Gathering Response Process Validity Evidence for an Ultrasound-guided Thoracentesis Phantom Using Eye-tracking Metrics

INTRODUCTION: Simulation-based education is essential for developing procedural competence in ultrasound-guided thoracentesis (USGT). However, few USGT phantoms integrate objective metrics to assess cognitive workload. This study used eye tracking (ET) to quantify cognitive demand and establish preliminary validity evidence for a novel, anatomically variable USGT phantom. MATERIALS AND METHODS: Thirteen experienced clinicians performed simulated USGT on a modular phantom divided into 4 quadrants of increasing difficulty. Eye-tracking glasses recorded gaze behaviour across 2 areas of interest: the ultrasound monitor and the phantom. Cognitive workload was assessed through fixation and revisitation counts. Postsimulation, participants completed a Likert-scale questionnaire and provided qualitative feedback. RESULTS: The monitor elicited significantly more fixations than the phantom [[91.6 ± 12.4 vs. 38.8 ± 12.4; F(1,87.1) = 20.26, P < 0.001], particularly in the most complex quadrant (Q3). Revisitation counts trended higher on the monitor but were not statistically significant overall (P = 0.08); however, Q3 showed significantly more revisitations than Q4 (P = 0.01). Q3 also required the most puncture attempts (2.31 ± 0.40; P = 0.001), aligning with increased cognitive workload. Realism and educational usefulness received high ratings (24/30 and 14.1/15, respectively). Thematic analysis highlighted anatomic fidelity, graduated difficulty, and integration of image acquisition with needle guidance as key strengths. ET revealed quadrant-specific variations in cognitive workload, demonstrating the phantom's structural design potential for progressive, scaffolded training. Fixation and revisitation metrics provided response process validity evidence, linking gaze behaviour to task complexity. Expert feedback confirmed the phantom's realism and educational value, reinforcing its feasibility as a platform for structured, just-in-time training. CONCLUSION: ET offers a powerful lens to evaluate cognitive demands in procedural simulation. This study demonstrates how gaze metrics can inform phantom design and assessment, enhancing the fidelity and effectiveness of USGT training.