Simulated Difficult Airway Research Articles

Is McGrath® MAC better than Glidescope® Ranger for novice providers in the simulated difficult airway? A randomized manikin study

Purpose of this study:McGrath® MAC and Glidescope® Ranger are portable video laryngoscopes that are easy to learn for novice and useful in difficult airway environment. We anticipated that McGrath® MAC would show performance in intubation of novices as equal as Glidescope® Ranger in normal and difficult airway. Materials and Methods: Primary outcomes were the rate of successful intubation, intubation time and overall glottic view of McGrath® MAC,Glidescope® Ranger andMacintosh.Weperformed a prospective, single-blinded, randomized crossover study of 39 medical students using three laryngoscopes in amanikin,with simulated normal and difficult airway scenarios. Results: The successful intubation rate of McGrath® MAC (82.5 (38.5)%) was better than Macintosh (57.5 (50.1)%; p=0.026) and equal to Glidescope® Ranger (85 (36.2)%) at first attempt of easy scenario. However, McGrath® MAC was equal to Macintosh and Glidescope® Ranger from second to fifth attempt. The intubation timeofMcGrath® MAC (24.4 (14.7) s)was also equal toGlidescope® Ranger (22.2 (8.7) s) and Macintosh laryngoscopes (25.4 (12.2) s). The glottic view ofMcGrath® MAC (1 (1–1))was superior toMacintosh (2 (1–2); P=0.000) and equal to Glidescope® Ranger (1 (1-1)). Novicesachievedanequal successful intubation ratewhenusing the McGrath® MAC (94.9 (22.1)%) comparing with Glidescope® Ranger (93.3 (25)%) and Macintosh (92.3 (26.7)%) in difficult scenario (p=0.725). Intubation times were also similar for three laryngoscopes and became shorter with practice (p=0.000). The view at laryngoscopy with the McGrath® MAC was better than Macintosh (p=0.000) and not superior to Glidescope® Ranger (p=0.001). Conclusions: The rate for successful intubation and intubation time with McGrath® MAC in novices were equal to Glidescope® Ranger and Macintosh laryngoscope. Novices achieved a better glottic view with McGrath® MAC than Macintosh and not in comparison to Glidescope® Ranger in both of airway environments.

The LMA-Supreme versus the I-gel in simulated difficult airway in children

Supraglottic airway devices such as the LMA-Supreme (LMA-S) and I-gel, which have an additional lumen for the insertion of a gastric tube, can be useful in the management of the difficult airway. To test the performance of these two devices in the difficult paediatric airway. Randomised double-blind study. Anaesthesia department, university hospital. Sixty American Society of Anesthesiologists (ASA) I-II children undergoing elective surgery. After obtaining ethical approval and written informed consent from the parents, we compared the size 2 LMA-S with the I-gel in a simulated airway scenario made more difficult by using a cervical collar to limit mouth opening and neck movement. The primary aim was to compare the oropharyngeal leak pressure of the LMA-S and the I-gel. The secondary aims were to compare success rate, insertion time, time to pass a gastric tube and fibreoptic view of the larynx. Oropharyngeal leak pressure (mean ± SD) for the LMA-S was significantly higher than with the I-gel (20.9 ± 3.2 versus 18.9 ± 3.2 cmH2O, P = 0.019). First attempt success rate for the LMA-S was 100 and 90% for the I-gel (P > 0.05). Insertion time of the LMA-S was shorter than I-gel (11.2 ± 1.8 versus 13.5 ± 2.4 s, P = 0.001). Gastric tube placement was possible in all patients. The mean insertion time of the gastric tube was shorter with the LMA-S than with the I-gel (10.3 ± 3.6 versus 12.7 ± 3.2 s, P = 0.009). Fibreoptic laryngeal views were similar in both groups. In the simulated difficult airway in children, both airway devices provided effective ventilation. Paediatric size 2 LMA-S sustained a higher airway pressure before leaking and was quicker to insert than the I-gel equivalent. These differences may not be clinically significant.

