Emergency department crowding: old problem, new solutions.

Emergency department (ED) crowding is becoming an increasing problem in EDs throughout the United States for a multitude of reasons, including an increase in patient volume and a decrease in available EDs. Crowding has an adverse impact on the ability to deliver quality and timely care and may contribute to adverse patient outcomes. Conceptually, factors that contribute to ED crowding can be divided into three domains, which correspond to their "sites of action": input, throughput, and output. A number of measures have been developed to better quantify crowding and its effects. More research needs to be done to better understand the factors that contribute to crowding, the impact of this problem on patients and ED throughput, and how to alleviate this nationwide crisis.