Predictive values of the modified Mallampati test, upper lip bite test, thyromental distance and ratio of height to thyromental distance to predict difficult laryngoscopy in pediatric elective surgical patients 5-12 years old at selected Addis Ababa governmental hospitals, Ethiopia: a multicenter cross-sectional study.

BACKGROUND: Maintaining patent airways is vital in pediatric anesthetic management. Failure to manage and anticipate difficult laryngoscopy (DL) preoperatively is the leading cause of morbidity and mortality. Data on the predictive values of screening parameters in predicting DL are limited in children. Therefore, this study aimed to assess the predictive value of the modified Mallampati test (MMT), upper lip bite test (ULBT), thyromental distance (TMD), and ratio of height to thyromental distance (RHTMD) in predicting DL in children aged 5-12 years at selected Addis Ababa governmental hospitals in Ethiopia. METHODS: A multicenter cross-sectional study was conducted on 141 elective pediatric surgical patients aged 5 to 12 years selected using a systematic random sampling technique at three governmental hospitals from December 1, 2021, to April 30, 2022. The collected data were entered and analysed by SPSS version 26. Chi-square and Fisher's exact tests were used to compare categorical variables. The receiver operating characteristic curve analysis was used to compare the accuracy of MMT, ULBT, TMD, and RHTMD against DL. A P value < 0.05 was considered statistically significant. RESULTS: The magnitude of DL was 15.6%. MMT has the highest sensitivity (86.4%), specificity (91.6%), and negative predictive value (NPV) (97.3%) compared to other tests. The ULBT also has a high sensitivity (72.7%) and specificity (84%) with comparable diagnostic accuracy (90.8%) with the MMT (P < 0.05). The sensitivity, specificity, positive predictive value (PPV), NPV, and accuracy of TMD were 63.6%, 95.8%, 73.7%, 93.4%, and 82.2%, respectively. The RHTMD has the lowest specificity (63.6%), PPV (22.5%), NPV (91.4%), and accuracy (56.7%) in predicting DL. CONCLUSION: The MMT and ULBT are good screening tests, followed by the TMD in predicting DL, while the RHTMD was the least accurate predictor. Because no single test has 100% predictive value, a combination of screening tests is advised in pediatrics for predicting DL.

Ratio of height to thyromental distance: a comparison with mallampati and upper lip bite test for predicting difficult intubation in Pakistani population.

OBJECTIVE: To compare the accuracy of three diagnostic tests in predicting difficult laryngoscopy using Cormack and Lehane grade as the gold standard. METHODS: The cross-sectional study was conducted at the Aga Khan University Hospital, Karachi, from August 2014 to August 2015, and comprised patients who required endotracheal intubation for elective surgical procedures. The primary investigator used ratio of height to thyromental distance, upper lip bite test and the modified Mallampati test for assessing the airway correlated with laryngoscopic view based on Cormack and Lehane grading. Data was analysed using SPSS 19. RESULTS: Of the 383 patients, 59(15.4%) were classified as difficult cases of laryngoscopy. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of ratio of height to thyromental distance were 84.7%, 90.1%, 60.9%, 97%, 89.3%; and those the corresponding values for the upper lip bite test were 83.1%, 89.2%, 58.3%, 96.7% and 88.3%. The values for the modified Mallampati test were 30.5%, 84.3%, 26.1%, 86.9% and 79.9% respectively. The area under receiver-operating characteristic curve for the first two tests was significantly more than for the modified Mallampati test (p<0.01). CONCLUSIONS: RHTMD and ULBT both are acceptable alternatives for prediction of difficult laryngoscopy as a simple, single bed-side test.

