Laryngeal View Research Articles

A Macintosh Laryngoscope Blade for Videolaryngoscopy Reduces Stylet Use in Patients with Normal Airways

Although most tracheal intubations with direct laryngoscopy are not performed with a styletted endotracheal tube, it is recommended that a stylet can be used with indirect videolaryngoscopy. Recently, there were several reports of complications associated with styletted endotracheal tubes and videolaryngoscopy. In this study, we compared three videolaryngoscopes (VLSs) in patients undergoing tracheal intubation for elective surgery: the GlideScope Ranger (GlideScope, Bothell, WA), the V-MAC Storz Berci DCI (Karl Storz, Tuttlingen, Germany), and the McGrath (McGrath series 5, Aircraft medical, Edinburgh, UK) and tested whether it is feasible to intubate the trachea of patients with indirect videolaryngoscopy without using a stylet. Four hundred fifty consecutive adults (ASA PS I-II) undergoing tracheal intubation for elective surgery were randomly allocated for airway management with one of the three devices. Anesthesia induction for tracheal intubation consisted of fentanyl-propofol-rocuronium. An independent anesthesiologist used the Cormack-Lehane grading system to score an initial direct laryngoscopic view using a classic metal Macintosh blade. After subsequent positive-pressure ventilation using a face mask and an oxygen-sevoflurane mixture for 1 min, the trachea was intubated using one of the three VLSs. During intubation, the following data were collected: intubation time, number of intubation attempts, use of extra tools to facilitate intubation, and overall satisfaction score of the intubation conditions. The trachea of every patient was intubated using the VLSs, and none of the patients required conversion to the classic Macintosh laryngoscope. All three VLSs offered equal or better view of the glottis as assessed by the mean Cormack-Lehane grade, compared with the traditional Macintosh laryngoscopy, including a larger viewing angle of the glottic entrance. The average intubation time was 34 +/- 20 s for the GlideScope, 18 +/- 12 s for the V-MAC Storz, and 38 +/- 23 s for the McGrath VLS. Intubation with the Storz was faster (P < 0.05) than the other two VLS tested and necessitated fewer additional tools (P < 0.01), resulting in a higher first-pass successful intubation rate. A stylet had to be used in 7% of the patients in the Storz group versus about 50% of the patients when the other two VLS were used. The trachea of a large proportion of patients with normal airways can be intubated successfully with certain VLS blades without using a stylet, although the three studied VLSs clearly differ in outcome. The Storz VLS displaces soft tissues in the fashion of a classic Macintosh scope, affording room for tracheal tube insertion and limiting the need for stylet use compared with the other two scopes. Although VLSs offer several advantages, including better visualization of the glottic entrance and intubation conditions, a good laryngeal view does not guarantee easy or successful tracheal tube insertion. We recommend that the geometry of VLSs, including blade design, should be studied in more detail.

Use of R‐Lock one‐way valve for rapid fluid administration using a three‐way tap

Forty-six paramedics took part in this randomised crossover study. After a demonstration and one practice intubation, paramedics were asked to intubate the trachea of a manikin (Laerdal Airway Management Trainer) placed on the floor and set to simulate a grade three laryngeal view. A single-use bougie (Portex Tracheal Tube Introducer; SIMS Portex, UK) was available for use with the Mac laryngoscope. Recorded data included success rate, time to tracheal intubation, time to first ventilation with a self-inflating bag (Ambu, UK), paramedic’s impression of ease of use (0 cm extremely easy, 10 cm extremely difficult) and preference of laryngoscope. The Cochran Q test was used to analyse nominal data and Kruskal–Wallis and ANOVA were used to analyse interval scale data.

The Efficacy of the Storz Miller 1 Video Laryngoscope in a Simulated Infant Difficult Intubation

