Difficult Ventilation Research Articles

Difficult Airway Prediction in Infants with Apparently Normal Face and Neck Features.

Background/Objectives: Prediction of a difficult airway during pre-anesthetic evaluation is of great importance because it enables an adequate anesthetic approach and airway management. As there is a scarcity of prospective studies evaluating the role of anthropometric measures of the face and neck in predicting difficult airways in infants with an apparently normal airway, we aimed to identify the aforementioned predictors of difficult facemask ventilation and intubation in infants. Methods: A prospective, observational study that included 97 infants requiring general endotracheal anesthesia was conducted. Anthropometric and specific facial measurements were obtained before ventilation and intubation. Results: The incidence of difficult facemask ventilation was 15.5% and 38.1% for difficult intubation. SMD (sternomental distance), TMA (tragus-to-mouth angle distance), NL (neck length) and mouth opening were significantly lower in the difficult facemask ventilation group. HMDn (hyomental distance in neutral head position), HMDe (hyomental distance in neck extension), TMD (thyromental distance), SMD, mandibular development and mouth opening were significantly different in the intubation difficulty group compared to the non-difficult group. HMDn and HMDe showed significantly greater specificities for difficult intubation (83.8% and 76.7%, respectively), while higher sensitivities were observed in TMD, SMD and RHSMD (ratio of height to SMD) (89.2%, 75.7%, and 70.3%, respectively). Regarding difficult facemask ventilation, TMA showed greater sensitivity (86.7%) and SMD showed greater specificity (80%) compared to other anthropometric parameters. In a multivariate model, BMI (body mass index), COPUR (Colorado Pediatric Airway Score), BOV (best oropharyngeal view) and TMA were found to be independent predictors of difficult intubation, while BMI, ASA (The American Society Physical Status Classification System), CL (Cormack-Lehane Score), TMA and SMD predicted difficult facemask ventilation. Conclusions: Preoperative airway assessment is of great importance for ventilation and intubation. Patient's overall condition and facial measurements can be used as predictors of difficult intubation and ventilation.

Ultrasound-based airway assessment in obese patients as a valuable tool for predicting difficult airway: an observational study

BackgroundDifficult airway, characterized by difficult mask ventilation and intubation, is common in obese patients undergoing surgery. The purpose of this study was to evaluate and compare the prognostic efficiency of ultrasound-measured anterior cervical soft tissue parameters as an indicator of difficult airway during anesthesia induction in obese patients. MethodsThis prospective, double-blind, observational study was conducted at Balikesir University Faculty of Medicine Hospital between March 2020 and March 2022. A total of 157 patients age ≥ 18 (BMI ≥ 30 kg.m-2), without previous head and neck surgery were included in the study. Anterior cervical soft tissue measurements were performed at three levels; minimum distance between the hyoid bone and skin at the level of the hyoid bone; (DSHB), distance between the midpoint of the epiglottis and skin at the level of the thyrohyoid membrane; (DSE), distance between the anterior commissure of vocal cords and skin at the vocal cord level; (DSV). The Han scale was used to assess difficult mask ventilation and the Cormack-Lehane scale was used to assess difficult laryngoscopy. ResultsIn the difficult laryngoscopy group, the mean values of DSHB, DSE and DSV were 18.5 ± 3.5, 18.3 ± 3.8, and 18.6 ± 3.4, respectively. The AUC values for DSHB, DSE, and DSV were 0.845, 0.827, and 0.850, respectively. Anterior cervical measurements showed a better predictive value for difficult laryngoscopy compared to difficult mask ventilation. ConclusionUltrasonographic measurements were predictive for difficult laryngoscopy and ventilation with better correlation in laryngoscopy.

