Study Reveals Heaviest Users of Ambulance Transport

Washington, DC– Patients with Medicare or Medicaid, the uninsured, the elderly and the critically ill are the heaviest users of ambulances for transport to the emergency department, making them most vulnerable during periods of ambulance diversion.   The results of a study of more than 30,000 patients taken to emergency departments by ambulance were published online Friday in Annals of Emergency Medicine (“At-Risk Populations and the Critically Ill Rely Disproportionately on Ambulance Transport to Emergency Departments”).
“The most surprising and somewhat disturbing finding in our study was close to half of critically ill patients come to the ER on their own, without ambulance transport,” said lead study author Benjamin Squire, MD, of Harbor-UCLA Medical Center in Los Angeles. “It has shed a whole new light on how dangerously ill some of the patients in the waiting room are. When a patient comes to the emergency department by ambulance, he is being monitored continually, which is not the case for a patient coming in on his own. This finding changed my view of triage.”
Only 57 percent of critically ill patients (defined as intubated, dying later in the emergency department, or transferred from the emergency department directly to the cardiac catheterization lab, ICU or surgery) went to the emergency department by ambulance. Among the critically ill, privately insured patients were less likely to rely on ambulance transport than those with Medicare, public insurance or no insurance. In the overall population, ambulance use did not vary with race and ethnicity, although among the critically ill, Latinos were least likely to arrive by ambulance.
Patients insured by Medicare were approximately three times more likely to come to the emergency department by ambulance than those with any other form of insurance. Nearly half of all patients older than 74 years came to the emergency department by ambulance.
“This trend in the general population suggests that demand for ambulance transport will increase substantially as the population ages,” said Dr. Squire. “The proportion of U.S. residents age 65 and older is expected to increase to 16 percent by the year 2020. The increasing demands on ambulance transport and emergency departments from an aging population indicate that ambulance diversion is likely to worsen and the elderly will be most affected.”
Approximately 500,000 ambulances are diverted away from the closest emergency department every year.
“Further study on the effects of ambulance diversion on patients is warranted,” said Dr. Squire. “Our findings about critically ill patients who come to the ER on their own also support putting a highly trained provider in the waiting room who can accurately identify patients with high-risk emergency conditions that may not be obvious at triage.”
Annals of Emergency Medicine is the peer-reviewed scientific journal for the American College of Emergency Physicians, a national medical society. ACEP is committed to advancing emergency care through continuing education, research, and public education. Headquartered in Dallas, Texas, ACEP has 53 chapters representing each state, as well as Puerto Rico and the District of Columbia. A Government Services Chapter represents emergency physicians employed by military branches and other government agencies. For more information visit

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