Christos Vasilakis

A simulation modelling approach to evaluating length of stay, occupancy, emptiness and bed blocking in a hospital geriatric department.

The flow of patients through geriatric hospitals has been previously described in terms of acute (short‐stay), rehabilitation (medium‐stay), and long‐stay states where the bed occupancy at a census point is modelled by a mixed exponential model using BOMPS (Bed Occupancy Modelling and Planning System). In this a patient is initially admitted to acute care. The majority of the patients are discharged within a few days into their own homes or through death. The rest are converted into medium‐stay patients where they could stay for a few months and thereafter either leave the system or move on to a long‐stay compartment where they could stay until they die. The model forecasts the average length of stay as well as the average number of patients in each state. The average length of stay in the acute compartment is artificially high if some would‐be long‐term patients are kept waiting in the short‐stay compartment until beds become available in long‐stay (residential and nursing homes). In this paper we consider the problem as a queueing system to assess the effect of blockage on the flow of patients in geriatric departments. What‐if analysis is used to allow a greater understanding of bed requirements and effective utilisation of resources.

Systematic Review of the Use of Computer Simulation Modeling of Patient Flow in Surgical Care

Computer simulation has been employed to evaluate proposed changes in the delivery of health care. However, little is known about the utility of simulation approaches for analysis of changes in the delivery of surgical care. We searched eight bibliographic databases for this comprehensive review of the literature published over the past five decades, and found 34 publications that reported on simulation models for the flow of surgical patients. The majority of these publications presented a description of the simulation approach: 91% outlined the underlying assumptions for modeling, 88% presented the system requirements, and 91% described the input and output data. However, only half of the publications reported that models were constructed to address the needs of policy-makers, and only 26% reported some involvement of health system managers and policy-makers in the simulation study. In addition, we found a wide variation in the presentation of assumptions, system requirements, input and output data, and results of simulation-based policy analysis.

A simulation study of scheduling clinic appointments in surgical care: individual surgeon versus pooled lists

The purpose of this paper is to compare two methods of scheduling outpatient clinic appointments in the setting where the availability of surgeons for appointments depends on other clinical activities. We used discrete-event simulation to evaluate the likely impact of the scheduling methods on the number of patients waiting for appointments, and the times to appointment and to surgery. The progression of individual patients in a surgical service was modelled as a series of updates in patient records in reaction to events generated by care delivery processes in an asynchronous fashion. We used the Statecharts visual formalism to define states and transitions within each care delivery process, based on detailed functional and behavioural specifications. Our results suggest that pooling referrals, so that clinic appointments are scheduled with the first available surgeon, has a differential impact on different segments of patient flow and across surgical priority groups.

A simulation study of the winter bed crisis

The winter bed crisis is a cyclical phenomenon which appears in British hospitals every year, two or three weeks after Christmas. The crisis is usually attributed to factors such as the bad weather, influenza, older people, geriatricians, lack of cash or nurse shortages. However, a possible alternative explanation could be that beds within the hospital are blocked because of lack of social services for discharge of hospital patients during the Christmas period. Adopting this explanation of why the bed crisis occurs, the problem was considered as a queuing system and discrete event simulation was employed to evaluate the model numerically. The model shows that stopping discharges of rehabilitating patients for 21 days accompanied by a cessation of planned patients for 14 days precipitate a bed crisis when the planned admissions recommence. The extensive “what-if” capabilities of such models could be proved to be crucial to the designing and implementation of possible solutions to the problem.

A participative and facilitative conceptual modelling framework for discrete event simulation studies in healthcare

Existing approaches to conceptual modelling (CM) in discrete-event simulation do not formally support the participation of a group of stakeholders. Simulation in healthcare can benefit from stakeholder participation as it makes possible to share multiple views and tacit knowledge from different parts of the system. We put forward a framework tailored to healthcare that supports the interaction of simulation modellers with a group of stakeholders to arrive at a common conceptual model. The framework incorporates two facilitated workshops. It consists of a package including: three key stages and sub-stages; activities and guidance; tools and prescribed outputs. The CM framework is tested in a real case study of an obesity system. The benefits of using this framework in healthcare studies and more widely in simulation are discussed. The paper also considers how the framework meets the CM requirements.

