surgery under GA.
PMCID: PMC4050934  PMID: 24963182
Anaesthesia; endotracheal intubation; modified Mallampatti test; validity
16.  Assessment of difficult laryngoscopy by electronically measured maxillo-pharyngeal angle on lateral cervical radiograph: A prospective study 
Saudi Journal of Anaesthesia  2010;4(3):158-162.
Difficult airway continued to be a major cause of anesthesia-related morbidity and mortality. Successful airway management depends on direct laryngoscopy and tracheal intubation. Difficult laryngoscopy is a resultant of incomplete structural arrangements during the process of head positioning. Through clinical history, examination of the patients along with craniofacial indices alerts the anesthetist for difficult laryngoscopy. But it does not predict all causes of difficult laryngoscopy during pre-anesthetic evaluation. The maxillo-pharyngeal angle, an upper airway anatomical balance, was proposed for better understanding the pathophysiology of difficult laryngoscopy. In our study we have assess difficult laryngoscopy by electronically measuring maxillo-pharyngeal angles on a lateral cervical radiograph. This angle is normally greater than 100°. Less than 90° angle suggests either impossible or difficult direct laryngoscopy when all known craniofacial indices were within the normal range. Cervical radiographic assessment is a simple, economical, and non-invasive predictive method for difficult laryngoscopy. It should be used routinely along with other indices as pre-anesthetic airway assessment criteria to predict the difficult laryngoscopy.
Difficulties with airway management continue to be a major cause of anesthesia-related morbidity, mortality, and litigation. Pre-operative assessment of difficult laryngoscopy by the simple and non-invasive radiological method can help to prevent them.
To assess the difficult laryngoscopy pre operatively by a simple and non invasive radiological method by electronically measuring maxillo-pharyngeal angle on a lateral cervical radiograph and it’s correlation with Cormack and Lehane grading.
Settings and Design:
This is a controlled, nonrandomized, prospective, cohort observation study.
Patients and Methods:
The 157 adult consented patients of ASA grade I to III of either sex, scheduled for elective surgery under general anesthesia with endo-tracheal intubation, were studied. The patients with identified difficult airway indices were excluded from the study. The maxillo-pharyngeal angle was electronically measured on a lateral cervical radiograph and was correlated with ease or difficulty of laryngoscopy under general anesthesia. Their degree of laryngeal exposure according to Cormack and Lehane classification grade was also noted.
Statistical Analysis used:
We performed univariate analyses to evaluate the association between the covariates and direct laryngoscopy.
In 148 patients (94.28%), the maxillo-pharyngeal angle was more than 100°, in 7 patients (4.45%) it was less than 90°, and in 2 patients (1.27%) the M-P angle was less than 85° with normal craniofacial indices. When the MP angle was less than 90°, the direct laryngoscopy was difficult which could be compared with to Cormack and Lehane classification grade III and IV.
Lateral cervical radiographic assessment should be used as pre-anesthetic airway assessment criteria to predict the difficult laryngoscopy as it is a simple, safe and non-invasive method.
PMCID: PMC2980661  PMID: 21189852
Maxillo-pharyngeal angle; laryngoscopy; cervical radiograph; electronic measurement of angle; Cormack and Lehane grade
17.  Risk Factors Assessment of the Difficult Intubation using Intubation Difficulty Scale (IDS) 
Background: The major responsibility of anaesthesiologist is to maintain adequate gas exchange in his patients in all circumstances and this require that patency of upper airway is constantly maintained. Problems with upper airway management are among the most frequent causes of anaesthetic mishaps. Using intubation difficulty scale (IDS) we made an attempt to objectively assess the predictors of difficult intubation. We assessed classical bedside tests such as modified Mallampati test, Thyromental distance test and also neck extension test.