First comparison of the VennerTM A.P. AdvanceTM versus the Macintosh laryngoscope for intubations by non‐anaesthetists: A manikin study

The present study aims to study whether using a videolaryngoscope (A.P. Advance™) facilitates or hinders intubation by non-anaesthetists inexperienced in its use. Thirty doctors from Emergency and Intensive Care Medicine backgrounds performed laryngoscopy and tracheal intubation using the Macintosh laryngoscope (MAC), A.P. Advance™ Normal Blade (AP N) and A.P. Advance™ Difficult Airway Blade (AP DAB) in simulated normal and difficult airway manikins. The primary outcomes measured were time to successful tracheal intubation and failure to intubate within 3 min or three attempts. Secondary outcomes were number of intubation attempts, adjuncts used, glottic view and ease of intubation. There was a higher rate of failed intubation in the simulated difficult airway in participants using the AP N blade than either the MAC or AP DAB (23% vs 3% and 7%, P = 0.031). This was associated with a longer median time to intubate with the AP N and the AP DAB versus MAC (56.6, 50.2 vs 39.9 s, P = 0.007 and P = 0.041). In the normal airway median time to intubate was longest with the AP N (27.8 s), and this was significantly slower than the MAC (18.1 s, P = 0.003) and the AP DAB (17.3 s, P < 0.001). No one failed to intubate the normal manikin. The use of the A.P. Advance™ videolaryngoscope should not be considered, without adequate prior training and experience, in the management of a difficult airway. The level of adequate training has yet to be established.

Tracheal intubation with a flexible fibreoptic scope or the McGrath videolaryngoscope in simulated difficult airway scenarios

Flexible fibreoptic endoscopic (FFE) intubation is considered the 'gold-standard' when difficult airway management is anticipated. Several videolaryngoscopes have been developed to facilitate intubation by laryngoscopy. The aim of the study was to compare the performance of the McGrath series 5 videolaryngoscope (McGrath videolaryngoscope) and the FFE for tracheal intubation in manikins with a simulated difficult airway, hypothesizing that the McGrath videolaryngoscope intubation would prove faster than FFE intubation. A randomised controlled study. The Danish Institute for medical simulation between December 2009 and June 2010. Twenty-eight anaesthesia residents participating in the Danish mandatory 3-day airway management course. All participants received instructions and training in the use of the McGrath videolaryngoscope and FFE. The participants then performed tracheal intubation on a SimMan manikin once with the McGrath videolaryngoscope and once with the FFE in three difficult airway scenarios: (1) pharyngeal obstruction; (2) pharyngeal obstruction and cervical rigidity; (3) tongue oedema. We measured successful intubations, defined as intubation within 120 s, and time to tracheal intubation. The trachea was intubated within 120 s with the McGrath videolaryngoscope in 25 out of 27 (93%), 25 out of 28 (89%) and 18 out of 28 (64%) occasions compared with 11 out of 28 (40%), 11 out of 28 (40%) and 16 out of 28 (57%) with the FFE in scenarios (1), (2) and (3), respectively. Time to tracheal intubation was shorter with the McGrath videolaryngoscope in scenarios (1) and (2) than with the FFE (Wilcoxon signed rank sum test, P < 0.0001). The McGrath videolaryngoscope is a valuable device with higher success rate and a quicker performance in simulated difficult airways. In patients, videolaryngoscopy may have a role in difficult airway algorithms, but the optimal device has yet to be found.

Difficult Airway Management for Novice Physicians: A Randomized Trial Comparing Direct and Video‐Assisted Laryngoscopy

To detect a difference in (1) intubation success and (2) successful intubation times between novice physicians using a Macintosh-style or video-assisted laryngoscope on a difficult airway manikin. Prospective randomized trial. Academic, tertiary medical center. Forty first-year residents across a variety of disciplines with fewer than 5 total live intubations were recruited for the study. Testing took place during orientation prior to commencement of clinical duties. The entire group was provided training by faculty otolaryngologists and anesthesiologists using both laryngoscope types on a manikin airway simulator in a standard intubating scenario. Subjects were then randomized into 2 testing groups, using either a Macintosh laryngoscope or video-assisted laryngoscope in a difficult intubation scenario. The difficult airway simulation entailed oral cavity/oropharyngeal obstruction using inflation of the tongue, as well as cervical spine immobilization with a rigid collar preventing extension and elevation of the head and limiting oral cavity opening. Success was defined as a confirmed endotracheal intubation by the testing instructor in 120 seconds or less. The Macintosh laryngoscope group (n = 19) had an intubation success rate of 47.4% with a mean intubation time of 69.0 seconds (95% confidence interval [CI]: 52.7, 85.2). The video-assisted group (n = 21) demonstrated a significantly higher success rate of 100% (P < .0001) and a decreased mean intubation time of 23.1 seconds (95% CI: 18.4, 27.8; P < .0001). The mean difference in success rate between groups was 52.6% (95% CI: 30.0%, 75.3%). Novice physicians with little to no prior intubation experience showed significantly higher intubation success with lower intubation times using a video-assisted laryngoscope in a difficult airway manikin simulator.

