In the Swiss Cheese Model, each slice represents a safeguard, while the holes represent inherent weaknesses. Normally, a second or third slice would stop an error from fully penetrating, resulting in a near miss. If the holes line up, however, a medication incident may occur.
The Swiss cheese model of accident causation is a model used in risk analysis and risk management, including aviation safety, engineering, healthcare, emergency service organizations, and as the principle behind layered security, as used in computer security and defense in depth.
According to this metaphor, in a complex system, hazards are prevented from causing human losses by a series of barriers. Each barrier has unintended weaknesses, or holes – hence the similarity with Swiss cheese. These weaknesses are inconstant – i.e., the holes open and close at random.
A well-known model used to do this is the “Swiss Cheese” model. Renowned psychologist James Reason developed this accident causation model to demonstrate how most accidents can be traced to four levels of failure: Organizational Factors; Unsafe supervision; Preconditions; and Unsafe acts.
An example of a slice of Swiss cheese as a barrier would be safe driving practices. A hole in the cheese could be distracted driving such as texting on a cell phone.
Swiss Cheese Model in pharmacovigilance?
In the Swiss Cheese Model, each slice represents a safeguard, while the holes represent inherent weaknesses. Normally, a second or third slice would stop an error from fully penetrating, resulting in a near miss. If the holes line up, however, a medication incident may occur.
The Swiss Cheese model puts the ownership of workplace injury and accidents on everyone involved. It stresses the need to adjust the planning process, streamline communications and put safety first in all decision making. Fundamental changes to project planning are needed to truly integrate safety into the job.
Reason’s Swiss Cheese model is based on Heinrich’s Domino theory. Barriers are depicted as slices of the Swiss Cheese while the hole in the Cheese represents latent failure (Figure A1). Active failure is directly linked with accidents and failing to stop can cause adverse events.
Weakness of Swiss Model
Each barrier has unintended weaknesses, or holes – hence the similarity with Swiss cheese. These weaknesses are inconstant – i.e., the holes open and close at random. When by chance all holes are aligned, the hazard reaches the patient and causes harm.
The idea is to slice the cheese and specify what each slice is used for. As each hole varies in size and position in each slice, it is like a “flaw”. Failure occurs when the holes in the slices align, allowing a hazard to pass through all of the layers of defense and causing serious accidents.
Think of defending yourself from COVID-19 as slices of Swiss cheese. Wearing a mask or washing your hands is not enough because each slice by itself has holes. If you layer the slices by taking more safety steps, you’ll protect yourself and others better. Wear a mask.
the role of the Swiss Cheese Model in quality of healthcare?
So pieces of Swiss cheese, or each slice, represents a barrier, a pharmacist, a physician, a nurse, a information technology, automated decision support. So each of them create a potential barrier for a propagating problem to intercept that problem.
Reason developed the “Swiss cheese model” to illustrate how analyses of major accidents and catastrophic systems failures tend to reveal multiple, smaller failures leading up to the actual hazard.
In the model, each slice of cheese represents a safety barrier or precaution relevant to a particular hazard. For example, if the hazard were wrong-site surgery, slices of the cheese might include conventions for identifying sidedness on radiology tests, a protocol for signing the correct site when the surgeon and patient first meet, and a second protocol for reviewing the medical record and checking the previously marked site in the operating room. Many more layers exist. The point is that no single barrier is foolproof. They each have “holes”; hence, the Swiss cheese. For some serious events (e.g., operating on the wrong site or wrong person), even though the holes will align infrequently, even rare cases of harm (errors making it “through the cheese”) will be unacceptable.
While the model may convey the impression that the slices of cheese and the location of their respective holes are independent, this may not be the case. For instance, in an emergency situation, all three of the surgical identification safety checks mentioned above may fail or be bypassed. The surgeon may meet the patient for the first time in the operating room. A hurried x-ray technologist might mislabel a film (or simply hang it backwards and a hurried surgeon not notice), “signing the site” may not take place at all (e.g., if the patient is unconscious) or, if it takes place, be rushed and offer no real protection. In the technical parlance of accident analysis, the different barriers may have a common failure mode, in which several protections are lost at once (i.e., several layers of the cheese line up).
In health care, such failure modes, in which slices of the cheese line up more often than one would expect if the location of their holes were independent of each other (and certainly more often than wings fly off airplanes) occur distressingly commonly. In fact, many of the systems problems discussed by Reason and others—poorly designed work schedules, lack of teamwork, variations in the design of important equipment between and even within institutions—are sufficiently common that many of the slices of cheese already have their holes aligned. In such cases, one slice of cheese may be all that is left between the patient and significant hazard.