Methods: We prospectively observed 400 patients undergoing general anaesthesia with endotracheal intubation, for each patient intubation difficulty score was recorded during intubation. Risk factors assessment of difficult intubation done using IDS. Risk factor assessed includes modified mallampati class III and IV, thyromental distance ≤ 6cm and neck extension < 5cm. Patients were categorised as Easy intubation (IDS, 0 to 2), slightly difficult intubation (IDS, 3 to 4) and difficult intubation (IDS 5). Preoperative airway assessment was done by thyromental distance measurement, neck extension measurement and modified mallampati test. Data was analysed using Receiver operating characteristic curve (ROC) and area under curve (AUC) for each test computed. p<0.05 was considered significant.
Results: The incidence of difficult intubation was 8% and there were no failure to intubate the trachea. The AUC were as follows: modified Mallampati test 0.473 (p<0.005), Thyromental distance test 0.753 (p<0.005) and neck extension test 0.768 (p<0.005).
Conclusion: The results indicate that neck extension test is strongest predictor of difficult intubation (IDS≥5) in comparison to Thyromental test and modified mallampati test.
PMCID: PMC4149082  PMID: 25177576
Airway; Difficult intubation; Mallampati
18.  Comparing ease of intubation in obese and lean patients using intubation difficulty scale 
Difficult tracheal intubation contributes to significant morbidity and mortality during induction of anesthesia. There are divided opinions regarding ease of intubation in obese patients. Moreover, the definition of difficult intubation is not uniform; hence we have use the Intubation Difficulty Scale (IDS) to find the incidence of difficult intubation in obese patients.
The primary aim of the following study is to find out the incidence of difficult intubation in obese and lean patients using IDS and secondary aim is to assess the performance of bedside screening tests to predict difficult intubation, mask ventilation and laryngoscopy in obese and lean patients.
Materials and Methods:
A prospective, observational cohort study of 200 patients requiring general anesthesia were categorized into 100 each based on body mass index (BMI) into lean (BMI <25 kg/m2) and obese (BMI ≥25 kg/m2) groups. IDS score ≥5 was termed as difficult intubation. Pre-operative airway assessment included Mallampati score, mouth opening, neck circumference (NC), upper lip bite test, thyromental distance, sternomental distance (SMD) and head neck mobility. Patients having difficulty in mask ventilation and laryngoscopy was recorded.
Over all in 200 patients the incidence of difficult intubation was 9%. Obese patients were slightly more difficult to intubate than lean (11% vs. 7%, P = 0.049). Age >40 years, NC >35 cm, SMD <12.5 cm and restricted head neck mobility were factors which were associated with IDS ≥5. Multivariate analysis revealed SMD <12.5 cm to predict difficult intubation in obese patients. Obese patients were difficult to mask ventilate (6% vs. 1%, P = 0.043). There was no difference regarding grading of laryngoscopy between the two groups.
Obese patients are difficult to mask ventilate and intubate. During intubation of obese patients who is more than 40 years age and SMD <12.5 cm, it is preferable to have a second skilled anesthesiologist.
PMCID: PMC4173612
Difficult intubation; intubation difficulty scale; lean; obese
19.  Is ultrasonic investigation of transverse tracheal air shadow diameter reasonable for evaluation of difficult airway in pregnant women: A prospective comparative study 
Objective: The aim of this study was to compare clinical screening tests (modified Mallampati score, Cormack-Lehane score, thyromental distance, and sternomental distance) with ultrasonic measurements of the upper airway in predicting difficult intubation in pregnant women whose Body Mass Index (BMI) is higher and lower than 30 kg m-2.
Methods: This study was designed as a prospective observational trial, and consisted of 40 pregnant women of American Society of Anesthesiologists (ASA) 1-2 groups. Patients with a BMI lower than 30 kg m-2 were included in Group 1 (n=20), and patients with a BMI higher than 30 kg m-2 were included in Group 2 (n=20). In the supine position with head in mild extension, the diameter of the transverse tracheal air shadow in the subglottic area of the front neck was measured using ultrasonography. Modified Mallampati score, Cormack-Lehane score, thyromental distance and sternomental distance measurements were recorded.