Several studies have shown video laryngoscopy to be a useful technique in the management of patients in whom glottic exposure by direct laryngoscopy is difficult. We conducted this study as a preliminary investigation comparing the Storz DCI Miller 1 video laryngoscope (VL, Karl Storz GmbH, Tuttlingen, Germany) and direct laryngoscopy with a Miller 1 laryngoscope (DL) in an infant manikin model simulating difficult direct laryngoscopy. We hypothesized that compared with DL, VL would provide a better glottic view but would be associated with a longer time to intubation because of the different skill set required when using video intubation. A Laerdal infant airway management training manikin (Laerdal Medical, Wappingers Falls, NY) was adapted using cloth tape to limit cervical spine mobility. Thirty-two attending pediatric anesthesiologists attempted tracheal intubation of the infant manikin using VL and DL in randomized order. The best laryngeal view with each laryngoscope and time to intubation were documented. There was a significant difference in the distributions of laryngoscopy grades between VL and DL (P < 0.001), with the VL giving a better laryngeal view. Forty percent of anesthesiologists reported a Grade 3 or 4 view with DL; all of which were converted to Grades 1 and 2 with VL. The median grade with interquartile range was two (2-3) for DL and one (1-2) for VL (P < 0.001). Seventy-eight percent of participants reported an improvement of at least one grade in laryngeal view with VL compared with DL. There were two failed intubations using DL and none using VL. Time to intubation was similar between the two techniques. The Storz Miller 1 VL blade improved glottic exposure in a simulated difficult laryngoscopy compared with direct laryngoscopy with a standard Miller 1 blade without increasing the time to intubation.

A comparison of the new paediatric Glidescope®Cobalt Videolaryngoscope and the conventional laryngoscope in simulated normal and difficult intubation conditions

Introduction: Intubation is the core skill of every anaesthetist [1]. The Royal College of Anaesthetists has expressed concern over the apparent increase in airway problems. The Glidescope® can improve laryngeal view [2,3] in adults but not necessarily the time taken to intubation [3,4]. A new paediatric Glidescope® (GVL) became available in October 2008. Instead of the previous reusable version, GVL® small (weight range 1.5–20 kg) there are now two new disposable blades, GVL® 1 (<3.6kg) and GVL® 2 (1.8–10 kg) for use with the ultraportable Cobalt videobaton1–2. Disposable equipment is preferable as it reduces the risk of infection transmission. We aimed to compare the GVL® 2 with conventional laryngoscopy in a paediatric simulator BabySIM (METI) under both normal and difficult airway conditions. We hypothesised the new Glidescope® would perform as well as the conventional laryngoscope. Methods: Following ethics committee approval and informed consent, subjects were asked to perform four intubations in random order; two under normal and two under difficult airway conditions. For each condition, intubation was performed with a conventional laryngoscope (Miller blade) and a GVL® 2. The primary outcome was time to intubation, defined as time from picking up the laryngoscope until first successful inflation of the lungs. A visual analogue scale (VAS) was used to assess the laryngoscopes for field of view, ease of use, willingness to use in an emergency and overall satisfaction. Results were analysed using a paired t-test. Results: Twenty eight anaesthetists were recruited (18 consultants, 10 trainees). Thirteen had no previous experience with the Glidescope® and 15 had used it less than10 times. Results are shown in Table 1. There was no statistical difference in the time taken for successful intubation between the conventional laryngoscope and Glidescope® although there was a trend towards a longer intubation time with the Glidescope®. Time to successful laryngoscopy was significantly longer for the difficult airway compared to the normal airway with both conventional laryngoscopy (P = 0.001) and the Glidescope® (P = 0.002). Table 1. Time to successful intubation and results of VAS Time to intubation (s) Mean (SD) VAS (0–10) evaluation of laryngoscopes Median (IQR) Normal Difficult Field of view Ease of use Emergency use Overall Conventional 26.3 (11.1) 45.2 (27.5) 8 (6–9) 8 (7–9) 9 (8–10) 8 (8–9) Gildescope® 30.3 (20.0) 50.9 (21.9) 7 (6–9) 8 (7–9) 6 (5–7) 7 (6–8) Discussion: Successful intubation of our simulator manikin under difficult airway conditions was prolonged with both laryngoscopes when compared to normal conditions, suggesting that BabySIM is a useful model for difficult intubation. The Glidescope® performed as well as the conventional laryngoscope however it did not reduce the time to intubation, which is similar to results in adult simulators [3]. Our anaesthetists indicated a preference for conventional laryngoscopy in the emergency setting. This is likely to be due to familiarity with equipment. Conclusion: The Glidescope® performs as well as conventional laryngoscopy for intubation of the BabySIM manikin in both the normal and simulated difficult airway setting.

