Design and Implementation of Non-invasive Continuous Blood Pressure Measurement and Monitoring System Using Photoplethysmography

Non-invasive continuous blood pressure measurement has become very popular for hypertensive patients to prevent cardiovascular problems. Blood pressure readings are not continuous in the conventional cuff sphygmomanometer system. We have proposed microcontroller based non-invasive continuous blood pressure measurement technique in which no cuff is used and photoplethysmogram (PPG) signal is taken only from the finger. It gives no pain to human because no catheter is needed to insert inside the body. A sensor network consisting of light emitting diode and light dependent resistor is used to get a PPG signal by the volume oscillometric method. The variation of blood volume in the finger is measured by this optical sensor. The variation of blood volume changes to blood pressure linearly. Automatic multi-scale based peak detection algorithm is used to detect maximum and minimum peaks of continuous PPG signal which corresponds to systolic and diastolic pressure after some simplification. Our proposed system is controlled by Arduino Uno which has on-chip microcontroller ATmega328P. We measure continuous blood pressure with 30 seconds delay between adjacent readings for twelve subjects. The results are verified by conventional cuff sphygmomanometer system. The mean difference is less than ± 5 mmHg. Therefore, the proposed system is less expensive and gives quite reliable and more accurate results according to international standards.