BACKGROUND: Cardiopulmonary resuscitation (CPR) initiated at the scene of a cardiac arrest may increase survival by up to 50%. In some locations 911 dispatchers provide instructions for CPR to untrained bystanders. Bystanders who witness a cardiac arrest often do not perform CPR because of fears of contamination and contagion. A pilot study performed in King County, Washington, showed a 3.5% increase in survival with chest compressions alone when compared with chest compressions with mouth-to-mouth ventilation.
POPULATION STUDIED: The study was performed in the Seattle, Washington, area with a fire department-based emergency medical care system. Patients were enrolled if they had a cardiac arrest diagnosed over the telephone by the dispatcher and there was a bystander willing to be instructed. A total of 1296 patients were included in the trial. Of these, 776 were excluded on the basis of a subsequent paramedic report of drug or alcohol overdose, carbon monoxide poisoning, trauma, or absence of cardiac arrest. The 520 remaining patients had an average age of 68 years, 64% were men, 58% had a witnessed cardiac arrest, and 88% occurred in a home.
STUDY DESIGN AND VALIDITY: After receiving a 911 call the emergency medical services (EMS) dispatcher would determine if the patient was eligible for this study. On the basis of computer randomization, the dispatcher provided instructions for traditional CPR or chest compressions alone. A total of 1296 patients were randomized; after exclusions 520 were analyzed. Of these, 241 were assigned to receive chest compressions alone and 279 to receive the traditional method of CPR. The study design was reasonable given the limitations of performing a trial under these circumstances.
OUTCOMES MEASURED: The primary outcome measured was survival to hospital discharge. Secondary outcomes included admission to the hospital, neurologic status of the survivors, duration of instructions, and bystander opinions.
RESULTS: Of the 520 patients included in the study, 64 survived to hospital discharge. Twenty-nine patients (10.4%) survived in the CPR with mouth-to-mouth ventilation group, and 35 patients (14.6%) survived in the chest compressions only group. There was no statistically significant difference in survival to discharge between the 2 groups (P=.18). A similar nonsignificant trend was noted for hospitalizations, with 34.1% of patients in the CPR group admitted to the hospital and 40.2% of the patients in the chest compressions-only group admitted (P=.15). There was no difference found in neurologic morbidity after a mean follow-up time of 2.4 years. Fewer bystanders refused the instructions in the compressions-only group (7.2% vs 2.9%), and instruction time was much shorter (1 minute vs 2.4 minutes). Compliance of the EMS dispatchers with the written protocol was excellent.
Chest compressions alone are as effective as CPR with mouth-to-mouth ventilation during the first few minutes of a cardiac arrest. This study was performed in an urban area with prompt EMS response (approximately 4 minutes to arrive on the scene). Whether these findings would apply in areas with longer response times is unknown: The overall effect may be hard to identify given the very poor outcomes associated with longer response times. Although not part of the study, the authors speculate that opening the airway may be a beneficial adjunct maneuver, since the compressions alone can move some air. When offering untrained bystanders instructions during cardiac arrests, EMS dispatchers need not teach mouth-to-mouth ventilation.