A system dynamics model for planning and evaluating shifts in health services: The case of cardiac catheterisation procedures in the NHS.

The shift in the balance between the primary, secondary and tertiary levels of the National Health Service is an established trend in health care. This has been motivated by various factors, including the desire to improve access to services. However, service shifts can stimulate further demand and thus undermine efforts to improve services overall. There is a need for "joined-up thinking" in respect of service shifts since existing analyses have been limited to isolated parts of the system, and little attention has been given to the actual mechanisms of the feedback or knock-on effects. The model-based methodology of system dynamics could be useful as it is designed for the study of the connections between different parts of systems and feedback effects. This thesis assesses the usefulness of system dynamics as a planning and evaluation tool for service shifts. A case study approach is followed, based upon a shift in cardiac catheterisation services from the established tertiary level to the secondary level involving three hospitals in England. The factors involved in service shifts are described, and the processes and causative forces at play across the different health service boundaries are captured by means of the system dynamics-based model procedure. The study reveals several interacting feedback mechanisms underlying changes in demand. It also demonstrates that by understanding the feedback structure, "joined-up solutions to joined-up problems" may be designed. For example, a more effective policy would be the service shift (to improve access) combined with the use of clinical guidelines (to suppress demand) and with changes to the forces that drive activity rates (to ensure that both the average waiting time and the waiting list length are controlled), In feedback terms, using clinical guidelines weakens existing feedback mechanisms whilst changing the forces that drive activity rates creates new feedback mechanisms.