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Defibrillator Paddles: What They Are and How to Use Them

Sudden cardiac arrest (SCA) is a life-threatening condition that can be caused by a heart attack, electric shock, drowning, or drug overdose. SCA patient’s heart rhythms will become irregular and they will collapse without warning. If an automated external defibrillator (AED) is not used for defibrillation and resuscitation by the immediate use of an AED to restore the heart rhythm within minutes, along with the use of cardiopulmonary resuscitation (CPR), death usually occurs.

This blog article outlines information about what defibrillators are, why defibrillator pads are still referred to as a “paddle” and how they work to save the life of a sudden cardiac arrest patient along with CPR for laymen responders as well as emergency medicine and healthcare providers.

Sudden Cardiac Arrest

Sudden Cardiac Arrest (SCA) is a medical emergency that occurs when the heart rhythms suddenly stop beating effectively. Most cardiac arrests take place out in public away from hospitals and cardiac arrests are usually caused by an electrical malfunction in the heart, which causes the heart to beat erratically or stop completely. This is asystole which is defined as the absence of all electrical activity in the heart. SCA is a leading cause of death and has no warning signs or symptoms. AEDs can restart the normal heart rhythm of the SCA patient. If they are not used for resuscitation to restore the heart rhythm within minutes, along with administering immediate CPR, death usually occurs.

Sudden Cardiac Arrest

The rate of survival care is tracked for all sudden cardiac arrests for what is called out of hospital cardiac emergencies. These statistics give us a window into how well AEDs are impacting the survival of cardiac arrest victims out of hospital cardiac centers. Hospitals obviously will have state-of-the-art lifesaving AEDs and expert caregivers. The out-of-hospital numbers give us a great idea of how well individuals, businesses, and public access AED users are saving lives.

Cardiopulmonary Resuscitation (CPR)

CPR is a life-saving technique that is used to resuscitate an individual who has suffered a cardiac arrest and is in need of emergency services. CPR provides oxygenated blood flow by manually compressing the chest between 100 to 120 compressions per minute and also allowing for defibrillation which can be administered via defibrillator paddles placed on either side of the bare, dry chest of the patient. This important care is a critical piece to the chain of survival for a cardiac arrest victim.

Why Are AED Electrodes Called paddles?

The history of defibrillators and the use of the term paddles go back to the 19 century and has been an extremely important part of medical treatment for patients of sudden cardiac arrest.

Technology today with AEDs and their amazing lifesaving features have improved exponentially over the last 20 years with smarter and more powerful devices being produced in a very small and portable footprint. The modern automated external defibrillator (AED) machine has dramatically improved the success rates of resuscitation from cardiac arrest through defibrillation when used in conjunction with administering CPR by rescuers and health professionals.

Why Are AED Electrodes Called paddles?

These amazing lifesaving devices have electrodes (often referred to as paddles) that attach to the defibrillator machine and deliver a shock dose of electricity that restores normal heart rhythm by stopping the chaotic electrical activity in the heart.

In the early 1900s defibrillator electrodes were referred to as “paddles” by doctors because they had two large paddles which would be held against the patient’s open heart during surgery or later with the invention of the automated external defibrillator (AED), against the external skin of the cardiac arrest victim. It was not until much later that the defibrillation paddles became small and portable enough to be applied to the skin of SCA patients and appropriately referred to now as electrodes.

Defibrillators or AEDs

Both a reference to defibrillators and AEDs are typically referring to the same type of machine. The addition of the word external to Automated External Defibrillator references that these devices are to be used on the outside of the body to apply a shock of electricity.

ECG versus EKG

The difference between ECG and EKG is extremely important to understand when defibrillating the heart muscle of a patient of sudden cardiac arrest. ECG is an abbreviation for the term electrocardiogram which measures electrical activity in the heart. An EKG on the other hand uses electrodes placed all over the body to measure brain wave activity, nerve signals, and muscle contractions along with monitoring skin changes that can be used as part of defibrillation via defibrillator pads.