Clinical reports of pulmonary metastasectomy for colorectal cancer: a citation network analysis.

Introduction:Pulmonary metastasectomy for colorectal cancer is a commonly performed and well-established practice of ∼50 years standing. However, there have been no controlled studies, randomised or otherwise. We sought to investigate the evidence base that has been used in establishing its status as a standard of care.Methods:Among 51 papers used in a recent systematic review and quantitative synthesis, a citation network analysis was performed. A total of 344 publications (the 51 index papers and a further 293 cited in them) constitute the citation network.Results:The pattern of citation is that of a citation cascade. Specific analyses show the frequent use of historical or landmark papers, which add authority. Papers expressing an opposing viewpoint are rarely cited.Conclusions:The citation network for this common and well-established practice provides an example of selective citation. This pattern of citation tends to escalate belief in a clinical practice even when it lacks a high-quality evidence base and may create an impression of more authority than is warranted.

The history of adoption of hepatic resection for metastatic colorectal cancer: 1984–95

BACKGROUND Liver resection for metastatic colorectal cancer became established without randomized trials. Proponents of surgical resection point out 5-year survival approaching 50% whilst critics question how much of the apparent effect is due to patient selection. METHOD A 2006 systematic review of reported outcomes provided the starting point for citation analysis followed by thematic analysis of the texts of the most cited papers. RESULTS 54 reports from 1988 to 2002 cited 709 unique publications a total of 1714 times. The 15 most cited papers were explored in detail, and showed clear examples of duplicate reporting and overlapping data sets. Textual analysis revealed proposals for a randomized controlled trial, but this was argued to be unethical by others, and no trial was undertaken. CONCLUSIONS This critical review reveals how the case for this surgery was made, and examines the arguments that influenced acceptance and adoption of this surgery.

Systems modelling and simulation in health service design, delivery and decision making

The ever increasing pressures to ensure the most efficient and effective use of limited health service resources will, over time, encourage policy makers to turn to system modelling solutions. Such techniques have been available for decades, but despite ample research which demonstrates potential, their application in health services to date is limited. This article surveys the breadth of approaches available to support delivery and design across many areas and levels of healthcare planning. A case study in emergency stroke care is presented as an exemplar of an impactful application of health system modelling. This is followed by a discussion of the key issues surrounding the application of these methods in health, what barriers need to be overcome to ensure more effective implementation, as well as likely developments in the future.

A participative modelling framework for developing conceptual models in healthcare simulation studies

Conceptual modelling, one of the first stages in a simulation study, is about understanding the situation under study and deciding what and how to model. We argue that stakeholder involvement as part of conceptual modelling could lead to a more successful simulation study with better prospects for implementation. Our work is mainly applied in health care studies, which are characterized by many stakeholders with multiple views and objectives and often a politically charged environment. We develop a participative conceptual modelling framework, which uses tools from soft systems methodology, a problem structuring approach. The benefit of this approach lies in that it supports the conceptual modelling process by engaging stakeholders in a structured and participative way. It involves facilitated workshops, using a set of tools developed. A case study of the conceptual modelling process undertaken for an obesity system is provided to illustrate the proposed framework and tools.

Using a model of the performance measures in Soft Systems Methodology (SSM) to take action: a case study in health care

This paper uses a case study of a multidisciplinary colorectal cancer team in health care to explain how a model of performance measures can lead to debate and action in Soft System Methodology (SSM). This study gives a greater emphasis and role to the performance measures than currently given in typical SSM studies. Currently, the concept of performance measurement in SSM is in the form of a set of criteria used to judge the performance of the SSM model (the purposeful activity model). These performance criteria are definitions of efficacy, efficiency, effectiveness, ethicality and elegance. However, the use of performance measures within SSM is not clear and therefore criticized by some as nebulous. This paper uses a case study to explain how to involve the stakeholders in deriving a performance measurement model (PMM), which is a more detailed expansion of the performance criteria. The paper concludes with some reflections about how the PMM can fit in the SSM cycle, with two modes of practice put forward.