The Simplified Predictive Intubation Difficulty Score: a new weighted score for difficult airway assessment

Spanish Society of Anesthesiology, Reanimation and Pain Therapy (SEDAR), Spanish Society of Emergency and Emergency Medicine (SEMES) and Spanish Society of Otolaryngology, Head and Neck Surgery (SEORL-CCC) Guideline for difficult airway management. Part I

The Airway Management section of the Spanish Society of Anesthesiology, Resuscitation, and Pain Therapy (SEDAR), the Spanish Society of Emergency Medicine (SEMES), and the Spanish Society of Otorhinolaryngology and Head and Neck Surgery (SEORL-CCC) present the Guide for the comprehensive management of difficult airway in adult patients. Its principles are focused on the human factors, cognitive processes for decision-making in critical situations, and optimization in the progression of strategies application to preserve adequate alveolar oxygenation in order to enhance safety and the quality of care. The document provides evidence-based recommendations, theoretical-educational tools, and implementation tools, mainly cognitive aids, applicable to airway management in the fields of anesthesiology, critical care, emergencies, and prehospital medicine. For this purpose, an extensive literature search was conducted following PRISMA-R guidelines and was analyzed using the GRADE methodology. Recommendations were formulated according to the GRADE methodology. Recommendations for sections with low-quality evidence were based on expert opinion through consensus reached via a Delphi questionnaire.

Multivariable prediction models for difficult direct laryngoscopy: Systematic review and literature metasynthesis

CONTEXT

The difficult airway is an important scenario in anaesthesia due to the impact of its potential complications, and the difficulty in predicting its presence in current clinical practice.

METHODS

Systematic review of articles in English and Spanish retrieved from MEDLINE (Ovid), LILACS and EMBASE up to March 2018. The search strategy was defined by the authors. The reviewers uploaded the studies to specially designed tables in order to qualitatively analyse the results of each paper.

RESULTS

A total of 3602 studies were identified. Thirty-four of these were included in the qualitative review. The most commonly used definition of difficulty was the Cormack-Lehane 3 or 4 classification, with a weighted mean incidence of 7.23%. The most relevant finding was the methodological weaknesses in obtaining these scales.

CONCLUSIONS

Available prediction models show limited discrimination, and weaknesses were detected in the methodology used to develop these prediction rules.

Identification of difficult to intubate patients from frontal face images using an ensemble of deep learning models

Failure to identify difficult intubation is the leading cause of anesthesia-related death and morbidity. Despite preoperative airway assessment, 75-93% of difficult intubations are unanticipated, and airway examination methods underperform, with sensitivities of 20-62% and specificities of 82-97%. To overcome these impediments, we aim to develop a deep learning model to identify difficult to intubate patients using frontal face images. We proposed an ensemble of convolutional neural networks which leverages a database of celebrity facial images to learn robust features of multiple face regions. This ensemble extracts features from patient images (n = 152) which are subsequently classified by a respective ensemble of attention-based multiple instance learning models. Through majority voting, a patient is classified as difficult or easy to intubate. Whereas two conventional bedside tests resulted in AUCs of 0.6042 and 0.4661, the proposed method resulted in an AUC of 0.7105 using a cohort of 76 difficult and 76 easy to intubate patients. Generic features yielded AUCs of 0.4654-0.6278. The proposed model can operate at high sensitivity and low specificity (0.9079 and 0.4474) or low sensitivity and high specificity (0.3684 and 0.9605). The proposed ensembled model outperforms conventional bedside tests and generic features. Side facial images may improve the performance of the proposed model. The proposed method significantly surpasses conventional bedside tests and deep learning methods. We expect our model will play an important role in developing deep learning methods where frontal face features play an important role.

Multivariable prediction models for difficult direct laryngoscopy: Systematic review and literature metasynthesis

CONTEXT

The difficult airway is an important scenario in anaesthesia due to the impact of its potential complications, and the difficulty in predicting its presence in current clinical practice.

METHODS

Systematic review of articles in English and Spanish retrieved from MEDLINE (Ovid), LILACS and Embase up to March 2018. The search strategy was defined by the authors. The reviewers uploaded the studies to specially designed tables in order to qualitatively analyse the results of each paper.

RESULTS

A total of 3602 studies were identified. Thirty-four of these were included in the qualitative review. The most commonly used definition of difficulty was the Cormack-Lehane3 or 4 classification, with a weighted mean incidence of 7.23%. The most relevant finding was the methodological weaknesses in obtaining these scales.

CONCLUSIONS

Available prediction models show limited discrimination, and weaknesses were detected in the methodology used to develop these prediction rules.

Effectiveness of simplified predictive intubation difficulty score and thyromental height in head and neck surgeries: an observational study

Background and objectives

In this study, we aimed to investigate the predictive value of different airway assessment tools, including parts of the Simplified Predictive Intubation Difficulty Score (SPIDS), the SPIDS itself and the Thyromental Height Test (TMHT), in intubations defined as difficult by the Intubation Difficulty Score (IDS) in a group of patients who have head and neck pathologies.

Methods

One hundred fifty-three patients who underwent head and neck surgeries were included in the study. The Modified Mallampati Test (MMT) result, Thyromental Distance (TMD), Ratio of the Height/Thyromental Distance (RHTMD), TMHT, maximum range of head and neck motion and mouth opening were measured. The SPIDSs were calculated, and the IDSs were determined.

