IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 _______________________________________________________________________________________ Volume: 03 Issue: 06 | Jun-2014, Available @ http://www.ijret.org 520 DESIGN AND DEVELOPMENT OF ELECTRO-OPTICAL SYSTEM FOR ACQUISITION OF PPG SIGNALS FOR THE ASSESSMENT OF CARDIOVASCULAR SYSTEM Jayadevappa B.M 1 , Kiran Kumar G.H 2 , Anjaneya L.H 3 , Mallikarjun S. Holi 4 1 Professor and Head, Electronics and Instrumentation Engineering, Bapuji Institute of Engineering and Technology, Davangere, Karnataka, India 2 Assistant Professor, Electronics and Communication Engineering, Bapuji Institute of Engineering and Technology, Davangere, Karnataka, India 3 Associate Professor, Biomedical Engineering, Bapuji Institute of Engineering and Technology, Davangere, Karnataka, India 4 Professor and Chairman, Electronics and Instrumentation Engineering, University B.D.T. College of Engineering, Davangere, Karnataka, India 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 --------------------------------------------------------------------***---------------------------------------------------------------------- 1. INTRODUCTION The problems related to the cardiovascular system which are generally diagnosed by electrocardiogram (ECG) and blood pressure (BP) will not give clear information about peripheral blood circulation, volume changes and oxygen contents in the blood in relation with heart functioning. With each heart beat a pulse radiates out to the peripheral circulation causing a significant change in the arterial and capillary diameters which is equivalent to the changes in volume of the blood flowing in these vessels, as shown in Fig.1. The characteristics of these pulses are unique and are influenced by arterial ageing and diseases [1]. These pulses can be detected non-invasively using PPG system. The measurement of blood volume changes in the peripheral circulation beneath the skin by means of PPG depends on the fact that blood absorbs infrared light more strongly than skin and tissues [2]. The change in blood volume caused by the pressure pulse can be detected by illuminating the skin from a light source and measuring the amount of light transmitted to a photo-detector. The signal obtained from the photo-detector is related to pulsatile arterial blood volume changes and the signal is called as PPG, which provides a means of determining the properties of the vascular tissue, peripheral blood circulation and cardiac activity during each cardiac cycle.