Preliminary study to assess vascular health for future use in patients with peripheral arterial disease using pressure dependent dynamic optical spectroscopy

Peripheral arterial disease (PAD) affects over 8.5 million people in the United States. Diagnostic tools to identify PAD continue to have low sensitivity for patients with diabetes and/or with poor vascular health in the small vessels of the lower extremities. A handheld device developed in our laboratory may address these limitations. The device combines dynamic vascular optical spectroscopy (DVOS) with pressure sensing to monitor the relationship between applied pressure and blood volume changes in tissues of interest, which is expected to differ between healthy and PAD subjects. Our probe is 20mm in diameter with the bottom face housing two infrared sources (wavelength λ = 780nm and 850nm) and one silicon photodetector located around 10mm from each source. The DVOS system continuously records the reflected light intensity from the local tissue at a frame rate of 10.24 frames per second. Simultaneously, the load applied by the probe to the tissue surface is measured continuously with a force sensor at the same frame rate. During data acquisition, the applied load is gradually increased, resulting in dynamic changes of the monitored DVOS signals. These recorded signals provide information on the response of the local tissue perfusion to changes in applied pressure. Here, we report on a preclinical study monitoring 3 vascular locations in the lower extremities of 3 healthy volunteers. Preliminary results suggest that on average there is a 0.03% change in total hemoglobin concentration per 10 mmHg change in applied pressure. We expect these changes to be significantly smaller in PAD patients.