While CPR is most associated with chest compressions and mouth-to-mouth procedures, people often forget that there is another major step in helping a victim of cardiac arrest: defibrillation.
In many forms of media, defibrillators are often inaccurately used to revive someone who is clinically dead. These devices are designed to restore the heart’s natural rhythm when it is thrown off.
Defibrillators can mean the difference between life and death. Mouth-to-mouth resuscitation is sometimes considered ineffective, and chest compressions alone are not enough to help a compromised heartbeat on its own
To maximize a patient’s chance of survival, you need something that can shock the heart and reset it back to a proper rhythm. This is where automated external defibrillators (AEDs) come in, and it is important to understand how these devices work before using them in an emergency.
If you have ever found yourself wondering how AEDs work, how many volts are in a defibrillator or what these devices do to the body, this comprehensive guide is here to answer all your questions.
What Is a Defibrillator?
Your heart is dependent upon a small amount of electricity that comes from your SA node, the natural pacemaker that sets and maintains your heartbeat. This electric current transmits the signals to your heart’s atria (upper chambers) to send oxygen-deprived blood to your lungs.
The blood becomes oxygenated in your lungs, and further electrical signals activate your heart’s ventricles (lower chambers), where the blood can be dispersed throughout the rest of your body. Once the oxygen has been distributed, the electrical signals start the process over again; this is how your heart maintains its natural rhythm.
However, certain health problems, risk factors and high-stress events can interrupt your heartbeat and cause the heart to pump irregularly (arrhythmia) or even to tremble instead of pump (fibrillation). In any event, both conditions can cause long-term damage and may even be lethal to a patient if they go untreated.
Fortunately, defibrillators are specifically designed to treat such heart problems. These machines deliver a controlled electric shock to the heart through the chest, which helps the heart restore a more stable rhythm.
There are two types of defibrillators: manual defibrillators and automated external defibrillators (AEDs). Both devices use the same method of controlled electric shock but administer it differently.
A defibrillator uses moderately high voltage (between 200 and 1,000 volts) to shock the heart, which essentially resets the SA node and forces it to resume its normal electrical activity. The voltage delivered to the patient depends on the presence of a heartbeat and how strong, fast, or slow it is.
Typically, the shock from an AED uses about as much electricity as it takes to power a 100-watt lamp for just a few seconds; this power actually weighs in at about 300 joules of electrical energy, much higher than the human body is used to.
AEDs have three major advantages for anyone who is unfamiliar with defibrillation: simple design, audio prompts and automatic cardio analysis. These devices come equipped with sticky pads that are attached to the patient’s chest, which detect the patient’s heart rate and analyze how much electricity will be needed for defibrillation.
Once the machine is ready, it will play a verbal audio prompt instructing you to push the ‘shock’ button, often a large, centralized, and clearly labeled button. After the shock has been delivered, the machine will reanalyze the patient and determine whether another shock is needed.
In between analyses and shock, you can perform chest compressions to help keep the patient’s heart going. AEDs are designed to be easily operated by anyone in an emergency, even people with no medical training, so the whole process is clearly outlined, and the machine’s audio prompts will guide you step by step.
Manual defibrillators are mostly used by professional responders and are more complicated. Instead of sticky pads that stay on the patient’s chest, these devices come with paddles that have a metal plating on one side and plastic handles with buttons on the other.
There are no audio prompts or automatic heartbeat analysis, and the machine has multiple dials and controls to change the level of shock manually. When responders decide it is necessary to shock a patient, they do so by pressing the paddles firmly against the patient’s chest and pushing the buttons in the handles. From here, the responder must reassess the patient to determine if another shock is needed.
When it comes to sudden cardiac arrest (SCA), CPR can be one of the most lifesaving maneuvers a responder can perform, but by itself, it is not enough. Chest compressions force the heart to pump manually as the responder presses on it, but the patient’s heart will not be able to pump on its own if the SA node is not reset.
Mouth-to-mouth is used less frequently anymore, as isn’t quite as effective as professionals once thought; the idea behind these rescue breaths is to fill the patient’s lungs with your own oxygen, forcing the person to breathe and re-oxygenate the blood.
However, most of the air you exhale is carbon dioxide, which does not enrich the patient’s blood at all. In fact, much of the air in rescue breaths passes through the esophagus and into the stomach, often causing the patient to bloat and even expel vomit or other waste.
Since the problem is electrical, manually pumping the heart and trying to breathe for the patient can help prolong their life but not save it.
By adding controlled shock to hands-only CPR, you can keep a patient alive with chest compressions and use electric shock until the heart regains a beat and can pump on its own. It may take several alterations of compressions and defibrillation, but these tactics together significantly increase a patient’s chance of survival.
What Should You Remember When Using an AED?
Whether you have had extensive training or have never touched one in your life, using an AED is simple when you know how. If you are in a position where you feel you need to use an AED on someone, keep these tips in mind:
Cardiac arrest, arrhythmia and fibrillation can all be frightening and intimidating conditions if you do not know what you are up against.
Fortunately, technology has come a long way in allowing bystanders to intervene and potentially save a life when cardiac arrest strikes. Remember that an AED will not deliver a shock unless it detects the need for one so you will not harm anybody with an unnecessary shock.
Defibrillation needs to be performed with CPR, for the best possible outcome, until help arrives. If the opportunity is available, consider becoming CPR certified or take an AED certification course to learn how to respond to common medical emergencies.