The use of the BERCI DCI® Video Laryngoscope for teaching novices direct laryngoscopy and tracheal intubation*

Authors


  • *

    Presented at the May 2007 Society of Anaesthetists of South-west Region Annual Conference in Budapest.

Dr Daniel Low
E-mail: Daniel.low1@mac.com

Summary

Traditional teaching of laryngoscopy is difficult due to the trainer and trainee lacking a shared view. The Karl Storz BERCI DCI® Video Laryngoscope provides a video image for the trainer and a direct view identical to that of a standard laryngoscope for the trainee. Forty-nine novice subjects were randomly assigned to a control group (n = 24) taught using a standard Macintosh laryngoscope or a study group (n = 25) taught using the Video Laryngoscope. Following training all subjects were assessed using a standard laryngoscope. Under simulated difficult airway conditions the study group performed better in terms of number of attempts (p = 0.02), number of repositioning manoeuvres required (p = 0.046) and teeth trauma (p = 0.034). The study group were more confident of the success of their tube placement (p = 0.035), found it easier than the control group (p = 0.042) and had improved knowledge of airway anatomy (p = 0.011). We conclude that video laryngoscopy confers benefits in the teaching of tracheal intubation.

Direct laryngoscopy is one of the most important airway management skills that anaesthetists require. Teaching this skill has always presented a challenge because the teacher and pupil do not have identical views of the anatomy. The technical development of mechanical systems to facilitate tracheal intubation began when Miller and Macintosh placed light sources at the end of metal blades to help visualise the laryngeal inlet [1, 2]. This technology requires the user to have a line of sight alongside the blade to obtain a view. The view is limited by the structures through which the blade passes (the mouth, tongue and oropharynx) and is further limited by attempts to advance the tracheal tube. The viewing angle obtained using this method has been measured at 15°. This method of visualising the laryngeal inlet has remained the most widely practised globally because of its dependability and simplicity. A shared view was first achieved with a head-mounted camera (the Airway Cam; Airway Cam Technologies, Wayne, PA, USA) [3]. Unfortunately, this method is unwieldy, the camera interfering with the trainee's line of sight and the view still limited to the 15° of a standard Macintosh blade. A superior system has been developed in which both a light source and microcamera are positioned at the tip of the laryngoscope. Two systems are currently available using this technology: one utilising a special laryngoscope blade (the GlideScope– Verathon Medical, Bothell, WA, USA) and the other using a standard Macintosh blade (the Karl Storz BERCI DCI® Video Laryngoscope; Karl Storz, Tuttlingen, Germany) (Fig. 1).

Figure 1.

 BERCI DCI Video Laryngoscope blade.

The advantages of video systems over direct view fibreoptic systems during endoscopic procedures in both surgery and anaesthesia, have become obvious over the last three decades with large, bright, high resolution screens replacing the small monocular eyepiece [4, 5]. Video systems offer six main benefits [5];

  • • technical – a larger, brighter, higher resolution image;
  • • procedural – allows for instruction and demonstration to multiple viewers;
  • • educational – static images or live video feeds can be captured and reviewed;
  • • documentation – pre/intra/post procedural images can be recorded;
  • • research – allows easier comparison between patients/procedures/operators;
  • • user comfort – physical comfort from improved posture.

The BERCI DCI Laryngoscope incorporates a fibreoptic camera lens into the light source of a standard Macintosh blade (Fig. 2). The camera is housed within the laryngoscope handle and the magnified image is displayed on a screen, the user's eye being ‘positioned’ at the tip of the instrument. The customary viewing angle of 15° is thus extended to 80°.

Figure 2.

 Miniature fibreoptic camera lens within light source.

One of the key difficulties of teaching direct laryngoscopy is the lack of a shared view. With the video laryngoscope the trainer and trainee share identical views, allowing the trainer to offer instruction to optimise the view and pass the tracheal tube.

Previous studies have demonstrated advantages of video laryngoscopy in a variety of clinical scenarios. Kaplan et al. [4] demonstrated improvements in the management of the difficult airway using the video laryngoscope. Iwase et al. [6] has shown that novices have a higher success rate intubating the trachea of patients using a video laryngoscope system compared with a standard Macintosh blade. Letivan et al. [7] reported higher intubation success rates in trainee paramedics who viewed a 26-min instructional video made with video laryngoscopy equipment as part of their training.

To our knowledge there have been no studies designed to investigate whether there are any objective improvements in laryngoscopic skills in subjects taught using the video laryngoscope compared to subjects taught using traditional methods.

This study was designed to determine whether using the BERCI DCI Video Laryngoscope as a teaching aid improved the skills of direct laryngoscopy using a standard Macintosh blade.

Methods

Ethical approval was sought but formal submission was not required. Despite this, written informed consent was obtained from all subjects agreeing to participate in the study.

