Comparison of two methods for predicting difficult intubation

Difficult Tracheal Intubation and Airway Outcomes after Radiation for Nasopharyngeal Carcinoma

OBJECTIVE

The aim of the study was to characterize the incidence and management of difficult tracheal intubations (DTIs) in nasopharyngeal carcinoma (NPC) after primary radiation therapy (RT).

METHODS

The study was a retrospective review of airway assessment and outcomes in post-RT NPC patients. Primary analysis was performed on patients who underwent post-RT procedures, who were split into non-DTI and DTI groups. Patients were classified as DTI if they (i) required >1 attempt to intubate, (ii) failed to be intubated, or (iii) experienced complications attributed to airway management. Secondary analysis was performed between patients who underwent post-RT procedures (procedure group) and those who did not (control group).

RESULTS

One-hundred and fifty patients were included, and 71.3% underwent post-RT procedures, with no differences in characteristics between the procedure and control groups. One-hundred and fifty procedures were identified, and 28.0% were categorized as DTI. There was no difference in patient characteristics or airway assessment measures between DTI and non-DTI groups. Regression analysis revealed concurrent cervical mobility restriction, and trismus increased DTI incidence by 7.1-fold (p = 0.011). Being non-White was an independent predictor of DTI. The incidence of high-grade intraoperative laryngoscopic view was lower in the non-DTI compared to the DTI group (20.4% vs. 64.3%, p < 0.0001). Failure to intubate occurred in 2.0% of cases, and 6.0% cases had perioperative complications. Based on preoperative assessment, sensitivity of predicting DTI was 54.8% and specificity was 63.9%.

CONCLUSION

NPC patients frequently undergo post-RT procedures requiring complex airway management. Rates of DTI and failed intubation are significantly higher than those in the general surgical population, and the ability to predict DTI with standard preoperative airway measures is poor.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:120-126, 2024.

A Predictor of Difficult Airway: The Tasli Classification in Transnasal Flexible Laryngoscopy

INTRODUCTION

Difficult airway is defined as difficulty or failure in one or more steps in upper airway management. Evaluation of the upper airway with physical examination methods and endoscopic devices is crucial in predicting difficult airway. The aim of this study was to evaluate bedside tests, Cormack Lehane (CL) and Tasli Classification (TC) scores of the patients and it was aimed to reveal the role of TC which will be performed preoperatively as a predictor of difficult tracheal intubation (DTI).

METHODS

The study included a total of 98 patients who underwent surgical treatment under general anesthesia. Demographic data, including age, gender, and body mass index (BMI), and bedside tests consisting Modified Mallampati Classification (MMC), thyromental (TD) and sternomental (SD) distances, neck circumference (NC), interincisor distance (IID), CL and TC were recorded.

RESULTS

Evaluation was made of 64 (65.3%) male and 34 (34.7%) female patients ranging in age from 18 to 84 years (mean age: 50.35 ± 0.47 years). The successfully intubated patients (SIP)  group comprised 68 (69.4%) patients, and the difficult intubation patients (DIP) group, 30 (30.6%). According to CL, the numbers of SIP and DIP constituting grade 1 was 29 (42.6%) and one (3.3%); grade 2a was 29 (42.6%) and one (3.3%); grade 2b was eight (11.8%) and three (10%); grade 3a was one (1.5%) and six (20%); grade 3b was one (1.5%) and 14 (46.7%) respectively. Grade 4 was only detected in the DIP group in 5 (16.7%) patients. According to TC, the numbers of SIP and DIP constituting grade 1 was 20 (29.4%) and 1 (3.3%); grade 2a was 37 (54.4%) and seven (23.3%); grade 2b was 10 (14.7%) and 18 (60%); grade 3 was one (1.5%) and two (6.7%) respectively. Grade 4 was only detected in the DIP group in two (6.7%) patients.

CONCLUSION

The TC, CL, NC and BMI scores were higher in the DIP group and higher TC scores (grade 2b, 3, and 4) can be a predictor of difficult airway. However, it may be more beneficial to use TC as a complementary diagnostic tool with bedside tests such as NC, SM, TM and MMC, rather than used alone.

Predictive Value of Modified Mallampati Test and Upper Lip Bite Test Concerning Cormack and Lehane's Laryngoscopy Grading in the Anticipation of Difficult Intubation: A Cross-Sectional Study at a Tertiary Care Hospital, Bhubaneswar, India

Background and objective

Many tests are at hand to predict difficult intubation preoperatively to prevent morbidity and mortality of unanticipated difficult intubation. The present study was conducted to evaluate and compare the efficacy of the modified Mallampati test (MMT) and upper lip bite test (ULBT) to foresee difficult intubation.

Materials and methods

After obtaining written informed consent, this prospective comparative observational study was conducted on 225 patients scheduled for elective surgery under general endotracheal anesthesia. Preoperative MMT and ULBT were performed. MMT Grade III, IV, and ULBT Grade IV were regarded as predictors of difficult intubation. The laryngoscopic view was graded as per Cormack and Lehane's laryngoscopic grading after induction of anesthesia by an experienced anesthesiologist ignorant of preoperative airway evaluation. Patients with Cormack and Lehane Class III and IV were regarded as difficult intubation. Sensitivity, specificity, and positive and negative predictive values of MMT and ULBT were computed. Agreement between two tests with the Cormack Lehane test was determined by the Kappa coefficient.

Results

In our research, the occurrence of difficult intubation was found to be 10.2% (23 cases of difficult intubation out of 225 patients). In our analysis, we found the sensitivity (95.5% vs. 95.4%), specificity (54.8% vs 50.0%), positive predictive value (91.6% vs 93.1%), and negative predictive value (39.1% vs 39.1%) were almost comparable between modified Mallampati test and upper lip bite test. Kappa coefficient for the upper lip bite test (0.492) was slightly higher as compared to modified Mallampati scoring (0.454), but both the values are highly statistically significant (p-value <0.001).

Conclusion

Both the upper lip bite test and modified Mallampati test are comparable with each other and since the upper lip bite test is easy to perform bedside test we recommend it to be used alone or in collaboration with other tests in assessing difficult airways.

