Estimation of the evacuation time in an emergency situation in hospitals

Abstract

In this paper, a prediction model is presented that estimates the evacuation time in an emergency situation for hospitals. The model is generic enough to be used in various hospital settings. This model can provide incident managers with estimates of the evacuation times of different types of patients and can offer support to the managers with their resource allocation decisions in emergency situations. The major advantage of the prediction model is that the computation time is very short and the model does not need a lengthy and costly design. The model was applied for several different evacuation scenarios and the results were compared with those of a simulation model which had already been designed for use by the hospital. The comparison shows that the prediction model can provide estimates of the evacuation time that are similar to the results found by using costly and time-consuming simulation models.

Introduction

In accordance with the rules and regulations of the Federal Emergency Management Agency (FEMA) and Joint Commission on Accreditation of Healthcare Organizations (JCAHO), all hospitals and healthcare facilities need to have a plan in place to be able to respond to internal and external emergencies. This plan is usually activated and supervised by a designated incident manager (Jafari, Golmohammadi, & Seyed, 2008). For this plan, the decision to allocate and assign available resources (such as medical and non-medical staff, elevators, and so on) to the floors and units in need of help during the course of evacuation highly depends on the emergency type and the estimated evacuation time. This decision making is vital when multiple floors are in danger and all of the patients, together with their family members, medical records and necessary medications need to be vacated to some safe locations. Some of these floors may have patients with critical conditions and therefore the incident manager may need to determine an estimate of the evacuation process time to assign more resources to those floors to make the operation faster, safer and more efficient.

Although the Joint Commission does not require estimated evacuation times, the estimation can help managers evaluate and measure the efficiency of their resources, level of utilization and response times. The ultimate goal is to save more lives in hospitals and healthcare facilities at the time of emergency and the determination of evacuation times demonstrates how a facility can accomplish this task with minimum loss.

In most major hospitals and clinics, there is a Division of Emergency Preparedness (DEP). The major goals of this division are to:

• Evaluate the current performance of operations and executive plans for potential disaster events.

• Educate medical and administrative staff about their roles and responsibilities in potential disaster events.

• Work with state and local partners to improve policies and plans for emergency response to health threats.

The use of quantitative decision making tools can provide insight for hospital managers to run what-if scenarios in order to estimate the evacuation response time in different situations and to evaluate their plans and resources. The results may impact on improving the training programs and improve policies and plans for a real emergency event.

With respect to emergency planning, a large number of research studies suggest alternative methods to deal with the evacuation of people from disaster areas through the use of the roadways. Computer programs have been developed to simulate various alternative traffic management strategies under different scenarios in order to improve highway network performance during an evacuation process (Hobeika and Jamei, 1985, Sheffi et al., 1982). Some researchers link geographic or real-time information systems with simulation models (Franzese and Joshi, 2002, Pidd et al., 1996). Further studies evaluate other methods that can be used to identify evacuation routing plans in road networks, such as the network flow model by Cova and Johnson (2003) or the use of contraflow segments of the interstate freeway by Wolshon (2001). Fewer studies have been involved with the issue of building evacuation.

There are a number of reasons why the emergency evacuation of a building may be necessary. One of the most compelling reasons is the threat of smoke or fire may require evacuation of a building. Other reasons may include the threat of an earthquake, a toxic or natural gas leak, a power blackout, elevator failure, a bomb threat, and civil defense emergencies. Large buildings undergo practice evacuations on a regular basis. It is understandable to plan evacuations in advance such that practice evacuations and, ultimately, actual evacuations will be successful (Chalmet, Francis, & Saunders, 1982).

A particularly difficult evacuation process involves high-rise buildings which can accommodate large amounts of people and have long vertical transport distances. In case of an emergency, occupants need time to escape from their current floor in the building to a safe place. The compelling question here is how long is the evacuation time of the occupants in these high-rise buildings? Accurate data on the evacuation time for occupants in a high-rise building are difficult to acquire because an investigation during a real emergency will endanger the occupants of the building. Fire drills serve as an alternative approach to simulate the real situation of a fire. Nevertheless, information acquired in such drills cannot incorporate the complex behavioral reaction of evacuees. Moreover, the arrangement for an evacuation exercise in a large building is difficult.

Some recent articles have discussed emergency preparedness in healthcare facilities as a result of a wide variety of disasters such as hurricanes (Castro et al., 2008, Gray and Hebert, 2007, Hyer et al., 2009), tornados (Lewis, 2007), wildfires (Barnett, Dennis-Rouse, & Martinez, 2009), earthquakes (Schultz, Koerig, & Lewis, 2003), and bomb threats (Augustine & Schoettmer, 2005). Emergency planning in hospitals is particularly important due to the risk to the lives of the patients. While most of the emergency response plans focus on a hospital being able to accommodate the input of patients resulting from some type of a disaster situation, there are few studies that are concerned with the issues that a hospital faces when their occupants must be evacuated (Taaffe, Kohl, & Kimbler, 2005). An evacuation process in a hospital is a particularly difficult and complex task that requires a strategy, well-trained staff, and careful execution.

Due to the complexities involved in hospitals and in other buildings, numerical simulation can be employed as an alternative approach for studying the evacuation problem. Gwynne, Galea, Owen, Lawrence, and Filippidis (1999) report that scientists and architectural engineers using high-speed digital computers have developed numerous different building evacuation models. One simulation model entitled EVACSIM (Drager et al., 1992) attempts to measure the performance of the evacuation system under conditions as realistic as possible, including human behavior and the possibility of accidents. Some of the simulation models that have been developed can successfully simulate the process of evacuation in low-rise buildings with limited populations (Lo, Fang, & Chen, 2001).

Other simulation models focus directly on the means of egress, such as exits that are used during evacuation. A simulation model called MOBILIZE (Weinroth, 1989) considers the evacuation of a complex building with thousands of people on a large campus. This model considers different evacuation patterns and total exit times with alternative occupancy levels. While attempting to reduce the variance of the total numbers of occupants who exit through individual doorways, Bakuli and MacGregor Smith (1996) study the effect of circulation widths on throughput during evacuation. Choi’s (1991) combined analytic and simulation model evaluates evacuation congestion effects by including branching rules as people come to a decision point in the egress network. Tayfur and Taaffe (2009) consider the evacuation of hospital patients who have to compete with the general population for transportation resources including vehicles and routes.

While simulation models are capable of analyzing the evacuation processes and estimating the evacuation time, building simulation models are costly and time consuming. The requirements of simulation modeling may include such expenses as purchasing simulation software (for example, Arena Basic Edition costs several thousands of dollars) and using simulation experts to help with various aspects of the modeling process (generally an expensive resource). In addition, simulation is a time consuming process that includes such functions as model development, testing and validation, data gathering, and data interpretation. Even simple models even take months to complete. In addition, these models have an overreliance on the specific layout and conditions of the building.

Due to the problems and complexities of using simulation modeling to study building evacuations, we have developed a quantitative prediction model. Our prediction model is applied to a hospital building in order to estimate evacuation times. In this paper, the evacuation time results from the model for 19 different hospital evacuation scenarios are compared with the results of a previously designed simulation model. While this work specifically focuses on evacuation, the methodology can also be extended for other types of surge capacity analysis.