A power study was performed based on data from seven paramedics attending for airway training. They underwent a timed intubation assessment of a Laerdal® Airway Management Trainer (Laerdal, Stavanger, Norway). The standard deviation of their times was calculated and the number required to recruit to determine a performance gain of > 10% difference (with reference to time to intubation) with 90% probability was calculated as 25 per cohort.

A total of 14 trainee paramedics and 35 medical students (with no prior experience of performing tracheal intubation) were recruited into the study. Subjects were divided into three groups of 10–12 and underwent the following training session:

Firstly, a standard lecture was provided in which the context and importance of laryngoscopy and tracheal intubation was explained. This included descriptions of relevant equipment, anatomy and the technique of tracheal intubation. Following the lecture, students were randomly allocated using sealed envelopes into two small groups of five or six: a control group (taught with a standard Macintosh laryngoscope) and a study group (taught with the BERCI DCI Video Laryngoscope).

Each group received a demonstration and verbal instructions on how to perform laryngoscopy and tracheal intubation by their instructor. The use of a gum elastic bougie was demonstrated. Each subject was then allowed five practice intubations using a SimMan® (Laerdal, Kent, UK) manikin with its default airway settings (Table 2). The subjects had to intubate the SimMan with a size 8.0 cuffed oral tracheal tube. Each practice attempt was stopped if it lasted > 120 s.

Table 2.   Data from SimMan (difficult airway scenario). Data are reported as mean (SD) or as n (%).
Parameter assessedControl Group
(n = 24)
Study Group
(n = 25)
  • *

    Statistically significant difference in number of attempts between the two groups (p = 0.020, Mann–Whitney test). The control group had more attempts at intubation than the video group.

Success rate; n (%)21 (87.5)23 (92.0)
For all attempts
 Time; s55.0 (32.2)44.4 (28.3)
Only for successful attempts
 Time; s47.9 (26.5)41.1 (24.5)
No. of attempts; n (%)
 113 (54.2)21 (84)*
 2 9 (37.5) 4 (16)
 3 1 (4.2) 0 (0)
 4 1 (4.2) 0 (0)
No. of repositioning; n (%)
 015 (62.5)22 (88.0)
 1 6 (25.0) 1 (4.0)
 2 0 (0) 2 (8.0)
 2 + 3 (12.5) 0 (0)
Teeth trauma (subjective)
 0 (none) 1 (4.2) 3 (12.0)
 1 (mild) 2 (8.3) 4 (16.0)
 2 (moderate) 6 (25.0)10 (40)
 2 + (severe)15 (62.5) 8 (32)
Bougie used; n (%)20 (83.3)19 (76.0)
Confidence in correct placement;
[0–100%]; mean (SD)
64.6 (30.2)79.4 (26.0)
Perception of difficulty; %
 Easy 0 (0) 2 (8.0)
 Moderate 6 (25.0)11 (44.0)
 Difficult18 (75)12 (48)

The control group subjects used a standard Macintosh laryngoscope for all five practice attempts. They were permitted to use a gum elastic bougie only on their third and fourth attempts.

The study group subjects used the BERCI DCI Video Laryngoscope for their first three attempts (Fig. 3). They used a standard Macintosh laryngoscope (Fig. 4) for their fourth and fifth attempts and they, too, were permitted to use a gum elastic bougie only on their third and fourth attempts. Subjects were encouraged to achieve a direct view through the mouth rather than look at the screen; the instructor used the screen image to direct the subject (Fig. 5). If the subject became disorientated and were unsure of what they were looking at, they were referred to the screen image as a means of re-orientation; they then continued with their intubation attempt using a direct view.

Figure 3.

 Using the BERCI DCI Video Laryngoscope system to intubate a manikin.

Figure 4.

 Direct view with standard Macintosh laryngoscope.

Figure 5.

 On screen view with BERCI DCI® Video Laryngoscope.

All three instructors were of equivalent seniority, all being post fellowship specialist registrars in anaesthesia. They were randomly assigned to which of the groups they instructed.

Immediately following the practice intubations, subjects were individually assessed. They were all required to use a standard Macintosh laryngoscope. The subjects were asked to intubate two manikins – the Laerdal Airway Management Trainer (normal airway) (Table 1) and the SimMan with a simulated difficult airway (neck stiffness and pharyngeal obstruction settings activated) (Table 2). Instructors received written and oral instructions on how to conduct their assessments and were blinded as to which practice group the subject had been in. The following primary and secondary endpoints were assessed.