Apneic Oxygenation during simulated prolonged difficult laryngoscopy: Comparison of nasal prongs versus nasopharyngeal catheter: A prospective randomized controlled study.

Background:Apneic oxygenation by insufflating O2 through nasal prongs (NP) and nasopharyngeal catheter (NC) has been proven to be effective. We conducted this study to compare the relative efficacy of these two techniques in a simulated difficult airway situation.Objective:The objective of this study is to evaluate the influence of two techniques of apneic oxygenation (NP vs. NC) on the duration of oxygen saturation ≥95% during simulated prolonged difficult laryngoscopy.Methods:A randomized non-blinded study was conducted in 56 adult patients, 28 in each group belonging to American Society of Anesthesiologists physical status class I and II scheduled for elective surgical procedures under general endotracheal anesthesia randomized to either NC or NP group. After pre-oxygenating for an end tidal oxygen concentration of 90% and induction, ability to mask ventilate was checked and paralyzed with rocuronium. Apneic oxygenation using 5 L/min of O2 was established either by NP or NC. After laryngoscopy the laryngoscope was withdrawn to simulate a Grade 4 laryngoscopy and held in this position for an apnea time (T1) of 10 min with SpO2 maintained at ≥95% or until SpO2 dropped to < 95%, whichever is earlier. An arterial blood gas analysis was performed at the end of T1. Desaturation to < 95% were compared between the groups using Chi-square test (P < 0.05 as significant). Arterial blood gas analysis among those who sustained T1 for 10 min between the groups were compared using independent sample t-test (P < 0.05 was considered as significant). None of patients were excluded from the study.Results:In NP group nine patients desaturated as against none in the NC group (P = 0.001). Arterial blood gas analysis among non-desaturated patients was comparable with respect to PO2, PCO2 and pH.Conclusion:Nasopharyngeal catheter is a better device than nasal prongs in maintaining safe oxygenation during apnea in a simulated prolonged difficult laryngoscopy.

A Comparison Between the Bonfils Intubation Fiberscope and McCoy Laryngoscope for Tracheal Intubation in Patients with a Simulated Difficult Airway

The Bonfils Intubation Fibrescope (Bonfils) and the McCoy laryngoscope (McCoy) are airway devices designed to assist tracheal intubation in difficult cases. Individually, both the Bonfils and McCoy have demonstrated superiority to the Macintosh laryngoscope in a simulated difficult airway. In this study, we compared the Bonfils with the McCoy laryngoscope in patients whose tracheal intubation had been intentionally hindered. Our primary hypothesis was that there is a significant difference in the rate of success for tracheal intubation when using the Bonfils or McCoy laryngoscope in patients with an intentionally hindered airway. Patients undergoing elective surgery and requiring general anesthesia and endotracheal intubation were randomized to have intubation performed with either the Bonfils or McCoy laryngoscope. All patients were fitted with a hard cervical collar to simulate a difficult airway. Data collected included the success rate of endotracheal intubation, the time taken for intubation, the number of attempts required, the use of further aids to intubation, hemodynamic variables, and the incidence of adverse events. The primary end point was the relative rate of successful tracheal intubation. Categorical outcome measures were compared using the χ test, or Fisher exact test where appropriate, and the Mann-Whitney U test or unpaired Student t test where data were continuous. For the nonnormally distributed data, log transformation was adopted, and t test was performed if normalcy was achieved. Sixty adult patients were recruited and randomized into 2 groups of 30 patients each. There was no difference in the rate of successful intubation between groups (95% confidence interval [CI], -11.6% to 11.6%), with a 100% success rate achieved in both groups. We found no statistically significant differences between groups in the time taken for intubation (P = 0.32, 95% CI, 0.90-1.41) and percentage of single attempts (P = 0.47, 95% CI, -30.3% to 9.7%). However, further aids to intubation were required more frequently when using the McCoy laryngoscope (P < 0.001, 95% CI, 0.17-0.46), with 18 patients in the McCoy group requiring the use of an elastic bougie, and no patients in the Bonfils group requiring any aids. There were no significant differences found in the rates of adverse events. In the hands of trained operators, there appears to be no clinically significant difference in success, time to intubation, or adverse outcomes, when comparing the Bonfils with the McCoy laryngoscope, in the setting of a simulated difficult airway. The choice to use either device should remain based on appropriate patient selection, available aids, individual operator's experience, and economic circumstances.

