A comparative study between tongue thickness measured by ultrasonography and thyromental distance in anticipation of difficult intubation

Diagnostic Efficacy and Clinical Value of Ultrasonography in Difficult Airway Assessment: Based on a Prospective Cohort Study.

Airway Assessment is essential in pre anesthetic assessment. Anticipating and preparing for difficulty in airway management is crucial to avoid airway catastrophes. Routine pre operative airway examination usually includes mouth opening and dentition, Mallampati classification, thyromental distance and neck movements. Neck circumference is a quick bedside test to determine difficult laryngoscopy. Increased tongue thickness and skin to epiglottis distance affects performance of laryngoscopy and tracheal intubation increasing the risk of difficult airway. Presently there is a search for non-invasive and accurate tools to overcome limitations of clinical airway assessment tests. Ultrasonography has been evolving as a useful device for airway assessment especially soft tissue structures in anterior surface of neck. Here we studied the measurement of neck circumference and ultrasound measurement of tonguethickness and skin to epiglottis distance as predictors for difficult intubation. The Aim of the study is to predict difficulty in intubation by measuring neck circumference, thickness of tongue and thickness of skin to epiglottis. Prospective observational study, 120 patients posted for surgery under general anesthesia, Department of anesthesia, Meenakshi medical college, Kanchipuram. After institutional Human ethical committee clearance, 120 Patients were screened during preoperative assessment for undergoing procedures under general anaesthesia. Neck circumference and other airway parameters were measured with measuring tape and distance between Skin to epiglottis and tongue thickness were measured with ultrasound linear probe. Patients were grouped into Group E( Easy Intubation) whose Cormack-lehane grade was 1 and 2 and Group D ( Difficult intubation) whose Cormack-lehane grade was 3 and 4. SPSS version 16 was used for statistical analysis. There was no statistical significance seen between age, sex, height among easy and difficult intubation but significance was seen with weight (p <0.05), Thyromental distance(p<0.05) and Sterno-mental distance(p<0.05). High significance was seen in Distance between skin to epiglottis distance(p<0.001), Tongue thickness(p<0.001) and Neck Circumference(p<0.001) in difficult intubation cases. Neck circumference and ultrasonographic measurement of tongue thickness and skin to epiglottis can avoid unanticipated difficult intubation.

Predicting difficult intubation--worthwhile exercise or pointless ritual?

Predicting difficult airway and preparedness for the same can help prevent catastrophic situations while handling the airway. With the increasing familiarity of anaesthesiologists to the use of ultrasound machine and its easy availability and non-invasiveness, we sought to study its utility in airway assessment, by measuring the thickness of tongue, to predict difficult laryngoscopy and intubation. A total of 85 patients undergoing elective surgeries under general anaesthesia with endotracheal intubation were examined preoperatively. Tongue thickness was measured using submental ultrasonography in the median sagittal plane along with other tests of airway assessment. Cormack Lehane grade on laryngoscopy and Intubation Difficulty Scale Score was recorded. The sensitivity, specificity, positive and negative predictive value, and accuracy was calculated for tongue thickness for predicting difficult intubation. The tongue thickness in those with difficult intubation (4.83 ± 0.62) was significantly higher than those without difficult intubation (4.38 ± 0.65). The ratio of tongue thickness to thyromental distance was also significantly higher in difficult intubation group. The area under the receiver operating characteristic curve for predicting difficult laryngoscopy and intubation was higher for tongue thickness as compared to other clinical parameters. The sensitivity and specificity of tongue thickness to predict difficult laryngoscopy was 100% and 83%, respectively, and to predict difficult intubation was 72% and 59%, respectively, with an accuracy of 72%. Ultrasound based assessment of tongue thickness can be a useful predictor of difficult airway along with clinical assessment of the airway.

