A comparison of the Seeing Optical Stylet and the gum elastic bougie in simulated difficult tracheal intubation: a manikin study

Management of the difficult airway is one of the major challenges that anaesthetists face. The flexible fibreoptic scope is widely available but its use requires a level of skill, training and continued practice that is not universally found in all anaesthetists, particularly trainees. The Seeing Optical Stylet is a new, semirigid fibreoptic stylet 'scope. We compared the Seeing Optical Stylet with a gum elastic bougie in a simulated Cormack and Lehane Grade 3 laryngoscopy in a manikin. Forty-four anaesthetists were timed while intubating the manikin's trachea with both devices. The mean (SD) time taken with the Seeing Optical Stylet was 20.8 (9.3) s and with the bougie 30 (19.8) s (p = 0.001). Oesophageal intubation occurred six times with the bougie but did not occur with the Seeing Optical Stylet (p = 0.011). We conclude that the Seeing Optical Stylet may be superior to the bougie in difficult tracheal intubation. We feel that the results of this manikin trial are sufficiently encouraging to proceed to a clinical trial in patients.     

A simple fibreoptic assisted laryngoscope for paediatric difficult intubation: a manikin study*

The fibreoptic assisted laryngoscope is a new airway device. We compared the fibreoptic assisted laryngoscope with the Bullard laryngoscope, Macintosh laryngoscope and fibreoptic bronchoscope in a manikin with a simulated Cormack and Lehane Grade 4 laryngoscopic view. Eighteen anaesthetists intubated the manikin’s trachea using these devices and the success rate of intubation was measured. They were then asked to rate the subjective difficulty of intubation. The success rate (95% confidence interval) was 100% (94.6–100) with the fibreoptic assisted laryngoscope, 88.9% (80.5–97.3) using the Bullard laryngoscope, 37.0% (24.1–49.9) with the Macintosh laryngoscope, and 22.2% (11.1–33.3) using the fibreoptic bronchoscope. Tracheal intubation using the fibreoptic assisted laryngoscope or Bullard laryngoscope is easier than that using the Macintosh laryngoscope or fibreoptic bronchoscope by subjective difficulty score. All of the intubations were successful with the fibreoptic assisted laryngoscope without practice. These results suggest that fibreoptic assisted laryngoscope may be a useful tool for paediatric difficult intubation.     

Evaluation of the new Viewmax laryngoscope in a simulated difficult airway

BACKGROUND: In this study, we evaluated the learning curve and performance of the Viewmax laryngoscope during simulated difficult laryngoscopy in an intubation manikin (Laerdal Airway Management Trainer). METHODS: To determine the learning curve, 25 anaesthesiologists without previous experience with the Viewmax laryngoscope performed 10 successive intubations in an intubation manikin with a normal airway. Time to intubation and failed intubation attempts were recorded. Another manikin was modified to enable comparison of the Viewmax laryngoscope with Macintosh and McCoy laryngoscopes. The time to intubation, number of failed intubation attempts, modified Cormack and Lehane (MCL) laryngeal view grading, percentage of glottic opening (POGO score), use of gum elastic bougie and subjective rating of degree of difficulty were recorded. RESULTS: The learning curve for the Viewmax laryngoscope showed a progressive decrease in time to successful intubation and reached a plateau at the sixth attempt. In simulated difficult laryngoscopy, the Viewmax laryngoscope demonstrated significantly better laryngeal view than the Macintosh and McCoy laryngoscopes in terms of MCL grading (Macintosh, P = 0.01; McCoy, P < 0.01) and POGO score (Macintosh, P < 0.01; McCoy, P < 0.01). The time required for intubation in simulated difficult laryngoscopy for the Viewmax laryngoscope was significantly longer than that for the Macintosh (P = 0.02) and McCoy (P < 0.01) laryngoscopes. There was no significant difference in the degree of difficulty, number of failed intubations and use of gum elastic bougie. CONCLUSION: When compared with the Macintosh and McCoy laryngoscopes in a manikin, the Viewmax laryngoscope appears to improve the view of the larynx but requires a longer time for tracheal intubation.     