Table 1.   Data from Laerdal Airway Trainer (normal airway). Data are reported as mean (SD) or as n (%).
Parameter assessedControl Group
(n = 24)
Study Group
(n = 25)
Success rate; n (%)21 (87.5)21 (84)
For all attempts
 Time; s 33.5 (14.7)44.3 (32.4)
Only for successful attempts
 Time; s 30.9 (14.7)38.0 (25.2)
No. of attempts; n (%)
 122 (91.7)22 (91.7)
 2 2 (8.3) 1 (4.2)
 3 0 (0) 1 (4.2)
No. of repositioning; n (%)
 019 (79.2)20 (83.3)
 1 4 (16.7) 0 (0)
 2 0 (0) 2 (8.3)
 2 + 1 (4.2) 2 (8.3)
Teeth trauma [clicks]; n (%)
 012 (50.0)18 (72.0)
 1 5 (20.8) 3 (12)
 2 4 (16.7) 2 (8)
 2 + 3 (12.5) 2 (8)
Bougie used; n (%)11 (45.8)14 (56)
Confidence in correct placement
(0–100%); mean (SD)
78.1 (23.0)84.9 (23.0)
Perception of difficulty; (5%)
 Easy 6 (25.0) 7 (28.0)
 Moderate11 (45.8)10 (40.0)
 Difficult 7 (29.2) 8 (32.0)

Primary endpoints

  • 1Success rate of tracheal intubation (verified by lung inflation).
  • 2Time to tracheal intubation. Time taken was defined by the laryngoscope blade passing between the teeth and the subject verbally indicating completion of intubation.

Secondary endpoints

  • 1Number of intubation attempts (defined by repeated insertion of the laryngoscope into the mouth).
  • 2Number of repositioning manoeuvres (head/pillow adjustments after initial positioning).
  • 3Teeth trauma (either teeth clicks on Laerdal manikin or subjective grading of pressure on the SimMan manikin).
  • 4Incidence of gum elastic bougie use.
  • 5Subject's confidence about correct tube placement (asked to score 0–100% before verifying using lung ventilation).
  • 6Subject's perception of difficulty (asked to score as easy, moderate, difficult, before lung ventilation).

A failed intubation attempt was recorded if the time exceeded 120 s. Subjects were not allowed to verify correct tube placement by ventilating the lungs until the secondary endpoints had been measured.

In addition, subjects were assessed on their ability to identify five anatomical structures (epiglottis, valecula, vocal cords, oesophagus and trachea) from a photograph taken during laryngoscopy of a human airway.

Statistics

Primary endpoint data were analysed using the Fisher's exact test (intubation success rate) and Mann–Whitney test (time to intubation). Secondary endpoint data including anatomy test scores were analysed using the Mann–Whitney test, Fisher's exact test or a Chi-squared test, as appropriate. Continuous data are presented as mean (SD). Categorical and ordinal data are presented as raw numbers and frequencies. Statistical significance for all analyses was set at p < 0.05.

Results

In all, 14 trainee paramedics and 35 4th year medical students were recruited and consented to participate in the study. None had received any clinical training in intubation. The control group (n = 24) had training sessions using standard teaching using a Macintosh laryngoscope (Table 1). The study group (n = 25) had training sessions with the BERCI DCI Video Laryngoscope (Table 2).

There were three failed intubations in the control group and four in the video group. All but two of these (both in the study group) failed before the 120-s time limit. One subject in the study group failed to place the tracheal tube at all and is recorded as having missing data on attempts, repositioning and confidence scores. There was no evidence of any difference between the two groups with all p values > 0.05.

In the SimMan (difficult airway) scenario, analysis of the 44 subjects who successfully intubated the trachea showed the video group to be 7 s faster, on average, than the control group (Table 2). This difference was not significantly different (p = 0.337, independent samples t-test, 2-sided). There is some evidence of a difference between the two groups in number of repositioning manoeuvres (p = 0.046, Mann–Whitney test) with the control group performing more repositioning manoeuvres than the video group. The control group caused more dental trauma during intubation attempts (p = 0.034, Mann–Whitney test). The study group were more confident about correct placement of their tracheal tube before confirming with lung inflation (p < 0.035, Mann–Whitney test 2-sided). There is some evidence that the perception of difficulty was greater in the control group (p = 0.042, 2-sided Mann–Whitney test).

The study group recognised more anatomical structures correctly than did the control group, the statistically significant difference being identification of the oesophagus (Tables 3 and 4).

Table 3.   Data from Anatomy Test score breakdown. Data are reported as n (%).
Structures correctly
identified
Control Group
(n = 24)
Study Group
(n = 25)
  • *

    There was a highly statistically significant difference in the groups (p = 0.001, Fisher's exact test, 2-sided) with 92% of the study group able to identify correctly the oesophagus compared to only 50% of the standard group.

