Comparison of the Mallampati Classification in Sitting and Supine Position to Predict Difficult Tracheal Intubation

Development and validation of a regression model with nomogram for difficult video laryngoscopy in Chinese population: a prospective, single-center, and nested case-control study

Background

Airway management failure is associated with increased perioperative morbidity and mortality. Airway-related complications can be significantly reduced if difficult laryngoscopy is predicted with high accuracy. Currently, there are no large-sample studies on difficult airway assessments in Chinese populations. An airway assessment model based on the Chinese population is urgently needed to guide airway rescue strategy.

Methods

This prospective nested case-control study took place in a tertiary hospital in Shanghai, China. Information on 10,549 patients was collected, and 8,375 patients were enrolled, including 7,676 patients who underwent successful laryngoscopy and 699 patients who underwent difficult laryngoscopy. The baseline characteristics, medical history, and bedside examinations were included as predictor variables. Laryngoscopy was defined as 'successful laryngoscopy' based on a Cormack-Lehane Grades of 1-2 and as 'difficult laryngoscopy' based on a Cormack-Lehane Grades of 3-4. A model was developed by incorporating risk factors and was presented in the form of a nomogram by univariate logistic regression, least absolute shrinkage and selection operator, and stepwise logistic regression. The main outcome measures were area under the curve (AUC), sensitivity, and specificity of the predictive model.

Result

The AUC value of the prediction model was 0.807 (95% confidence interval [CI]: 0.787-0.828), with a sensitivity of 0.730 (95% CI, 0.690-0.769) and a specificity of 0.730 (95% CI, 0.718-0.742) in the training set. The AUC value of the prediction model was 0.829 (95% CI, 0.800-0.857), with a sensitivity of 0.784 (95% CI, 0.73-0.838) and a specificity of 0.722 (95% CI, 0.704-0.740) in the validation set.

Conclusion

Our model had accurate predictive performance, good clinical utility, and good robustness for difficult laryngoscopy in the Chinese population.

A Prospective Cohort Study on the Respiratory Effect on Modified Mallampati Scoring

Background

Mallampati scoring is a common exam method for evaluating the oropharynx as a part of the airway assessment and for anticipation of difficult intubation. It partitions the oropharynx into 4 categories with scores of 1, 2, 3, and 4. Even though its reliability is known to be limited by confounding factors such as patient positioning, patient phonation, tongue protrusion, and examiner variability, the effect of respiration, i.e., inspiration and expiration, has not yet been formally studied.

Methods

Mallampati scores were collected from 100 surgical patients during both inspiration and expiration and later compared to the score obtained in the medical record, determined by a board certified anesthesiologist.

Results

Score deviations from the medical record reference were compared for both inspiration and expiration showing that respiration affects Mallampati scores; for some patients, the scores improved (i.e., decreased), while in others they worsened (i.e., increased). The respiratory change effect was quantified and visualized by plotting the area under the curve of the histogram of the deviations. 42% of the patients had a worsening of scores by 1 or 2 points with inspiration while 36% of the patients had a worsening of scores by 1 or 2 points with expiration.

Conclusions

Mallampati scoring is commonly used in evaluating the oropharynx as a part of the airway assessment and as a screening tool for difficult intubations. However, as this study points out, the respiratory cycle substantially affects the Mallampati scoring system, with significant deviations of 1 or 2 points. In a scoring system of 4 score categories, these deviations are remarkable.

A Systematic Review and Meta-Analysis of Randomized Controlled Trials on Supine vs. Nonsupine Endotracheal Intubation

Background

This systematic review and meta-analysis of randomized controlled trials (RCTs) was performed to compare the safety and efficacy of supine vs. nonsupine positions during intubation.

Methods

Based on the literature from inception to October 2020, 13 studies with nonemergent intubation in supine and nonsupine positions were chosen using PRISMA and MOOSE protocols. Pooled estimates were calculated using random-effects models with 95% confidence interval (CI). The primary outcome was a successful intubation, attempt, and duration of intubation. The secondary outcome was adverse events (trauma and hypoxia). Bias was evaluated qualitatively, by visual analysis, and quantitatively through the Egger test.

