Out of hospital cardiac arrest : with focus on bystander CPR and public access defibrillation

Abstract

Background: Out-of-hospital cardiac arrest (OHCA) annually affecting hundreds of thousands of patients in Europe alone. Survival is highly dependent on time to treatment (cardiopulmonary resuscitation (CPR) and defibrillation). Long emergency medical system (EMS) time intervals and low bystander CPR rates are major obstacles for increased survival. New treatment strategies are needed to reach and treat patients faster. Automated external defibrillators (AEDs) make it is possible for lay people to deliver life-saving shocks within minutes, a concept known as public access defibrillation (PAD). Further, the development of mobile phone technology makes it possible to identify and recruit lay volunteers to nearby OHCAs for life-saving actions.

Aim: To evaluate the new treatment possibilities of PAD and mobile phone technology involving lay and non-health care responders for early CPR and defibrillation in case of OHCA.

Methods: In all studies, data from the Swedish Cardiac Arrest Register (SCAR) were used. This is a national register of data from resuscitation attempts from EMS treated OHCAs since 1992. In Study I SCAR data was analysed in connection with the numbers of cases and changes of characteristics over time (1992-2005) among OHCAs patients suffering arrest outside home. In Study III, SCAR data and records from ambulance police and fire services was reviewed to evaluate the impact on survival of different defibrillation strategies: police and fire services (first responders), EMS or PAD in OHCAs in public locations. In Studies II and IV a mobile positioning system (MPS) was used to geographically locate and dispatch CPR-trained lay volunteers to nearby OHCAs. Study II was a pilot study in Stockholm city centre and Study IV was a full-scale countywide randomized controlled trial.

Results: In Study I, 26% of all OHCAs were found to be potential subjects of PAD. Among these cases, the proportion of patients with an initial rhythm that could be defibrillated decreased over time, but overall survival increased. In Study II, 1200 lay volunteers were recruited. During six months there were 92 cases of suspected OHCAs where the MPS was triggered. In 45% of these, one or more lay volunteer(s) reached the scene prior to the EMS. In Study III, 474 of 6532 OHCAs were defined as subjects for PAD and were defibrillated at a public location. Survival was 71% (n=51) in patients defibrillated by a public AED versus 31% (n=101) in patients defibrillated by the EMS (p<0,001). In cases defibrillated by first responders survival was 42% (n=22). In Study IV, 5989 lay volunteers were recruited. 667 cases of EMS-treated OHCAs where the MPS was triggered were analysed. In cases ran¬domized to activation of the MPS for dispatch of lay responders bystander CPR rate was 62% versus 48% where the system was not activated (absolute difference, 13.9 percentage points; 95% CI, 6.2 to 21.2, p <0.001).