Intended for healthcare professionals

Education And Debate

System changes to improve patient safety

BMJ 2000; 320 doi: (Published 18 March 2000) Cite this as: BMJ 2000;320:771
  1. Thomas W Nolan (, statistician
  1. Associates in Process Improvement, 1110 Bonifant Street, Silver Spring, MD 20910, USA

    The automated teller machine that dispenses cash and other banking transactions has become ubiquitous in many parts of the world. Most machines follow one of two sequences to complete a transaction. Some dispense the money first and then return the card. Others reverse these two steps. Since the aim of the transaction is to obtain the money, common sense and research in human factors predict that the person using the machine is more likely to forget the card if it is returned after the money is dispensed.1 The order is designed into the system and produces a predictable risk of error.

    Researchers have documented the extent of errors and their effect on patient safety. 2 3 Like the card forgotten at the automated teller machine, many of the adverse events resulted from an error made by a person who was capable of performing the task safely, had done so many times in the past, and faced significant personal consequences for the error. Although we cannot change the aspects of human cognition that cause us to err, we can design systems that reduce error and make them safer for patients.4 My aim here is to outline an approach to designing safe systems of care based on the work of human factors experts and reliability engineers.

    Summary points

    Many errors are attributable to characteristics of human cognition, and their risk is predictable

    Systems can be designed to help prevent errors, to make them detectable so they can be intercepted, and to provide means of mitigation if they are not intercepted

    Tactics to reduce errors and mitigate their adverse effects include reducing complexity, optimising information processing, using automation and constraints, and mitigating unwanted effects of change

    Strategies for the design of safe systems of care

    Designers of systems of care can make them safer by attending to three tasks: designing the system …

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