Diagnostic Accuracy of Combined Mallampati and Wilson Score to Predict Difficult Intubation in Obese Patients: A Descriptive Cross-Sectional Study

Background

Airway protection during anesthesia is often the primary concern of anesthetists when working with obese patients and always is a difficult task due to increased exposure to harmful effects of apnea, hypoxia, and impaired respiratory mechanics.

Objectives

The primary goal of this research was to determine the diagnostic accuracy of combined Mallampati and Wilson score in detecting difficult intubation in obese patients undergoing surgery by taking the Cormack-Lehane grading on direct laryngoscopy and intubation as the gold standard.

Methods

This descriptive cross-sectional study was done in 300 obese patients with BMI > 29.9 kg/m². Modified Mallampati and Wilson score was recorded preoperatively for each patient in the sitting position by the primary investigator. Endotracheal intubation grades were also recorded, and grades IIb, III, and IV were regarded as difficult intubation according to the Cormack-Lehane intubation classification.

Results

The mean age was 46.76 ± 15.57 years. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of the combined Mallampati and Wilson score for detecting difficult laryngoscopy and difficult intubation were 75.0, 98.8, 92.9, 95.0, and 94.6%, respectively.

Conclusions

Combined Mallampatti and Wilson score is highly accurate in the initial diagnostic workup of obese patients at risk of difficult intubation. It is easy to calculate and lower the risk of intubation-related complications and failure.

2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway

The American Society of Anesthesiologists; All India Difficult Airway Association; European Airway Management Society; European Society of Anaesthesiology and Intensive Care; Italian Society of Anesthesiology, Analgesia, Resuscitation and Intensive Care; Learning, Teaching and Investigation Difficult Airway Group; Society for Airway Management; Society for Ambulatory Anesthesia; Society for Head and Neck Anesthesia; Society for Pediatric Anesthesia; Society of Critical Care Anesthesiologists; and the Trauma Anesthesiology Society present an updated report of the Practice Guidelines for Management of the Difficult Airway.

The effect of brief pre-anesthetic exercise therapy of jaw and neck joints on mouth opening, neck extension, and intubation conditions during induction of general anesthesia: a randomized controlled trial

BACKGROUND

The effort to improve tracheal intubation process is clinically valuable. We hypothesized that a preoperative brief exercise therapy would increase mouth opening and neck extension, enhancing intubation conditions during general anesthesia.

METHODS

Patients undergoing general anesthesia were randomized into two groups. The exercise group performed the exercise regimen including masseter muscle massage and stretching of jaw and neck joints before anesthetic induction, while the control did not. Before (baseline) and after the intervention, we evaluated Mallampati score, mouth aperture size, and sternomental distance. After tracheal intubation, intubation difficulty scale with direct laryngoscope and oropharyngeal soft tissue injury were also evaluated.

RESULTS

A total of 138 patients completed the analysis (control = 68, exercise = 70). Baseline characteristics did not differ between groups. At anesthetic induction, there was a significant difference in Mallampati score between the two groups (P = 0.039) and the incidence of Mallampati scores of 1 was higher in the exercise group (odds ratio [95% CI]: 2.1 [1.0-4.3], P = 0.043). Mouth opening after the intervention was greater in the exercise group than in the control group (estimated difference [95% CI]: - 2.4 [- 4.8 - -0.1], P = 0.042) and sternomental distance was similar between the two groups (estimated difference [95% CI]: - 3.7 [- 9.0-1.7, P = 0.175). The exercise group showed less soft tissue injuries (odds ratio [95% CI]: 0.2 [0.1-0.8], P = 0.009), however, intubation difficulty scale did not differ between the study groups (P = 0.112).

CONCLUSIONS

The brief pre-anesthetic exercise improved intubation conditions and enabled faster tracheal intubation with less injury to oropharyngeal soft tissue.

TRIAL REGISTRATION

Clinical Research Information Service (registration number: KCT0002618), registered at December 28, 2017.

Description and comparison of the performance of the upper lip bite test, the ratio of height to thyromental distance and other methods of preoperative airway assessment in a Nigerian population – a pilot study

Background: The ability to reliably predict difficult intubation can prevent airway related adverse outcomes. The upper lip bite test (ULBT) and ratio of height to thyromental distance (RHTMD) are airway predictive tests that have been evaluated in Caucasian populations with promising results. This study determined the test performance of the ULBT and RHTMD and compared with commonly employed predictive tests (modified Mallampati [MMT], thyromental distance [TMD] and inter-incisor gap [IIG]) in adult Nigerians. Methods: This was a cross-sectional study. Two hundred and sixteen consecutive, consenting ASA I-III patients presenting for surgery and planned for general anaesthesia with endotracheal intubation over a six month period in our teaching hospital, had all five airway assessment tests (ULBT, RHTMD, MMT, TMD and IIG) assessed preoperatively. The Cormack and Lehane grading was used to determine easy or difficult visualisation of the larynx (EVL or DVL). Sensitivity, specificity, predictive values and likelihood ratios of the tests were determined. Results: The sensitivities, specificities, positive and negative predictive values and positive and negative likelihood ratios respectively for the tests were: ULBT (11.8%, 99.0%, 50.0%, 92.9%, 11.71 and 0.89), RHTMD (35.3%, 92.5%, 28.6%, 94.4%, 4.68 and 0.70), TMD (29.4%, 97.5%, 50.0%, 94.2%, 11.71 and 0.72), MMT (52.9%, 86.4%, 25.0%, 95.6%, 3.90 and 0.54), and IIG (11.8%, 97.0%, 25.0%, 92.8%, 3.90 and 0.91). Conclusion: The modified Mallampati test had the highest sensitivity in this study, however all the tests evaluated showed only low to moderate sensitivity. The ULBT and RHTMD had low sensitivities in this population. However, based on the high positive likelihood ratios of the ULBT and the TMD, whenever positive, these tests do show a high probability of DVL and these two tests would probably perform similarly in this population. Anthropometric differences may account for differences in performance of preoperative airway assessment tests in various populations.

Will This Patient Be Difficult to Intubate?: The Rational Clinical Examination Systematic Review

IMPORTANCE

Recognizing patients in whom endotracheal intubation is likely to be difficult can help alert physicians to the need for assistance from a clinician with airway training and having advanced airway management equipment available.

OBJECTIVE

To identify risk factors and physical findings that predict difficult intubation.