A challenging Paediatric Airway Management; Acquired Tracheo-oesophageal Fistula Following Accidental Ingestion of a Metal Bobbin

Acquired trachea-esophageal fistula formation is a rare, life-threatening complication of delayed presentation of foreign body ingestion. Airway management of such a patient is a significant challenge to the anaesthetist due to air leak from the defect leading to difficult oxygenation and ventilation and gastric insufflation. The paediatric age group adds to the difficulty because of small airway caliber and difficult lung isolation.Multidisciplinary team involvement and close communication, prior imaging to identify the anatomy, and planning were vital for successful outcome.

COVID-19 and mechanical ventilation

Mechanical ventilation (MV) is used to treat patients with severe coronavirus disease 2019 (COVID-19). This severe respiratory illness, typically develops 8 days after symptom onset and when it does not respond to non‐invasive respiratory support, it requires advanced respiratory support, including high concentrations of inspired oxygen and mechanical ventilation. Such therapies are also required for the acute respiratory distress syndrome (ARDS), which has been widely studied over several decade. Obesity as a disease causes a restrictive lung disease and is a sufficient predisposing factor for difficult ventilation. Higher BMI patients are more likely to be young, with single organ failure, less chronic comorbidity but with increased severity of hypoxemia at presentation. Severe respiratory failure from coronavirus disease 2019 pneumonia not responding to non‐invasive respiratory support requires mechanical ventilation. Although ventilation can be a life‐saving therapy, it can cause further lung injury if airway pressure and flow and their timing are not tailored to the respiratory system mechanics of the individual patient. The phenomenon of “hard lung” is observed as the ventilation of the intubated patient is very arduous and recruitment requires a lot of effort. Coronavirus disease 2019-induced acute respiratory distress syndrome is more severe in morbidly obese patients. This relationship between BMI and mortality was investigated by several observational studies, but the relationship was not universally observed. Some studies found increased BMI was associated with an increased risk of requiring intubation and ventilation, but with no clear relationship with mortality. The combination is quite difficult as these patients oppose the ventilator. Our objective was to determine the association between MV for treatment of COVID-19.

Comparative Evaluation of Effectiveness of Two-handed E-C Clamp Technique versus V-E Technique in Patients with Predicted Difficult Mask Ventilation

Abstract Background: The skill of bag mask ventilation (BMV) remains pivotal during airway management for maintenance of oxygenation in apneic unconscious patients. Two-handed BMV techniques viz., the traditional E-C and V-E have been proven to be superior to one-handed techniques in optimizing BMV in difficult mask ventilation (DMV) scenarios. Aims and Objectives: This study aimed to compare the effectiveness of these two techniques of BMV in adult patients with predicted DMV. Methods: Four hundred ASA I-III adult patients with predictors of DMV received BMV after induction of anaesthesia using E-C clamp and V-E techniques in a randomized cross-over manner. Ventilator was set to VCV mode delivering tidal volume of 7 ml/kg, respiratory rate of 10 breaths per minute, and no PEEP. The primary outcome was exhaled tidal volume (Vte) and secondary outcomes analysed included air-leak, peak inspiratory pressure (PIP), end-tidal carbon dioxide (EtCO2), minute ventilation (MV), plateau pressure and SpO2. Results: Two-handed V-E technique generated significantly higher mean Vte of 377.83 ± 58.43 ml as compared to two-handed E-C technique (303.26 ± 103.34 ml). The air-leak was found to be significantly more with E-C technique (131.05 ml ± 100.95 ml) as compared to V-E technique (59.08 ± 49.62 ml). Higher EtCO2, MV with concomitant lower airway pressures were observed with V-E technique. Failure rate of BMV was significantly higher with E-C technique (19%) as compared to V-E technique (1%) (P = 0.001). Conclusion: Two-handed V-E technique results in more effective ventilation as compared to two-handed E-C technique in patients with predictors of difficult BMV. This technique may be preferred as a first option in patients with anticipated DMV.

