Why Defibrillator Voltage is Important

Defibrillators, commonly referred to as automated external defibrillators (AED), are lifesaving medical devices designed to restore normal heart rhythm when patients experience sudden cardiac arrest. During sudden cardiac arrest, electrical activity becomes disrupted causing the heart to quiver instead of contract rhythmically. This denies vital organs oxygen-rich blood increasing the chances for brain damage and eventual fatality if immediate intervention is not given. Defibrillators play an essential part in treating life-threatening conditions by administering an electric shock to the heart, in an attempt to reset its electrical system and enable regular heartbeat restoration. Their success depends on many factors; among these being voltage - an appropriate level being critical in defibrillation's success and increasing chances of normal rhythm restoration.

What is Defibrillation?

Defibrillation involves delivering an electrical shock to the heart to try to restore a normal heart rhythm. During a cardiac arrest, electrical activity in the heart is disrupted. This causes the heart to tremble instead of contracting normally. This condition, also known as ventricular fibrillation or pulseless ventricular Tachycardia (VT), prevents blood flow to vital organs. By shocking the heart's electrical system, AEDs can reset the heart rhythm, which could save a life.

What is Defibrillator Voltage?

The amount of energy delivered by a defibrillator is called the voltage. The energy used by AEDs is measured in joules (J) and varies depending on the patient's size. Typically, adults need higher shock energies than kids due to physiological differences. AEDs measure energy in joules. The joule unit of electrical power can be described using the formula below.

Joules (Energy) = Voltage X Current X Time

How Many Volts Does an AED Deliver?

AEDs can deliver 120 to 360 joules. Automated External Defibrillators (AEDs) can deliver electrical energy levels ranging from 120 to 360 joules. Most AEDs administer initial shocks within the optimal voltage range of 120-200 joules for most adult patients experiencing sudden cardiac arrest. However, if that initial shock fails to restore normal heart rhythm, further shocks may need to be delivered at higher energy levels. This can reach up to 360 joules for effective defibrillation.

How Does the AED Decide How Many Volts to Deliver? 

AEDs determine the appropriate voltage level necessary to deliver an electric shock based on factors like heart rhythm, age, size, and other considerations. Their algorithms are specifically designed to calculate what voltage level will provide effective shock therapy while minimizing their users' injury risk. AED software utilizes electrodes attached to a patient's chest in order for heart rhythms to calculate the energy required to restore regular electrical activity. Most AED devices typically have pre-set energy levels for adults and children, depending on the model. If pediatric or child mode is activated, the device will automatically reduce the voltage level to one more appropriate for a child. If the AED determines defibrillation will not effectively treat a patient's heart rhythm, it may advise against giving shocks. Instead, it instructs the user to perform CPR and call emergency medical services immediately.

Why is the Voltage of a Defibrillator Important?

Voltage plays an essential part in defibrillation as it directly influences how much energy is delivered during shocks. A higher voltage means more energy being transmitted to the heart, increasing the chances of successful defibrillation. Harnessing higher voltage levels allows defibrillators to deliver the necessary electrical stimulus necessary to restore normal heart rhythm. 

Factors Affecting Defibrillator Voltage

The effectiveness of a defibrillator can be affected by several factors, such as the size of the person, the location of the pads, and the impedance in the chest. Here are a few factors that can impact the level of defibrillator voltage. 

Patient Size: The amount of energy needed for an electric shock depends on the patient's size and weight. A person who is larger will require a more powerful shock. However, a child or a smaller adult may need a shock with a lower level of energy. The majority of AEDs have pre-set energy settings for both adults and children.

Pad Placement: The placement of the pads is critical to delivering a shock that works. Correctly place the pads on the upper left and lower right sides of the chest. Positioning the pads correctly ensures the electrical current is passed through the heart muscle. The shock could be ineffective if the pads aren't placed correctly.

Impedance: Impedance is the resistance of the chest against an electrical current. The chest impedance varies based on several factors, including age, gender, and body composition. The impedance can influence the amount of energy delivered to the heart when defibrillating. The more impedance there is, the higher the energy required to deliver a shock.

The amount of energy delivered to the heart determines the effectiveness of the shock. If the voltage is too low, the shock could be too weak to restart electrical activity in the heart. If the voltage is high enough, it may cause heart muscle damage or burns. The heart's electrical system is resistant to lower voltages. Because the heart's electrical system is resistant, defibrillators deliver high-voltage shocks to the heart. 

Defibrillator voltage is a crucial factor in delivering an effective shock to the heart during sudden cardiac arrest. AEDs come with different energy levels suitable for adults and children, and the energy level can be adjusted depending on the patient's size. Proper pad placement is crucial in delivering an effective shock, and the impedance of the chest can affect the amount of energy that reaches the heart during defibrillation. Defibrillation is an essential medical intervention used to restore normal heart rhythm during cardiac arrest, and the voltage of the defibrillator shock plays an integral part in its success.