PREDICTION OF DIFFICULT INTUBATION BY USING UPPER LIP BITE, THYROMENTAL DISTANCE AND MALLAMPATI SCORE IN COMPARISON TO CORMACK AND LEHANE CLASSIFICATION SYSTEM

OBJECTIVE: To evaluate efficacy of Modified Mallampati test (MMT), upper lip bite test (ULBT) and Thyromental distance (TMD) or combination of two method Modified Mallampati test (MMT)+ upper lip bite test (ULBT), Thyromental distance (TMD) + upper lip bite test (ULBT) in prediction of difficult intubation in patients undergoing GA. PATIENTS AND METHODS: Three tests were carried out in all patients by a single anesthesiologist. These were MMT, ULBT and TMD. Laryngoscopy was performed with patient's head in the sniffing position. The laryngoscopy view was graded according to modified Cormack and Lehane classification system. Study was prospective, single cross sectional, in 151 adult patients who required GA with endotracheal intubation for elective surgery. On arrival in the operating room, routine monitoring and venous cannula were introduced. Midazolam, Fentanyl. and rocuronium, ketamine , propofol were given to facilitate endotracheal intubation. RESULTS: Out of 150 assessed patients, 18 (12%) had difficult intubation. Of those 18 patients, 17 (83.33%) patients had Cormack and Lehane classification III and one patient (16.67%) had classification IV. Compared with Cormack and Lehane classification system as the gold standard for difficult intubation, the sensitivity and specificity of MMT was 66.67% and 96.97% respectively, while ULBT had a sensitivity of 77.78% and a specificity of 93.18%, and TMD had a sensitivity of 55.56% and specificity of 94.97% respectively. A combination of different tests improved their efficiencies. The sensitivity and specificity MMT and TMD combinations was 77.78% and 92.42% respectively, while it was 88.89% and 93.18%, respectively for MMT and ULPT. The combination of TMD and ULBT has a sensitivity of 88.33% and a specificity of 91.67%. CONCLUSION: Upper lip biting test has the best sensitivity while MMT had the best specificity. No single test alone can be reliable for predicting of difficult intubation. The combination of ULBT and MMT was the best in terms of both sensitivity and specificity for prediction of difficult intubation.

Ratio of height-to-thyromental distance and ratio of height-to-sternomental distance as predictors of laryngoscopic grade in children.

BACKGROUND AND AIMS: Failure to secure the airway is an important cause of morbidity and mortality in children. Children are often uncooperative for routine examination and pose problems for obtaining external measurements. We aimed to evaluate ratio of height-to-thyromental distance (RHTMD) and ratio of height-to-sternomental distance (RHSMD) as predictors of laryngoscopic grade in children aged 1-12 years. MATERIAL AND METHODS: This study was an observational study conducted in children aged between 1 and 12 years scheduled for elective surgery under general anesthesia. Children unable to stand, having limited mouth opening/neck mobility, cleft palate or with midline neck masses were excluded. Weight, height, and thyromental and sternomental distances were measured preoperatively. Following induction of anesthesia and full-muscle relaxation, laryngoscopy was performed and Cormack-Lehane view with Cook's modification was noted. Receiver operating characteristic (ROC) curve analysis using RHTMD and RHSMD was performed for predicting poor laryngoscopic view. RESULTS: A total of 138 children with mean age of 6.6 ± 3.4, RHTMD of 17.7 ± 2.1, and RHSMD of 10.0 ± 1.0 were included. No Grade 3 or 4 laryngoscopic views were obtained. ROC curve analysis was done for predicting 2b view (restricted), incidence of which was 10.1%. RHTMD was a better predictor of 2b laryngoscopic view with an area under curve (AUC) of 0.792 compared to RHSMD (AUC = 0.463). CONCLUSIONS: In children aged 1-12 years, RHTMD is a better predictor of restricted view compared to RHSMD.

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.

Comparison of upper lip bite test and ratio of height to thyromental distance with other airway assessment tests for predicting difficult endotracheal intubation.