Non-traumatic complete cervical spine dislocation with severe fixed kyphosis: successful multidisciplinary approach to a challenging case

BackgroundTo our knowledge, there is no previous report in the literature of non-traumatic neglected complete cervical spine dislocation characterized by anterior spondyloptosis of C4, extreme head drop, and irreducible cervicothoracic kyphosis.Case presentationWe report the case of a 33-year-old Caucasian man with a 17-year history of severe immune polymyositis and regular physiotherapy who presented with severe non-reducible kyphosis of the cervicothoracic junction and progressive tetraparesia for several weeks after a physiotherapy session. Radiographs, computed tomography, and magnetic resonance imaging revealed a complete dislocation at the C4–C5 level, with C4 spondyloptosis, kyphotic angulation, spinal cord compression, and severe myelopathy. Due to recent worsening of neurological symptoms, an invasive treatment strategy was indicated. The patient’s neurological status and spinal deformity greatly complicated the anesthetic and surgical management, which was planned after extensive multidisciplinary discussion and relied on close collaboration between the orthopedic surgeon and the anesthetist. Regarding anesthesia, difficult airway access was expected due to severe cervical angulation, limited mouth opening, and thyromental distance, with high risk of difficult ventilation and intubation. Patient management was further complicated by a theoretical risk of neurogenic shock, motor and sensory deterioration, instability due to position changes during surgery, and postoperative respiratory failure. Regarding surgery, a multistage approach was carefully planned. After a failed attempt at closed reduction, a three-stage surgical procedure was performed to reduce displacement and stabilize the spine, resulting in correct spinal realignment and fixation. Progressive complete neurological recovery was observed.ConclusionThis case illustrates the successful management of a critical situation based on a multidisciplinary collaboration involving radiologists, anesthesiologists, and spine surgeons.

Difficult mask ventilation: An objective criterion

Effective mask ventilation plays a critical role in safe management of airway before intubation or after failed intubation. Mask ventilation (MV) is the primary technique of ventilation before tracheal intubation or insertion of any airway device. Its most unique role however, is as a rescue technique for ventilation should tracheal intubation fail or prove difficult. The ability to establish adequate MV has, therefore, become a major branch point in any difficult airway algorithm. Despite it being an important skill, MV has received little attention in the extensive body of literature and book chapters addressing airway management when compared to laryngoscopy and intubation. At present, there is no standard definition for Difficult Mask Ventilation (DMV) that is based on precise and objective criterion. The authors propose a simple objective criterion to categorize difficult mask ventilation based on the best monitoring parameters.

Difficult Airway in a Patient with Well-Differentiated Epidermoid Carcinoma: A Case Report

Introduction: Cutaneous epidermoid carcinoma (SCC) is a common skin tumor that can arise from precursor lesions or de novo. It is the second leading cause of death from skin cancer and its incidence is expected to double by 2030. Risk factors include gender, ionizing radiation, alcohol and tobacco use, and HPV infection. SCC can be classified into five types according to the Peniche classification, with the ulcerative form being the most frequent. Anesthesia management for head and neck cancers is challenging due to airway complications. Case presentation: An 82-year-old female with a history of biomass combustion smoke exposure and hypertension presented with a painful papular lesion on the left nasal wing. Biopsy revealed well-differentiated epidermoid cancer. Despite treatment, the lesion progressed rapidly, leading to a request for surgical resection. The patient had predictors of difficult intubation and ventilation, and initial intubation attempts were unsuccessful. After aspiration of secretions and intracavitary bleeding, successful intubation was achieved on the second attempt. Controlled ventilation was initiated with specific settings. Clinical discussion: A difficult airway can pose challenges for anesthesiologists, especially in patients with head and neck cancer. Pre-anesthetic evaluation and preparation for rescue devices or maneuvers are crucial. In this case, the patient had a difficult Intubation Prediction Index. General anesthesia allowed for invasive monitoring, venous access, and reliable mechanical ventilation. Direct laryngoscopy was performed due to retro nasal bleeding, with equipment available for difficult airway management and aspiration. Conclusion: Anesthetic management for patients with head cancer presents challenges in airway management and carries the risk of complications. Pre-anesthetic and airway assessment are crucial to prevent complications and ensure successful intubation.