Results: No statistically significant difference was detected between groups regarding mean age, mean number of pregnancy, ASA scores and comorbid disease. Mean body weight (p=0.0001) and mean pre-pregnancy weight (p=0.0001) were significantly higher in Group 2. There was no statistically significant difference between groups regarding mean modified Mallampati score, thyromental distance, sternomental distance measurements, Cormack-Lehane score, and mean ultrasonic measurements.
Conclusion: It was found that BMI higher or lower than 30 kg m-2 has no effect on ultrasonic measurements and clinical airway tests. We thought that ultrasonic measurement could not give us valuable information in obese or non-obese pregnant women.
PMCID: PMC3955549  PMID: 24639838
Pregnancy; body mass index; obesity; airway evaluation; ultrasonography; diameter of transverse tracheal air shadow
20.  Prediction of Difficult Laryngoscopy in Obese Patients by Ultrasound Quantification of Anterior Neck Soft Tissue1 
Anaesthesia  2003;58(11):1111-1114.
Prediction of difficult laryngoscopy in obese patients is challenging. In 50 morbidly obese patients, we quantified the neck soft tissue from skin to anterior aspect of trachea at the vocal cords using ultrasound. Thyromental distance <6 cm, mouth opening <4 cm, limited neck mobility, Mallampati score >2, abnormal upper teeth, neck circumference >45 cm, and sleep apnoea were considered predictors of difficult laryngoscopy. Of the nine (18%) difficult laryngoscopy cases, seven had obstructive sleep apnoea history; whereas, only 2 of the 41 easy laryngoscopy patients did (P<0.001). Difficult laryngoscopy patients had larger neck circumference [50 (3.8) vs. 43.5 (2.2) cm; P<0.001] and more pre-tracheal soft tissue [28 (2.7) mm vs. 17.5 (1.8) mm; P<0.001] [mean (SD)]. Soft tissue values completely separated difficult and easy laryngoscopies. None of the other predictors correlated with difficult laryngoscopy. Thus, an abundance of pretracheal soft tissue at the level of vocal cords is a good predictor of difficult laryngoscopy in obese patients.
PMCID: PMC1283106  PMID: 14616599
Anaesthesia; Neck; Obesity; Ultrasound
21.  Video laryngoscopy improves intubation success and reduces esophageal intubations compared to direct laryngoscopy in the medical intensive care unit 
Critical Care  2013;17(5):R237.
Tracheal intubation in the Intensive Care Unit (ICU) can be challenging as patients often have anatomic and physiologic characteristics that make intubation particularly difficult. Video laryngoscopy (VL) has been shown to improve first attempt success compared to direct laryngoscopy (DL) in many clinical settings and may be an option for ICU intubations.
All intubations performed in this academic medical ICU during a 13-month period were entered into a prospectively collected quality control database. After each intubation, the operator completed a standardized form evaluating multiple aspects of the intubation including: patient demographics, difficult airway characteristics (DACs), method and device(s) used, medications used, outcomes and complications of each attempt. Primary outcome was first attempt success. Secondary outcomes were grade of laryngoscopic view, ultimate success, esophageal intubations, and desaturation. Multivariate logistic regression was performed for first attempt and ultimate success.
Over the 13-month study period (January 2012-February 2013), a total of 234 patients were intubated using VL and 56 patients were intubated with DL. First attempt success for VL was 184/234 (78.6%; 95% CI 72.8 to 83.7) while DL was 34/56 patients (60.7%; 95% CI 46.8 to 73.5). Ultimate success for VL was 230/234 (98.3%; 95% CI 95.1 to 99.3) while DL was 52/56 patients (91.2%; 95% CI 81.3 to 97.2). In the multivariate regression model, VL was predictive of first attempt success with an odds ratio of 7.67 (95% CI 3.18 to 18.45). VL was predictive of ultimate success with an odds ratio of 15.77 (95% CI 1.92 to 129). Cormack-Lehane I or II view occurred 199/234 times (85.8%; 95% CI 79.5 to 89.1) and a median POGO (Percentage of Glottic Opening) of 82% (IQR 60 to 100) with VL, while Cormack-Lehane I or II view occurred 34/56 times (61.8%; 95% CI 45.7 to 71.9) and a median POGO of 45% (IQR 0 to 78%) with DL. VL reduced the esophageal intubation rate from 12.5% with DL to 1.3% (P = 0.001) but there was no difference in desaturation rates.
