AEDs and Sudden Cardiac Arrest

Sudden Cardiac Arrest is the abrupt cessation of normal circulation of the blood due to failure of the heart to contract effectively. A cardiac arrest is different from (but may be caused by) a heart attack or myocardial infarction, where blood flow to the still-beating heart is interrupted.

"Arrested" blood circulation prevents delivery of oxygen to all parts of the body. Cerebral hypoxia, or lack of oxygen supply to the brain, causes victims to lose consciousness and to stop normal breathing, although intermittent and irregular breathing may still occur. Brain injury is likely if cardiac arrest is untreated for more than 5 minutes although new treatments have begun to extend this time. To improve survival and neurological recovery immediate response is paramount.

Cardiac arrest is a medical emergency that, in certain groups of patients, is potentially reversible if treated early enough.  When unexpected cardiac arrest leads to death this is called sudden cardiac death (SCD). The primary first-aid treatment for cardiac arrest is cardiopulmonary resuscitation (commonly known as CPR) to provide circulatory support until availability of definitive medical treatment, which will vary dependant on the rhythm the heart is exhibiting, but often requires defibrillation.

An Automated External Defibrillator or AED is a portable electronic device that automatically diagnoses the potentially life threatening cardiac arrhythmias of ventricular fibrillation and ventricular tachycardia in a patient, and is able to treat them through defibrillation, the application of electrical therapy which stops the arrhythmia, allowing the heart to re-establish an effective rhythm.

AEDs are designed to be simple to use for the layman, and the use of AEDs is taught in many first aid, first responder and basic life support (BLS) level CPR classes.

An automated external defibrillator is used in cases of life threatening cardiac arrhythmias which have led, to cardiac arrest. The rhythms the device will treat are usually limited to Ventricular Fibrillation or Pulse-less Ventricular tachycardia

In each of the two types of shock-able cardiac arrhythmia, the heart is in activity, yet in an unusual pattern which can be life-threatening if left uncorrected. In ventricular fibrillation, the electrical activity of the heart becomes chaotic, preventing the ventricle from effectively pumping blood. In ventricular tachycardia, the heart beats too fast to effectively pump blood. Ultimately, ventricular tachycardia leads to ventricular fibrillation. The fibrillation in the heart decreases over time, and will eventually reach asystole.

AEDs are designed to be used by laypersons who ideally should have received AED training. This is in contrast to more sophisticated manual and semi-automatic defibrillators used by health professionals, which can act as a pacemaker if the heart rate is too slow (bradycardia) and perform other functions which require a skilled operator able to read electrocardiograms.

 

This article is licensed under the GNU Free Documentation License

It uses material from the Wikipedia article "Metasyntactic variable"

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