Anesthesia Management in an Edentulous Patient with Huge Parotid Tumour: Case Report

Huge head and neck tumors are known to cause difficult ventilation and difficult intubation. Edentulous mouth can result in difficult mask ventilation. Head and neck tumor resections can also present hemodynamic challenge, due to their proximity to large vessels.
 We herein report a clinical case of difficult ventilation due to large parotid tumor in an edentulous patient.

Prevalence of obstructive sleep apnea syndrome and predictors of difficult orotracheal intubation.

Obstructive sleep apnea syndrome (OSAS) is an underdiagnosed condition that causes recurrent episodes of partial or total collapse of the upper airways during sleep. It is associated with perioperative pulmonary complications. The STOP-BANG is a screening tool for assessing patients at risk of OSAS. The aim of this study was to assess the prevalence of patients with OSAS during pre-anesthetic evaluation at a hospital and its correlation with predictors of ventilation and difficult airway. This is an observational, cross-sectional study carried out from January 2022 to September 2023. The questionnaire comprised demographic data (age, weight, BMI, type of surgery, and anesthesia), the STOP-BANG, predictors of difficult orotracheal intubation (Mallampati, mouth opening, thyromental distance, cervical mobility, and upper lip bite test), and predictors of difficult ventilation through a facial mask (male sex, absence of teeth, presence of beard, obesity, and >55 years). The study had the participation of 221 patients, of whom 121 presented with a STOP-BANG ≥3, with a prevalence of 54.2%. All patients undergoing bariatric surgeries presented STOP-BANG ≥3. No significant statistical relationships were found between predictors of difficult orotracheal intubation and STOP-BANG ≥3. However, significant statistical relationships were found in relation to predictors of difficult ventilation through the facial mask.

A COMPARATIVE STUDY TO ASSESS EFFECTS OF PNEUMOPERITONEUM AND TRENDELENBURG POSITION ON HEMODYNAMICS AND VENTILATORY MECHANICS DURING TOTAL LAPAROSCOPIC HYSTERECTOMY IN OBESE AND NON-OBESE PATIENTS

Background:Hysterectomy is a common gynaecological surgical procedure, with Laparoscopic hysterectomy (LH) emerging as a favorable approach due to its benefits such as shorter recovery periods and reduced complications. However, the creation of pneumoperitoneum and the Trendelenburg position required for total laparoscopic hysterectomy (TLH) can induce significant hemodynamic and ventilatory changes. Methodology: Our study included 60 patients who were categorized into two groups of 30 each based on their BMI: non-obese (BMI < 30) and obese (BMI ≥ 30). All patients underwent routine pre-anaesthesia check-up followed by general anaesthesia. Diastolic blood pressure (DBP), systolic blood pressure (SBP), peripheral oxygen saturation (SpO2), heart rate (HR), mean arterial pressure (MAP), plateau pressure (PPLAT), peak pressure (PPEAK),and driving pressure (PDRIVING), end-tidal carbon dioxide (EtCO2) as well as static (CST) and dynamic (CDYN) lung compliance were measured at different time intervals including baseline, following induction of anaesthesia, insufflation, changing to Trendelenburg position, desufflation and after extubation. Results:The heart rate decreased on induction of anesthesia in both the groups and remained lower throughout the procedure but was statistically non-significant (p>0.05). There was a rise in SBP, DBP, and MAP on insufflation and further with head-down positioning in both obese and non-obese patients, however, was statistically non-significant (p>0.05). The PPEAK, PPLAT, and PDRIVING were increased on induction, following the creation of pneumoperitoneum as well as Trendelenburg position (p<0.05). The values were higher in obese as compared to the non-obese. The static and dynamic compliance were lower at all time intervals in obese patients when compared to the non-obese group. Conclusion: Obese patients exhibit higher plateau pressure, peak inspiratory pressure, and driving pressure values, indicating increased airway resistance and potential ventilation challenges during surgery. Additionally, the reduced static and dynamic lung compliance values in obese patients suggest decreased lung elasticity and difficult ventilation.