In the medical ICU, video laryngoscopy resulted in higher first attempt and ultimate intubation success rates and improved grade of laryngoscopic view while reducing the esophageal intubation rate compared to direct laryngoscopy.
PMCID: PMC4056427  PMID: 24125064
22.  Evaluation of Truview evo2® Laryngoscope In Anticipated Difficult Intubation – A Comparison To Macintosh Laryngoscope 
Indian Journal of Anaesthesia  2009;53(2):164-168.
The aim of the study was to assess and compare laryngoscopic view of Truview evo2 laryngoscope with that of Macintosh laryngoscope in patients with one or more predictors of difficult intubation (PDI). Moreover ease of intubation with Truview evo2 in terms of absolute time requirement was also aimed at. Patients for elective surgery requiring endotracheal intubation were initially assessed for three PDI parameters – modified Mallampati test, thyro-mental distance & Atlanto-occipital (AO) joint extension. Patients with cumulative PDI scores of 2 to 5 (in a scale of 0 to 8) were evaluated for Cormack & Lehane (CL) grading by Macintosh blade after standard induction. Cases with CL grade of two or more were further evaluated by Truview evo2 laryngoscope and corresponding CL grades were assigned. Intubation attempted under Truview evo2 vision and time required for each successful tracheal intubation (i.e. tracheal intubation completed within one minute) was noted. Total fifty cases were studied. The CL grades assigned by Macintosh blade correlated well with the cumulative PDI scores assigned preoperatively, confirming there predictability. Truview evo2 improved laryngeal view in 92 % cases by one or more CL grade. Intubation with Truview evo2 was possible in 88% cases within stipulated time of one minute and mean time of 28.6 seconds with SD of 11.23 was reasonably quick. No significant complication like oro- pharyngeal trauma or extreme pressor response to laryngoscopy was noticed. To conclude, Truview evo2 proved to be a better tool than conventional laryngoscope in anticipated difficult situations.
PMCID: PMC2900100  PMID: 20640117
Difficult airway; Truview laryngoscope; Macintosh laryngoscope
23.  A prospective study of physician pre-hospital anaesthesia in trauma patients: oesophageal intubation, gross airway contamination and the ‘quick look’ airway assessment 
BMC Anesthesiology  2013;13:21.
In trauma patients intubated in a physician-led pre-hospital trauma service we prospectively examined the rate of misplaced tracheal tubes, the presence and nature of gross airway contamination, and the value of ‘quick look’ airway assessment to identify patients with subsequent difficult laryngoscopy.
Patients requiring pre-hospital intubation in a 16 month period were included. Intubation success rate, misplaced tracheal tube rate, Cormack and Lehane grade, and the presence and nature of gross airway contamination were recorded at laryngoscopy. Tube placement was verified with carbon dioxide detection and chest x-ray. After visual assessment physicians stated whether laryngoscopy was expected to be a straightforward or ‘difficult’. The assessment was compared to subsequent laryngoscopy grade.
400 patients had attempted intubation and 399 were successfully intubated. 42 were in cardiac arrest and intubated without drugs. There were no oesophageal or misplaced tracheal tubes. Gross airway contamination was reported in 177 of 400 patients (44%), of which ¾ was from the upper airway. Unconscious patients had higher contamination rates (57%) than conscious patients (34%) (p ≤ 0.0001). As a test of difficult intubation, the ‘quick look’ generated sensitivity 0.597 and specificity 0.763 (PPV and NPV were 0.336 and 0.904 respectively).