Evaluation of Paramedic Utilization of the Intubating Laryngeal Mask Airway in High-Fidelity Simulated Critical Care Scenarios

Successful oxygenation and ventilation can mean the difference between life and death in the prehospital setting. While airway challenges can be numerous within the confines of the emergency department, there are many additional confounding difficulties in the prehospital setting, which include limited access to equipment, poor lighting, extreme environments, limited personnel to assist, no immediate backup, and limited rescue airway options. The concept of an easy, reliable, and rapidly deployable alternative rescue airway device is critical, especially when considering the addition of rapid sequence intubation protocols in the prehospital setting. Hypothesis The primary objective of this study was to ascertain whether paramedics can be trained to deploy this alternative airway device with an acceptable success rate in a simulated critical care airway scenario. The secondary objective was to determine whether the previously-trained paramedics were able to retain their ability to deploy the device successfully at one year. This was a prospective, observational, single-group, descriptive cohort, educational trial. Forty paramedics were trained in the use of the Intubating Laryngeal Mask Airway (I-LMA) in a simulation medicine curriculum culminating in a simulated critical care difficult airway scenario requiring urgent oxygenation and ventilation after failed traditional endotracheal intubation. An emergency medicine physician proctor determined successful airway management. Repeat testing was then performed at approximately one year out, challenging the medics to intubate a mannequin using the I-LMA during an unrelated training session. Of the 40 paramedics who underwent complete simulation training, 39 were able to intubate and ventilate the simulated difficult airway using the I-LMA during the critical care scenario. This yields a success rate of 97.5% (95% CI, 87.1%-99.4%). At approximately one year out, 35 out of 35 medics were able to intubate the mannequin using the I-LMA, resulting in a success rate of 100% (95% CI, 91.4%-100%). In this study, paramedics were able to deploy the I-LMA with a high degree of success in a simulated difficult airway, with a high degree of skill retention at one year out.

Does the use of a bougie reduce the force of laryngoscopy in a difficult airway with manual in-line stabilisation?

Manual in-line stabilisation is usually used during tracheal intubation of trauma patients to minimise movement of the cervical spine and prevent any further neurological injury. Use of a bougie in combination with laryngoscopy may reduce the forces exerted on the cervical spine. To evaluate the difference in force applied to the head and neck during tracheal intubation with a Macintosh laryngoscope with or without simultaneous use of a bougie. Randomised, crossover simulation study. Simulation laboratory, Anaesthetic Department, Queen's Hospital, Romford between March and April 2012. Twenty anaesthetists, all with a minimum of 1 year of anaesthetic experience. Participants used either a Macintosh laryngoscope alone, or in combination with a bougie in a Laerdal SimMan manikin with a simulated difficult airway and manual in-line stabilisation. The force exerted during laryngoscopy. Success rate and time taken to tracheal intubation were also measured. Significantly less force was exerted utilising a Macintosh laryngoscope in combination with a bougie compared with the laryngoscope alone (24.9 versus 44.5 N; P < 0.001). The trachea was successfully intubated on all occasions within 120 s. The use of a bougie was associated with a nonsignificant reduction in the time to tracheal intubation. To minimise the force of laryngoscopy and movement of a potentially unstable cervical spine injury, consideration should be given to the early use of a bougie.