Results

A total of 25.4% of the patients had difficult intubations. SPIDS scores >10 had 86.27% sensitivity, 71.57% specificity and 91.2% Negative Predictive Value (NPV). The results of the Receiver Operating Curve (ROC) analysis for the airway screening tests and SPIDS revealed that the SPIDS had the highest area under the curve; however, it was statistically similar to other tests, except for the MMT.

Conclusions

The current study demonstrates the practical use of the SPIDS in predicting intubation difficulty in patients with head and neck pathologies. The performance of the SPIDS in predicting airway difficulty was found to be as efficient as those of the other tests evaluated in this study. The SPIDS may be considered a comprehensive, detailed tool for predicting airway difficulty.

[Effectiveness of simplified predictive intubation difficulty score and thyromental height in head and neck surgeries: an observational study]

BACKGROUND AND OBJECTIVES

In this study, we aimed to investigate the predictive value of different airway assessment tools, including parts of the Simplified Predictive Intubation Difficulty Score (SPIDS), the SPIDS itself and the Thyromental Height Test (TMHT), in intubations defined as difficult by the Intubation Difficulty Score (IDS) in a group of patients who have head and neck pathologies.

METHODS

One hundred fifty-three patients who underwent head and neck surgeries were included in the study. The Modified Mallampati Test (MMT) result, Thyromental Distance (TMD), Ratio of the Height/Thyromental Distance (RHTMD), TMHT, maximum range of head and neck motion, and mouth opening were measured. The SPIDSs were calculated, and the IDSs were determined.

RESULTS

A total of 25.4% of the patients had difficult intubations. SPIDS scores > 10 had 86.27% sensitivity, 71.57% specificity and 91.2% Negative Predictive Value (NPV). The results of the Receiver Operating Curve (ROC) analysis for the airway screening tests and SPIDS revealed that the SPIDS had the highest area under the curve; however, it was statistically similar to other tests, except for the MMT.

CONCLUSIONS

The current study demonstrates the practical use of the SPIDS in predicting intubation difficulty in patients with head and neck pathologies. The performance of the SPIDS in predicting airway difficulty was found to be as efficient as those of the other tests evaluated in this study. The SPIDS may be considered a comprehensive, detailed tool for predicting airway difficulty.

Patient-specific and hyper-realistic phantom for an intubation simulator with a replaceable difficult airway of a toddler using 3D printing

Difficult tracheal intubation is the third most common respiratory-related adverse co-morbid episode and can lead to death or brain damage. Since difficult tracheal intubation is less frequent, trainees have fewer opportunities to perform difficult tracheal intubation; this leads to the need to practice with a hyper-realistic intubation simulator. However, conventional simulators are expensive, relatively stiffer than the human airway, and have a lack of diversity in terms of disease variations and anatomic reproducibility. Therefore, we proposed the development of a patient-specific and hyper-realistic difficult tracheal intubation simulator using three-dimensional printing technology and silicone moulding and to test the feasibility of patient-specific and hyper-realistic difficult intubation simulation using 3D phantom for the trainee. This difficult tracheal intubation phantom can provide a realistic simulation experience of managing various difficult tracheal intubation cases to trainees, which could minimise unexpected tissue damage before anaesthesia. To achieve a more realistic simulation, a patient-specific phantom was fabricated to mimic human tissue with realistic mouth opening and accurate difficult airway shape. This has great potential for the medical education and training field.

[Evaluation of bedside tests and proposal of a model for predicting difficult laryngoscopy: an observational prospective study]

BACKGROUND AND OBJECTIVES

The prediction of difficult laryngoscopy is based on tests that assess anatomic characteristics of face and neck. We aimed to identify the most accurate tests and propose a multivariate predictive model.

METHODS

This prospective observational study included 1134 patients. Thyromental Distance (TMD), Sternomental Distance (STMD), Ratio of Height-to-Thyromental Distance (R-H/TMD), Neck Circumference (NC), Ratio of Neck Circumference-to-Thyromental Distance (R-NC/TMD), Hyomental Distance with head in Neutral Position (HMD-NP) and at Maximal Extension (HMD-HE), Ratio of Hyomental Distance at Maximal head extension-to-hyomental distance in neutral position (R-HMD), Mallampati Class (MLC), Upper Lip Bite Test (ULBT), Mouth Opening (MO) and Head Extension (HE) were assessed preoperatively. A Cormack-Lehane Grade ≥ 3 was defined as Difficult Laryngoscopy. Sensitivity, specificity, positive and negative predictive values were assessed for all tests. Multivariate analysis with logistic regression was used to create the predictive models.

RESULTS

A model incorporating MLC, ULBT, HE, HMD-HE and R-NC/TMD showed high prognostic accuracy; x²(5)=109.12, p <0.001, AUC=0.86, p <0.001). Its sensitivity, specificity and negative predictive value were 82.3%, 74.8% and 97.4%, respectively. A second model including two measurements not requiring patient's cooperation (R-NC/TMD and HMD-HE) exhibited good prognostic performance; x²(2)=63.5, p <0.001, AUC=0.77, p <0.001. Among single tests, HE had the highest sensitivity (78.5%) and negative predictive value (96%).

CONCLUSIONS

A five-variable model incorporating MLC, ULBT, HE, HMD-HE and R-NC/TMD showed satisfyingly high predictive value for difficult laryngoscopy. A model including R-NC/TMD and HMD-HE could be useful in incapable patients. The most accurate single predictor was HE.