Sinus Rhythm

The sinus node is the area of the atrioventricular (AV) node that begins to depolarize the muscle. The presence of properly positioned P waves on the electrocardiogram is an indicator that this form of heart rhythm is present. Sinus rhythm is required, but it isn’t sufficient, for normal electrical activity in the heart.

Why do Electrodes Expire?

Modern AED electrodes are made with an adhesive on gel pads for all AEDs is limited because the adhesive gel pads that attach them to the cardiac arrest patient lose their ability to stick and conduct electricity to the patient over time, not due to usage.

Most AEDs today have an accessories life from two years to five years depending on the brand and model of AED. At AED USA we offer our FREE AED management solution as well as our paid AEDMD Plus AED Management program.

Why do Electrodes Expire?

Electrode pads are a disposable part of defibrillator equipment. They can only be used once and it is important to make sure you change them if used for shock delivery defibrillation, in order for your defibrillator to remain ready for use.

You should check the expiration date on electrodes before using them, as expired defibrillation electrodes may not work properly or at all when applied to an SCA patient’s chest.

Electrodes expire because they are made with an adhesive gel that both stick the pads to the skin of the patient and also conducts electricity through to the body when a shock is applied.

Impedance with a Cardiac Arrest Patient

Impedance is defined as a measure of the opposition a circuit presents to alternating current. This is important when defibrillating an SCA patient because it can be helpful in finding out what may have caused their cardiac arrest and why they are not responding to defibrillation with shock. Impedance testing is done by applying defibrillation pads to one or more locations on the patient’s chest while recording ECG waveforms that help identify heart rhythm abnormalities like atrial fibrillation, premature ventricular complexes, etc.

What you will notice about impedance testing for defibrillation vs regular EKG leads placed all over your body is that there must be skin contact between the electrodes and skin surface if accurate readings are to be generated.

It is worth noting the technology with some newer pads allows for the AED to estimate impedance and therefore better align the joules for a shock with an algorithm instead of relying on special pads with sensors.

What Is Defibrillation?

When the heart’s electrical system goes into cardiac arrest, it is most frequently in a ventricular fibrillation (v-fib) rhythm. Ventricular fibrillation is a heart rhythm disorder in which the ventricles of the heart quiver rather than beating properly. It’s caused by chaotic electrical activity in the heart. Ventricular fibrillation causes cardiac arrest with loss of consciousness and no pulse. The resuscitation process for this problem is to give the heart a large dose of energy in order to overpower fibrillation and, hopefully, allow regular pacemaker cells in the heart to restart and begin rhythmic and organized muscle contraction.

What Is Defibrillation?

Defibrillation is the medical treatment in which an electric shock current by an AED is passed through electrodes placed on either side of the chest and causes all of the heart’s muscles to contract at the same time, thereby defibrillating it.

Fibrillations are associated with ventricular fibrillation and pulseless ventricular tachycardia, but not always. Both of these patterns cause the cardiac muscle to lose its ability to function correctly and obstruct myocardial perfusion and blood flow throughout the body.

In fibrillation, the chaotic rhythm has no regular polarization or depolarization pattern. The goal is for the shock energy to enter the right atrium (near the sinoatrial node), pass through the chest wall, and reach the lower right corner of the left ventricle via normal conduction pathways after it has been delivered to a patient.

All of the cardiac cells depolarize at once as a result of this large delivery of energy. The heart’s functional electrical system may reset and begin firing with one pacemaker site after the cells and heart have recovered, resulting in an organized EKG rhythm.

American Heart Association (AHA) Changed Guidelines

In 2005, the American Heart Association (AHA) revised its guidelines for defibrillation with AEDs & CPR. In the past, a person experiencing cardiac arrest and ventricular fibrillation or pulseless ventricular tachycardia (V-tach) was immediately defibrillated. If the rhythm did not change after three total defibrillations, CPR was started.

Following the additional study, the employment of three “stacked shocks” has been discontinued in favor of more successful cardiopulmonary resuscitation (CPR). The Advanced Cardiac Life Support course teaches two distinct procedures:

  1. If a witnessed cardiac arrest is detected with ventricular fibrillation or pulseless ventricular tachycardia on the monitor, personnel should immediately use an AED to defibrillate one time and then begin CPR.
  2. In the event of an unwitnessed cardiac arrest, staff should start CPR for five cycles, check an EKG rhythm, defibrillate using AEDs if V-fib or pulseless V-tach is on the monitor, and then resume CPR.

