Theoretical calculation of maximum attainable benefit of public access defibrillation in Belgium¹

Abstract 

Objective: Assuming that a lay person performing cardiopulmonary resuscitation (CPR) will also use an automatic external defibrillator (AED) wherever available, we tried to estimate the maximal attainable benefit of public access defibrillation in some centres in Belgium. Methods: We analysed retrospectively the data from the Belgian Cardio Pulmonary Cerebral Resuscitation Registry collected between 1991 and June 1996. The majority of these emergency medical service (EMS) systems are two-tiered with an early defibrillation program for the first tier and a physician-staffed second tier. Results: The data show that, in 5543 registered cases, there were 1001 (18%) adults with non-traumatic ventricular fibrillation/ventricular tachycardia (VF/VT) as the first monitored rhythm. In this subgroup there were 419 (42%) cases who had lay CPR. The duration of lay CPR before the first defibrillation either by the first or the second tier is known in 357 cases. This duration was more than 5 min and 10 min, in 80% and 53% of the cases, respectively. The median (Q₁, Q₃) lay CPR duration was 11 (7, 15) min. Survival to hospital discharge in this subgroup was achieved in 80/357 (22%) patients. Using Weaver's linear model for survival after witnessed VF/VT, an estimated increase of more than 30% in survival rate was calculated. Conclusion: It is concluded that in our EMS system, laymen reach a substantial number of VF/VT victims many minutes before the arrival of the professional EMS teams. Therefore, a substantial increase in the number of survivors could be expected if lay responders were prepared to use an AED.

Keywords:  Cardiac arrest, Linear regression model, Public access defibrillation

• 1 Prior presentation in part at the Public Access Defibrillation II meeting in Washington, DC, 17–19 April 1997.