Four different models for simulation-based training of bronchoscopic procedures

Thiel embedded cadavers and plastic manikins have shown to be suitable for simulation and training of bronchoscopic airway inspection [15, 16]. In this study, simulation of a bronchoscopic airway inspection could be performed in the BronchoBoy manikin, the Koken manikin, and the human cadaver. Both manikins represent typical bronchial anatomy, and the lack of anatomical variance is a known limitation of plastic manikins [8, 12]. The anatomy of the bronchial tree in the BronchoBoy manikin was considered ‘too easy’ to navigate by several participants. No negative comments were provided for the Koken manikin. It has been shown that despite limited fidelity in plastic manikins, they are useful for training in bronchoscopy [10], suggesting that at least the Koken manikin is useful for simulation of a bronchoscopic airway inspection. Human cadavers also have a realistic anatomy and a high fidelity, but anatomical variants can be seen and might confuse novice trainees [13]. Human cadavers have been used in training bronchoscopic procedures and were favored over manikin models for educational purposes [17, 18], which is in consistency with the findings of this study. Porcine lungs are promising models for hands-on training of bronchoscopic procedures and the histological structure of the respiratory tract is similar to humans [19‐21]. However, the difference in anatomy was commented on by multiple participants. Hence, the anatomical differences between the porcine and human lungs make these models inappropriate for learning human anatomy [20, 22].

Retrieval of fluid in a BAL procedure should be more than 30% of the instilled volume [23]. In this study, several participants failed to obtain this volume of retracted fluid in the human cadaver. This is thought to be caused by a leakage found in the lungs, resulting in a spread of fluid to the abdomen and a lower volume of retracted fluid. A single Thiel embedded cadaver can be used for several years [13]. However, aging has shown to result in changes to the soft tissue of Thiel embedded cadavers [24], which might explain the leakage in the nearly three years old cadaver used in this study. When simulating the BAL procedure in the BronchoBoy manikin, more participants failed to retrieve more than 30% of the instilled amount of fluid and leakage was observed in all test sessions. In a BAL procedure, the bronchoscope must be wedged into a bronchial segment, occluding the lumen of the bronchus [14, 23]. The bronchi of the BronchoBoy manikin are closed and the lumen was found to be too wide to fully wedge the bronchoscope, resulting in a spread of fluid to the bronchial tree. Consequently, the BronchoBoy manikin is not recommended for simulation of BAL procedures. No significant difference was found between the Koken manikin and the preserved porcine lung, suggesting both models can be used for training of BAL procedures.

Tissue sampling with a biopsy forceps is an important procedure in diagnostic bronchoscopy, e.g., in cancer diagnostics [25]. Accordingly, the ability to simulate tissue sampling is essential when choosing a simulation model for training of bronchoscopy. Porcine lungs have been evaluated as a supplement to teaching of bronchoscopic techniques, including tissue sampling procedures [21]. In this study, all bronchoscopists attempted the biopsy procedure in all for models. Tissue samplings were acquired from the preserved porcine lung and the human cadaver, whereas no tissue sampling was acquired from the BronchoBoy manikin and the Koken manikin. However, this was expected due to the hard, synthetic material of the plastic manikins [26, 27]. The lack of acquiring a tissue sample from the plastic manikins was commented on by several participants, stating that this made the models less preferred for simulation of a tissue sampling procedure. Further, it was commented that the plastic manikins felt “sticky” and the appearance was artificial. By using the Thiel embedding technique, the flexibility of the tissue is preserved, making it possible to retrieve a tissue sample. Further, the tissue colors are preserved [28, 29]. In this study, the appearance of the porcine lung was commented to be too pale, but the lack of perfused blood vessels was commented on in both the porcine lung and the human cadaver. No significant difference was found between the preserved porcine lung and the human cadaver, suggesting that the differences in anatomy between porcine and human lungs are not critical for simulation of tissue sampling procedures when retrieval of a tissue sampling is possible.

Factors such as costs and availability should be considered when choosing a simulation model for bronchoscopic procedures. The price of a human cadaver is 1000 USD per use day [30]. However, a facility capable of following the regulatory requirements for cadaver studies is necessary and ethical concerns must also be considered [13, 24]. The plastic manikins can be reused over several years which makes the costs of the Koken manikin (3734 USD) and the BronchoBoy (7181 USD) reasonable one-time costs [31, 32]. Live anesthetized animals are widely used for training new doctors and could also be considered for realistic bronchoscopy training. However, there are ethical concerns when working with live animals, and the “Three Rs”: Replacement, Reduction, and Refinement should be acknowledged. Whenever possible, an alternative to animals should be used, and the minimum number of animals necessary should be used for training. Further, training should be modified in such way that any distress and pain exposed to the animal is minimized [33, 34]. These ethical concerns are overcome when using preserved porcine lungs, as the lungs are waste products from food production and can be reused for multiple procedures if stored correctly [35]. The price of a preserved porcine lung is 251 USD [36].

This is the first study to compare plastic manikins with a human cadaver and a preserved porcine lung for simulation of bronchoscopic procedures. All participants were experienced physicians, and they all evaluated all four bronchoscopy models in a fully crossed design. However, the sample size was relatively small, and it would be interesting to test the models using more bronchoscopists with different levels of experience.

It has been shown that learning benefits for novices rank higher than for more experienced physicians [37]. All participants in this study were physicians with many years of experience with real patients which might make their evaluation of physical models more critical compared to novices.

The Thiel embedded cadaver used in this study had been embedded for almost three years, which might have caused some damage to the soft tissue. This might have been avoided using a more fresh cadaver, as aging has shown to result in changes to the soft tissue of Thiel embedded cadavers [24]. In spite of this, by using a Thiel embedded cadaver, a low formaldehyde concentration is used, the lungs can be ventilated, and the flexibility of the tissue is preserved [29].

This study was completed using Ambu aScope 4 Broncho only. The findings of this study may be different with other single-use bronchoscopes or with reusable bronchoscopes.

Virtual reality simulators can simulate various bronchoscopy procedures and pathologies. However, the practical experience with different procedures, such as instillation of fluids and retrieval of tissue samplings, is missing. Live anesthetized porcines are often used to simulate human physiology in the evaluation of drug performance and surgical procedures [38, 39]. In this study, the preserved porcine lung was shown to be realistic for simulation of BAL procedures and tissue sampling. However, live porcines are necessary if the specific training needs include physiological reactions like ventilation, movement, and bleeding [40].

The included models were found to be useful for training purposes by experienced physicians, therefore the findings in this study can give an indication of which model would benefit the learning of novices in more clinical aspects. As an example, basic bronchoscopic navigation could be practiced in an anatomically correct plastic model whereas biopsy procedures would optimally require a porcine lung model or even a human cadaver. Optimally, randomized trials with solid outcome measures (e.g., generated by artificial intelligence) should be conducted to test the efficacy of the simulation-based training programs [41].