Prediction of difficult mask ventilation using a systematic assessment of risk factors vs. existing practice - a cluster randomised clinical trial in 94,006 patients

Preoperative assessment of adults undergoing elective noncardiac surgery: Updated guidelines from the European Society of Anaesthesiology and Intensive Care

BACKGROUND

When considering whether a patient is fit for surgery, a comprehensive patient assessment represents the first step for an anaesthetist to evaluate the risks associated with the procedure and the patient's underlying diseases, and to optimise (whenever possible) the perioperative surgical journey. These guidelines from the European Society of Anaesthesiology and Intensive Care Medicine (ESAIC) update previous guidelines to provide new evidence on existing and emerging topics that consider the different aspects of the patient's surgical path.

DESIGN

A comprehensive literature review focused on organisation, clinical facets, optimisation and planning. The methodological quality of the studies included was evaluated using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) methodology. A Delphi process agreed on the wording of recommendations, and clinical practice statements (CPS) supported by minimal evidence. A draft version of the guidelines was published on the ESAIC website for 4 weeks, and the link was distributed to all ESAIC members, both individual and national, encompassing most European national anaesthesia societies. Feedback was gathered and incorporated into the guidelines accordingly. Following the finalisation of the draft, the Guidelines Committee and ESAIC Board officially approved the guidelines.

RESULTS

In the first phase of the guidelines update, 17 668 titles were initially identified. After removing duplicates and restricting the search period from 1 January 2018 to 3 May 2023, the number of titles was reduced to 16 774, which were then screened, yielding 414 abstracts. Among these, 267 relevant abstracts were identified from which 204 appropriate titles were selected for a comprehensive GRADE analysis. Additionally, the study considered 4 reviews, 16 meta-analyses, 9 previously published guidelines, 58 prospective cohort studies and 83 retrospective studies. The guideline provides 55 evidence-based recommendations that were voted on by a Delphi process, reaching a solid consensus (>90% agreement).

DISCUSSION

This update of the previous guidelines has covered new organisational and clinical aspects of the preoperative anaesthesia assessment to provide a more objective evaluation of patients with a high risk of postoperative complications requiring intensive care. Telemedicine and more predictive preoperative scores and biomarkers should guide the anaesthetist in selecting the appropriate preoperative blood tests, x-rays, and so forth for each patient, allowing the anaesthetist to assess the risks and suggest the most appropriate anaesthetic plan.

CONCLUSION

Each patient should have a tailored assessment of their fitness to undergo procedures requiring the involvement of an anaesthetist. The anaesthetist's role is essential in this phase to obtain a broad vision of the patient's clinical conditions, to coordinate care and to help the patient reach an informed decision.

Emergency medicine updates: Endotracheal intubation

INTRODUCTION

Airway management including endotracheal intubation (ETI) is a key skill for emergency clinicians. Therefore, it is important for emergency clinicians to be aware of the current evidence regarding the identification and management of patients requiring ETI.

OBJECTIVE

This paper evaluates key evidence-based updates concerning ETI for the emergency clinician.

DISCUSSION

ETI is commonly performed in the emergency department (ED) setting but has many nuanced components. There are several tools that have been used to predict a difficult airway which incorporate anatomic and physiologic features. While helpful, these tools should not be used in isolation. Preoxygenation and apneic oxygenation are recommended to reduce the risk of desaturation and patient decompensation, particularly with noninvasive ventilation in critically ill patients. Induction and neuromuscular blocking medications should be tailored to the clinical scenario. Video laryngoscopy is superior to direct laryngoscopy among novice users, while both techniques are reasonable among more experienced clinicians. Recent literature suggests using a bougie during the first attempt. Point-of-care ultrasound is helpful for confirming correct placement and depth of the endotracheal tube.

CONCLUSIONS

An understanding of literature updates can improve the ED care of patients requiring emergent intubation.