A comparison of Truview infant EVO2 laryngoscope with the Miller blade in neonates and infants

The Truview EVO2 laryngoscope is a recently introduced device with a unique blade that provides a wide and magnified laryngeal view at 46 degrees anterior refracted angle. An infant blade of the laryngoscope has recently become available. The aim of the study was to compare the Truview infant EVO2 laryngoscope with the Miller straight blade laryngoscope in order to determine whether the Truview EVO2 laryngoscope provided an improved laryngeal view at laryngoscopy and also to assess the time taken for intubation with the two devices. In this prospective randomized study, 60 neonates and infants of either sex undergoing surgery under general anesthesia were enrolled and divided into two groups: endotracheal intubation using a Truview infant blade (Group I) or with a Miller blade number 0 (Group II). The view of the glottis at laryngoscopy, time to intubation and the number of attempts required for intubation were recorded. The average time for laryngoscopy in Group I was 18.18 s and in Group II was 16.30 s, which though not significant clinically, is statistically significant (P = 0.002). While eight patients (26.6%) had Cormack and Lehane grade 2 view on laryngoscopy in Group II, only two patients (6.6%) had such a view in Group 1 (P = 0.039). The number of attempts at laryngoscopy was comparable in the two groups. In this study, we found that in neonates and infants, the tracheal intubation using Truview infant EVO2 blade took almost as much time as miller blade and provided improved laryngoscopic view as compared to the Miller blade.

Videolaryngoscopy in the management of the difficult airway: a comparison with the Macintosh blade

Several studies have shown that videolaryngoscopes can provide better laryngeal exposure than conventional laryngoscopy. These studies, however, did not exclusively focus on patients with an anticipated difficult intubation. The aim of the present study was to assess whether a videolaryngoscope would provide better laryngeal exposure than conventional laryngoscopy and therefore facilitate intubation in cases of difficult laryngoscopy. One hundred and twelve patients with an estimated difficult intubation, scheduled to undergo surgical operations, requiring general anaesthesia and endotracheal intubation, were included in the study. Direct laryngoscopy with a Macintosh blade was performed, followed by videolaryngoscopy and intubation attempt(s). The laryngeal views obtained by each method were recorded according to the Cormack/Lehane scale. The percentage of Cormack-Lehane I and II views obtained by conventional laryngoscopy rose from 63.4 to 90.2% (P < 0.0005) with videolaryngoscopy, whereas Cormack-Lehane III and IV views declined from 36.6 to 9.8% (P < 0.0005). Intubation was successful in 98.2% of the cases. In patients with an anticipated difficult airway, videolaryngoscopy significantly improved the laryngeal exposure thus facilitating endotracheal intubation.

Evaluation of tracheal tube introducers in simulated difficult intubation*

In a randomised cross-over study, 72 anaesthetists attempted to place Pro-Breathe, new Portex, and Frova single-use tracheal tube introducers and an Eschmann multiple-use introducer in the trachea of a manikin set to simulate a grade 3 laryngeal view. Successful placement (proportion, 95% confidence interval) of either the Frova (78%, 67-86%) or the Eschmann introducer (64%, 52-74%) was significantly more likely (p < 0.0001) than with the Pro-Breathe (4%, 1-12%) or the new Portex introducer (13%, 7-22%). The difference between the success rates for the Frova and the Eschmann introducers (p = 0.08) was not significant. A separate experiment revealed that the peak force that could be exerted by the Pro-Breathe, new Portex and Frova single-use introducers were three to six times greater than that which could be exerted by the Eschmann introducer (p < 0.0001). The single-use introducers are more likely to cause tissue trauma during placement, particularly if held close to the tip.

Audit of a systematic approach to laryngoscopy for predicted difficult intubation under general anaesthesia