Difficult Airway Simulation for Novice Physicians: A Randomized Trial Comparing Traditional and Video‐Assisted Laryngoscopy

Objectives: Detect a difference in intubation success and total intubation times between novice physicians using either a Macintosh laryngoscope or a video-assisted laryngoscope (Glidescope®) on a difficult airway manikin simulator. Methods: This prospective randomized trial was performed in June 2012. 40 first year residents with less than five total live intubations were recruited. Training was provided by both faculty otolaryngologists and anesthesiologists using both laryngoscope types on a manikin airway simulator in a standard intubation scenario. This was followed by randomization to use one of the aforementioned laryngoscopes in a difficult intubation scenario. The difficult airway simulation entailed oral cavity/oropharyngeal obstruction using tongue inflation, with rigid cervical spine immobilization preventing extension and elevation of the head and limiting oral cavity opening. Success was defined as a confirmed endotracheal intubation by the instructor in 120 seconds or less. Results: The Macintosh laryngoscope group (n=19) had an intubation success rate of 52.63% with a mean intubation time of 69.0 (95% CI: 52.7, 85.2) seconds. The video-assisted group (n=21) demonstrated a significantly higher success rate of 100% (p&lt;0.0001) and a decreased mean intubation time of 23.1 (95% CI: 18.4, 27.8) seconds (p&lt;0.0001). Conclusions: Novice physicians with little to no prior intubation experience showed significantly higher intubation success with lower intubation times using a video assisted laryngoscope in a difficult airway manikin simulator.

Stylet‐ or forceps‐guided tube exchanger to facilitate GlideScope® intubation in simulated difficult intubations – a randomised controlled trial

The GlideScope videolaryngoscope is widely used in the management of the difficult airway. However, passing the tracheal tube through the vocal cords can be awkward, and the use of a stylet to guide insertion is recommended. This randomised controlled trial evaluated a forceps-guided tube exchanger as an alternative to the stylet to aid intubation with the GlideScope in patients undergoing anaesthesia, with a simulated difficult airway created by the application of a semi-rigid cervical collar. Data were analysed from 178 patients randomly assigned to undergo intubation using either the stylet (n = 88) or a forceps-guided tube exchanger (n = 90). All intubations were completed successfully, with first attempt rates of 93.2% using the stylet and 94.4% using the exchanger (p = 0.597). The mean (SD) intubation time was 67.8 (28.7) s in the stylet group and 66.1 (15.5) s in the forceps-guided tube exchanger group (p = 0.11). The frequency of sore throat 1 h after extubation was 34.1% in the stylet group and 2.2% in the tube exchanger group (p < 0.001); 24 h after extubation the corresponding figures were 40.0% and 11.1% (p < 0.001). Using a forceps-guided tube exchanger may offer an advantage over a stylet in guiding tracheal intubation when the GlideScope is used.

The intubation performance of InnoScope in simulated difficult airway

In a randomised crossover manikin study comparing the intubation performance of the InnoScope with the Macintosh laryngoscope in simulated normal and difficult airways, Fong et al. 1 concluded that an improved laryngeal view obtained by the InnoScope did not translate into better conditions for tracheal intubation. Other than the limitations described in the discussion, we believe that further issues need to be clarified. Figure 4 Modified chart for infusion of lipid emulsion in local anaesthetic toxicity. Second, the median anaesthetic experience among the participants was 8 years. We believe that all participants had achieved proficiency with tracheal intubation using a Macintosh laryngoscope in the patients with normal and difficult airways. In contrast, none of the participants had used the InnoScope before the study. In the pre-study training, participants were allowed to practise tracheal intubation using the InnoScope in up to 50 attempts on the manikin. However, it is unclear whether the pre-study training was performed in the manikin with a normal airway only. If this was the case, the lower success rate of tracheal intubation using the InnoScope compared with the Macintosh laryngoscope in the difficult airway scenario may suggest that acceptable proficiency with use of the InnoScope had not been attained by many of the study participants. A critical issue raised by this study is that any new airway device is only useful in managing a difficult airway after the anaesthetist has obtained sufficient skill and experience 2, 3. Moreover, we would like to echo Behringer et al. 4 that for the results of a comparative study to be valid, participants must be equally proficient with each airway device in order to avoid bias. Third, as a new member of the video intubating stylet family, it would be interesting to know the possible reasons why 52% of participants did not achieve successful intubation with the InnoScope on the first attempt in a difficult airway scenario, despite an improved laryngeal view. Was distal angulation of the InnoScope the same in all three airway scenarios used in this study? Was the failed intubation on the first attempt attributed to difficulty directing the tracheal tube into the glottis or difficulty advancing the tracheal tube into the trachea? Moreover, it is unclear what measures were taken in order to allow successful intubation on subsequent attempts.

