The purpose of this paper is to demonstrate that Lean principles and methodology should be applied on a regular basis to the entire process flow of healthcare delivery systems. With reference to an actual case-based research, this article demonstrates how patient flows can be successfully optimized if Lean is not limited to single processes/contexts only, and it is applied to achieve holistic process improvement of an entire system. The complexity of healthcare delivery systems requires inclusive investigation from various points of view. This is why case-study-based research has been used to investigate dynamic, experiential and complex processes and areas, such as the ones featured by this article. The methodological basis for this research has been a twelve-step optimization approach outlined by the authors during a previous successful Lean programme. This same approach has been applied to optimize patient flows in the emergency departments of four different hospitals in Northern Italy. The research has involved teams composed of medical, nursing, technical and administrative staff.The results outlined in the article suggest that inclusive application of Lean tools leads to effective process optimization and a better working environment, when in connection with a systematic and holistic optimization approach. Feedback from participants was obtained through a satisfaction survey and a project assessment; it reported enthusiastic project acceptance and good teamwork climate. Among the results of the research performed in the four hospitals, several measures have been effectively implemented to reduce the lead-time for patients from registration to discharge. At the same time, patient-staff ratio and quality of care have been either maintained or even improved. However, lack of a definite conclusive evaluation can be explained by the research project still being implemented.The value of this paper lies in demonstrating how Lean contributes to achieve better process performance and high staff satisfaction, when implemented within the whole supply chain of a healthcare delivery system on a regular basis