Universal C-MAC® videolaryngoscope use in adult patients: a single-centre experience

Universal use of Storz C-MAC® videolaryngoscopes was implemented for adult tracheal intubations in the operating theatres, intensive care unit and emergency department at Royal United Hospitals Bath NHS Foundation Trust in 2017. We report data from 1099 intubations from March 2020 to March 2022, collected contemporaneously and anonymously using a smartphone app, representing an estimated 18% of intubations in operating theatres and 30% of intubations in other locations during this period. Intubation success was 100%. The first-pass success rate was 87.3% overall: 87% with a Macintosh videolaryngoscope, 92% with a hyperangulated videolaryngoscope and 81% for users with ≤ 20 previous uses. First-pass success without complications was 87% overall: 87% in operating theatres (836/962), 93% in the emergency department (38/41) and 83% in the intensive care unit (73/88). Complications occurred during 0.6% of intubations: 0/962 in operating theatres and 7/137 in non-theatre locations. The rate of complications was unaltered by blade type (Macintosh 5/994 vs. hyperangulated 2/105, p = 0.14); intubator experience with the device (≤ 20 previous clinical uses 2/260 vs. > 20 previous uses 5/832, p = 0.67) and use of airborne personal protective equipment (PPE 6/683 vs. no-PPE 1/410, p = 0.27). Complication rates increased outside theatres (theatres 0/963 vs. non-theatre 7/136, p < 0.001) and during rapid sequence induction (RSI 6/379 (1.6%) vs. non-RSI 1/720 (0.1%), p = 0.008).

Comparison of nasal and face mask ventilation in anaesthetised obese adults: A randomised controlled study

Background and Aims

The use of a face mask while inducing general anaesthesia (GA) in obese patients is often ineffective in providing adequate ventilation. Although nasal mask ventilation has demonstrated effectiveness for continuous positive airway pressure (CPAP) in obese patients with obstructive sleep apnoea (OSA), it has not yet been applied to the induction of anaesthesia. This study evaluated the efficacy of nasal mask ventilation against standard face mask ventilation in anaesthetised obese patients with body mass index (BMI)>25 kg/m2.

Methods

Ninety adult patients with BMI >25 kg/m2 were randomly assigned to receive either facemask (Group FM) or nasal-mask (Group NM) ventilation during induction of GA. Expired tidal volume (VtE), air leak, peak inspiratory pressure (PIP), plateau pressure (PPLAT), oxygen saturation (SpO2), and end-tidal carbon dioxide (EtCO2) were recorded for10 breaths, and their mean was analysed.

Results

The mean (standard deviation) VtE measured was not significantly higher in Group NM [455.98 (55.64) versus 436.90 (49.50) mL, P = 0.08, degree of freedom (df):88, mean difference (95% confidence interval [CI]) -19.08 (-41.14, 2.98) mL]. Mean air-leak [16.44 (22.16) versus 31.63 (21.56) mL, P = 0.001, df: 88, mean difference 95%CI: 15.19 (6.03,24.35)], mean PIP [14.79 (1.39) versus 19.94 (3.05) cmH2O, P = 0.001, df: 88, mean difference, 95%CI: 5.15 (4.16, 6.14)], and mean PPLAT [12.04 (1.21) versus 16.66 (2.56) cmH2O, P = 0.001, df: 88, mean difference 95% CI: 4.62 (3.78, 5.45)] were significantly lower in Group NM. EtCO2, SpO2, and haemodynamic measurements were similar between the two groups.

Conclusion

Nasal mask ventilation is an effective ventilation method and can be used as an alternative to face mask ventilation in anaesthetised obese adults with BMI>25 kg/m2.

Difficult Tracheal Intubation and Airway Outcomes after Radiation for Nasopharyngeal Carcinoma

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

4 Laryngoscope, 134:120-126, 2024.

Geometric morphometrics and machine learning from three-dimensional facial scans for difficult mask ventilation prediction

Background

Unanticipated difficult mask ventilation (DMV) is a potentially life-threatening event in anesthesia. Nevertheless, predicting DMV currently remains a challenge. This study aimed to verify whether three dimensional (3D) facial scans could predict DMV in patients scheduled for general anesthesia.

