In the contemporary patient safety movement, the systems approach to human errors replaces the traditional, person approach. The basic premise of the systems approach to human errors is acknowledgement that humans are fallible by nature and errors should be expected. Instead of blaming individual healthcare professionals, this approach is focused on identifying true causes of errors and building defenses within the systems in which humans work in order to anticipate and prevent errors or limit their impact when they occur. According to British psychologist James Reason, active failures and latent failures represent the two main categories of errors in a complex system. Active failures, often referred to as errors at the “sharp end” of the system, involve errors made by the frontline healthcare providers. For example, a technologist completed the wrong exam or performed procedure on a wrong patient, a nurse selected and administered the wrong medication, a surgeon performed wrong side surgery, etc. Errors at the “sharp end” of the system are generally quite apparent because they are committed by the healthcare providers who are closest to the patient. The “sharp end” of the system is the point where health care services are provided to the patient, and it also represents the point of contact between the individual and a larger system (human-system interface). Latent failures, or errors at the “blunt end” of the system tend to be less apparent, and they are attributed to broader organizational influences including but not limited to financial constraints, quality management system, organizational culture, allocation of resources, communication, work processes, administrative policies, regulations, etc. The term “root cause” is often used to describe latent failures and the organization’s underlying system for planning, executing, monitoring and controlling work processes.
To understand root causes of adverse events occurring at the “sharp end”, it is necessary to investigate and analyze a wide variety of contributing factors at the “blunt end” of the system. Latent failures can be present in a system for a number of years without causing an accident or any harm to patients. It only takes certain situational factors, also known as unlucky circumstances or contributing factors, to activate the latent failures that will ultimately result in committing an active failure. For example, having two patients with the same name and age in the waiting room at the same time (situational factor) can activate the latent failure (flawed patient identification process) and result in performing the procedure on a wrong patient (active failure). The safety barriers or defenses include a wide variety of technical or administrative safeguards that can prevent the health care provider from committing an active failure in the first place or absorb the effects of the active failure before causing harm to the patient. The safety barriers may include forcing functions, affordances, reminders, equipment lockouts, warning, sensors, alarms, redundancies, policies, procedures, and many others. The Accident Trajectory Model makes it obvious that accidents, adverse events or near misses are caused by complex interactions among a wide variety of factors and system elements, not simply by the individual healthcare providers.