Annex 2: Patient Safety: State of the Art
1.1 James Reason’s “Swiss Cheese Model”
The human factor, defined as “the study of the interrelationships between humans, the tools they use, and the environment in which they live and work”,38 is one major factor behind accidents (among others such as material defect, environmental variations etc.).
The aviation sector pioneered in research to understand accidentsxviii and invested hugely to understand the human factor. Until serious investigations and research were undertaken, accidents were imputed to the pilot.
Scientific analysis and observation enabled researchers to understand that plane accidents, 70% to 80% of which are attributable at least partly to human error,39 are mostly the end result of a series of causes, with the unsafe acts by the crew only the last.40 Consequently, prevention measures could be imagined at various levels, which have had a significant effect on the number of accidents and fatalities since the 1970s. Air travel is now one of the safest forms of transportation.xix
xviii A specialized agency of the United Nations, the International Civil Aviation Organisation (ICAO) was even created in 1944 to promote the safe and orderly development of international civil aviation throughout the world. See http://www.icao.int/Pages/default.aspx Accessed on September 17, 2018.
xix According to a report of Allianz Insurance company, although the air traffic has constantly grown, in 1959 the chance to have a fatal accident was 1 every 25’000 departure (USA & Canada) and in 2015 is 1 on
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James Reason, a psychologist, is one of those researchers whose work on human error remains an important reference in the area of safety.41 With his observations and reflections on possible causes explaining the genesis of errors committed by front‐line workers, he initiated a real paradigm shift in the understanding of human error. Human errors are not necessarily the result of a lack of ability on the part of front‐line workers;
they may also be the culmination of a series of prior errors (at the management level, in the maintenance processes etc.)
Starting by clarifying the separation between intentional and non‐intentional actions,42 he made the distinction between what he designated as active errors and latent errors. Active errors are those whose effects are in direct relation to the occurrence of the adverse event and are committed by the front‐line actor. Latent errors are those whose contributing factors are lying dormant within the system. Such errors are committed by people who are likely unaware that they are participating in a process that will result in an accident.
In a production process, various human errors, even very small, can contribute (contributing factors), each at its own level, to the occurrence of the accident. However, each error alone is not necessarily sufficient, by itself, to cause the accident.
Reason offers also a differentiation between various types of human error: slips (errors made under the influence of fatigue, stress or distraction), lapses (memory error) and mistakes (“deficiency or failure in the judgemental and/or inferential processes involved in the selection of an objective or in the specification of the means to achieve it, irrespective whether the actions directed by this decision‐scheme run according to plan”).43 Slips and lapses are skill‐based errors, while mistakes can be rules‐based errors (bad application of the rules) or knowledge‐based errors (the person has no idea what to do without clear rules, nor how to react to a specific situation).44
29 million departures (USA & EU), 100 time less than bicycle accident risk.
http://www.skybrary.aero/bookshelf/books/3297.pdf. Accessed on July 12, 2016
The understanding of this differentiation allows the determination and implementation of specific actions to avoid future errors of the same kind: intelligent decision support systems (checklists), training, clearer written procedures for maintenance, environmental interface design, self‐knowledge about error types and mechanisms.45 One of the consequences of Reason’s approach to error has been, in some high‐risk industries, to deviate from the usual search for a guilty person to blame. It offers new options on where to act in the quest to prevent errors:46 beyond interventions to enhance the abilities of front‐line workers, actions upstream in the complex interaction of humans, machines and systems.47
James Reason illustrated his reflections on human error in the famous “Swiss‐Cheese Model” (Figure1), a milestone in safety science.
Figure 1. James Reason: The Swiss Cheese model48
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Unawareness and/or unacceptance of errors as being rooted in system processes leads to the “vulnerable system syndrome” making an organisation more error‐prone.49 Organisations suffering from this syndrome share three main characteristics: the impulsion to search for a guilty party to blame in the event of a problem; the non‐
recognition that latent errors are points of vulnerability generated by the system; and a culture of organisation and management focused on productivity without caring for safety.50
In Reason’s model, accidents are explained by a linear succession of actions or a chain of various elements. There is an accident when factor A + factor B + factor C etc. are activated or because factor A causes factor B which causes factor C…, leading to the accident. This linearity is one of the main sources of criticism of the model,51 seen as an over‐
simplification of reality. Despite this criticism, the Swiss Cheese Model remains an essential landmark in safety science and its applications.52