BACKGROUND:Bystander cardiopulmonary resuscitation (CPR) improves survival. The authors attempted to determine whether the rates at which CPR is performed differ when a cardiac arrest is witnessed by someone known or unknown to the victim.METHODS:Retrospective observational cohort study of all witnessed nontraumatic cardiac arrests (Utstein) from Boston from 1994 to 1998. Cardiac arrests were excluded if the original record was unavailable or if medical or public safety personnel witnessed the cardiac arrest. The relationship between the provider of CPR and the victim was determined by the emergency medical technicians at the scene and later categorized as known or unknown. Survival (survival to hospital discharge) was determined through telephone follow-up with the arrest victim's caregivers.RESULTS:Known bystanders performed CPR 15.5% (42 of 271) of the time (95% confidence interval (95% CI], 11.2%, 19.8%). Unknown bystanders performed CPR 45.8% (66 of 144) (95% CI, 37.6%, 54.1%) of the time. The odds ratio of receiving CPR if an unknown bystander witnessed a cardiac arrest was 4.61 (95% CI, 2.89, 7.34). Arrests witnessed by unknown bystanders had a 24.3% (35 of 144) (95% CI, 17.2%, 31.4%) survival rate. Those witnessed by known bystanders had a 17.7% (95% CI, 13.1%, 22.3%) survival rate (p = 0.110). In a logistic regression model including both bystander status and location of arrest, unknown bystander status remained statistically significantly associated with having CPR performed regardless of location (OR = 3.56, p = 0.01; 95% CI, 1.64, 7.72). Location was not statistically significant in the presence of bystander status (OR = 1.17, p = 0.686).CONCLUSION:Victims of cardiac arrest are more likely to receive CPR when the event is witnessed by bystanders unknown to the victim than if the arrest is witnessed by friends or family.

Objective. To describe the impact of a rapidly deployable, automated external defibrillator (AED)-equipped first-responder service at Boston's Logan International Airport on the rate of survival to hospital discharge after cardiac arrest. Methods. A prospective observational outcome study was undertaken for cardiac arrests taking place on the airport grounds from January 1, 1995, to December 31, 1999. Patients were included if they were unresponsive, they had no palpable pulse and no spontaneous respirations, an AED was turned on, and the cardac arrest took place on airport grounds. Airport fire rescue and emergency medical services (EMS) personnel submitted resuscitation records and AED memory modules for each cardiac arrest. Each author independently reviewed all cardiac arrest reports and code summaries to ensure accuracy and data integrity. Relevant dispatch and response times were determined from airport fire rescue and EMS dispatch records. Patient outcome was determined from hospital patient records. Descriptive statistics were calculated. Results. The airport fire rescue crew responded to 53 cardiac arrests. Of those, 38 met inclusion criteria. In 36 of 38 cases (94.7%), the airport fire rescue crew was first to apply the defibrillator, and the first to deliver a shock in 28 of 32 cases (87.5%) where a shock was delivered. The median response time for the airport fire rescue crew was 2 minutes, with a mode of 1 minute. The EMS response times were 5:29 (95% CI 4:37-6:19) for basic life support crews and 8:07 (95% CI 7:17-8:57) for advanced life support crews. All patients who survived to hospital admission (n = 15) and hospital discharge (n = 8) received their first shock by the airport fire rescue crew. Eight patients (21.1%) survived to hospital discharge. In five of the eight survivors to hospital discharge, defibrillation by the airport crew alone achieved a return of spontaneous circulation. Conclusions. A rapidly deployable first-responder service permits early defibrillation minutes before arrival of EMS personnel. This rapid response positively impacts the return of spontaneous circulation and survival to hospital discharge after cardiac arrest. PREHOSPITAL EMERGENCY CARE 2002;6:1-5

STUDY OBJECTIVE We determined whether automated external defibrillators (AEDs) can meet the American Heart Association performance criteria to detect and shock unstable cardiac rhythms (ventricular fibrillation [VF], ventricular tachycardia [VT]) in the setting of an out-of-hospital cardiac arrest. METHODS AED performance was reviewed for cardiac arrests occurring between January 1, 1995, and December 31, 1997. After every cardiac arrest, data regarding each rhythm analyzed and subsequent response (shock or no shock) were downloaded from the AED memory module. The study paramedic and study physician independently reviewed each case and interpreted cardiac rhythms from downloaded AED data. The emergency medical services medical director resolved all discrepancies in a blinded manner. All cases of out-of-hospital cardiac arrest in which an AED was turned on and a rhythm analyzed were included. The primary objective was the correct identification and defibrillation of VF or VT. Sensitivity, specificity, and predictive values with 95% confidence intervals (CIs) were calculated. Sources of error in AED rhythm management are also described. RESULTS A total of 3,448 AED rhythms were available for interpretation. Sensitivity and specificity for appropriate AED management of a shockable (VF or VT) rhythm were 81.0% (95% CI 77.9% to 83.8%) and 99.9% (95% CI 99.7% to 100%), respectively. Positive and negative predictive values were 99.6% (95% CI 98.7% to 99.9%) and 95.5% (95% CI 94.7% to 96.2%), respectively. There were 132 errors associated with AED management. Two errors resulted in delivery of an inappropriate shock. In the remaining 130 errors, a shockable rhythm was not shocked. Fifty-five (42.3%) errors were AED dependent, 70 (53.9%) were operator dependent, and 5 (3.9%) were unclassified. CONCLUSION The AED had high specificity and moderately high sensitivity in detecting and shocking unstable cardiac rhythms in the out-of-hospital setting. Few cardiac rhythms were mismanaged by the AED. Elimination of operator-dependent errors could increase AED sensitivity.