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Understanding adverse events: human factors.
  1. J Reason
  1. Department of Psychology, University of Manchester, UK.


    (1) Human rather than technical failures now represent the greatest threat to complex and potentially hazardous systems. This includes healthcare systems. (2) Managing the human risks will never be 100% effective. Human fallibility can be moderated, but it cannot be eliminated. (3) Different error types have different underlying mechanisms, occur in different parts of the organisation, and require different methods of risk management. The basic distinctions are between: Slips, lapses, trips, and fumbles (execution failures) and mistakes (planning or problem solving failures). Mistakes are divided into rule based mistakes and knowledge based mistakes. Errors (information-handling problems) and violations (motivational problems) Active versus latent failures. Active failures are committed by those in direct contact with the patient, latent failures arise in organisational and managerial spheres and their adverse effects may take a long time to become evident. (4) Safety significant errors occur at all levels of the system, not just at the sharp end. Decisions made in the upper echelons of the organisation create the conditions in the workplace that subsequently promote individual errors and violations. Latent failures are present long before an accident and are hence prime candidates for principled risk management. (5) Measures that involve sanctions and exhortations (that is, moralistic measures directed to those at the sharp end) have only very limited effectiveness, especially so in the case of highly trained professionals. (6) Human factors problems are a product of a chain of causes in which the individual psychological factors (that is, momentary inattention, forgetting, etc) are the last and least manageable links. Attentional "capture" (preoccupation or distraction) is a necessary condition for the commission of slips and lapses. Yet, its occurrence is almost impossible to predict or control effectively. The same is true of the factors associated with forgetting. States of mind contributing to error are thus extremely difficult to manage; they can happen to the best of people at any time. (7) People do not act in isolation. Their behaviour is shaped by circumstances. The same is true for errors and violations. The likelihood of an unsafe act being committed is heavily influenced by the nature of the task and by the local workplace conditions. These, in turn, are the product of "upstream" organisational factors. Great gains in safety can ve achieved through relatively small modifications of equipment and workplaces. (8) Automation and increasing advanced equipment do not cure human factors problems, they merely relocate them. In contrast, training people to work effectively in teams costs little, but has achieved significant enhancements of human performance in aviation. (9) Effective risk management depends critically on a confidential and preferable anonymous incident monitoring system that records the individual, task, situational, and organisational factors associated with incidents and near misses. (10) Effective risk management means the simultaneous and targeted deployment of limited remedial resources at different levels of the system: the individual or team, the task, the situation, and the organisation as a whole.

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