Tracheal intubation for a difficult airway using Airway scope®, KingVision® and McGRATH®: a comparative manikin study of inexperienced personnel

The Airway scope® (AWS), the KingVision® (KV) and the McGRATH® (MG) are new indirect video laryngoscopes designed to facilitate effective and safe tracheal intubation under various conditions. However, there are few comparative studies as for performance in tracheal intubation attempted by inexperienced personnel. The purpose of this study was to evaluate success rates, time to intubation with use of these devices by inexperienced personnel in a simulated manikin difficult airway.

Simulation‐based training in advanced airway skills in an otolaryngology residency program

Life-support training emphasizes the primacy of airway management. Acquiring these skills requires practice and exposure to events. Otolaryngology residents lack standardized training in advanced airway skills. This project aimed to create such a program by using simulation-based methodology evaluated using specific educationally based tools. Prospective cohort study. The program consisted of lectures and simulation-based training sessions designed to impart competency in a set of defined airway skills to otolaryngology residents. Only participating residents who completed the course (n = 12) were evaluated both before and after the course for their fund of knowledge through multiple-choice examinations and for clinical reasoning and technical skills as assessed by a panel of otolaryngologists in simulated difficult airway situations. Self-assessment tools were also incorporated. The average multiple choice score was 12 of 27 (44%) before the course and 15 of 27 (55%) after the completion of the course (P = .001). Faculty assessment yielded a cumulative score of 80% and 91% pre- and postcourse, respectively (P = .002). Although all residents reported prior experience in a critical emergency airway situation, only one reported prior training in advanced airway skills. A significant increase in participants' self-perceived ability to carry out critical airway-related skills was observed. All respondents felt the course was effective. Simulation-based airway training courses can be effectively incorporated into existing educational curricula for otolaryngology residents, and their success can be measured using educationally based tools. With such a course, residents can be expected to demonstrate measurable improvement in clinical knowledge base, technical skills, and self-perceived ability to handle difficult airway situations.

Evaluation of the Storz CMAC®, Glidescope® GVL, AirTraq®, King LTS-D™, and direct laryngoscopy in a simulated difficult airway

ObjectiveThe aim of this study was to compare first-attempt and overall success rates and success rates in relation to placement time among 5 different airway management devices: Storz CMAC, Glidescope GVL, AirTraq, King LTS-D, and direct laryngoscopy (DL). MethodsEmergency medical technician basic (EMT-B), EMT-paramedics (EMT-P), and emergency medicine residents and staff physicians placed each of the 5 devices in a random order into an AirSim (TruCorp, Belfast, UK) part-task training manikin. The difficult airway scenario was created by fixing the manikin head to a stationary object and introducing simulated emesis into the hypopharynx. First-attempt and overall success and success in relation to placement time were compared. Provider feedback about device performance was also evaluated. ResultsNinety-four providers (16 EMT-basics, 54 EMT-paramedics, and 24 emergency department doctors of medicine) consented to participation. First-attempt and overall success rates for DL, King LTS-D, GVL, and CMAC were not statistically different. Compared with DL, the AirTraq was 96% less likely to be placed successfully (odds ratio, 0.04; 95% confidence interval [CI], 0.01-0.14). When time was factored into the model, the odds of successful placement of the King LTS-D were higher compared with DL (hazard ratio [HR], 1.80; 95% CI, 1.34-2.42) and lower for GVL (HR, 0.59; 95% CI, 0.44-0.80) and AirTraq (HR, 0.228; 95% CI, 0.16-0.325). Providers ranked the CMAC first in terms of performance and preference for use in their practice setting. ConclusionOverall success rates for DL, King-LTS-D, and both video laryngoscope systems were not different. When time was factored into the model, the King LTS-D was more likely to be placed successfully.