Are physician assistant and patient airway assessments reliable compared to anesthesiologist assessments in detecting difficult airways in general surgical patients?

Background

Airway management remains one of the most important responsibilities of anesthesiologists. Prediction of difficult airway allows time for proper selection of equipment, technique, and personnel experienced in managing patients with difficult airway. Face to face preoperative anesthesia interviews are difficult to conduct as they necessitate patients traveling to the clinics, and, in practice, are usually conducted in the morning of the procedure by the anesthesiologist, when identification of predictors of difficult intubation may lead to schedule delays or case cancelations. We hypothesized that an airway assessment tool could be used by patients or physician assistants to accurately assess their airways.

Methods

We administered an airway assessment tool, which had been constructed in consultation with a psychometrician and revised after non-medical layperson feedback, to 215 patients presenting to the preoperative clinic for evaluation. Separately, patients had the airway exam performed by a physician assistant and an anesthesiologist. Agreement was compared using kappa.

Results

We found good agreement between observers only on "can you put three fingers in your mouth?" (three-way kappa = .733, p < 0.001) and poor agreement on Mallampati classification (three-way kappa = .195, p < 0.001) and "Can you fit three fingers between your chin and your Adam's Apple?" (three-way kappa = .216, p < 0.001). The agreements for the other questions were mostly fair. Agreements between patients and anesthesiologists were similar to those between physician assistants and anesthesiologists.

Conclusions

Neither the patients' self-assessments nor the physician assistants' assessments were adequate to substitute for the anesthesiologists' airway assessments.

Incidence and severity of postoperative sore throat: a randomized comparison of Glidescope with Macintosh laryngoscope

BACKGROUND

Postoperative sore throat (POST) is a common problem following endotracheal (ET) intubation during general anesthesia. The objective was to compare the incidence and severity of POST during routine intubation with Glidescope (GL) and Macintosh laryngoscope (MCL).

METHODS

One hundred forty adult patients ASA I and II with normal airway, scheduled to undergo elective surgery under GA requiring ET intubation were enrolled in this prospective randomized study and were randomly divided in two groups, GL and MCL. Incidence and severity of POST was evaluated at 0, 6, 12 and 24 h after surgery.

RESULTS

At 0 h, the incidence of POST was more in MCL than GL (n = 41 v.s n = 22, P = 0.001), and also at 6 h after surgery (n = 37 v.s n = 23, P = 0.017). Severity of POST was more at 0, 6 and 12 h after surgery in MCL (P < 0.001, P = 0.001, P = 0.004 respectively).

CONCLUSIONS

Routine use of GL for ET tube placement results in reduction in the incidence and severity of POST compared to MCL.

TRIAL REGISRATION

ClinicalTrials.gov NCT02848365 . Retrospectively Registered (Date of registration: July, 2016).

Tracheal extubation with suction vs. positive pressure during emergence from general anaesthesia in adults: A randomised controlled trial

BACKGROUND

After general anaesthesia (GA) in adults, the optimal tracheal extubation technique (positive pressure or suctioning) remains debated. The primary endpoint of this study was to assess the effects of these techniques on onset time of desaturation (SpO₂<92%).

METHODS

Sixty-nine patients with a body mass index<30 scheduled for elective orthopaedic surgery were allocated to positive pressure (PP) or suctioning (SUC) group. GA was standardised with propofol and remifentanil via target-controlled infusion. A morphine bolus of 0.15mg/kg was administered 20-30mins before the end of surgery. The effect of extubation technique on onset time of desaturation (T92) was assessed during the first 10mins after extubation during the spontaneous air breathing. Secondary endpoints included: frequency of desaturation, respiratory complications, need to use oxygen therapy and SpO₂ at the end of the first hour while breathing in air (ClinicalTrials.gov identifier: NCT01323049).

RESULTS

Baseline patient characteristics and intraoperative management data for the 68 patients included had no relevant clinical difference between groups. T92 (sec) after tracheal extubation was 214 (168) vs. 248 (148) in the PP and SUC groups, respectively (P=0.44). In the PP and SUC groups, 50 and 43% reached a SpO₂<92% within the first 10mins after extubation respectively (P=0.73). There were no statistically significant differences between groups for any secondary endpoints.

CONCLUSIONS

Positive pressure extubation as compared with suctioning extubation did not seem to delay onset time of desaturation after GA in standard weight adult patients.

High levels of IGF-1 predict difficult intubation of patients with acromegaly

PURPOSE

To investigate the characteristics of difficult intubation and identify novel efficient predictors in patients with acromegaly.

METHODS

Patients with either untreated acromegaly or non-functional pituitary adenomas were enrolled. Patients with acromegaly underwent hormone assays, upper airway computed tomography and magnetic resonance imaging examinations and preoperative overnight polysomnography. The modified Mallampati classification, mouth opening, neck circumference, and neck extension were assessed, and the Cormack-Lehane grades and the time of tracheal intubation were recorded.