BACKGROUND: Various anatomical measurements and noninvasive clinical tests, singly or in various combinations can be performed to predict difficult intubation. Upper lip bite test (ULBT) and ratio of height to thyromental distance (RHTMD) are claimed to have high predictability. Hence, we have conducted this study to compare the predictive value of ULBT and RHTMD with the following parameters: Mallampati grading, inter-incisor gap, thyromental distance, sternomental distance, head and neck movements, and horizontal length of mandible for predicting difficult intubation. MATERIALS AND METHODS: In this single blinded, prospective, observational study involving 170 adult patients of either sex belonging to American Society of Anesthesiologists physical Status I-III scheduled to undergo general anesthesia were recruited. All patients were subjected to the preoperative airway assessment and, the above parameters were recorded correlated with Cormack and Lehane grade and analyzed. The number of intubation attempts and use of intubation aids were also noted. RESULTS: ULBT and RHTMD had highest sensitivity (96.64%, 90.72%), specificity (82.35%, 80.39%), positive predictive value (92.74%, 91.53%), and negative predictive value (91.3%, 78.8%), respectively, compared to other parameters. While odds ratio and likelihood ratio >1 for all the tests. CONCLUSION: ULBT can be used as a simple bedside screening test for prediction of difficult intubation, but it should be combined with other airway assessment tests for better airway predictability. RHTMD can also be used as an acceptable alternative.

Evaluation of upper airway ultrasonographic measurements in predicting difficult intubation: A cross-section of the Turkish population.

Objectives: Studies have shown that there are differences in clinical evaluation parameters and difficult intubation rates among different ethnic populations. In our study, we aimed to evaluate the efficacy of upper airway clinical and ultrasonographic measurement methods in Turkish population. Methods: Our study is a single-center, prospective, observational study conducted with 402 patients. All patients underwent clinical airway measurements which are routinely used in pre-anesthetic evaluation. In addition, ultrasonographic anterior neck soft tissue thickness measurements of each patient were made and recorded. Results: Among the clinical measurements, we found the neck circumference/thyromental distance (TMD) ratio to be significant with a cut-off value of 5.5 and a sensitivity of 92.9% and a specificity of 88.3%, while among the ultrasonographic anterior neck measurements, we found the skin-epiglottic distance to be the most sensitive measurement. We found that there was a positive relationship between the neck circumference/TMD ratio and skin-epiglottis. Conclusions: In our study, we found that routine measurement methods used in airway examination alone are not sufficient, and measurements that take into account the body proportions of the patients, such as the neck circumference/TMD ratio and the ultrasonographic evaluations are more useful in predicting difficult intubation.

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.

BACKGROUND: 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. RESULTS: 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. CONCLUSIONS: ULBT is the best predictive test for difficult laryngoscopy in apparently normal patients but RHTMD can also be used as an acceptable alternative.

Evaluation of neck-circumference- thyromental- distance ratio as a predictor of difficult intubation: A prospective, observational study.

Background and Aims: Preoperative identification of difficult airway and subsequent planning is of utmost importance for a patient's safety. Previous studies have identified the ratio of the neck circumference (NC) to the thyromental distance (TMD); NC/TMD as a reliable predictor of difficult intubation in obese patients. But there is a lack of studies evaluating the NC/TMD in non-obese patients. Therefore, the aim of this study was to compare the NC/TMD as a predictor of difficult intubation in both obese and non-obese patients. Methods: A prospective, observational study was conducted after obtaining institutional ethics committee clearance and written and informed consent from each patient. One hundred adult patients undergoing elective surgeries under general anaesthesia with orotracheal intubation were included in this study. Difficulty in intubation was assessed using the Intubation Difficulty Scale. The NC/TMD was calculated and the predictive accuracy of NC/TMD and other established parameters in obese and non-obese patients were compared. Results: Univariate logistic regression analysis showed that gender, weight, body mass index, inter-incisor gap, Mallampati classification, NC, TMD, sternomental distance, and NC/TMD had a significant association with difficult intubation. NC/TMD has a higher sensitivity, specificity, and positive and negative predictive value with better predictability in comparison to other parameters. Conclusion: The NC/TMD is a reliable and better predictor of difficult intubation in both obese and non-obese patients in comparison to NC, TMD, and sternomental distance alone.

Assessment of airway parameters in obstetric patients and comparing them at different phases in the perinatal period: A prospective observational study.

