Simulation is the obvious answer, but commercial cricothyroidotomy simulators cost hundreds of dollars, putting them out of reach for many of the settings where trauma training is needed most. Traumatic injury requiring surgical intervention accounted for 19.1 percent of the global burden of disease in 2021, with low- and middle-income countries disproportionately affected. Existing low-cost alternatives have their own drawbacks: 3D-printed models depend on printing technology that is not reliably available in resource-poor environments, pig tracheas require special handling and storage and can be used only once, and other homemade designs rely on epoxy or silicone resin that may not be easy to source. A team led by Lukas Shum-Tim, with collaborators spanning medical students, surgical residents, surgeons, nurses and biomedical engineers from five institutions, set out to break that trade-off between cost and accessibility.

Their solution is disarmingly simple. The simulator is built from an egg carton, a 500 mL water bottle, a nitrile glove and homemade slime made from laundry detergent, glue, corn starch and sodium bicarbonate. To the authors’ knowledge, no other simulator in the literature has used slime as a cheap, infinitely reusable material that mimics soft tissue. The total materials cost is about 0.53 USD per unit, dropping further if materials are recycled, and assembly from scratch takes less than five minutes, with a per-use cost of roughly 0.05 USD, lower than most previously described low-cost simulators. The full design and manufacturing process was described in a separate publication, and the team deliberately chose materials that are accessible essentially anywhere in the world.

A cheap trainer is only useful if it can actually measure skill, so the team set out to generate validity evidence for using the simulator in formative assessment. They anchored the study in Messick’s unified validity framework, the approach recommended by the American Educational Research Association and the American Psychological Association, gathering evidence across five sources: content, response process, internal structure, relations to other variables, and consequences. The study was conducted at McMaster University between December 2024 and April 2025, with the British Columbia Children and Women’s Research Ethics Board deeming it quality improvement and waiving full ethics review.

Twenty-six participants were recruited through convenience sampling: 19 novices, mostly surgical residents, and seven experts, defined as physicians with at least five years of postgraduate clinical experience in trauma or head and neck surgery. None had seen the simulator before. Each participant completed a pre-test survey, performed a cricothyroidotomy on the model while a camera recorded their hand movements, and then filled out a 43-item post-test questionnaire covering anatomy, realism, instrument handling and confidence. Guidance was given only after the performance, never during it, so that the recorded attempts reflected unaided skill.

Two trauma surgeons independently scored the anonymized videos using two standardized instruments. The procedure-specific checklist contained nine items corresponding to critical steps of a Rapid Four-Step Cricothyroidotomy, adapted from a validated bougie-assisted checklist so that the assessment would work even in settings where bougies are unavailable; each step earned five points if achieved, three if in progress, and one if not observed. The error checklist contained seven items drawn from a multicenter expert collaboration on mistakes to avoid, with one point awarded for each error avoided. The raw score, ranging from nine to 52, was then divided by procedure time in seconds, a deliberate design choice reflecting the clinical reality that airway compromise must be resolved quickly and that errors or delays can cause irreversible harm.

The results showed the simulator does what a training tool should: it separates the skilled from the unskilled. Experts completed significantly more procedural steps than novices (Mann-Whitney U z = -2.52, p = 0.012), committed fewer errors (z = -3.07, p = 0.002), achieved better raw scores (z = -2.69, p = 0.007) and better final timed scores (z = -3.21, p = 0.001), and finished faster (z = -2.86, p = 0.004). In other words, experts were more accurate, made fewer mistakes and worked quicker, exactly the pattern expected if the simulator captures the essential elements of the real procedure. Internal consistency was excellent across the board, with Cronbach’s alpha of 0.86 for the procedure checklist, 0.85 for the error checklist, 0.84 for novice questionnaire responses and 0.97 for expert responses, all more than adequate for low-stakes formative assessment.

The study was candid about its weaknesses. Interrater reliability was only moderate for the procedure checklist, with an intraclass correlation of 0.54, and poor for the error checklist at 0.36, likely because composite scores are harder to agree on than binary ones and because the raters received no formal rating standardization. The authors calculated, using the Spearman-Brown formula, that about four raters would be needed to reach a targeted reliability of 0.5 on the error checklist, a burden they argued is hard to justify for a formative tool. Defining expertise also proved tricky, since multiple specialties perform the procedure with slightly different techniques, and one checklist item, a vertical skin incision, cost experts points even though a horizontal incision would be clinically valid in some contexts. Notably, no expert achieved a perfect score, which the authors read as a sign the simulator is better suited to assessing and teaching novices than to certifying experts.