Intubation of infants with Pierre Robin syndrome: the use of the paraglossal approach combined with a gum-elastic bougie in six consecutive cases

Infants with Pierre Robin syndrome are known to be difficult to intubate. We evaluated the paraglossal approach combined with a gum elastic bougie for intubation of these infants. Whilst under general anaesthesia, a conventional laryngoscopy was performed; if it failed to obtain a laryngoscopic grade I or II view, intubation was attempted using a paraglossal approach and a gum elastic bougie. Six consecutive infants were studied. Conventional laryngoscopy failed in all infants whilst the paraglossal approach combined with a gum elastic bougie was successful in five of the cases. The paraglossal approach combined with a gum elastic bougie made intubation easy in most children with severe Pierre Robin syndrome and difficult laryngoscopy. Therefore we recommend this as the first line for airway management in such children. However, a fibreoptic bronchoscope and an anaesthetist trained in fibreoptic intubation must still be present when dealing with severe Pierre Robin syndrome infants.     

A comparison of the Pentax Airway Scope™ with the Airtraq™ in an infant manikin

We compared the Pentax Airway Scope(TM) with the Airtraq(TM) optical laryngoscope in an infant manikin. Twenty-three anaesthetists randomly performed tracheal intubation: at rest, (a) with the Airway Scope and (b) with the Airtraq; and during chest compressions, (c) with the Airway Scope and (d) with the Airtraq. The success rate, modified Cormack and Lehane classification for glottic view, time taken to view the glottis, and time to place the tracheal tube were recorded. There was no difference in intubation success rate or quality of glottic view between the two devices. The median (IQR [range]) time taken to obtain a view of the glottis was 4.5 (3.7-6.4 [1.8-14.0]) s using the Airway Scope compared with 7.1 (5.5-9.6 [3.3-12.0]) s using the Airtraq (p = 0.001), and to successful placement of the tracheal tube was 8.3 (6.8-9.4 [3.7-20.7]) s using the Airway Scope compared with 11.2 (10.4-13.8 [4.9-23.7]) s using the Airtraq (p = 0.001). During chest compressions, the median (IQR [range]) time taken to view the glottis was 5.1 (4.0-7.2 [2.0-12.4]) s using the Airway Scope compared with 7.5 (5.0-13.2 [4.2-26.4]) s using the Airtraq (p = 0.006), and to successful placement of the tracheal tube was 9.5 (6.6-13.7 [4.5-16.2]) s using the Airway Scope compared with 11.7 (9.1-18.1 [6.2-37.4]) s using the Airtraq (p = 0.022). We conclude that both devices provided good quality views of the glottis and successful tracheal intubation in an infant manikin both at rest and during external chest compressions. Use of the Airway Scope resulted in a shorter time to view the glottis and perform successful tracheal intubation compared with the Airtraq.     

The rigid nasendoscope as a tool for difficult tracheal intubation: a manikin study

We examined the use of the 30 degrees rigid nasendoscope in aiding difficult tracheal intubations. A Cormack and Lehane grade 4 difficult intubation (no view of glottis or epiglottis) was set up on a manikin. After 10 s of tuition, 40 anaesthetists attempted to pass a standard gum elastic bougie between the cords, with and without the nasendoscope, in randomised order. A bougie curved to an 'optimal curve' was also tested. Using the standard bougie 13/40 (33%) passed the bougie between the cords without the nasendoscope, compared with 31/40 (78%) when using the nasendoscope (p < 0.001). The 'optimal curve' bougie resulted in 29/40 (73%) and 39/40 (98%) success rates without and with the nasendoscope, respectively (p = 0.004). The nasendoscope is a simple and easy to use tool in grade 4 intubation, and results are improved further by the use of an 'optimal curve' bougie.     