RESULTS

Patients with acromegaly had a higher incidence of difficult intubation (62.5%). The time of tracheal intubation was prolonged, the neck circumference was enlarged, and the neck extension was confined. In patients with acromegaly and difficult intubation, the insulin-like growth factor 1 levels and apnea/hypoxia index were significantly higher compared to patients without difficult intubation (1115.40 ± 253.73 vs. 791.67 ± 206.62 ng/ml, P = 0.020; 22.17 ± 23.25 vs. 2.47 ± 2.84, P = 0.026, respectively). The bilateral regression analysis revealed that high levels of insulin-like growth factor 1 were an independent risk factor for developing difficult intubation (p = 0.042, Exp B = 1.006). The modified Mallampati classification was positively correlated with apnea/hypoxia index and could be calculated using the following logarithmic equation: MMC = 0.2982 * ln (AHI) + 2.1836.

CONCLUSIONS

In patients with acromegaly, neck movement is confined, the time of tracheal intubation is prolonged, and the neck circumference is enlarged, and these patients suffer from an increased incidence of difficult intubation (62.5%) during anesthesia induction. The apnea/hypoxia index and insulin-like growth factor 1 levels are both increased in acromegalic patients with difficult intubation, and elevated insulin-like growth factor 1 levels are an independent risk factor of difficult intubation in acromegalic patients.

Avoidance versus use of neuromuscular blocking agents for improving conditions during tracheal intubation or direct laryngoscopy in adults and adolescents

BACKGROUND

Tracheal intubation during induction of general anaesthesia is a vital procedure performed to secure a patient's airway. Several studies have identified difficult tracheal intubation (DTI) or failed tracheal intubation as one of the major contributors to anaesthesia-related mortality and morbidity. Use of neuromuscular blocking agents (NMBA) to facilitate tracheal intubation is a widely accepted practice. However, because of adverse effects, NMBA may be undesirable. Cohort studies have indicated that avoiding NMBA is an independent risk factor for difficult and failed tracheal intubation. However, no systematic review of randomized trials has evaluated conditions for tracheal intubation, possible adverse effects, and postoperative discomfort.

OBJECTIVES

To evaluate the effects of avoiding neuromuscular blocking agents (NMBA) versus using NMBA on difficult tracheal intubation (DTI) for adults and adolescents allocated to tracheal intubation with direct laryngoscopy. To look at various outcomes, conduct subgroup and sensitivity analyses, examine the role of bias, and apply trial sequential analysis (TSA) to examine the level of available evidence for this intervention.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, BIOSIS, International Web of Science, LILACS, advanced Google, CINAHL, and the following trial registries: Current Controlled Trials; ClinicalTrials.gov; and www.centerwatch.com, up to January 2017. We checked the reference lists of included trials and reviews to look for unidentified trials.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared the effects of avoiding versus using NMBA in participants 14 years of age or older.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data independently. We conducted random-effects and fixed-effect meta-analyses and calculated risk ratios (RRs) and their 95% confidence intervals (CIs). We used published data and data obtained by contacting trial authors. To minimize the risk of systematic error, we assessed the risk of bias of included trials. To reduce the risk of random errors caused by sparse data and repetitive updating of cumulative meta-analyses, we applied TSA.

MAIN RESULTS

We identified 34 RCTs with 3565 participants that met our inclusion criteria. All trials reported on conditions for tracheal intubation; seven trials with 846 participants described 'events of upper airway discomfort or injury', and 13 trials with 1308 participants reported on direct laryngoscopy. All trials used a parallel design. We identified 18 dose-finding studies that included more interventions or control groups or both. All trials except three included only American Society of Anesthesiologists (ASA) class I and II participants, 25 trials excluded participants with anticipated DTI, and obesity or overweight was an excluding factor in 13 studies. Eighteen trials used suxamethonium, and 18 trials used non-depolarizing NMBA.Trials with an overall low risk of bias reported significantly increased risk of DTI with no use of NMBA (random-effects model) (RR 13.27, 95% CI 8.19 to 21.49; P < 0.00001; 508 participants; four trials; number needed to treat for an additional harmful outcome (NNTH) = 1.9, I² = 0%, D² = 0%, GRADE = moderate). The TSA-adjusted CI for the RR was 1.85 to 95.04. Inclusion of all trials resulted in confirmation of results and of significantly increased risk of DTI when an NMBA was avoided (random-effects model) (RR 5.00, 95% CI 3.49 to 7.15; P < 0.00001; 3565 participants; 34 trials; NNTH = 6.3, I² = 70%, D² = 82%, GRADE = low). Again the cumulative z-curve crossed the TSA monitoring boundary, demonstrating harmful effects of avoiding NMBA on the proportion of DTI with minimal risk of random error. We categorized only one trial reporting on upper airway discomfort or injury as having overall low risk of bias. Inclusion of all trials revealed significant risk of upper airway discomfort or injury when an NMBA was avoided (random-effects model) (RR 1.37, 95% CI 1.09 to 1.74; P = 0.008; 846 participants; seven trials; NNTH = 9.1, I² = 13%, GRADE = moderate). The TSA-adjusted CI for the RR was 1.00 to 1.85. None of these trials reported mortality. In terms of our secondary outcome 'difficult laryngoscopy', we categorized only one trial as having overall low risk of bias. All trials avoiding NMBA were significantly associated with difficult laryngoscopy (random-effects model) (RR 2.54, 95% CI 1.53 to 4.21; P = 0.0003; 1308 participants; 13 trials; NNTH = 25.6, I² = 0%, D²= 0%, GRADE = low); however, TSA showed that only 6% of the information size required to detect or reject a 20% relative risk reduction (RRR) was accrued, and the trial sequential monitoring boundary was not crossed.

