A Signal Quality Index (SQI) is intended to assess whether reliable signals can be obtained from the machines using sensors. PPG technology thus represents a convenient and low-cost technology that can be applied to various aspects of cardiovascular monitoring, including the detection of blood oxygen saturation, heart rate, BP, cardiac output, respiration, arterial aging, endothelial function, microvascular blood flow, and autonomic. The below signal quality index evaluation diagram suggests a photo platysma gram (PPG) is a noninvasive circulatory signal related to the pulsatile volume of blood in tissue and is typically collected by pulse oximeters. You can use EdrawMax Online to create a similar-looking SQI Evaluation diagram for your academic usage.