DESIGN AND DEVELOPMENT OF ELECTRO-OPTICAL SYSTEM FOR ACQUISITION OF PPG SIGNALS FOR THE ASSESSMENT OF CARDIOVASCULAR SYSTEM

Jayadevappa B.M, Kiran Kumar G.H, Anjaneya L.H, Mallikarjun S. Holi

Abstract: The revolution in semiconductor technology has lead to the development of efficient optical techniques for acquisition of biomedical signals which can be used effectively in diagnostics. The interaction of light with biological tissue is complex and includes the optical processes like scattering, absorption, reflection, transmission and fluorescence. The amount of light received by the photo-detector varies in accordance with the blood volume, blood vessel wall movement and the orientation of red blood cells (RBC). In the present work a real-time electro-optical based photoplethysmograpgh system is developed to monitor and record the variations in the volume of blood with each heart beat resulting in the form of a signal called photoplethysmogram (PPG). The developed sensor unit consists of a source of light and photo-detector both packed in the form of probe and fitted to patient’s index finger. The PPG signal acquired comprise a pulsatile (AC) waveform attributed to cardiac synchronous changes in the blood volume with each heart beat and is superimposed on a slowly varying (DC) baseline with various lower frequency components attributed to respiration, sympathetic nervous system activity and thermoregulation. For remote monitoring of PPG signals, a system is designed and developed based on ZigBee wireless technology. From the transmitted and received PPG signals, parameters like pulse rate (PR), average pulse rate (APR), pulse rate variability (PRV) and frequency spectrum can be determined which are of diagnostic importance. The PPG system designed and developed in the present work is non-invasive, portable, reliable and cost effective. The system can be effectively used for handicapped patients, ambulatory conditions and in post operative care units for continuous monitoring and assessment of cardiovascular patients. The preliminary study and results shows that the developed wireless PPG system can be an alternative to the traditional methods used for remote monitor of cardiovascular and respiratory system and their disorders.

Keywords: Photoplethysmogram (PPG), cardiovascular system, pulse rate, ZigBee

DOI: https://doi.org/10.15623/ijret.2014.0306097