Editor, In Canada, the GlideScope is frequently used to manage difficult airways during general anaesthesia [1,2]. For example, this video laryngoscope is likely to serve as both the primary laryngoscope for predicted difficulty and the alternative laryngoscope for unpredicted difficulty. This practice is in contrast with the UK, where the McCoy is more likely to be used as the primary or alternative laryngoscope for difficult airways or both. Although no study has compared the McCoy laryngoscope with the GlideScope, neither has a GlideScope study specifically selected patients with difficult airways, even though this video laryngoscope was designed primarily for difficult intubations. Should direct laryngoscopy be performed first with a Macintosh or McCoy blade before video laryngoscopy to at least confirm the predicted difficulty? The McCoy blade has a Macintosh profile when the tip is in neutral position. If the direct laryngeal view then confirms the difficulty, one can lift the McCoy tip during the same laryngoscopy and potentially reduce the use of the GlideScope. By systematically using the McCoy as the first laryngoscope, we therefore aimed to provide a diagnostic and systematic airway management strategy that is missed when only the GlideScope is used. After obtaining ethical approval from our hospital and university departments, we undertook a 2-month quality assurance audit to document the GlideScope usage and need during predicted difficult direct laryngoscopy under general anaesthesia. The attending anaesthesiologist evaluated the airway history and examination and selected patients with predicted laryngoscopic difficulty but easy facemask ventilation for intubation under general anaesthesia. The following systematic approach to laryngoscopy and intubation was then audited: McCoy laryngoscopy Start with the McCoy tip in the neutral position (i.e. a Macintosh profile) to confirm the predicted difficulty (laryngeal grade 3 or 4) but intubate if McCoy tip-neutral view is laryngeal grade of less than 3 (modified Cormack and Lehane score, i.e. original grade 2 modified to 2a and 2b). If predicted difficulty is confirmed, lift the McCoy tip and intubate if laryngeal grade is less than 3. GlideScope laryngoscopy if the McCoy tip-lift view is laryngeal grade 3 or 4. Using an anonymous quality assurance form, the attending anaesthesiologist recorded the patient's age, sex, documentation of previous difficult airway, Mallampati score, laryngoscopy grade(s) and intubation outcome. Sixty-one patients were audited. The mean age was 53 years, and the gender distribution was almost even. Ninety-three per cent of the patients were ASA grades 2 and 3, reflecting the higher proportion of older patients with multiple comorbidities operated upon at Vancouver General Hospital. Forty-two of the 61 patients had a Mallampati score of at least 3, demonstrating the most common reason for suspicion of difficult intubation. Using the above systematic approach, direct laryngoscopy with the McCoy neutral tip confirmed the predicted difficulty in 42 patients (69%; Table 1). The McCoy tip-lift then converted: four out of four Macintosh grade 4 views to grade 3 and 27 out of 38 (70%) Macintosh grade 3 views to grade of less than 3. In the 15 patients who were not intubated with the McCoy, the GlideScope converted all 15 out of 15 to laryngeal grade of less than 3. Therefore, 19 out of 61 (31%) patients were intubated with the McCoy neutral tip, 27 (44%) with the McCoy tip-lift and all the remaining patients (those with the most difficult laryngoscopies), 15 (25%), were intubated with the GlideScope. There were no failed intubations in this audit.Table 1: Systematic laryngoscopy and intubation in 61 patients with predicted difficultyIn summary, the McCoy blade is a simple and portable device that successfully converted difficult grade 3 direct Macintosh views into manageable views in 70% of patients. We found, however, that it was only able to convert the grade 4 Macintosh views to grade 3 views. This result mirrors the results of a study on the McCoy laryngoscope published by Chisholm and Calder [3] in 1997. The GlideScope appears to be a superior tool in that it converted all grade 3 and 4 direct views into intubatable views and gave a far better laryngoscopic exposure than the McCoy. It must be remembered, however, that a good GlideScope view does not necessarily mean an easy intubation. By first using the McCoy blade, we were able to reduce GlideScope usage by 75%. Importantly, valuable diagnostic airway information was provided for these patients from this audit for subsequent use by anaesthesiologists. If this systematic approach to airway diagnosis and management is used in a practice such as ours, we predict that the associated reduction in GlideScope use would decrease the GlideScope's overall cost and downtime because of cleaning and maintenance. Finally, consideration should be given by both the ASA and the Difficult Airway Society to make reference in their difficult airway guidelines to the availability of video laryngoscopy.

Airway Scope®‐assisted nasotracheal intubation

The Airway Scope® (AWS) (Pentax Corporation, Tokyo, Japan) is only available for orotracheal intubation [1, 2]. We describe its use in the management of a patient with difficult nasotracheal intubation. A middle-aged man scheduled for repair of a mandible fracture required nasotracheal intubation. The patient had a history of surgery for a mesopharyngeal tumour. He could open his mouth without pain, and the oropharyngeal view was Mallampati Class II. On pre-operative examination, epiglottis and vocal cords were clearly observed on flexible laryngoscopy, suggesting that there would be no particular difficulty in tracheal intubation under general anaesthesia. In the operating room, propofol, vecuronium and fentanyl were given, face mask ventilation was easy and oxygen saturation maintained at 100% during oxygen and sevoflurane anaesthesia. After preparation of the nasopharynx with 8% lidocaine spray, a fibre-optic scope (FI-16RBS; Pentax, Tokyo, Japan) was introduced into the more patent nostril. This was gently advanced, but we failed to see the glottis or epiglottis. Laryngoscopy using a Macintosh blade did not improve the view. Fibre-optic intubation alone was abandoned after multiple attempts over 20 min. To obtain a wider laryngeal view, an AWS was inserted into the pharynx. A deformed epiglottis was seen, with severe deviation caused by scarring. The tip of the fibre-optic scope was observed with the AWS. The deformed epiglottis interrupted the view by the fibre-optic scope. Using the AWS view of the larynx, the fibre-optic scope was advanced into the trachea and a tracheal tube, mounted on the fibre-optic scope was successfully placed. The combination with the laryngeal view provided by the AWS and the ability to manipulate the fibre-optic scope as a guide wire for the tracheal tube finally permitted nasotracheal intubation.

