Emergency front-of-neck access is the life-saving rescue procedure in ‘cannot intubate cannot oxygenate’ situations.1 Unfortunately, emergency front-of-neck access is associated with high first-attempt failure rates of 30 to 50%;1 therefore, regular training is crucial and needed.2 The scalpel-bougie-tube cricothyroidotomy is recommended.3 Human/animal cadavers, anaesthetised animals and manikins have been used to train cricothyroidotomy. However, as well as the technical procedures, full-scale simulation trains the equally important human factors (communication, leadership, situational awareness and team/task management).4 Hybrid simulation, using a cricothyroidotomy trainer and a trained simulated patient, trains the technical skills and human factors as realistically as possible.
We developed and pilot-tested a hybrid full-scale simulation using a novel cricothyroidotomy trainer: an inexpensive, three-dimensional (3D) printed model of the larynx was placed on the anterior neck of a simulated patient to enhance realism.5 The authors are pleased to share the data file to print the 3D-airway model free of charge. The file is accessible at the website of the European Airway Management Society (EAMS) www.eamshq.net. This project was exempt from ethics committee approval as it did not fall under the Swiss Human Research Act and was undertaken from May to September 2019.
Various components were added to the original Duggan's open-access 3D cricothyroidotomy model6 (Fig. 1) so that punctures between the hyoid bone and the thyroid cartilage and between the cartilage rings of the trachea are possible. At the tracheal end, we added a standard tube connector. Adhesive tape simulated the laryngeal membranes/ligaments.
To demonstrate the feasibility of the set-up, the cricothyroidotomy trainer was initially fitted on a manikin. Later, we placed it on the anterior neck of a simulated patient. First, a flexible neck protector (CRL-Nacken-Schnittschutz-Laurence, Ilsfeld, Germany) was placed around the neck as cut protection and then stab protection was added using commercially available aluminium sheeting (0.5 mm thick) cut to size. Over that, the 3D cricothyroidotomy trainer was fixed in place with adhesive tape and finally, a strip of fresh pig skin was placed to cover everything (Supplementary Video, https://links.lww.com/EJA/A526). Different thicknesses of pig skin increase the challenge for participants by representing various anatomical conditions (e.g. obesity). An intravenous cannula connected to flexible tubing was hidden under the pig skin and, when an incision into the pig skin took place; artificial blood was injected to mimic bleeding (Fig. 2). The tracheal end of the cricothyroidotomy trainer was connected to an artificial lung (SilkoBag-Rüsch, Athlone, Ireland) and placed under the volunteer's shirt. Successful cricothyroidotomy allowed confirmation of ventilation by visible ‘thoracic’ movements. For the pilot-test we used commercially available cricothyroidotomy sets (scalpel, bougie, cuffed tube – ScalpelCricset-VBM, Sulz, Germany).
The simulated patient was positioned supine with the neck extended without a pillow on an operating table. Standard noninvasive monitoring was simulated (ALSi-iSumuate, Fyshwick, Australia) allowing realistic deterioration of vital signs and monitor alarms. The simulated patient acted out a scenario as if experiencing a severe allergic reaction that had led to swelling of the upper airways and life-threatening respiratory distress (Supplemental material, scenario, https://links.lww.com/EJA/A525); additional instructions for the simulation were relayed to the simulated patient via an intra-aural earphone.
Three airway teams (a consultant, resident and nurse) pilot-tested this hybrid-simulation. Before the simulation, the teams were informed that a patient with a life-threatening respiratory condition was expected via ambulance and that airway manoeuvres had been unsuccessful due to swelling of the upper airway.
Paramedics handed over the tachypnoeic but stable simulated patient with the suspected allergic reaction and severe respiratory distress. Vital signs deteriorated rapidly (low oxygen saturation, tachypnoea, tachycardia and hypertension). The simulated patient acted agitated at being unable to breathe adequately.
The aim was to force the airway team to perform a cricothyroidotomy. If the team was reluctant, then the simulated patient collapsed (no movement, extremely low oxygen saturation, superficial respiration attempts, extreme tachycardia and hypotension). If there was further delay, then a simulation instructor entered the room acting as supervising physician and instructed the team to perform an immediate cricothyroidotomy. After successful tube placement and ventilation of the simulated lung, the simulated patient slowly recovered, which ended the simulation scenario. Simulation instructors then performed video-assisted debriefing and participants were asked for open feedback on the hybrid simulation and the cricothyroidotomy trainer.
Our 3D printed model is an inexpensive, stable, resistant and easily reproducible cricothyroidotomy trainer with a haptic and texture very close to reality. The possibility of challenging trainees by adding additional layers to modify the thickness of the pig skin (to simulate the neck of an obese patient) renders it particularly attractive.
After gathering the equipment together, the set-up of the cricothyroidotomy trainer and pig skin on the simulated patient was easy and fast, achievable within less than 8 min. However, procurement of the necessary materials was time-consuming and not-for-food refrigerated space for the pig skin is required.
All participants confirmed the realistic haptic of this hybrid simulation set-up and its suitability for cricothyroidotomy training. The technical skill performance of cricothyroidotomy in that setting was rated as relatively easy. The artificial blood added realism and enhanced the sense of urgency, but did not add difficulty. Some participants were initially confused by the slightly unnatural thickness of the simulated patient's neck, but this did not lead to any performance problems. The possibility of verifying the correct tube position by achieving realistic ‘thoracic movement’ with ventilation was a stress-relieving moment for all participants. Compared with the usual cricothyroidotomy training manikins, all participants confirmed that this hybrid simulation setup adds fidelity and is far more realistic. Thus, the participants confirmed the face validity of the hybrid simulation set-up with our 3D printed cricothyroidotomy trainer.
Participants valued the integration of a simulated patient into the training scenario, and the realistic training of communication, leadership and decision-making was seen as a major benefit over conventional manikin simulation set-ups. The simulated patient was able to provide feedback on how it felt to experience an airway emergency, and this was welcomed and well received by all participants. The cut and stab protection layers were comfortable and protective for the simulated patient and, in addition, it minimised skin contact with the pig skin. The simulated patient felt completely safe and comfortable.
A major limitation is that with our set-up it is only possible to practice the cricothyroidotomy: other airway management manoeuvres are not feasible. We cannot provide data on the educational and patient outcomes of the hybrid simulation.
In conclusion, this highly realistic, low-cost hybrid simulation offers the possibility of practising the life-saving skill of emergency cricothyroidotomy in a close-to-reality simulation. This helps the airway team to recognise the need to act and to perform a cricothyroidotomy early and with greater confidence, thereby potentially preventing devastating complications.7
Acknowledgements relating to this article
Assistance with the letter: the authors wish to thank the personnel of the Bern Simulation and CPR-Centre (BeSiC) of the Bern University Hospital, Bern, Switzerland for their collaboration and input in the realisation of this project. Donald W Corson generously performed the 3D airway model adaptations and printing. The authors would also like to thank Yves Balmer and Thilo Schweizer for their contribution to the successful pilot-test of this hybrid simulation. Additionally, the authors would also like to thank Christopher Berrie for critical review of the English in this manuscript.
Financial support and sponsorship: the Department of Anaesthesiology and Pain Medicine, Bern University Hospital, Bern, Switzerland granted a departmental research grant to Prof R Greif. No other external funding was obtained.
Conflicts of interest: RG is the current immediate past president of the European Airway Management Society. SN is committee member of the TEAMS committee (trainees of the European Airway Management Society). All other authors declare that they have no competing interests.
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