To shape or not to shape...simulated bougie-assisted difficult intubation in a manikin

Thirty anaesthetists attempted to place a derived 'optimal' curve bougie or a straight bougie in the trachea of a manikin, in a randomised cross-over study. A Grade 3 Cormack and Lehane laryngoscopic view was simulated. The anaesthetists were blinded to success (tracheal placement) or failure (oesophageal placement). The success rates with the curved and straight bougies were 83 and 7%, respectively, giving a difference (95% confidence interval) of 77% (54-87%) between the two bougies (p < 0.0001). On a separate occasion, under identical laboratory conditions, 30 anaesthetists attempted to place a straight coudé (angled)-tipped bougie or a straight straight-tipped bougie in the trachea of a manikin. The success rates with the coudé- and straight-tipped bougies were 43 and 0%, respectively, giving a difference (95% confidence interval) of 43% (21-61%) between the two bougies (p < 0.001). These results suggest that bougies used to facilitate difficult intubation should be curved and have a coudé tip.     

A new practical classification of laryngeal view

A new practical classification of laryngeal view at laryngoscopy is presented and evaluated. The best laryngeal view obtained with or without anterior laryngeal pressure is recorded. The laryngeal view is easy (E) when the laryngeal inlet is visible. The view is restricted (R) when the posterior glottic structures (posterior commissure or arytenoids) are visible or the epiglottis is visible and can be lifted; this includes some grade 2 and some grade 3 views as classified by Cormack and Lehane. A difficult (D) view is present when the epiglottis cannot be lifted or when no laryngeal structures are visible. Five hundred patients were studied. Laryngoscopy, with the patient anaesthetised and paralysed, was performed with a Macintosh laryngoscope. If the vocal cords were not visible, a gum elastic bougie was used to aid intubation. Other aids were used only if this did not allow intubation. Each laryngeal view was graded according to the new classification and that of Cormack and Lehane. Intubation was timed and the equipment needed to facilitate intubation was recorded. The new classification stratified increasing difficulty with intubation (time for intubation longer and increasingly complex methods needed) better than the Cormack and Lehane classification. The new classification is as sensitive and more specific than the Cormack and Lehane classification in predicting difficult intubation. It is also more sensitive and more specific in predicting easy intubation.     

Comparison of malleable stylet and reusable and disposable bougies by paramedics in a simulated difficult intubation

In a randomised crossover study, 60 ambulance paramedics attempted tracheal intubation of a manikin model of a Cormack and Lehane grade 3/4 view using a Portex stylet, Portex and Frova single-use bougies, and a Portex reusable bougie. Tracheal intubation within 30 s was achieved by 34/60 (57%) using the stylet, 18/60 (30%) using a Portex single-use bougie, 16/60 (27%) using a Frova single-use bougie and 5/60 (8%) using a Portex reusable bougie. The proportion intubating within 30 s was significantly higher with the stylet compared with any bougie (p < 0.001), but significantly lower with a Portex reusable bougie than any other device (p < 0.004). Participants rated the Portex reusable bougie as significantly more difficult to use than the other devices (p < 0.001). There was no evidence of a relationship between previous experience and success rate for any device.     

Simulated difficult intubation

A randomised study was carried out to compare the efficacy of the gum elastic bougie and the stylet in a simulated difficult intubation. A laryngoscopy assessment, as described by Cormack and Lehane, was made in 100 patients. A Grade 3 view was then simulated. In the Bougie First Group (50 patients) two attempts were made to pass a gum elastic bougie and a tracheal tube into the trachea. If these first two attempts were not successful, two further attempts at intubation were allowed with a stylet placed in the tracheal tube. In the Stylet First Group (50 patients) the order was reversed. After two attempts the tube was correctly placed in the trachea in 96% of cases in the Bougie First Group compared to only 66% of cases in the Stylet First Group (p < 0.001). We recommend that a gum elastic bougie should be readily available and that anaesthetists should use it in preference to a stylet whenever a good view of the glottis is not immediately available.     

A comparison of simulated difficult intubation with multiple-use and single-use bougies in a manikin

In a randomised cross-over study, 20 anaesthetists attempted to place a multiple- or single-use bougie in the trachea of a manikin, in which a grade 3 Cormack and Lehane laryngoscopic view was simulated. The anaesthetists made two attempts at placement with each bougie and were blinded to success (tracheal placement) or failure (oesophageal placement). The success rates for the first attempts with the multiple- and single-use bougies were 85 and 15%, respectively [mean (95% CI) difference between the two bougies 70% (40-84%); p < 0.001]. The success rates for the second attempts were similar to those for the first attempts with both bougies. There is an increased risk of failure to intubate the trachea when using a single-use bougie, and this must be weighed against the unquantified risk of cross-infection from prions when using a multiple-use bougie.     