AUTHORS' CONCLUSIONS

This review supports that use of an NMBA may create the best conditions for tracheal intubation and may reduce the risk of upper airway discomfort or injury following tracheal intubation. Study results were characterized by indirectness, heterogeneity, and high or uncertain risk of bias concerning our primary outcome describing difficult tracheal intubation. Therefore, we categorized the GRADE classification of quality of evidence as moderate to low. In light of defined outcomes of individual included trials, our primary outcomes may not reflect a situation that many clinicians consider to be an actual difficult tracheal intubation by which the patient's life or health may be threatened.

Evaluation of the reliability of preoperative descriptive airway assessment tests in prediction of the Cormack-Lehane score: A prospective randomized clinical study

STUDY OBJECTIVE

In this study we investigated and compared the predictive values of different airway assessments tests including thyromental height measurement test, which has been recently suggested, in difficult laryngoscopy (Cormack and Lehane [C-L] scores 3 and 4). In addition, we compared the effectiveness of methods and C-L scores, by IDS, in terms of predicting difficult intubation.

DESIGN

Prospective, blinded study.

SETTING

Maltepe University.

PATIENTS

Four hundred fifty-one patients selected randomly who underwent general anesthesia.

INTERVENTIONS

In this study we compared predictive value of thyromental height measurement test (TMH), which has been recently suggested, modified Mallampati test (MMT), upper lip bite test (ULBT), and thyromental distance measurement test (TMD) in difficult laryngoscopy. Final C-L scores were compared with intubation difficulty scale (IDS) in terms of predicting difficult intubation.

MEASUREMENTS

Patient's American Society of Anesthesiology score, age and weight were recorded. TMH, TMD, MMT, ULBT, IDS and C-L scores were measured and determined.

MAIN RESULTS

The optimal cut-off point for TMH for predicting difficult laryngoscopy was 43.5 mm and for TMD was 82.06 mm. Use of TMH <43.5 with MMT has the highest sensitivity for predicting difficult intubation (78.38) with 75.36% specificity and 97.50% negative predictive value. TMH showed sensitivity of 91.89% and specificity 52.17% at 50 mm cut-off value. In the comparison of the area under the receiver operating characteristic curve values, none of the tests came forth individually or in combination with MMT test.

CONCLUSIONS

The present study demonstrates the practicality of TMH as a digitalized test however the clinical benefits of TMH in daily medical practice are drawn into question. The additional variable of race may have had some bearing on this and further studies, larger in patient sample size, may need to use different methodology concerning age-, sex-, and race-dependent variables in evaluating these tests.

Head-Elevated Patient Positioning Decreases Complications of Emergent Tracheal Intubation in the Ward and Intensive Care Unit

BACKGROUND

Based on the data from elective surgical patients, positioning patients in a back-up head-elevated position for preoxygenation and tracheal intubation can improve patient safety. However, data specific to the emergent setting are lacking. We hypothesized that back-up head-elevated positioning would be associated with a decrease in complications related to tracheal intubation in the emergency room environment.

METHODS

This retrospective study was approved by the University of Washington Human Subjects Division (Seattle, WA). Eligible patients included all adults undergoing emergent tracheal intubation outside of the operating room by the anesthesiology-based airway service at 2 university-affiliated teaching hospitals. All intubations were through direct laryngoscopy for an indication other than full cardiopulmonary arrest. Patient characteristics and details of the intubation procedure were derived from the medical record. The primary study endpoint was the occurrence of a composite of any intubation-related complication: difficult intubation, hypoxemia, esophageal intubation, or pulmonary aspiration. Multivariable logistic regression was used to estimate the odds of the primary endpoint in the supine versus back-up head-elevated positions with adjustment for a priori-defined potential confounders (body mass index and a difficult intubation prediction score [Mallampati, obstructive sleep Apnea, Cervical mobility, mouth Opening, Coma, severe Hypoxemia, and intubation by a non-Anesthesiologist score]).

RESULTS

Five hundred twenty-eight patients were analyzed. Overall, at least 1 intubation-related complication occurred in 76 of 336 (22.6%) patients managed in the supine position compared with 18 of 192 (9.3%) patients managed in the back-up head-elevated position. After adjusting for body mass index and the Mallampati, obstructive sleep Apnea, Cervical mobility, mouth Opening, Coma, severe Hypoxemia, and intubation by a non-Anesthesiologist score, the odds of encountering the primary endpoint during an emergency tracheal intubation in a back-up head-elevated position was 0.47 (95% confidence interval, 0.26-0.83; P = 0.01).

CONCLUSIONS

Placing patients in a back-up head-elevated position, compared with supine position, during emergency tracheal intubation was associated with a reduced odds of airway-related complications.

[Post analysis simulated correlation of the El-Ganzouri airway difficulty score with difficult airway]

BACKGROUND

Difficult airway (DA) occurs frequently (5-15%) in clinical practice. The El-Ganzouri Risk Index (EGRI) has a high sensitivity for predicting a difficult intubation (DI). However difficult mask ventilation (DMV) was never included in the EGRI. Since DMV was not included in the EGRI assessment, and obstructive sleep apnea (OSA) is also correlated with DMV, a study correlating the prediction of DA and OSA (identified by STOP-Bang questionnaire, SB) seemed important.

