Comparison between different tests and their combination for prediction of difficult intubation: An analytical study

Evaluation of preoperative difficult airway prediction methods for adult patients without obvious airway abnormalities: a systematic review and meta-analysis

BACKGROUND

This systematic review aims to assist clinical decision-making in selecting appropriate preoperative prediction methods for difficult tracheal intubation by identifying and synthesizing literature on these methods in adult patients undergoing all types of surgery.

METHODS

A systematic review and meta-analysis were conducted following PRISMA guidelines. Comprehensive electronic searches across multiple databases were completed on March 28, 2023. Two researchers independently screened, selected studies, and extracted data. A total of 227 articles representing 526 studies were included and evaluated for bias using the QUADAS-2 tool. Meta-Disc software computed pooled sensitivity (SEN), specificity (SPC), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR). Heterogeneity was assessed using the Spearman correlation coefficient, Cochran's-Q, and I2 index, with meta-regression exploring sources of heterogeneity. Publication bias was evaluated using Deeks' funnel plot.

RESULTS

Out of 2906 articles retrieved, 227 met the inclusion criteria, encompassing a total of 686,089 patients. The review examined 11 methods for predicting difficult tracheal intubation, categorized into physical examination, multivariate scoring system, and imaging test. The modified Mallampati test (MMT) showed a SEN of 0.39 and SPC of 0.86, while the thyromental distance (TMD) had a SEN of 0.38 and SPC of 0.83. The upper lip bite test (ULBT) presented a SEN of 0.52 and SPC of 0.84. Multivariate scoring systems like LEMON and Wilson's risk score demonstrated moderate sensitivity and specificity. Imaging tests, particularly ultrasound-based methods such as the distance from the skin to the epiglottis (US-DSE), exhibited higher sensitivity (0.80) and specificity (0.77). Significant heterogeneity was identified across studies, influenced by factors such as sample size and study design.

CONCLUSION

No single preoperative prediction method shows clear superiority for predicting difficult tracheal intubation. The evidence supports a combined approach using multiple methods tailored to specific patient demographics and clinical contexts. Future research should focus on integrating advanced technologies like artificial intelligence and deep learning to improve predictive models. Standardizing testing procedures and establishing clear cut-off values are essential for enhancing prediction reliability and accuracy. Implementing a multi-modal predictive approach may reduce unanticipated difficult intubations, improving patient safety and outcomes.

Society of Family Planning clinical recommendations: Pain control in surgical abortion part 2 - Moderate sedation, deep sedation, and general anesthesia

Analgesic options for surgical abortion (also called procedural abortion) beyond local anesthesia and minimal sedation include moderate sedation, deep sedation and general anesthesia. These clinical recommendations review the effectiveness of various moderate sedation, deep sedation, and general anesthesia regimens for pain control during abortion; medication regimens used to induce analgesia and anesthesia; patient factors affecting anesthesia safety; preoperative and intraoperative protocols to reduce anesthesia risks; personnel qualifications for administration; recommended patient monitoring protocols; and general risks of anesthesia in the context of abortion care. The scope of these recommendations is based on limited available evidence and considerably relies on existing professional society guidelines and recommendations developed by content experts and reviewers. Further research to compare the efficacy and safety of different regimens is needed.

Comparison of sensitivity, specificity, and accuracy of Wilson's score and intubation prediction score for prediction of difficult airway in an eastern Indian population-A prospective single-blind study

Introduction:

Unidentified difficult airway leads to significant adverse events and therefore prediction of a difficult airway is of importance. Independent bedside tests for the prediction of a difficult airway have poor accuracy. The airway assessment scores have not gained popularity as they are cumbersome to perform at the bedside. They also have a varying degree of interobserver variability because of their subjective parameters. Therefore, there is a need to search for a simple score with objective parameters that can be performed at the bedside.

Aim:

To determine the diagnostic accuracy of the Wilson score andiIntubation prediction score for predicting difficult airway in the Eastern Indian population.

Material and Method:

A prospective single-blind study was done including 150 consecutive patients, ASA grade I and II between the ages of 18 and 70 years, undergoing surgery requiring general anesthesia with endotracheal intubation. Preoperatively, the airway was assessed in all patients using Wilson Score and Intubation Prediction Score. General anesthesia with endotracheal intubation was done in all patients. The airway was assessed for ease laryngoscopy and intubation using the Intubation Difficulty Scale. An IDS >5 was taken as difficult airway. The sensitivity, specificity, PPV, NPV, and accuracy of the two predictive tests to predict a difficult was calculated.