BackgroundGeneral anesthesia is not without morbidity. One of the well-known life-threatening events associated with general anesthesia is difficult airway which can happen during induction of anesthesia while attempting to insert the endotracheal tube with the aid of a laryngoscope. Difficult intubation, inadequate ventilation, and esophageal intubation are the principal causes of death or brain damage related to airway manipulation. ObjectiveThe main objective of this study was to assess the magnitude and predictors for difficult laryngoscopy and intubation among surgical patients who underwent elective surgery under general anesthesia with endotracheal intubation at Tikur Anbessa Specialized Hospital from February 1 to March 30, 2019. Materials &methodAn institutional based cross sectional study was conducted from February 1 to March 30, 2019 on patients who underwent elective surgery under general anesthesia with endotracheal intubation. Data on socio-demographic characteristics, preanesthetic airway assessment and laryngoscopic view were collected. Data were analyzed by SPSS Version 20.0. Chi- square test, binary logistic regression and multivariate analysis were performed. Tables and texts were used to present data. A p value less than 0.05 was considered as statistically significant. ResultsThe magnitude of difficult laryngoscopy, difficult intubation, and failed intubation were 12.2%, 6.1%, and 0.67%, respectively. Upper Lip Bite Test (ULBT) had a higher sensitivity (90.2%) and negative predictive value of 85.3%. Mallampati had a sensitivity of 45.8% and negative predictive value of 86% in predicting difficult laryngoscopy. Mallampati grade, thyromental distance and ratio of height to thyromental distance (HRTMD) have also showed greater sensitivity (69.6%, 58.3% and 47.8%, respectively) when compared to other tests in predicting difficult intubation. Mallampati class, upper lip bite test (ULBT) and inter-incisor distance (IID) are independent predictors for difficult laryngoscopy (p < 0.05). Furthermore, Mallampati class, Thyromental distance and ratio of height to thyromental distance (HRTMD) are identified as independent predictors of difficult intubation (p < 0.001). Conclusionand recommendation: Mallampati class, Thyromental distance and Ratio of height to Thyromental distance (HRTMD) can predict the probability of difficult endotracheal intubation in adult patients. Whereas, Mallampati class and upper lip bite test (ULBT) predicts higher probability for difficult laryngoscopy.

BACKGROUND: Unanticipated difficult tracheal intubation is a significant source of morbidity and mortality in anaesthetic practice which can be reduced by identification of potential difficult intubation. OBJECTIVE: We aimed the present study to know the incidence of difficult intubation, factors associated with it and the predictive value of various airway predictors in anticipating difficult visualization of larynx and difficult intubation. METHODS: 435 adult patients (>18 year) undergoing general anaesthesia with intubation were examined preoperatively for demographic details (age, sex, weight), dentition, airway pathology and six airway predictors i.e. Inter Incisor Gap (IIG), Modified Mallampatti Grading (MMPG), Upper lip bite test (ULBT), Thyromental distance (TMD), Sternomental distance (SMD) and subluxation of mandible (SLM). All patients were anaesthetized using standard protocol with thiopentone (5mg/kg) and succinylcholine (1.5 mg/kg). On direct laryngoscopy, Cormack Lehane (CL) grading was noted. CL grade I, II was defined as easy visualization of larynx (EVL) and CL grade III, IV as difficult visualization of larynx (DVL). Difficult intubation score (DIS) was calculated as sum of CL grade and number of intubation attempts. DIS of less than or equal to 4 was defined as easy intubation (EI) and DIS > 4 was defined as difficult intubation (DI).Sensitivity, specificity, positive and negative predictive value, positive and negative likelihood ratios(LR) and odd's ratio value for six airway predictor tests was calculated by standard formulae. RESULTS: Incidence of DVL was 12.65% (n=55) and DI was 9.65% (n=42), with no failed intubation. All airway tests had very high negative predictive value (>90%) which implicates they identify easy intubations more precisely. MMPG and ULBT were found as airway predictors for difficult intubation having odds ratio of 85.23 (95% CI 25.42- 285.89%) and 65.45 (95% CI 25.69-166.7%) respectively, along with very high sensitivity of 92.80% and 85.7% respectively. Presence of ULBT III is the best predictor of difficult intubation (+LR 21.97) and absence of MMPG III, IV is the best predictor of difficult intubation (-LR 0.091). Abnormal dentition and airway pathology also increase the risk of difficult intubation, P<0.001. CONCLUSION: We conclude that ULBT and MMPG are nearly perfect airway predictors and should be used routinely during pre-anesthetic visit for screening of difficult intubation.

