STEP 1: PROBLEM FORMULATION

The initial step in this phase is to describe the problem that is to be studied with ABMS independent from any software that will be used. In this step, it is important to consider six main topics (Salamon, 2011):

1. The problem: to provide an overall description of the problem. 2. The processes: to identify the processes

3. The entities: to describe the entities engaged in the processes, their characteristics, and to define what they want, what they do, and how they interact with each other.

4. The environment: to explain the characteristics of the environment and its interrelations with the entities.

5. The aim: to define the purpose of the study, what is to be measured, how it is to be measured and what questions are to be answered

6. Validation: how to evaluate and to test the developed model.

5.3.1.1 The problem

As was discussed in previous chapters, Emergency Departments are highly complex and dynamic systems. Emergency Departments in the UK are governed by a performance framework that has a set of performance standards that the departments must maintain. In particular, the four-hour standard originally stated that 98% of the patients being seen in an accident and emergency department should leave the department in less than four hours either because they are admitted as inpatients or because they are discharged from the department. Therefore, doctors and nurses need to make decisions that require balancing the patients’ clinical priorities with the department’s time performance standards. As a result, the decisions that clinical staff face are continuously affected by the different situations that are present in the healthcare provision process.

5.3.1.2 The process

Figure 5-2 shows the outline of the patient flows in an A&E department as a chain of activities. Patients arrive into the department via an ambulance or by the walk-in entrance. Patients arriving by ambulance are usually triaged and registered in route to the hospital before entering the department. Patients arriving by walk-in are first registered by a clerk and then are triaged by a nurse. The triage system considered here involves a colour and number coding scheme using red

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(number 5) to represent a patient who needs immediate attention, Orange (number 4) means very urgent, Yellow (number 3) means urgent, Green (number 2) standard, and Blue (number 1) non- urgent. Depending on the condition of the patient, the initial assessment that follows triage is done by a nurse or a doctor. Some patients may require tests at this stage, and some others may be discharged or immediately admitted as inpatients to the hospital. Those patients that require tests are usually treated by the same doctor who conducts the initial assessment.

Figure 5-2. Patient flows in an A&E department

5.3.1.3 The entities

The different entities that participate in the process are:

• The patients who come to the department wish to be seen by the appropriate staff and to be diagnosed or treated within a reasonable time. They move from one process to another, queue when necessary, and leave when treatment is complete, or they are admitted to the hospital as inpatients.

• The clerk is in charge of registering the patients. The Clerks only task is to obtain necessary information from the patient to indicate them where to go next.

• The nurses are in charge of triaging the patients and in some cases of doing the first assessment and may accompany the doctors when necessary. Nurses wish to ensure that the patients are treated in the minimum possible time.

The doctors are in charge of doing the first assessment and the treatment of the patients. As with the nurses, the doctors wish to provide an excellent service within a reasonable time.

5.3.1.4 The environment

The environment in which they are acting is dynamic and uncertain. There are several sources of uncertainty in this environment, such as patient demand and the duration of the activities of the service process. This is a dynamic environment because the conditions of the environment change

Registration Arrival of patients Triage Initial assessment Test/X- ray Treatment Discharge/ Admission

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over time while the entities are making decisions. Three main characteristics make this environment dynamic. First is that the volume of patients that enter the department during the day changes with time; there are some busy periods and others that are quieter. Second, the number of tasks that a doctor or nurse can perform may vary depending on the conditions of the department at a particular time. A doctor, for example, could see more than one patient at a time if necessary. Third, the number of staff that work in the department changes over time: doctors, nurses and clerks have different working shifts.

5.3.1.5 The aim

The main purpose of the ABMS model is to gain insight into the overall value of including human behaviour into an A&E simulation. More specifically, this model aims to model how the four-hour target and other external factors may affect the behaviour of the clinical staff inside an A&E department. This model makes a simple representation of a typical A&E department, modelling some interactions among the patients coming to the department to be assessed and treated for their medical conditions, and the staff who are responsible for the provision of those services.

5.3.1.6 Validation

The ABMS model developed in this research does not intend to reproduce a real A&E department but to demonstrate how human behaviour can be incorporated in an ABMS model of an A&E department. The ABMS model is based on the DES model developed by Günal (2008). Therefore, the validation process will be done by comparing the ABMS model against the Günal model rather than comparing the ABMS model against the real world.