MANG 6122 Simulation
Coursework Part B
1. You must upload on to the Blackboard site as “Part B – Report” a SINGLE Word document, labelled with your family name, containing the following three sections:
a. A BRIEF management report (1000 words maximum) for the hospital making your recommendations and briefly explaining in non-technical language why you have come to that conclusion. You should discuss any key assumptions in the model, and their implications for interpreting the results.
b. A printout of the Simul8 screen for your model, showing the routing arrows.
c. A short technical Appendix briefly describing how you chose the run length, the warm-up period, and the number of iterations, and your experimentation strategy.
2. You must hand a printed copy of this Word file in to Reception.
3. You must also upload the Simul8 file (showing your BEST solution) on to the Blackboard site. Please name the Simul8 file with your family name, e.g. mine would be “Brailsford.s8”.
Summary
Upload to Blackboard:
• Part B – Report (a single Word document containing a) to c) above)
• Part B – Model (a Simul8 file)
Hand in to Reception:
• Printed copy of the Word doc
Your work will be assessed on the quality of your solution, the clarity of your explanations, the extent to which you demonstrate your understanding of simulation methodology, and your ability to use Simul8.
Marking scheme (approximate)
Simul8 model correct, with appropriate use of various aspects of Simul8 30
Technical appendix clear and correct: sensible experimentation strategy described clearly 20
Presentation of results: intelligent selection of appropriate output variables 15
Professional covering letter 5
Report for the hospital – clarity of explanation, appropriate use of graphs/tables to explain recommendations, short and informative Exec Summary 30
100
The Emergency Room
You have been employed as a business consultant by the management of Queen Mary’s Hospital, Southampton, in order to advise them on staffing levels in the Emergency Department (ED).
Patients arrive at the ED either by ambulance, or independently as “walk-ins”. The walk-in patients first join a queue for “Triage”, where they are rapidly assessed by a nurse and assigned a category between 1 and 5, according to how seriously ill they are. Category 1 is the most serious and is for life-threatening conditions such as heart attack or major trauma; Category 5 is the least serious and is for minor ailments and injuries. All ambulance arrivals are assumed to be Category 1 and do not receive triage. The proportions of walk-in patients in each triage category are as follows:
Category % in this category
1 5
2 15
3 25
4 30
5 25
Following arrival (in the case of ambulance patients) or after Triage (in the case of walk-in patients) patients then wait to be examined by a doctor. Category 1, 2 and 3 patients are examined in a process called “Majors”. In theory, Category 1 patients should not have to wait, and therefore Category 1 patients have their own special queue for Majors and take priority over any category 2 and 3 patients who are also waiting. Category 4 and 5 patients are seen in a process called “Minors”.
After this examination, patients take different paths through the ED, depending on their triage category.
• After Minors, Category 5 patients just need some simple treatment (“Treatment 1”) and then they are able to go home.
• After Minors, Category 4 patients all go for diagnostic tests (“Diagnostics”). After this, they all receive further, more complex treatment (“Treatment 2”), after which 85% of patients are able to go home and 15% will be admitted to hospital.
• After Majors, Triage category 2 and 3 patients follow the same path as Category 4: they all have Diagnostics, undergo Treatment 2 and then 85% go home and 15% are admitted.
• After Majors, all Category 1 patients go the Resuscitation area (“Resus”). Sadly, 5% of patients die in Resus; the rest get admitted to hospital.
Three types of staff work in the ED: doctors, nurses and porters. Porters are needed to transport patients to other parts of the hospital.
Data have been collected over a period of six months for the various processes in the ED, and probability distribution functions have been fitted for them, as shown in the Table below. The time units are minutes. This Table also shows the number of staff required for each process.
Process
PDF Resources
Ambulance arrivals Neg exp (30) –
Walk in arrivals Neg exp (5) –
Triage Triangular (5,8,12) 1 nurse
Minors Triangular (15,20,40) 1 doctor
Majors Triangular (20,30,60) 1 doctor, 2 nurses
Resus Uniform (20,60) 2 doctors, 2 nurses
Diagnostics Fixed, 60 1 nurse, 1 porter
Treatment 1 Uniform (20,40) 1 nurse
Treatment 2 Uniform (40,60) 2 nurses
Admit Fixed, 5 1 nurse, 1 porter
Build a Simul8 model for this system and use your model to tell the hospital how many doctors, nurses and porters there should be. You should bear in mind the following factors:
• Although the UK Government has now abolished the official “4-hour target” for monitoring the performance of EDs, most UK hospitals still strive to attain this. The precise target was that 98% of patients should not spend more than 4 hours inside the ED. The admission process counts towards this duration.
• Obviously, the hospital is concerned about costs and therefore wishes to employ as few staff as possible, consistent with providing high-quality care.
Technical points
1. You should alter the Time format to “Simple count from zero” (this is in the Clock – Clock properties menu). Assume the ED is open 24/7, 365 days a year and that all arrivals, processes and staffing levels remain the same for every hour of the day and day of the week. You should use a time unit of minutes.
2. You will need to do a warm-up since otherwise the simulation will start with an empty ED. This is also in the Clock Properties menu – you will also need to alter the Results Collection Period. You will need to choose these durations yourself and justify your choice in your report.
3. Of course in a real ED, Category 1 patients would not be allowed to wait for Majors or for Resus. If all the staff were busy with lower category patients, in reality one or more of these less serious patients would have their treatment interrupted while the staff dealt with the Category 1 patient. This is difficult, although not impossible, to model in Simul8. Do not attempt to model interrupted activities. Although Category 1 patients have their own queue for Majors, which should have priority over the Category 2/3 queue, there may still be occasions when patients wait here. The same is also true for Resus. You should simply discuss the implications of this modelling limitation in your report.
4. You will need to create two labels in this model. One will be the Triage category which for walk-in patients is a user-defined distribution and is assigned at the entry point. For ambulance arrivals it is always set equal to 1. The triage category remains unchanged for the whole time a patient is in the system. The other label is needed for those places where Routing Out is done by triage category. This label, which you might call “next”, will be used to indicate which destination that patient will go to, out of the list of all possible destinations in the Routing Out dialog. Its value will be assigned by using Visual Logic. This is exactly the same logic as the Babies example you had in the lecture “Advanced Simul8” and you will have practised in the lab classes on December 8th. The VL should be used to check the triage category and to set the value of “next” accordingly.
For example, suppose process P is just for Categories 4 and 5, after which we want to route Category 4 patients to queue Q1 and Category 5 patients to queue Q2. The VL in workcenter P will be of the form
IF Triage category = 4 THEN
SET next = 1
ELSE
SET next = 2
(We can just use ELSE because if patients are not Category 4, then they must be Category 5).
For workcenter P, choose Routing out by Label and select the label “next”. Finally, you just then need to make sure that Queue Q1 is in position 1 in the destination list and Queue Q2 is in position 2.
5. There will be a surgery session for Simul8 in the class slot in Week 12. However the PhD students who run this session will NOT answer detailed questions about the coursework, or tell you if your model is right or not. Please do not ask them this! They will have been given strict instructions about what they can and cannot help you with.
Final hint. The easiest way to import Simul8 windows into a Word document is:
• Select the required window in Simul8
• Press Alt-PrintScreen (i.e. hold down the Alt key and at the same time press the Print Screen key) to copy the window to the clipboard
• Go to your Word document and press Ctrl-V to paste the contents of the clipboard into your document.
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