From Simio and Simulation: Modeling, Analysis, Applications

Chapter 9 Problem # 9.5.2

Modify Model 9-1 to support preemption of the Doctor resource for Urgent patients. In particular, if all doctors are busy when an Urgent patient arrives, the Urgent patient should preempt a doctor from one of the other non-Urgent patients. Compare the results of the models. Would you advise that the emergency department make the corresponding change in the real system?

I attempted this problem using two approaches.

Approach A)

For this approach, I tried to use a seize request on the Doctor resource. The Facility view is shown below. However, using a state variable to count the number of seizes that occur, I realized that the doctor is either being seized too many times for non-urgent patients or my logic is incorrect (or both). Shown below, the number of seizes far exceeds the number of Urgent patients.

To attempt to handle this, I tried updating the condition to require that a seize only occurs when 1.) a patient is Urgent, 2.) there’s capacity in the doctor resources, and the Urgent patient has not seen a doctor yet, the UrgentHasDoctor variable.

The resulting OptQuest output using Satisfaction as the response variable seemed mixed in its results. Overall, I didn’t feel confident that this approach was modeled correctly.

Approach B)

For this approach, I based on the logic off of two Simbits examples showing interrupts – InterruptingServerWithMultipleCapacity and InterruptingAcrossMultipleServers.

Facility View.

With this approach, the number of doctor seizes seems more reasonable given the number of Urgent patients in the system. However, I did run into an occasional run-time warning related to destroying entities with seized resources.

With this approach, leverage the existing Before and After Processing Add-Ons on the TraumaRooms.

The logic is shown below for the TraumaRooms_Processing Process. I only applied the preemption of the doctor resource at the TraumaRooms, assuming this station was the first station where an Urgent patient would need immediate need from a doctor.

The OptQuest output again shows mixed results for this approach where satisfication is not exceeding th 80% rate.