Automated External Defibrillator (AED)

AEDs are portable electronic devices that analyze the heart’s rhythm and, when appropriate, can deliver an electric shock (called defibrillation), which helps the heart return to a normal, effective rhythm. When applied soon enough, AEDs greatly increase the likelihood of survival from cardiac arrest. For every minute that lifesaving care, including defibrillation, is delayed, it is estimated that survival declines as much as 10%. AEDs should only be used with unresponsive victims who have no breathing and no pulse.

General AED Information

AED operation

AED operation

The AED is a complex device, but it has been designed to be used by the general public. Many of the essential functions of the AED are performed automatically or with the touch of a button. The AED monitors the heart’s electrical activity through two electrodes in the AED pads placed on the chest. A computer in the AED determines the need for a shock by analyzing the pattern, size, and frequency of EKG waves. If these waves resemble a shockable rhythm (i.e., V-fib or V-tach), the machine readies an electrical charge. When the charge is ready, usually you must press a button to deliver the shock to the patient.

Delivering an electric shock with an AED disrupts all abnormal electrical activity long enough to enable the heart to return to normal sinus rhythm. If V-fib or V-tach is not corrected by defibrillation, eventually all electrical activity will cease, resulting in a condition called asystole. Asystole cannot be corrected by defibrillation.

Many AEDs are equipped with adult and pediatric pads so an appropriate electrical shock can be given to each patient. When pediatric pads are applied, a lower level shock considered appropriate for infants and children up to 8 years of age or weighing less than 55 pounds is delivered. If pediatric pads are not available, adult pads can be used for children and infants, assuming local protocols allow this. Pediatric pads, however, should not be used on adults.

After the AED analyzes the patient, whether or not a shock is advised, you must perform 2 minutes of CPR with the pads in place until the AED re-analyzes for a shockable rhythm. The “analyze for shock, 2-minutes of CPR, re-analyze for shock, and repeat” algorithm is programmed into all AEDs. Every time the AED analyzes, the results could be a shock or no shock; you must continue to provide CPR and follow AED prompts until EMS personnel arrive and take over or the patient displays an obvious sign of life by moving, breathing, or speaking. When this happens, stop CPR and monitor the patient’s condition.

Special AED Situations

Certain situations require responders to take additional actions when using an AED.

  • AEDs and water - Always dry the patient’s chest before applying the pads. Also, if the patient is in the rain or in standing water, remove the patient to shelter or a dry part of the deck or facility before applying pads. A shock delivered in the rain or standing water may conduct the energy to the responder or bystanders.
  • Body piercings and jewelry - Body piercings and jewelry do not need to be removed to use the AED. Do not delay AED use in an attempt to remove these items.
  • Chest hair - If the patient has excessive chest hair, this may cause difficulty with pad-to-skin contact. This is rarely a problem, however, so apply pads as soon as possible. If you get a “check pads” error from the AED, you may need to quickly shave a small area for pad placement.
  • Hypothermia - As with water, dry the patient and quickly remove wet clothing. If you do not feel a pulse, begin CPR and apply the AED as soon as it is available. While performing CPR and using the AED, protect the patient from further heat loss.
  • Other AED protocols - Older AEDs delivered up to 3 shocks before recommending CPR. Current protocols only deliver 1 shock and then CPR. If you have an older AED, follow its algorithm since it is neither harmful nor incorrect, only out-of-date. Contact the manufacturer as soon as possible to have the AED reprogrammed to the current protocol as soon as possible. The current protocol allows improved coordination of AED operation and CPR and is more beneficial to the patient.
  • Pacemakers and implantable cardioverter-defibrillators - If the patient has an implanted device, do not place the pads directly over it. This may interfere with analysis and shock delivery. Adjust pad placement as necessary and follow established protocols.
  • Transdermal medication patches - The patient may have a transdermal medication patch (e.g., nitroglycerin patch, nicotin patch, etc.). Remove any patch from the patient’s chest before applying AED pads.
  • Trauma - If the patient is in cardiac arrest because of significant trauma, you can still use an AED. Follow local protocols.

AED Precautions

When operating an AED, follow these general precautions:

  • Do not use alcohol to wipe the patient’s chest; alcohol is flammable.
  • Do not use adult pads on a child or infant unless pediatric pads are not available.
  • Do not use pediatric pads on an adult patient.
  • Do not touch the patient while the AED is analyzing. Touching or moving the patient can affect the analysis.
  • Before shocking the patient, make sure no one is in contact with the patient or resuscitation equipment. The AED delivers a potentially lethal shock.
  • Do not touch the patient while defibrillating. You or someone else can be shocked.
  • Do not defibrillate around combustible materials, such as gasoline or free-flowing oxygen.
  • Do not use an AED in a movving vehicle. Movement may affect analysis.
  • Do not use an AED on a patient in contact with water. Move the patient away from standing water or out of the rain before defibrillating.
  • Remove nitroglycerin patches (and all other transdermal medication patches) before attaching AED pads.
  • Do not use a mobile phone or radio within 6 feet of the AED. Radio frequency and electromagnetic interference can disrupt AED analysis.
  • Never place pads on an individual who is not in cardiac arrest.

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