DATA SOURCES

The databases of MEDLINE and EMBASE were searched from 1946 to June 2018 and from 1947 to June 2018, respectively, and the reference lists from the retrieved articles and previous reviews were searched for additional studies.

STUDY SELECTION

Sixty-two studies with high (level 1-3) methodological quality that evaluated the accuracy of clinical findings for identifying difficult intubation were reviewed.

DATA EXTRACTION AND SYNTHESIS

Two authors independently abstracted data. Bivariate random-effects meta-analyses were used to calculate summary positive likelihood ratios across studies or univariate random-effects models when bivariate models failed to converge.

RESULTS

Among the 62 high-quality studies involving 33 559 patients, 10% (95% CI, 8.2%-12%) of patients were difficult to intubate. The physical examination findings that best predicted a difficult intubation included a grade of class 3 on the upper lip bite test (lower incisors cannot extend to reach the upper lip; positive likelihood ratio, 14 [95% CI, 8.9-22]; specificity, 0.96 [95% CI, 0.93-0.97]), shorter hyomental distance (range of <3-5.5 cm; positive likelihood ratio, 6.4 [95% CI, 4.1-10]; specificity, 0.97 [95% CI, 0.94-0.98]), retrognathia (mandible measuring <9 cm from the angle of the jaw to the tip of the chin or subjectively short; positive likelihood ratio, 6.0 [95% CI, 3.1-11]; specificity, 0.98 [95% CI, 0.90-1.0]), and a combination of physical findings based on the Wilson score (positive likelihood ratio, 9.1 [95% CI, 5.1-16]; specificity, 0.95 [95% CI, 0.90-0.98]). The widely used modified Mallampati score (≥3) had a positive likelihood ratio of 4.1 (95% CI, 3.0-5.6; specificity, 0.87 [95% CI, 0.81-0.91]).

CONCLUSIONS AND RELEVANCE

Although several simple clinical findings are useful for predicting a higher likelihood of difficult endotracheal intubation, no clinical finding reliably excludes a difficult intubation. An abnormal upper lip bite test, which is easily assessed by clinicians, raises the probability of difficult intubation from 10% to greater than 60% for the average-risk patient.

Ultrasound Quantification of Anterior Soft Tissue Thickness Fails to Predict Difficult Laryngoscopy in Obese Patients

Morbid obesity is associated with difficult laryngoscopy and intubation. In the general population, bedside indices for predicting difficult intubation (i.e. Mallampati classification, thyromental distance, sternomental distance, mouth-opening and Wilson risk score) have poor-to-moderate sensitivity (20-62%) and moderate-to-fair specificity (82-97%). In the obese population, although the risk of difficult intubation after a positive Mallampati test is 34%, it is still not sufficient to be used as a single predictive test. An abundance of pretracheal soft tissue anterior to the vocal cords, as quantified by ultrasound, was a better predictor of difficult laryngoscopy than body mass index (BMI) in Israeli patients. Obesity is a growing problem in the United States: therefore we sought to confirm this finding in the obese population in the United States. We used ultrasound to quantify the neck soft tissue, from the skin to the anterior aspect of the trachea at the vocal cords, in 64 obese patients (BMI >35). We assessed thyromental distance, mouth-opening, jaw movement, limited neck mobility, modified Mallampati score, abnormal upper teeth, neck circumference, confirmed obstructive sleep apnoea, BMI, age, race and gender as predictors. Twenty patients were classified as difficult laryngoscopy; they were older (47±9 vs 42±1 years; P=0.048; mean±SD) and had less soft pretracheal tissue (20.4±3.0 vs 22.3±3.8 mm; P=0.049) than did easy laryngoscopy patients. Multivariate regression indicated that none of the factors was an independent predictor of difficult laryngoscopy. We conclude that the thickness of pretracheal soft tissue at the level of the vocal cords is not a good predictor of difficult laryngoscopy in obese patients in the United States.

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

Background and Aims

Preoperative airway assessment to predict patients with difficult laryngoscopy is always crucial for anesthesiologists. Several predictive tests have been studied by various authors in quest of finding the best airway predictor. Recently, a new airway predictor, thyromental height test (TMHT) has been reported to have good predictive value in assessing difficult airway. We conducted this study with primary aim to evaluate the diagnostic accuracy of TMHT and to compare it with other established airway predictors, such as ratio of height to thyromental distance (RHTMD), thyromental distance (TMD), and modified Mallampati test (MMT) for predicting difficult laryngoscopy.

Material and Methods

This prospective, observational study was conducted in 550 patients of either sex aged >18 years scheduled for elective surgery under general anesthesia. The patients' airway was assessed preoperatively by two anesthetists. Standard anesthetic protocol was followed in all the patients. The laryngoscopic view was graded according to Cormack-Lehane scale. The receiver operating characteristic (ROC) curve was used to calculate the ideal cut off values for TMHT and RHTMD. Standard formulae were used to calculate validity indexes.

Results

The incidence of difficult laryngoscopy was 10%. The cut-off value for TMHT and RHTMD were 5.1 cm and 19.5, respectively. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of TMHT were 78.18%, 93.94%, 58.90%, and 97.48%, respectively. The highest sensitivity, PPV, and NPV were observed with TMHT as compared with RHTMD, TMD, and MMT (P < 0.0001).

Conclusions

TMHT is the best predictive test with highest accuracy and odds ratio for predicting difficult airway out of all predictive tests evaluated.

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

BACKGROUND

The unanticipated difficult airway is a potentially life-threatening event during anaesthesia or acute conditions. An unsuccessfully managed upper airway is associated with serious morbidity and mortality. Several bedside screening tests are used in clinical practice to identify those at high risk of difficult airway. Their accuracy and benefit however, remains unclear.

OBJECTIVES

The objective of this review was to characterize and compare the diagnostic accuracy of the Mallampati classification and other commonly used airway examination tests for assessing the physical status of the airway in adult patients with no apparent anatomical airway abnormalities. We performed this individually for each of the four descriptors of the difficult airway: difficult face mask ventilation, difficult laryngoscopy, difficult tracheal intubation, and failed intubation.

