Reason’s Swiss cheese model

FIGURE 52.1 The use of Reason s Swiss cheese model of accident causation for the management of medical equipment risk. (Adapted from Reason, J. 2000. British Medical lournah 320 768-770,18 March.)... 

It has a sound theoretical basis, being derived from a proven accident analysis tool. Reason s Swiss Cheese Model is now a familiar concept in numerous industries, which enables this derivative process to be readily explained to users. 

The associations of distinct detection mechartisrrts to differerrt types of errors led Thomas to propose an organic approach according to which variability in performance and human error requires parallel defense strategies and an adaptive approach and not the traditional serial protective layers as illustrated by Reason s Swiss Cheese Model. 

The systems approach seeks to identify situations or factors likely to contribute to human error. James Reason s analysis of industrial accidents revealed that catastrophic safety failures almost never result from isolated errors conunitted by individuals. Most incidents result from smaller and multiple errors in components and environments with underlying system flaws. Reason s Swiss Cheese Model describes this phenomenon. Errors made by individuals can result in disastrous consequences due to flawed systans that are represented by the holes in the cheese. Reason believed human error would happen in complex systems. Striving for perfection or punishing individuals who make errors does not appreciably improve safety. A systems approach stresses efforts to catch or anticipate human errors before they occur. Reason used the terms active errors and latent errors to distinguish individual errors from system errors. Active errors almost always involve frontline personnel. They occur at the point of contact between a human and some element of a larger system. Latent errors occur due to failures of the organization or designs that allow inevitable active errors to cause harm. The terms sharp end and blunt end correspond to active error and latent error. The systems approach provides a framework for analysis of errors and efforts to improve safety. 

Simple accident sequence (adapted from James Reason s Swiss Cheese Model (Reason, 1997). 

The effective management of medical equipment-related risk requires a meaningful and practical framework or paradigm from which to start. As described here. Reason s modified Swiss cheese model provides one such paradigm. Metaphorically and conceptually, the model also tends to be readily understood, which further aids in its acceptance as a risk management tool. 

Figure 4.1 also illustrates the additive nature of a job s safety risks. That is, added safety risks associated with each factor cumulatively increase the job s overall safety risk. The additive nature of risk is well captured by Reason s (1990) Swiss cheese safety model. Each factor represents a risk layer, and the probability of an accident increases as the number of risk layers increases. Where possible a job which a new employee is entering should be striped of as many risk layers as possible. As will be discussed below, more senior employees, who are experienced, are likely to be better able to cope with job risks which are difficult or impossible to remove. 

Table 2.1 shows examples of how the elements of an accident fit together. Reading the table from left to right, you can see how an accident evolves. First, there is a hazardous condition—such as large quantities of flammable liquids. Then the initiating event occurs—for example, a valve sticks open. The effect of a valve-failed-open propagates a pressure rise in the system. Now, an in-line relief valve can mitigate the effects of the initial event. If not, an accident ensues—explosion. Chapter 11 discusses and details the events that lead to an accident. It also discusses James Reason s famous Swiss cheese accident model. 

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