Continuous Quality Improvement and Risk Management



Continuous Quality Improvement and Risk Management

Swiss Cheese Theory

The Swiss Cheese Theory was proposed by James T. Reason. He is part of the faculty for Psychology at Manchester University. For a good whole 25 years of his life he had been researching on what causes errors in organizational as well as human systems, despite the existence of multiple layers of defense. In 1990, he came up with the Swiss Cheese model, which attempted to explain the reason and the manner in which an error occurs.

The Swiss Cheese Model was an attempt to explain the manner and sequence of accidents in organizational and other systems. This model works on the basis of the assumption that defense mechanisms exist in models. For instance, drugs get screened and tested before they are administered for legal use. The defense mechanisms and levels develop holes in themselves due to a various reasons such as faulty design, ineffective decision making by senior management, incorrect methods, insufficient training, resource scarcity, etc. The holes can also be termed as latent conditions. In an ideal system, there would be no holes. However, that is far from reality. Holes exist within layers. The occurence of a system error happens when the holes in all the layers (which are stacked together) align to allow the smooth passage of the hazard.

In a system where latent conditions exist, the chances of active errors being made are higher. This further aggravates the flaw in the system as it eases the breach of levels for the hazard. In a stack of cheese (representing an ideal system) the presence of multiple layers denoteds the fact that if an error has passed through a hole in one layer, it won't be able to pass through the next layer if it does not ...