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.     

Evaluation of three unchannelled videolaryngoscopes and the Macintosh laryngoscope in patients with a simulated difficult airway: a randomised,controlled trial

This prospective randomised, controlled trial compares the performance of three unchannelled videolaryngoscopes (KingVision^?, Airtraq^?, A.P. Advance^? MAC ) and the standard Macintosh laryngoscope. With ethics committee approval and written informed consent, 480 patients were included. A difficult airway was created with a cervical collar, limiting mouth opening and neck movement. Primary outcome was first‐attempt orotracheal intubation success. Overall success, laryngeal view, intubation difficulty scale, handling, intubation times and side‐effects were secondary outcomes. First‐attempt success rates were: KingVision 90% (95% CI 83–94%), Airtraq 82% (74–88%), A.P. Advance MAC 49% (40–58%), Macintosh 44% (35–53%; p < 0.001). The 95% confidence interval of first‐attempt success rate was thus below 90% for all devices, but the KingVision and the Airtraq performed better than the A.P. Advance MAC and the Macintosh laryngoscope. Also, performance was better with the KingVision and the Airtraq in terms of overall success, laryngeal view, intubation difficulty scale and quality of view. Problems with tube advancement were a frequent cause of intubation failure. In summary, the KingVision and the Airtraq performed better than the A.P. Advance MAC and the Macintosh laryngoscope. Success rates of the unchannelled KingVision and Airtraq were similar to those of their channelled versions reported previously, indicating that performance largely depends on blade design rather than the presence of a channel for tube advancement.     

Reduced hemodynamic responses to tracheal intubation by the Bonfils retromolar fiberscope: a randomized controlled study

The Bonfils retromolar intubation fiberscope is a rigid endoscope designed to enable glottic visualization and facilitate intubation under endoscopic vision. Theoretically, avoiding direct-vision laryngoscopy and thus could produce less stimulation during intubation than the conventional direct laryngoscopic procedure. This prospective randomized study was designed to compare the effect of tracheal intubation with direct vision laryngoscopy (Macintosh blade) and the Bonfils retromolar intubation fiberscope on the hemodynamic responses in ASA I patients. Forty patients scheduled for elective surgery and requiring endotracheal intubation were randomly allocated to one of two groups according to the intubating tool under sevoflurane nitrous oxide Anaesthesia (n=20 each). The retromolar group received tracheal intubation with the Bonfils retromolar fiberscope, while the direct laryngoscopy group received tracheal intubation by the direct vision laryngoscope (Macintosh blade). Heart rate and arterial blood pressure (systolic BP, diastolic BP, mean ABP) were recorded before induction of Anaesthesia, 3 minutes after induction of Anaesthesia (before intubation) and 5 successive recordings at one-minute interval after intubation. All the systolic BP, diastolic Bp, mean ABP and heart rate values in the direct laryngoscopy group were significantly higher in the 5 successive minutes after intubation in comparison with the retromolar group (P = 0.00). This might be attributed to the gentle intubating technique, by the Bonfils retromolar fiberscope, which allows quick endotracheal intubation without manipulations of the base of the tongue or epiglottis.     

Eine unerwartet schwierige Intubation

A solution to managing intubation difficulties during anaesthesia induction is described in this article. After two attempts at laryngoscopy had failed, endotracheal intubation was achieved by the combined use of a laryngoscope and the Bonfils rigid fiberscope. The successful technique involved two anaesthesiologists, one who displaced the patient's tongue to the left ventral part of the mouth with a laryngoscope and cleared the airway by suctioning, and one who accomplished the intubation using the Bonfils rigid fiberscope by following the blade of the laryngoscope to the larynx. After securing a good view of the vocal cords, the tube was successfully inserted into the trachea. The entire procedure of intubation was accomplished within 20 s.     