SEARCH METHODS

We searched major electronic databases including CENTRAL, MEDLINE, Embase, ISI Web of Science, CINAHL, as well as regional, subject specific, and dissertation and theses databases from inception to 16 December 2016, without language restrictions. In addition, we searched the Science Citation Index and checked the references of all the relevant studies. We also handsearched selected journals, conference proceedings, and relevant guidelines. We updated this search in March 2018, but we have not yet incorporated these results.

SELECTION CRITERIA

We considered full-text diagnostic test accuracy studies of any individual index test, or a combination of tests, against a reference standard. Participants were adults without obvious airway abnormalities, who were having laryngoscopy performed with a standard laryngoscope and the trachea intubated with a standard tracheal tube. Index tests included the Mallampati test, modified Mallampati test, Wilson risk score, thyromental distance, sternomental distance, mouth opening test, upper lip bite test, or any combination of these. The target condition was difficult airway, with one of the following reference standards: difficult face mask ventilation, difficult laryngoscopy, difficult tracheal intubation, and failed intubation.

DATA COLLECTION AND ANALYSIS

We performed screening and selection of the studies, data extraction and assessment of methodological quality (using QUADAS-2) independently and in duplicate. We designed a Microsoft Access database for data collection and used Review Manager 5 and R for data analysis. For each index test and each reference standard, we assessed sensitivity and specificity. We produced forest plots and summary receiver operating characteristic (ROC) plots to summarize the data. Where possible, we performed meta-analyses to calculate pooled estimates and compare test accuracy indirectly using bivariate models. We investigated heterogeneity and performed sensitivity analyses.

MAIN RESULTS

We included 133 (127 cohort type and 6 case-control) studies involving 844,206 participants. We evaluated a total of seven different prespecified index tests in the 133 studies, as well as 69 non-prespecified, and 32 combinations. For the prespecified index tests, we found six studies for the Mallampati test, 105 for the modified Mallampati test, six for the Wilson risk score, 52 for thyromental distance, 18 for sternomental distance, 34 for the mouth opening test, and 30 for the upper lip bite test. Difficult face mask ventilation was the reference standard in seven studies, difficult laryngoscopy in 92 studies, difficult tracheal intubation in 50 studies, and failed intubation in two studies. Across all studies, we judged the risk of bias to be variable for the different domains; we mostly observed low risk of bias for patient selection, flow and timing, and unclear risk of bias for reference standard and index test. Applicability concerns were generally low for all domains. For difficult laryngoscopy, the summary sensitivity ranged from 0.22 (95% confidence interval (CI) 0.13 to 0.33; mouth opening test) to 0.67 (95% CI 0.45 to 0.83; upper lip bite test) and the summary specificity ranged from 0.80 (95% CI 0.74 to 0.85; modified Mallampati test) to 0.95 (95% CI 0.88 to 0.98; Wilson risk score). The upper lip bite test for diagnosing difficult laryngoscopy provided the highest sensitivity compared to the other tests (P < 0.001). For difficult tracheal intubation, summary sensitivity ranged from 0.24 (95% CI 0.12 to 0.43; thyromental distance) to 0.51 (95% CI 0.40 to 0.61; modified Mallampati test) and the summary specificity ranged from 0.87 (95% CI 0.82 to 0.91; modified Mallampati test) to 0.93 (0.87 to 0.96; mouth opening test). The modified Mallampati test had the highest sensitivity for diagnosing difficult tracheal intubation compared to the other tests (P < 0.001). For difficult face mask ventilation, we could only estimate summary sensitivity (0.17, 95% CI 0.06 to 0.39) and specificity (0.90, 95% CI 0.81 to 0.95) for the modified Mallampati test.

AUTHORS' CONCLUSIONS

Bedside airway examination tests, for assessing the physical status of the airway in adults with no apparent anatomical airway abnormalities, are designed as screening tests. Screening tests are expected to have high sensitivities. We found that all investigated index tests had relatively low sensitivities with high variability. In contrast, specificities were consistently and markedly higher than sensitivities across all tests. The standard bedside airway examination tests should be interpreted with caution, as they do not appear to be good screening tests. Among the tests we examined, the upper lip bite test showed the most favourable diagnostic test accuracy properties. Given the paucity of available data, future research is needed to develop tests with high sensitivities to make them useful, and to consider their use for screening difficult face mask ventilation and failed intubation. The 27 studies in 'Studies awaiting classification' may alter the conclusions of the review, once we have assessed them.

Neck fat volume as a potential indicator of difficult intubation: A pilot study

Background:

Direct laryngoscopy is the gold standard of the airway management in patients without predicted difficulties. If unpredicted difficulties are encountered instead, different algorithms to follow have been developed. To date, no single predictor is sufficiently valid. In clinical practice, it is used a combination of them to enhance the estimate, and despite the variety of parameters used, not all the difficult intubations are predicted. The aim of this work is to retrospectively analyze neck computed tomography scans of 37 patients who have had tracheal intubation and search for anatomic neck fat compartments that correlate with the intubation difficulty, and eventually find a suitable, clinical parameter that can potentially enhance the prediction of a difficult airway when used in combination of the preexisting scores.

Materials and Methods:

the patients are divided by direct laryngoscopy view into two groups: Group A (n = 31): Normal airway, with a Cormack Lehane, Score I or II; Group B (n = 6): Difficult airway, with a Cormack Lehane Score III or IV. In the zone of interest, it was measured the neck volume parameter and other subparameters.

Results:

Despite a positive trend is shown for anterior fat volume (AFV) (P = 0.23) and fat volume (FV) (P = 0.28), statistically significant differences (P < 0.05) were not found between Group A and B in any of the measurements acquired.

Conclusions:

According to the literature, our results confirmed that there is still no single element that can predict a difficult intubation. Although no statistical significance was found, the AFV and FV have shown to have a potential predictive role for difficult intubation. Further studies with bigger samples are advisable to confirm this encouraging result.

Thyromental height test for prediction of difficult laryngoscopy in patients undergoing coronary artery bypass graft surgical procedure

BACKGROUND

Patients undergoing coronary artery bypass graft (CABG) procedures have higher incidence of difficult laryngoscopy and intubation than general surgery population. Accurate prediction of difficult laryngoscopy in CABG patients is desirable to reduce the hemodynamic response and myocardial oxygen requirements. Recently, thyromental height test (TMHT) has been proposed as one of the highly sensitive and specific bedside tests to predict difficult airway. We, in our prospective observational study, evaluated the accuracy of the TMHT in predicting difficult laryngoscopy.