Difficult Airway in Adult patients: Outcome and institutional response

Introduction. The airway is one in which a trained anesthesiologist experiences difficulty in ventilation or difficulty in intubation, or both. Objective. To determine the outcome of patients over 18 years of age with a difficult airway and the characteristics of the institutional response capacity, at the Hospital Escuela Universitario, Tegucigalpa, Honduras. 2018-2020. Methods. Descriptive Cross-Sectional Study, with a sample of 80 patients with difficult airway. Non-probability sampling for convenience. The data were entered in EPI-INFO. Descriptive analysis was performed as measures of central tendency and grouping. The proportion was estimated using the formula: P = Number of people with difficult airways / number of patients older than 18 years multiplied by 100. The protocol was approved by the Ethics Committee in Biomedical Research / FCM / UNAH. Results. 28,8 % had ASA II anesthetic risk, 27,6 % had ASA IIE. 68,5 % had Grade III Cormack Lehane Scale, 7,5 % Grade II, 23,7 % Grade IV, 97,5 % of the intubation was successful, 2,5 % was unsuccessful. 36,3 % with a difficult airway are overweight, 25 % are type I obese, 13,8 % are type III obese and 8,3 %. There was 97,2 % of successful intubation and, in most, up to 2 attempts were required to achieve it. Conclusions. Obesity constitutes a risk factor for difficult ventilation and intubation, as well as an anesthetic risk. ASA II and III is also a risk factor for difficult airway.

Extracorporeal life support use in limited lung function: a narrative review.

In thoracic surgery, different modalities of extracorporeal life support (ECLS) can be used for cardiorespiratory support in complex scenarios. Decades of learning in clinical practice and physiology associated with technological development led to a great variety of ECLS technologies available. Thoracic surgery procedures with difficult or impossible single lung ventilation may still be performed using different ECLS modalities. The aim of this review is to describe the use of ECLS, with its different modalities, as a solution to perform complex surgeries in a patient with difficult or impossible single lung ventilation. A literature review was conducted using the terms "extracorporeal life support pulmonary resection" and "extracorporeal life support thoracic surgery", and articles were selected according to defined criteria. To support lung function during thoracic surgery, the most efficient and popular variety of ECLS is venovenous extracorporeal membrane oxygenation. Lung resection on a single lung after pneumonectomy, surgery in a patient with severe hypercapnia and/or low respiratory reserve, carinal and airway surgery, and severe thoracic trauma are the main examples of situations where ECLS may be the solution to provide a safe surgical environment in patients who cannot tolerate single lung ventilation. Multidisciplinarity, selection of patients and careful surgical planning are cornerstones in defining the situations that may benefit from ECLS support. Knowledge on techniques of ECLS are essential for every thoracic surgeon. Although rarely used, these techniques of cardiorespiratory support should be considered when planning complex cases with difficulties in ventilation and emergent situations.

To Evaluate Usefulness of Stop-Bang Questionnaire in Predicting Difficult Bag Mask Ventilation and Difficult Intubation in Adult Patients for Elective Surgery: Important Guide for Obstructive Sleep Apnea Patients

Introduction: Obstructive sleep apnea (OSA) is a condition with repetitive interruptions to breathing due to obstruction of the airway in sleep. We evaluated STOP-BANG score outcome. Aim and Objective: To evaluate the usefulness of stop-bang questionnaire in predicting difficult bag mask ventilation and difficult intubation (DIT) with comparison. Materials and Methods: A prospective, simple randomized, comparative study was on 100 patients. Results: O group had male preponderance, higher American Society of Anesthesiologists grades along with comorbidities, higher mallampati grades, lower sternomental distance and thyromental distance, and higher neck circumference. Mean time in study group was 31.7 s and in control group was 18.68 s. Conclusion: We conclude that patients with STOP-BANG score ≥3 are at higher risk of unanticipated difficult mask ventilation and DIT in undiagnosed cases of OSA.