METHODS

We accessed a database previously collected for a post analysis simulation of the airway difficulty predictivity of the EGRI, associated with normal and difficult airway, particularly DMV. As secondary aim, we measured the correlation between the SB prediction system and DA, compared to the EGRI.

RESULTS

A total of 2747 patients were included in the study. The proportion of patients with DI was 14.7% (95% CI 13.4-16) and the proportion of patients with DMV was 3.42% (95% CI 2.7-4.1). The incidence of DMV combined with DI was (2.3%). The optimal cutoff value of EGRI was 3. EGRI registered also an higher ability to predict DMV (AUC=0.76 (95% CI 0.71-0.81)). Adding the SB variables in the logistic model, the AUC increases with the inclusion of "observed apnea" variable (0.83 vs. 0.81, p=0.03). The area under the ROC curve for the patients with DI and DMV was 0.77 (95% CI 0.72-0.83).

CONCLUSIONS

This study confirms that the incidence of DA is not negligible and suggests the use of the EGRI as simple bedside predictive score to improve patient safety.

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.

Prospective validation of the modified LEMON criteria to predict difficult intubation in the ED

BACKGROUND

Evidence to predict difficult intubation remains scarce in the emergency department (ED) setting. A previously defined clinical decision rule, the modified LEMON criteria, may provide a reliable and reproducible means of identifying difficult intubations. We aimed to prospectively evaluate the external validity of the modified LEMON criteria in the EDs.

METHODS

We conducted a 13-center prospective observational study, the second Japanese Emergency Airway Network study. We prospectively collected data on all patients undergoing intubations in the ED from February 2012 through September 2014. The primary outcomes were sensitivity, specificity, and predictive values of the modified LEMON criteria for predicting difficult intubation (≥2 attempts by emergency attending physicians or anesthesiologists).

RESULTS

The database recorded a total of 4034 encounters (capture rate, 96%) in the EDs. Of these, 3313 patients (84%) underwent the intubation attempt with a direct laryngoscope and 610 patients (16%) with a video laryngoscope. The proportion of difficult intubation was 5.4% (95% confidence interval [CI], 4.7%-6.2%) in the direct laryngoscope group and 7.4% (95% CI, 5.6%-9.7%) in the video laryngoscope group. The sensitivity was 85.7% (95% CI, 79.3%-90.4%) with direct laryngoscope and 94.9% (95% CI, 83.5%-98.6%) with video laryngoscope. The specificity was 47.6% (95% CI, 47.2%-47.9%) and 40.3% (95% CI, 39.4%-40.6%), respectively. The negative predictive value was 98.2% (95% CI, 97.5%-98.8%) and 99.0% (95% CI, 96.6%-99.7%), respectively.

CONCLUSIONS

In this multicenter prospective study, we found a high sensitivity and a negative predictive value of the modified LEMON criteria for predicting difficult intubation. The modified LEMON might assist ED providers in better identifying difficult intubations.

Comparing ease of intubation in obese and lean patients using intubation difficulty scale

Background:

Difficult tracheal intubation contributes to significant morbidity and mortality during induction of anesthesia. There are divided opinions regarding ease of intubation in obese patients. Moreover, the definition of difficult intubation is not uniform; hence we have use the Intubation Difficulty Scale (IDS) to find the incidence of difficult intubation in obese patients.

Aims:

The primary aim of the following study is to find out the incidence of difficult intubation in obese and lean patients using IDS and secondary aim is to assess the performance of bedside screening tests to predict difficult intubation, mask ventilation and laryngoscopy in obese and lean patients.

Materials and Methods:

A prospective, observational cohort study of 200 patients requiring general anesthesia were categorized into 100 each based on body mass index (BMI) into lean (BMI <25 kg/m²) and obese (BMI ≥25 kg/m²) groups. IDS score ≥5 was termed as difficult intubation. Pre-operative airway assessment included Mallampati score, mouth opening, neck circumference (NC), upper lip bite test, thyromental distance, sternomental distance (SMD) and head neck mobility. Patients having difficulty in mask ventilation and laryngoscopy was recorded.

Results:

Over all in 200 patients the incidence of difficult intubation was 9%. Obese patients were slightly more difficult to intubate than lean (11% vs. 7%, P = 0.049). Age >40 years, NC >35 cm, SMD <12.5 cm and restricted head neck mobility were factors which were associated with IDS ≥5. Multivariate analysis revealed SMD <12.5 cm to predict difficult intubation in obese patients. Obese patients were difficult to mask ventilate (6% vs. 1%, P = 0.043). There was no difference regarding grading of laryngoscopy between the two groups.

Conclusion:

Obese patients are difficult to mask ventilate and intubate. During intubation of obese patients who is more than 40 years age and SMD <12.5 cm, it is preferable to have a second skilled anesthesiologist.

Application of process improvement principles to increase the frequency of complete airway management documentation

BACKGROUND

Process improvement in healthcare delivery settings can be difficult, even when there is consensus among clinicians about a clinical practice or desired outcome. Airway management is a medical intervention fundamental to the delivery of anesthesia care. Like other medical interventions, a detailed description of the management methods should be documented. Despite this expectation, airway documentation is often insufficient. The authors hypothesized that formal adoption of process improvement methods could be used to increase the rate of "complete" airway management documentation.