Cricoid pressure – friend or foe?

Cricoid pressure was described by Sellick [1] over 40 years ago to reduce the probability of the aspiration of gastric contents onto the pulmonary tree. It subsequently became part of the technique termed rapid sequence intubation and is used in most countries of the world as an integral part of the emergency induction of anaesthesia. Its introduction into clinical practice followed a simple technique description and case series. The technique was never evaluated in a trial. Subsequently evidence has emerged to suggest that the use of CP may impair laryngoscopy and bag mask ventilation [2]. Releasing CP has been recommended as a way of improving the laryngeal view at difficult intubations. However there is limited data concerning the effects of releasing CP (with/without laryngeal manipulation) on the resultant quality of the laryngeal view and subsequent intubation's success rates [2]. We prospectively evaluated the use of CP and its release on 402 emergency pre-hospital trauma airways over 16 months. CP was released in 47 cases. Its release was associated with an improved or neutral effect on laryngeal view in all cases. Removing CP facilitated intubation in most cases and was not associated with a worsening view of the cords in any patient. There were two cases of regurgitation associated with failed intubation, prolonged BMV and the removal of CP. CP has entered into clinical practise with scant evidence that it reduces aspiration and little evaluation of its risks and benefits. We suggest that in cases of poor laryngeal view early removal of CP is likely to facilitate intubation with little evidence of risk to the patient.

Video Laryngoscopy with the Macintosh Video Laryngoscope in Simulated Prehospital Scenarios by Paramedic Students

Objective. To investigate the effectiveness of the Karl Storz BERCI DCI Macintosh video laryngoscope (MVL) via the TELE PACK system for facilitating intubation by novice paramedic students in a simulation environment. We assessed the laryngeal view, measured by percentage of glottic opening (POGO), when intubating the SimMan manikin airway in different settings. The primary endpoint was the best POGO achieved by the student. Secondary endpoints included intubation times andsuccess rate. Method. We enrolled 25 novice paramedic students to intubate SimMan manikins. Students were randomized to use either a conventional Macintosh 3 (Mac3) blade alone or the MVL with a Mac3 blade. Students attempted their first intubation with the manikin on a stretcher in a normal neck position andreattempted intubation with the manikin's neck stiffened. The groups then crossed over using the alternate device to repeat the attempts in the manikin with a normal neck andwith a stiffened neck. The students then attempted the same sequence of four intubations with the manikin on the floor. Results. The MVL significantly improved POGO in all scenarios (p < 0.05). The MVL improved mean POGO 16% ± 6% in the manikin with a normal neck position on a stretcher and33% ± 7% in the manikin with a stiff neck on the floor. The improvement was significantly greater in simulated difficult scenarios. The intubation success rate (94%) was equal in the two groups, andthe POGO was significantly worse in the failures. In some subgroups, intubation times were longer with the MVL. Conclusion. The MVL improves the laryngeal view for novice laryngoscopists in a simulated setting, andthis improvement is greatest in simulated difficult scenarios

Comparison of airwayscope to direct laryngoscope and lightwand for cardiovascular response in patients with difficult airway.

Airwayscope (AWS), which has been used successfully for difficult airway in general anesthesia, has been anticipated that hemodynamic response to tracheal intubation in the difficult airway may be attenuated. Also, there is a series of reports demonstrating the successful use of lightwand to open the difficult airway. Thus, we decided to conduct a survey to compare AWS to lightwand and to direct laryngoscopy of cardiovascular response to tracheal intubation. Of 64 healthy patients without cardiovascular disease, 22, 21, 21 patients were randomly assigned to AWS group, lightwand group and direct laryngoscope group. After induction of general anesthesia, intubation was performed with manual in-line neck stabilization. During laryngoscopy, a modified Cormack-Lehane grade was assessed and time to intubation was measured. Systolic arterial pressure (SAP) and heart rate (HR) were recorded at the following timepoints: baseline, just before intubation, 1 min, 2 min, 3 min, 4 min and 5 min after intubation. There were no significant differences between the 3 groups in SAP, HR (P > 0.05). However modified Cormack-Lehane grade of all patients in the AWS group was I, while that in direct laryngoscope group was IIB or III. In addition, the mean time to intubation of the direct laryngoscope group was significantly longer than that of the AWS and lightwand (P < 0.05). In the difficult airway, AWS was very effective in improving laryngeal view and decreasing time to intubation compared to direct laryngoscopey. In addition, lightwand reduced the time to intubation. However we could not find any significant difference in hemodynamic response to tracheal intubation among the 3 groups.