Methods

The 3D facial scans were taken on 669 adult patients scheduled for elective surgery under general anesthesia. Clinical variables currently used as predictors of DMV were also collected. The DMV was defined as the inability to provide adequate and stable ventilation. Spatially dense landmarks were digitized on 3D scans to describe sufficient details for facial features and then processed by 3D geometric morphometrics. Ten different machine learning (ML) algorithms, varying from simple to more advanced, were introduced. The performance of ML models for DMV prediction was compared with that of the DIFFMASK score. The area under the receiver operating characteristic curves (AUC) with its 95% confidence interval (95% CI) as well as the specificity and sensitivity were used to evaluate the predictive value of the model.

Results

The incidence of DMV was 35/669 (5.23%). The logistic regression (LR) model performed best among the 10 ML models. The AUC of the LR model was 0.825 (95% CI, 0.765-0.885). The sensitivity and specificity of the model were 0.829 (95% CI, 0.629-0.914) and 0.733 (95% CI, 0.532-0.819), respectively. The LR model demonstrated better predictive performance than the DIFFMASK score, which obtained an AUC of 0.785 (95% CI, 0.710-0.860) and a sensitivity of 0.686 (95% CI, 0.578-0.847). Notably, we identified a significant morphological difference in the mandibular region between the DMV group and the easy mask ventilation group.

Conclusion

Our study indicated a distinct morphological difference in the mandibular region between the DMV group and the easy mask ventilation group. 3D geometric morphometrics with ML could be a rapid, efficient, and non-invasive tool for DMV prediction to improve anesthesia safety.

Difficult or impossible facemask ventilation in children with difficult tracheal intubation: a retrospective analysis of the PeDI registry

BACKGROUND

Difficult facemask ventilation is perilous in children whose tracheas are difficult to intubate. We hypothesised that certain physical characteristics and anaesthetic factors are associated with difficult mask ventilation in paediatric patients who also had difficult tracheal intubation.

METHODS

We queried a multicentre registry for children who experienced "difficult" or "impossible" facemask ventilation. Patient and case factors known before mask ventilation attempt were included for consideration in this regularised multivariable regression analysis. Incidence of complications, and frequency and efficacy of rescue placement of a supraglottic airway device were also tabulated. Changes in quality of mask ventilation after injection of a neuromuscular blocking agent were assessed.

RESULTS

The incidence of difficult mask ventilation was 9% (483 of 5453 patients). Infants and patients having increased weight, being less than 5th percentile in weight for age, or having Treacher-Collins syndrome, glossoptosis, or limited mouth opening were more likely to have difficult mask ventilation. Anaesthetic induction using facemask and opioids was associated with decreased risk of difficult mask ventilation. The incidence of complications was significantly higher in patients with "difficult" mask ventilation than in patients without. Rescue placement of a supraglottic airway improved ventilation in 71% (96 of 135) of cases. Administration of neuromuscular blocking agents was more frequently associated with improvement or no change in quality of ventilation than with worsening.

CONCLUSIONS

Certain abnormalities on physical examination should increase suspicion of possible difficult facemask ventilation. Rescue use of a supraglottic airway device in children with difficult or impossible mask ventilation should be strongly considered.

Risk factors for difficult mask ventilation and difficult intubation among patients undergoing pharyngeal and laryngeal surgery

Background

The prediction of difficult mask ventilation (DMV) and difficult intubation (DI) are key questions in anesthesia fields. DMV or DI related to pharyngeal and laryngeal diseases are a special kind of difficult airways. However, there is a lack of risk factors for prediction.

Methods

This study retrospectively collected data from patients who were admitted to the Eye & ENT Hospital of Fudan University from May 2014 to May 2018 and underwent laryngopharyngeal surgery under general anesthesia.

Results

A total of 126 patients were included. Twenty patients suffered from DMV. Preoperative laryngeal obstruction classification (OR = 7.46, 95% CI: 2.56-21.76, P < 0.001) and airway patency after sevoflurane inhalation (OR = 10.96, 95% CI: 2.70-44.43, p = 0.001) were independently associated with DMV. Seventy-six patients could be intubated at the first attempt. Preoperative laryngeal obstruction grade (OR = 0.28, 95% CI: 0.13-0.62, P = 0.002), neoplasm size (OR = 0.43, 95% CI: 0.22-0.82, P = 0.011), and airway patency after sevoflurane inhalation (OR = 0.14, 95% CI: 0.05-0.36, P < 0.001) were independently associated with first-attempt successful intubation.