Airtraq vs standard laryngoscopy by student paramedics and experienced prehospital laryngoscopists managing a model of difficult intubation

Two consecutive, randomised, cross-over trials compared intubation success rates in third-year paramedic students and experienced prehospital practitioners using the Airtraq or a Macintosh laryngoscope with flexible stylet in a manikin model of a Cormack and Lehane grade III/IV laryngoscopic view. First-time intubation rates for the Macintosh and Airtraq for students were 0/23 (0%) vs 10/23 (44%) (44% difference, 95% CI 26-63%, p < 0.001) and for experienced laryngoscopists were 14/56 (25%) vs 47/56 (84%) (59% difference, 95% CI 42-72%, p < 0.0001), respectively. First-time oesophageal intubation rates for students were 15/23 (65%) vs 3/23 (13%) (-52% difference, 95% CI -25 to -72%, p < 0.001) and for experienced practitioners 9/56 (16%) vs 0/56 (0%) (-16% difference, 95% CI -9 to -28%, p = 0.0014). Student paramedics and experienced prehospital laryngoscopists managing a manikin model of a grade III/IV view had increased first-time intubation rates and had lower rates of oesophageal intubation with the Airtraq compared with a standard laryngoscope.     

A paramedic study comparing the use of the Airtraq, Airway Scope and Macintosh laryngoscopes in simulated prehospital airway scenarios

In a randomised, cross-over study, we compared the use of the Airtraq , Airway Scope and Macintosh laryngoscopes by paramedics for tracheal intubation in three simulated prehospital scenarios. Fifty-four paramedics were invited to take part. When evaluated in a difficult airway manikin, median IQR [range] time to intubation with the Airtraq (21 (16-37 [6-80] s) and Airway Scope (16 (5-75 [12-23] s) was shorter than that with the Macintosh laryngoscope (39 (25-54 [7-120] s; p < 0.0001). The success rate within 30 s was greater with the Airtraq (61%) and Airway Scope (93%) than with the Macintosh laryngoscope (22%; p < 0.0001). When used for a standard intubation and in the sitting position, we found minimal differences among the three laryngoscopes. We conclude that the Airway Scope and Airtraq have significant advantages over the Macintosh laryngoscope and that of the two, the Airway Scope is the more effective device to use in the prehospital environment.     

Videolaryngoscopy vs. direct laryngoscopy use by experienced anaesthetists in patients with known difficult airways: a systematic review and meta‐analysis

Experienced anaesthetists can be confronted with difficult or failed tracheal intubations. We performed a systematic review and meta‐analysis to ascertain if the literature indicated if videolaryngoscopy conferred an advantage when used by experienced anaesthetists managing patients with a known difficult airway. We searched PubMed, MEDLINE, Embase and the Cochrane central register of controlled trials up to 1 January 2017. Outcome parameters extracted from studies were: first‐attempt success of tracheal intubation; time to successful intubation; number of intubation attempts; Cormack and Lehane grade; use of airway adjuncts (e.g. stylet, gum elastic bougie); and complications (e.g. mucosal and dental trauma). Nine studies, including 1329 patients, fulfilled the inclusion criteria. First‐attempt success was greater for all videolaryngoscopes (OR 0.34 (95%CI 0.18–0.66); p = 0.001). Use of videolaryngoscopy was associated with a significantly better view of the glottis (Cormack and Lehane grades 1 and 2 vs. 3–4, OR 0.04 (95%CI 0.01–0.15); p < 0.00001). Mucosal trauma occurred less with the use of videolaryngoscopy (OR 0.16 (95%CI 0.04–0.75); p = 0.02). Videolaryngoscopy has added value for the experienced anaesthetist, improving first‐time success, the view of the glottis and reducing mucosal trauma.     