A comparison of cervical spine movement during laryngoscopy using the Airtraq or Macintosh laryngoscopes

The Airtraq laryngoscope has an oropharyngeal airway-shaped blade that provides a non-line-of-sight view of the glottis. The configuration of the blade should mean that less movement of the cervical spine is required during laryngeal visualisation. We compared the degree of cervical spine movement in laryngoscopy performed using the Airtraq and conventional Macintosh laryngoscope. In 20 patients requiring general anaesthesia and tracheal intubation, we measured cervical spine movement using radiography in the same patient during consecutive procedures using the two laryngoscopes. Although significant movement of the cervical spine from baseline was noted during all procedures (p < 0.05), cervical spinal extension with the Airtraq was 29% less than that measured during Macintosh laryngoscopy between the occiput and C4, and 44% less at the C3/C4 motion segment (p < 0.05). Anterior deviations of the vertebral bodies from baseline were 32%, 35%, 38% and 40% less at the atlas, C2, C3, and C4 vertebrae, respectively, during Airtraq laryngoscopy than those measured during Macintosh laryngoscopy (p < 0.01). Our study demonstrated that laryngoscopy using the Airtraq laryngoscope involves less movement of the cervical spine compared to conventional procedures using a Macintosh laryngoscope.     

The Pentax-AWS((R)) rigid indirect video laryngoscope: clinical assessment of performance in 320 cases

The Pentax-AWS airway scope system is a rigid indirect video laryngoscope with integrated tube guidance. Laryngoscopy and intubation are visualised using a built in LCD monitor which displays the view obtained by a CCD camera mounted in the tip of the laryngoscope. We describe its clinical performance in 320 patients. The Pentax-AWS significantly improved the laryngeal view compared to the Macintosh laryngoscope. Forty-six patients (14%) who were classified as Cormack Lehane glottic view grade 3 or 4 using the Macintosh laryngoscope were classified as grade 1 (45 cases) or 2a (1 case) using the Pentax-AWS airway scope. Laryngeal views measured by percentage of glottic opening score were improved significantly using the Pentax-AWS. Intubation using the Pentax-AWS was successful in all cases, 96% at the first and 4% at the second attempt. The mean (SD) time required to place the tracheal tube was 20 (10) s. The Cormack Lehane grade obtained with the Macintosh blade did not affect the total time to correctly position the tube using the Pentax-AWS. Intubation difficulty scale (score = 0 in 305 patients, score = 1 in 14 and score = 2 in one patient) indicates that tracheal intubation was performed easily in most cases. The Pentax-AWS not only improves the laryngeal view, but its tube guide also facilitates rapid, easy and reliable tracheal intubation under vision. It can be useful in routine anesthesia care and may be advantageous in the situation of unanticipated difficult intubation.     

Left molar approach improves laryngeal view in patients with simulated limitation of cervical movements

Background: Immobilized cervical spine, because of either diseases or stabilizing devices, poses considerable difficulties with endotracheal intubation due to poor laryngoscopic view. The left molar (LM) approach has been shown to be useful in difficult sporadic intubation cases. We evaluated efficacy of this approach of laryngoscopy to improve laryngeal view in patients with simulated limitation of cervical movements.
Methods: Thirty patients of American Society of Anesthesiologists grade I/II, who were scheduled to undergo routine surgical procedures under general anaesthesia and endotracheal intubation, were studied. A two-piece semi-rigid cervical collar was used to immobilize the cervical spine. Under standardized anaesthesia and neuromuscular blocking agent, conventional laryngoscopy using a curved Macintosh blade was performed and glottic view was recorded with and without optimal external laryngeal manipulation (OELM). Subsequently, in the same subjects the laryngoscope blade was withdrawn and re-inserted through the LM approach and glottic view was recorded with and without OELM followed by tracheal intubation.
Results: With the conventional approach, laryngeal view was recorded as grade II in five patients, grade III in 24 patients, and grade IV in one patient. However, with the LM approach, laryngeal view was grade I in 25 patients, grade II in five patients, and grade III or IV in none ( P <0.001). Tracheal intubation with the LM approach required the use of a flexible stylet to guide the tube tip into the larynx.
Conclusions: The laryngeal view is improved by the LM approach in patients with simulated limited cervical movements with a high success rate of tracheal intubation, but requires orientation for negotiation of the tube through the narrow oropharyngeal space available.     

