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What is a Defibrillator, Different Types & How to Use One

With an estimated 25,000 cases occurring out-of-hospital each year, sudden cardiac arrest (SCA) presents as one of the most prevalent health risks facing Australians today. However, it is possible to significantly increase cardiac arrest patients’ chance of survival through the immediate delivery of CPR (cardiopulmonary resuscitation) and defibrillation as part of the chain of survival [include link]. Early defibrillation is often considered to be the most important measure as it is the only way to restore the patient’s normal heart rhythm. In this blog, we take an in-depth look at the function and varieties of defibrillators, as well as how they relate to the workplace.  

 

Cardiac Arrest vs Heart Attack

It’s important to note that cardiac arrest is not the same as a heart attack. Heart attack refers to a blockage of blood flow to the heart. Often a heart attack is caused by a build-up of fat, cholesterol or other substances in one of the heart’s coronary arteries. This blockage reduces the supply of oxygenated blood to the heart which can lead to damage of the heart muscle and even death. Generally, a heart attack will cause the patient to feel a tightness or pain in the chest, back, neck or arms.  

On the other hand, cardiac arrest is an electrical problem with the heart that causes it to stop pumping blood around the body. Cardiac arrest can be caused by a heart attack that has caused the heart to take on an irregular rhythm (commonly ventricular fibrillation or pulseless ventricular tachycardia). Unlike a heart attack where the patient will generally be alert and breathing, cardiac arrest victims will be unresponsive and not breathing properly. CPR should be administered immediately and continued until an Automated External Defibrillator is applied.

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What Is a Defibrillator?

A defibrillator is a compact medical device that is used to deliver a shock to the heart to restore its normal rhythm in the event of cardiac arrest. There are three common types of defibrillators that can be distinguished by their design, functionality and usability with regard to public access use, surgical implantation and wearability.

 

Types of Defibrillators

AED: Automated External Defibrillator

Equipped with an in-built computer, Automated External Defibrillators (AEDs) automate much of the defibrillation process. Rescuers need only recognise that cardiac arrest may have occurred and attach two adhesive electrode pads to the patient’s chest following CPR.

The AED electrodes serve to analyse the heart’s activity to determine if there is a shockable (irregular) rhythm, otherwise known as anarrhythmia. AEDs are completely safe for use by untrained bystanders as the device’s shocking capability will only be unlocked if a shockable rhythm is detected. Instructions for use are provided via simple voice prompts with semi-automated models requiring the operator to press a button to administer a shock, while fully-automated models can deliver a shock without external manipulation.

Once a shock has been delivered, the AED will analyse the patient’s heart again to determine if the arrhythmia has been corrected, providing further instruction for CPR and subsequent shocks as required.

For every minute that defibrillation is delayed, there is approximately a 10% reduction in the chance of survival for patients experiencing cardiac arrest, specifically ventricular fibrillation. Research has also shown that patients who received an AED shock from a bystander were 2.62 times more likely to survive to hospital discharge than those who only received an AED shock after emergency services arrived.

ICD: Implantable Cardioverter-Defibrillator

An implantable cardioverter-defibrillator (ICD) is a small battery-powered device that is implanted directly into the patient’s chest to detect and prevent irregular heart rhythms. Implantable cardioverter defibrillators work by continuously monitoring the patient’s heartbeat and delivering an electric shock, when required, to restore a regular rhythm. 

ICDs are commonly provided to people who have survived a cardiac arrest, have sustained ventricular tachycardia or are otherwise at high risk of arrhythmia (e.g., ventricular fibrillation) and sudden death.

Like AEDs, ICDs come in two forms: 

  • Traditional ICD, where the device is implanted within the patient’s chest, with the leads attaching to the heart.
  • Subcutaneous ICD (S-ICD), where the device is implanted under the skin below the armpit with an electrode running along the sternum. This is generally considered to be the less invasive option.

WCD: Wearable Cardioverter-Defibrillator

A wearable cardioverter-defibrillator (WCD) is a non-invasive type of defibrillator that is built into a wearable vest that can be worn under the patient’s clothing. The garment which is anchored to the patient’s upper chest is connected to a monitor that is worn around the waist or from a shoulder strap. Similar to ICDs, WCDs continuously monitor the patient’s heartbeat and deliver an electrical shock if an abnormal rhythm is detected, without patient or bystander intervention. 

WCDs are typically used by people who are at a heightened risk of developing an irregular heart rhythm, specifically ventricular tachyarrhythmia.

 

How Do Public Access AEDs Work?

Designed to offer immediate medical intervention in the event of sudden cardiac arrest, public access AEDs are built to be easily accessible and operable by untrained bystanders. With fully automatic and semi-automatic models available, AEDs provide users with voice prompts to guide them through the defibrillation process, step by step.  

