defibrillator

Information about defibrillator

Published on October 21, 2009

Author: abhinavbit

Source: authorstream.com

Content

Slide 1: DEFIBRILLATOR Slide 2: NEED FOR A DEFIBRILLATOR Ventricular fibrillation is a serious cardiac emergency resulting from asynchronous contraction of the heart muscles. Due to ventricular fibrillation, there is an irregular or rapid heart rhythm. Fig. Ventricular fibrillation Fig. Normal heart beat Slide 3: Ventricular fibrillation can be converted into a more efficient rhythm by applying a high energy shock to the heart. This sudden surge across the heart causes all muscle fibres to contract simultaneously. The instrument for administering the shock is called a DEFIBRILLATOR. Possibly , the fibres may then respond to normal physiological pacemaking pulses. NEED FOR A DEFIBRILLATOR TYPES OF DEFIBRILLATORS : 4 TYPES OF DEFIBRILLATORS Internal External TYPES OF DEFIBRILLATORS : TYPES OF DEFIBRILLATORS Internal defibrillator Electrodes placed directly to the heart Eg.-Pacemaker External defibrillator Electrodes placed directly on the heart Eg.-AED THE POWER OF DEFIBRILLATION : 6 THE POWER OF DEFIBRILLATION Higher voltages are required for external defibrillation than for internal defibrillation. A corrective shock of 750-800 volts is applied within a tenth of a second . That is the same voltage as 500-533 no of AA batteries! Slide 7: DEFIBRILLATOR ELECTRODES Types of Defibrillator electrodes:- Spoon shaped electrode Applied directly to the heart. Paddle type electrode Applied against the chest wall Pad type electrode Applied directly on chest wall Slide 8: DEFIBRILLATOR ELECTRODES Slide 9: Fig.- Pad electrode DEFIBRILLATOR ELECTRODES Slide 10: PRINCIPLE OF DEFIBRILLATION Energy storage capacitor is charged at relatively slow rate from AC line. Energy stored in capacitor is then delivered at a relatively rapid rate to chest of the patient. Simple arrangement involve the discharge of capacitor energy through the patient’s own resistance. Slide 11: PRINCIPLE OF DEFIBRILLATION Slide 12: PRINCIPLE OF DEFIBRILLATION The discharge resistance which the patient represents as purely ohmic resistance of 50 to 100Ω approximately for a typical electrode size of 80cm2. This particular waveform Fig 13.9(b) is called ‘ Lown’ waveform. The pulse width of this waveform is generally 10 ms. Classes of discharge waveform : Classes of discharge waveform Monophasic pulse or waveform Bi-phasic pulse or waveform Slide 14: Classes of discharge waveform There are two general classes of waveforms: mono-phasic waveform Energy delivered in one direction through the patient’s heart Biphasic waveform Energy delivered in both direction throuth the patient’s heart Slide 15: Classes of discharge waveform Fig:- Generation of bi-phasic waveform Slide 16: Classes of discharge waveform The biphasic waveform is preferred over monophasic waveform to defibrillate .why????? A monophasic type, give a high-energy shock, up to 360 to 400 joules due to which increased cardiac injury and in burns the chest around the shock pad sites. A biphasic type, give two sequential lower-energy shocks of 120 - 200 joules, with each shock moving in an opposite polarity between the pads. Slide 17: AUTOMATIC EXTERNAL DEFIBRILLATOR Slide 18: AEDs require self-adhesive electrodes instead of hand held paddles. AED is a type of external defibrillation process. AUTOMATIC EXTERNAL DEFIBRILLATOR AED is a portable electronic device that automatically diagnoses the ventricular fibrillation in a patient. Automatic refers to the ability to autonomously analyse the patient's condition. The AED uses voice prompts, lights and text messages to tell the rescuer what steps have to take next. Slide 19: ELECTRODE PLACEMENT OF AED Anterior electrode pad Apex electrode pad Fig. anterior –apex scheme of electrode placement Slide 20: WORKING OF AED turned on or opened AED. AED will instruct the user to:- Connect the electrodes (pads) to the patient. Avoid touching the patient to avoid false readings by the unit. The AED examine the electrical output from the heart and determine the patient is in a shockable rhythm or not. Slide 21: When charged, the device instructs the user to ensure no one is touching the victim and then to press a red button to deliver the shock. when device determined that shock is warranted, it will charge its internal capacitor in preparation to deliver the shock. WORKING OF AED Many AED units have an 'event memory' which store the ECG of the patient along with details of the time the unit was activated and the number and strength of any shocks delivered. Slide 22: PRECAUTIONS IN DEFIBRILLATION PROCESS The paddles used in the procedure should not be placed:- on a woman's breasts over an internal pacemaker patients. Before the paddle is used, a gel must be applied to the patient's skin

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