What is the explanation for the shift? In fact, basic CPR alone is unlikely to cure v-fib, according to the AHA. In most situations, defibrillation is required for effective resuscitation along with immediate CPR. Furthermore, survival rates drop 7%–10% for each minute that goes by between collapse and defibrillation without basic CPR. When done by bystanders, the survival rate drops by 3%–4% each minute.

In animal research, stopping chest compressions to provide rescue breathing and EKG monitoring was found to reduce survival rates (recall that the AHA has now defined survival as discharge from hospital neurologically intact). A 2002 and 2003 study found that loss of compression was associated with a decreased chance of converting v-fib to a perfusing EKG rhythm.

Finally, according to data from 2005, healthcare providers’ CPR survived for only 51%–76% of the total time.

When the heart stops beating, myocardial cells rapidly lose their oxygen and energy resources. Strong and quick chest compressions delivered through CPR may help restore them, making the cells ready to function again.

After a cardiac arrest, the myocardial cells may be damaged as they are not receiving enough oxygen. CPR may help restore their intake of oxygen in these circumstances since the scenario is one of an unwitnessed arrest and an unknown condition of these myocardial stores. According to these studies, when the cells are fed, they will be more likely to respond to defibrillation attempts and convert to a different rhythm.

European Resuscitation Council

The European Resuscitation Council is a medical organization that works together with other groups to develop and implement training programs. It also develops standards for resuscitation care throughout Europe. The European Resuscitation Council was formed in 1989. The primary goal of the ERC is “to maintain human life by ensuring that high-quality resuscitation services are available to everyone.”


Cardioversion is a medical treatment in which an abnormally fast heart rate or other cardiac arrhythmia is changed to a normal rhythm with electricity or medicines.

The electrical conduction system of the heart, also known as the cardiac rhythm, is interrupted and reestablished through synchronized cardioversion treatment.

A therapeutic amount of electric current is applied to the heart at a specific point in the cardiac cycle, thus restoring its electrical conduction function. Chemical cardioversion, also known as pharmacological cardioversion, is a therapy that employs antiarrhythmic medications rather than an electrical shock.

Defibrillation Pads and Their Placement

The electrode pad size for AEDs and their surface area have been reduced over the last 20 years due to the miniaturization of the electronic parts used within modern pads.

Defibrillation Pads and Their Placement

External shock defibrillation is administered using paddles or multifunction electrodes (MFE), commonly known as defibrillator pads. Regardless of the method, the following steps should be followed in sequence for optimal energy delivery.

The first thing you need to do is to remove any clothing from the chest of a cardiac arrest patient and ensure the chest is dry.

Electrode Paddle Position

To considerably enhance current flow, secure the electrodes in such a manner that they can reach all or most of the myocardium. One electrode is placed one electrode to the right of the upper sternal border just below the clavicle, which is referred to as a lateral thoracotomy. The second electrode should be placed to the left of the nipple with the center of the electrode in the midaxillary line.

What is the Midaxillary Line?

This is a fictitious landmark line that runs through a person’s body, dividing it into its anterior (front) and posterior (back) halves.

This line begins in the armpit and travels vertically down. The subclavian vein is positioned between the anterior and posterior axillary lines. The anterior and posterior axillary lines, on the other hand, are imaginary landmark lines that stretch across the front (anterior) and rear (posterior) halves of the body.

The armpit is bordered by the anterior axillary fold, formed by the chest muscles (pectoralis), and the posterior axillary fold, which is made up of two big upper-back muscles (latissimus dorsi and teres major).

The alternative is to position the “apex” paddle anterior, over the left precordium, and the other paddle (labeled “sternum”) posterior to the heart in the right interscapular region. Take particular care to keep the defibrillation paddles separate and that paste or gel is not smeared between the paddles since current may travel along the chest wall, “missing” the heart. Self-adhesive monitor/defibrillator electrode pads are also effective and may be used in any of these situations.

