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Learning Endotracheal Intubation Using a Novel Videolaryngoscope Improves Intubation Skills of Medical Students

Herbstreit, Frank; Fassbender, Philipp; Haberl, Helge; Kehren, Clemens; Peters, Jürgen

doi: 10.1213/ANE.0b013e3182222a66
Economics, Education, and Policy: Research Reports
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INTRODUCTION: Teaching endotracheal intubation to medical students is a task provided by many academic anesthesia departments. We tested the hypothesis that teaching with a novel videolaryngoscope improves students' intubation skills.

METHODS: We prospectively assessed in medical students (2nd clinical year) intubation skills acquired by intubation attempts in adult anesthetized patients during a 60-hour clinical course using, in a randomized fashion, either a conventional Macintosh blade laryngoscope or a videolaryngoscope (C-MAC®). The latter permits direct laryngoscopy with a Macintosh blade and provides a color image on a video screen. Skills were measured before and after the course in a standardized fashion (METI Emergency Care Simulator) using a conventional laryngoscope. All 1-semester medical students (n = 93) were enrolled.

RESULTS: The students' performance did not significantly differ between groups before the course. After the course, students trained with the videolaryngoscope had an intubation success rate on a manikin 19% higher (95% CI 1.1%–35.3%; P < 0.001) and intubated 11 seconds faster (95% CI 4–18) when compared with those trained using a conventional laryngoscope. The incidence of “difficult (manikin) laryngoscopy” was less frequent in the group trained with the videolaryngoscope (8% vs 34%; P = 0.005).

CONCLUSION: Education using a video system mounted into a traditional Macintosh blade improves intubation skills in medical students.

Published ahead of print June 16, 2011

From the Department of Anesthesiology, Universität Duisburg–Essen, University Hospital Essen, Essen, Germany.

Funding: The study was supported by a grant from the Faculty of Medicine, Universität Duisburg–Essen.

The authors declare no conflicts of interest.

Reprints will not be available from the authors.

Address correspondence to Frank Herbstreit, Dr. med., Universität Duisburg– Essen, University Hospital Essen, Klinik für Anästhesiologie, Universitätsklinikum Essen, Hufelandstrasse 55, 45122 Essen, Essen, Germany. Address e-mail to frank.herbstreit@uk-essen.de.

Accepted April 22, 2011

Published ahead of print June 16, 2011

Although endotracheal intubation is regarded as the “gold standard” in emergency airway management, the incidence of unrecognized tube misplacement in an emergency setting is between 6% and 14% in retrospective studies.14 Therefore, medical students should acquire skills in airway management.

Some studies suggest that >50 endotracheal intubations are necessary to achieve a 90% success rate in patients.5 Thus, teaching endotracheal intubation is time consuming and difficult to manage in today's tight operating room schedules. A method of teaching advanced airway management with satisfactory results but requiring less practice overcoming these obstacles would therefore be welcome.

Several devices may improve the airway skills of medical students. For example, higher success rates have been achieved by students using a glide scope as an alternative tool for endotracheal intubation when compared to traditional laryngoscopy with a Macintosh blade.6 A recent study demonstrated beneficial effects of training with this video-assisted laryngoscope.7 However, most of these devices incorporate unique designs that differ from a standard laryngoscope (i.e., the glidescope®, the Bonfils®, or the CTrach®8) or require techniques much different from those of conventional intubation. In contrast, the C-MAC® videolaryngoscope incorporates a video system mounted into a traditional Macintosh blade.9 This tool provides both the laryngoscoper and an instructor a typical direct laryngoscopic view with a color image displayed on a nearby video screen. Because the video system is incorporated into a standard Macintosh blade, the psychomotor skills to perform endotracheal intubation are similar to those required when traditional equipment is used.