Confidence data added a cautionary nuance. Novice pre-test confidence, averaging 1.68 on a five-point scale, rose to 3.80 after the exercise, while expert confidence dipped slightly from 3.78 to 3.00. One expert warned that a low-fidelity model risks underrepresenting the skillset required and could foster false confidence, a reminder that training on a single unidimensional model may not build the adaptive expertise needed to handle varied patient presentations. The authors counter that their conclusions align with studies using high-fidelity models, consistent with a growing literature showing that low-fidelity simulation training for procedural skills is not inferior to high-fidelity training, and that simulation of any kind beats no intervention at all.

The bigger picture is one of democratized surgical education. By slashing the cost of a cricothyroidotomy trainer to half a dollar and designing it from materials found in any household, the team has removed the procurement barrier that keeps simulation out of hospitals, training programs and medical schools in low-resource settings, where trauma burdens are highest and learning alternatives are scarcest. The findings provide preliminary validity evidence that checklist-based assessment of simulated cricothyroidotomy performance works on this humble device, and the authors are explicit that further research is needed to determine its educational effectiveness. But the concept has an appeal that goes beyond one procedure: if a slime-and-egg-carton model can reliably distinguish expert from novice performance on a life-saving emergency airway maneuver, the same design philosophy, frugal, reproducible and globally accessible, could be applied to a whole family of high-acuity, low-occurrence skills that clinicians everywhere struggle to practice before the moment they matter most.

Subject of Research: Validation of a low-cost, low-fidelity cricothyroidotomy training simulator for surgical education

Article Title: Evaluation and performance assessment on a low-cost, low-fidelity cricothyroidotomy simulator

Article References: Shum-Tim, L., Desaigoudar, V., Mashat, A., Hsiao, H., Malik, P. R. A., Malone, K. R., Abdalla, M. H., Rajagopalan, S., Mourad, N., Bos, C., Joos, E., & Joharifard, S. (2026). Evaluation and performance assessment on a low-cost, low-fidelity cricothyroidotomy simulator. Global Surgical Education – Journal of the Association for Surgical Education, 5(1), Article 138. https://doi.org/10.1007/s44186-026-00545-z

Image Credits: AI Generated

DOI: 10.1007/s44186-026-00545-z

Keywords: cricothyroidotomy, surgical simulation, medical education, global surgery, validity evidence, low-cost simulator, emergency airway, trauma training, Messick framework, checklist assessment, low-resource settings, surgical skills

The research, published in Global Surgical Education, the journal of the Association for Surgical Education, set out to gather what psychometricians call validity evidence for a low-cost inanimate simulator designed for subclavian central venous catheterization training. Rather than simply asking whether trainees liked the model, the authors, Luz Galvis-Arenas and Omaira Rodríguez of the Department of Surgery in Caracas, structured their investigation around Messick’s framework, the modern conceptual foundation of educational measurement. Under this framework, validity is not a property of a test or a simulator itself but of the interpretations and actions built on its scores. A simulator earns its place in a curriculum only if its scores actually mean what educators claim they mean, such as the claim that a high checklist score reflects genuine procedural competence.

To test that claim, the team ran a cross-sectional validation study with twenty participants divided into two starkly different groups. Ten were sixth-year medical students with no prior experience in central venous catheterization, forming the novice cohort, and ten were experienced general surgeons who constituted the expert group. The logic behind this design, known as the known-groups approach, is straightforward and powerful: if the simulator and its scoring system are truly measuring procedural skill, then experts should systematically outperform novices. A model on which beginners score as well as veterans would be blind to the very skill it is supposed to capture, no matter how realistic it looks or feels.

The study examined three strands of evidence. First, content validity was assessed by surveying experts about whether the model adequately represents the essential elements of subclavian catheter placement, quantified through the Content Validity Index, a metric that reflects the proportion of raters agreeing that each element is relevant. Second, technical performance was scored with a thirteen-item procedural checklist, completed independently by two evaluators who watched each attempt, allowing the researchers to calculate interrater reliability using the kappa statistic. Third, construct validity was examined through the comparison of experts and novices across a battery of outcomes, including checklist scores, procedure duration, first-attempt success, the proportion of participants completing the procedure without assistance, and the occurrence of simulated complications.

The content validity results were as strong as this type of evidence can be. Every item on the expert survey achieved an item-level Content Validity Index of 1.00, and the scale-level average matched that perfect figure, indicating unanimous agreement among the consulted experts that the model covers the essential steps of the procedure. Interrater reliability was equally remarkable: the two independent evaluators assigned identical checklist scores to every performance, yielding a kappa of 1.00. Perfect agreement between raters is an ideal outcome for any scoring instrument, because it means the checklist items are described with enough clarity that subjective interpretation plays essentially no role in the grade a trainee receives.