Conclusion

Among patients with pharyngeal and laryngeal diseases, the degree of laryngeal obstruction before the operation and the degree of airway obstruction after inhaling sevoflurane are the risk factors of DMV. The degree of laryngeal obstruction before the operation, airway obstruction after inhaling sevoflurane, and the neoplasm size are the risk factors of DI.

Evaluation of Ventilation with Nasal Versus Face Mask After General Anesthesia Induction in Pediatric Patients

Background

Because of some difficulties during face mask ventilation in unconscious patients, such as upper airway obstruction patients, we conducted this study to compare nasal and face mask ventilation during general anesthesia induction.

Methods

In this clinical trial study, 70 patients between 3 and 12 years old undergoing elective lower abdominal surgery with general anesthesia were randomly divided into two groups. After administration of induction agents, one group was ventilated with the face mask and 100% oxygenation in three minutes and the other with the nasal mask. The mean expiratory volume, airway pressure, end-tidal CO₂ (EtCO₂), blood oxygen saturation (SpO₂), and hemodynamic factors were recorded and compared in the baseline, two minutes after mask ventilation, and five minutes after intubation.

Results

The mean EtCO₂ in the second minute after ventilation was significantly higher in the nasal mask group than in the face mask group (P = 0.04). However, in the fifth minute after intubation, there was no significant difference between the two groups (P = 0.31). Other factors related to ventilation did not significantly differ between the two groups.

Conclusions

It can be concluded that nasal mask ventilation is as effective as facial mask ventilation. The nasal mask can replace the face mask if there is difficult face mask ventilation or airway obstruction.

Updated guideline on equipment to manage difficult airways: Australian and New Zealand College of Anaesthetists

The Australian and New Zealand College of Anaesthetists (ANZCA) recently reviewed and updated the guideline on equipment to manage a difficult airway. An ANZCA-established document development group, which included representatives from the Australasian College for Emergency Medicine and the College of Intensive Care Medicine of Australia and New Zealand, performed the review, which is based on expert consensus, an extensive literature review, and bi-nationwide consultation. The guideline (PG56(A) 2021, https://www.anzca.edu.au/getattachment/02fe1a4c-14f0-4ad1-8337-c281d26bfa17/PS56-Guideline-on-equipment-to-manage-difficult-airways) is accompanied by a detailed background paper (PG56(A)BP 2021, https://www.anzca.edu.au/getattachment/9ef4cd97-2f02-47fe-a63a-9f74fa7c68ac/PG56(A)BP-Guideline-on-equipment-to-manage-difficult-airways-Background-Paper), from which the current recommendations are reproduced on behalf of, and with the permission of, ANZCA. The updated 2021 guideline replaces the 2012 version and aims to provide an updated, objective, informed, transparent, and evidence-based review of equipment to manage difficult airways.

Comparison of intraoral mask and classic face mask in terms of ventilation success and practitioners' workload assessments: A randomised crossover study

AIM

Providing effective ventilation of the unconscious patient is an essential skill in every specialty dealing with airway management. In this randomised crossover study aimed to compare intraoral and classic face mask in terms of ventilation success of patients, practitioners' workload and anxiety assessments. Also we analysed potential risk factors of difficult mask ventilation for both masks.

METHODS

In all, 24 anaesthesiology residents and 12 anaesthesiologists participated in the study. Each of the practitioners ventilated four patients with both masks at settled pressure and frequency. Practitioners rated their workload and anxiety related to masks with National Aeronautics and Space Administration Task Load Index score and State Trait Anxiety Inventory scale. Ventilation success was evaluated with Han scale, expiratory tidal volume and leak volume. We analysed potential risk factors of difficult mask ventilation with anthropometric characteristics and STOP-Bang score.

