Test-retest reliability of endothelial ischemia reperfusion injury in healthy adults

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Introduction: Ischemia-Reperfusion Injury (IRI) describes the paradoxical phenomenon through which the restoration of blood flow following prolonged ischemia exacerbates tissue damage during reperfusion. IRI can be experimentally modeled in humans through transient upper-limb ischemia, which temporarily impairs endothelial-dependent vasodilation, as assessed by flow-mediated dilation (FMD) of the brachial artery. Despite the widespread adoption of this experimental model, its reproducibility has not been established. Therefore, our objective was to evaluate the test–retest reliability of IRI-induced endothelial dysfunction in healthy adults, measured by reductions in FMD (ΔFMD). We hypothesized that IRI would elicit consistent reductions in FMD across two visits. Methods: Eight young, healthy adults (2F/6M, age = 28 ± 7yrs) reported to the lab for two identical experimental visits separated by 2 ± 2 days. Participants were positioned supine and instrumented for measurement of brachial artery FMD at rest and following IRI. IRI was induced via 20-min of upper-arm cuff inflation (250 mmHg) followed by 20-min of reperfusion. Immediately following the reperfusion period, FMD was reassessed. A single unblinded sonographer performed all analyses. Reproducibility of ∆FMD was evaluated using intraclass correlation coefficient (ICC; two-way mixed effects, absolute agreement, 2,1 model) with 95% confidence intervals. Results: Baseline FMD was similar across visits (Visit 1 Pre-IRI: 6.3 ± 1.6%; Visit 2: Pre-IRI: 6.1 ± 1.9%, P = 0.64) and was reduced following IRI (Visit 1 Post-IRI: 2.7 ± 2.3%; Visit 2 Post-IRI: 2.6 ± 1.8%, P = 0.76). The magnitude of reduction (∆FMD) was consistent between visits (ICC = 0.71 [0.04−0.94], SEM = 1.03%, CV = 17.42%), demonstrating a high degree of reproducibility. Conclusion: To the best of our knowledge, this is the first investigation to establish the reproducibility of endothelial IRI in humans. We demonstrate that IRI reduces brachial artery FMD to a similar extent across multiple study visits. These findings support the use of this experimental model as a reliable method of investigating mechanisms of vascular protection and for testing interventions designed to improve endothelial resilience to IRI-induced impairments in humans. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

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