Swiss cheese model
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- For the Swiss Cheese model in physical cosmology, see large-scale structure of the cosmos, galaxy filament, and supercluster.
The Swiss Cheese model of accident causation is a model used in the risk analysis and risk management of human systems, commonly aviation, engineering, and healthcare. It likens human systems to multiple slices of swiss cheese, stacked together, side by side. It was originally propounded by Dante Orlandella and James T. Reason of the University of Manchester (Reason 1990), and has since gained widespread acceptance and use in healthcare, in the aviation safety industry, and in emergency service organizations. It is sometimes called the cumulative act effect.
Reason hypothesizes that most accidents can be traced to one or more of four levels of failure: Organizational influences, unsafe supervision, preconditions for unsafe acts, and the unsafe acts themselves. In the Swiss Cheese model, an organization's defenses against failure are modeled as a series of barriers, represented as slices of Swiss cheese. The holes in the cheese slices represent individual weaknesses in individual parts of the system, and are continually varying in size and position in all slices. The system as a whole produces failures when all of the holes in each of the slices momentarily align, permitting (in Reason's words) "a trajectory of accident opportunity", so that a hazard passes through all of the holes in all of the defenses, leading to a failure.
The Swiss Cheese model includes, in the causal sequence of human failures that leads to an accident or an error, both active failures and latent failures. The former concept of active failures encompasses the unsafe acts that can be directly linked to an accident, such as (in the case of aircraft accidents) pilot errors. The latter concept of latent failures is particularly useful in the process of aircraft accident investigation, since it encourages the study of contributory factors in the system that may have lain dormant for a long time (days, weeks, or months) until they finally contributed to the accident. Latent failures span the first three levels of failure in Reason's model. Preconditions for unsafe acts include fatigued air crew or improper communications practices. Unsafe supervision encompasses such things as, for example, two inexperienced pilots being paired together and sent on a flight into known adverse weather at night. Organizational influences encompass such things as reduction in expenditure on pilot training in times of financial austerity.
The same analyses and models apply in the field of healthcare, and many researchers have provided descriptive summaries, anecdotes, and analyses of Reason's work in the field. For example, a latent failure could be the similar packaging of two different prescription drugs that are then stored close to each other in a pharmacy. Such a failure would be a contributory factor in the administration of the wrong drug to a patient. Such research has led to the realization that medical error can be the result of "system flaws, not character flaws", and that individual greed, ignorance, malice, or laziness are not the only causes of error.
Lubnau, Lubnau, and Okray apply Reason's Swiss Cheese model to the engineering of human systems in the field of firefighting, with the aim of reducing human errors by "inserting additional layers of cheese into the system", namely the techniques of Crew Resource Management.
Although the Swiss cheese model is respected and considered to be a useful method of relating concepts, it has been subject to some criticism, including that it is used over broadly, and without enough other models or support. However, it is viewed as a decent model when supported.
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- Douglas A. Wiegmann and Scott A. Shappell (2003). A Human Error Approach to Aviation Accident Analysis: The Human Factors Analysis and Classification System. Ashgate Publishing, Ltd. pp. 48–49. ISBN 0754618730.
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- Thomas Lubnau II, Randy Okray, and Thomas Lubnau (2004). Crew Resource Management for the Fire Service. PennWell Books. pp. 20–21. ISBN 1593700067.
- "Revisiting the Swiss cheese model of accidents". Eurocontrol. October 2006.
 Further reading
- Reason, James (2000-03-18). "Human error: models and management". British Medical Journal 320 (7237): 768–770. doi:10.1136/bmj.320.7237.768. PMC 1117770. PMID 10720363.
- Reason, James (1990-04-12). "The Contribution of Latent Human Failures to the Breakdown of Complex Systems". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 327 (1241): 475–484. doi:10.1098/rstb.1990.0090.
- Reason, James (1997). Managing the risks of organizational accidents. Aldershot: Ashgate. ISBN 1840141042.
- Reason, James (1995). "A System Approach to Organizational Error". Ergonomics 38: 1708–1721.
- Bayley, Carol (2004). "What medical errors can tell us about management mistakes". In Paul B. Hofmann and Frankie Perry. Management Mistakes in Healthcare: Identification, Correction, and Prevention. Cambridge University Press. pp. 74–75. ISBN 0521829003.
- Garland, Daniel J. (1998). Organizational factors associated with safety and mission success in aviation environments. Lawrence Erlbaum Associates. p. 84. ISBN 0805816801. More than one of
|last=specified (help) — Westrum and Adamski relate Reason's Swiss Cheese model to Westrum's "human envelope" model, where "around every complex operation there is a human envelope that develops, operates, maintains, interfaces, and evaluates the function of the sociotechnological system" and where the system "depends on the integrity of this envelope, on its thickness and strength". Westrum models latent failures as voids within this envelope, and active failures as factors external to the envelope that are acting to breach it.
- Shappell, Scott A.; Wiegmann, Douglas A. (February 2000). "The Human Factors Analysis and Classification System—HFACS: The "Swiss cheese" model of accident causation". National Technical Information Service.
- "Sources of Error in Drug Interactions: The Swiss Cheese Model". Pharmacy Times. 2004.
- Perneger, Thomas V. (2005-11-09). "The Swiss cheese model of safety incidents: are there holes in the metaphor?". BMC Health Services Research (BioMed Central Ltd.) 5 (71). doi:10.1186/1472-6963-5-71.
- Young, M.S.; Shorrock, S.T.; Faulkner, J.P.E (2005-06-14). "Seeking and finding organisational accident causes: Comments on the Swiss cheese model". Department of Aviation, University of New South Wales. (also available on-line here) — a reminder that while Reason's model extends causation to latent failures, this is not at the expense of eliminating active failure entirely
- Nance, John J. (2005-04-12). "Just How Secure Is Airline Security?: The Swiss Cheese Model and What We've Really Accomplished Since 9/11". ABC News.
- Luxhøj, James T.; Kauffeld, Kimberlee (2003). "Evaluating the Effect of Technology Insertion into the National Airspace System". The Rutgers Scholar 3.
- Howell, Elizabeth A.; Chassin, Mark R. (May 2006). "Right? Left? Neither!". Morbidity & Mortality Rounds on the Web. Agency for Healthcare Research and Quality. — the application of the Swiss Cheese model to a specific case of medical error