RESULTS

Ventilation success rate was superior with intraoral mask comparing to classic face mask in terms of successful ventilation (P = .000) and tidal volume (P = .000). Leak volume in in intraoral mask ventilation was significantly lower than classic face mask (P = .000). Difficult mask ventilation risk factors for classic face mask were high weight (P = .011), neck circumference (95% CI, OR = 1.180, P = .002), Mallampati score (P = .029) and high risk of OSAS (P = .001). Difficult mask ventilation risk factors for intraoral mask were high body mass index (95% CI, OR 1.162 P = .006) and Mallampati score (P = .043). The anxiety ratings of practitioners were similar between two masks. The workload rating is higher with intraoral mask comparing to classic face mask.

CONCLUSION

Intraoral mask may be an effective alternative device for bag-valve mask ventilation.

The Impact of Sevoflurane and Propofol Anesthetic Induction on Bag Mask Ventilation in Surgical Patients with High Body Mass Index

Background and Aims:

Obesity is associated with restrictive ventilatory pattern which causes rapid oxygen desaturation. Although obesity is considered as a risk factor for difficult airway management, failure to achieve effective bag mask ventilation (BMV) can be catastrophic. This study tried to assess the effect of both propofol and sevoflurane on the efficacy of BMV during anesthetic induction in obese patients.

Patients and Methods:

A total of 200 cases were included, and they were randomly divided into two equal groups; Group S which included 100 cases who underwent sevoflurane induction, and Group P which included the remaining 100 cases who underwent propofol induction.

Results:

No statistically significant difference was detected between the two groups regarding patient and air way characteristics (P > 0.05). Difficult BMV (DBMV) was encountered in 19% and 37% of cases in Groups S and P, respectively. The incidence of DBMV was significantly increased in the P group (P = 0.005). Furthermore, the severity of difficulty was more marked in the P group. Logistic regression analysis revealed that thyromental distance, presence of macroglossia, presence of beard, lack of teeth, history of snoring, as well as propofol induction were risk factors for DBMV.

Conclusion:

Sevoflurane can facilitate BMV and provide better intubation conditions in comparison to propofol during anesthetic induction in morbidly obese patients. Moreover, decreased thyromental distance, presence of macroglossia and beard, lack of teeth, and history of snoring are considered preoperative indicators of DBMV.

Submental Ultrasound Is Effective in Predicting Difficult Mask Ventilation but Not in Difficult Laryngoscopy

The goal of this study was to determine the utility of submental ultrasound parameters in distinguishing difficult airway management from easy airway management. Forty-one adult patients who underwent elective surgery under general anesthesia with endotracheal intubation from March to December 2018 were included. We used submental ultrasound to measure tongue base thickness (TBT) in the midsagittal plane and the distance between lingual arteries (DLA) in the transverse dimension. The primary outcome was difficult laryngoscopy, and the secondary outcome was difficult mask ventilation. Receiver operating characteristic curve analysis and logistic regression revealed no correlation between difficult laryngoscopy and SMUS measurements. Nevertheless, patients with difficult mask ventilation had significantly higher TBT (p = 0.009) and longer DLA (p = 0.010). After adjustment of confounding factors, increased TBT (>69.6 mm) was the sole independent predictor of difficult mask ventilation. The results indicated that SMUS is effective in predicting difficult mask ventilation but not difficult laryngoscopy.

Routinely collected data and patient-centred research in anaesthesia and peri-operative care: a narrative review

Randomised controlled trials are the gold standard in clinical research, but remain rare due to their expense and a perceived lack of 'real-world' applicability. At the same time, there has been an exponential increase in routinely collected data which presents opportunities for audit, quality improvement, adverse event reporting and more efficient clinical research. Registry-based research benefits from reduced cost, large sample size and real-world applicability, with methodological developments, particularly registry-based randomised controlled trials and causal inference techniques, showing promise. Limitations include data quality and validity, the need for data linkage, the restrictions of fixed data fields, regulatory barriers, and privacy and security concerns. However, the principal factor hampering current efforts is a lack of anaesthesia-specific datasets in the UK and the fact that most surgical registries do not collect any anaesthetic data. This presents an opportunity for anaesthetists, through enhanced engagement and collaboration, to influence and improve the design of these datasets and increase the value and volume of data collected. Better datasets, coupled with a growing appreciation of new analysis methodologies, would allow significant progress towards realising the potential of routinely collected data for patient benefit. At the same time, work should begin on the development of a minimum dataset for anaesthesia to underpin new data sharing networks and, ideally, a national registry of anaesthesia.