  • AEDs require the user to apply two electrode pads to the patient’s exposed torso with one pad placed slightly below the collarbone on the right side of the chest and the other placed below the armpit on the left side. The AED pads  then analyse the electrical signals coming from the patient’s heart.
  • If the device detects  a shockable rhythm it will advise that a shock is required. 
  • Depending on whether the AED is fully- or semi-automated, it will either prompt the user to press a button to deliver an electric shock, or count down and administer the shock automatically. A voice prompt will also instruct the operator to stand clear of the patient while the shock is being delivered.
  • This electrical shock is intended to reset electrical activity within their heart, thereby restoring the heart’s normal rhythm.
  • Following the initial shock the AED will instruct the rescuer to continue performing CPR for a further 2 minutes before analysing the patient’s heart rhythm again. 
  • The device will continue to instruct the rescuer to perform additional shocks and CPR for as long as it detects a shockable rhythm. These instructions should be followed until emergency services arrive.  
  • Alternatively, the AED will advise the rescuer to refrain from administering further shocks if the heart rhythm has been restored or if the patient has flatlined. It is a common misconception that defibrillation can be performed on someone who has flatlined since this is not a shockable heart rhythm. Instead, CPR should be administered to try and return the patient’s heart into a shockable rhythm.

 

When to Use an AED

As the third link in the chain of survival, AED defibrillation should only be administered on an unresponsive patient following the delivery of CPR. It is important that CPR continues until the AED is turned on and the pads are correctly attached to the patient (on an axis through the heart). Though CPR is an integral link in the chain of survival for cardiac arrest?keeping blood flowing artificially and producing a shockable rhythm?a shock from a defibrillator is the only way to restore the patient’s heart back into its normal rhythm. 

 

Where Should AEDs be Placed?

Defibrillators are often found in public places so that they are readily available in case of a cardiac-related emergency. With many people having out-of-hospital cardiac events every year, it’s important to provide members of the public with an easy-to-use medical device that has been proven to increase one’s chance of survival. You will commonly find them in places such as:

  • Train stations
  • Gyms
  • Airports
  • Shopping centers
  • Workplaces

The general rule is to have AEDs located in a central location—generally on a wall—where it can be easily identified by anyone in need of using the device. Furthermore, AEDs should always be located within 90 seconds of a brisk walk, capable of being accessed by people of all heights.

 

Workplace AED Placement

While there is no mandate for Australian workplaces to have a defibrillator on premises, the Safe Work Australia Code of Practice still encourages it as good practice for businesses and industries. Ultimately though, the use of Automated External Defibrillators is at the discretion of individual workplaces.

 

Keeping AEDs in the Workplace

With over 25,000 cardiac arrests occurring every year across Australia, the benefit to keeping a defibrillator in the workplace couldn’t be clearer. Like first aid kits, AEDs are a valuable provision that can go a long way in improving the safety and survival of both employees and customers in the event of a medical emergency.

 

However, to ensure that AEDs can be deployed effectively in workplace settings, it is imperative that businesses and industries initiate the following measures:

Placement

As with public areas, workplace AEDs should be kept in a central location with clear signage to enhance visibility so that they can be easily identified in an emergency cardiac situation. AEDs should also be placed in easily accessible locations where they can be readily retrieved by any employee or member of the public.  

 

For high-risk workplaces where employees are exposed to hazardous environments and activities (e.g. chemical and mechanical work), it’s important to place AEDs in or near these high-risk locations to allow for quick and easy access.

Set Up

When you first purchase an AED for your workplace, you may be required to carry out some simple preliminary steps to ensure the device is operational and ready for use. This often includes installing the pads and battery within the device as well as ensuring the status indicator on the front of the device is flashing green (depending on the make/model). It’s important that this set-up be conducted upon installation since this will save valuable time in the event of an emergency.

Training

While training is not necessarily required in order to operate an AED, it is highly recommended that employees, employers and other potential users of workplace AEDs undertake first aid training along with subsequent refresher courses. 

Maintenance

Though AEDs perform regular self-tests to ensure continued usability and functionality, workplaces will often still need to administer routine maintenance in the form of simple checks, such as:

  • Inspecting the device for any signs of wear or damage  
  • Reviewing expiry dates of particular components
  • Ensuring the Status Indicator is functioning normally

 

AERO Healthcare AEDs

If you’re looking to improve the safety of your workplace, we offer a range of high-quality Public Access AEDs, trainer defibrillators, storage cabinets and accessories. Put the safety of your employees and customers first with AERO Healthcare.

 

References: 

https://newsroom.heart.org/news/cardiac-arrest-survival-greatly-increases-when-bystanders-use-an-automated-external-defibrillator

https://resus.org.au/download/anzcor-guideline-7-automated-external-defibrillation-in-basic-life-support-april-2021-0-3-mib/?wpdmdl=13730&masterkey

https://www.atsjournals.org/doi/full/10.34197/ats-scholar.2021-0084VO

https://www.mja.com.au/journal/2021/215/5/cardiac-arrests-general-practice-clinics-or-witnessed-emergency-medical-services

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC274065/