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Aetiology of hospital setting adverse events 1: limitations of the 'Swiss cheese' model.

Introduction An adverse event in health care is an injury resulting from a patient’s medical management rather than a consequence of the patient’s underlying medical condition or conditions. Adverse events are common and costly to the affected patients and the health-care system. In the last two decades, the incidence, aetiology and outcomes from adverse events have been documented mostly in the hospital setting (Table 1). Taking these studies together, approximately 10% of hospital patient admissions have some sort of adverse event. Of these, half result in no long-term harm to the patient. However, 10% (of the 10%, i.e. 1% of all hospital admissions) of the affected patients suffer significant harm; they either die or are left with some sort of permanent disability as a result of the adverse event (Table 1) (Buist et al, 2003). In 1995 the cost of adverse events to the Australian health-care system was estimated at $2 billion (AUD) dollars (Wilson et al, 1995). Attempts to reduce the incidence of adverse events and make hospitals safer have been largely unsuccessful (Shojania and Thomas, 2013). Like other diseases and conditions, an understanding of the underlying aetiology or pathophysiology of adverse events is important for the development of preventative strategies. To date the predominant theory to explain adverse events in health has been the ‘Swiss cheese’ model developed by James Reason (1997) from his analysis of large scale industrial and organizational accidents. This article examines that theory and its limitations when applied to hospital systems, with specific reference to the deteriorating patient – the final common pathway for most adverse events when patients suffer harm. A second article (p. C175) proposes an alternative model called clinical futile cycles to explain hospital setting adverse events which takes into account some of the unique cultural systems that exist in hospitals (Buist and DeVita, 2010).