Design And Development Of Portable Cardiac Defibrillators

In recent years,more and more people have died of cardiovascular disease,and in many cardiovascular disease,Ventricular fibrillation(VF)is one of the most important factor of death.Currently,the best way to treat VF is using impulse current to shock the patient’s heart and help it depolarizing to restore the normal rhythm.With the rapid development of computer technology in recent years,the electronic equipment of medical treatment is developing rapidly towards intelligence and humanization.Intelligent external defibrillator is an intelligent electronic medical instrument which using the authority method to shock heart by high voltage pulse,It has the functions of ECG signal acquisition,VF waveform recognition,and cardiac shock treatment.This new type of portable heart defibrillator(AED)is easy to carry and operate equipment,specially designed to provide convenient emergency for patients with ventricular fibrillation in public places.This paper takes the STM32F103ZET6 SCM of ARM as the core,carries on the software design and hardware development of the portable heart defibrillator.This paper first illustrates the principle of defibrillator’s recharge and discharge defibrillation and the classification of current defibrillator,and provideds the overall design of the system base on the principle of electrode defibrillation.The principle of its work is summarized as follows: in the patients with onset,acquiring his ECG waveform,combined with sample entropy algorithm to determine whether the occurrence of ventricular fibrillation,meanwhile detecting the pleural resistance patients,according to the resistance to choose appropriate defibrillation energy,If there was a ventricular fibrillation by the SCM’s judgment,then charged the storage capacitor to Charging the energy storage capacitor treatment patients hrough the electric shock.The hardware design of the defibrillator in this system is divided into the following modules: ECG acquisition module,human resistance detection module,harging defibrillation module and GPRS transmission module.The ECG acquisition module is to acquire the human’s ECG signal after processing by STM32 SCM,which is the basis for the follow-up work of the signal collection.The human body resistance detection module realizes the detection of the human chest resistance,and chooses the discharge energy size according to the detected resistance value.The charge defibrillation module using the battery to charge the capacitor,realizes the portability of the whole AED,and the discharge part is the key to the success of the defibrillation.Through the wireless remote transmission,GPRS transmission module sent the collected ECG signals to the designated medical staff.this part can Can increase one more security guarantee for the treatment of patients,which is also a major highlight of this article.In the Software part,the main program of system consist of ECG waveform acquisition program,ventricular fibrillation signal determination and discharge time selection program,ECG waveform remote transmission instruction configuration,and also includes inverter circuit and biphase wave discharge circuit driver.After repeated testing,it is proved that the operation of each module is in good condition.It is shown in:(1)the ECG signal is less noisy and the waveform is clear;(2)the human chest cavity resistance can be accurately collected;(3)the accumulator can store about 200 J in a short time when charging the capacitor;(4)the ECG waveform can be transmitted quickly to the designated mobile phone and clearly displayed.