How do errors result in harm?
This is illustrated most frequently by James Reason’s “Swiss cheese model.” The slices of Swiss cheese represent safety barriers or "defensive layers". Before an error results in harm, a number of safety barriers usually have to be penetrated.
An example: If a doctor prescribes the wrong medicine, the prescription first goes to the pharmacy, then on to the nurse and the patient. This can only result in harm if the doctor’s mistake (prescribing the wrong medicine) penetrates these safety barriers unnoticed.
Reason's Swiss Cheese Model