Background and Aims: Airway changes occur in different stages of pregnancy. We aimed to evaluate the changes in the upper airway in obstetric patients during pregnancy, labour and after delivery using multiple airway indices and identify the predictive factors of these changes. Methods: This observational study was conducted on 90 parturients aged >20 years, having monofoetal pregnancy. The patient's weight was noted, airway assessment including Mallampati grading (MPG), and thyromental distance (TMD), sternomental distance (SMD), neck circumference (NC) and Wilson's risk score were measured in the second trimester of pregnancy (T0), between 32 and 34 weeks of gestation (T1), at the time of admission for safe confinement, between 38 and 40 weeks of gestation (T2), 2 h after delivery of baby (T3) and, 24 h after delivery (T4). Unpaired t-test and analysis of variance test were applied. Results: Changes in mean (standard deviation [SD]) weight, recorded from T0 to T2, were from 56.96 (10.77) to 65.322 (11.49) kg (P = 0.001). A rise of one or two grades in MPG was detected as the pregnancy progressed, and a decrease of one grade was noted after delivery. A significant decrease in mean (SD) TMD was noted from 6.88 (0.65) to 6.36 (0.62) cm from T0 to T2 (P = 0.001). SMD also decreased in a similar manner as TMD. NC increased from T0 to T3 and then decreased at T4 (P = 0.004). Conclusion: Following the second trimester of pregnancy, MPG increased by either one or two grades, with a decrease in TMD and SMD and an increase in NC.

Predicting difficult intubation: the hyomental distance ultrasound evaluation is superior to the thyromental distance.

BACKGROUND: Hyomental distance (HMD), an anatomical feature of the upper airway, can be measured precisely by ultrasonography. But the sensitivity and specificity of HMD compared to thyromental distance (TMD) to predict difficult airways is still unknown. METHODS: A case-cohort study was conducted. The written informed consent was obtained. Elective surgery adult patients undergoing general anaesthesia and tracheal intubation were recruited. The other inclusion criteria were: no maxillofacial deformity, trauma, airway stenosis, known difficult airway. The exclusion criteria were: tracheal intubations or operations were canceled, or patients' data were missing. HMD ultrasound measurements of patients in a sniffing position and other usual airway evaluations were performed before general anaesthesia induction. The primary outcome was the intubation difficulty level. Predictive values were calculated. RESULTS: We successfully enrolled 2357 patients (62 difficult intubation patients) in the cohort study for analysis. The area under the receiver operating characteristic curve (AUC) of the HMD and TMD for predicting difficult intubation was 0.86 (95% CI, 0.84-0.87) and 0.77 (95% CI, 0.75-0.78) respectively (comparison: P < 0.001). With an optimal cut-off value of HMD ≤ 4.9 cm, we observed a sensitivity and specificity of 0.90 (95% CI, 0.80-0.96) and 0.73 (95% CI, 0.71-0.75). Meanwhile, with TMD ≤ 7.0 cm, the sensitivity and specificity were 0.77 (95% CI, 0.65-0.87) and 0.65 (95% CI, 0.63-0.67) respectively. CONCLUSION: In comparison to TMD, HMD measured by ultrasound was more sensitive in predicting difficult intubation.

The Ratio of Height to Thyromental Distance (RHTMD) and Height to Sternomental Distance (RHSMD) as the Predictive Tests for Difficult Tracheal Intubation.

BACKGROUND: Pre-operative evaluation is a cornerstone in identifying patients with a risk of difficulty in intubation. Thyromental distance (TMD) is the most commonly used predictor of difficult intubation. However, it's not a reliable indicator of difficulty during intubation because it differs with patients' body & size proportion. The present study was done for the evaluation of the ratio of height to thyromental distance (RHTMD) and ratio of height to sternomental distance (RHSMD) as difficult airway predictors.  Methods: Data was taken from 400 consecutive patients posted for the need for anesthesia with intubation during surgery. Preoperatively examination of RHTMD and RHSMD was done. Difficulty during intubation has been explained in this current study with Cormack and Lehane grade 3 or 4. The positive and negative predictive values, as well as sensitivity and specificity of individual tests, were calculated as per the recognized formula. RESULTS: The study enrolled 400 patients, which include a maximum number of participants (138 [34.5%]) from the 41-50 year age group. On analyzing RHTMD and RHSMD, the former was found to have a better predictive value than RHSMD (p=0.001). RHTMD & RHSMD was found to have 62.5% & 37.50% sensitivity, respectively. RHTMD was found to have better specificity, positive & negative predictive values, and accuracy than RHSMD. CONCLUSION: RHTMD was observed to have superior precision in anticipating difficulty in intubation compared to RHSMD.

