Johns Hopkins Health System uses SIMUL8 to improve patient flow and waiting times across its emergency departments

Learn why simulation has been a vital tool for optimizing ED throughput at Johns Hopkins Health System for more than 10 years

Johns Hopkins Health System is a $7.7 billion integrated global health enterprise and one of the leading health care systems in the United States. JHHS’s mission is to improve the health of the world by setting the standard of excellence in medical education, research and clinical care.

Its six US member hospitals receive a combined 2,800,000 outpatient visits, 115,000 inpatients and 350,000 emergency visits annually.

JHHS has empowered decision making throughout its network of hospitals using SIMUL8’s simulation software, including the Howard County General Hospital, Bayview Medical Center and The Johns Hopkins Hospital.

Simulation has proven invaluable for analyzing current and future emergency department performance, as well as enabling business cases to be made by providing strong evidentiary support for proposed changes.

Acknowledgements to: Eric Hamrock, Senior Project Administrator, Department of Operation Integration, Johns Hopkins / Kerrie Paige, President, NovaSim

Johns Hopkins Health System's achievements using SIMUL8:

  • Average wait times for ED psychology services reduced from 61.8 to 16.2 minutes at Howard County Hospital
  • Identified optimum current and future bed capacity for a $40 million ED expansion, as well as increasing throughput and decreasing patient wait times at Bayview Medical Center
  • Using insight and results garnered from simulations to work towards achieving ‘zero-wait’ at Johns Hopkins Hospital's 1,192 bed ED

Further resources for this case study:

Rising pressure on Emergency Departments

From their post-World War Two beginnings in the US, emergency departments (EDs) have played a vital role in treating seriously ill and injured patients.

They have evolved from part-time coverage, staffed by community physicians, to around-the-clock facilities operated by full-time trained emergency physicians. The specialized knowledge and skills of ED staff has enabled an expansion of services; diagnosing and managing a huge range of health issues without resorting to hospital admission.

This expansion of available services, along with factors such as difficulties accessing primary care and increasingly complex patient populations, led to a 26% rise in visits recorded by US EDs between 1993 to 2003. Yet, during this period, the number of hospital-based EDs actually decreased by 425. (Institute of Medicine, 2007)

Did you know? According to the National Center for Health Statistics, approximately 20% of U.S. adults seek health care at emergency departments each year.

Increased crowding in EDs

Rising use of ED services by uninsured patients, more intensive examinations, and fewer inpatient beds have also extended lengths of stay in EDs and increased the number of patients in hospitals at any time of day.

As a result, EDs have grown increasingly crowded. According to a national survey by the Institute of Medicine, 91% of EDs reported crowding as a problem with 40% indicating that it was a daily occurrence.

Crowding is a serious issue for hospitals as it can compromise care quality, patient safety and satisfaction, while also leading to increased costs.

How are hospitals tackling crowding?

Although there are many external forces outside of EDs control that contribute to crowding, there are also several internal opportunities to improve use of resources and flow of patients.

These include refining department layouts, increasing the number of inpatient beds, staffing levels, and improving operational processes to more efficiently serve patients.

However, with the sheer number of resources and interlinked processes within EDs, it can be extremely complicated to test and implement changes without risk to patient service quality.

Discrete event simulation is utilized by hospital like Johns Hopkins Health System to meet this challenge.

Why is discrete event simulation used for ED decision making?


Discrete event simulation is a very powerful tool for decision making. By using simulation software like SIMUL8, hospitals are able to test ideas and assumptions for improvements.

This is very effective in settings such as the emergency department where there is a lot more variation and unpredictability, particularly in how patients arrive.

Over the last 10 years, Johns Hopkins Health System has relied on simulation to identify and implement a range of improvements to patient flow across their network of emergency department facilities; from its early use at Howard County Hospital through to its use at its largest trauma center at Johns Hopkins Hospital.

  Learn more: Read Johns Hopkins Health System's Eric Hamrock's seven tips for using simulation in successful performance improvement programs.

"Everybody accepts management tools that we have now as the way to approach a problem, but even a lean project with good statistical analysis will only give you the results of the statistical analysis. It won’t draw you a picture of what your whole operation will look like; that is what I think discrete event simulation does that is different."

Jim Scheulen, Chief Administrative Officer, Johns Hopkins

Reducing ED wait times at Howard County Hospital

In starting out with simulation, Johns Hopkins focused on one of the less complex EDs in their system. Howard County, a community hospital based in Maryland, has 18 ED beds and treats over 175 patients per day.

Stating with this smaller facility to build a robust ED simulation template, the team considered common elements involved in ED systems. Although each facility might look different from others, they contain consistent aspects such as fast track areas, acute care areas and patient arrival patterns that differ by time of day.

By creating a template simulation with these common key elements, JHHS has been able to apply the same base simulation to other, more complex EDs across its network and turn simulation projects around faster.

Within Howard County, SIMUL8 has been used to improve wait times, change fast track schedules, reduce process times for ancillary processes, perform surge analysis and change patient flows.

Testing these scenarios using the template simulation, JHHS saw impressive real-world results which echoed those of what the simulation model had projected. For example, by adding an extra psychology pod, average wait times reduced from 61.8 to 16.2 minutes and allowed the hospital to treat higher volumes of patients.

