Table 2.

Overview of the selected patient flow performance indicators used in this study.

Abbreviation	Patient Flow Performance Indicators (PFPI) and Description	Unit
TTT	Time to Treatment: This performance indicator calculates the patient population’s average time within the emergency department before the treatment starts in their assigned treatment room. The value is in this simulation study given on a per-patient basis, i.e., the number of hours of waiting per patient. A lower value is better, all else equal, compared to a higher value, as less waiting means that each patient faster receives health care for the condition they got admitted for. This patient performance indicator is reported for the aggregate total group of patient agents (Tot.), the patients classified with the COVID+ status, and the patients classified with the COVID− status.	Hours per patient [h/pt]
ALOS	The average length of stay: The performance indicator is calculated, showing the total amount of time spent in the emergency department on a per-patient basis. It tracks the time taken from entering the emergency department, the point of admission, until the patient has been discharged from the emergency department. The performance indicator is measured as an average for all the patient agents, meaning the value gives the average hours of time each patient spent in the emergency department. Similar to the previous patient flow performance indicator, TTT, this performance indicator is also reported for the aggregate total group of patient agents (Tot.), the patients classified with the COVID+ status, and the patients classified with the COVID− status.	Hours per patient [h/pt]
Crowding	The patient flow performance indicator called ‘crowding’ calculates for each and every moment how many patients are present in the emergency department. This patient flow performance indicator is, including its naming, from the case emergency department’s patient flow improvements project. In the implementation of this metric, we show how much of the total simulated time the crowding has been beyond three different thresholds of interest as defined by the case emergency department in their internal working emphasis on the improvement of patient flow conditions and response for over-crowding problematics. The three threshold levels are set at 15, 25, and 30 patients in the emergency department.	%
Peak Crowding	Peak crowding, as its name suggests, is concerned about the peak of crowding, the previous performance indicator. The given number (#) tells how many patients were residing at the emergency department at the point in time when the number was at its maximum that day. In addition, the metric also tracks the time during the day the peak occurs. Thus, the first portion states the number of patients, while the second portion states how much the clock was at that given point.	# & Time
Time Start Use/Time in Use	This patient flow performance indicator states the time different resources of particular interest start being used during the day. In this performance measure implementation, it has been chosen to track when the extra treatment rooms (E.TR.), triage (Tri.), and waiting zone (WZ) are used. Secondly, the performance indicator calculates how much the given resource is used in proportion to the total elapsed time of that time, e.g., a reading in the Tri.-column at ‘11:00′ means that the triage that day was not used until 11:00. The second value shows the percentage amount of that day this resource has been used at least by one patient.	Time
Time Full	This performance measure, as the name suggests, keeps track of when particular resources of interest, the extra treatment rooms (E.TR.), triage (Tri.), and waiting zone (WZ), are full, meaning they cannot further take any more patients. Similar to the previous performance indicator, this also has dual tracking. Firstly, the time when the given resource is full is given next, a percentage of how long the elapsed time the resource has been full.	Time & %
Time in WR	This performance measure calculates how long patients on average, spent in the emergency department waiting room. The indicator is calculated as an average across all the patients.	h
Times TR blocked for COVID+.	This performance indicator tracks the total number of times (#) a patient agent classified as COVID+ is blocked from entering the treatment room after pre-triage. This is a critical point for the emergency department as it is heavily loaded with the patients so much that they cannot immediately fast-track a patient to an isolated room.	#
Times TR Assigned	This performance measure tracks the number of times (#) a treatment room (TR) has been assigned to a patient. This refer to the term ‘seize’ used in simulation modeling discipline; how many times a certain resource is utilized for the purpose treatment of a patient. Each time a patient is assigned to a treatment room is resource-consuming, especially considering the sanitization of the rooms.	#