Research advances in consistency and variability in ex vivo lung perfusion assessment metrics

Ex vivo lung perfusion (EVLP) has become an important platform for dynamic assessment and preservation of donor lungs, particularly for marginal grafts that might otherwise be declined for transplantation. Although EVLP has expanded the donor lung pool and improved opportunities for graft selection, the lack of standardized assessment criteria remains a major barrier to its broader clinical application. Considerable variability persists across centers, device platforms, perfusate compositions, perfusion flows, ventilation strategies, sampling time points, and thresholds used to determine transplant suitability. This review summarizes current evidence on the consistency and variability of EVLP assessment metrics, with emphasis on physiological parameters, ventilatory mechanics, hemodynamic indices, edema evaluation, biochemical and inflammatory biomarkers, microbiological assessment, imaging findings, and composite scoring systems. Core metrics such as the PaO₂/FiO₂ ratio, dynamic compliance, airway pressure, pulmonary vascular resistance, lung weight change, and inflammatory cytokine trends are widely used, but their interpretation remains highly protocol-dependent. Emerging biomarkers, radiological scores, lung ultrasound, and predictive models provide additional value, yet most remain limited by single-center validation and insufficient external reproducibility. We further discuss how device platforms, prolonged perfusion, therapeutic EVLP, and primary graft dysfunction (PGD) phenotypes influence metric interpretation. Overall, EVLP assessment should evolve from isolated static thresholds toward a hierarchical, multimodal, and dynamic framework that integrates physiological function, structural injury, inflammation, infection risk, and outcome-oriented prediction. Prospective multicenter studies with harmonized definitions, standardized data collection, and validated composite models are needed to improve donor lung selection, enable reliable cross-center comparison, and support safer expansion of lung transplantation.