SWIVIT - Swiss video-intubation trial evaluating video-laryngoscopes in a simulated difficult airway scenario: study protocol for a multicenter prospective randomized controlled trial in Switzerland

BackgroundVideo-laryngoscopes are marketed for intubation in difficult airway management. They provide a better view of the larynx and may facilitate tracheal intubation, but there is no adequately powered study comparing different types of video-laryngoscopes in a difficult airway scenario or in a simulated difficult airway situation.Methods/DesignThe objective of this trial is to evaluate and to compare the clinical performance of three video-laryngoscopes with a guiding channel for intubation (Airtraq™, A. P. Advance™, King Vision™) and three video-laryngoscopes without an integrated tracheal tube guidance (C-MAC™, GlideScope™, McGrath™) in a simulated difficult airway situation in surgical patients. The working hypothesis is that each video-laryngoscope provides at least a 90% first intubation success rate (lower limit of the 95% confidence interval >0.9). It is a prospective, patient-blinded, multicenter, randomized controlled trial in 720 patients who are scheduled for elective surgery under general anesthesia, requiring tracheal intubation at one of the three participating hospitals. A difficult airway will be created using an extrication collar and taping the patients’ head on the operating table to substantially reduce mouth opening and to minimize neck movement. Tracheal intubation will be performed with the help of one of the six devices according to randomization. Insertion success, time necessary for intubation, Cormack-Lehane grade and percentage of glottic opening (POGO) score at laryngoscopy, optimization maneuvers required to aid tracheal intubation, adverse events and technical problems will be recorded. Primary outcome is intubation success at first attempt.DiscussionWe will simulate the difficult airway and evaluate different video-laryngoscopes in this highly realistic and clinically challenging scenario, independently from manufacturers of the devices. Because of the sufficiently powered multicenter design this study will deliver important and cutting-edge results that will help clinicians decide which device to use for intubation of the expected and unexpected difficult airway.Trial registrationNCT01692535

In reply: efficacy of a new videolaryngoscope; what we should assess?

To the Editor: We thank Dr. Meng and colleagues for their constructive comments to our study [1]. Videolaryngoscopes have been shown to be useful in patients with and without difficult airways [2–5], but their efficacies may differ [2]. To assess the usefulness of each new device, we need to address three major factors: the device (efficacy), the patient (degree of difficult airway), and the performer (expertise). In addition to these major factors, as Meng and colleagues point out, we may need to assess the efficacy of supportive measures (such as pressure on the neck or use of a stylet). It would be ideal to assess all of these, but it is often impractical to standardize all factors (other than the device factor). We considered that because it would be difficult and may be unethical to standardize the patient factor in real patients, we chose to standardize the patient factor using a manikin with four different simulated difficult airways. Regarding the expertise of the performer, we stated the reasoning for choosing residents and their equal proficiency in our article [1]: It is known that the expertise of the anesthesiologist will affect the success rate of tracheal intubation. We considered that, for experienced anesthesiologists, they would be able to intubate the trachea using either a Macintosh laryngoscope or a fibreoptic bronchoscope, whereas for less experienced anesthesiologists (but with minimum skills), videolaryngoscopes may be regarded as the first choice when tracheal intubation using a Macintosh laryngoscope has failed. The participants had minimum skills with the Macintosh laryngoscopes, because in a manikin with normal airway, there were no significant differences in the success rate of tracheal intubation between the VLP-100, the AWS, and the Macintosh [1]. Meng and colleagues state that the difference in laryngoscopic views among three laryngoscopes was stated as a final endpoint of performance comparison, and comparing the views obtained with direct and video laryngoscopes is not an entirely appropriate comparison. We agree with their comments on the uncertainty regarding the use of the Cormack–Lehane score for assessing the efficacy of videolaryngoscopes, and this is why we did NOT use the view of the glottis as the primary endpoint. We clearly state that the main aim of our study was to compare success rates of tracheal intubation between the three laryngoscopes, and tracheal intubation was the primary endpoint [1]. As Meng and colleague imply, there are many factors that we did not study: for example, there is still insufficient evidence to judge whether tracheal intubation using a videolaryngoscope is less likely to traumatize the airway or to prolong apnea time [2]. We need to continue carrying out randomized controlled trials and reporting large case series, together with some tips for effective use, to establish the true role of each videolaryngoscope in patients with and without difficult airways.