Evaluation of various anthropometric airway parameters as predictors of difficult airway in neonates: A prospective observational study.

OBJECTIVE: To determine the relationship between various anthropometric parameters (age, weight, neck circumference, head circumference, thyromental distance, sternomental distance, frontal plane to chin distance, and frontal plane to chin distance by weight ratio) in neonates with difficult laryngoscopy and difficult intubation. DESIGN: A Prospective, double-blind, observational study. SETTING: Conducted in a Tertiary care Hospital in India. The study was conducted over a period of one year. PATIENTS: Participants included 100 neonates undergoing either elective or emergency non-cardiac surgery under general anesthesia. INTERVENTIONS: The various anthropometric parameters were correlated with Difficult laryngoscopy (Cormack Lehane grading III, IV) and Difficult intubation (Intubation Difficulty score>5). MEASUREMENTS: Difficult laryngoscopy (Cormack lehane grade III, IV) and Difficult intubation (Intubation Difficulty score >5). MAIN RESULTS: We found a statistically significant difference between weight (2.5 (2.2-2.8) kg vs 1.9 (1.55-2.35) kg), (p = 0.006), TMD (3.03 (2.74-3.46) cm vs 2.70 (2.45-3.13) cm), (p = 0.029), SMD (5.18 (5.06-5.76) cm vs 5.02 (4.84-5.29) cm), (p = 0.020) and FPCD/Wt ratio (0.31 (0.27-0.36) vs 0.44 (0.37-0.44)) with p = 0.001 in neonates with Easy and Difficult laryngoscopy. Using ROC curve analysis we calculated AUC, optimal cut off value, sensitivity, specificity, PPV and NPV for weight, TMD, SMD and FPCD/Wt ratio and found FPCD/Wt ratio to be best predictor for difficult laryngoscopy with highest AUC (0.844), high sensitivity (77.78%) and NPV (97.44%). CONCLUSIONS: No single parameter can provide a high index of sensitivity and specificity to predict difficult airway in neonates. Therefore, a combination of tests, including Weight, TMD, SMD, and FPCD/Wt ratio, should be used. To the best of our knowledge, this is the first prospective study to assess predictors to the difficult airway in neonates.

Evaluation of different airway tests to determine difficult intubation in apparently normal adult patients: undergoing surgical procedures.

BACKGROUND: Inadequate maintenance of a patient's airway represents a major cause of anesthesia-related morbidity and mortality. This study was designed to evaluate common preoperative clinical tests to determine the risk of difficult endotracheal intubation in apparent "normal" adult patients undergoing surgical procedures. METHODS: A prospective observational cohort study was performed on 160 consecutive adult patients undergoing surgical procedures at an academic medical center in Jordan from 20 May 2019 until 11 February 2020. Preoperative assessment of airway risk stratification was performed by the following clinical tests: the mandible protrusion test (MPT), thyromental (TMD) and sternomental (SMD) distances, inter-incisor gap (IIG), and the modified Mallampati tests with tongue protrusion (MMT-TP) and without tongue protrusion (MMT-NTP). Grade C on the MPT, TMD ≤ 6 cm, SMD ≤ 12 cm, and MMT grades III and IV were considered to be predictors of difficult endotracheal intubations. A modified Cormack-Lehane grading (MCLG) of laryngoscopic views with backward, upward, and right-sided pressure on the thyroid and cricoid cartilages (BURP) maneuver was also documented, with grades 2B, 3, and 4 considered to be difficult airways for intubation. RESULTS: Fifteen patients (9.4%) were classified as MCLG 2B, 3, and 4, with age significantly associated with the MCLG grade (P = 0.028). The sensitivity and Youden's index of MMT-TP were found to be the lowest (40% and 0.29, respectively). The MPT was the most accurate and specific test (90.63 and 95.17%, respectively), with the highest PPV (50%), Youden's index (0.42), and area under the curve (AUC) (0.781). Bivariant analysis of MPT and the t-test of the mean TMDs and SMDs revealed significant associations between these airway tests and the difficulty of intubation (P values: < 0.001, 0.02, < 0.01, respectively). CONCLUSION: The MPT, with its highest accuracy, specificity, positive predictive value, and good sensitivity may be used as a routine screening test for preoperative prediction of difficult endotracheal intubations.