Comparison of the C‐MAC® videolaryngoscope with the Macintosh,Glidescope®, and Airtraq® laryngoscopes in easy and difficult laryngoscopy scenarios in manikins

The C‐MAC^® comprises a Macintosh blade connected to a video unit. The familiarity of the Macintosh blade, and the ability to use the C‐MAC as a direct or indirect laryngoscope, may be advantageous. We wished to compare the C‐MAC with Macintosh, Glidescope^® and Airtraq^® laryngoscopes in easy and simulated difficult laryngoscopy. Thirty‐one experienced anaesthetists performed tracheal intubation in an easy and difficult laryngoscopy scenario. The duration of intubation attempts, success rates, number of intubation attempts and of optimisation manoeuvres, the severity of dental compression, and difficulty of device use were recorded. In easy laryngoscopy, the duration of tracheal intubation attempts were similar with the C‐MAC, Macintosh and Airtraq laryngoscopes; the Glidescope performed less well. The C‐MAC and Airtraq provided the best glottic views, but the C‐MAC was rated as the easiest device to use. In difficult laryngo‐scopy the C‐MAC demonstrated the shortest tracheal intubation times. The Airtraq provided the best glottic view, with the Macintosh providing the worst view. The C‐MAC was the easiest device to use.     

Tracheal intubation of morbidly obese patients: a randomized trial comparing performance of Macintosh and Airtraq laryngoscopes

BACKGROUND: The Airtraq laryngoscope is designed to allow visualization of the glottis without alignment of the oral, pharyngeal, and laryngeal axes. We hypothesized that this new airway device would facilitate tracheal intubation of morbidly obese patients. We compared tracheal intubation performance of standard Macintosh laryngoscope with the Airtraq laryngoscope in morbidly obese patients. METHODS: One hundred and six consecutive ASA I-III morbidly obese patients undergoing surgery were randomized to intubation with the Macintosh laryngoscope or the Airtraq laryngoscope. Induction of anaesthesia was standardized. If tracheal intubation failed within 120 s with the Macintosh or Airtraq , laryngoscopes were switched. Success rate, SpO2, duration of tracheal intubation, and quality of airway management were evaluated and compared between the groups. RESULTS: Preoperative characteristics of the patients were similar in both groups. In the Airtraq group, tracheal intubation was successfully carried out in all patients within 120 s. In the Macintosh laryngoscope group, six patients required intubation with the Airtraq laryngoscope. The mean (SD) time taken for tracheal intubation was 24 (16) and 56 (23) s, respectively, with the Airtraq and Macintosh laryngoscopes, (P<0.001). SpO2 was better maintained in the Airtraq group than in the Macintosh laryngoscope group with one and nine patients, respectively, demonstrating drops of SpO2 to 92% or less (P<0.05). CONCLUSIONS: In this study, the Airtraq laryngoscope shortened the duration of tracheal intubation and prevented reductions in arterial oxygen saturation in morbidly obese patients.     

Direkte Laryngoskopie oder C-MAC-Videolaryngoskopie?

Background

Previous studies have shown that video laryngoscopy enhances laryngeal view in patients with apparently normal and difficult airways. The utility of the novel, portable, battery-powered C-MAC video laryngoscope is as yet unproven. It was hypothesized that in routine patients undergoing ENT surgery, the rate of glottic views considered unsatisfactory, i.e. Cormack and Lehane grades IIb, III, and IV, could be significantly reduced with the C-MAC video laryngoscope compared to direct laryngoscopy.

