Systems approaches in emergency medical services: the history, the impact, and the future.

Systems approaches have been important in planning and evaluating emergency medical services (EMS) systems. However, maximal use of systems approaches are limited by small political boundaries, the lack of user-friendly systems tools, and the need for EMS planning staffs who are familiar with these systems tools. Developing technology, particularly communications, will continue to have a great impact on EMS delivery. In addition, the need is seen for continuing advances in systems concepts, and in particular, the promotion and incorporation of health and prevention of injury as systems concepts.