Validity of thyromental height test as a predictor of difficult laryngoscopy: A prospective evaluation comparing modified Mallampati score, interincisor gap, thyromental distance, neck circumference, and neck extension.

BACKGROUND AND AIMS: Thyromental height test (TMHT) is a recently described anatomical bedside screening tool in predicting difficult laryngoscopy. It has been shown to be more accurate than the modified Mallampati score, thyromental distance (TMD), and sternomental distance with regard to sensitivity and positive predictive value (PPV). Airway assessment studies based on the anatomic parameters of the upper airway are limited in the subcontinent population. We attempted this study to evaluate and validate the predictive value of TMHT at 50 mm in an Indian population in predicting difficult laryngoscopy. METHODS: This prospective observational study was conducted in a tertiary teaching hospital on 340 patients. TMHT along with other bedside predictors of difficult intubation, including modified Mallampati score, interincisor gap (IIG), TMD, neck circumference (NC), and neck extension were assessed. We compared the sensitivity, specificity, PPV, negative predictive value (NPV), and diagnostic accuracy of TMHT with other bedside tests such as the modified Mallampati score, IIG, TMD, NC, and neck extension individually in predicting difficult laryngoscopy. Any Cormack and Lehane's intubation grade II b and above was considered to be difficult laryngoscopy. RESULTS: TMHT had the highest sensitivity (84.62%) and specificity (98.97%), and had the most PPV (88%) and NPV (98.63%) when compared with the modified Mallampati score, IIG, TMD, NC, and neck extension. TMHT was followed by the modified Mallampati score and IIG. CONCLUSION: TMHT appears promising as a single anatomical measure to predict the risk of difficult laryngoscopy, however, validation will require further studies in more diverse patient populations.

Comparison of Upper Lip Bite Test and Ratio of Height to Thyromental Distance with Other Airway Assessment Tests for Predicting Difficult Endotracheal Intubation.

BACKGROUND AND AIMS: Unanticipated difficult intubation or the failed intubation in operating room and in emergency department is an imperative source of anesthesia-related patient's mortality. The aim of this study is to compare the predictive value of upper lip bite test (ULBT) and ratio of height to thyromental distance (RHTMD) with other commonly used preoperative airway assessment tests for predicting difficult intubation in Indian population. MATERIALS AND METHODS: In this prospective, single-blinded observational study, 260 adult patients of either sex, belonging to American Society of Anesthesiologists physical Status I and II undergoing elective surgical procedure under general anesthesia were included in the study. ULBT, RHTMD, inter-incisor gap, modified Mallampati grade, horizontal length of the mandible, head and neck movements, sternomental distance, and TMD were assessed preoperatively and correlated with Cormack and Lehane's grading during laryngoscopy under anesthesia. Statistical analysis was done by Chi-square and Fisher's exact test. RESULTS: ULBT and RHTMD had highest sensitivity (66.7% and 63.3%), specificity (99.1% and 89.6%), positive predictive value (90.9% and 44.2%), and negative predictive value (96.9% and 95.0%), respectively, when compared to other parameters in predicting difficult airway. CONCLUSION: ULBT and RHTMD may be used as a simple bedside airway assessment tools for prediction of difficult intubation.

Ethnicity and upper airway measurements: A study in South Indian population.

