Ambulance diversion not an effective way to control emergency department crowding

Massachusetts' 2009 ban on ambulance diversion not only did not increase emergency department length of stay or ambulance turnaround time but may actually have led to improvements in both areas, according to a study published online today in Annals of Emergency Medicine ("The Effect of an Ambulance Diversion Ban on Emergency Department Length of Stay and Ambulance Turnaround Time").  

"Our study supports what we have been hearing from emergency physicians anecdotally since the ban was put into effect," said Laura G. Burke , MD, MPH, of Beth Israel Deaconess Medical Center in Boston, Mass.  "It also supports the view that diversion is not an effective way to control emergency department crowding. Hospital-wide operational changes likely contributed significantly to the ban's apparent success."

Researchers evaluated nine Boston-area hospital emergency departments before and after the ban was issued in 2009.  The hospitals in the study accounted for the majority of emergency department visits in Boston and Cambridge. Emergency department length of stay was the measure for crowding. 

None of the emergency departments studied experienced increased in length of stay for admitted or discharged patients and there was no increase in ambulance turnaround time, despite an increase in volume for several of the studied emergency departments.  Overall, emergency department volume increased by 3.6 percent but length of stay decreased by 10.4 minutes for admitted patients and ambulance turnaround time decreased by 2.2 minutes.

Researchers had theorized that if ambulance diversion was effective in mitigating crowding, hospitals with high rates of diversion would show a relatively greater increase in emergency department length of stay after the ban.  However, after the ban went into effect they found no difference in length of stay between hospitals with high rates of diversion and hospitals with low rates of diversion.

"We think that concerted efforts by hospitals to make the operational changes necessary to improve patient flow through the hospital from the emergency department helped make the ban a success," said Dr. Burke. "If our findings are confirmed by other studies, then other geographic areas may enjoy similar success to what we have seen in Boston."