BackgroundWe studied the differences in airway assessment factors among old, middle, and young age groups, and evaluated the frequency and causes of difficult intubation among these groups.MethodsPatients were divided into young (< 40 yr, n = 75 ), middle (40-59 yr, n = 83), and old (≥ 60 yr, n = 89) group. Airway assessment factors such as head and neck movement, thyromental distance, interincisor gap, dentition, Mallampati score, and Arné score were assessed. After muscle relaxation, cervical joint rigidity and Cormack-Lehane (C-L) grade were assessed. The differences in airway assessment factors between difficult (C-L grade 3, 4) and easy (C-L grade 1, 2) intubation were then examined. Logistic regression analysis was also carried out to identify the extent to which airway assessment factors reflected difficult intubation.ResultsAs aging, head and neck movement, thyromental distance, and interincisor gap decreased, the grade of dentition, Mallampati score, cervical joint rigidity and the ratio of Arné score > 11 increased. In the old and middle group, the incidence of difficult intubation was increased compared with the young group. Dentition in the young group, Mallampati score and interinsisor gap in the middle group and Mallampati score, cervical joint rigidity in the old group respectively predicted difficult intubation.ConclusionsCompared to young individuals, middle-aged or elderly adults are likely to experience more difficulty in endotracheal intubation and its predictive factors could vary by age group.

To the Editor: Even though several previous studies have questioned and challenged its relevancy as a predictor (1–5), thyromental distance (TMD) is still widely used in almost every airway study to date. In our view, TMD is a tenacious misconception that has contributed to the present confusion and frustration in understanding and predicting difficult intubation (6). For example, although El-Ganzouri et al. (7) did not discuss TMD directly in their 1996 multivariate risk index study, their data showed TMD correctly predicted only 7% of all difficult intubation cases (93% false negative). In a recent study by Brodsky et al. (8) on morbid obesity and tracheal intubation, TMD was found to be no different between easy and difficult (problematic) intubations. In one patient with failed direct laryngoscopy, the TMD was 14 cm long. A MacIntosh No. 4 blade revealed a Grade 3 view. Taken together with previous literature (1–5) and findings presented in El-Ganzouri and Brodsky et al.’s studies (7,8), we suggest that TMD falls short as a useful predictor because measuring TMD is fundamentally an incorrect approach. Measurement of TMD originated as a quantitative assessment of “receding jaw,” yet we have found no correlation between receding jaw and the mechanism of difficult laryngoscopy (9). We have previously shown that in patients with a caudally positioned larynx, the mandibulohyoid distance (MHD) is long and the tongue is largely contained in the hypopharynx, causing difficult ventilation, difficult intubation, or sleep apnea (10). Although MHD is measured vertically and TMD obliquely, patients who have a long MHD/caudal larynx/large hypopharyngeal tongue will also have a long TMD. These patients are candidates for difficult intubation, yet their long TMDs will indicate easy intubation. Such cases may account for the large false negatives associated with the use of TMD in prediction. Another confusing concept is the “anterior larynx” often used to describe patients with difficult intubation. We believe the term “anterior larynx” is a misnomer. For instance, in a laryngoscopy Grade 3 patient, we may try with effort to lift up the tongue with the blade, yet only the epiglottis can be seen. At such time, the deeper, unreachable larynx appears situated “anterior” to the line of sight. Thus, while “anterior larynx” may describe the failure to bring the larynx into view, it obscures the real issue of a caudal larynx/large hypopharyngeal tongue that causes difficulties (2,10). Therefore, we propose “caudal larynx” to be the anatomically correct term to indicate the cause of difficult laryngoscopy. Since the 1990 closed claims study (11), difficult airway management has become a top patient safety issue in clinical practice. After more than a decade’s effort, our specialty is now at a crossroads. Perhaps it is time for practitioners to think differently and examine new concepts and insights (2,9,10). Hsiu-chin Chou, MD Tzu-lang Wu, MD