One statistical nuance deserves attention. The internal consistency of the checklist, measured with the KR-20 coefficient, came in at a moderate 0.63, and the authors noted ceiling effects in several fundamental steps. In plain terms, most participants, including many novices, completed the basic items correctly, so those items could not strongly differentiate performance levels. This is a common and partly unavoidable feature of procedural checklists, since fundamental steps such as hand preparation and equipment assembly are quickly mastered by most trainees. A moderate internal consistency coefficient is not a fatal flaw, but it signals that the checklist may be most informative about overall procedural conduct rather than fine-grained differences in technical finesse, and it suggests room for refinement of the instrument in future versions.

The construct validity results were decisive. Experts achieved a mean checklist score of 100.0 percent, compared with 85.4 plus or minus 10.5 for the novices, a difference that reached statistical significance with a p value of 0.002. Experts were also dramatically faster, completing the procedure in an average of 5.28 plus or minus 0.79 minutes against 11.61 plus or minus 4.67 minutes for the students, again with p equal to 0.002. First-attempt success rates told the same story: 70 percent of experts succeeded on their initial attempt, while only 10 percent of novices did so, a difference with a p value of 0.020. Autonomy diverged even more sharply, with every expert completing the placement independently compared with just 10 percent of the students, a result significant at p equal to 0.0003.

Complication data added a clinical dimension to the statistical picture. No complications occurred among any of the expert attempts, whereas the novice group generated simulated complications in 30 percent of their attempts. Although these were simulated events on an inanimate model, the pattern mirrors real-world epidemiology, where mechanical complications of central venous catheterization, including arterial puncture and pneumothorax, are concentrated among less experienced operators. The fact that the simulator reproduces this gradient of adverse events suggests it captures not only the choreography of the procedure but also the consequences of technical error, which is precisely what makes it valuable as a rehearsal space before students face actual patients.

The implications extend well beyond one medical school in Caracas. Central venous catheterization is among the most commonly performed invasive procedures in hospitals worldwide, and meta-analyses of simulation-based education have linked structured simulator training to fewer catheter-related complications in clinical practice. Studies using simulation-based mastery learning have shown measurable reductions in intensive care unit catheter complications, and multicentre audits have documented the ongoing toll of mechanical injuries even in the ultrasound-guided era. Against that backdrop, the appeal of a low-cost, non-living model is obvious. Commercial high-fidelity mannequins can be prohibitively expensive for institutions in low- and middle-income countries, where the burden of preventable procedural harm is often greatest. Simple, affordable simulators such as gelatin phantoms and assembled low-cost models have been explored by several groups, and this study adds rigorous validity evidence to that movement, showing that cost-cutting need not come at the price of measurement quality.

The Venezuelan study also carries a methodological lesson for the broader field of surgical education. A systematic review of validity evidence in surgical simulation has documented how inconsistently simulators are evaluated, with many devices adopted on plausibility alone. By grounding the evaluation in Messick’s framework, quantifying content validity, verifying interrater reliability, and applying a known-groups design, the authors modeled the kind of disciplined assessment that should precede any simulator’s integration into a training curriculum. The study was approved by the Bioethics Committee of the Instituto Autónomo Hospital Universitario de Caracas, and all participants gave written informed consent. The authors declared no competing interests and received no specific external funding. As health systems worldwide continue to shift invasive skills training away from real patients and toward the simulation laboratory, evidence like this helps ensure that the tools awaiting trainees there are not just cheap and convenient, but demonstrably capable of measuring what matters: the difference between a procedure done right and one that goes dangerously wrong.

Subject of Research: Validity evidence for a low-cost inanimate simulation model used in subclavian central venous catheterization training

Article Title: Validation of an inanimate simulation model for subclavian central venous catheterization training

Article References: Galvis-Arenas, L., & Rodríguez, O. (2026). Validation of an inanimate simulation model for subclavian central venous catheterization training. Global Surgical Education – Journal of the Association for Surgical Education, 5(1), Article 158. https://doi.org/10.1007/s44186-026-00556-w

Image Credits: AI Generated

DOI: 10.1007/s44186-026-00556-w

Keywords: central venous catheterization, simulation-based education, subclavian approach, validity evidence, procedural skills training, medical education, surgical simulation, Messick framework, construct validity, low-cost simulator, patient safety, checklist assessment