Automated monitoring of urine output in hospitalized patients with indwelling urinary catheters: a clinical evaluation on the cardiology ward

BACKGROUND: Urine output (UO) is a key clinical parameter for assessing hemodynamic status, yet manual UO measurements are labour-intensive, and documentation is often incomplete and error-prone. The Gravity of Flow study evaluated an in-house developed urine production gauge (UPG), designed as a reusable-cost system compatible with standard urine bags for automatic, continuous UO measurement and Electronic Health Record (EHR) integration. METHODS: This single-centre observational study enrolled 25 cardiology patients (519 h) with indwelling urine catheters. To assess completeness and volume accuracy, UPG performance was compared against standard manual urine charting and a 24-hour container (gold standard). RESULTS: The UPG achieved superior median completeness compared to manual charting (100% vs. 40%, p < 0.001). The device demonstrated high accuracy (median absolute percentage error 2.3%) and minimal bias (median -3 mL), meeting ±5% equivalence criteria (78.3% within bounds). In contrast, manual charting failed to meet equivalence. Performance of the UPG remained consistent across various UO flow rates. CONCLUSION: By providing superior, automated UO data (accuracy, completeness, reliability), the UPG has the potential to optimise fluid management, enable earlier intervention, and reduce nursing workload. Future research should validate these benefits across various clinical settings and over longer periods.