While videolaryngoscopes facilitate intubation in difficult airway scenarios in manikins10 and have been demonstrated to be useful for student teaching by video-assisted instruction,11 their use in teaching conventional intubation has not been well studied. The learning curve for using a combination of a conventional laryngoscope with a video system is short, and it has been speculated that such a tool might be advantageous for teaching.12 We hypothesized that medical students trained in endotracheal intubation achieve a higher intubation success rate and faster intubation times when training with a videolaryngoscope rather than a conventional laryngoscope.

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METHODS

Students Enrolled

All students (n = 93) enrolled in a course of emergency medicine for 1 semester, mainly provided by the anesthesiology department of our university, were included. Medical students were in their 2nd clinical year of education and had previously received theoretical lessons with regard to the practice of anesthesiology but had no previous experience with intubation. The students were informed about the study and the study was conducted with approval of the committee on teaching of the University of Essen Medical School and of the local institutional ethics review board.

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Study Design

On the 1st day of the course, an initial evaluation of intubation skills was performed on a standardized manikin (METI Emergency Care Simulator, Medical Education Technologies Inc., Sarasotoa, FL). The students were asked to intubate with a conventional Macintosh blade the trachea of the simulator's manikin, and the following measurements were taken by an instructor (trained anesthesiologist): successful endotracheal tube placement (yes/no), time from picking up the laryngoscope to passage of the endotracheal tube, and contact made to incisor teeth (yes/no). An endotracheal intubation was considered successful when the tube was placed into the trachea. Tracheal tube placement was confirmed in both manikin and patients by detection of expiratory carbon dioxide. Unilateral intubation of 1 mainstem bronchus was considered successful for the purpose of this study. The students were then asked to grade their ability to visualize the artificial larynx by using the Cormack and Lehane classification,13 which was provided to them on a pictogram. The students were permitted 1 intubation attempt during their evaluation on the manikin.

For the subsequent course the students were assigned by computer randomization to either a conventional group or a videolaryngoscope group. Each student was assigned to a resident (anesthesiology PGY 2 or 3) who served as the individual student's instructor during the course which for 2 weeks (10 work days) covered clinical routine, problem-oriented learning units of various emergency settings, and intubation attempts in anesthetized patients.

The instructors demonstrated proper intubation techniques using either a standard laryngoscope with a Macintosh blade or the videolaryngoscope according to the student's group assignment during the first 2 days, and the students were then given the opportunity to practice supervised endotracheal intubation in anesthetized adult patients for the remainder of the course using exclusively either the videolaryngoscope or a conventional Macintosh blade according to randomization. Students practiced airway management on adult patients without increased risk for aspiration of gastric contents (no history of gastroesophageal reflux disease, body mass index <30, elective surgery, sufficient preoperative fasting, no signs of ileus or gastrointestinal motility disorders). Anesthesia induction was performed with sodium thiopenthal (5 mg kg−1) and fentanyl (4 μg kg−1). All patients were paralyzed with rocuronium (0.5 mg kg−1), and mask ventilation was performed for at least 2 minutes after injection of rocuronium and before laryngoscopy was first attempted. Isoflurane was applied during mask ventilation with a target expiratory concentration of 1%. One intubation attempt per patient was permitted for safety reasons. In case of a failed attempt, the tutor took over. The intubation attempts performed by each student in patients during the training period were also counted. To correct for potential heterogeneity of individual instructors, all instructors alternated teaching for 2 weeks with the videolaryngoscope with teaching of the conventional method for the next student over the subsequent 2 weeks. Furthermore, after having been assigned to 1 arm (videolaryngoscope versus conventional) of the study, the students were allocated randomly to the instructors.

After the training period and upon conclusion of the course, the student's performance in endotracheal intubation was again evaluated using the standardized manikin model and a conventional Macintosh blade. An assessor blind to the randomization and students' group allocation scored the students' skills, as described above for the initial measurements.

