Design and Development of a Modular, Multichannel Photoplethysmography System

Abstract

In this paper, we present the design, development, and validation of a 'modular photoplethysmography (PPG) system called ZenPPG. This portable, dual-channel system has the capability to produce "raw" PPG signals at two different wavelengths using commercial and/or custom-made PPG sensors. The system consists of five modules, each consisting of circuitry required to perform specific tasks, and are all interconnected by a system bus. The ZenPPG system also facilitates the acquisition of other physiological signals on-demand including electrocardiogram (ECG), respiration, and temperature signals. This report describes the technical details and the evaluation of the ZenPPG along with results from a pilot in vivo study on healthy volunteers. The results from the technical evaluations demonstrate the superiority and flexibility of the system. Also, the systems' compatibility with commercial pulse oximetry sensors such as the Masimo reusable sensors was demonstrated, where good quality raw PPG signals were recorded with the signal-to-noise ratio (SNR) of 50.65 dB. The estimated arterial oxygen saturation (SpO 2) values from the system were also in close agreement with commercial pulse oximeters, although the accuracy of the reported SpO 2 value is dependent on the calibration function used. Future work is targeted toward the development of variations of each module, including the laser driver and fiber optic module, onboard data acquisition and signal processing modules. The availability of this system will help researchers from a wide range of disciplines to customize and integrate the ZenPPG system to their research needs and will most definitely enhance research in related fields.

In silico and in vivo investigations using an endocavitary photoplethysmography sensor for tissue viability monitoring

“…To adjust the driving current of the LEDs, which proportionally adjusts the light intensities, and to condition the acquired PPG signals, a PPG processing system, ZenPPG, which was developed by the Research Centre for Biomedical Engineering at City, University of London, was utilized. 28 The portable, battery-operated ZenPPG permits the acquisition of raw, dual-wavelength PPG signals prior to the analogue-todigital conversion of signals for offline analysis. Contact measurements, where the sensor-tissue separation is 0 mm, were achieved by covering the PPG sensor in a clear plastic sheath.…”

A Novel Photoplethysmography Sensor for Vital Signs Monitoring from the Human Trachea

“…PPG instrumentation has been developed [13,14] to drive the active elements of the sensor and process the raw signals ready for data storage on a laptop computer. The PPG device, named ZenPPG, has the ability to drive multiple physiological sensors and can be customised for nearly any clinical trial or in vivo study.…”

A Pulsatile Optical Tissue Phantom for the Investigation of Light-Tissue Interaction in Reflectance Photoplethysmography

“…The reflectance PPG sensor was attached to a custom-built PPG processing system, "ZenPPG". ZenPPG is a dualwavelength, dual-channel research PPG system developed by the Research Centre for Biomedical Engineering at City, University of London [17] [18]. The main functionalities of the ZenPPG are the acquisition of raw PPG signals (AC + DC), adjustment of light intensities and the ability to drive custom-made and commercial PPG sensors.…”