Methods

Following ethical approval and sample size estimates 108 consecutive patients undergoing ENT surgery under general anesthesia were studied. First, direct laryngoscopy was performed with the naked eye. The best view obtained was graded by the first anesthesiologist without looking at the video monitor. A second anesthesiologist blinded to the laryngeal view obtained under direct laryngoscopy graded the laryngeal view on the video monitor. Endotracheal intubation using Ring-Adair-Elwyn (RAE) tracheal tubes was then attempted under video-aided visualization. The tubes were not reinforced with a stylet. The C-MAC video laryngoscopy system (Karl Storz, Tuttlingen, Germany) is a novel device that can be used with Macintosh laryngoscope blades in different sizes. A camera and light source are located recessed from the tip of the blade. The camera unit sits in a handle attached to the laryngoscope blade and is connected by a wire to a TFT video monitor. It allows for both direct and indirect laryngoscopy and the low profile of the original British Macintosh blades may prove advantageous in patients with limited mouth opening.

Results

A total of 108 patients were enrolled in the study but for various reasons only 94 completed the study (post hoc power 97%). In 89 patients a size 3 Macintosh laryngoscopewas used while a size 4 blade was used in the remaining 5 patients. With direct laryngoscopy the glottic view was considered unsatisfactory in 40 patients (42%), but this was the case in only 15 patients (16%) when video laryngoscopy was used (p<0.0001). Endotracheal tube placement was successful in all but one patient where the Bonfils intubation fiberscope needed to be employed. No complications related to the C-MAC system were observed.

Conclusions

Compared to direct laryngoscopy with a Macintosh laryngoscope blade in unselected patients undergoing ENT surgery and thus patients more susceptible to an unexpected difficult airway than a general patient population, the mobile C-MAC video laryngoscope significantly enhanced laryngeal view. Using RAE tracheal tubes seems to compensate the unfavorable deviation of optical and anatomical axes when indirect laryngoscopy is performed with the C-MAC system.     

Initial evaluation of a new optic laryngoscope blade

We report on a new optic laryngoscope blade that provides two views of the larynx during tracheal intubation. The availability of an alternative direct view of the larynx may improve the ability of anesthesia providers to observe the tracheal tube passing through the vocal cords when using a Macintosh laryngoscope blade. The optic port improved visualization of passage of the endotracheal tube in obese patients. However, further studies are needed in patients with difficult airways to determine whether this new blade will ease the ability of practitioners to insert a tracheal tube.     

Brief report: Tracheal intubation using the Bonfils intubation fibrescope or direct laryngoscopy for patients with a simulated difficult airway

BACKGROUND: The Bonfils intubation fibrescope (BIF), a rigid, straight and reusable fibreoptic device, is being used increasingly to facilitate endotracheal intubation after direct laryngoscopy has failed. We tested the hypothesis that, with the BIF compared to direct laryngoscopy, the rate of failed endotracheal intubation could be reduced in patients with a difficult airway, simulated by means of a rigid cervical immobilization collar. METHODS: Seventy-six adults undergoing elective gynecological surgery under general anesthesia were randomly assigned to have endotracheal intubation, facilitated with either a standard size 3 Macintosh laryngoscope blade, or the BIF. A rigid cervical immobilization collar was used to simulate a difficult airway, by reducing mouth opening and limiting neck extension. If endotracheal intubation could not be achieved within two attempts, the cervical collar was removed, and direct laryngoscopy was performed thereafter, using a Macintosh blade in all subjects. The success rate of endotracheal tube placement was the primary outcome variable. RESULTS: Patient characteristics were similar in the two groups. After neck immobilization, the inter-incisor distance was reduced to 2.6 +/- 0.7 cm (Macintosh) and 2.6 +/- 0.8 cm (BIF). Tube placement was successful in 15/38 (39.5%) patients with a Macintosh blade, and in 31/38 patients with the BIF (81.6%; P = 0.0003). Time required for tube placement was 53 +/- 22 sec (Macintosh) and 64 +/- 24 sec (BIF; P = 0.15). CONCLUSION: The Bonfils intubation fibrescope is a more effective intubating device for patients with immobilized cervical spine and significantly limited inter-incisor distance, when compared to direct laryngoscopy.     