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Statistical Analysis

Data are presented as means with 2-sided 95% confidence intervals for differences between groups unless otherwise specified. Standard deviations are presented with other data in Table 1. We tested 2 a priori null hypotheses in a hierarchical fashion:

  1. There is no difference in success rate in endotracheal intubation between students trained with a videolaryngoscope and those trained conventionally.
  2. There is no difference in intubation times between students trained with a videolaryngoscope and those trained conventionally.
Table 1

Table 1

The difference in success rate before and after training with each student having 1 intubation attempt on the manikin before and after the training period was compared using the McNemar test as well as the difference in success rates between groups after training. The time required by the students to successfully pass the endotracheal tube before and after training was analyzed using a 2-way repeated-measures analysis of variance (ANOVA) after the Mauchly test confirmed that sphericity can be assumed.

All other values of variables were analyzed with an exploratory intention only, i.e., contact to teeth, incidence of Cormack and Lehane scores 3 or 4, number of intubations attempted during the training period, or effects of training when compared with respective baselines. In an additional analysis, the number of intubations performed on anesthetized patients during the training period and the different instructors were included as covariates when the intubation times achieved in the after-training evaluation were compared.

Arbitrarily, sample size was calculated on the basis of an α error of 0.05 and a β error of 0.2 so as to detect a 20% difference in intubation success rate. Sample size calculation predicted a required enrollment of 73 students. Accordingly, enrollment of 1 complete semester of students (approximately 90 students) was considered adequate.

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RESULTS

Eighty-six students were available for evaluation after the 2-week course period (Fig. 1).

Figure 1

Figure 1

The intubation success rate of the manikin's trachea did not differ at baseline (44% videolaryngoscope group, 51% conventional group, P = 0.66) (Table 1). Students significantly improved their intubation skills after the course when compared with the respective baseline measurements (success rate after training: 90% in the videolaryngoscope group, 71% in the conventional group). The group trained on the videolaryngoscope achieved a 19% higher success rate after training when compared with the conventional group (95% confidence interval [CI] 1.1% to 35.3%, P < 0.001, Fig. 2, Table 1).

Figure 2

Figure 2

The time required for successful endotracheal intubation after the 2-week training period was a mean of 11 seconds shorter in the videolaryngoscope group than in the conventional group (95% CI for difference, 4–18, P = 0.003, Fig. 3). There was a marked 22-second improvement in the videolaryngoscope group when compared with the baseline evaluation (95% CI 14 to 30 seconds, P < 0.001, Fig. 3).

Figure 3

Figure 3

To account for potential confounders such as different tutors or differences in number of students' intubation attempts in anesthetized patients during the training period (Table 1), we included these factors as covariates in an additional analysis. The success rate after training was still significantly higher (P = 0.049) in the videolaryngoscope group. Likewise, the time required to successfully perform endotracheal intubation remained significantly shorter (P = 0.029) when the number of intubation attempts (i.e., the amount of practice) during the training period and the instructors were included as covariates.

The incidence of poor visualization of the larynx, expressed as a Cormack and Lehane score of 3 or 4, was less in the group trained with a videolaryngoscope (8% vs 34%, P = 0.005; Fig. 4). There was no significant difference between groups in the incidence of contact to teeth (40% in the videolaryngoscope group vs 48% in the conventional group) nor in the number of intubation attempts in anesthetized patients during the 2-week training period (Table 1).

Figure 4

Figure 4

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DISCUSSION

Our data show that training with the C-MAC videolaryngoscope improved endotracheal intubation skills in medical students when compared with conventional training, as demonstrated by an improved success rate for intubation and a shorter time required for successful intubation in a standardized manikin setting.

We cannot pinpoint what specific mechanism (or mechanisms) evoked improved learning when using the videolaryngoscope. It has been demonstrated in manikins that a C-MAC videolaryngoscope facilitates endotracheal intubation and leads to high success rates when used.14 However, all our students were assessed on a simulator both before and after their training and by using a conventional Macintosh blade mounted on a standard laryngoscope. Accordingly, although teaching with the C-MAC laryngoscope offered advantages such as easier demonstration of the correct technique by the instructor and better and more timely feedback to the student performing the intubation, using this tool for teaching resulted in better performance even when a standard Macintosh laryngoscope was subsequently used for intubation on a manikin.

