Community Heartbeat Trust

Uncorrected, these cardiac conditions (ventricular tachycardia, ventricular fibrillation, asystole) rapidly lead to irreversible brain damage and death. After approximately three to five minutes, irreversible brain/tissue damage may begin to occur. For every minute that a person in cardiac arrest goes without being successfully treated (by defibrillation & CPR), the chance of survival decreases by 23%.

Automated external defibrillators are generally either held by trained personnel who will attend events or are public access units which can be found in places including village halls, telephone boxes, pubs, corporate and government offices, shopping centres, airports, restaurants, casinos, hotels, sports stadiums, schools and universities, community centres, fitness centres, health clubs, workplaces and any other location where people may congregate.

The location of a public access AED should take into account where large groups of people gather, regardless of age or activity. Children, as well as adults, may fall victim to sudden cardiac arrest (SCA) although the incident rate in children is significantly lower, with those being most at risk usually identified with special requirements in place by local health facilities.

In many areas, emergency vehicles are likely to carry AEDs, with some ambulances carrying an AED in addition to manual defibrillators. Police or fire vehicles often carry an AED for first responder use. Some areas have dedicated community first responders, who are volunteers tasked with keeping an AED and taking it to any victims in their area. AEDs are also increasingly common on commercial airliners, cruise ships, and other transportation facilities.

High-rise buildings are densely populated but are more difficult to access by emergency crews facing heavy traffic and security barriers. It has been suggested that AEDs carried on elevators could save critical minutes for cardiac arrest victims, and reduce their deployment cost. 

In order to make them highly visible, public access AEDs often are 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. In September 2008, the International Liaison Committee on Resuscitation issued a ‘universal AED sign’ to be adopted throughout the world to indicate the presence of an AED. 

 A trend that is developing is the purchase of AEDs to be used in the home, particularly by those with known existing heart conditions. The number of devices in the community has grown as prices have fallen to affordable levels. There has been some concern among medical professionals that these home users do not necessarily have appropriate training, and many advocate the more widespread use of community responders, who can be appropriately trained and managed. However, due to the current level of technology of AED's a layperson cannot harm someone with an AED, to be precise it will not shock a person who does not need it.

An AED should have available an AED Rescue Kit, which will contain a face shield for providing a barrier between patient and first aider during rescue breathing; a pair of nitrile rubber gloves; a pair of trauma shears for cutting through a patient’s clothing to expose the chest; a small towel for wiping away any moisture on the chest, and a razor for shaving those with very hairy chests. 

An AED is external because the operator applies the electrode pads to the bare chest of the victim, as opposed to internal defibrillators, which have electrodes surgically implanted inside the body of a patient.

Automated refers to the unit’s ability to autonomously analyse the patient’s condition, and to assist this, the vast majority of units have spoken prompts, and some may also have visual displays to instruct the user.

When activated, 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. This system is not only safer (charging only when required), but also allows for a faster delivery of the electrical 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; although some AED's are fully automatic and do not require a button to be pressed, depending on the manufacturer and particular model, after the shock is delivered most devices will analyze the patient and either instruct CPR to be given, or administer another shock. Touching the patient during the delivery of a shock should be avoided.

Many AED units have an ‘event memory’ which store the ECG of the patient along with details of the time the unit was activated and the number and strength of any shocks delivered. Some units also have voice recording abilities 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.

The first commercially available AEDs were all of a monophasic type, which gave a high-energy shock, up to 360 to 400 joules depending on the model. This caused increased cardiac injury and in some cases second and third-degree burns around the shock pad sites. Newer AEDs (manufactured after late 2003) have tended to utilise biphasic algorithms which give two sequential lower-energy shocks of 120 – 200 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. 

Most manufacturers recommend checking the AED before every period of duty or on a regular basis for fixed units. CHT recommend checking AED's weekly as a minimum or more frequently if recommended by the manufacturer. 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 pads with an expiry date, and it is important to ensure that the pads are in date. This is usually marked on the outside of the pads. Some models are designed to make this date visible through a ‘window’, although others will require the opening of the case to find the date stamp.

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. Automatic models will administer the shock without the user’s command. 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. Some AEDs may be used on children – those under 55 lbs (25 kg) in weight or under age 8. If a particular model of AED is approved for pediatric use, all that is required is the use of more appropriate pads. Some organizations, such as the Resuscitation Council (UK), recommend that if pediatric AED pads are not available, adult pads should be used to determine if the child is in a shockable rhythm. There is insufficient evidence to suggest that a child, in a shockable cardiac arrest, can be "hurt" by an adult defibrillation energy setting.

All AEDs use an electronic voice to prompt users through each step. Because the user of an AED may be hearing impaired, many AEDs now include visual prompts as well. 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), which experts agree has the potential to be the single greatest advance in the treatment of out-of-hospital cardiac arrest since the invention of CPR.

CHT pioneered the concept of Community Public Access Defibrillators (CPAD) in the UK.

Automated external defibrillators are now easy enough to use that most countries include the "good faith" use of an AED by any person under the Good Samaritan laws. "Good faith" protection under a Good Samaritan law means that a volunteer responder (not acting as a part of one’s occupation) cannot be held civilly liable for the harm or death of a victim by providing improper or inadequate care, given that the harm or death was not intentional and the responder was acting within the limits of their training and in good faith. AEDs create little liability if used correctly, in the UK the SARAH Act 2015 applies.

In general, during a rescue carried out under the guidance of an ambulance service, the service will accept clinical liability for trained users and those acting under a trained user as defined by the NHS third-party liability scheme.