Epiglottis23 (95.8)24 (96)
Valecula16 (66.7)20 (80)
Oesophagus12 (50.0)23 (92.0)*
Trachea24 (100)23 (92)
Vocal cords24 (100)25 (100)
Table 4.   Data from Anatomy Test – overall scores.
 Control GroupStudy Group
  • *

    There was a statistically significant difference in the distribution of scores between the two groups (p = 0.011, Mann–Whitney, 2-sided) with, on average, higher scores in the study group.

Mean4.14.6*
SD0.70.8
Median45

Discussion

It has been suggested that video laryngoscope systems are ideal for teaching the technique of tracheal intubation primarily because of their ability to allow the trainer and trainee to share identical views [4, 6–9]. The trainer can give advice on optimising the view, using the BERCI DCI Video Laryngoscope, and pass the tracheal tube. The view can be further improved by the targeted application of external laryngeal manipulation (such as the backwards-upwards-right-pressure ‘BURP’ manoeuvre) [10].

This study was designed to determine whether using the BERCI DCI Video Laryngoscope as a teaching aid improved the skills of direct laryngoscopy using a standard Macintosh blade. To our knowledge, no previous study has investigated this. The BERCI DCI Video Laryngoscope system was used because it was felt the skills learnt would be more readily transferable to direct laryngoscopy with a standard Macintosh laryngoscope.

Primary endpoints

This study showed differences between the control group (standard Macintosh laryngoscope) and study group (BERCI DCI Video Laryngoscope) under ‘difficult’ airway conditions. The lack of difference in our primary endpoints of time to intubation and success rate may be real. However, the authors felt that it would be advantageous to repeat the study using a dedicated airway manikin, e.g. AirSim (Verathon), and this study is in progress.

Secondary endpoints

With regard to secondary endpoints it has been shown that the study group needed fewer attempts to intubate the trachea, made fewer repositioning manoeuvres and caused less dental trauma than the control group, when under test conditions. This study showed increased confidence in tracheal tube placement in the study group when using a standard Macintosh laryngoscope. In addition, the study group was better at identifying the anatomical structures of the airway than the control group. The authors feel this reflects the improved ability to repeatedly demonstrate the wide angled anatomical view with the BERCI DCI Video Laryngoscope.

Subjective feedback

As trainers, teaching using the video laryngoscope was reported as being relatively straightforward. It made airway anatomy easy to demonstrate (Fig. 6). During individual subject attempts at intubation with the video laryngoscope, the whole group benefited from watching the performance on the monitor. It led to group involvement in the intubation attempt with individuals offering helpful advice, such as ‘a little more to the left’. Unlike the control group, the study group maintained interest through each subject's attempt at intubation due to the dynamic and interactive nature of the teaching session.

Figure 6.

 Comparison of angle of views with standard and video laryngoscope.

Main findings

We believe our findings demonstrate the Macintosh video laryngoscope system to be a useful aid to teaching the complex technique of tracheal intubation. A repeat study with larger numbers and dedicated airway manikins will be of interest. It would also be of interest to investigate skill retention of the subject group assuming, of course, none had further intubation practice. This has implications for infrequent laryngoscopists such as paramedics and emergency physicians. An intubation course for novice anaesthetists is planned where subsequent clinical performance can then be measured.

Implications for training

Teaching with a video laryngoscope is likely to be a useful adjunct for the novice anaesthetist. The reduction in training hours and less opportunity to intubate patients on routine lists (since the advent of the laryngeal mask airway) may make the achievement of competency in laryngoscopy and intubation difficult for a junior anaesthetist. Failed intubations in emergency situations may become more prevalent, with the possibility of significant morbidity and mortality.

With the advent in UK medical training of Modernising Medical Careers (MMC), doctors are expected to demonstrate their abilities and competencies against set standards. One aspect of this assessment is Direct Observation of Procedural Skill (DOPS). The video laryngoscope, with manikin training, may well have a role to play in the training and assessment of the junior anaesthetist's airway skills. Such teaching should be integrated into a programme of airway management, with emphasis always placed on the ability adequately to ventilate and oxygenate a patient before proceeding to more advanced airway manoeuvres.

This study adds to the body of evidence that already exists [4–9] which supports the use of video laryngoscopy for clinical training. This study has demonstrated the improved skill of novices handling a standard Macintosh blade when trained with a BERCI DCI Video Laryngoscope.

Acknowledgements

The authors would like to thank Storz for the free loan of the equipment and Dr Andrew McIndoe for free use of the Bristol Medical Simulation Centre and their manikins. We thank Dr John Cobby for his statistical input. The authors also thank Dr Claire Kaloo for her proof-reading assistance.

Funding for the study was kindly donated from the paramedic research fund from Frenchay Hospital, Bristol.

Conflict of interest

The authors have no conflict of interest in regard to the Karl Storz BERCI DCI video laryngoscope.

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