How Does a Defibrillator Work?
Using a defibrillator to help the heart restart is the only way to save someone in cardiac arrest. The more people use defibrillators outside of a hospital the better the chance for survival from cardiac arrest.
In January 2020, London Ambulance Services found that 10.8% of people now survive when cardiac arrest strikes out of hospital, more than double the statistic from a decade ago. This is largely thanks to an increase in public access AEDs and bystanders stepping in to offer life-saving assistance.
Automatic External Defibrillators (AEDs) are designed to be straightforward and easy to use so that any member of the public can help someone in cardiac arrest before medical personnel arrive. But due to less training and understanding, many people are hesitant to use an AED.
A useful step in feeling comfortable using an AED is to understand exactly how it works and what it does. Find out in this article.
What is it like using an AED?
When imagining an AED in action, many people will think of scenes from films in which a paramedic holding two paddles shouts ‘clear!’ When the person’s body is shocked it jolts dramatically up into the air.
The AEDs that members of the public have access to (and indeed those used by paramedics today) are much less intimidating. They are small, lightweight, and come with very simple instructions. Instead of paddles, two sticky back pads are used meaning all you need to do is attach them in the right places.
Depending on the type of defibrillator you will have minimal involvement in delivering the shocks. A semi-automatic defibrillator will require you to press a button to deliver a shock. A fully automatic defibrillator will administer the shock on its own.
An AED like the iPAD SP1 Semi-Automatic Defibrillator offers the user as much support as possible. It will inform the users when the pads are in the correct position and delivers a shock only when it is determined necessary, the user only needs to press a button to deploy the shock. The device comes with audible instructions to follow and can be switched from adult mode to child mode.
What does a defibrillator do?
Cardiac arrest occurs when the electrical rhythm in a person’s heart causes it to stop beating at a normal rhythm. This results in an irregular beat called arrhythmia which prevents the heart from moving oxygenated blood around the body properly.
When blood flow to the brain and other vital organs are stopped the person will suddenly collapse and become unresponsive. You won’t be able to feel their pulse or detect breathing. A person in cardiac arrest will have minutes to survive and using a defibrillator is the only way to help them recover and get their heart beating at a normal rhythm (sinus rhythm) again.
A defibrillator works by de-polarising the cardiac muscle with a short electrical shock. This allows the cells in the heart to recharge at the same time, reestablishing the sinus rhythm in the process.
Does a defibrillator restart the heart?
Due to depictions in films and TV, many people wonder ‘are defibrillators used to start the heart?’ A defibrillator is not designed to restart a heart that has fully stopped. When in cardiac arrest, the heart is not ‘lifeless’, rather it is stuck at an irregular beat, unable to correct itself. A defibrillator fixes this by shocking the heart’s rhythm back to normal.
Does a defibrillator stop the heart?
A defibrillator doesn’t need to stop the heart to get it working normally again. Rather it sends an electrical pulse through the heart that causes all individual cells in the heart to start up again in synchronicity, similar to rebooting a computer.
How many volts does a defibrillator put out?
Knowing that the device delivers a shock that is potentially dangerous to those around the patient, many people wonder ‘how many volts does a defibrillator give?’ An AED is capable of delivering a charge of 3,000 volts in a fraction of a second.
What is a defibrillator used for?
There are three different types of defibrillators, but defibrillator use is always the same: to detect arrhythmias and send a shock to the heart when necessary to reestablish the sinus rhythm. The three different types of defibrillators are Automated External Defibrillators, Implantable Cardioverter Defibrillators, and Wearable Cardioverter Defibrillators.
The only difference between AED and a defibrillator is that one is worn on the outside or inside of the body to monitor for arrhythmia all the time, and the other is available to the public to use in an emergency situation.
