CPR Chicago: Outcome of CPR in a Large Metropolitan Area - Where are the Survivors?

Becker LB, Ostrander MP, Barrett J, Kondos GT Annals of Emergency Medicine 1991 Vol 20 Pages 355-361

The authors suggest that survival from out-of-hospital cardiac arrest in cities with populations of more than 1 million, has not been studied adequately. This study was undertaken to determine the overall survival rate for Chicago (More than 3 million inhabitants in 228 square miles), the effect of previously reported variables on survival, and to compare the observed survival rates with those previously reported. In the Chicago EMS system, two person crews trained in advanced life support, staff 55 ambulances on a 24-hour-a-day basis. If a paramedic unit is not immediately available upon receipt of a 9-1-1 call, or is more than 18 blocks from the address, an ambulance assist unit staffed by firefighters trained in CPR is dispatched first, with paramedics following as soon as possible. This occurred in 10% of the cases reviewed. An ambulance assist unit is also dispatched if dispatchers recognize a cardiac arrest or paramedics call for backup at the scene of a cardiac arrest. A total of 3,221 consecutive prehospital arrest patients on whom paramedics attempted resuscitation, were studied prospectively during 1987. The study population consisted of 1,812 (56%) men and 1,409 (44%) women. In all, 1,689 (52%) were white, 1,390 (43%) were black, and the remainder either Hispanic, Asian, or of unknown race. Mean age was 67 +/- 16 years. The incidence of out-of hospital cardiac arrest was 107/100,000 in the population. Most (77%) of the arrests occurred in private residences with 29% of these having a specific patient access problem. Ninety-one percent of the patients were pronounced dead in emergency departments, 7% died later in hospital, and only 2% survived to hospital discharge. Among patients with combined favourable variables of bystander-witnessed arrest, bystander-initiated CPR, and initial rhythm of V-Fib or V-Tach, the survival rate was 10%. Among patients whose arrests were paramedic-witnessed with initial V-Fib or V-Tach, the survival rate was 13%. Overall survival rates were significantly lower than those reported in most previous studies based on smaller communities. They were however, consistent with the rates reported in the one comparable study of a large city (Stockholm). The single factor that most likely contributed to the poor overall survival was the relatively long interval between collapse and defibrillation (mean of 16 minutes). Logistical, demographic and other special characteristics of large cities may have affected the rates. The authors suggest that we have much to learn about out-of-hospital cardiac arrest in large cities. If we are to improve survival rates, we urgently need 1) further study of comparable metropolitan sites, 2) further study of each component of the EMS system, and 3) rigorous efforts among researchers to standardize terms and validate measurements. For Chicago, potential improvements include educating the patient community, enhancing the ability of dispatch personnel to recognize cardiac arrest, improving traffic management for emergency vehicles, implementing a two-tiered response with the first responders using automatic defibrillators, creating additional first responders by training and equipping police and other nontraditional health care providers, and re-emphasizing the priority of rapid defibrillation.