Nearly 114 mln visits were made to US emergency departments in 2003 according to the Centers for Disease Control and Prevention (CDC). On an average day, there were more than 300,000 visits to an emergency department in the US compared to a decade ago; annual visits to emergency departments grew by 24 mln, an increase of 26%, while the number of EDs in the US decreased by 14% during the same period. The average length of stay for an emergency department visit in 2003 was 3.2 hours and in over 700,000 visits, the length of visit to the emergency department exceeded 24 hours. For 1.7% of emergency department visits, patients left the hospital prior to being seen which represents potential patient satisfaction and safety issues. In 2003, 13.9% of emergency department visits resulted in the patient being admitted to the hospital for further treatment and in 1.6% of visits, patients were admitted to the intensive care unit (ICU) or critical care unit or to 23-hour observation. Typically, the ED can represent 40% or more of all hospital admissions.