METHODS

The authors defined a set of criteria as a local practice standard of "complete" airway management documentation. The authors then employed selected process improvement methodologies over 13 months in three iterative and escalating phases to increase the percentage of records with complete documentation. The criteria were applied retrospectively to determine the baseline frequency of complete records, and prospectively to measure the impact of process improvements efforts over the three phases of implementation.

RESULTS

Immediately before the initial intervention, a retrospective review of 23,011 general anesthesia cases over 6 months showed that 13.2% of patient records included complete documentation. At the conclusion of the 13-month improvement effort, documentation improved to a completion rate of 91.6% (P<0.0001). During the subsequent 21 months, the completion rate was sustained at an average of 90.7% (SD, 0.9%) across 82,571 general anesthetic records.

CONCLUSION

Systematic application of process improvement methodologies can improve airway documentation and may be similarly effective in improving other areas of anesthesia clinical practice.

Post analysis simulated correlation of the El-Ganzouri airway difficulty score with difficult airway

BACKGROUND

Difficult airway (DA) occurs frequently (5-15%) in clinical practice. The El-Ganzouri Risk Index (EGRI) has a high sensitivity for predicting a difficult intubation (DI). However difficult mask ventilation (DMV) was never included in the EGRI. Since DMV was not included in the EGRI assessment, and obstructive sleep apnea (OSA) is also correlated with DMV, a study correlating the prediction of DA and OSA (identified by STOP-Bang questionnaire, SB) seemed important.

METHODS

We accessed a database previously collected for a post analysis simulation of the airway difficulty predictivity of the EGRI, associated with normal and difficult airway, particularly DMV. As secondary aim, we measured the correlation between the SB prediction system and DA, compared to the EGRI.

RESULTS

A total of 2747 patients were included in the study. The proportion of patients with DI was 14.7% (95% CI 13.4-16) and the proportion of patients with DMV was 3.42% (95% CI 2.7-4.1). The incidence of DMV combined with DI was (2.3%). The optimal cutoff value of EGRI was 3. EGRI registered also an higher ability to predict DMV (AUC=0.76 (95% CI 0.71-0.81)). Adding the SB variables in the logistic model, the AUC increases with the inclusion of "observed apnea" variable (0.83 vs. 0.81, p=0.03). The area under the ROC curve for the patients with DI and DMV was 0.77 (95% CI 0.72-0.83).

CONCLUSIONS

This study confirms that the incidence of DA is not negligible and suggests the use of the EGRI as simple bedside predictive score to improve patient safety.

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.

Validation of modified Mallampati test with addition of thyromental distance and sternomental distance to predict difficult endotracheal intubation in adults

Background and Aims:

Intubation is often a challenge for anaesthesiologists. Many parameters assist to predict difficult intubation. The present study was undertaken to assess the validity of different parameters in predicting difficult intubation for general anaesthesia (GA) in adults and effect of combining the parameters on the validity.

Methods:

The anaesthesiologist assessed oropharynx of 135 adult patients. Modified Mallampati test (MMT) was used and the thyromental distance (TMD) and sternomental distances (SMD) for each of the patients were also measured. The Cormack and Lehane laryngoscopic grading was assessed following laryngoscopy. The validity parameters such as sensitivity, specificity, false positive and negatives values, positive and negative predictive values were calculated. The effect of combining different measurements on the validity was also studied. Univariate analysis was performed using the parametric method.

Results:

The study group comprised of 135 patients. The sensitivity and specificity of MMT were 28.6% and 93%, respectively. The TMD (<6.5 CM) had sensitivity and specificity of 100% and 75.8%, respectively. The SMD (<12.5 CM) had sensitivity and specificity of 91% and 92.7%, respectively. Combination of MMT grading and TMD and SMD measurements increased the validity (sensitivity of 100% and specificity of 92.7%).

Conclusion:

MMT had high specificity. The validity of combination of MMT, SMD and TMD as compared to MMT alone was very high in predicting difficult intubation in adult patients. All parameters should be used in assessing an adult patient for surgery under GA.

The importance of subjective facial appearance on the ability of anesthesiologists to predict difficult intubation

BACKGROUND

Previously we demonstrated that a computer algorithm based on bedside airway examinations and facial photographs accurately classified easy and difficult airways. The extent of the ability of anesthesiologists to perform the same task is unknown. We hypothesized that providing photographs would add to the predictive ability of anesthesiologists over that achieved when provided only with the Mallampati (MP) score and the thyromental distance (TMD). We further hypothesized that human observers would implicitly bias their predictions toward more sensitive determination of difficult airways, rather than more specific determination of easy airways.

METHODS

Residents, fellows, and attending anesthesiologists with varying levels of experience (N = 160) were presented with MP and TMD information from 80 Caucasian men subjects. The same subjects' data, accompanied by 3 facial photographs in head-on and right and left profiles, were also presented. Anesthesiologists classified the airways as easy or difficult according to specified criteria ("easy" defined as a single attempt with a Macintosh 3 blade resulting in a grade 1 laryngoscopic view; "difficult" defined as >1 attempt by an operator with at least 12 months anesthesia experience, grade 3 or 4 laryngoscopic view, need for a second operator, or nonelective use of an alternative airway device). Accuracy, sensitivity, and specificity were calculated for each anesthesiologist. We further developed a cost function to quantify a relative bias toward avoiding an unexpectedly difficult intubation versus overpreparing for an easy intubation.

