Analog Multimodal Device for Early Neuroischemic Diabetic Foot Screening

Diabetic foot disease is one of the most severe complications of diabetes mellitus due to its strong association with ulceration, infection, lower-limb amputation, and increased mortality. In the Dominican Republic and the Caribbean, this burden is further intensified by limited access to early screening technologies and the need for robust, field-deployable solutions adapted to resource-constrained healthcare environments. The objective of this study is to propose a fully analog, discrete-electronics screening device for early neuroischemic diabetic-foot risk assessment. The proposed system integrates two complementary physiological biomarkers: bilateral plantar thermal asymmetry, as an indicator of localized inflammatory stress, and post-occlusive microvascular reactivity, assessed through hyperemic time-to-peak using reflective photoplethysmography. The architecture is based on a hardware-only design that eliminates the need for software, microcontrollers, or digital signal processing, and includes multisite plantar temperature sensing, optical perfusion measurement with synchronous demodulation, a controlled vascular occlusion module, and comparator-based risk classification. This design enables deterministic behavior, direct signal traceability, and local interpretability, which are essential for screening applications in low-infrastructure settings. The main contribution of this work lies in the integration of inflammatory and vascular physiological domains within a single discrete-electronics platform. Unlike existing approaches that rely on digitally mediated systems, the proposed method provides a transparent and resilient alternative for early screening. The study is presented as a design-and-rationale framework with a defined validation pathway, providing a foundation for prototype development, experimental validation, and potential clinical application.