Blood Pressure Sensor (2)

Abstract

Blood pressure is important to monitor as there are about one-third of people in Hong Kong have high blood pressure. However, traditional inflatable blood pressure monitor is very inconvenient and uncomfortable. Moreover, it is impossible to measure blood pressure in a continuous manner. This project is to develop a wearable cuffless blood pressure sensor to help people continuously monitor their blood pressure. Blood pressure is usually expressed as systolic blood pressure (SBP) and diastolic blood pressure (DBP). They can be estimated by pulse transit time (PTT). Two pulse sensors are used to get the pulse signals of our heart beat. PTT are calculated by the time difference of the peaks of the two pulse signals. Photo plethysmography (PPG) technology is selected to generate pulse signals. Two pulse sensors are made, one on fingertip and one on forearm. A band pass filter is added into the circuit to filter out unwanted frequency. To strengthen the signal, amplifiers are added into the circuit. Arduino Bluno is selected to do the data processing. It convert analog signal to digital signal and send out information by Bluetooth. An Android application developed to receive data from Bluno through Bluetooth. Data processing also involved in the application. A traditional blood pressure sensor are used for calibration. The relation between PTT and blood pressure are found after a number of experiments. Therefore, the user's diastolic and systolic blood pressure are calculate in the application and display on mobile phone screen. In addition, user's heart pulse and heart rate will display on the screen.