Defibrillation is a medical technique used to counter the onset of ventricular fibrillation, a common cause of cardiac arrest, and pulseless ventricular tachycardia, which sometimes precedes ventricular fibrillation but can be just as dangerous on its own.
Defibrillation is a technique used in emergency medicine to terminate ventricular fibrillation or pulseless ventricular tachycardia. It uses an electrical shock to reset the electrical state of the heart so that it may beat to a rhythm controlled by its own natural pacemaker cells. It is not effective for asystole (complete cessation of cardiac activity, more commonly known as "flatline") and pulseless electrical activity (PEA). Ventricular tachycardia with a pulse is treated with medication (if hemodynamically stable), or syncronized cardioversion (if hemodynamically unstable).
The equipment used in this process is called a defibrillator. The "sync" function must be deactivated, otherwise the machine will be searching for an organized R-wave to syncronize the shock with. Defibrillation is part of advanced cardiac life support (ACLS).
The purpose of defibrillation of ventricular arrhythmias is to apply a controlled electrical shock to the heart, which leads to depolarization of the entire electrical conduction system of the heart. When the heart repolarizes, the normal electrical conduction may assert itself, in which case the ventricular arrhythmia is terminated. However, if enough energy is not used for defibrillation, the heart may not be completely depolarized, in which case the ventricular tachycardia or fibrillation may not be terminated. Also, if the heart itself is not getting enough oxygen or if there is an instability of the electrolytes in the cardiac cells, the ventricular arrhythmia may recur.
The shock is generally conducted through the heart by two electrodes, in the form of two hand-held paddles or adhesive patches depending on the variety of the defibrillator. One electrode is placed on the right side of the front of the chest just below the clavicle, and the other electrode is placed on the left side of the chest just below the pectoral muscle or breast. Open-chest defibrillators also exist, which have electrodes in the form of two cup-shaped paddles that surround the sides of the heart and shock it directly. Open-chest defibrillators generally require less energy to operate due to direct contact with the heart.
Although the process of defibrillation can be repeated, the number of attempts is, in practice, limited, to a series of three or four attempts at increasing voltages, as the likelihood of restoring normal heart rhythm is much less in successive attempts.
A defibrillator is a medical device used in the defibrillation of the heart. It consists of a central unit and a set of two electrodes. The central unit provides a source of power and control. The two electrodes are placed directly on or in the patient. The device is designed to deliver an electric shock to the patient, in an effort to stop ventricular fibrillation.
I was lucky enough to see this item placed next to one patient who had a metabolic disorder, rise of ammonium level which affected his mental state. He was sleeping the whole time.
Defibrillation was invented in 1899 by Prevost and Batelli, two Italian physiologists. They discovered that electric shocks could convert ventricular fibrillation to sinus rhythm in dogs. The first case of a human life saved by defibrillation was reported by Beck et al in 1947. I wonder where those Italians got this idea of shocking a patient. I guess they got it from reading Frankenstein(back then they didn't have Frankenstein movies yet).
