To the Editor.
—We applaud the effort by Dr Gallagher and colleagues1 to extend their earlier study on the disappointing outcomes of out-of-hospital cardiac arrest in New York City2 to evaluate the effectiveness of bystander-initiated cardiopulmonary resuscitation (CPR) in that large urban setting. We also acknowledge that outcome is likely to be contingent on the effectiveness with which precordial compression is performed, although there is evidence that rescue breathing is of much less importance in their patient subset of sudden (nonasphyxial) deaths.3-6The authors evaluated the capability of emergency medical technicians to make objective judgments on the effectiveness of the interventions rendered by bystanders. Their evaluation was based on CPR trials on mannequins. Yet, this did not serve as a control on post hoc observer bias. The medical rescue personnel were both observers and providers. They provided professional life support and were witnesses to the outcome of