When performing cardioversion or defibrillation on patients with permanent pacemakers or ICDs, do not put the electrodes near the device generator because defibrillation might cause the device to malfunction. The myocardium is also subjected to energy starvation during defibrillation, resulting in ineffective energy delivery. Finally, after the patient receives shocks, always check the pacing threshold again to patients with permanent pacemakers because some of the defibrillation currents flow down their pacemaker leads. Consider utilizing the ICD-10 diagnostic code format to highlight any relevant changes in clinical practice or information technology. Also examine the ICD-9 functional classification, as well as its subdivisions.

Possible Interference with Electrode Pads

Finally, if there is a lot of chest hair, the region where the pad/paddle will be placed should be shaved so the adhesive gel touches the skin of the SCA patient. Many companies keep a spare set of pads with their defibrillators and If you have a spare set, use them on the chest hair where you’ll be applying the pads and swiftly rip them off, taking the hair with them. Then apply a new set of pads.

Possible Interference with Electrode Pads

The sternal-apical placement for pads and paddles is one of the three suggested regions by the AHA. The left pad/paddle is placed on the upper right chest wall, and the right one is placed on the patient’s left lateral side, even with their left breast.

The second choice is the biaxial position, in which the pads/paddles are placed directly across from each other on both the right and left lateral chest walls, even with the breasts. The second is to place the left pad/paddle on the upper right chest wall and the right one on the upper left side of the back.

Monophasic vs. Biphasic

According to a recent study, the electrical shock impulse provided by defibrillation machines has an impact on shock success and how well patients respond.

Monophasic Defibrillation

For many years, monophasic defibrillation has been the standard shock delivery method. Monophasic electrical impulse shock delivers precisely the correct quantity of electricity from one pad to another using only one pair of pads. The electricity instantly depolarizes the myocardium when it is placed between the pads, with the cardiac muscle sandwiched in between.

Ventricular fibrillation conversion rates of monophasic defibrillators are usually 60%–80%.

Biphasic Defibrillation

Biphasic defibrillation shock is a technique of defibrillation that uses two pads to repeatedly stimulate the heart in sequence. It repeats this process until the patient’s rhythm is restored. There are two variants, one for each kind of waveform. The most frequent types of non-sinusoidal waveforms are BTE and Rectilinear BIPHASIC waveforms. This biphasic truncated exponential (BTE) and rectilinear biphasic waveforms have different impulse acceleration and duration and are known as biphasic truncated exponential (BTE). Although the waveforms have not been compared extensively against each other, biphasic has a much higher 90 percent shock success rate in converting v-fib.

AHA Guidelines

The AHA guidelines recommend different energy shock settings for different defibrillator types (mono- or biphasic) and, if biphasic, which waveform is employed. Adult patients who are comatose or in VF, regardless of the presence of adequate oxygenation and ventilation, should be promptly defibrillated with 360j doses. When defibrillation is required, the AHA recommends using the lowest possible setting that has proved effective (120j–200j), assuming 100% electrical efficacy. To meet the demands of different applications and applications, various manufacturers and gadgets may establish unique initial and following joule settings for each monitor, generally 120j, 150j, and 200j. The AHA adds that shocks should be equal to or greater than the previous, up to 200j, after the first. According to studies, 120j with a biphasic defibrillator is equivalent to 360j with a monophasic one, but it causes significantly less tissue and cell damage.

Modern AED pads might still be referred to as “paddles” but they are far more advanced than how they are typically described. These modern medical marvels save cardiac arrest victims’ lives and if you ever find yourself in need of saving a cardiac arrest victim, it’s important to know how CPR and an AED can help save someone who you suspect is having a sudden cardiac arrest. Trust an AED to coach you through using the device as well as the placement of the “paddles” of life. Save a life and be a hero to the victim’s family and loved ones. Contact us at AED USA to explore any aspect of an AED program with Zoll, Defibtech, Cardiac Science, Philips, Physio-Control, and Heartsine brands. We carry them all and we have you covered.

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