Improving health care systems following an incident investigation.

All health care is delivered to patients through an assemblage of minisystems. (A minisystem is the smallest system that can deliver a single clinical benefit.) It is the failure of these minisystems that reportedly results in between 44,000 and 98,000 iatrogenic deaths in the United States, annually. Device-related, accident investigations are intended to identify the latent defects within these minisystems and to recommend corrective actions that will prevent a recurrence. A generic, system's risk model has been developed for analyzing the performance of these minisystems. It provides the investigator with a mental model of the interacting components of the minisystem and provides a logical pathway toward the root causes of an adverse event. Of practical importance in using this model, is that operator error contributes to approximately 69% of the failures of health care minisystems and a fundamental understanding of human factors and human error is required.