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A diagram showing the chain of survival. In ventricular tachycardia, the heart beats too fast to effectively pump blood. Ultimately, ventricular tachycardia leads to ventricular fibrillation. In ventricular fibrillation, the electrical activity of the heart becomes chaotic, preventing the ventricle from effectively pumping blood.

The fibrillation in the heart decreases over time, and will eventually reach asystole. The asystolic patient only has a chance of survival if, through a combination of CPR and cardiac stimulant drugs, one of the shockable rhythms can be established, which makes it imperative for CPR to be carried out prior to the arrival of a defibrillator. Effect of delayed treatment[ edit ] Uncorrected, these cardiac conditions ventricular tachycardia, ventricular fibrillation, asystole rapidly lead to irreversible brain damage and death, once cardiac arrest takes place.

However, sixth-grade students have been reported to begin defibrillation within 90 seconds, as opposed to a trained operator beginning within 67 seconds. Bras with a metal underwire and piercings on the torso must be removed before using the AED on someone to avoid interference. Of these 18, 11 survived. Of these 11 patients, 6 were treated by bystanders with absolutely no previous training in AED use.

Automated external defibrillators are generally either kept where health professionals and first responders can use them health facilities and ambulances as well as public access units which can be found in public places including corporate and government offices, shopping centres, restaurants, public transport, and any other location where people may congregate.

In order to make them highly visible, public access AEDs are often brightly coloured and are mounted in protective cases near the entrance of a building. When these protective cases are opened or the defibrillator is removed, some will sound a buzzer to alert nearby staff to their removal, though this does not necessarily summon emergency services; trained AED operators should know to phone for an ambulance when sending for or using an AED.

There has been some concern among medical professionals that these home users do not necessarily have appropriate training, [13] and many advocate the more widespread use of community responders, who can be appropriately trained and managed.

Some units need to be switched on in order to perform a self check; other models have a self check system built in with a visible indicator. All manufacturers mark their electrode pads with an expiration date, and it is important to ensure that the pads are in date. This is usually marked on the outside of the pads.

The AED manufacturer will specify how often the batteries should be replaced. Each AED has a different recommended maintenance schedule outlined in the user manual. To assist this, the vast majority of units have spoken prompts, and some may also have visual displays to instruct the user.

When turned on or opened, the AED will instruct the user to connect the electrodes pads to the patient.

Once the pads are attached, everyone should avoid touching the patient so as to avoid false readings by the unit. The pads allow the AED to examine the electrical output from the heart and determine if the patient is in a shockable rhythm either ventricular fibrillation or ventricular tachycardia.

If the device determines that a shock is warranted, it will use the battery to charge its internal capacitor in preparation to deliver the shock. The device system is not only safer - charging only when required, but also allows for a faster delivery of the electric current.

When charged, the device instructs the user to ensure no one is touching the patient and then to press a button to deliver the shock; human intervention is usually required to deliver the shock to the patient in order to avoid the possibility of accidental injury to another person which can result from a responder or bystander touching the patient at the time of the shock.

Depending on the manufacturer and particular model, after the shock is delivered most devices will analyze the patient and either instruct CPR to be performed, or prepare to administer another shock.

Some units also have voice recording abilities [16] to monitor the actions taken by the personnel in order to ascertain if these had any impact on the survival outcome. All this recorded data can be either downloaded to a computer or printed out so that the providing organisation or responsible body is able to see the effectiveness of both CPR and defibrillation.

Some AED units even provide feedback on the quality of the compressions provided by the rescuer. This caused increased cardiac injury and in some cases second and third-degree burns around the shock pad sites. Newer AEDs manufactured after late have tended to utilise biphasic algorithms which give two sequential lower-energy shocks of — joules, with each shock moving in an opposite polarity between the pads. This lower-energy waveform has proven more effective in clinical tests, as well as offering a reduced rate of complications and reduced recovery time.

Simplicity of use[ edit ] Usual placement of pads on chest Unlike regular defibrillators , an automated external defibrillator requires minimal training to use. It automatically diagnoses the heart rhythm and determines if a shock is needed. Semi-automatic models will tell the user that a shock is needed, but the user must tell the machine to do so, usually by pressing a button. In most circumstances, the user cannot override a "no shock" advisory by an AED.

If a particular model of AED is approved for pediatric use, all that is required is the use of more appropriate pads. Most units are designed for use by non-medical operators. Their ease of use has given rise to the notion of public access defibrillation PAD. When operated by non-dispatched lay first responders they have the highest likelihood of leading to survival. Technical malfunctions likely contributed to more than deaths in the 5-year period between and , in most cases by component failures or design errors.

During the same period, up to 70 types of AEDs were recalled, including recalls from every AED manufacturer in the world. The Henley Standard reported on 21 July that more than half the defibrillators in Henley-on-Thames and the surrounding area were at risk of failing, either because of low battery power or because adhesive pads had deteriorated.

In drills of pretend heart attack, the average time to bring the AED to the patient was 96 seconds, with a time that ranged from 52 to seconds. This met the three minute goal. In some cases, the use of the AED required the continuous presence of building personnel.

Future improvements include more obvious signage and public-access AEDs which do not require a staff member of the building to either retrieve or use the device.


Desfibrilador Externo Automático (DEA)






Desfibrilador Externo Automático (DEA)


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