RESULTS

One hundred sixty respondents completed the study. Presenting photographs improved respondents' sensitivity and accuracy in classifying airways, though specificity decreased slightly. Overall accuracy when given photographs was 61.6% (95% confidence interval, 60.8%-62.4%), which was significantly lower than the computer's performance of 87.5% (t test, P < 0.0001). Presentation of photographs, compared with MP and TMD alone, caused anesthesiologists to change their prediction from easy to difficult more frequently if the patients were obese (weight or body mass index), despite not having data on weight or height available. The cost function demonstrated that anesthesiologists strongly preferred to enhance sensitivity (detecting difficult airways) as compared with specificity (detecting easy airways), with a ratio of 6.5:1 (95% confidence interval, 4.9:1-8.4:1).

CONCLUSIONS

Anesthesiologists can derive useful information from facial appearance that enhances the prediction of a difficult airway over that achieved when presented with MP and TMD data alone. Anesthesiologists implicitly bias their predictions toward detection of difficult airways, compared with the true incidence of difficult airways, at the expense of accuracy and specificity. This behavior may be rational for cognitive tasks in which the costs of failure are strongly asymmetric.

Anticipation of the difficult airway: preoperative airway assessment, an educational and quality improvement tool

BACKGROUND

Assessment of the potentially difficult airway (DA) is a critical aspect of resident education. We investigated the impact of a new assessment form on airway prediction and management by anaesthesia residents. We hypothesized that residents would demonstrate improvement in evaluation of DAs over the study duration.

METHODS

After IRB approval, anaesthesia residents were randomized into two groups: control (existing form) and experimental (new form). Data were collected prospectively from August 2008 to May 2010 on all non-obstetric adult patients undergoing non-emergent surgery.

RESULTS

Eight thousand three hundred and sixty-four independent preoperative assessments were collected and 8075 were analysed. The experimental group had the higher completion rate than the control group (94.3% vs 84.3%, P=0.001). DA prediction was higher for the control group (71.2%) compared with the experimental group (69.1%; P=0.032). A significant improvement in prediction rates was found over time for the experimental group (likelihood estimate=0.00068, P=0.031).

CONCLUSIONS

The use of a comprehensive airway assessment did not improve resident ability to predict a DA in an academic, tertiary-based hospital, anaesthesiology residency training programme.

Poor prognostic value of the modified Mallampati score: a meta-analysis involving 177 088 patients

The modified Mallampati score is used to predict difficult tracheal intubation. We have conducted a meta-analysis of published studies to evaluate the Mallampati score as a prognostic test. A total of 55 studies involving 177 088 patients were included after comprehensive electronic and manual searches. The pooled estimates from the meta-analyses were calculated based on a random-effects model and a summary receiver operating curve. Meta-regression analyses were performed to explore sources of possible heterogeneity between the studies. The summary receiver operating curve demonstrated an area under the curve of 0.75. The pooled odds ratio for a difficult intubation with a modified Mallampati score of III or IV was 5.89 [95% confidence interval (CI), 4.74-7.32]. The pooled estimates of the specificity and sensitivity were 0.91 (CI, 0.91-0.91) and 0.35 (CI, 0.34-0.36), respectively. The pooled positive and negative likelihood ratios were 4.13 (CI, 3.60-4.66) and 0.70 (CI, 0.65-0.75), respectively. The meta-analyses had statistical and clinical heterogeneity ranging from 87.2% to 99.4%. Meta-regression analyses did not identify any significant explanation of the heterogeneity. We conclude that the prognostic value of the modified Mallampati score was worse than that estimated by previous meta-analyses. Our assessment shows that the modified Mallampati score is inadequate as a stand-alone test of a difficult laryngoscopy or tracheal intubation, but it may well be a part of a multivariate model for the prediction of a difficult tracheal intubation.

A simplified risk score to predict difficult intubation: development and prospective evaluation in 3763 patients

BACKGROUND AND OBJECTIVE

Despite the presence of numerous preoperative tests to predict a difficult airway, there is no reliable bedside method. The aim of this study was to create and verify a simplified risk model with an acceptable discriminating power.

METHODS

A total of 3763 patients from two university hospitals were screened for potential risk factors for difficult intubation, defined as needing additional technical or human resources, more than three attempts or duration more than 10 min. A random sample (n = 2509) was subjected to multivariate stepwise logistic regression analysis, and the most powerful independent risk factors were used to build a simplified model that was applied to a validation dataset (n = 1254).

RESULTS

The following factors (odds ratio) were associated with a difficult intubation: presence of upper front teeth (3.61), history of difficult intubation (2.88), any Mallampati status different from '1' (2.55) or equal to '4' (1.91) and mouth opening less than 4 cm (1.80). The discriminating power of the score was 0.72 (95% confidence interval 0.63-0.81). The likelihood for a difficult intubation increases continuously from 0 (when no risk factor is present) to 2, 4, 8 and 17%, when one, two, three and more than three factors are present.

CONCLUSION

The new simplified multivariate risk score for difficult intubation may prove to be useful in clinical practice for predicting a difficult airway. Presence of upper front teeth, a history of difficult intubation, any Mallampati status different from '1' and equal to '4' and mouth opening less than 4 cm are independent risk factors for difficult endotracheal intubation. With each of these risk factors, the likelihood increases from 0 (when no risk factor is present) to 17% (when four or five factors are present).