BackgroundAccurate prediction of the difficult airway (DA) could help to prevent catastrophic consequences in emergency resuscitation, intensive care, and general anesthesia. Until now, there is no nomogram prediction model for DA based on ultrasound assessment. In this study, we aimed to develop a predictive model for difficult tracheal intubation (DTI) and difficult laryngoscopy (DL) using nomogram based on ultrasound measurement. We hypothesized that nomogram could utilize multivariate data to predict DTI and DL.MethodsA prospective observational DA study was designed. This study included 2254 patients underwent tracheal intubation. Common and airway ultrasound indicators were used for the prediction, including thyromental distance (TMD), modified Mallampati test (MMT) score, upper lip bite test (ULBT) score temporomandibular joint (TMJ) mobility and tongue thickness (TT). Univariate and the Akaike information criterion (AIC) stepwise logistic regression were used to identify independent predictors of DTI and DL. Nomograms were constructed to predict DL and DTL based on the AIC stepwise analysis results. Receiver operating characteristic (ROC) curves were used to evaluate the accuracy of the nomograms.ResultsAmong the 2254 patients enrolled in this study, 142 (6.30%) patients had DL and 51 (2.26%) patients had DTI. After AIC stepwise analysis, ULBT, MMT, sex, TMJ, age, BMI, TMD, IID, and TT were integrated for DL nomogram; ULBT, TMJ, age, IID, TT were integrated for DTI nomogram. The areas under the ROC curves were 0.933 [95% confidence interval (CI), 0.912–0.954] and 0.974 (95% CI, 0.954–0.995) for DL and DTI, respectively.ConclusionNomograms based on airway ultrasonography could be a reliable tool in predicting DA.Trial registrationChinese Clinical Trial Registry (No. ChiCTR-RCS-14004539), registered on 13th April 2014.

Background: An incidence of difficult intubation in elective surgery is 1.5%–8%. Multiple attempts during tracheal intubation can cause airway injuries bleeding, brain hypoxia, and even cardiac arrest. Unanticipated failure and inability to secure difficult airway can lead to “cannot ventilate, cannot intubate” condition. Preoperative assessment and bedside tests play a vital role in predicting and stratifying risk of difficult intubation. This study was done to determine the incidence of difficult intubation and diagnostic accuracy of different bedside tests for predicting intubation difficulty in patients without airway pathology scheduled for elective surgery under general anesthesia. Materials and Methods: Two hundred patients, aged 20–50 years, American Society of Anaesthesiologists I and II, without airway pathology undergoing elective surgery were evaluated preoperatively using simple bedside tests such as Mallampati grading (MPG), interincisor gap (IIG), thyromental distance (TMD), sternomental distance, upper lip bite test, neck circumference, and atlantooccipital extension to predict difficult intubation. Statistical confirmation was done using Pearson’s chi-square test and univariate and multivariate logistic regression. Results: In our study, the incidence of difficult intubation was observed as 6%. High sensitivity for predicting difficult intubation was seen with IIG &gt; TMD &gt; MPG, and high specificity among the relevant bedside tests was seen with TMD &gt; MPG &gt; IIG. Tests with high positive predictive value were TMD &gt; MPG, whereas high negative predictive value was seen with IIG &gt; TMD &gt;MPG. Conclusion: IIG, TMD, and MPG can be used to predict difficult intubation in patients without airway pathology.