METHODOLOGY

A total of 345 patients undergoing CABG of either sex, in the age group of 35-80 years, American Society of Anesthesiologists 111, undergoing CABG, were studied. Airway assessment was performed with modified Mallampati test with the addition of thyromental distance, sternomental distance, and TMHT. Intraoperatively, direct laryngoscopy was done in accordance with Cormack and Lehane grade of laryngoscopy. The preoperative data and laryngoscopic findings were used together to evaluate the accuracy of TMHT. The sensitivity, specificity, positive and negative predictive values of other three tests were calculated according to standard formula.

RESULTS

A total of 345 patients were in the group with mean age of study population at 56.7 (standard deviation 9.1) years (35-80 years). This study showed that almost all tests had good specificity, but sensitivity was poor. However, sensitivity of TMHT was 75% with accuracy of 95%. Receiver operating characteristic curve analysis of TMHT-derived cutoff was 52.17 which increased sensitivity to 81.25% and specificity to 92.3%.

CONCLUSION

TMHT had a higher sensitivity compared to other tests along with good positive and negative predictive value and a very high specificity.

Evaluation of the McGrath® MAC videolaryngoscope in a tertiary teaching hospital

Background:

Videolaryngoscopes have become increasingly popular in recent years for use in both normal and difficult airways. Despite this trend, their benefit remains controversial. The McGrath® MAC videolaryngoscope (Aircraft Medical Ltd, Edinburgh, UK) is used for first line or rescue intubation, and for training in videolaryngoscopy intubation. We conducted a prospective observational study to assess the performance of the McGrath® MAC.

Methods:

We evaluated the use of the McGrath® MAC videolaryngoscope from January 2016 to April 2016. We recruited 500 adult patients undergoing elective surgery requiring endotracheal intubation. Data was collected via an online survey. The primary outcome was the success of intubation with the McGrath® MAC. Secondary outcomes included the ease of the McGrath® MAC insertion, best glottic view, ease of tracheal tube insertion, number of intubation attempts, evidence of airway trauma, quality of view, adjunct used, airway manoeuvres used, quality of image on monitor screen and overall impression of the device.

Results:

A total of 428 responses were analysed. The overall success rate was 97.9% (95% confidence interval 96.0–99.0%). The success rate for those with predictors of difficult airway was 95.5% (95% confidence interval 87.6–99.5%). Easy scope insertion was reported by 97.2% of anaesthetists and 89.7% reported easy tube insertion. Some of our cases (1.9%) were complicated by airway trauma involving superficial oropharyngeal or lip injury.

Conclusion:

The McGrath® MAC videolaryngoscope is a good choice for a videolaryngoscope, conferring advantages of a high intubation success rate, ease of laryngoscope insertion and ease of intubation. It is suitable for use in predicted difficult airways.

Effects of airway evaluation parameters on the laryngeal view grade in mandibular prognathism and retrognathism patients

BACKGROUND

Failure to maintain a patent airway can result in brain damage or death. In patients with mandibular prognathism or retrognathism, intubation is generally thought to be difficult. We determined the degree of difficulty of airway management in patients with mandibular deformity using anatomic criteria to define and grade difficulty of endotracheal intubation with direct laryngoscopy.

METHODS

Measurements were performed on 133 patients with prognathism and 33 with retrognathism scheduled for corrective esthetic surgery. A case study was performed on 89 patients with a normal mandible as the control group. In all patients, mouth opening distance (MOD), mandibular depth (MD), mandibular length (ML), mouth opening angle (MOA), neck extension angle (EXT), neck flexion angle (FLX), thyromental distance (TMD), inter-notch distance (IND), thyromental area (TMA), Mallampati grade, and Cormack and Lehane grade were measured.

RESULTS

Cormack and Lehane grade I was observed in 84.2%, grade II in 15.0%, and grade III in 0.8% of mandibular prognathism cases; among retrognathism cases, 45.4% were grade I, 27.3% grade II, and 27.3% grade III; among controls, 65.2% were grade I, 26.9% were grade II, and 7.9% were grade III. MOD, MOA, ML, TMD, and TMA were greater in the prognathism group than in the control and retrognathism groups (P < 0.05). The measurements of ML were shorter in retrognathism than in the control and prognathism groups (P < 0.05).

CONCLUSIONS

Laryngoscopic intubation was easier in patients with prognathism than in those with normal mandibles. However, in retrognathism, the laryngeal view grade was poor and the ML was an important factor.

Assessment before airway management

It is wise to plan and prepare for the unexpected difficult airway. Although it is essential to take a history and examine every patient prior to airway management, preoperative anticipation of a difficult airway occurs in only 50% of patients subsequently found to have a difficult airway. Bedside screening tests lack accuracy. The modified Mallampati test and the measurement of thyromental distance are unreliable for prediction of difficult tracheal intubation. Knowledge of risk factors for various airway management techniques may help when devising an airway management plan.

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.

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

BACKGROUND

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.

RESULTS

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).

CONCLUSION

The NC/TM Discomparable with NC, RHTMD, and ULBT for the prediction of difficult laryngoscopy in caes are an delivery.

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

Background:

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.

Results:

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).

Conclusion:

The HMDR is comparable with RHTMD and ULBT for prediction of difficult laryngoscopy in the general population, but was significantly more than for MMT.

Sensitivity of palm print sign in prediction of difficult laryngoscopy in diabetes: A comparison with other airway indices

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.

Methods:

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.

Results:

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.

Conclusion:

The PP test appears to be the most sensitive and specific in the prediction of difficult laryngoscopy in diabetic patients.

Prediction of difficult laryngoscopy: Extended mallampati score versus the MMT, ULBT and RHTMD

BACKGROUND

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.

RESULTS

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.

CONCLUSION

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.

Airway management

In this article, recent literature related to airway management in the ambulatory surgery setting is reviewed. Practical pointers to improve clinical success and avoid complications of newer airway management techniques are provided.

Comparison of acromioaxillosuprasternal notch index (a new test) with modified Mallampati test in predicting difficult visualization of larynx

BACKGROUND

We aimed to compare the efficacy of a new bedside screening test named acromioaxillosuprasternal notch index (AASI) with modified Mallampati (MMP).