Evaluation of a single-use intubating videoscope (Ambu aScope ™) in three airway training manikins for oral intubation, nasal intubation and intubation via three supraglottic airway devices

We compared the Ambu aScope? with a conventional fibrescope in two simulated settings. First, 22 volunteers performed paired oral and nasal fibreoptic intubations in three different manikins: the Laerdal Airway Trainer, Bill 1 and the Airsim (a total of 264 intubations). Second, 21 volunteers intubated the Airway Trainer manikin via three supraglottic airways: classic and intubating laryngeal mask airways and i‐gel (a total of 66 intubations). Performance of the aScope was good with few failures and infrequent problems. In the first study, choice of fibrescope had an impact on the number of user‐reported problems (p = 0.004), and user‐assessed ratings of ease of endoscopy (p < 0.001) and overall usefulness (p < 0.001), but not on time to intubate (p = 0.19), or ease of railroading (p = 0.72). The manikin chosen and route of endoscopy had more consistent effects on performance: best performance was via the nasal route in the Airway Trainer manikin. In the second study, the choice of fibrescope did not significantly affect any performance outcome (p = 0.3), but there was a significant difference in the speed of intubation between the devices (p = 0.02) with the i‐gel the fastest intubation conduit (mean (SD) intubation time i‐gel 18.5 (6.8) s, intubating laryngeal mask airway = 24.1 (11.2) s, classic laryngeal mask airway = 31.4 (32.5) s, p = 0.02). We conclude that the aScope performs well in simulated fibreoptic intubation and (if adapted for untimed use) would be a useful training tool for both simulated fibreoptic intubation and conduit‐assisted intubation. The choice of manikin and conduit are also important in the success of such training. This manikin study does not predict performance in humans and a clinical study is required.     

A randomised clinical trial comparing the flexible fibrescope and the Pentax Airway Scope (AWS)® for awake oral tracheal intubation

We compared awake fibreoptic intubation with awake intubation using the Pentax Airway Scope^® in 40 adult patients. Sedation was achieved using a target‐controlled remifentanil infusion of 1–5 ng.ml^?1 and midazolam. The airway was anaesthetised with lidocaine spray and gargle. The total procedure time – a composite of sedation time, topical anaesthesia time and intubation time – was recorded. The operator's impression of the ease of the procedure and the patients' reported comfort were recorded on a 0–100 mm visual analogue scale. The median (IQR [range]) for total procedure time was 900 (739–1059 [616–1215]) s with the fibrescope and 651 (601–720 [498–900]) s with the Pentax Airway Scope (p = 0.0001). The median (IQR [range]) intubation time was 420 (283–480 [120–608]) s with the fibrescope and 183 (144–220 [107–420]) s with the Pentax Airway Scope (p = 0.0002). The median (IQR [range]) visual analogue scores for the operator's ease of intubation for the fibrescope and Pentax Airway Scope were 83.6 (72.0–98.0 [49.0–100.0]) and 86.8 (84.0–91.0 [61.0–100.0]), respectively (p = 0.3507). The median (IQR [range]) visual analogue score for patient comfort was 85.5 (81.0–97.0 [69.0–100.0]) and 79.4 (74.0–85.0 [59.0–100.0]) for the fibrescope and Pentax Airway Scope, respectively (p = 0.06). Total procedure time was significantly shorter with the Pentax Airway Scope compared with the fibrescope, with no difference in procedure difficulty or patient discomfort.     

Difficult fiber-optic intubation in a patient with giant neck masses: The role of McCoy laryngoscope in elevating compressed laryngeal aperture

Airway management in patients with giant neck masses is usually a challenge to anesthesiologists. A giant neck mass could compress the airway and thus impede endotracheal intubation. We encountered a situation where the giant neck masses of a patient pushed the epiglottis posteriorly toward the posterior pharyngeal wall and compressed the laryngeal aperture narrowing after anesthetic induction, causing direct laryngoscopic intubation and sequential fiber-optic intubation failed. The neck masses twisted the aryepiglottic fold tortuously and clogged the laryngeal aperture tightly, making a flexible fiber-optic bronchoscope unable to pass through the laryngeal aperture. Later, we utilized a McCoy laryngoscope alternately to lift the compressed larynx up and away from the posterior pharyngeal wall, creating a passage and completing endotracheal intubation successfully with the aid of a gum elastic bougie. Our case suggested that the tilting tip blade of the McCoy laryngoscope could lever the tongue base up against the tumor mass compression to improve laryngeal views and facilitate endotracheal intubation when a difficult fiber-optic intubation was encountered on a compressed laryngeal aperture.     

