Effect of posture on photoplethysmography signals from the posterior tibial artery in adults with and without type 2 diabetes

Diabetic foot complications remain a major cause of disability in diabetes and represent a severe consequence of poor glycaemic control, primarily driven by peripheral arterial obstruction, neuropathic damage, and compromised tissue perfusion. Photo-plethysmography (PPG) signals offer a non-invasive means of assessing vascular health. The objective is to provide insights that aid in tailoring interventions for subjects with diabetes. The study examines posture-related changes on PPG parameters at the posterior tibial artery in healthy subjects (Group A) and subjects with diabetes (Group B). Physiological parameters analysed included pulse amplitude, mean Peak-to-Peak-Interval (PPI), SDPP, Low-Frequency to High-Frequency ratio (LF/HF), b/a ratio, and (b-c-d-e)/a ratio. Postural effects were evaluated in 30 subjects per group using two-way ANOVA and Mann-Whitney U tests. Morphological analysis of PPG waveforms in Group B revealed a gradual systolic rise, prolonged diastolic decay, and a less prominent dicrotic notch, indicating accelerated vascular aging. Significant main effects of posture were found for pulse amplitude, mean PPI, SDPP, LF/HF, b/a, and (b-c-d-e)/a ratio. Furthermore, posture × group interaction effects reached significance for mean PPI, SDPP, LF/HF, and b/a ratio. The study reveals posture-related variations in PPG signal quality and autonomic function, with supine posture yielding the most stable waveforms. These findings may offer preliminary insights into posture-sensitive PPG measures that could support future research and aid in the clinical assessment of diabetic foot complications.