Objectives: To determine the frequency of agonal breathing during cardiac arrest (CA), its impact on the ability of 9-1-1 dispatchers to identify CA, and the impact of dispatch-assisted cardiopulmonary resuscitation (CPR) instructions on bystander CPR rates.
Methods: A before-after observational study enrolling out-of-hospital adult CA patients where resuscitation was attempted in a single city with basic life support with defibrillation/advanced life support tiered emergency medical services. Victim, caller, and system characteristics were measured during two successive nine-month periods before (control group) and after (intervention group) the introduction of dispatch-assisted CPR instructions.
Results: There were 529 CAs between July 1, 2003, and December 31, 2004. Victim characteristics were similar in the control (n = 295) and intervention (n = 234) period; mean age was 68.3 years; 66.7% were male; 50.1% of CAs were witnessed; call-to-vehicle stop was 6 minutes, 37 seconds; ventricular fibrillation/ventricular tachycardia occurred in 29.9%; and the survival rate was 4.0%. Dispatchers identified 56.3% (95% confidence interval [CI] = 48.9% to 63.0%) of CA cases; agonal breathing was present in 37.0% (95% CI = 30.1% to 43.9%) of all CA cases and accounted for 50.0% (95% CI = 39.1% to 60.9%) of missed diagnoses. Callers provided ventilations in 17.2% and chest compressions in 8.3% of cases as a result of the intervention. Long time intervals were observed between call to diagnosis (2 minutes, 38 seconds) and during ventilation instructions (2 minutes, 5 seconds). Bystander CPR rates increased from 16.7% in the control phase to 26.4% in the intervention phase (absolute rate, 9.7%; 95% CI = 8.5% to 11.3%; p = 0.006).
Conclusions: This trial demonstrates an increase in bystander CPR rate after the introduction of dispatch-assisted CPR. Agonal breathing occurred frequently and had a negative impact on the recognition of CA. There were long time intervals between call initiation and diagnosis of CA and during mouth-to-mouth ventilation instructions.