Human factors encompass all those factors that can influence people and their behaviour. In a work context, human factors are the environmental, organisational and job factors, and individual characteristics which influence behaviour at work.

What is Clinical Human Factors?

Dr Ken Catchpole, a Human Factors expert who has done much work in healthcare has provided this brief definition:

“Enhancing clinical performance through an understanding of the effects of teamwork, tasks, equipment, workspace, culture, organisation on human behaviour and abilities, and application of that knowledge in clinical settings.”

Human Factors is a scientific discipline (not a collection of factors about humans, which is why we don’t answer the question “What are human factors”.

The Institute of Ergonomics and Human Factors (UK) definition for human factors is:

“Ergonomics (or Human Factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimise human well-being and overall system performance.”

Human Factors Theory

How errors and incidents occur

Healthcare professionals are human beings, and like all human beings are fallible. In our personal and working lives we all make mistakes in the things we do, or forget to do, but the impact of these is often non-existent, minor or merely creates inconvenience. However, in healthcare there is always the underlying chance that the consequences could be catastrophic. It is this awareness that often prevents such incidents as we purposefully heighten our attention and vigilance when we encounter situations or tasks we perceive to be risky.

Swiss Cheese Model of organisational accidents (Reason 1990)

One human factors model that is increasingly well known in healthcare is the Swiss Cheese Model of organisational accidents (Reason 1990). The Swiss Cheese Model hypothesises that in any system there are many levels of defence. Examples of levels of defence would be checking of drugs before administration, a preoperative checklist or marking a surgical site before an operation.

Each of these levels of defence has little ‘holes’ in it which are caused by poor design, senior management decision-making, procedures, lack of training, limited resources etc. These holes are known as ‘latent conditions’. If latent conditions become aligned over successive levels of defence they create a window of opportunity for a patient safety incident to occur. Latent conditions also increase the likelihood that healthcare professionals will make ‘active errors.’ That is to say, errors that occur whilst delivering patient care. When a combination of latent conditions and active errors causes all levels of defences to be breached a patient safety incident occurs. This is depicted by the arrow breaching all levels of defence in the image below.

levels of defence


When a combination of latent conditions and active errors causes all levels of defences to be breached a patient safety incident occurs.

When such incidents occur it is uncommon for any single action or ‘failure’ to be wholly responsible. It is far more likely that a series of seemingly minor events all happen consecutively and/or concurrently so on that one day, at that one time, all the ‘holes’ line up and a serious event results.

On investigation it becomes clear that multiple failings occurred and the outcome appears inevitable, but for those working in the system it can be shocking as they have often worked with these same environmental conditions and small errors or slips occurring regularly without harm ever occurring as a result.

It is very rare for staff in healthcare to go to work with the intention of causing harm or failing to do the right thing. Therefore we have to ask why there are many incidents where some of the latent conditions are caused by staff not doing the right thing, even when they know what the right thing is. Many processes and policies in healthcare are complex or seem to create difficulties for busy staff thus creating the temptation to take shortcuts or ‘workarounds’.