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Achieving better health outcomes for patients and populations requires a focus on continuous quality improvement (QI). While physicians pride themselves on being subject matter experts in their focused area of medical practice, such knowledge alone is insufficient to produce fundamental changes in the delivery of health care. Physicians who practice in complex hospital and health care systems must acquire another kind of knowledge in order to develop and execute change.

W. Edwards Deming, an American statistician and professor who is widely credited with improvement in manufacturing in the United States and Japan, has described this knowledge as a “system of profound knowledge” (Figure 21-1). This knowledge is composed of the following items: appreciation for a system, understanding variation, building knowledge, and the human side of change. These concepts are just beginning to be taught to health care professionals and are essential for anyone who wishes to improve the health care delivery system.

Figure 21-1

Deming’s System of Profound Knowledge. (Reproduced, with permission, from Langley GJ, et al. The Improvement Guide: A Practical Approach to Enhancing Organization Performance, 2nd ed. San Francisco, CA: Jossey-Bass; 2009.)

All hospitalists have witnessed changes that did not result in fundamental improvements within their hospital systems: the computerized order set that was successfully implemented but never revised based on prescribers’ feedback, the paper checklist for medication reconciliation that never gets filled out, or the new rounding system that worked for the first few weeks but then failed to become a standard part of practice due to physician variation or lack of commitment. These are all examples of first-order changes—changes that ultimately returned the system to the normal level of performance. In quality improvement work, individuals must strive for second-order changes, which are changes that truly alter the system and result in a higher level of system performance. Such changes impact how work is done, produce visible, positive differences in results relative to historical norms, and have a lasting impact. Although the model for improvement described below may seem simple, it is actually quite demanding when used properly; and the process is essential to both learning and ultimately changing complex systems.


The Plan-Do-Study-Act (PDSA) model is a commonly used method in quality improvement. Shewart and Deming described the model many years ago when they studied quality in other industries. This model first appeared in health care when Berwick described how the tools could be applied using an iterative approach to change. Using a “test-and-learn approach” in which a hypothesis is tested, retested, and refined, the PDSA cycle allows for controlled change experiments on a small scale before expansion to a larger system. The four repetitive steps of PDSA—plan, do, study, and act—are carried out until fundamental ...

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