Design evaluation of commonly used rigid and levering laryngoscope blades

BACKGROUND: The shape of a laryngoscope blade affects the exposition of the larynx. This study evaluates and compares some rigid and levering blade designs based on previous investigative X-ray laryngoscopic studies. METHODS: Five rigid laryngoscope blades (Miller #3, Standard Macintosh #3, Classical Macintosh #4 and English-Macintosh #3 and #4) and two levering laryngoscope blades (McCoy in neutral and maximally elevated positions and Flexiblade in three basic positions: straight, neutral, and maximally curved) were evaluated. This study assesses two parameters derived from the depth of insertion: the eye line deviation from the ideal straight view line to the vocal cords, and the space occupied by the blade behind the mandible, which affects the contact of the blade tip with the base of the tongue. RESULTS: The best results on larynx exposition were produced by the English-Macintosh #4 at all insertion depths between 5 and 14 cm. It surpassed the Classical Macintosh #4 and both the English and Standard Macintosh #3. Although the Miller and the Flexiblade in a straight position afford a nearly ideal view line, both blades reduce the space reserved for the tongue behind the mandible. The McCoy with its tip maximally elevated provides limited view, while activation of the Flexiblade provides various ranges of larynx exposition. CONCLUSION: The difference in shape and design of Macintosh blades affects their performance. The distal portion of a large-sized curved blade is more effective than the full length of a shorter blade. The #4 English Macintosh is a better choice for routine clinical use. The Flexiblade performs as a multiblade device and can therefore be used for both routine and difficult intubations.     

A comparison of tracheal intubation using the Airtraq or the Macintosh laryngoscope in routine airway management: A randomised, controlled clinical trial

The Airtraq laryngoscope is a novel single use tracheal intubation device. We compared the Airtraq with the Macintosh laryngoscope in patients deemed at low risk for difficult intubation in a randomised, controlled clinical trial. Sixty consenting patients presenting for surgery requiring tracheal intubation were randomly allocated to undergo intubation using a Macintosh (n = 30) or Airtraq (n = 30) laryngoscope. All patients were intubated by one of four anaesthetists experienced in the use of both laryngoscopes. No significant differences in demographic or airway variables were observed between the groups. All but one patient, in the Macintosh group, was successfully intubated on the first attempt. There was no difference between groups in the duration of intubation attempts. In comparison to the Macintosh laryngoscope, the Airtraq resulted in modest improvements in the intubation difficulty score, and in ease of use. Tracheal intubation with the Airtraq resulted in less alterations in heart rate. These findings demonstrate the utility of the Airtraq laryngoscope for tracheal intubation in low risk patients.     

Pentax-AWS improves laryngeal view compared with Macintosh blade during laryngoscopy and facilitates easier intubation

BACKGROUND: The PENTAX-AWS (AWS), combined with PBLADE is a novel tracheal intubation device which allows indirect visualization of the vocal cords without the alignment of the oral, pharyngeal axes required for direct laryngoscopy. Intubation procedure can be monitored on a built-in CCD monitor. METHODS: We compared the laryngeal view obtained with the Macintosh laryngoscope with that obtained with the AWS in 100 patients scheduled for elective anesthesia. Laryngeal view was determined by Cormack & Lehane classification modified by Cook, first using the Macintosh laryngoscope with the patient's head and neck in the sniffing position, followed by the AWS with the head and neck in a neutral position. The time taken to pass the endotracheal tube, the incidence of tube impingement on the arytenoids and the total number of intubation attempts were also recorded. RESULTS: The best laryngeal view obtained with the Macintosh laryngoscope in 100 cases were Grade I: 65, IIa: 16, IIb: 8, IIIa: 6, IIIb: 5, IV: 0. With AWS, the laryngeal views obtained were all grade I. The total time to pass the tube with the AWS was 19.5 +/- 7.9 s and the number of intubation attempts was 1.05 +/- 0.2. The Cormack grade obtained with the Macintosh laryngoscope did not affect the AWS view. The tube touched the right arytenoid in 5 cases but successful intubation was achieved by adjusting the blade direction. CONCLUSIONS: We conclude that the PENTAX-AWS provides a better laryngeal view than the Macintosh laryngoscope and facilitates easier intubation under vision in a higher proportion of patients.     