A comparative study on the efficacy and cardiovascular response generated by macintosh and pentax-AWS video laryngoscopic endotracheal intubation methods.

The Pentax-AWS is a newly developed rigid video laryngoscope. In comparison to the Macintosh laryngoscope, it offers a significantly improved laryngeal view and facilitates endotracheal intubation. The present study was performed to compare the general efficiency and the cardiovascular responses generated by Macintosh and Pentax-AWS systems during endotracheal intubation. This study included 120 patients with American Society of Anesthesiologists (ASA) physical status class 1 or 2 requiring tracheal intubation for elective surgery. All patients were randomly allocated into two groups: Pentax-AWS (group P) and Macintosh (group M). Induction of anesthesia was performed using fentanyl, thiopental and succinylcholine intravenously. Systolic, mean and diastolic blood pressure (SBP, MBP, DBP) and heart rate (HR) were recorded just prior to induction, 1, 3, and 5 minutes after intubation. There were no significant differences in SBP, MBP, DBP and HR between both groups. However, group P showed a higher POGO (Percentage of Glottic Opening) score than group M during endotracheal intubation. Use of Pentax-AWS in endotracheal intubation did not increase hemodynamic changes compared to the use of Macintosh laryngoscope. Furthermore, Pentax-AWS offered an improved laryngeal view during endotracheal intubation.

The Effect of Laryngeal View Grade and Intraoral Bleeding on Intubation Difficulty during Fiberoptic Nasotracheal Intubation

The Effect of Laryngeal View Grade and Intraoral Bleeding on Intubation Difficulty during Fiberoptic Nasotracheal Intubation

Flexion compromises ventilation with the laryngeal tube suction II in children

There are insufficient data as to the influence of the head and neck flexion, extension, and rotation on the ventilation with laryngeal tube suction II (LTS II). The purpose of this study was to investigate the influence of the head and neck position on oropharyngeal sealing pressure (primary outcome) and ventilation score (secondary outcome) during ventilation with the LTS II in children. We studied 33 children scheduled for elective surgery. Oropharyngeal sealing pressure and ventilation score were measured with the head and neck in a neutral position, flexed, extended and rotated to the right. The ventilation score was scored from 0 to 3 based on three items (no leakage with an airway pressure of 15 cmH2O, bilateral chest excursion, and a square wave capnogram; each item scored 0 or 1 point). Peak inspiratory pressure (PIP) at a tidal volume of 10 ml x kg(-1) and fiberoptic laryngeal views were also assessed in each position. Although the sealing pressure was lower in the extended position [22 (8) cmH2O] than that in the neutral position [25 (7) cmH2O], there was no significant leakage during ventilation with a tidal volume of 10 ml x kg(-1). In the neutral, extended and rotated positions, the median ventilation scores were better (3 point respectively) than that with the head and neck flexed (1 point). PIP was decreased with the head and neck extended or rotated but was significantly increased in flexion position. During fibreoptic examination, the vocal cords were more easily seen in extension and right rotation, compared with the neutral position and flexion. Although oropharyngeal sealing pressure is decreased with the head and neck extended, effective ventilation with LTS II can be performed like in the neutral position or the rotated position. While the sealing pressure is maintained with the head and neck flexed, flexion compromises the ventilation with LTS II in children.

Comparison of the Glidescope®, the McGrath®, the Airtraq® and the Macintosh laryngoscopes in simulated difficult airways*

Several indirect laryngoscopes have recently been developed, but relatively few have been formally compared. In this study we evaluated the efficacy and the usability of the Macintosh, the Glidescope, the McGrath and the Airtraq laryngoscopes. Sixty anaesthesia providers (20 staff, 20 residents, and 20 nurses) were enrolled into this study. The volunteers intubated the trachea of a Laerdal SimMan manikin in three simulated difficult airway scenarios. In all scenarios, indirect laryngoscopes provided better laryngeal exposure than the Macintosh blade and appeared to produce less dental trauma. In the most difficult scenario (tongue oedema), the Macintosh blade was associated with a high rate of failure and prolonged intubation times whereas indirect laryngoscopes improved intubation time and rarely failed. Indirect laryngoscopes were judged easier to use than the Macintosh. Differences existed between indirect devices. The Airtraq consistently provided the most rapid intubation. Laryngeal grade views were superior with the Airtraq and McGrath than with the Glidescope.

