Products: The Simulator and its accessories
Figure 3 shows our simulator. The simulator weighs about one kilogram and looks like a small suitcase on the outside. When closed, the simulator measures 21 cm in length, 13 cm in width, and 13 cm in height (Figure 3A). While open, two structures are designed for knot-tying at the surface or depth (Figure 3B). The mock vessel is a small and compressible silicon tube. Its outer and inner diameters are 2.0 mm and 1.1 mm, respectively. The built-in electric air compressor can abruptly pressurize the mock vessel, and the intra-conduit pressure is measured by a built-in pressure gauge connected to the upstream of the mock vessel (Figures 1B and 3B). The transient pressure driven by the air compressor is about 160 mmHg. If the ligation knot fails to occlude the vessel completely, the indicator of the pressure gauge returns to zero quickly due to a continuous leak of intra-conduit air from the open end to the air. The simulator requires four triple-A batteries to maintain the operation of the built-in electric air compressor. When recording vessel ligation with a smartphone, the entire mock vessel should be visible on the screen, aligned with the zero line on the chart ruler at rest for accurate displacement measurement (Figure 3C). The scale of the chart ruler was 0.5 cm per mark. The vertical displacement had been translated into the corresponding force by vertically pulling the mock vessel at the middle point (the knotting site) with a hand-held tensiometer to a given mark on the chart ruler (Figure 3D). The displacement-force translation measurement was done ten times for each mark to obtain the mean values of force applied to each mark (Figure 3D). The cost of the simulator was about 250 USD. Table 1 shows the OSATS checklist. In the first four tasks to tie superficially, trainees received formative evaluation and feedback from the proctors. In the last two tasks to tie in depth, trainees received summative evaluation and feedback from the proctor and the novel simulator. In the end, their achievements in the final two assignments determined whether they passed or failed this training course. The links of the e-learning platform and the introduction video of our simulator are (https://reurl.cc/nDEd78) and (https://www.youtube.com/watch?v=TZRfnALNGdo), respectively.
Experts’ evaluation
The Appendix Table 1 shows the demographic data of the six experts. They were three general surgeons, two cardiac surgeons, and one chest surgeon. The average seniority as an attending surgeon in them exceeded 20 years. Table 2A shows the experts’ scores on the face and content validity of the novel simulator as an appropriate teaching instrument. The mean scores for all evaluated items on face and content validity were 4.5 and 4.77, respectively. Compared to other items, the items related to the appropriateness of the texture of the mock vessel and the post-ligation pressure test got lower mean scores and showed larger standard deviations. These arguments were primarily due to the textural discrepancy between the silicon tube and the biological blood vessel. An expert stated,
The mock vessel seems sturdy and is unbroken by excessive traction. This feature may lead the user to focus on tightening the knot to pass the pressure test rather than respecting the tissue. Therefore, according to this learning experience, they might overestimate the force required to ligate a real vessel of equivalent size and break the vessel in the operating room. Therefore, I recommend replacing the current texture of the mock vessel with a more fragile material that can be torn. (E4, Chest Surgeon, Attending Seniority: 20 years, a clinician educator.)
Other experts showed a positive attitude toward the post-ligation pressure test but also suggested testing trainees with vessels of variable fragility to increase the realism and discrimination power of the simulation.
Novice Participants’ performance
The Appendix Table 2 shows the demographic data of the thirty novice participants. Most participants (N = 23; 77%) attended one or more training class focusing on instrument ties prior to this training course, but only 7% (N = 2) of them had practiced the skill more than five times within 12 months of the training course. The median score on their self-confidence scale for mastering common surgical knot-tying techniques was 4 (2–6) before joining the class. Table 3A shows the comparisons in skill performance recorded by the OSATS checklist between the expert group and the novice group. According to Table 3, experts performed significantly better than novices only in the task completion time. The median of the trainees’ self-confidence scale increased to 8 (6–8) after attending the pilot curriculum, which was significantly higher than the pre-class value (p < 0.001).
Novice participants’ perceptions of the simulator
All of the thirty novice participants answered “yes” to the question, ‘Do you think this novel simulator is helpful to your learning in this training course on surgical knot-tying techniques?’ Table 2B shows the word cloud of the main themes extracted from the students’ descriptions regarding the helpfulness of the simulator in their skill learning. It shows that “hands-on practice” and “feels real” were the two most common phrases appearing in their comments. They appreciated this novel simulator for providing them with a high-fidelity (real) environment in which to learn the hands-on skill. A student wrote
“I had watched the instruction video before and found that I did not fully understand how to move my hands to tie knots as shown in the video. Learning surgical knot-tying in this simulator brought me spatial perception and tactile feedback that benefited my mastery of the skill.” (S15, female, 24 years old.)
The direct objective outcome assessments provided by the simulator may also contribute to their sense of realism in this simulation training. Another student wrote
“Practicing on this simulator allows me to become familiar with tying knots in a limited space. The force measurement also helps me understand how to use my hands to tie knots and tighten them properly. The final pressure test tells me instantly if my knot has successfully occluded the vessel. This test allows me to quickly identify problems in my skills and seek improvements. (S20, male, 25 years old.)