EMS system performance: the use of cardiac arrest timelines.

The time data used to analyze the significance of time-to-treatment intervals on times from sudden cardiac arrest vary by definition of time and individual system design, making it difficult to compare these data and to extrapolate findings from one study to another to achieve generalizable conclusions. A model is proposed to describe the time-to-treatment/time-to-patient response intervals sought by most researchers to evaluate quality of care and system performance. It provides a mechanism for incorporating system design elements into the cardiac arrest timeline proposed by the Utstein Conference. The present model is composed of generic patient management intervals (classes of intervals common to all systems) that are composed of component intervals (intervals particular to each system) that describe the system's conduct of an emergency medical services call, which, in turn, are constructed of data (activity) points unique to each system. Because each system defines its own data points, the present model permits rigorous definition and analysis of the time data produced by all systems. Each system thereby constructs reliable component intervals, producing a system-specific, real-time depiction of the events related to a cardiac arrest call. Because all systems share the same generic patient management intervals, the resulting cardiac arrest timeline can be compared with those from other systems to assess system performance. The goal of the present model is to facilitate further the standardization of cardiac arrest data acquisition and reporting and evaluation of emergency medical services system performance.