Results

The final analysis included 13 clinical trials with 1,916 patients. The pooled success rates in the supine vs. lateral positions were 99.21% and 98.82%. The supine vs. semierect positions were 99.21% and 98.82%. The 1st attempt success rate in the supine vs. lateral position was 85.35% and 88.56% compared to 91.38% and 90.76% for the supine vs. semierect position. The rate of total adverse events in the supine position was 3.73% vs. 6.74% in the lateral position, and the rate of total adverse events in the supine position was 0.44% vs. 0.93% in semierect position. Low to substantial heterogeneity was noted in our analysis. Discussion. There is no significant difference between total successful intubations and success from 1st intubation attempt between supine and nonsupine positions. However, there are slightly higher rates of adverse events in nonsupine position. Addition of more recent studies on supine vs. nonsupine intubations would improve this study. Given these findings, it is important to develop more studies regarding different intubation positions and techniques with the aim of improving efficacy and decreasing adverse outcomes. Other. This review is not registered in a public database. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Endotracheal Intubation with King Vision Video Laryngoscope vs Macintosh Direct Laryngoscope in ICU: A Comparative Evaluation of Performance and Outcomes

Background

Endotracheal intubation to protect airway patency in critically ill patients with the use of videolaryngoscopes has been emerging and their expertise to handle is crucial. Our study focuses on the performance and outcomes of King Vision video laryngoscope (KVVL) in intensive care unit (ICU) compared to Macintosh direct laryngoscope (DL).

Materials and methods

This comparative study was conducted by randomizing 143 critically ill patients in ICU into two groups: KVVL and Macintosh DL (n = 73; n = 70). The intubation difficulty was assessed by Mallampati score III or IV, apnea syndrome (obstructive), cervical spine limitation, opening mouth <3 cm, coma, hypoxia, anesthesiologist nontrained (MACOCHA) score. The primary endpoint was the glottic view measured by Cormack-Lehane (CL) grading. The secondary endpoints were a first-pass success, the time required for intubation, airway morbidities, and manipulations required.

Results

The KVVL group showed the primary endpoint of significantly improved glottic visualization measured in terms of CL grading compared with the Macintosh DL group (p < 0.001). In the KVVL group, the first pass success rate was higher (95.7%) compared to the Macintosh DL group (81.4%) (p < 0.05). The time required for intubation in the KVVL group (28.77 ± 2.63 seconds) was significantly less compared with Macintosh DL (38.84 ± 2.72 seconds) group (p < 0.001). The airway morbidities observed were similar in both groups (p = 0.5) and the manipulation required for endotracheal intubation was significantly less (p < 0.05) in our KVVL group (16 cases; 23%) compared to the Macintosh DL group (8 cases; 10%).

Conclusion

We found that the performance and outcomes of KVVL in intubating critically ill ICU patients were promising when handled by experienced operators who are experts in anesthesiology and airway management.

How to cite this article

Dharanindra M, Jedge PP, Patil VC, Kulkarni SS, Shah J, Iyer S, et al. Endotracheal Intubation with King Vision Video Laryngoscope vs Macintosh Direct Laryngoscope in ICU: A Comparative Evaluation of Performance and Outcomes. Indian J Crit Care Med 2023;27(2):101-106.

A Prospective, Comparative Study to Evaluate the Diagnostic Accuracy of Mallampati Grading in Supine and Sitting Positions for Prediction of Difficult Airway

Background & aim

Difficult airway is a major concern for all anaesthesiologists because failure to secure airway could lead to devastating complications or may increase morbidity and mortality. Airway assessment, therefore, is of paramount importance and anticipating a difficult airway prior to anesthetic administration, could help us in better preparation as well as avoidance of life-threatening complications. There are various tests available to assess the airway, out of which, modified Mallampati test (MLPT) is one of the common, easy and reliable methods to predict difficult airway. Mallampati test, usually is done with patient in sitting position. However, in certain group of patients in whom sitting position is not possible (suspected cervical spine injury, pelvic injury, patients in shock, etc.), the Mallampati test can be done in supine position. Few studies were available which concluded that Mallampati test in supine position was not only reliable but also superior to sitting position, whereas, few other studies contradicted this opinion. We, therefore, wanted to address this issue and tried to find out whether Mallampati test in supine position could offer better diagnostic accuracy or not.

