Foot complications, including sensory and motor impairments and ulcerations, are common in individuals with type 2 diabetes (T2D) and peripheral artery disease (PAD). These manifestations may arise partly from disturbances in microvascular function within the skin, subcutaneous tissue, and skeletal muscle of the foot. However, microvascular reactivity in plantar, load-bearing regions remains poorly characterized. Reactive hyperemia following brief circulatory occlusion provides a physiologically meaningful approach to assess microvascular reserve and oxygen delivery capacity. Objective: To evaluate plantar forefoot microvascular function by quantifying near-infrared spectroscopy (NIRS)–derived tissue oxygenation at baseline, during cuff-induced ischemia, and throughout reactive hyperemia in individuals with T2D, PAD, and non-diabetic controls. Hypothesis: Both T2D and PAD would exhibit reduced and slower reperfusion responses compared with non-diabetic controls. Methods: Participants included non-diabetic controls (n=20, 16 females, 63±8 yr, HbA1c 5.7±0.4%, ankle–brachial index ABI 1.15±0.06), T2D (n=11, 6 females, 65±7 yr, HbA1c 7.2±1.0%, ABI 1.14±0.16), and PAD (n=9, 2 females, 69±9 yr, HbA1c 7.0±1.3%, ABI 0.64±0.15). A flexible NIRS probe placed on the plantar forefoot measured tissue oxygen saturation (StO 2 ). After baseline, an ankle cuff was inflated to 220 mmHg for 5 minutes and then released for 5 minutes. Outcomes included baseline StO 2 , the desaturation slope during occlusion (Slope 1), the reperfusion slope after deflation (Slope 2), the change from baseline to peak (ΔStO 2 ), and time-to-peak (TTP). Group differences were assessed using ANOVA with Tukey post hoc tests. Results: Baseline plantar StO 2 was similar across groups (Controls: 42.2±9.6%; T2D: 44.3±11.6%; PAD: 43.4±8.9%; p >0.05). Significant group effects were observed for Slope 1 (p=0.006), Slope 2 (p=0.007), ΔStO 2 (p=0.002), and TTP (p=0.04). Compared with Controls, the PAD group demonstrated faster desaturation during cuff occlusion (Slope 1: PAD –0.050±0.010 vs. Controls –0.030±0.010 %/s, p=0.005), slower reperfusion following cuff release (Slope 2: PAD 0.23±0.05 vs. Controls 0.39±0.12 %/s, p=0.005), a smaller increase in StO 2 from baseline to peak (ΔStO 2 : PAD 13.3±5.1 vs. Controls 22.6±7.5 %, p=0.0008), and a longer time-to-peak (TTP: PAD 137.9±46.5 vs. Controls 81.0±23.2 s, p=0.0001). The T2D group exhibited intermediate responses without significant differences from Controls (all p >0.05). Conclusion: PAD is associated with impaired plantar forefoot microvascular reactivity, characterized by slower and blunted reperfusion during reactive hyperemia. Responses in individuals with T2D were preserved. NIRS-derived oxygenation kinetics provide a sensitive method for assessing microvascular reserve in weight-bearing foot tissues and may help clarify the heightened vulnerability to complications in PAD. Funding: Supported by The John Martinson Honors College’s Research Breakthrough Award from Purdue University. 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.
Chan et al. (Fri,) studied this question.