This was a prospective randomized study, and differences in the students‘ performance at baseline before taking the course cannot account for the observed differences between groups. In fact, there was no significant difference in the baseline success rate between the 2 groups.

The success rate in intubation of the manikin's trachea after the training period was higher than was the overall success rate of intubation of anesthetized patients during the training period. Although this likely reflects the recent training, the difference might also have been due to the manikin's airway being easier than that of some patients or a more cautious approach by the students in intubating patients.

There could have been potential bias by our instructors or effects related to individual instructors. However, the instructors alternated teaching of the conventional and videolaryngoscope methods, and students in both groups were able to attempt a similar number of endotracheal intubations in anesthetized patients. When the instructors and the number of intubation attempts on patients were included as covariates in a multivariate analysis, the results still remained significant. We, therefore, believe that our results can be generalized. The reason for improved intubation skills after training with the videolaryngoscope may be attributable to the instructors' direct observation of the students' intubation attempts via the devices' video screens, which may have provided them with better and more timely feedback, thus possibly facilitating their acquisition of practical skills.15

It has been suggested that simulators16,17 or cadavers18 be used to teach endotracheal intubtation, or alternative approaches like the intubating laryngeal mask.19 In contrast to such approaches, a videolaryngoscope using a video camera mounted into a traditional Macintosh blade as used in this study permits the tutor to monitor, in real time, a student's performance and also to assess the placement of the endotracheal tube when endotracheal intubation is performed on a patient. Most likely, this approach allows for clinical training to be both more realistic and feasible.

Our data obtained in medical students may suggest that the C-MAC videolaryngoscope is beneficial for the training of other health care professionals also required to be skilled in endotracheal intubation, i.e., paramedics and even residents in anesthesia.

Although our study confirms the beneficial effects of training with a video-assisted laryngoscope published recently,7 the videolaryngoscope used in our study has the advantage of using a standard Macintosh blade. Thus, although the benefits of using a video device are retained, the psychomotor skills of conventional intubation can be practiced.

Our study has some limitations. The learning curve for endotracheal intubation has been examined, with a wide range of results. Although 1 study suggests a decent success rate with the 3rd attempt,20 another study demonstrates that 57 attempts are necessary to produce a 90% success rate, with 18% of the trainees still requiring assistance after 80 attempts.5 Although a 2-week training period is probably not sufficient to master the skill of endotracheal intubation, the training was long enough to demonstrate the advantage of the novel teaching technique. The success rate observed after training with the videolaryngoscope in our study is comparable to that observed after >50 intubation attempts in other studies.5 Thus, teaching endotracheal intubation with the videolaryngoscope might be a particularly effective way to teach airway skills.

Finally, the students graded their ability to visualize laryngeal structures using the Cormack and Lehane scale, as presented to them on a pictorial chart. Although there is some evidence that the reliability of this scale is limited,21 visibility of laryngeal structures was not the primary end point of this study, and we cannot determine a better way to have the students grade their visualization of anatomic landmarks during laryngoscopy.

In conclusion, the C-MAC videolaryngoscope is a valuable tool for teaching medical students the skill of endotracheal intubation. Teaching endotracheal intubation this way improves the success rate of endotracheal intubation and shortens the time required for this task. Further studies regarding the long-term benefits of this educational tool are warranted.

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REFERENCES

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15. Sachdeva AK. Use of effective feedback to facilitate adult learning. J Cancer Educ 1996;11:106–18
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DISCLOSURES

Name: Frank Herbstreit, DrMed.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Attestation: Frank Herbstreit has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files.

Name: Philipp Fassbender.

Contribution: This author helped design the study, conduct the study, and analyze the data.

Attestation: Philipp Fassbender has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Helge Haberl.

Contribution: This author helped design the study, conduct the study, and analyze the data.

Attestation: Helge Haberl has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Clemens Kehren, DrMed.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Attestation: Clemens Kehren has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Jürgen Peters, ProfDrMed.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Attestation: Jürgen Peters has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

© 2011 International Anesthesia Research Society