METHODS

A total of 603 adult patients, who were candidates for tracheal intubation in elective surgery, were enrolled in this prospective study. Preoperative airway assessment was carried out with AASI and MMP. The new AASI score is calculated based on the following measurements: (1) using a ruler, a vertical line is drawn from the top of the acromion process to the superior border of the axilla at the pectoralis major muscle (line A); (2) a second line is drawn perpendicular to line A from the suprasternal notch (line B); and (3) the portion of line A that lies above the point where line B intersects it is line C. AASI is calculated by dividing the length of line C by that of line A (AASI = C/A). After induction of anesthesia, the laryngeal view was recorded according to the Cormack-Lehane grading system. Receiver operating characteristic curve analysis was employed to compare between AASI and MMP.

RESULTS

Difficult visualization of larynx (DVL, Cormack-Lehane III and IV) was observed in 38 (6.3%) patients. The best cutoff point for DVL was defined at AASI > 0.49. AASI had a lower false negative rate and higher predictive values (sensitivity, positive predictive value, and accuracy) in comparison with MMP.

CONCLUSION

AASI was associated with higher predictive values than MMP and could be used for estimation of DVL.

Diagnostic value of the upper lip bite test in predicting difficulty in intubation with head and neck landmarks obtained from lateral neck X-ray

Background:

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.

Methods:

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.

Results:

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.

Conclusion:

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.

Predictors of difficult intubation defined by the intubation difficulty scale (IDS): predictive value of 7 airway assessment factors

Background

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.

Methods

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.

Results

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).

Conclusions

We suggest that TAS (> 6) and ULBT (class III) are the most useful factors predicting DI.

Examination of Submental Space as an Alternative Method of Airway Assessment (Submental Sign)

Background

Difficult airway especially failed intubation has been associated with a high incidence of mortality and morbidity. Most of mortalities occur when an anaesthesiologist encounters an unanticipated difficult airway.

Findings

In 1999, a 23 yr. old, 65 kg weight and 170 cm height female patient had been scheduled for arthroscopy. Despite totally normal airway assessment (thyromental distance, mouth opening, jaw and neck movement ...) I was astonished by encountering a grade IV Cormack - Lehane laryngoscopic view. Tracheal intubation was impossible and ventilation was very difficult.

On attempt to attain a better laryngoscopic view, while manipulating submandibular region I encountered a bulky noncompliant submental space (Submental Sign). This event made me more alert regarding this finding. Thereafter I noted for this sign throughout the past years and I found it very helpful.

These findings encouraged me to write this report, and suggest a routine examination of submental space in order to keep the safety of the patient at the heart of the care we provide.

Conclusion

Evaluation of the submental space is suggested as an alternative predictor of difficult airway and routine examination of the submental space is of value in airway assessment.

A comparison of the ratio of patient's height to thyromental distance with the modified Mallampati and the upper lip bite test in predicting difficult laryngoscopy

BACKGROUND

THE AIM OF THE PRESENT STUDY WAS TO COMPARE THE ABILITY TO PREDICT DIFFICULT VISUALIZATION OF THE LARYNX FROM THE FOLLOWING PREOPERATIVE AIRWAY PREDICTIVE INDICES, IN ISOLATION AND COMBINATION: modified Mallampati test (MMT), the ratio of height to thyromental distance (RHTMD) and the Upper-Lip-Bite test (ULBT).

METHODS

We collected data on 603 consecutive patients scheduled for elective surgery under general anesthesia requiring endotracheal intubation and then evaluated all three factors before surgery. 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 value, Receiver operating characteristic (ROC) Curve and the area under ROC curve (AUC) for each airway predictor in isolation and in combination were determined.

RESULTS

Difficult laryngoscopy (Grade 3 or 4) occurred in 41 (6.8%) patients. The main endpoint of the present study, the AUC of the ROC, was significantly lower for the MMT (AUC, 0.511; 95% CI, 0.470-0.552) than the ULBT (AUC, 0.709; 95% CI, 0.671-0.745, P=0.002) and the RHTMD score (AUC, 0.711; 95% CI, 0.673-0.747, P=0.001). There was no significant difference between the AUC of the ROC for the ULBT and the RHTMD score. By using discrimination analysis, the optimal cutoff point for the RHTMD for predicting difficult laryngoscopy was 21.06 (sensitivity, 75.6%; specificity, 58.5%).

CONCLUSION

The RHTMD is comparable with ULBT for prediction of difficult laryngoscopy in general population.

[Evaluation of a protocol for predicting difficult airway in routine practice: interobserver agreement]

OBJECTIVES

To evaluate a protocol for routine assessment of potential risk factors for difficult airway intubation in an anesthesia department, by measuring interobserver agreement and the behavior of the factors in a predictive model.

MATERIAL AND METHODS

A cross-sectional study group of 320 consecutive patients undergoing major surgery requiring orotracheal intubation was assessed for possible difficult airway. We calculated interrater agreement for recording of the Mallampati score, thyromental distance less than 6 cm, thick neck, kyphosis, small mouth, macroglossia, and dental prosthesis during the preanesthesia examination (by an anesthetist) and on the day of the operation (by an anesthetist and a resident). We constructed a model to predict difficult intubation (requiring 3 or more attempts).

RESULTS

The kappa indices of agreement between the anesthetists at the preoperative examination and in the operating room or the resident were all less than 0.6. Factors like thyromental distance, small mouth, and kyphosis had kappa indices less than 0.21. The kappa index between the resident and the anesthetist in the operating room was over 0.55. The only factor that had a different level of agreement was the presence or not of a dental prosthesis. None of the studied individual factors, nor these factors in association with the Mallampati score, achieved significance in a bivariate regression model to predict difficult intubation.

CONCLUSIONS

There is poor interobserver agreement on factors for predicting difficult airway in comparisons between preoperative and operating room assessment by an anesthetist or a resident. The individual predictive factors and their association with the Mallampati score did not prove useful for predicting difficult intubation.

The difficult airway in adult critical care

INTRODUCTION

The difficult airway is a common problem in adult critical care patients. However, the challenge is not just the establishment of a safe airway, but also maintaining that safety over days, weeks, or longer.

