In this tutorial we show how optical sensors can be exploited in order to manufacture a conformable system able to monitor the arterial stiffness by means of a fully optical technique, which is the photopletysmography PPG. We show how a PPG signal can be usefully monitored by exploiting also the ECG signals. In the tutorial, after an introduction on the PPG/ECG combined system, developed within the ASTON!SH ECSEL JU EU project, we proceed with a demo-live of a PPG/ECG portable system.
In details, we present a portable PPG/ECG combo system (Fig. 1) developed by the LOOX (Laboratory of Optics and OptoelectroniX) of the University of Palermo, Italy. The system supports the synchronous acquisition of 8 channels (5 PPG + 3 ECG leads) with 24-bit resolution, a sampling rate of 1 kSPS and is capable to visualize, in real-time, the following physiological parameters: heart rate, ECG R-R intervals or PPG pulse-pulse interval, Pulse Arrival Time, Pulse Transit Time, Pulse Wave velocity and breathing rate. The visualization is achieved through an appositely developed Graphical User Interface (Fig. 2). The physiological parameters can be plotted in real time and saved for offline post-processing.
Each PPG probe includes a Silicon Photomultiplier (SiPM) detector, provided by STMicroelectronics, and a 735/850 nm Bi-Color LED. The functional parts of the system are: the Analog Front-End (Texas Instruments ADS1298, designed for Biopotential Measurements), the circuitry to drive the LEDs of the probes (employing an I2C interface), an STM32 microcontroller and the power supply circuitry. The system also includes USB and Bluetooth interfaces to transmit (both wired and wirelessly) the acquired data to the PC and is battery operated using standard AA batteries.
Fig. 1 The portable PPG/ECG combo system with the standard ECG probes and a custom PPG probe.
