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Care Pathways System dynamics represents processes and patient pathways in a unique language of stocks and rates. Stocks are important measurable accumulations of physical (and non-physical) resources in the world. They are built and depleted over time as input and output rates to them change. For example, the arrival of patients into a treatment facility is a rate, but the number waiting for the treatment is a stock. Likewise, the movement of patients from the wait stock into treatment is a rate , but those being treated is a stock. Further, the movement of patients from treatment to, say, assessment is a rate and those in assessment is a stock. Any patient pathway can thus be represented as a series of stocks and rates. Stocks are essentially delays, which separate and buffer their inputs from their outputs. They persist through time and continue to influence other flows even when their inputs and outputs are switched off. Recognising the difference between stocks and rates is fundamental to understanding the world as a system. Rates are sometimes exogeneous variables to an organisation but are more often the managerial variables, which often can be redesigned. Stocks are the measureable states of the organisation (patients, staff and other resources) which provide information for managerial policies. Symmetric consulting have been working with groups of managers and clinicians to map, simulate and design patient pathways in a variety of settings by formulating them in this way. For example, in the case of patients flowing through hospital we have been interested in the rates of flow of patients into different wards (where the number of beds is capacity constrained) and the rate of discharge of patients from hospital to post acute services (where the post acute beds are also capacity constrained). The purpose to demonstrate where bottleneck might occur and how these might be averted if waiting is not allowed. An interesting insight of such modelling is that, to improve overall performance, it is usually much more cost effective to change rate variables (say, to redirect patient flows) than to change stock variables (say, the number of beds). We recommend you download the whole system commissioning template on this web site to investigate this pathway modelling further. |
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