What is patient flow?

Patient flow describes how people move through the steps of care, such as arrival, assessment, treatment, admission and discharge. Smooth flow means short waits and good use of staff and beds, while blocked flow causes crowding and risk. It is the central view for finding where a health system is slowed down.

How it works

Each step has a capacity and a processing time. When arrivals exceed what a step can handle, a queue forms before it, and the queue grows until demand drops or capacity rises. A step that limits the whole system is called a bottleneck.

Steps depend on each other. If ward beds are full because discharges are slow, patients cannot leave the emergency department, which then fills with those waiting for a bed. Fixing the front step does little until the blocked step downstream is solved, so effort is best aimed at the bottleneck rather than at the place where the queue is seen.

Example

Say an emergency department sees 120 patients a day. Treatment takes place in the department, and 25% of patients, or 30 a day, need a ward bed. The ward can discharge 24 patients a day. Each day, 6 more patients need a bed than are released, so the number waiting in the department grows by 6 daily. After 10 days, 60 patients are waiting, even though the department itself is working at full pace. Raising ward discharges to 30 a day ends the growth. These figures are illustrative.

How to model it in Machinations

Chain the steps with Pools and Queues: a Source for arrivals, a Queue for triage, a Pool for treatment, a Gate that sends a share to the ward, and a Pool for ward beds with a Delay for the stay. Make arrivals, bed numbers and discharge speed Levers. Play and chart the queue lengths to find the bottleneck.