AIMS

This review considers the management of the difficult airway in the adult critical care environment. Central themes are the recognition of the potentially difficult airway and the necessary preparation for (and management of) difficult intubation and extubation. Problems associated with tracheostomy tubes and tube displacement are also discussed.

RESULTS

All patients in critical care should initially be viewed as having a potentially difficult airway. They also have less physiological reserve than patients undergoing airway interventions in association with elective surgery. Making the critical care environment as conducive to difficult airway management as the operating room requires planning and teamwork. Extubation of the difficult airway should always be viewed as a potentially difficult reintubation. Tube displacement or obstruction should be strongly suspected in situations of new-onset difficult ventilation.

CONCLUSIONS

Critical care physicians are presented with a significant number of difficult airway problems both during the insertion and removal of the airway. Critical care physicians need to be familiar with the difficult airway algorithms and have skill with relevant airway adjuncts.

Prediction of difficult tracheal intubation in Turkish patients: a multi-center methodological study

BACKGROUND AND OBJECTIVE

Preoperative evaluation is important in the detection of patients at risk for difficult airway management. It is still unclear whether true prediction is possible and which variables should be chosen for evaluation. The aim of this prospective, multi-centre study was to investigate the incidence of difficult intubation, the sensitivity and positive predictive values of clinical screening tests and whether combining two or more of these tests will improve the prediction of difficult intubation in Turkish patients.

METHODS

Seven study sites from six regions in Turkey participated in this study. One thousand six hundred and seventy-four ASA physical status I-III patients, scheduled to undergo elective surgery under general anaesthesia, were included.

RESULTS

The incidence of difficult intubation was 4.8% and increased with age (P < 0.05). The incidence of difficult intubation was significantly higher in patients who had a Mallampati III or IV score, a decreased average thyromental and sternomental distance, decreased mouth opening, or decreased protrusion of the mandible (P < 0.05). Mouth opening and Mallampati III-IV were found to be the most sensitive criteria when used alone (43% and 35%, respectively). Combination of tests did not improve these results.

CONCLUSIONS

There is still no individual test or a combination of tests that predict difficult intubations accurately. Tests with higher specificity despite low positive predictive value are needed.

Endotracheal Intubation with Flexible Fiberoptic Bronchoscopy in Patients with Abnormal Anatomic Conditions of the Head and Neck

We performed a retrospective chart review to evaluate the indications for endotracheal intubation via flexible fiberoptic bronchoscopy in patients who were scheduled for surgery or who were hospitalized in the intensive care unit of our 1,100-bed, tertiary care university hospital. We reviewed 9,201 clinical records of anesthetic procedures during which endotracheal intubation had been performed from January to December 2002. We identified 66 patients who had been intubated with flexible fiberoptic bronchoscopy. On preanesthetic examination, 61 of these patients had been found to be poor candidates for conventional laryngoscopic intubation—51 because of abnormal head and neck anatomy and 10 because of reduced visual access to the airway (Mallampati class IV). The remaining 5 patients were intubated via flexible fiberoptic bronchoscopy after conventional intubation had failed during emergency surgery. Our study emphasizes (1) the importance of the preanesthetic examination of surgical patients, to identify those in whom conventional intubation would likely be problematic, and (2) the need to have fiberoptic bronchoscopes and an anesthesiologist or bronchoscopist skilled in their use available in operating suites and intensive care units.

Easy Endotracheal Intubation of a Patient Suffering from Both Cushing's and Nelson's Syndromes Predicted by the Upper Lip Bite Test Despite a Mallampati Class 4 Airway

A 31-yr-old woman with concurrent Cushing's and Nelson's syndromes was scheduled for transsphenoidal hypophysectomy. The patient had generalized edema, morbid obesity, and a history of sleep apnea. Her Mallampati assessment was Class 4, suggesting very difficult intubation, but the upper lip bite test predicted easy intubation. After rapid sequence induction, there was a Class 1 view on laryngoscopy, and intubation was accomplished easily.

Evaluation of the airway and preparation for difficulty

Preoperative airway evaluation is essential to consider which is the best method of maintaining and protecting the airway during surgery and whether problems with airway management are likely. In general surgical patients, the prevalence of difficult intubation is low and tests have poor predictive power. This means that the patient may be evaluated as normal but prove to be difficult. The absence of reliable prediction in general surgical patients means that airway strategy holds the key to successful management. Where there are obvious abnormalities in the history, examination or imaging the preoperative evaluation will allow choice of the most appropriate airway strategy which may include preparation of the patient, assembling of alternative airway equipment, advice and help from a more senior or skilled anaesthetist or aid from a surgical colleague or assistant.

Predictive Performance of Three Multivariate Difficult Tracheal Intubation Models: A Double-Blind, Case-Controlled Study

We performed a case-controlled, double-blind study to examine the performance of three multivariate clinical models (Wilson, Arné, and Naguib models) in the prediction of unanticipated difficult intubation. The study group consisted of 97 patients in whom an unanticipated difficult intubation had occurred. For each difficult intubation patient, a matched control patient was selected in whom tracheal intubation had been easily accomplished. Postoperatively, a blinded investigator evaluated both patients. The clinical assessment included the patient's weight, height, age, Mallampati score, interincisor gap, thyromental distance, thyrosternal distance, neck circumference, Wilson risk sum score, history of previous difficult intubation, and diseases associated with difficult laryngoscopy or intubation. The Naguib model was significantly more sensitive (81.4%; P < 0.0001) than the Arné (54.6%) or Wilson (40.2%) models. Both the Naguib (76.8%) and Arné (74.7%) model classified more intubations correctly (P = 0.01) than the Wilson model (66.5%). The specificity of Arné, Wilson, and Naguib model was 94.9%, 92.8%, and 72.2%, respectively (P < 0.0001). The corresponding area under the receiver operating characteristic curve was 0.87, 0.79, and 0.82, respectively. Our new model for prediction of difficult intubation was developed using logistic regression and includes thyromental distance, Mallampati score, interincisor gap, and height. This model is 82.5% sensitive and 85.6% specific with an area under the receiver operating characteristic curve of 0.90.