Defibrillator Types and Uses
Automatic External Defibrillator (AED)
An AED is a defibrillator you need to be aware of if you want to help someone in cardiac arrest. Workplace defibrillators and public access defibrillators are becoming more commonplace so that anyone can receive medical attention as soon as possible to increase the chance of survival from cardiac arrest.
Finding a public access AED will be easy if you know what you’re looking for. An AED comes in a small box and is usually installed on an AED wall bracket or in a wall-mounted AED cabinet. There may be a sign on it or near it in green and white, or in red that says ‘AED’, ‘cPAD’, or ‘defibrillator’.
In the box, you will find two, adhesive pads and a machine. The machine will come with instructions, and may even have audible instructions to follow, like the iPAD SP1. There may also be a towel and razor to dry the skin and remove hair if needed before attaching the pads.
Implantable Cardioverter Defibrillator (ICD)
An ICD is a type of internal defibrillator that is inserted into a person’s chest so their heartbeat can be continuously monitored for arrhythmias. When an irregular rhythm is detected, the ICD can immediately deploy a shock to restore a normal heartbeat.
Certain conditions require the implanting of an ICD such as having an abnormally large heart, a weak heart, a history of coronary artery disease, or a genetic heart condition.
A traditional ICD is implanted in the upper chest, with wires that extend within the heart and which is put in via invasive surgery. You could also have a subcutaneous ICD which is implanted under the skin below the armpit, with a wire that travels along the breastbone.
Wearable Cardioverter Defibrillator (WCD)
Also called a life vest, a WCD is a wearable device that provides similar support to an ICD. A WCD can be worn by someone who is at risk of arrhythmia to deliver a shock to the heart as soon as it’s needed.
Oftentimes while survivors of heart attacks wait for an ICD to be implanted to support their heart, they are at risk of further arrhythmias. The WCD offers an excellent way to protect the person by continuously monitoring their heart rate and delivering a shock when needed, preventing them from going into cardiac arrest again.
WCDs are also used by patients who might be at higher risk of cardiac arrest for a temporary amount of time, where implanting an ICD would be unnecessary.
Manual Defibrillator vs AED
The difference between a manual and automatic external defibrillator is the control that the user has in the level of intensity of the shock delivered. Manual defibrillators are used by professionals who have been trained to deliver defibrillation. Automatic defibrillators are designed to be used by anyone including those who’ve ever used a defibrillator before.
Both types of defibrillators do exactly the same thing: deliver a shock to the heart when a person is in cardiac arrest. Everything about the way an AED is made is to help an untrained person give medical assistance. The device will do the following:
- Provide step by step instructions.
- Come with adhesive pads so that no one needs to be near the patient when a shock is delivered.
- Automatically detect whether the pads are in the correct position.
- Deliver a shock only when it has determined it necessary.
A manual defibrillator has more capabilities than an AED. Designed for use by paramedics, doctors, and other medical personnel, a manual defibrillator can be used to identify specific problems with the heart and treat those problems. The user will be able to adjust the level of energy delivered in a shock too.
When emergency services arrive on the scene of a cardiac arrest, the AED (if there is one being used) will be able to deliver a report on the shocks already delivered. The response team might then switch over to using a manual defib.
Fully Automatic vs Semi-Automatic Defibrillator
A fully automatic and semi-automatic defibrillator are quite similar, the only difference is that user input is needed for a semi-automatic defibrillator to work.
A semi-automatic defibrillator will give out instructions once it is opened and turned on. Once the pads have adhered to the person’s chest in the correct placement, the AED will analyse the heartbeat. If a shock is needed, the AED will tell the user to push the shock button once everyone is standing well clear of the patient.
A fully automatic defibrillator will analyse the heartbeat and then inform the user whether a shock will be delivered. The fully automatic defibrillator will ask for everyone around to stand clear before announcing that a shock will be delivered. The user does not have to press any buttons for the shock to be delivered.
How Does a Defibrillator Work?
A useful step in feeling comfortable using an AED is to understand exactly how it works and what it does. Find out in this video.
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