DefibrillatorsPublished on 10/8/2018 & updated on 29/8/2018
What is Fibrillation?When heart pumps blood through heart muscles, they spread over atria and makes the heart chambers to contract together. The condition at which synchronization of heart muscle is lost is known as fibrillation. During this fibrillation condition, the normal rhythmic contraction of atria and ventricles does not occur. They are replaced with irregular twitching of muscle walls. There are two types of fibrillation namely atrial fibrillation and ventricular fibrillation. During fibrillation, heart muscles are stimulated at a constant rate.
Atrial FibrillationAtrial Fibrillation is due to atrial muscles. During atrial fibrillation condition, a ventricle does not function normally. Before the atrial contraction, almost all blood flows into ventricles. This reduces
Ventricular FibrillationVentricular fibrillation occurs due to ventricle fibrillation. It is more dangerous than the atrial fibrillation. During this condition, ventricles cannot pump blood. In this condition uncoordinated movement of ventricle walls results in body abnormality. Therefore, it has to be treated immediately to avoid death of the patient. This condition can be made as a regular rhythm when a high voltage shock is applied to heart. Sudden application of shock makes the heart muscles to contract simultaneously.
How to Treat Fibrillation Problems?Therefore, the defibrillator is the device used to provide this electric shock. Defibrillators are the device that produces myocardial depolarization and stops the condition of fibrillation. Even after giving sufficient shock to the patient, if the heart does not contract intact, pacemakers are used to restart the myocardium contraction. Defibrillator is used to treat sudden cardiac arrest.
Types of DefibrillatorsTwo types of defibrillators are showing below.
External DefibrillatorExternal defibrillator is pressed on the chest using paddle shaped electrodes. The electrode has a bottom made of copper disc with a diameter range of 3 to 5 cm for children and 8 to 10 cm for adults. It has an insulated handle to hold the device. The voltage value required ranges from 1000V to 6000V. Electrode gel is applied on the chest before placing the electrode so that the contact impedance on the chest is around 100 Ω. In general, a D.C defibrillator can deliver about 50 to 400 J of energy for 1 to 5 milli seconds. Therefore, the amount of current that passes through chest is between 10 to 60 amperes. Electrodes can be placed on two ways either in anterior – anterior position or in anterior – posterior position. In anterior – anterior position current flows through the heart. In this position, one paddle is placed above the heart apex and another paddle on the sternum. Hence, the current flows in the direction of bottom to top of the heart. Whereas, in anterior – posterior position blood flows to chest from behind through heart.
Internal DefibrillatorThis type of defibrillator is used when chest is opened. Electrodes are in shape of large spoons and they have an insulated handle. Internal d.c defibrillator uses voltage values range between 50 V to 1000 V to provide shock. The electrodes used are in direct contact with the heart so the contact impedance is 50 Ω. Hence, the amount of current passing through heart is about 1 to 20 amperes. The amount of excitation energy required for internal defibrillator is between 15 to 50 J for a time of 2.5 to 5 millisecond.
Need for Insulation HandleWhen a person applies electrode on the patient he has to be prevented from accidental shocks so insulated handles are provided. To discharge the defibrillator a thumb switch is present on one or both handles. To charge the defibrillator in modern devices a charge switch is placed on the handle of the paddle.
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