Background Waiting time for physician attention is considered emergency care–sensitive, but still many emergency departments (EDs) attend their patients outside of the standard recommended. Objectives The objective of this research is to make a contribution for managing continuous improvement in EDs based on providing fast feedback using a new normalized variable named vulnerability. Methods This research has analyzed the levels of census, efficiency and vulnerability with which an ED works. The data set contains information regarding 53,175 individuals attended in an ED in Chile during 2013. A regression model was conducted to explain vulnerability. In order to carry out the analysis census, efficiency and vulnerability variables were calculated for each patient attended. The model has explained 63% of vulnerability. Results 40% of ED patients were attended after the wait time recommended by ESI and with efficiency levels lower than 40%. According to our results, efficiency, census, diagnostic track and months explain vulnerability. Conclusions This study allows us to manage EDs by using a new variable named vulnerability. Vulnerability provides fast feedback for healthcare professionals in order to develop a continuous improvement policy. This could increase professional commitment for continuous improvement and therefore decrease morbidity and mortality in any ED.