Malposition of the epiglottis after tracheal intubation via the intubating laryngeal mask

The intubating laryngeal mask has been reported to be a successful method of tracheal intubation although advancement of the tracheal tube via the laryngeal inlet into the trachea cannot be seen. Damage to the larynx or other tissues may occur during blind passage of a tracheal tube. We report a case in which the tracheal tube, advanced blindly, tucked the epiglottis into the laryngeal inlet, resulting in oedema of the epiglottis. This case illustrates the potential for airway obstruction after extubation when using the intubating laryngeal mask as a blind intubation guide.      

Evaluación del videolaringoscopio Airtraq como dispositivo de rescate tras laringoscopia directa difícil

Background and objectives

Unexpected difficult tracheal intubation and failure to intubate are among the leading causes of anesthesia-related morbidity and mortality. This study was undertaken to evaluate the effectiveness of the Airtraq video laryngoscope for tracheal intubation after difficult direct laryngoscopy.

Epiglottic prolapse induced by lighted stylet tracheal intubation

We report a case of epiglottic prolapse induced by lighted stylet tracheal intubation perceived by following upper gastrointestinal endoscopy. A 68-year-old male was to undergo endoscopic mucosal resection (EMR) under general anesthesia for a superficial orolarynx cancer spreading over the root of the tongue. Because the mucosal change was so minimal, intubation was performed with a lighted stylet instead of a direct laryngoscope, to prevent its metal blade spoiling the delicate endoscopic findings. After intubation, endoscopy revealed that the epiglottis folded down completely into the laryngeal vestibule. Immediate extubation with a ventilating tube exchanger failed to turn the entrapped epiglottis back to normal, and the inlet of the larynx remained obstructed. After reintubation, the epiglottis was restored to its normal position with endoscopic forceps. The postoperative course was uneventful and he was discharged on the sixth postoperative day. Retrospective evaluation of preoperative gastrointestinal endoscopy showed the epiglottis was flat and thin enough to have a tendency to become attached to the posterior pharynx wall, even though the procedure was performed in the decubitus position. Epiglottic prolapse induced by lighted stylet tracheal intubation is a quite rare complication but we should be aware of it as a potential injury which could cause upper airway obstruction if not recognized before extubation.     

Displacement of the epiglottis during intubation with the Pentax-AWS Airway Scope

The Pentax-AWS system is a rigid indirect video laryngoscope with integrated tube guidance. Complications associated with this device are not well understood. We report two cases of epiglottis malposition during intubation with the Pentax-AWS. The standard technique of using the Pentax-AWS system involves direct elevation of the epiglottis for exposure of the vocal cords. The blade tip should be passed posterior to the epiglottis for laryngeal exposure, but pressure on the anterior surface of the epiglottis by the tip can rarely happen even during the correct maneuver. Although the Pentax-AWS provides clear images of the airway structures, it is sometimes difficult to observe the epiglottis continuously because the camera is located beneath the blade tip. Consequently, the view of the epiglottis from the camera may be impeded by the blade tip and may result in undiagnosed epiglottis malposition. The AWS’s structural feature and its approach to the larynx can be associated with increased chance of unexpected epiglottis folding. It is particularly important to confirm normal position of the epiglottis during withdrawal of the device to prevent this complication.