University of Twente Student Theses


A simulation model to support implementation of a combined walk-in and appointment system at diagnostic facilities

Smid, K. (2013) A simulation model to support implementation of a combined walk-in and appointment system at diagnostic facilities.

[img] PDF
Abstract:INTRODUCTION AND PROBLEM DESCRIPTION: If resources such as machines or personnel in a production or service process are scarce, they have to be allocated in such a way that the objectives of the organization can be realized. The manner in which this is done impacts the performance. At diagnostic facilities appointment systems are commonly used to organize these resources, where supply and demand are matched to avoid crowded waiting rooms and to create a leveled workload. Possible downsides of this system are that there can be several days between the appointment request and the actual moment of service (access time) and that the planning costs time and money. Alternatively, if no schedule is used, patients can walk in without an appointment at any time the facility is open. This system potentially offers logistical benefits: utilization can be increased because no time has to be reserved for slack, no resources have to be used for scheduling and access time is reduced to zero. There are also benefits from the patient’s perspective: less visits to the hospital and the potentially stressful period of awaiting the appointment is avoided. A possible drawback of the system is that the fluctuation in demand can cause peaks in the workload and long waiting time for patients. There are also situations in which a walk-in system is not possible or desired. For this situation a combination between an appointment and walk-in system can be constructed. In this combined system time is reserved for appointments while the remaining time is open for walk-in patients. The challenge in this combination is to balance the pros and cons of both systems and to minimize the number of walk-in patients who is not allowed to walk-in because it is too busy at the diagnostic facility (a deferral). RESEARCH OBJECTIVE AND APPROACH: The objective of this research is to develop a simulation model that can be used to support decision makers at a diagnostic facility with choices regarding the combination of a walk-in and appointment system. To this extent we created the Walk-in and Appointment Simulation Model (WAPSIM), that consists of four elements: (i) the core system with a planner, a choice to accept or defer a walk-in patient and one server, (ii) a preparation component, (iii) a test component and (iv) extra server components. These elements can then be combined to represent real world diagnostic facilities. By adding design choices corresponding to when walk-in is possible, how appointments are scheduled and who gets priority in the waiting room, there is a broad range of functionalities to experiment with. We used the model to analyze a case of the radiology department of the Academic Medical Centre Amsterdam, who are considering to implement a combined walk-in and appointment system for the regular CT-scans and are currently working with an appointment system. RESULTS AND RECOMMENDATIONS: After validation of WAPSIM for the CT-scan case we simulated the situation in which walk-in and appointments are combined. The results show that a combined walk-in and appointment system is a viable option: - Most walk-in patients can be served on the day of the request; - Decrease in the number of no shows, as there are fewer appointments; - Waiting time of appointments decreases compared to the current situation; - Waiting time of walk-in patients is higher than that of appointments; - More patients incur waiting time than in the current situation; - Access time for patients who require an appointment as soon as possible does not change; - The amount of work done outside of office hours increases (overtime). Furthermore we experimented with five design choices, the experimental factors. Three of these factors allow the decision makers to make trade-offs between the performance indicators: - Increasing the allowed waiting time for walk-in patients reduces the fraction of walk-in patients who is deferred, but also leads to higher waiting time for walk-in patients; - By changing the priority in the waiting room from ‘Appointments first’ to ‘Appointments first, unless a walk-in patient is waiting more than an hour’ the waiting time of appointments rises, but the waiting time for walk-in patients decreases. - Introducing a closing time of one hour for walk-in patients (meaning that walk-in patients who arrive one hour before the end of the day are deferred for walk-in), increases the number of deferred walk-in patients increases while the percentage of work done out of office hours decreases. These primary trade-offs give an indication of the effects but may miss important dynamics. For a more extensive analysis we studied the dynamics between the experimental factors, which can be used to explain unexpected outcomes or to make interdependence between several factors apparent. Based on this extensive analysis we can conclude that the used schedules are too restrictive because of agreements with other departments and the underestimation of the processing time of some patient types. Through sensitivity analysis we showed that three small changes in the schedule could improve overall performance. Some of the results of the simulation study can be used to give practical advice, such as the improvement of the schedule. However, there is not a best practice that can be advised. The power of WAPSIM is that all effects can be mapped to aid the decision makers. To make full use of this power we suggest a method in which the main effects from the experimental factors are used to start a discussion between decision makers, and the analysis of the dynamics between factors can be used as catalyst to come to a consensus. We also note that the factors that can be experimented with WAPSIM are only part of the considerations related to the implementation of a combined walk-in and appointment system. There are internal and external organizational changes, such as changes in information requirements and responsibilities, which need to be mapped if a department decides to implement a combined walk-in and appointment system. CONCLUSION We developed a reusable simulation model that can be used to analyze the combination of walk-in and appointments to organize diagnostic facilities. There are many factors that can be experimented with, but it is important to note that the model should be calibrated and validated whenever it is used. We think that WAPSIM can be used for a broad range of cases, however at this point we cannot claim that the model is truly generic because it has only been tested extensively on the CT-case of the AMC. Based on this research the radiology department decided to implement a combined walk-in and appointment system, and the results of the WAPMSIM-analysis will be used to support decision makers with design choices.
Item Type:Essay (Master)
Faculty:BMS: Behavioural, Management and Social Sciences
Subject:85 business administration, organizational science
Programme:Industrial Engineering and Management MSc (60029)
Link to this item:
Export this item as:BibTeX
HTML Citation
Reference Manager


Repository Staff Only: item control page