"No Room at the Emergency Room: Causes and Consequences" was presented by Linda Green, an operations researcher who is the Armand G. Erpf Professor of the Modern Corporation at Columbia Business School. Co-authors are Sherry Glied, M. Grams, and Natalia Yankovic of Columbia University.

"Emergency room overcrowding and ambulance diversions aren't just inconvenient for patients," says Prof. Green. "This research shows that delaying treatment to people suffering ailments or injuries that require immediate care can cost them their lives."

Patients who try to access a hospital emergency room during a time of ambulance diversion may experience additional delays not only due to the increased travel time associated with going to a more distant hospital, but also because this increased time translates into longer response times to calls for ambulances. In addition, the research showed that when one hospital is on diversion, there is an increased likelihood that other hospitals are on diversion and so emergency rooms are generally busier. So when the patient arrives to an emergency room, the wait to be seen by a physician and receive care is likely to be longer.

The authors studied data collected in all five boroughs of New York City in 1999 and 2000. They found a significant association between time on ambulance diversion and increased mortality resulting from acute myocardial infarction (AMI). Each additional borough-hour of ambulance diversion was associated with a 2.9 to 3.8% increase in AMI outpatient deaths. Days which had an incidence of gridlock, which was defined as at least 25% of hospitals in a borough being on diversion simultaneously, were associated with a 14.1 to 15.7% increase in AMI outpatient deaths.

In effect, an additional "borough-day" of gridlock was associated with a 39.0 to 68.4% increase in AMI outpatient deaths. As a result, there were between 201 and 390 additional AMI deaths during the study period associated with ambulance diversions.

Although health care observers have long assumed that ambulance diversion was associated with serious medical consequences for patients with serious illness or injury, Prof. Green and her colleagues are the first to document a connection between ambulance diversion and an increased number of deaths. The authors chose to focus on heart attack deaths because of the critical nature of providing rapid care during the "Golden Hour" and the availability of data. They used operations research and statistical techniques to reach their conclusions.

The authors examined data about all 9,743 adult patients who died of myocardial infarctions in New York during the study period of January 2, 1999, to December 31, 2000. Diversion status data from 58 New York hospitals was obtained from the New York City Fire Department.

These findings differ from previously published results, which showed no increase in transport-related deaths over a concomitant period of increasing ambulance diversion. Unlike previous studies, the authors' primary outcome measure was deaths from myocardial infarction, a smaller and more sensitive subset of patients. The analysis included all deaths within a day occurring either in the emergency department or outside a hospital setting, rather than solely those that occurred during transport. This inclusion may capture deaths that occurred after the time of transport but which were nonetheless associated with the degree of emergency department crowding.

The findings suggest that ambulance diversion may have serious consequences for other emergency patients, as well.

Prof. Green delivered the paper last month at the INFORMS annual meeting in Washington, DC.

The INFORMS website is http://www.informs.org/.