<span>Abstract Unexpected difficult endotracheal intubation remains the main concern of anesthesiologists. This study aimed to compare validity and role of 7 bedside techniques of assessment used in predicting difficult intubation. This prospective study included 80 patients scheduled for surgery. Before induction of anesthesia, bedside tests for predicting difficult intubation were done, these tests are: Prayer sign, Thyromental distance, Mallampati test, The inter incisor distance, Palm print test, Upper lip bite test, and Wilson scoring system. During induction of anesthesia, laryngoscopic view was evaluated. Values for each test were calculated and compared. The results showed that, the highest sensitivity (62.5%) was for Mallampati and thyromental distance but despite that, they differed in their specificity and predictive values. Upper lip bite was 12.5% sensitive but had one of the highest specificity alongside with Mallampati test. Thyromental distance was 34.7% specific. Mallampati classes of more than class I was strongly associated with difficult intubation. The mouth gap of more than 4 cm was marginally associated with difficult intubation. The predictor Wilson showed a significant association with difficult intubation if the score exceeded 3.5. The upper lip bite of more than class I was slightly associated with difficult intubation. In conclusion, Mallampati classification and thyromental distance are superior to other available tests to predict difficult intubation, performing these two tests alone is relatively adequate to predict intubation difficulty. Keywords: Difficult endotracheal intubation, The inter incisor distance, Wilson scoring system, Mallampati test, Palm print test, Prayer sign, Upper lip bite test, and Thyromental distance.</span>

Can tongue thickness measured by ultrasonography predict difficult tracheal intubation?

Aim: Difficult tracheal intubation is a fundamental cause of perioperative morbidity and mortality. The frequency of difficult intubation is thought to be higher in the pediatric age group due to the different anatomical and physiological structures, and it may not be easy to detect this beforehand. Anthropometric measurements were evaluated before the elective operation and the relationship of some parameters with difficult intubation. Material and Method: This prospective cross-sectional study was conducted on 90 pediatric patients aged 2-14 who underwent elective surgery under general anesthesia. All patients’ age, gender, height, weight, body surface area (BSA), and body mass index (BMI) records were recorded before the operation. Mallampati scoring, head and neck circumference, thyromental distance measurements, and head circumference/neck circumference ratio were performed. Cormack-Lehane (CL) scoring and endotracheal intubation were applied during direct laryngoscopy of the operated patients. Children with easy intubation (CL grade 1 and 2) group 1; children who underwent difficult intubation (CL grade 3 and 4) were defined as group 2. Results: There was no significant relationship between Groups I and II in terms of age, height and weight values. There was no significant relationship between the two groups with BSA and thyromental distance measurements. Mallampati scores were found to be grades 3 and 4 (3.3%) in three of the 90 patients, and CL scores of 3 and 4 (4.4%) in four patients. A significant correlation was found between Mallampati scoring and CL scoring. A statistically significant difference was found between the two groups regarding head/neck ratios and BMI. Conclusion: In our study, head circumference/neck circumference ratio and BMI were found to be helpful while predicting difficult intubation in children with normal physical characteristics, 2-14 years of age, who underwent elective surgery. Our findings can be supported by further studies that will be planned and include more patients.

Challenging the Traditional Definition of a Difficult Intubation: What Is Difficult?

Introduction: The prediction of difficult intubation using simple bedside test is of great importance to prevent mismanagement of airway. This study was conducted to compare Upper Lip Bite Test (ULBT) with Modified Mallampati Test (MMT) and Thyromental Distance (TMD) for the prediction of difficult intubation.&#x0D; Method: This was descriptive cross-sectional study conducted in 121 patients of American Society of Anaesthesiologists Physical Status (ASA PS) I and II patients scheduled for elective surgery requiring general anaesthesia with endotracheal tube. The airway assessment of the patients was done one day prior to the surgery using Upper Lip Bite Test (ULBT), Modified Mallampati Test (MMT) and measurement of Thyromental Distance (TMD) . On the day of surgery during laryngoscopy, Cormack-Lehane (CL) grading was recorded. The CL grading of III and IV was labeled as difficult intubation. The Sensitivity, Specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV), Likelihood Ratio (LR) of ULBT, MMT and TMD were calculated and compared.&#x0D; Results: The total percentage of difficult intubation, defined by Cormack-Lehane (CL) III and IV was 16.52 %. The sensitivity, specificity, PPV, NPV and accuracy of Upper Lip Bite Test (ULBT) was 50%, 100%, 100%, 91% and 91.74% respectively. ULBT had a significantly higher sensitivity, specificity and PPV when compared to MMT or TMD or MMT and TMD when combined together.&#x0D; Conclusions: Upper Lip Bite Test (ULBT) is better predictor of difficult intubation and it should be used along with other test during airway assessment.