Management by constraints: Considering patient volume when adding medical staff to the emergency department

Zeev Rotstein*, Rachel Wilf-Miron, Bruno Lavi, Daniel S. Seidman, Poriah Shahaf, Amir Shahar, Uri Gabay, Shlomo Noy

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Background: The emergency department is one of the hospital's busiest facilities and is frequently described as a bottleneck. Management by constraint is a managerial methodology that helps to focus on the most critical issues by identifying such bottlenecks. Based on this theory, the benefit of adding medical staff may depend on whether or not physician availability is the bottleneck in the system. Objective: To formulate a dynamic statistical model to forecast the need for allocating additional medical staff to improve the efficacy of work in the emergency department, taking into account patient volume. Methods: The daily number of non-trauma admissions to the general ED was assessed for the period 1 January 1992 to 1 December 1995 using the hospital computerized database. The marginal benefit to shortening patient length of stay in the ED by adding a physician during the evening shift was examined for different patient volumes. Data were analyzed with the SAS software package using a Gross Linear Model. Results: The addition of a physician to the ED staff from noon to midnight significantly shortened patient LOS: an average decrease of 6.61 minutes for 80-119 admissions (P < 0.001). However, for less than 80 or more than 120 admissions, adding a physician did not have a significant effect on LOS in the ED. Conclusions: The dynamic model formulated in this study shows that patient volume determines the effectiveness of investing manpower in the ED. Identifying bottleneck critical factors, as suggested by the theory of constraints, may be useful for planning and coordinating emergency services that operate under stressful and unpredictable conditions. Consideration of patient volume may also provide ED managers with a logical basis for staffing and resource allocation.

Original languageEnglish
Pages (from-to)170-173
Number of pages4
JournalIsrael Medical Association Journal
Issue number3
StatePublished - 2002
Externally publishedYes


  • Emergency department
  • Length of stay
  • Management by constraints
  • Patient volume


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