Health policy and clinical practice/original research
Analysis of Ambulance Transports and Diversions Among US Emergency Departments

https://doi.org/10.1016/j.annemergmed.2005.12.001Get rights and content

Study objective

We describe emergency department (ED) visits in which the patient arrived by ambulance and estimate the frequency of and reasons for ambulance diversion. Using information on volume of transports and probabilities of being in diversion status, we estimate the number of patients for whom ED care was delayed because of diversion practices.

Methods

Data from the 2003 ED component of the National Hospital Ambulatory Medical Care Survey, an annual sample survey of visits to US hospital EDs, were used for the analysis. Data were provided by 405 participating EDs on 40,253 visits. Data from supplemental questionnaires to the hospital staff were used to describe volume and frequency of ambulance diversions.

Results

In 2003, patients arrived by ambulance for 16.2 million ED visits (14.2%). About 31 ambulances arrived at a US ED every minute. Of ambulance-related visits, 39% were made by seniors, 68% were triaged as emergent or urgent, and 37% resulted in hospital-admission. About 45% of EDs reported diverting ambulances at some point during the previous year. Among EDs that had any diversion, approximately 3% of operating time was spent in diversion status. In 2003, an estimated 501,000 ambulances were diverted, ie, 1 ambulance diversion per minute. Large EDs represent 12% of all EDs, 35% of all ambulance arrivals, 18% of all EDs that went on diversion, 47% of all hours spent in diversion status, and 70% of all ambulances diverted to another ED.

Conclusion

Description of current use of ED ambulance transports and likelihood of diversions should help policymakers plan for demographic changes in the population during the next 15 years.

Introduction

In 2003, there were approximately 114 million emergency department (ED) visits in the United States, which was the highest visit volume ever reported.1 From 1993 to 2003, the number of ED visits rose by 26%, whereas the number of EDs decreased by 12%.1 This increasing demand for ED services, coupled with fewer operating EDs, leads to higher visit volumes in those remaining open, which can overwhelm ED resources, as well as other parts of the hospital system. When EDs lack the capacity to provide emergency care for patients requiring treatment or admission, they commonly divert ambulances to other hospitals.2 Another consequence of ED crowding includes emergency medical services (EMS) providers remaining with the patient until the ED staff has room to handle the case. This affects the entire EMS system by tying up EMS resources, reducing response time, delaying patient care, and creating conflict with ED staff. The health of the community is also affected by ambulance diversion in that the capacity of the ED to respond to infectious disease outbreaks, natural disasters, and terrorist attacks is reduced.

About 14% of ED patients arrive by air or ground ambulance transport.1 Such patients tend to be older than the average ED patient 1 and likely require more resources, ranging from diagnostic tests performed and treatment provided to total time spent in the ED. Understanding how emergency care is organized and delivered, how well transitions from EMS to ED work, and the extent of resources required by ambulance cases is important for gauging not only future ED needs but also EMS services. Little has been published on national estimates of resources involved in ED transport cases. There is no national EMS database, and no national estimates exist for the frequency of ambulance diversions.

In this study, we used data from the ED component of the 2003 National Hospital Ambulatory Medical Care Survey (NHAMCS) to describe the characteristics of patients transported by ambulance and the extent of resources used in their ED care. We also used supplemental survey data from the NHAMCS to describe the magnitude of ambulance diversion episodes nationwide. Using the volume of transports and the frequency and duration of diversion, we estimated, by modeling, the number of ambulances that were likely diverted in US hospitals during 2003.

Section snippets

Study Design

The NHAMCS is an annual probability sample survey of US hospital EDs and outpatient departments. It was first conducted in 1992 by the Centers for Disease Control and Prevention’s (CDC’s) National Center for Health Statistics (NCHS). The US Census Bureau is responsible for field operations and data collection. The NHAMCS uses a 4-stage probability sampling procedure: (1) 112 geographic primary sampling units; (2) probability sample of nonfederal, short-stay, or general hospitals with EDs or

Analysis of ED Visit Data on Ambulance Transports

In 2003, there were 16.2 million ED visits (14.2%) in which the patient arrived by ambulance; this figure corresponds to 44,300 per day and 1,800 per hour. The peak time of arrival for ambulance transports was 10 am to 1 pm, with a smaller peak occurring from 5 pm to 7 pm (Figure 1). The majority of patient visits were for illness (59.3%), whereas 40.7% were for injury, poisoning, or adverse effects of medical treatment. Although the rate for all ambulance arrivals was fairly consistent across

Limitations

The limitations of the portion of the study describing ambulance transports are that data are not collected on out-of-hospital EMS care or on whether multiple patients arrive in the same ambulance, so it is assumed that each arrival is a different ambulance transport. For the ambulance diversion section of the article, there are limitations of the estimates provided, and there is no standard definition of diversion. The estimate of the volume of ambulances diverted is conservative because there

Discussion

This report describes the magnitude and frequency of ambulance transports and diversions at US EDs. Although mode of arrival to the ED was collected and reported from the 1999 and 2000 NHAMCS, it did not receive wide attention, even though NHAMCS data represent the only national estimate of ambulance transports to the ED. The relative proportion of ED visits in which the patient arrived by ambulance remained constant from 1999 to 2003 (14.2%)1, 7; however, the number of arrivals increased from

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Supervising editor: Brent R. Asplin, MD, MPH

Author contributions: CB conceived the study. CB and LM designed the study. RV edited the data. CB, LM, and RV performed the analysis. CB and LM wrote the article. CB takes responsibility for the paper as a whole.

Funding and support: The authors report this study did not receive any outside funding or support.

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