Objective: To compare the acceptability and preference between manikin models and fresh frozen cadaver (FFC) for direct laryngoscopic orotracheal intubation training.
Methods: In this prospective crossover trial, participants in the airway workshop performed direct laryngoscopic orotracheal intubation on four airway training manikins: Airway Management Trainer (Ambu, St Ives, UK), Airway Trainer (Laerdal, Medical, Stavanger, Norway), Airsim (Trucorp, Belfast, Northern Ireland) and “Bill 1” (VBM, Sulz, Germany), and FFC. Participants were asked to access the following: reality of jaw mobility, difficulty with mouth opening, reality of neck flexibility, difficulty with intubation, overall model reality and model preference for each model using a visual analogue scale (VAS) of 0–10 cm. The VAS scores for each model were compared.
Results: Fifty-six participants were included in the study. The FFC had a highest VAS score for reality of jaw mobility, overall reality and preference of model. Trucorp manikin and Laerdal manikin followed cadaver. There were no significant statistical differences between Trucorp manikin and Laerdal manikin. In difficulty with mouth opening and difficulty with intubation, Trucorp manikin had the lowest VAS score.
Conclusion: The FFC is a more realistic and preferred model for direct laryngoscopic orotracheal intubation training. Trucorp and Laerdal manikin can be used as alternative models.
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All doctors with acute care responsibilities are expected to be competent in airway management.1 For emergency doctors to perform accurate and rapid tracheal intubation in critical situation, appropriate education and training are required.2
Manikins have been used generally as a tool to teach invasive procedures to medical personnel and students. Currently, there are multiple manikin models suited for use in various training techniques, such as airway management and psychomotor skills, but the downside of manikin models is their fixed structural content and lack of realism. The use of cadavers for medical students and resident procedural training has been cited as an effective educational model for the past several years.3 4
To our knowledge, the fresh frozen cadaver (FFC) has not been evaluated as a tool for intubation training. Compared with the traditional cadaver, FFC may provide a better model for procedural skills training, as tissue planes are not distorted by the embalming process.5 We have evaluated and compared four currently available airway manikins with FFC to determine their adequacy and preference as simulators for intubation skill training.
This was a prospective crossover study that was undertaken in 56 participants on the emergency airway management courses hosted by the Korean Emergency Airway Management Society from April 2007 to September 2007. The courses included didactic lectures followed by skill stations using manikins and FFC. The various techniques were performed in skill stations. Instructions were provided by board-certified emergency doctors.
This study was approved by the institutional review board, and informed consent was obtained from each participant.
Direct laryngoscopic orotracheal intubation technique was instructed in the lecture component of the course. Participants performed orotracheal intubation on four airway manikins and FFC. The order in which the manikins were tested was randomised using computerisation. The four airway manikins used are shown in fig 1 and were as follows: (1) Airway Management Trainer (Ambu, St Ives, UK), (2) Airway Trainer (Laerdal Medical, Stavanger, Norway), (3) Airsim (Trucorp, Belfast, Northern Ireland) and (4) “Bill 1” (VBM, Sulz, Germany). These are referred to by their manufacturer (ie, Ambu, Laerdal, Trucorp and VBM). Recently deceased cadavers were obtained from the Catholic Institute for Applied Anatomy. The cadavers were not formalin fixed but were arterially flushed with an isopropyl alcohol solution to preserve natural tissue turgor and prevent degradation. The cadaver remained frozen and was fully thawed before the initiation of the course.
Orotracheal intubations were performed using the Macintosh no. 3 curved blade (Welch Allyn, Skaneateles Falls, New York, USA) and an endotracheal tube with an internal diameter of 8.0 mm. The maximum time allowed for an intubation attempt was 30 s, and single intubation attempt was allowed on each manikin and FFC. Correct placement of the tracheal tube was thereafter confirmed by an instructor.
After intubation, participants were immediately questioned on demographics, previous experience in airway training and actual experience. They were asked to score the following on visual analogue scale (VAS) of 0–10 cm: reality of jaw mobility, difficulty with mouth opening, reality of neck flexibility, difficulty with procedure, reality of model and preference of model. The participants were blinded of each other's scores.
The sample size was calculated according to the preference of model. A VAS difference of 1.3 was selected as the minimum clinically value.6 We used the pilot study performed by 15 participants from previous course as our reference. Using the VAS SD of 2.0 for preference of model, we calculated that a sample size of 50 participants was sufficient to detect an effect value at a significance level of 0.05 (two-sided) with 80% power.
