The semi-automatic external defibrillator (AED) is a portable electronic device that diagnoses and treats cardiorespiratory arrest when it is due to ventricular fibrillation (in which the heart has electrical activity but without mechanical effectiveness) or pulseless ventricular tachycardia (in which there is activity electrical and in this case the blood pump is ineffective), reestablishing an effective heart rhythm electrically and mechanically.
Defibrillation consists of emitting a direct current impulse to the heart, simultaneously depolarizing all myocardial cells, allowing them to resume their normal or other effective electrical rhythm. Ventricular fibrillation is the most common cause of sudden death.
The AED is very effective for most of the so-called cardiac arrests, which are mostly due to the heart fibrillating and its rhythm not being adequate. These devices basically return the proper rhythm to the heart, but it is totally ineffective in cardiac arrest with asystole since the heart, in this case, in addition to not pumping blood, has no electrical activity; and in pulseless electrical activity (PEA), previously called electromechanical dissociation, where there is electrical activity, which may even be normal, but without mechanical efficiency. In these last two cases, only chest compression should be performed while other advanced measures are established.
Make sure the rescuer, victim, and any witnesses are safe. Follow the adult BLS sequence:
-If the victim does not respond and is not breathing normally, send someone to get help and, if found, look for and bring an AED.
-Start the AED and apply the patches to the patient’s bare chest. If there is more than one rescuer, CPR maneuvers have to be done while applying the patches.
-Follow the AED instructions immediately.
-Ensure that no one approaches or touches the victim while the AED performs the rhythm analysis.
If shock is indicated: ensure that no one touches the victim. Press the download button. Immediately restart 30:2 CPR. Continue as directed in the instructions.
If shock is not indicated: restart CPR immediately, performing 30 chest compressions and 2 breaths. Continue as directed by the visual/sound instructions.
Follow the AED instructions until : another rescuer arrives to take over. The victim wakes up: moves, opens his eyes and breathes normally. The rescuer is tired and there is another person who can replace him or her immediately.