The Autumn Ghost. How the Battle Against a Polio Epidemic Revolutionized Modern Medical Care

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Nasopharyngeal Ventilation Compared to Facemask Ventilation: A Prospective, Randomized, Crossover Trial in Two Different Elective Cohorts.

Facemask ventilation is routinely used to preoxygenate patients before endotracheal intubation during anesthesia induction or to secure ventilation in patients with respiratory insufficiency. Occasionally, facemask ventilation cannot be performed adequately. The placement of a regular endotracheal tube through the nose into the hypopharynx may be a valid alternative to improve ventilation and oxygenation before endotracheal intubation (nasopharyngeal ventilation). We tested the hypothesis that nasopharyngeal ventilation is superior in its efficacy compared to traditional facemask ventilation. In this prospective, randomized, crossover trial, we enrolled surgical patients requiring either nasal intubation (cohort #1, n = 20) or patients who met "difficult to mask ventilate" criteria (cohort #2, n = 20). Patients in each cohort were randomly assigned to receive pressure-controlled facemask ventilation followed by nasopharyngeal ventilation or vice versa. The ventilation settings were kept constant. The primary outcome was tidal volume. The secondary outcome was the difficulty of ventilation, measured using the Warters grading scale. Tidal volume was significantly increased by nasopharyngeal ventilation in cohort #1 (597 ± 156 ml vs.462 ± 220 ml, p = 0.019) and cohort #2 (525 ± 157 ml vs.259 ± 151 ml, p < 0.01). Warters grading scale for mask ventilation was 0.6 ± 1.4 in cohort #1, and 2.6 ± 1.5 in cohort #2. Patients at risk for difficult facemask ventilation may benefit from nasopharyngeal ventilation to maintain adequate ventilation and oxygenation before endotracheal intubation. This ventilation mode may offer another option for ventilation at induction of anesthesia and during the management of respiratory insufficiency, especially in the setting of "unexpected" ventilation difficulty.

Elective Cesarean Section under General Anesthesia Experience in more than 5,000 Patients at Melinda Women Hospital Bandung-Indonesia

BACKGROUND: Despite the safe nature of the procedure, cesarean section (CS) is still associated with higher maternal mortality and morbidity rates. CS can be performed under spinal, epidural, combined spinal and epidural, or general anesthesia. The choice of anesthesia for CS is still a matter of debate due to its side effects on mothers and neonates. Success in the selection of anesthesia in CS is seen in maternal and neonatal outcomes, where the Apgar score is used for assessing neonates in the first and fifth minutes. AIM: This study aimed to determine the effect of general anesthesia in cesarean section as measured by Apgar score. SUBJECT AND METHODS: This was a cross-sectional analytical retrospective study on a total sample of 7,131 patients who underwent elective cesarean section under general anesthesia during 18 years (July 2004–June 2022) at Melinda Women Hospital Bandung Indonesia. In this study, data from medical records were used to analyze neonatal and maternal outcomes. RESULTS: Of the 7,131 CS under general anesthesia cases, no maternal death or difficult ventilation was found; however, the incidence of postoperative nausea and vomiting (PONV) (15), difficult intubation (6), hypotension (5), and need for blood transfusion (5), and postoperative analgesia (all cases) were observed in the mothers. In neonates, neonatal death caused by IUFD and severe congenital disease (3), and a mean neonatal Apgar score of 9 and 10 at 1 and 5 min were identified. CONCLUSION: No low Apgar score is found as the effect of general anesthesia in cesarean section.

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

BackgroundDifficult 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. MethodsWe 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. ResultsThe 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. ConclusionsCertain 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.