Nominal variables were expressed as frequency and percentage. Continuous variables were expressed as mean and SD. The VAS scores for each model were compared with ANOVA. Tukey multiple comparisons test was used for post hoc analysis. Differences were considered significant where p<0.05. Statistical analysis was performed using SPSS V.13.0 for Windows.
The participants consisted of 43 (76.8%) doctors and 13 (23.2%) nurses. Of the 43 doctors, there were 11 board-certified emergency doctors (25.6%). Twenty (35.7%) participants had no airway management training experience, but the majority (24; 42.9%) had one to three experiences in airway management training. Thirty-eight participants (67.9%) had previous orotracheal intubation experience with actual patients.
VAS scores were highest in FFC for reality of jaw mobility. In difficulty with mouth opening, Trucorp manikin was preferred over the other three manikins, and no statistical significance was found compared with FFC. VAS scores were highest in FFC for reality of neck flexibility, but there was no statistical difference in the Laerdal, Trucorp manikin and FFC. Laerdal and Trucorp manikin were favoured over VBM manikin. In difficulty with procedure, Trucorp manikin was easier than any other model. In VAS scores of overall reality and preference of model, statistical analysis showed that FFC was preferred over manikins. Laerdal and Trucorp manikin were favoured over Ambu and VBM manikin (table 1). The results from the 38 participants with actual orotracheal intubation experience were similar (table 2).
The first intubation was successful on four manikins and FFC in ∼85.7%–100% (table 3). On VBM manikin, the success rate for the first attempt was significantly poorer.
In this study, we attempted to compare ease of use, acceptability and model preference for direct laryngoscopic orotracheal intubation training between four airway manikins and FFC. In the past, intubation training was performed directly on patients, but this raised ethical and safety issues, so animal or cadaver models were used instead. Nowadays, we have the privilege of training with various manikin models, such as simple task trainers and high-fidelity human simulators.7 8 Simple task trainers can provide psychomotor skill training, but they lack the reality of the procedure. While high-fidelity human simulators also provide psychomotor and cognitive skill training, they also lack the reality for psychomotor skills training. Animal models are realistic for training, but the anatomical differences defer us from using them as training models. In addition, there are animal rights issues to be taken into consideration.9 10
FFC is excellent model for psychomotor skill training. They maintain the texture and realism of live humans. Therefore, they are considered appropriate psychomotor training models.5 A previous study looking at the efficiency and realism for training of certain procedures (intravenous puncture, nasogastric tube insertion and lumbar puncture) reported a favourable outcome for cadaver model over manikin models.11 However, no study to date has compared model preference of FFC for intubation skill training.
Our study shows a favourable outcome for FFC over manikins in reality of jaw mobility, reality of neck flexibility and overall reality of model. When comparing the four manikins, Laerdal and Trucorp manikin were favoured over the other two models. Laerdal manikin received better scores for reality of jaw mobility, reality of neck flexibility, overall reality of model and preference of model, whereas Trucorp manikin received good scores for most of the measurements. These results are similar to a previous study by Jordan et al.12
Ambu and VBM manikin lack the elasticity of synthetic skin tissue. They also do not have a realistic laryngeal inlet anatomy. Trucorp manikin has a realistic laryngeal inlet anatomy but lacks the realism of some exterior structures including exterior neck anatomy, and the black plastic cover also gave it an unrealistic feeling.
This study has several limitations. First, although we used the most recent versions available for each manikin at the time of the study, they may have been modified further. Second, we evaluated only one of each manikin, and we cannot exclude the possibility of variations between individual manikins from the same manufacturer. Third, we have not performed any formal comparison of cost, portability or other features that may affect a choice. Fourth, one-third of candidate had no previous orotracheal intubation experience with actual patients. But, it is important to mention that the scores of the experienced participants were similar to those of the rest of participants, confirming that FFC has the advantage of more realistically simulating the actual experience. Fifth, there was limited hands-on time for participants. Only a single orotracheal intubation was performed on each model because of time constraints.
With this study, we can conclude that FFC can be more realistic and acceptable training tool for direct laryngoscopic orotracheal intubation. Trucorp and Laerdal manikin can be good alternatives when FFC is not readily available.
The authors gratefully acknowledge the members of the Korean Emergency Airway Management Society.
Competing interests Declared. The manikins used in this study were donated free of charge by Ambu Korea, Laerdal Korea, Trucorp Korea and VBM Korea.
Provenance and Peer review Not commissioned; externally peer reviewed.