Such results gave JHHS confidence to apply simulation to larger, more complex ED environments.


Johns Hopkins Healthcare System – Howard County Hospital simulation model

Planning capacity for a $40 million ED expansion at Bayview Medical Center

From Howard County, JHHS used SIMUL8's simulation software at their next hospital in terms of ED complexity, the Bayview Medical Centre. Uniquely positioned, the facility serves both an urban and county population and receives over 50,000 patients per year in the ED.

At Bayview Medical Center, it was identified that forecasted ED demands could not be served effectively by the existing facility complex. Requiring significant investment in a new, expanded ED facility, JHHS utilized simulation to make decisions around capacity planning for the future.

Using SIMUL8 to test ED performance levels with varying bed capacities against future population projections, it was shown that capacity for 48 beds in the near-term and 62 for future growth would provide an optimum utilization rate of around 70%.

The insight provided by simulation has ensured that JHHS’ $40 million investment in the Bayview Medical Center ED expansion will improve the quality and efficiency of patient care for many years to come.


Johns Hopkins Healthcare System – Bayview Hospital simulation model

"By expanding our facilities and adding ambulance bays, we’ll have the space and processes in place to care for more patients and increase throughput. When the project is finished, we expect to have improved patient access and decreased patient wait times, which will make for a better overall patient experience."

Ed Bessman, M.D., Chair of Emergency Medicine at Johns Hopkins Bayview

Simulating towards a ‘zero-wait’ ED at Johns Hopkins Hospital

The Johns Hopkins Hospital, opened in 1889, has been ranked number one in the nation by U.S. News & World Report for 22 years of the survey’s 25 year history.

As JHHS’s largest trauma center, serving a very complex patient population, the hospital has over 1,192 acute care beds and receives over 100,000 ED visits each year.

With the ultimate aim of achieving a ‘zero-wait’ ED, SIMUL8’s simulation software has been used at Johns Hopkins Hospital to answer questions around the prospective effects of increasing capacity, reducing patient dwell time and changing intra-departmental processes to contribute to this vision.

Adding more capacity

One of the first scenarios tested by Johns Hopkins Hospital to cut ED wait times was to increase bed capacity. As a relatively new facility, there was potential scope to add bed capacity in the RAP and super tracks areas.

This RAP area being used for most patients to do an initial assessment before moving to a bed in the main ED, and the super track for patients with conditions which can be treated quickly.

As shown in the simulation results, although adding one or two rooms would provide steep reductions in wait time for a bed, adding large numbers of additional beds would not completely eliminate ED waiting times alone.


Time to First Beds (Additional Beds)

Reducing patient dwell time

Johns Hopkins also tested cutting the time to the first bed through dwell time reductions; with dwell time being the total length of time that patients spend in ED areas. Simulation showed that reducing dwell time as much as 30%, a potentially difficult task to achieve in itself, would also not completely eliminate patient wait times.

Therefore, the team looked at combining increased capacity and dwell time reduction factors in order to achieve 95% of patients to first bed within 30 minutes. Even here, the simulation showed that Johns Hopkins Hospital would have to add a substantial number of beds and heavily reduce dwell time to eliminate wait time.


Dwell Time vs Total Beds

Intra-department process changes

The last scenario Johns Hopkins Hospital looked at involved making intra-department process changes.

The team had observed that boarding time, the time it took patients to get to an inpatient bed once it was determined that they needed one, had been increasing. The ED had been planning for a lower volume of patients than what they had been experiencing, creating a bottleneck (as shown in the simulation model here).

The team looked at various scenarios to reduce boarding time down to an average of certain levels, or the 95th percentile - what would this do to overall performance improvement?

JHHS found that this intervention proved to have the biggest likely impact on reducing ED wait time.

This analysis, together with the animated simulation models provided by SIMUL8, helped to convey the potential benefits of reducing boarding time to senior ED stakeholders.


Johns Hopkins Healthcare System – Johns Hopkins Hospital simulation model

“This information was very useful to be able to talk to the Department of Medicine. We could say ‘these are the changes that would be useful, and if we are able to work together to decrease boarding time down to a consistent level, here is what we can accomplish in the ED.”

Kerrie Paige, President, NovaSim

Continuing the process improvement journey

SIMUL8 has played a vital role in enabling Johns Hopkins Health System to make a wide range of decisions which have contributed to its commitment of delivering high-quality, compassionate care for its patients.

Simulation has not only enabled the organization to make smarter, more effective use of valuable resources over the last 10 years, but will increasingly be relied on by healthcare organizations in times of rising costs and patient demand:

“Healthcare has got to a point where we cannot afford to mismanage scare resources; it used to be that bed space, emergency department space, and all the other resources that we have, frankly, were not so scarce. We operated at utilization rates where we did not have to manage things down to the level that other industries have probably had to manage for some time.

With ongoing cost reductions and other restrictions within the healthcare environment, clearly our resources are getting to be very precious and scarce, so we need to use tools like SIMUL8 to make sure we are getting the highest performance we can out of the most reasonable amount of resources.”

Jim Scheulen, Chief Administrative Officer, Johns Hopkins

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