Bridging the fidelity gap: a multi-phase usability engineering approach for validating automated monitoring systems in the ICU

Purpose: Automated urine output monitoring enhances accuracy and traceability in critical care, yet its implementation is often hindered by ergonomic and environmental barriers. This study evaluated the safety and usability of an automated monitoring system through a Human Factors and User-Centered Design (UCD) approach to identify factors influencing clinical integration. Methods: A prospective, multi-phase study was conducted following IEC 62366-1/2 standards. First, a PRISMA-ScR scoping review was performed to establish design requirements. Subsequently, usability validation was conducted with 30 nursing professionals across a progressive fidelity framework: (I) formative laboratory evaluation; (II) summative testing; and (III) high-fidelity in-situ simulation within an active Intensive Care Unit (ICU). Usability was quantified via the System Usability Scale (SUS) and task performance analysis. Results: The scoping review identified a lack of structured human factors validation in existing technologies. In the validation phase, although no critical safety errors occurred, a significant "fidelity gap" was observed: perceived usability declined from "Good" in the laboratory (SUS = 77.5 +/- 14.9) to "Marginal" in the real ICU environment (SUS = 63.5 \+/- 24.6). Physical ergonomic constraints, specifically device fixation and height-gravity dilemmas, were the primary barriers to optimal usability, rather than software interface logic. Conclusion: The evaluation of this automated monitoring technology highlights the critical role of multi-phase usability testing in identifying safety gaps that remain latent during controlled laboratory evaluations. The emergence of a 'fidelity gap' in the in-situ phase demonstrates that the clinical environment is a decisive variable in the performance of medical devices.