The Predictive Value of the Height Ratio and Thyromental Distance: Four Predictive Tests for Difficult Laryngoscopy

Preoperative evaluation of anatomical landmarks and clinical factors help identify potentially difficult laryngoscopies; however, predictive reliability is unclear. Because the ratio of height to thyromental distance (RHTMD) has a demonstrably better predictive value than the thyromental distance (TMD), we evaluated the predictive value and odds ratios of RHTMD versus mouth opening, TMD, neck movement, and oropharyngeal view (modified Mallampati). We collected data on 550 consecutive patients scheduled for elective-surgery general anesthesia requiring endotracheal intubation and then assessed all five factors before surgery. An experienced anesthesiologist, not apprised of the recorded preoperative airway assessment, performed the laryngoscopy and grading (as per Cormack and Lehane's classification). Difficult laryngoscopy (Grade 3 or 4) occurred in 69 patients (12.5%). RHTMD had a higher sensitivity, positive predictive value, and fewer false negatives than the other variables tested. In the multivariate analysis, three criteria were found independent for difficult laryngoscopy (neck movement < or =80 degrees; Mallampati Class 3 or 4, and RHTMD > or =23.5). The odds ratio (95% confidence interval) of the RHTMD, Mallampati class, and neck movement were 6.72 (3.29-13.72), 2.96 (1.63-5.35), and 2.73 (1.14-6.51), respectively. The odds ratio for RHTMD was the largest and thus may prove a useful screening test for difficult laryngoscopy.

Failed intubation secondary to complete tracheal rings: a case report and literature review

Unanticipated difficult intubation in asymptomatic infants is a rare event. Most infants with congenital tracheal anomalies will present with airway problems. We present a case of failed intubation in an asymptomatic 8-day-old infant with complete tracheal rings. The infant could be ventilated with an LMA and surgery for placement of a ventricular-peritoneum shunt was completed. This is a report of the case and review of the literature.

Inter-observer agreement of tests used for prediction of difficult laryngoscopy/tracheal intubation

BACKGROUND

Guidelines recommend pre-operative airway evaluation for the prediction of airway management difficulties. Combining tests for evaluation increases the accuracy of the assessment. One model including seven parameters transformed into a simplified airway risk index (SARI) has been proven to be valid. We determined the inter-observer agreement of the specific test combinations included in SARI as well as of the total score.

METHODS

Four observers assessed 136 patients, 120 without and 16 with a difficult airway history. Two residents and two specialists in anaesthesia performed the airway assessment consisting of the measurement of the mouth opening, the thyromental distance (TMD), the ability to protrude the mandible and an evaluation of the Mallampati class and head and neck mobility. Body weight was also recorded. Inter-observer agreement between specialists and residents, separately, was analysed using kappa statistics and Spearman's correlation analysis and the limits of agreement were evaluated using the 95% confidence interval. The agreement between pairs of assessors was also evaluated.

RESULTS

The inter-observer agreement was good to excellent for both specialists and residents when measuring mouth opening (Spearman's correlation coefficient R=0.88-0.97) and the horizontal distance between the upper and lower incisors during jaw protrusion (R=0.56-0.97). The Mallampati classification assessment demonstrated satisfactory to complete inter-observer agreement (kappa=0.41-1). The assessment of TMD and neck mobility showed considerable discrepancies between observers.

CONCLUSIONS

We demonstrated good inter-observer agreement using three tests from SARI and recommend the Mallampati classification, mouth opening and ability of jaw protrusion for pre-operative airway evaluation. A simplification of the assessment of TMD and neck mobility is warranted.

Lateral neck radiography for prediction of difficult orotracheal intubation

BACKGROUND AND OBJECTIVES

Failed endotracheal intubation is a principal cause of morbidity and mortality in anesthetized patients. The aim of this study was to investigate the efficiency of lateral neck radiography in predicting difficult intubation.

METHODS

In a prospective triple-blind study, 100 patients (aged 18-89 yr), scheduled for elective surgery were randomly selected. Lateral neck X-ray was obtained from each of the patients before operation. Several angles and parameters on the X-ray were proposed to illustrate a relationship with easy or difficult intubation. A radiologist recorded these angles before the operation. An anaesthesiologist also determined the Mallampati score preoperation. At the time of intubation, two other anesthesiologists performed a laryngoscopy and, according to established criteria, identified the patients as easy or difficult intubation. The results were then compared with each other.

RESULTS

Fifteen patients were identified as having difficult intubation (laryngoscopy Grades III and IV). Sensitivity and specificity of the Mallampati Class test were 26% and 100%, respectively. The sensitivity and specificity of the lateral neck X-ray for three measured angles were 100%. The positive and negative predictive values (NPVs) for those angles were 100% and for Mallampati classification were 100% and 80%, respectively.

CONCLUSIONS

Compared to the Mallampati Class test, our method of analyzing the lateral X-ray, although not as easy and universally applicable as Mallampati Class test, proved to be a suitable method for predicting difficult intubation.

Airway management after failure to intubate by direct laryngoscopy: outcomes in a large teaching hospital

PURPOSE

The purpose of this single-centre database review was to establish the incidence of failure to intubate by direct laryngoscopy, to measure morbidity and mortality associated with this event, and to examine the use and efficacy of alternative airway devices.

METHODS

Difficult intubation via direct laryngoscopy at Mayo Clinic Rochester is recorded in an electronic database using a functional classification: 0 = no difficulty; 1 = mild to moderate difficulty; and 2 = severe difficulty often requiring a change in intubation technique. Using this database, the total number of intubations was determined for a selected review period and the incidence of failure to intubate by direct laryngoscopy was established. Abstraction of chart data allowed for determination of associated morbidity and mortality, success of alternative airway devices, and case cancellation rate.

RESULTS

During the period from August 1, 2001 through December 31, 2002, 37,482 patients underwent general anesthesia with attempted direct laryngoscopy. One hundred sixty-one patients (0.43%) could not be intubated by direct laryngoscopy alone. Morbidity associated with difficult intubation included soft tissue/dental damage (n = 8), intraoperative cardiac arrest (n = 1), and possible aspiration (n = 1). Three patients required intensive care unit admission. There was no associated mortality. The most commonly used alternative airway device was the flexible fibreoptic scope. Five case cancellations resulted from failure to intubate with alternative devices.

CONCLUSION

The rate of unexpected failure to intubate by direct laryngoscopy is essentially unchanged from earlier studies. While morbidity was low, continued education and early use of alternative difficult airway devices may further limit complications associated with this event.