Introduction

Medical simulation is a field where engineers create tools for physicians, students, and healthcare professionals to train and practice procedures in order to improve patient safety and satisfaction in a controlled environment. These simulations can include a combination of mannequins, robots, or paid actors, as well as fake blood, tissue, organs, and bones. Through our discussions with our preceptor, Dr. Jennifer Snow, we were led to focus on a simulation for a specific procedure called a cricothyrotomy. A cricothyrotomy (abbreviated as cric) is an emergency airway procedure, where the physician makes a small incision in the patient’s throat, through the skin and the cricothyroid membrane (CTM), and inserts a tube to allow the patient to breath during life threatening situations such as airway obstruction (Figure 1). While cric procedures are life-saving, they are not very often performed by physicians. Therefore, a lifelike cric simulation trainer is needed for practice to keep physicians, students, and healthcare professionals familiar and comfortable with the procedure. 

Dr. Snow introduced us to another one of our mentors, Dr. James Kearney, who is the Chairman and professor of Otorhinolaryngology & Head and Neck Surgery at Pennsylvania Hospital and the medical director of the Penn Rittenhouse Ambulatory Surgery Center. Through his extended knowledge of cric procedures and teaching using simulation, Dr. Kearney guided us in the details of cricothyrotomy procedures and specified what factors were important for his use of cric trainers. With Dr. Kearney's guidance, we decided on three main goals for our cric trainer. We wanted to make our trainer more lifelike, less expensive, and more diverse than current cric trainers. To do this, we focused on four main areas of research for our trainer: design, material, fat simulation, and patient simulation.

Analysis

For our design, we researched current open source 3D printed cric trainers and found that there were two main types: solid base and curved base (Figure 2). We decided to print one of each to determine variables such as print time and print difficulty that would help us to determine which design type would be best for our trainer (Figure 3). Dr. Snow also helped us to utilize a tool called Quality Function Deployment (QFD) to compare the different options for our design, as well as the other main areas of our trainer. For the concept of design, we took into consideration three different attributes: print time, print difficulty, and shape accuracy (Figure 4). We weighted the importance of each of these (either 1 for not important, 3 for moderately important, or 9 for most important) based on feedback from Dr. Kearney. We decided that shape accuracy was the most important, in order to align with one of our initial three goals to make the trainer more lifelike. Next, we ranked each of these three attributes across our two design options and determined that curved base design would be best for our trainer because the shape accuracy was much higher than that of the solid base design.

Next, we researched material. Our options were to 3D print with thermoplastic elastomer (TPE) or nylon, or to create a mold to make our trainer. We used the same table process as our design, this time with 6 different attributes: upfront cost, later cost, prep time, time to make, printing difficulty, and printing accuracy (Figure 5). We weighted prep time and printing difficulty as the most important (9), followed by upfront cost, later cost, and printing accuracy, all weighted as moderately important (3). These last three align with two of our initial three goals: more lifelike and less expensive. Ranking these 6 attributes across the three material options we had a very close call between 3D printing with TPE (relative rating  = 20) and creating a mold (relative rating = 23). Therefore, we determined that more research would be needed to determine a winner between the two materials.

We decided that fat simulation was one of the areas we wanted to focus on in an effort to address our third main goal of creating a more diverse trainer. Dr. Kearney advised us that most of the emergency cric procedures that physicians perform are on an overweight population, where fat prevents the physician from feeling the cartilage landmarks of the trachea. However, no current cric trainers have any fat simulation for these physicians to practice on. Therefore, we repeated the same process as above to determine which fat simulation would be best for our trainer (Figure 6). Here, our research pointed to three possibilities: thermoplastic, rubber, or commercialized fake fat. The attributes we considered here were accuracy, cost, weight, and thickness. We weighted both accuracy and cost as most important (9), as we wanted to, again, stay true to our original goals. We then weighted weight and thickness as moderately important (3). The relative ratings resulted in a close call between the commercialized fake fat and the thermoplastic. Again, this tells us that we would need to perform more research in order to make a final decision between these two options.

Finally, we discussed the option of simulating with or without an actor. Initially, we were under the impression that without an actor would be more desirable due to safety considerations. However, under Dr. Kearney’s guidance we discovered that the position of the patients’ head and neck are very important in a cric procedure. With this new knowledge, we realized that the lifelike nature of using an actor was very important. Therefore, in our table we weighted lifelikeness as most important (9) and danger and cost as moderately important (3) (Figure 7). From this tool, we were able to determine that simulating with an actor was the best option.

Conclusions

In conclusion, our final design plan would consist of an actor with a kevlar neck cover, a curved base trainer design that is either 3D printed with TPE or constructed via mold (more research needed), overlaid with a commercialized fake fat or thermoplastic (more research needed), and a suture kit skin cover on top (Figure 8). While we were able to 3D print two cric trainers, we were not able to actually implement any of our other design choices due to the time restraint of the class. However, we hope that our extensive research and decisions about what we would have liked to pursue for our final design show that we put adequate time and effort into this project. If we were to pursue this project in the future, our first action would be to research more into how difficult it would be to create a mold for creating cric trainers. Some questions we would need to answer would be: what material would the mold be made out of? What material would the cric trainers be made of? How long exactly is the prep time of creating a mold and how does it compare to the time it takes to 3D print multiple cric trainers in TPE? We would also need to research more into thermoplastic versus commercialized fake fat for our fat simulation. To do this, we would likely pursue stakeholder feedback such as Dr. Kearney and other physicians and professors.

References

1. Sakles, J. C., Wolfson, A. B., & Ganetsky, M. (2021, March 22). Emergency cricothyrotomy (cricothyroidotomy). UpToDate. Retrieved from https://www.uptodate.com/contents/emergency-cricothyrotomy-cricothyroidotomy  

2. Published by joinsims (2019, March 2). 3D printed cricothyrotomy trainer. SIMS Solutions. Retrieved from https://joinsims.wordpress.com/2018/02/12/3d-printed-cricothyrotomy-trainer/   

3. 3D Cric Trainer. The Airway App. (n.d.). Retrieved from http://www.airwaycollaboration.org/3d-cric-trainer-1    

4. Health, A. D. A. M. (2019, November 4). Emergency airway puncture. Healthing: Inspiring Canadians to Live Better. Retrieved from https://www.healthing.ca/surgery/emergency-airway-puncture