Success of the Gum Elastic Bougie as a Rescue Airway in the Emergency Department

The gum elastic bougie (GEB) is a rescue airway device commonly found in the emergency department (ED). However, data documenting its efficacy are lacking in the emergency medicine literature. To determine the success rate of endotracheal intubation using a GEB and the reliability of "palpable clicks" and "hold-up" in the ED setting. The GEB was introduced at our two affiliated urban EDs with a 3-year residency training program and an annual census of 150,000. Physicians were trained in the use of the GEB before initiation of the study. Over the course of 1 year, we conducted a prospective, observational study of GEB practices in the ED. The study population included all adult patients on whom intubation was attempted with a GEB. All emergency physicians attempting intubation completed a structured data form after laryngoscopy, recording patient characteristics, grade of laryngeal view (using the modified Cormack-Lehane classification), and presence of "palpable clicks" and "hold-up." Indications for GEB use in our ED include a difficult or rescue airway and for training purposes. Data were analyzed using standard statistical methods and 95% confidence intervals. In our study period, there were 26 patients on whom intubation was attempted with a GEB. The overall success rate was 20/26 (76.9%; 95% confidence interval [CI] 60.7-93.1%). Among cases where the GEB was used for training purposes (all grade 1 or 2a laryngeal view), six of seven (85.7%) intubations were successful. When the GEB was used for clinically indicated purposes, 14 of 19 (73.7%; 95% CI 53.9-93.5%) intubations were successful. Palpable clicks were appreciated in 11/20 successful intubations (sensitivity 55.0%; 95% CI 33.2-76.8%); there was one false positive (specificity 80%; 95% CI 40.9-98.2%). Of 20 successful intubations, hold-up was deferred in five cases; of 15 remaining cases, hold-up was appreciated in 5/15 (sensitivity 33.3%; 95% CI 9.5-57.2%); there were no false positives (specificity 100%; 95% CI 60.7-100%). In our ED setting, the GEB had a success rate of 73.7% when utilized as a rescue airway after failed attempts. The characteristics of "palpable clicks" and "hold-up" were unreliable.

Preoperative clinical prediction of difficult laryngeal exposure in suspension laryngoscopy

We investigated general and physical predictors of difficult laryngeal exposure in patients undergoing suspension laryngoscopy; 93 patients were included in this prospective study. The patients were classified as difficult laryngeal exposure group or non-difficult laryngeal exposure group based on the laryngeal view in suspension laryngoscopy. Twelve parameters (age, sex, body mass index, neck circumference, full mouth opening, modified mallampati index, hyoid-mental, thyroid-mental, horizontal thyroid-mental, vertical thyroid-mental, sternum-mental distance) that could predict difficult laryngeal exposure were evaluated. Of 93 patients, 22 had difficult laryngeal exposure. Cormack-Lehane score, neck circumference, body mass index, modified mallampati index, hyoid-mental, thyroid-mental, vertical thyroid-mental, and sternum-mental distance showed significant correlation with difficult laryngeal exposure. Based on the multivariate analysis, neck circumference superior to 40 cm, hyoid-mental and sternum-mental distance with respectively a value less than 6.05 and 13.9 cm were independently associated with difficult laryngeal exposure. Muscular neck, hyoid-mental and sterno-mental distance should be considered clinical predictors of difficult laryngeal exposure. Measurements of physical variables at full extension position of the neck are more useful and reliable predictors than neutral position for the risk of difficult laryngeal exposure.

Lost in Translation: The Mallampati Score?

