Automate Pulse Interface System (APIS)

Abstract

Photoplethysmography (PPG) is a simple non-invasive optical technique used to record blood volume flow changes in human peripheral vascular network. It is the basic technique exploited in pulse oximetry measurement to estimate the heart rate and blood oxygenation. The PPG may also measure physiological responses at different body points on human peripheries. The PPG technique provides possible assessment of the cardiovascular system and related diseases, thus can inform the human health condition. Standard oximeters in the market mostly are monitoring only oxygen level and heart rate. PPG monitoring systems are often too expensive in the market. This project attempts to display multiple signals, which are vital signals obtained from human body using a commercial finger pulse oximeter probe to record the finger PPG signals which indirectly have the information related to the heart. This requires hardware interfacing and microprocessor programming to control the electronic circuitry and Graphic User Interface (GUI) to display the result. Output current from phototransistor are converted to voltage by trans-impedance amplifier. Then these amplified analog signals are filtered and only low frequencies signals of below 10Hz are passed through after which the signals being digitalized before the microcontroller PIC16F877A. A minimum of 1000 samples per second are captured and send to a personal computer through a serial to USB interface. Visual Basic 2006 (VB6) is used as the platform for user interface to record, display and save the data. The Graphic User Interface (GUI) program using VB6 displays in real time the graph of the infrared (IR) light from the IR LED being moderated by the heart activity and detected by the phototransistor situated in the finger oximeter probe. Soft filtering by moving average filter and data logger are also done in the VB6. For post data processing the data recorded and saved are also plotted using Microsoft Excel and Matlab for further analysis. Results showed that the system is developed successfully. Nevertheless, fine tuning the VB6 program can be made for system improvement especially to tackle the issues of proper data sampling and saving.