BACKGROUND AND AIMS: Most studies on upper airway are conducted based on airway measurements in the western population. We set out to find the normal values of upper airway measurements in South Indian population. The aim of this study was to perform various upper airway examinations and to set standards for normal measurements in the South Indian population as well as to analyse the data for predictors of difficult intubation. METHODS: This prospective observational study was conducted in a tertiary cancer hospital in Southern India. Airway assessment parameters, including modified Mallampati classification (MPC), upper lip bite test (ULBT), sternomental distance, thyromental distance (TMD), and the inter-incisor distance were documented for 2004 patients meeting the inclusion criteria. Laryngoscopic view after induction was graded as per Cormack and Lehane's (CL) classification. Any CL ≥3 was considered to be difficult laryngoscopy. The collected data (2004 cases) was analyed with SPSS software version 17. Receiver operating characteristics (ROC) curve was used to determine cut-offs in the population. Sensitivity, specificity, positive and negative predictive value were computed. RESULTS: MPC, ULBT, and ratio of height to TMD (RHTMD) predicted difficult intubation with sensitivity of 40.86%, 45.53% and 64.60%, respectively and these were statistically significant with P < 0.001. Using the area under the curve of the ROC curve and discrimination analysis normal RHTMD in our population had a cut off value of 17.1. CONCLUSION: The cut off value for RHTMD to predict difficult laryngoscopy in the South Indian population is 17.1.

Correlation between changes in thyromental distance and distance of migration of oral Ring-Adair-Elwyn tubes during neck extension with a shoulder positioner in patients undergoing neck procedures.

OBJECTIVES: To measure the migration of oral Ring-Adair-Elwyn (RAE) preformed tracheal tubes during neck extension compared with the neutral neck position, and to assess the correlation between changes in the thyromental distance (TMD) during changes in neck position and tracheal tube migration. METHODS: This prospective observational study enrolled adult patients undergoing elective neck or thyroid procedures below the mandible. Using fibreoptic bronchoscopy, distances from the RAE tube adapter to the carina and to the tube tip were measured in the neutral position and after neck extension with a 10 cm D-shaped gel shoulder positioner. The change in distance of the RAE tube tip migration was compared with the change in TMD in each patient. RESULTS: This study enrolled 106 patients. During neck extension with a 10-cm shoulder positioner, RAE tubes cranially migrated 2.7 cm from the neutral position, but RAE tube migration was not correlated with the change in external TMD. CONCLUSION: Oral RAE tube migration was not significantly correlated with the change in external TMD. Due to their large variability, changes in TMD were not useful predictors of RAE tube migration.

Prediction of ease of laryngoscopy and intubation-role of upper lip bite test, modified mallampati classification, and thyromental distance in various combination.

BACKGROUND: The incidence of difficult intubation in patients undergoing general anaesthesia is estimated to be approximately 1-18% whereas that of failure to intubate is 0.05-0.35%.1,2,3 Various methods have been used for prediction of difficult laryngoscopy. Although, upper lip bite has been shown to be a promising test in its introductory article, repeated validation in various populations is required for any test to be accepted as a routine test. We have compared upper lip bite test (ULBT), modified Mallampati test (MMC) and thyromental distance (TMD) individually and in various combinations to verify which of these predictor tests are significantly associated with difficult glottic exposure. METHODS: After obtaining institutional ethics committee approval, 402 ASA I and II adult patients undergoing elective surgical procedures requiring endotracheal intubation were included. All the three test were performed in all the patients preoperatively and their glottic exposure was recorded by Cormack-Lehane classification during intubation. Sensitivity, specificity, positive predictive value and negative predictive value were used for comparison. RESULTS: In our study, the incidence of difficult laryngoscopy was 11.4% and failure to intubate 0.49%. None of the three are a suitable predictive test when used alone. Combination of tests added incremental diagnostic value. CONCLUSION: We conclude that all three screening tests for difficult intubation have only poor to moderate discriminative power when used alone. Combinations of individual tests add some incremental diagnostic value.