Defibrillator pads go on bare skin in two specific spots: one on the upper right chest below the collarbone, and one on the lower left side of the chest. This diagonal placement creates an electrical path that crosses through the heart, giving the shock the best chance of restoring a normal rhythm. Getting the pads positioned correctly takes only a few seconds, but those seconds matter. Here’s exactly how to do it.
Why Pad Placement Matters
A defibrillator shock creates a current that travels from one pad to the other through your chest. For that current to work, it needs to pass through the heart muscle itself, essentially “sandwiching” the heart between the two electrodes. The standard diagonal placement captures both the front and back portions of the heart’s pumping chambers.
If pads are placed too close together, too high, or off to one side, the current may bypass critical heart tissue. The heart’s muscle fibers also conduct electricity better in certain directions, which is why the specific angle between the two pads isn’t arbitrary. It’s designed to send current along the path most likely to interrupt the chaotic electrical signals of cardiac arrest and allow an organized heartbeat to return.
Step-by-Step Pad Placement for Adults
Once you power on an AED, it will give you voice prompts. Most devices include a diagram on the pads themselves showing where each one goes. Here’s what to do:
- Expose the chest completely. Remove or cut away clothing, including bras or undershirts. You need bare skin.
- Place the first pad on the upper right chest. Position it just below the collarbone, above the right nipple. It should sit to the right of the breastbone.
- Place the second pad on the lower left side. On a male patient, align it with the bottom edge of the left pectoral muscle. On a female patient, place it under the left breast. The pad should sit along the side of the ribcage, roughly in line with the armpit.
- Press each pad firmly so it adheres completely to the skin with no air pockets or lifted edges.
This front-and-side positioning (called anterolateral) is the standard recommended by the American Heart Association. An alternative is anteroposterior placement, where one pad goes on the center of the chest and the other on the back between the shoulder blades. Some clinical settings use this approach, but for bystander rescue with an AED, the front-and-side method is standard because it doesn’t require rolling the person over.
Preparing the Chest
Pads need direct, firm contact with dry skin. Several things can interfere with that contact, and most AED kits include supplies to handle them.
Wet skin: If the person is wet from rain, sweat, or submersion in water, move them away from standing water first. Then dry the chest quickly with a towel or cloth before applying the pads. Water on the skin can cause the electrical current to arc between the pads along the surface rather than traveling through the chest, dramatically reducing the shock’s effectiveness.
Chest hair: Thick chest hair prevents the pads from sticking to the skin. If a pad won’t adhere, press down firmly. If the AED gives a “check electrodes” warning, rip the pads off quickly (this pulls out the hair underneath), then apply a fresh set. If the problem persists, use the razor typically included in the AED kit to shave the two areas where the pads will go. Speed matters here, so don’t shave the entire chest. Just clear the two pad-sized patches.
Medication patches: Transdermal patches for pain, nicotine, or heart medication can cause burns if a defibrillator pad is placed directly over them. Peel off any patch in the pad area, wipe away the residue, and use gloves if available so you don’t absorb the medication through your own skin.
Jewelry: Remove any necklaces or chest piercings that fall in the pad area. Metal can interfere with current delivery and cause burns.
Adjustments for Implanted Devices
Some people have a pacemaker or implanted defibrillator visible as a hard lump under the skin, usually below the left or right collarbone. Don’t place a pad directly over the device. Shift the pad at least an inch or so away from the lump. The AED will still work. Placing a pad directly on the implant can block current delivery and potentially damage the device.
Placement on Women
AEDs use the same pad positions on everyone, regardless of breast tissue. The key difference is practical: the lower left pad needs to make contact with the chest wall, not sit on top of breast tissue. Lift the breast and place the pad on the skin underneath it, along the lower ribcage. The National Heart, Lung, and Blood Institute emphasizes that AEDs work the same way on people with breasts, and hesitation about exposing a woman’s chest should not delay treatment. Cardiac arrest is fatal within minutes without intervention.
Placement on Children
For children under about 55 pounds (roughly 8 years old), use pediatric pads if the AED has them. These deliver a lower energy dose. If pediatric pads aren’t available, adult pads can and should be used. On a small child, the two pads may be too large to fit on the chest without touching each other. If that happens, use anteroposterior placement: one pad on the center of the chest, one on the center of the back between the shoulder blades. The pads should never overlap or touch each other, as this would short-circuit the shock.
What Happens After You Apply the Pads
Once both pads are on, the AED analyzes the heart’s rhythm automatically. Don’t touch the person during analysis. The device will tell you whether a shock is advised. If it is, the AED will either deliver the shock automatically or prompt you to press a button. Make sure no one is touching the person when the shock is delivered.
After the shock, immediately resume chest compressions. The AED will continue to monitor the heart rhythm and tell you when to stop for another analysis, typically every two minutes. Leave the pads attached even if the person starts breathing again. Their heart rhythm could deteriorate, and the AED needs to stay connected to detect that.
If the first shock doesn’t work, the AED will prompt you to try again. In some cases, switching to an anteroposterior pad position (one pad on the front, one on the back) can change the direction of the electrical current enough to succeed where the standard placement didn’t. This reflects the fact that everyone’s heart sits slightly differently in their chest, and what works as a default position may not be optimal for a particular person.