Analysis of urgent/emergent conversions from monitored anesthesia care to general anesthesia with airway instrumentation

Background

Monitored Anesthesia Care (MAC) is an anesthetic service involving the titration of sedatives/analgesics to achieve varying levels of sedation while avoiding general anesthesia (GA) and airway instrumentation. The goal of our study was to determine the overall incidence of conversion from MAC to general anesthesia with airway instrumentation and elucidate reasons and risk factors for conversion.

Methods

In this retrospective observational study, all non-obstetric adult patients who received MAC from July 2002 to July 2015 at Mount Sinai Hospital were electronically screened for inclusion via a clinical database. Patient, procedure, anesthetic, and practitioner data were all collected and analyzed to generate descriptive analyses. Subsequent univariate and multivariate analyses were used to identify specific risk factors associated with conversion to GA.

Results

Overall, 0.50% (1097/219,061) of MAC cases were converted to GA. Approximately half of conversions were due to the patient’s “intolerance” of MAC (with or without failed regional anesthesia), while the other half were due to physiologic derangements. Body mass index, male sex, American Society of Anesthesiologists Physical Status Classification, anesthesia team composition, and surgical specialty were all associated with risk of conversion to GA.

Conclusions

This is one of the first and largest retrospective studies aimed at identifying reasons and risk factors associated with the conversion of MAC to GA. These findings may be used to help better anticipate or prevent these events.

Canadian Airway Focus Group updated consensus-based recommendations for management of the difficult airway: part 1. Difficult airway management encountered in an unconscious patient

PURPOSE

Since the last Canadian Airway Focus Group (CAFG) guidelines were published in 2013, the literature on airway management has expanded substantially. The CAFG therefore re-convened to examine this literature and update practice recommendations. This first of two articles addresses difficulty encountered with airway management in an unconscious patient.

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 was lacking, statements are based on group consensus.

FINDINGS AND KEY RECOMMENDATIONS

Most studies comparing video laryngoscopy (VL) with direct laryngoscopy indicate a higher first attempt and overall success rate with VL, and lower complication rates. Thus, resources allowing, the CAFG now recommends use of VL with appropriately selected blade type to facilitate all tracheal intubations. If a first attempt at tracheal intubation or supraglottic airway (SGA) placement is unsuccessful, further attempts can be made as long as patient ventilation and oxygenation is maintained. Nevertheless, total attempts should be limited (to three or fewer) before declaring failure and pausing to consider "exit strategy" options. For failed intubation, exit strategy options in the still-oxygenated patient include awakening (if feasible), temporizing with an SGA, a single further attempt at tracheal intubation using a different technique, or front-of-neck airway access (FONA). Failure of tracheal intubation, face-mask ventilation, and SGA ventilation together with current or imminent hypoxemia defines a "cannot ventilate, cannot oxygenate" emergency. Neuromuscular blockade should be confirmed or established, and a single final attempt at face-mask ventilation, SGA placement, or tracheal intubation with hyper-angulated blade VL can be made, if it had not already been attempted. If ventilation remains impossible, emergency FONA should occur without delay using a scalpel-bougie-tube technique (in the adult patient). The CAFG recommends all institutions designate an individual as "airway lead" to help institute difficult airway protocols, ensure adequate training and equipment, and help with airway-related quality reviews.

Airways ultrasound in predicting difficult face mask ventilation

BACKGROUND

Unanticipated difficult airway is a potentially life-threatening event during elective surgery or management of critical conditions. Nevertheless, predicting difficult mask ventilation currently remains a challenge due to the poor sensitivity of available clinical tests. Our primary goal was to verify whether preoperative upper airway ultrasound measurements were useful to predict difficult face mask ventilation. Our secondary goal was to evaluate clinical characteristics and differences between patients who are difficult to ventilate and patients who are not.

