Noninvasive optical methods to assess tissue perfusion in patients with peripheral arterial disease and diabetes mellitus: a scoping review and discussion

Background: The global incidence of peripheral arterial disease (PAD) is 10.5 million individuals annually. There are 113 million people affected globally, which can result in limb loss. PAD is often part of a greater set of comorbidities, including diabetes mellitus (DM), chronic kidney disease, coronary artery disease and obesity. Diabetic foot ulceration is a debilitating complication of DM that occurs owing to a combination of neuropathy, PAD, and structural biomechanical changes. Poor tissue perfusion in the context of microangiopathy can result in impaired wound healing and eventual limb loss. The combination of diabetic foot ulceration and PAD can be burdensome socially, psychologically and economically, for patients and health systems. It is, therefore, imperative to be able to identify and continuously monitor high-risk patients to aid in the prevention, monitoring, and management of these conditions in a noninvasive, easily accessible and cost-effective manner. We sought to evaluate the current evidence relating to noninvasive optical tissue perfusion assessment modalities available and their use in patients with PAD and individuals with DM. We also aimed to collate how each assessment modality worked, and its advantages and disadvantages. Methods: A systematic literature search was conducted of the Embase and Medline (via the Ovid interface), PubMed, and Google Scholar databases for articles relating to PAD in individuals with DM. Articles were reviewed by two independent reviewers. Findings were collated for each method of tissue perfusion. Results: In the final review, 35 articles met criteria for inclusion. The modalities discussed included photoplethysmography, spatial frequency domain imaging, hyperspectral imaging, laser Doppler, laser speckle flowgraphy, near infrared spectroscopy, thermography, photoacoustic imaging, and indocyanine green. Conclusions: Several modalities are available for the noninvasive monitoring of tissue perfusion in individuals with DM and PAD that show promise. Their clinical applicability is an area of ongoing research