Diagnostic Performance of Airway Ultrasound for the Assessment of Difficult Laryngoscopy: A Systematic Review and Meta-Analysis

This study aimed to review and appraise the evidence regarding airway ultrasound assessment in predicting difficult laryngoscopy in adult patients. A systematic review of the literature was conducted according to the Cochrane collaboration guidelines and the recommendations for the systematic review and meta-analysis of diagnostic studies. Observational studies that evaluated the diagnostic performance of airway ultrasound for the prediction of difficult laryngoscopy were included for consideration. Literature searches were performed in 4 databases (PubMed [Medline], Embase, Clinical Trials, and Google Scholar) to identify all observational studies using any ultrasound technique to assess difficult laryngoscopy. The search terms included "sonography," "ultrasound," "airway," "difficult airway," "difficult laryngoscopy," "Cormack," "risk factors," "ultrasound at the point of care," "difficult ventilation," "difficult intubation" and others, combined with sensitive filters. The search was done for studies performed in the last 20 years in English or Spanish. Adult patients older than 18 years old under general anesthesia for an elective procedure. Evident anatomic airway abnormalities, obstetric populations, those using an alternative imaging method besides ultrasound, and animal studies were excluded. Preoperative bedside ultrasound measuring distances and ratios from the skin to different reference points, such as the ratio of the hyomental distance in a neutral position (HMDN) and hyomental distance in extension (HMDR), HMDN, and the skin-to-epiglottis distance (SED), the preepiglottic area, and tongue thickness, among others. A total of 24 studies evaluated the prediction of a difficult laryngoscopy using airway ultrasound. The diagnostic performance and the number of ultrasound parameters reported in the studies were variable. Meta-analysis was performed for 3 measurements consistently included in most studies. The SED and the HMDR ratio presented a sensitivity of 75% and 61%, respectively, and a specificity of 86% and 88%, respectively. The ratio of the preepiglottic distance to the epiglottic distance at the midpoint of the vocal cords (pre-E/E-VC) presented the best performance for predicting a difficult laryngoscopy (sensitivity: 82%, specificity: 83%, diagnostic odds ratio: 22.2). With the currently available evidence, the 3 commonly used point-of-care ultrasound measures used to identify difficult laryngoscopy, (SED, HMDR, and pre-E/E-VC), showed better sensitivity and similar specificity to clinical measures. Future studies and more data may change the authors' confidence in these conclusions, given the wide variability of measurements noted in studies.

Pre-intubation ventilation device for bearded patients: prospective, randomized, crossover trial in anesthetized patients.

Having a beard is an independent predictor of difficult ventilation by face mask. This study evaluates the efficacy of a novel intra-oral Bag-Valve-Guedel Adaptor (BVGA) in anaesthetized bearded patients. Patients with ASA score 1-2, scheduled for elective surgery, were recruited for this prospective, crossover trial. Beard length was categorized as < 0.5cm, 0.5-1cm, 1-5cm, or > 5cm. Patients were ventilated by attending anesthesiologists using the BVGA and a facemask (both with a Guedel oral airway). End-tidal CO2 (EtCO2) and expiratory tidal volume (TV) were recorded as was the number of hands required for the procedure. The primary outcome was the difference between BVGA and Facemask. Sixty-one patients were enrolled. Of these, 38 had beards, and 23 were without beards or with beards < 0.5cm length. In bearded patients, ventilation with the BVGA was superior to the face mask by EtCO2 and non-inferior by TV (BVGA-vs-Mask, mean [95% CI]: EtCO2 [mmHg], 33.0 [31.6, 34.3]-vs-27.2 [25.5, 28.8], p < 0.001; TV [ml∙kg-1 IBW], 8.1 [7.4, 8.9]-vs-6.9 [6.0, 7.7], p = 0.11). The BVGA was found to be superior to the face mask by EtCO2 across all beard lengths (p ≤ 0.001), but by TV only for the longest beard group (p = 0.009). After securing the BVGA, ventilation was possible without hands in 74% of the cases - clearly impossible with the facemask (p ≤ 0.001).The BVGA is more effective and more convenient than the facemask in anaesthetized bearded patients. A follow-up study is underway to test whether replacing the face mask with the BVGA will improve effectiveness and ease of pre-intubation field ventilation by less-experienced, first responders.