Speckle-based non-invasive assessment of cardiac vital signs

otoplethysmography (PPG) is an optical method that measures blood volume variations over time by detecting changes in non-coherent light absorption. It provides valuable information on heart rate, peripheral oxygen saturation (SpO2), and can serve as a proxy for blood pressure. Even though the above-mentioned technique has been extensively described in the literature, the actual clinical implementation is hampered due to low signal quality in people with skin melanin, low perfusion, or during varying ambient light conditions. Speckle plethysmography (SPG) presents a promising alternative, this method is based on Laser Speckle Contrast Imaging (LSCI), utilizing speckle patterns that are created on the detector when coherent light interacts with a tissue. Both SPG and LSCI quantify speckle blur due to movement of scatter particles (e.g. red blood cells). Unlike PPG, SPG is inherently less affected by changes in ambient light and skin melanin, making it a more reliable option for diverse clinical settings.