Live demonstration: Pulse transit time measurement on a modified weighing scale for cuffless blood pressure estimation

Summary form only given. The demonstration setup will include a modified weighing scale with an analog circuit built into the device, a National Instruments myRIO system for data acquisition, and a laptop for visualization of the data and implementation of the demo. The weighing scale measures the ballistocardiogram (BCG) signal - the reaction forces of the body to ejection of blood from the heart into the vasculature and movement of the blood through the vascular tree [1] - as well as a reflectance mode photoplethysmogram (PPG) from the top of the foot, representing the local blood volume pulse [2]. The BCG is measured from the strain gauges built into the scale, interfaced to a low noise instrumentation amplifier and filter circuit for amplifying the AC component of bodyweight which fluctuates synchronously with the heartbeat. The reflectance PPG is measured using a custom strap that we have developed, including an array of photodiodes and light emitting diodes (LEDs) for illuminating the top of the foot - close to the dorsal artery - and measuring the changes in reflectance at that location associated with the blood volume pulse. The time delay from the BCG I-wave to the PPG waveform foot is pulse transit time (PTT), and we have shown in previous work that this measurement of PTT is correlated to the subject's blood pressure [3].