Health Policy/Concepts
A conceptual model of emergency department crowding*,**

https://doi.org/10.1067/mem.2003.302Get rights and content

Abstract

Emergency department (ED) crowding has become a major barrier to receiving timely emergency care in the United States. Despite widespread recognition of the problem, the research and policy agendas needed to understand and address ED crowding are just beginning to unfold. We present a conceptual model of ED crowding to help researchers, administrators, and policymakers understand its causes and develop potential solutions. The conceptual model partitions ED crowding into 3 interdependent components: input, throughput, and output. These components exist within an acute care system that is characterized by the delivery of unscheduled care. The goal of the conceptual model is to provide a practical framework on which an organized research, policy, and operations management agenda can be based to alleviate ED crowding. [Ann Emerg Med. 2003;42:173-180.]

Introduction

Emergency department (ED) crowding has become a major barrier to receiving timely emergency care in the United States. Patients who present to EDs often face long waiting times to be treated and, for those who require admission, even longer waits for an inpatient hospital bed. Because ED crowding is a reflection of larger supply and demand mismatches in the health care system, the problem cannot be solved by examination of the ED in isolation. To find solutions, we must examine ED crowding in the context of the entire delivery system by using reliable methods to understand, measure, and monitor system capacity.

We present a conceptual model of ED crowding to help administrators, researchers, and policymakers understand its causes and develop potential solutions. The conceptual model partitions ED crowding into 3 interdependent components: input, throughput, and output. Although factors that originate in many parts of the health care system contribute to ED crowding, the model focuses on this problem from the perspective of the ED. We do not intend to describe all the potential causes of this complex issue. Rather, our goal is to provide a framework that will facilitate a systematic understanding of the problem. After discussing a definition of ED crowding and the overall acute care system, we present the model's components and describe how it could guide research and operational and policy solutions for ED crowding.

The lack of consensus definitions of ED crowding has been a challenge for researchers, clinicians, administrators, and policymakers.1, 2 In 2002, the American College of Emergency Physicians assembled the Crowding Resources Task Force to develop a guide to help American College of Emergency Physicians chapters respond to the problem. The task force developed the following definition of ED crowding, which we have adopted for this article.

Emergency department crowding: A situation in which the identified need for emergency services outstrips available resources in the ED. This situation occurs in hospital EDs when there are more patients than staffed ED treatment beds and wait times exceed a reasonable period. Crowding typically involves patients being monitored in nontreatment areas (eg, hallways) and awaiting ED treatment beds or inpatient beds. Crowding may also involve an inability to appropriately triage patients, with large numbers of patients in the ED waiting area of any triage assessment category.3

Other authors have offered potential definitions of ED crowding and described factors that are most likely to contribute to the problem. Schull et al2 used an expert panel to identify factors that were deemed key determinants of ED crowding. They developed a conceptual model of ED crowding that grouped potential causes of crowding into 4 areas: community, patient, ED, and hospital determinants. This group identified ambulance diversion as the most useful operational definition and proxy measure of ED crowding; however, because ambulance diversion is not an option for many hospitals, and because EDs have widely variable thresholds for diverting ambulances, we decided that this definition is not generalizable to ED crowding in the United States. Schull et al also excluded factors such as the availability of primary care in the community as an important determinant of ED crowding. However, their study was based on the Canadian health care system, where universal access to primary care is the norm. Our goal is not to prioritize potential causes of ED crowding but to provide a general conceptual framework that can be used to study the causes and consequences of ED crowding, as well as potential solutions.

Section snippets

The acute care system

The input-throughput-output conceptual model applies operations management concepts to patient flow among health care sites that we refer to as the acute care system. We broadly define the acute care system to include any delivery system component that provides unscheduled care (Figure 1).

. The acute care system includes the components of the health care system that contribute to, or are affected by, ED crowding. The common link among these services is that they are delivered as unscheduled care.

Input component

The input component of ED crowding in our conceptual model includes any condition, event, or system characteristic that contributes to the demand for ED services. This portion of the conceptual model has properties that are similar to existing models of health care use. For example, Andersen and Laake's4 Behavioral Model of Healthcare Utilization describes 3 factors that affect use: patient need for health care services, predisposing factors that affect an individual's likelihood of seeking

Throughput component

The throughput component of the model identifies patient length of stay in the ED as a potential contributing factor to ED crowding. This part of the model highlights the need to look internally at ED care processes and modify them as needed to improve their efficiency and effectiveness, especially those that have the largest effect on length of stay and resource use in the ED. There are 2 primary throughput phases in the model. The first phase includes triage, room placement, and the initial

Output component

Inefficient disposition of ED patients contributes to crowding for admitted and discharged patients.8 The most frequently cited reason for ED crowding is the inability to move admitted patients from the ED to an inpatient bed.8, 19, 22, 23, 24, 25 This problem forces the ED to board admitted patients until inpatient beds are available, effectively reducing the ED's capacity to care for new patients. Boarding of inpatients in the ED has also been cited as the most important determinant of

A model-driven research, policy, and operations management agenda

The input-throughput-output conceptual model of ED crowding may be useful for organizing a research, policy, and operations management agenda to alleviate the problem. The model illustrates the need for a systems approach with integrated rather than piecemeal solutions for ED crowding. We believe there are 4 general areas of ED crowding that require future research. First, we must develop measures of ED crowding that are valid, reliable, and sensitive to changes throughout time. Second,

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    *

    Supported by contract number 290-00-0015 from the Agency for Healthcare Research and Quality. The views in this paper are those of the authors. No official endorsement by the Agency for Healthcare Research and Quality or the Department of Health and Human Services is intended or should be inferred. Dr. Asplin's work was supported by grant number K08-HS13007 from the Agency for Healthcare Research and Quality.

    **

    Reprints not available from the authors.

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