Automated external defibrillator for use by lay rescuer in CPR

Automated external defibrillator for use by lay rescuer in CPR

Since early defibrillation is the third and one of the vital links in the chain of survival after a sudden cardiac arrest due to ventricular fibrillation (VF), automated external defibrillator (AED) for use in public places by lay rescuers have been devised. The rescuer turns on the device and attaches the adhesive electrodes on the chest of the victim. AED is a computerized device which can analyze the victim’s cardiac rhythm and deliver a shock if the rhythm is ventricular fibrillation or ventricular tachycardia (VT). The AED gives audible and visible prompts to guide the lay rescuer. The computer algorithm of an AED will advise the rescuer whether a shock is needed. The diagnostic algorithms of AEDs have been shown to be quite accurate in assessing and delivering an appropriate shock when needed. In one of the early studies, AED was used by paramedics to detect ventricular fibrillation and deliver shocks in 39 patients with out-of-hospital cardiac arrests. The AED identified and delivered at least one shock in 13 of the 16 patients with ventricular fibrillation, providing 81% sensitivity [1]. Response of the AED was correct in all 21 non ventricular fibrillation rhythms which included 13 asystole and no shocks were delivered (100% specificity). The device did not cause any injury to patients or personnel. Rhythm could not be assessed in 2 patients.

Newer AEDs can also provide recorded information on the frequency and depth of chest compressions during CPR and this could improve performance of bystander CPR.

Use and development of public access defibrillation (PAD) programs have been promoted by the American Heart Association since 1995 in order to improve survival in out of hospital sudden cardiac arrest. The goal of PAD programs is to shorten the time from onset of VF until CPR and shock delivery. High survival rates of the order of 40 – 70% have been obtained in out of hospital cardiac arrest when defibrillation occurs within three to five minutes of witnessed VF sudden cardiac arrest with immediate bystander CPR. Such high survival rates cannot be expected when the time to defibrillation is longer. For the success of a community lay rescuer AED program, the following aspects need to be taken care of: a planned and practiced response, training of potential rescuers in CPR and AED use, good link with the local emergency medical service and finally an ongoing quality improvement program [2].

It may be noted that AEDs are not useful for non shockable rhythms. Since non perfusing rhythms may be present in most patients after a shock, the need for ongoing CPR is highlighted.

A study from Italy assessed community-based AED only resuscitation for out-of-hospital cardiac arrest patients [3]. The rescuers attached the publicly available AEDs, turned it on and followed the instructions. They did not do CPR of any sort. It was a prospective study from 2001 to 2014 and was known locally as “Progetto Vita”. Google Translates Progetto Vita as Life Project. Progetto Vita treated had 41.4% survival to hospital discharge among the 95 patients, compared to 5.9% of the 3271 patients treated by emergency medical services (EMS). At 13 year follow up, estimates of survival was 31.8% when AED only was used and 2.4% with standard EMS/CPR response. When the 95 EMS patients with fastest response times were compared, Progetto Vita was associated with a more than 2-fold increased rate of survival.

References

1. Cummins RO, Eisenberg M, Bergner L, Murray JA. Sensitivity, accuracy, and safety of an automatic external defibrillator. Lancet. 1984 Aug 11;2(8398):318-20.
2. Aufderheide T, Hazinski MF, Nichol G, Steffens SS, Buroker A, McCune R, Stapleton E, Nadkarni V, Potts J, Ramirez RR, Eigel B, Epstein A, Sayre M, Halperin H, Cummins RO; American Heart Association Emergency Cardiovascular Care Committee; Council on Clinical Cardiology; Office of State Advocacy. Community lay rescuer automated external defibrillation programs: key state legislative components and implementation strategies: a summary of a decade of experience for healthcare providers, policymakers, legislators, employers, and community leaders from the American Heart Association Emergency Cardiovascular Care Committee, Council on Clinical Cardiology, and Office of State Advocacy. Circulation. 2006 Mar 7;113(9):1260-70.
3. Capucci A, Aschieri D, Guerra F, Pelizzoni V, Nani S, Villani GQ, Bardy GH. Community-based automated external defibrillator only resuscitation for out-of-hospital cardiac arrest patients. Am Heart J. 2016 Feb;172:192-200.