The Design Of Automated External Defibrillator Based On ARM9 Embedded System

Cardiac arrest, also called sudden cardiac death, is a major killer to the human life. Most of SCD is caused by ventricular fibrillation (VF) which is one of the most serious arrhythmias. A generic approach to curve SCD is using high voltage electric shock to defibrillation.In this thesis, we first do a survey of the development status of the defibrillation products. Then we design and develop a small and intelligent automated external defibrillator(AED)prototype. The design highlighted the entire development process, and described the detail of each module.First, we introduce the working principle and classification of AED, and then proposed the overall scheme for our design which can be summarized as follows: detect the human impedance first. If it is within the normal range, collect the ECG signal and use the combined algorithm to test whether the VF occurs, then charge the capacitor to shock the body.After that, we discussed the functional modules respectively. The hardware is under the control of the main chip S3C2440 microprocessor, and can be divided into three large modules: the ECG acquisition module, the impedance detection module and high voltage charging module based on fly- back power. Detailed description of each one and the key technology solutions, particularly in the impedance detection module and high voltage charging module are presented. We then proposed some practical and efficient ideas about the components and their parameters. The software elaborated on both the driver and applications; A simple algorithm to use detect VF, called approximate entropy, is realized under the VC++6.0. In addition, we design a GUI to control some peripheral devices based on QT designer.After repeated experiments and tests, it is shown that each module works well, and the technical performance basically meet the requirements: (1) the ECG acquisition module can collect the signal from the body surface with little noise; (2) the charging module can obtain a high voltage up to 1300V within 15 seconds; (3) the impedance measurement module can obtain a stable current signal which is used to go through the human body. (4)The software and the hardware work properly together, and the GUI make the entire system intelligent and friendly.With further improvement, we believe the developed device in this thesis could become a prototype of industrial products.