A Comparison of the GlideScope Video Laryngoscope and Standard Direct Laryngoscopy in Children With Immobilized Cervical Spine

Airway management in children with cervical spine may make direct laryngoscopy difficult. Video laryngoscopy is an alternative to direct laryngoscopy. The GlideScope video laryngoscope, successfully used in expected and unexpected difficult pediatric airway situations, has not been studied so far in children with cervical spine immobilization. A total of 23 children underwent laryngoscopy with manual cervical spine immobilization using the GlideScope and a direct laryngoscope (Miller 1 or Macintosh 2 blade). Percentage of glottis opening score, Cormack-Lehane score, and time to best view were recorded. Percentage of glottis opening score using the GlideScope was 50% (1%-87%) and 90% (60%-100%) using direct laryngoscopy (P < 0.001). Cormack-Lehane score using the GlideScope was 1 (1-2.7) and 1 (1-1) in direct laryngoscopy (P < 0.001). Time to best view with the GlideScope was 21 seconds (12.2-28 seconds) and 7 seconds (6-8.7 seconds) in direct laryngoscopy (P < 0.05). Data are presented as median and interquartile range and analyzed using paired t test. In simulated difficult pediatric airway, using the GlideScope resulted in a significantly declined view to the glottic entrance. This result is in contrast to studies in children with difficult airway anatomy due to an anterior larynx, where the GlideScope resulted in improved views.

Impact of stylet use in a simulated difficult airway model

BackgroundStylet use during endotracheal intubation (ETI) is variable across medical specialty and geographic location; however, few objective data exist regarding the impact of stylet use on ETI performance. ObjectiveWe evaluated the impact of stylet use on the time required to perform ETI in cases of simulated difficult airways in novice and experienced providers. MethodsWe performed a prospective, randomized observational study of experienced (attending anesthesiologists and emergency physicians) vs inexperienced airway providers (emergency medical technician, paramedic and medical students) comparing the use of stylet vs no stylet in random order using a simulated difficult airway. The primary outcome was attempt time for each of 6 attempts defined as entry of the laryngoscope in the mouth until successfully passing the endotracheal tube past the vocal cords. We analyzed the data using descriptive statistics including means with SDs and t tests. We used generalized estimating equations to evaluate potential changes in the attempt time over multiple attempts. ResultsThere were 23 providers per group. The mean (SD) inexperienced attempt time in seconds was 25.88 (28.46) and 10.50 (5.47) for experienced providers (P < .0001). Stylet use did not alter attempt time for either group. When adjusting for stylet use, the attempt time did not change over repeated intubations (P = .541). When adjusting for experience status, inexperienced intubators had shorter attempt times with each successive trial, whereas experienced intubators attempt times remained constant (P < .001). ConclusionStylet use does not improve attempt time in a simulated difficult airway model for either inexperienced or experienced intubators.

The McGrath® Series 5 videolaryngoscope vs the Macintosh laryngoscope: a randomised, controlled trial in patients with a simulated difficult airway

We compared the McGrath® Series 5 videolaryngoscope with the Macintosh laryngoscope in a simulated difficult airway, using manual in-line stabilisation in 88 anaesthestised patients of ASA physical status 1-2. The primary outcome was laryngoscopic view. Secondary outcomes included rates of successful tracheal intubation and complications. A Cormack and Lehane grade-1 or -2 view was found in all patients when using the McGrath compared with 45 (51%, p < 0.0001) using the Macintosh laryngoscopes. The mean (SD) percentage of glottic opening was 82 (23)% using the McGrath compared with 13 (23)% using the Macintosh (p < 0.0001). In 66 out of 88 patients (75%), the McGrath improved the glottic view by one to three grades compared with the Macintosh (p < 0.001). Intubation of the trachea was successful in all patients using the McGrath, while the Macintosh was successful in 26 (59%, p < 0.001). There was no significant difference in the complication rates between the devices.