Accuracy,intra‐ and inter‐rater reliability of three scoring systems for the glottic view at videolaryngoscopy

An accurate and reproducible recording of laryngoscopic view at tracheal intubation is an important aspect of anaesthetic practice. Unlike direct laryngoscopy, in which the view achieved by the line of sight directly relates to the ease of intubating the trachea, videolaryngoscopy can create a situation in which the view is good, but intubation difficult or impossible. Communicating this to a subsequent anaesthetist is important. We compared three scoring systems: Cormack and Lehane; POGO (percentage of glottic opening); and the Fremantle score, as used by 74 critical care doctors rating 30 anonymised videos of videolaryngoscopic intubations. Accuracy (degree of agreement of score with an expert panel assessment) was higher for POGO (75.5%) and the Fremantle score (73.9%) than for Cormack and Lehane (65.4%; p < 0.001). Intra‐rater reliability (mean free marginal Kappa for ordinal scores and mean Cronbach's Alpha for continuous score) was higher for Fremantle score (0.796) and Cormack and Lehane (0.773) than POGO (0.693). Inter‐rater reliability for Fremantle score (0.618) and POGO (0.614) were similar and higher than the inter‐rater reliability of Cormack and Lehane 0.464 (p < 0.001). The higher accuracy and inter‐rater reliability of POGO and the Fremantle score suggest they are preferable to Cormack and Lehane for use when documenting videolaryngoscopy. The additional information about ease of intubation conveyed by the Fremantle score may support its routine use in recording videolaryngoscopic intubation.     

Ease of tracheal intubation through the intubating laryngeal mask during manual in-line head and neck stabilisation

We studied 40 anaesthetised and paralysed patients, in a randomised manner, to compare the ease of tracheal intubation either using a Macintosh laryngoscope and gum elastic bougie (group C) with the ease of tracheal intubation through the intubating laryngeal mask using a fibreoptic bronchoscope (group L), during manual in-line stabilisation of the patient's head and neck. In both groups, a maximum of 120 s was allowed for attempts at tracheal intubation. The ease of placement of the intubating laryngeal mask or tracheal intubation was assessed using a 100-mm visual analogue scale (VAS). In patients in whom tracheal intubation succeeded, time for intubation was measured. The intubating laryngeal mask was placed successfully in 19 of 20 patients, with the median VAS of 18 mm (95% CI: 13-32 mm). The success rate of tracheal intubation in group L (17 patients) was significantly higher than in group C (nine patients) (p < 0.01), tracheal intubation in group L was significantly easier than intubation in group C (p < 0.001; 95% CI for difference in VAS: 18-68 mm) and time taken for tracheal intubation was significantly shorter in group L than in group C (95% CI for difference: 8-50 s).     

Performance of the Airtraq™ laryngoscope after failed conventional tracheal intubation: a case series

Background: The Airtraq^™, a new disposable indirect laryngoscope, was evaluated in patients with difficult intubation.
Methods: The Airtraq^™ was used in 47 patients with predicted or unpredicted difficult intubation after failed orotracheal intubation performed by two senior anaesthesiologists with the Macintosh laryngoscope.
Results: Tracheal intubation with Airtraq^™ was successful in 36 patients (80%). The Cormack and Lehane score was IIb–III in 35 patients, and IV in 12 patients, with the Macintosh laryngoscope, while Cormack and Lehane score was I–IIa in 40 patients, IIb–III in three and IV in four with Airtraq^™. A gum elastic bougie was used to facilitate tracheal access in one-third (11/36) of the cases. Orotracheal intubation was not possible with Airtraq^™ in nine cases, five of whom had a pharyngeal, laryngeal or basal lingual tumour.
Conclusion: In patients with difficult airway, following failed conventional orotracheal intubation, Airtraq^™ allows securing the airway in 80% of cases mainly by improving glottis view. However, the Airtraq^™ does not guarantee successful intubation in all instances, especially in case of laryngeal and/or pharyngeal obstruction.