Graduate School of Medicine, Chiba University, Chiba, Japan. shirohisono@yahoo.co.jpIn Reply:— I greatly thank Drs. Downing and Baysinger for raising an important issue, my mistranslation of the Mallampati classification in my Editorial view for the noticeable article by Kodali et al. 1,2I totally agree with Drs. Downing and Baysinger that accurate knowledge and proper translation of the historical backgrounds of development of the anesthesia practice are important. Mallampati considered and hypothesized that the size of the base of the tongue is an important factor for determining the degree of difficulty during direct laryngoscopy.3Mallampati et al. prospectively tested and proved the clinical usefulness of a simple grading system of the relative tongue size into three classes by beautifully demonstrating its significant association with the laryngeal view during direct laryngoscopy in 210 adult patients.4After the milestone article was published in 1985, Samsoon and Young recalled 13 patients with failed intubation who were anesthetized during 1982–1985 at their institute and performed the airway assessment proposed by Mallampati et al. They noticed that even the soft palate was not visible in 12 of the 13 patients with failed intubation, and created the class 4 for these patients by modifying the original Mallampati classification.5For reasons of historical accuracy and because of the fundamental differences between them, a clear distinction between the 3/3 Mallampati score4and the 4/4 Samsoon–Young score5is necessary. As Drs. Downing and Baysinger indicated in their letter, confusion was introduced after the article was published by Samsoon and Young, although, needless to say, they significantly contributed to the improvement of preoperative airway assessment. Most likely, careless reading of the articles resulted in the confusion of “modified” Mallampati score currently used by many clinicians and researchers. The number of airway classes is not the only difference between the airway classification systems. Very few careful readers may recognize that the anatomical landmarks used for definitions of the airway classes and order of concealment of the structures by the tongue base significantly differ between them. Mallampati et al. defined three classes according to three anatomical landmarks seen as follows: class 1, faucial pillars, soft palate, and uvula; class 2, faucial pillars and soft palate; and class 3, soft palate.4Samsoon and Young defined four classes according to four structures seen as follows: class 1, soft palate, fauces, uvula, and pillars; class 2, soft palate, fauces, and uvula; class 3, soft palate and base of uvula; and class 4, soft palate not visible.5Clearly, the two airway classification systems are totally different.The question is whether we have been accurately translating the difference between them for modifying and reshaping the Mallampati score; regretfully, we have not done well so far. There are confusions everywhere, but most of us do not realize them. Most anesthesia textbooks, including those mentioned by Drs. Downing and Baysinger, and original articles, even by Pilkington et al. 6and Kodali et al. ,2describe a “modified” Mallampati score with four classes defined by the three anatomical landmarks used by Mallampati et al. The fourth is added as a condition that the soft palate is not visible. Clearly, the “modified” Mallampati score differs from the Samsoon–Young score. Despite using Mallampati’s anatomical landmarks, some anesthesia textbooks and even review articles use a figure published in the article of Samsoon and Young, introducing additional confusion. This confusion is possibly derived from the variability and complexity of the upper airway anatomy among patients. For example, it is difficult to determine the upper margins of the faucial pillars and the uvula. Mallampati et al. 4assume that the uvula is concealed by the tongue base first, whereas Samsoon and Young5assume that the pillars are concealed by the tongue base first. Because of the anatomical variability, both could be wrong or correct. Compared with difficulty in determining the class 2 airway, both class 1 and class 3 are relatively easily determined. One solution to this inherent mistranslation or confusion would be to just define class 2 as an oropharyngeal view between classes 1 and 3. Now, many clinicians and researchers in nonanesthesia fields acknowledge the usefulness of Mallampati’s concept. I believe it is time for anesthesiologists to recognize the inherent lost-in-translation of the Mallampati score and to improve Mallampati’s concept. By doing so, Mallampati’s great work and his name will continue to live on in our medical field.Graduate School of Medicine, Chiba University, Chiba, Japan. shirohisono@yahoo.co.jp

A New Curved Laryngoscope Blade for Routine and Difficult Tracheal Intubation

We have designed a new curved laryngoscope blade based on a new concept of reversing the peardrop phenomenon to facilitate a view of the larynx sufficient for intubation in a greater variety of patients than the current Macintosh blade affords. The new design has a bifid tip and S-shaped spatula to exert more effective pressure in the vallecula area, elevate the epiglottis and change directions of the forces on the tongue to prevent posteroinferior displacement of the compressed tongue in the submandibular space during laryngoscopy. A radiograph laryngoscopy technique was used to guide the new blade curvature design and compare the performance of the new blade with the Macintosh blade in patients with or without a difficult airway. Our results confirm that the new blade provides a laryngeal view sufficient to accomplish intubation by compressing the root of the tongue in an anterocephalad direction in the submandibular space and elevating the epiglottis effectively in patients with or without unanticipated difficult airway. The new curved blade can also effectively move the U-shaped epiglottis out of the laryngeal view to facilitate intubation in pediatric patients aged 2 mo-13 yr.