Materials & methods

Mallampati test (MLPT) in sitting position was done in 100 patients initially in preoperative period and subsequently in supine position inside operating room prior to induction of anesthesia. During laryngoscopy, Cormack-Lehane (CL) grading was noted in all patients. Correlation of Mallampati test in sitting and supine position with Cormack-Lehane grading was obtained. A receiver operating characteristics (ROC) analysis was done to determine the area under the curve, the sensitivity and the specificity. Positive predictive value (PPV) and negative predictive value (NPV) were also calculated to analyse the diagnostic accuracy of Mallampati score (MLPT) in sitting and supine position.

Results

A toal of 22.2% of patients had difficult intubation (CL grade 3) although MLPT of these patients in sitting position anticipated a non-difficult airway (MLPT 1 and 2) and there was no significant correlation between MLPT grade in sitting position with the Cormack-Lehane grade. In comparison to sitting position, MLPT in supine position had significant correlation with the Cormack-Lehane grading and all patients with supine MLPT 1 and 2 (non-difficult airway) had easy intubation (CL grade 1 and 2). ROC analysis also showed that MLPT grade in supine position had superior correlation and better diagnostic accuracy than MLPT in sitting position for assessment of airway as indicated by higher sensitivity and better positive as well as negative predictive values.

Conclusion

Mallampati test done in supine position has far greater sensitivity and is superior in predicting difficult intubation as compared to MLPT done in conventional sitting position.

The Association Between Upper Airway Patency and Speaking Valve Trial Tolerance for Patients With Tracheostomy: A Clinical Retrospective Study and an In Vitro Study

Purpose Upper airway patency is crucial in a patient's ability to tolerate a one-way speaking valve (SV). Traditional assessment of airway patency is mainly subjective. We developed four noninvasive methods to assess patency (leak volume, transtracheal pressure [TTP], end-tidal CO₂, and Mallampati score) in our institution. This study was aimed to evaluate the effectiveness of the four methods and explore the relationship between the patient's upper airway patency and SV trial tolerance. Method A retrospective cohort study was conducted to enroll adult patients with tracheostomies eligible for an SV trial from April 2019 through January 2020. An in vitro study was also implemented to explore the relationship between upper airway patency and noninvasive measurements. Results Forty patients (22 men and 18 women) were included; 16 used SV in-line with mechanical ventilation. Twenty-four patients tolerated an SV trial of > 10 min; they had lower TTP (3.0 [2.0-9.0] vs. 15.0 [9.3-21.3] cm H₂O, p < .001), higher leak volume (268.5 ± 177.2 vs. 88.6 ± 99.6 ml, p = .038), and lower percentage of patients with Mallampati Classification IV (16.7 vs. 50.0%, p = .035), compared to the 16 patients who did not tolerate an SV trial. Twenty-two patients with a TTP of ≤ 9 cm H₂O had higher percentage tolerating an SV trial than those with a TTP of > 9 cm H₂O (86.4 vs. 35.3%, p = .002). The in vitro study demonstrated a strong correlation between upper airway patency and TTP, peak inspiratory flow, and tidal volume inhaled from the upper airway. Conclusions TTP, Mallampati classification, and leak volume can be used to assess upper airway patency for adult patients with tracheostomies undergoing an SV trial. A TTP of ≤ 9 cm H₂O might indicate adequate upper airway patency to tolerate the SV trial.

Low-Dose of Rocuronium During Thyroid Surgery: Effects on Intraoperative Nerve-Monitoring and Intubation

BACKGROUND

Intraoperative Neurophysiological Monitoring (IONM) reduces the incidence of Recurrent Laryngeal Nerve (RLN) injuries during thyroid surgery. To preserve nerve function, long acting neuromuscular blocking agents (NMBA) should be avoided. However, NMBA are necessary for laryngoscopy and endotracheal intubation. We designed this double-blinded, randomized, placebo-controlled trial to assess if a low-dose of rocuronium given at intubation would affect the IONM data recorded before the thyroid dissection.

METHODS

Hundred patients undergoing elective thyroid surgery were randomized to receive either 0.3 mg kg^-1 of low dose rocuronium (intervention) or no-NMBA (control). Intubation was performed with video-laryngoscopy. IONM was placed on RLN and nerve stimulation was performed before and after thyroid dissection. The presence of a valid amplitude prior to dissection was defined when the IONM signal was >100 μV. Occurrence of difficult laryngoscopy was reported together with intubation details including time, difficulty and failure. The lowest peripheral saturation (SpO₂) and the number of desaturation episodes during the intubation were also registered.