METHODS

We performed a prospective observational study, enrolling 250 adult patients selected for colorectal, gastric, bariatric and pancreatic elective surgery between September 2017 and October 2018. We performed a preoperative US assessment of the airways, following a standardized protocol. We measured the hyomental distance (DIM), the thickness of the base of the tongue (SBL), the thickness of the soft tissues anterior to the hyoid bone (STTi), thyro-hyoid distance (DTI), the thickness of soft tissue anterior to the epiglottis (STTe), to the arytenoid (STTa) and to the commissure of the vocal cords (STTcv).

RESULTS

SBL had a predictive role of difficult mask ventilation in curarized and noncurarized patients for values higher than 50 mm. Hyomental distance with hyperextension of the head and subluxation of the mandible (DIMs) had a predictive role in the curarized patient (protective parameter).

CONCLUSIONS

Airways ultrasound evaluation could be an important tool to predict difficult mask ventilation. Further studies are necessary to validate the parameters found and correlate them to the preoperative clinical evaluation.

Recommendations for the evaluation and management of the anticipated and non-anticipated difficult airway of the Societat Catalana d'Anestesiologia, Reanimació i Terapèutica del Dolor, based on the adaptation of clinical practice guidelines and expert consensus

The Airway Division of the Catalan Society of Anaesthesiology, Intensive Care and Pain Management (SCARTD) presents its latest guidelines for the evaluation and management of the difficult airway. This update includes the technical advances and changes observed in clinical practice since publication of the first edition of the guidelines in 2008. The recommendations were defined by a consensus of experts from the 19 participating hospitals, and were adapted from 5 recently published international guidelines following an in-depth analysis and systematic comparison of their recommendations. The final document was sent to the members of SCARTD for evaluation, and was reviewed by 11 independent experts. The recommendations, therefore, are supported by the latest scientific evidence and endorsed by professionals in the field. This edition develops the definition of the difficult airway, including all airway management techniques, and places emphasis on evaluating and classifying the airway into 3 categories according to the anticipated degree of difficulty and additional safety considerations in order to plan the management strategy. Pre-management planning, in terms of preparing patients and resources and optimising communication and interaction between all professionals involved, plays a pivotal role in all the scenarios addressed. The guidelines reflect the increased presence of video laryngoscopes and second-generation devices in our setting, and promotes their routine use in intubation and their prompt use in cases of unanticipated difficult airway. They also address the increased use of ultrasound imaging as an aid to evaluation and decision-making. New scenarios have also been included, such as the risk of bronchoaspiration and difficult extubation Finally, the document outlines the training and continuing professional development programmes required to guarantee effective and safe implementation of the guidelines.

Factors influencing harmonized health data collection, sharing and linkage in Denmark and Switzerland: A systematic review

INTRODUCTION

The digitalization of medicine has led to a considerable growth of heterogeneous health datasets, which could improve healthcare research if integrated into the clinical life cycle. This process requires, amongst other things, the harmonization of these datasets, which is a prerequisite to improve their quality, re-usability and interoperability. However, there is a wide range of factors that either hinder or favor the harmonized collection, sharing and linkage of health data.

OBJECTIVE

This systematic review aims to identify barriers and facilitators to health data harmonization-including data sharing and linkage-by a comparative analysis of studies from Denmark and Switzerland.

METHODS

Publications from PubMed, Web of Science, EMBASE and CINAHL involving cross-institutional or cross-border collection, sharing or linkage of health data from Denmark or Switzerland were searched to identify the reported barriers and facilitators to data harmonization.

RESULTS

Of the 345 projects included, 240 were single-country and 105 were multinational studies. Regarding national projects, a Swiss study reported on average more barriers and facilitators than a Danish study. Barriers and facilitators of a technical nature were most frequently reported.

CONCLUSION

This systematic review gathered evidence from Denmark and Switzerland on barriers and facilitators concerning data harmonization, sharing and linkage. Barriers and facilitators were strictly interrelated with the national context where projects were carried out. Structural changes, such as legislation implemented at the national level, were mirrored in the projects. This underlines the impact of national strategies in the field of health data. Our findings also suggest that more openness and clarity in the reporting of both barriers and facilitators to data harmonization constitute a key element to promote the successful management of new projects using health data and the implementation of proper policies in this field. Our study findings are thus meaningful beyond these two countries.

