The DGHPSim A&E model

A&E waiting time targets are a long-standing element of the NHS performance measurement regime. The current target requires 98% of A&E patients to discharged, or admitted to hospital beds, within 4 hours. That is, virtually all A&E patients should spend less than 4 hours in the unit.

Most general hospitals have an A&E (ER) unit, which accept patients who arrive themselves or are brought in by ambulance. Most A&E patients are not subsequently admitted as inpatients but are fully treated in A&E. In many hospitals, those that are thought to require inpatient care are initially admitted to assessment units for observation. Later, they they may be discharged from the assessment unit or moved onto inpatients wards.




The DGHPSim A&E model  simulates individual patient as they arrive, wait, are treated, undergo diagnostic tests and then may be discharged or admitted for further care. The times taken for each element of a patient's time in A&E will vary and so the simulator users stochastic sampling methods to represent this.

Used alone, the A&E simulator can be used to assess the performance of an A&E department against the 4-hour target. The model requires: 

• The arrival patterns of walk-in and ambulance patients
• The times needed to complete the common activities in A&E (e.g. initial assessment) 
• The physical capacity of the unit
• The probabilities of different journeys through the unit.

The two graphs below show the real and simulated performance of 2 A&E departments. The red line is the simulated performance and the black is the real-life performance. It is clear that, in the left hand A&E Department, something strange is happening in real-life. It seems that the 4-hour target is causing action to be taken on many patients just before the 4 hour deadline.



The DGHPSim A&E model can also be linked to the others in the DGHPSim suite, thereby generating emergency admissions to the inpatient side of the hospital.