RESULTS

No patients showed impaired IONM signal before dissection in both groups. Cormack-Lehane grade was higher in the intervention group (1^1;2) compared to control one (1^1;1; P = 0.046). No-NMBA patients had increased number of difficult laryngoscopies (21% versus 6%, P = 0.041) and intubations (34% versus 8%; P = 0.003) as well as a longer time to intubation (78 [55; 175] versus 55 [31; 110] sec; P = 0.006). Lower values of peripheral SpO₂ during intubation attempt were registered in the no NMBA group (99 [97; 100] versus 99 [99; 100] %; P = 0.020). However, the number of intubation failure was similar between groups (p=0.495).

CONCLUSIONS

Low-dose of rocuronium does not compromise pre-dissection IONM signal and improves intubation condition when compared to a relaxant free strategy.

Canadian Airway Focus Group updated consensus-based recommendations for management of the difficult airway: part 2. Planning and implementing safe management of the patient with an anticipated difficult airway

PURPOSE

Since the last Canadian Airway Focus Group (CAFG) guidelines were published in 2013, the published airway management literature has expanded substantially. The CAFG therefore re-convened to examine this literature and update practice recommendations. This second of two articles addresses airway evaluation, decision-making, and safe implementation of an airway management strategy when difficulty is anticipated.

SOURCE

Canadian Airway Focus Group members, including anesthesia, emergency medicine, and critical care physicians were assigned topics to search. Searches were run in the Medline, EMBASE, Cochrane Central Register of Controlled Trials, and CINAHL databases. Results were presented to the group and discussed during video conferences every two weeks from April 2018 to July 2020. These CAFG recommendations are based on the best available published evidence. Where high-quality evidence is lacking, statements are based on group consensus.

FINDINGS AND KEY RECOMMENDATIONS

Prior to airway management, a documented strategy should be formulated for every patient, based on airway evaluation. Bedside examination should seek predictors of difficulty with face-mask ventilation (FMV), tracheal intubation using video- or direct laryngoscopy (VL or DL), supraglottic airway use, as well as emergency front of neck airway access. Patient physiology and contextual issues should also be assessed. Predicted difficulty should prompt careful decision-making on how most safely to proceed with airway management. Awake tracheal intubation may provide an extra margin of safety when impossible VL or DL is predicted, when difficulty is predicted with more than one mode of airway management (e.g., tracheal intubation and FMV), or when predicted difficulty coincides with significant physiologic or contextual issues. If managing the patient after the induction of general anesthesia despite predicted difficulty, team briefing should include triggers for moving from one technique to the next, expert assistance should be sourced, and required equipment should be present. Unanticipated difficulty with airway management can always occur, so the airway manager should have a strategy for difficulty occurring in every patient, and the institution must make difficult airway equipment readily available. Tracheal extubation of the at-risk patient must also be carefully planned, including assessment of the patient's tolerance for withdrawal of airway support and whether re-intubation might be difficult.

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.

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.

Thyromental height test as a new method for prediction of difficult intubation with double lumen tube

Background

Predicting difficult intubation is of high clinical interest.

Methods

237 patients aged ≥18 years were included in the study. Preoperative airway evaluation included: Mallampati test, thyromental distance, sternomental distance and thyromental height test. During direct laryngoscopy Cormack & Lehane classification was graded. We calculated the ROC AUC, sensitivity and specificity for thyromental height test as a primary end point of our study.

Results

Only thyromental height test and Cormack-Lehane scale proved significant on occurrence of difficult intubation. The optimal sensitivity and specificity values of thyromental height test were met with a cut off value of 50 mm. With 1 mm increase in thyromental height test, risk of difficult intubation decreased by 7%.

Conclusion

Thyromental height test is a simple, easy to perform and non-invasive test to predict difficult intubation in patients scheduled for elective double lumen tube intubation during thoracic surgical procedures. With 1 mm above 50 mm increase in thyromental height test the risk of difficult intubation decreased by 7%.

Trial registration

Clinicaltrials.gov Identifier: NCT02988336.

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.