Difficult Airway Society guidelines for awake tracheal intubation (ATI) in adults

Awake tracheal intubation has a high success rate and a favourable safety profile but is underused in cases of anticipated difficult airway management. These guidelines are a comprehensive document to support decision making, preparation and practical performance of awake tracheal intubation. We performed a systematic review of the literature seeking all of the available evidence for each element of awake tracheal intubation in order to make recommendations. In the absence of high‐quality evidence, expert consensus and a Delphi study were used to formulate recommendations. We highlight key areas of awake tracheal intubation in which specific recommendations were made, which included: indications; procedural setup; checklists; oxygenation; airway topicalisation; sedation; verification of tracheal tube position; complications; management of unsuccessful awake tracheal intubation; post‐tracheal intubation management; consent; and training. We recognise that there are a range of techniques and regimens that may be effective and one such example technique is included. Breaking down the key practical elements of awake tracheal intubation into sedation, topicalisation, oxygenation and performance might help practitioners to plan, perform and address complications. These guidelines aim to support clinical practice and help lower the threshold for performing awake tracheal intubation when indicated.

The DIFFMASK score for predicting difficult facemask ventilation: a cohort study of 46,804 patients

Facemask ventilation is an essential part of airway management. Correctly predicting difficulties in facemask ventilation may reduce the risk of morbidity and mortality among patients at risk. We aimed to develop and evaluate a weighted risk score for predicting difficult facemask ventilation during anaesthesia. We analysed a cohort of 46,804 adult patients who were assessed pre-operatively airway for 13 predictors of difficult airway management and subsequently underwent facemask ventilation during general anaesthesia. We developed the Difficult Facemask (DIFFMASK) score in two consecutive steps: first, a multivariate regression analysis was performed; and second, the regression coefficients of the adjusted regression model were converted into a clinically applicable weighted point score. The predictive accuracy of the DIFFMASK score was evaluated by assessment of receiver operating characteristic curves. The prevalence of difficult facemask ventilation was 1.06% (95%CI 0.97-1.16). Following conversion of regression coefficients into 0, 1, 2 or 3 points, the cumulated DIFFMASK score ranged from 0 to 18 points and the area under the receiver operating characteristic curve was 0.82. The Youden index indicated a sum score ≥ 5 as an optimal cut-off value for prediction of difficult facemask ventilation giving a sensitivity of 85% and specificity of 59%. The DIFFMASK score indicated that a score of 6-10 points represents a population of patients who may require heightened attention when facemask ventilation is planned, compared with those patients who are obviously at a high- or low risk of difficulties. The DIFFMASK score may be useful in a clinical context but external, prospective validation is needed.

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.

The effect of neuromuscular blockade on the efficiency of facemask ventilation in patients difficult to facemask ventilate: a prospective trial

Facemask ventilation of the lungs can be an important rescue intervention in a 'cannot intubate' scenario. We assessed the effect of neuromuscular blockade on expiratory tidal volumes in patients with expected difficulty in mask ventilation. The lungs of patients with at least three predictors of difficulty in mask ventilation were ventilated using a facemask held with two hands, with mechanical ventilation set in a pressure-controlled mode. Tidal volumes were recorded before and after the establishment of complete neuromuscular block. In 113 patients, median (IQR [range]) tidal volume increased from 350 (260-492 [80-850]) ml initially, by 48% to 517 (373-667 [100-1250]) ml 30 s after rocuronium administration, (p < 0.001). After the onset of the complete neuromuscular block, a median tidal volume of 600 (433-750 [250-1303]) ml was observed, corresponding to an increase of 71% from baseline values (p < 0.001), and 16% from values obtained 30 s after rocuronium administration, respectively; p = 0.003). No decrease in the tidal volume during the measurements was observed. We conclude that the administration of rocuronium at a dose of 0.6 mg.kg^-1 was able to improve facemask ventilation in all cases with a potentially clinically relevant increase in tidal volume. The early use of a neuromuscular blocking agent can be considered as a therapeutic option in case of difficulty with mask ventilation.