26 - Automated external defibrillators

Summary

History of AEDs

Automated external defibrillators (AEDs) as we now know them have had a rapid and interesting evolution. The first report of an “automatic cardiac resuscitator” was made by Diack et al. in 1979, who had developed the defibrillator, the Heart-Aid. A first clinical report on successful ambulance use was published in 1982. The design of this defibrillator was unusual for several reasons. First, it used a tongue electrode together with a chest electrode for defibrillation. Second, the tongue blade also contained a sensor for respiration, which prevented the defibrillator from delivering a shock as long as an air stream was detected over the tongue. Confidence in the algorithm to detect ventricular fibrillation (VF) by the ECG was not sufficient: a second independent sign of circulatory arrest was desired. Further automated analysis of the ECG and defibrillation in cardiac arrest was investigated first in defibrillators that were used by traditional responders such as Emergency Medical Technicians. Then, when safety and efficacy were confirmed, the use was extended to fire fighters who were already part of the Emergency Medical Services (EMS) and to police squads who had never been part of the EMS. It became clear that the future of automated defibrillation was with lay rescuers with limited training, without the ability to interpret ECGs. Ease of use was paramount.

Therefore, new AEDs were designed with the lay rescuer in mind, with increasing simplicity and decreasing weight, volume, and cost.