Results:

The sensitivity, positive predictive value and accuracy of Intubation Prediction Score was 77.8%, 58.3%and 90.7% respectively as compared to 38.9%, 25.95% and 78.33% respectively of Wilsons score.

Conclusion:

Intubation Prediction score with its objective parameters can be preferred as a simple and accurate bedside test to predict a difficult airway in an Eastern Indian population.

A Comparative Evaluation of Hemodynamic Response and Ease of Intubation using Airtraq and McCoy Laryngoscope

Background:

Various airway gadgets have been devised to overcome difficult airway scenario in anesthesia practice. It includes simple rigid laryngoscope to complex fiber-optic intubating devices; however, there is weak evidence to support the superiority of one device over the other.

Aims and Objective:

The ease of intubation, time and the hemodynamic variability between two groups during intubation are considered as the primary outcome measures.

Materials and Methods:

In this prospective study, 60 patients of either sex undergoing elective surgery who required tracheal intubation were included. All the patients of age between 20 and 50 years with the American Society of Anesthesiologists Classes I and II were divided into the following two groups: Group AT (n = 30): the intubation was performed using AT laryngoscope and Group-MC (n = 30); the intubation was performed using MC laryngoscope. The following intubating parameters were recorded: ease of intubation (Grade-I–IV), mean time of laryngoscopy and intubation, Cormack–Lehane grade, and the percentage of glottis opening (POGO) score. The vital parameters such as heart rate (HR) and mean arterial blood pressure (MABP) were recorded only after premedication, and it was taken as the baseline value. These parameters were again recorded at 1 min, 3 min, 5 min, and 10 min after laryngoscopy and intubation. The incidences of sore throat were recorded just before discharge from the recovery room till 24 h of surgery. All these parameters were compared between these two groups using the Student's t-test and Chi-square test.

Results:

There was no significant difference in age, sex, weight, and Mallampati grading between the two groups. More than 30% of patients in Group AT were intubated without an external aid than the Group MC (P < 0.05). In Group AT, the mean time of intubation was 13.5 ± 5.72 s when compared to 15.63 ± 7.28 s in Group MC (P > 0.05). The Cormack–Lehane grade and POGO score were better in the AT group than that of the MC group. The HR at 1 min in Group AT was 101.83 ± 14.50 and in Group MC, it was 108.93 ± 12.86 (P < 0.05) and after 3 min, it was 98.66 ± 12.60 and 111.53 ± 11.67 (P < 0.05), respectively. The MABP was 107.17 ± 9.03 in Group AT compared to 116 ± 10.12 in Group MC (P < 0.05) at 1 min postintubation. The incidences of sore throat were similar in both the groups.

Conclusion:

The AT laryngoscope is better than MC in terms of the ease of intubation, better glottis view, and hemodynamic stability. However, the incidences of sore throat in both groups were comparable.

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.

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

Background:

Various anatomical measurements and noninvasive clinical tests, singly or in various combinations can be performed to predict difficult intubation. Upper lip bite test (ULBT) and ratio of height to thyromental distance (RHTMD) are claimed to have high predictability. Hence, we have conducted this study to compare the predictive value of ULBT and RHTMD with the following parameters: Mallampati grading, inter-incisor gap, thyromental distance, sternomental distance, head and neck movements, and horizontal length of mandible for predicting difficult intubation.

Materials and Methods:

In this single blinded, prospective, observational study involving 170 adult patients of either sex belonging to American Society of Anesthesiologists physical Status I–III scheduled to undergo general anesthesia were recruited. All patients were subjected to the preoperative airway assessment and, the above parameters were recorded correlated with Cormack and Lehane grade and analyzed. The number of intubation attempts and use of intubation aids were also noted.

Results:

ULBT and RHTMD had highest sensitivity (96.64%, 90.72%), specificity (82.35%, 80.39%), positive predictive value (92.74%, 91.53%), and negative predictive value (91.3%, 78.8%), respectively, compared to other parameters. While odds ratio and likelihood ratio >1 for all the tests.

Conclusion:

ULBT can be used as a simple bedside screening test for prediction of difficult intubation, but it should be combined with other airway assessment tests for better airway predictability. RHTMD can also be used as an acceptable alternative.