Influence of Cardiopulmonary Resuscitation Prior to Defibrillation in Patients With Out-of-Hospital Ventricular Fibrillation

Abstract

There is little doubt that speed in providing care represents the major determinant of survival for patients with out-of-hospital ventricular fibrillation (VF). That relationship has been documented for initiation of cardiopulmonary resuscitation (CPR)^1,2 as well as for the arrival of personnel and devices necessary for defibrillation.^3,4 Since 1970, the pattern for delivering out-of-hospital emergency care in Seattle, Wash, has incorporated rapidly responding first units staffed by emergency medical technicians (EMTs), followed as soon as possible by a later-arriving paramedic unit.⁵ In 1980, we initiated the use of early defibrillation by EMTs in 4 first-responding units.⁶ Later, automated external defibrillators (AEDs) were extensively used. Whereas the survival experience of subsets of VF patients in Seattle seemed to be improved with AEDs,⁷ the overall survival rate remained virtually unchanged (Figure 1) despite an approximately 3- to 4-minute shortened time to defibrillatory shock in most cases. Such a time saving had been predicted to increase survival by several percentage points.³ Prompted by the lack of overall improvement in survival and by the experimental work of Niemann et al⁸ in which resuscitation rates improved when animals were pretreated with CPR and epinephrine, we modified the protocol for first-responding Seattle Fire Department EMTs. The revised protocol directed the provision of approximately 90 seconds of CPR before automated analysis of cardiac rhythm for patients found in cardiac arrest.