This study suggests that when physicians perform pre-hospital anaesthesia they have high intubation success rates and the use of ETCO2 monitoring reduces or eliminates undetected misplaced tracheal tubes. We found high rates of airway contamination; mostly blood from the upper airway. The ‘quick look’ airway assessment had some utility but is unreliable in isolation.
PMCID: PMC3848683  PMID: 24024531
Tracheal intubation; Airway; Pre-hospital; Anaesthesia
24.  Routine intubation in the prone position 
Upsala Journal of Medical Sciences  2012;117(4):411-414.
Tracheal intubation in the prone position has previously been reported only as a necessity in a very few emergency situations. It emerged at our clinic as a routine after invention of a test aimed at pinpointing a painful motion segment in patients with chronic low back pain who were candidates for lumbar fusion operation.
Material and methods.
During a 6-year period 247 consecutive patients were treated at our clinic, 91 men and 156 women, mean age 42.8 years, range 25.3–62.8. Classification of the pharyngeal structures according to Mallampati et al. was done the day before surgery, and grading of visualization of the glottis as described by Cormack and Lehane was done during intubation, with the aim of revealing factors of importance for the possibility of performing tracheal intubation in the prone position.
The large majority of patients classified preoperatively as Mallampati class 1 had Cormack and Lehane grade 1 at laryngoscopy, although some patients had grades 2, 3, and 4. Most problems with intubation in the prone position were anticipated among those classified preoperatively as Mallampati class 3, but tracheal intubation in the prone position was still possible in 21 of the 23 patients in this group. In all, tracheal intubation in the prone position was successful in 244 of the 247 patients (98.8%).
Routine tracheal intubation in the prone position can be performed effectively by experienced anaesthesiologists, but this requires continuous training and good support from the anaesthesiology staff.
PMCID: PMC3497215  PMID: 22574748
Anaesthesia; endotracheal intubation; laryngoscopy; pharyngeal anatomy; prone position
25.  A comparison of Truview EVO2 laryngoscope with Macintosh laryngoscope in routine airway management: A randomized crossover clinical trial 
Saudi Journal of Anaesthesia  2013;7(3):244-248.
The Truview EVO2 blade facilitates the view of vocal cords by indirect laryngoscopy and does not require the proper alignment of the oral, pharyngeal and tracheal axes as with the Macintosh blade.
In a crossover fashion, we prospectively compared the view obtained at laryngoscopy with Truview EVO2 and the Macintosh blade in 110 adult patients of either sex between the age of 18 and 60 years, who were scheduled to undergo general anesthesia with endotracheal intubation. The patients were intubated with the second laryngoscope. The preoperative airway variables, laryngoscopic view, difficulty of intubation scale (IDS) score, duration of intubation, and degree of difficulty percentage of glottic opening (POGO score) of use with each laryngoscope were compared.
The IDS score was low and comparable between the two laryngoscopes. The laryngeal view was easy; Modified Cormack Lehane (MCL) grade 2a or less in 98.14% of the cases with the Truview laryngoscope compared to 78.7% of the cases with the Macintosh laryngoscope. Nineteen patients of MCL grade 3, one patient of grade 2b, and seven patients of grade 2a view with the Macintosh laryngoscope had MCL grade 1 view with the Truview laryngoscope. The duration of intubation was comparable between Truview and Macintosh laryngoscopes (12.1±3.8 s vs. 10.9±2.1 s).
Truview laryngoscope performed comparably to Macintosh laryngoscope in patients with normal airway; however, the Truview laryngoscope may be a better option in difficult airway situations when the Macintosh blade fails to show the glottic opening.
PMCID: PMC3757794  PMID: 24015124
Difficult airway; intubation difficulty scale score; laryngoscopic view; Macintosh laryngoscope; Truview EVO2

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