Latent errors

It is therefore useful to distinguish between active and latent errors or failures. An active human error has an immediate effect in that it either directly causes a hazardous state of the system or is the direct initiator of a chain of events which rapidly leads to the imdesirable state. 

In the case of a latent human error the consequences of the error may only become apparent after a period of time when the condition caused by the error combines with other errors or particular operational conditions. Two types of latent error can be distinguished. One category originates at the operational level and leads to some required system function being degraded or unavailable. Maintenance and inspection operations are a frequent source of this type of latent failure. 

In an offshore oil production platform, a major accident occurred partly because pump seals failed and therefore an antifoaming agent was not delivered to a crude oil separator. The fact that the pump seals were defective should have been picked up during routine inspections, but the inspections were neglected because of production pressures. The failure to carry out the inspections was a latent error. 

Example 2.3 A Latent Error Due to Lack of Design Knowledge (Kletz, 1994b)... 

Recovery Error/Failure A recovery failure occurs if a potentially recoverable active or latent error is not detected or remedial achon is not taken before the negative consequences of the error occur. 

Latent error An erroneous action or decision for which the consequences only become apparent after a period of time when other conditions or events combine with the original error to produce a negative consequence for the system. 

Policy makers, practitioners, and scholars from a variety of disciplines have recently embraced a new approach to risk reduction in health care—a "systems approach"—without proposing any specific reforms of medical liability law. The Institute of Medicine (IOM) placed its imprimatur on this approach in its recent reports (Kohn et al., 2000 IOM, 2001). In its simplest form, a systems approach to risk reduction in health care posits that an injury to a patient is often the manifestation of a latent error in the system of providing care. In other words, a medical mishap is the proverbial "accident waiting to happen" because the injury-preventing tools currently deployed, including medical liability law, are aimed at finding the individuals at fault rather than the systemic causes of error. Coexistence of a systems approach to error reduction and medical liability law as a conceptual framework for policy makers implies that the latter is likely to evolve in an incremental fashion as the former makes more visible different aspects of the medical error problem. 

Latent component failures, human errors, and related imsafe acts and errors are all results of weaknesses in our management systems. This is why the terms root cause and management system weaknesses are used interchangeably. The term latent failure or latent error is still used in some academic settings. 

Reason (21) has described a model for looking at human error that portrays a battle between the sources of error and the system-based defenses against them. This model is often referred to as the "Swiss cheese model" because the defenses against error are displayed as thin layers with holes that are described as latent error in the system. Figure 26.5 demonstrates the model as applied to medication error. Each opportunity for error is defended by the prescriber, pharmacist, nurse, and patient. When a potential error is identified and corrected (e.g., dose error, route of administration error) the event becomes a "near miss" rather than an ADE. In those cases in which the holes in the Swiss cheese line up, a preventable medication error occurs. The Swiss cheese model provides an interesting framework for research in this field. 

The latent errors in the medication use system have been described in several studies. Major contributors to errors in medication use were found to be knowledge gap related to drug therapy (30%) ... 

To identify opportunities for reducing medication errorS/ it is important that each error be carefully reviewed by a limited number of individuals to gain intimate knowledge of each reported incident. Collection and classification of error data must be followed by use of a careful epidemiological approach to problem solving at the system level. Narrative data which may not be seen by looking at the categorical data alone/ can be used to provide important details about proximal causes and latent error that may have contributed to the event. Success in this type of error reduction requires the reviewers to read between the lineS/ look for common threads between reports/ and link multiple errors that are the result of system weaknesses. 

Figure 5 illustrates the relations between factors influencmg on possibility of latent error commitment which can induce active human errors. Relevant factors should be considered during analysis of protection layers, especially the alarm system and human machine interface (Scarborough et al. 2005). 

At the same time, achange in approach to organizational safety can be identified a more traditional reactive perspective to undesirable events has progressively been replaced by a proactive outlook that contemplates a set of elements in an integrated system. Within this framework, latent errors are presented as a recirrring theme in theoretical accounts of major accidents and, therefore, should be targeted by preventive initiatives. 

Ramanujam, R. (2003). The effects of discontinuous change on latent errors in organizations the moderating role of risk. Academy of Management Journal, 46(5), 608-17. 

James Reason s Human Error, which was previously mentioned, is also a highly recommended resource. First published in 1990, it has since had 12 reprintings. Reason discusses The Nature of error Studies of human error Performance levels and error types Cognitive underspecification and error forms A design for a fallible machine The detection of errors Latent errors and system disasters and Assessing and reducing the human error risk. 

Per references from the nuclear power industry, loss-producing events are said to be split between 80 percent human error and 20 percent physical equipment failure. Of this 80 percent allocated to human error, 70 percent stem from organizational weakness (latent errors). Only 30 percent are from individual mistakes. If 70 percent of incidents are due to organizational... 

HPl asks us to seek out latent errors that may not manifest themselves for long periods of time. For example, one of the authors used the JHA as part of an... 

For example, if supervisors have little control over maintenance, hiring practices, trairung, budget, time, quality, etc., then they have little control over the elements that create the potential for a loss-producing event. In this scenario, if supervisors are held accormtable for injuries that may occur, they are being held accormtable for human and latent errors that are not under his or her control (Volume 1 Concepts and principles, human performance improvement handbook, 2009). The best approach is to have clearly defined, tangible responsibilities for preloss activities and lines of authority. 

Roles and responsibilities will define the types of leadership skills that are necessary to support the safety management system and avoid or reduce the potential for active and latent errors that lead to loss-producing events. The following are examples of some assigned safety roles for each category ... 

Latent errors result in hidden organization-related weaknesses or equipment flaws that lie dormant. Such errors go unnoticed at the time they occur and have no immediate apparent outcome to the facility or to personnel. Latent conditions include actions, directives, and decisions that either create the preconditions for error or fail to prevent, catch, or mitigate the effects of error on the physical facility... Managers, supervisors, and technical staff as well as front-line workers, are capable of creating latent conditions. Inaccuracies become embedded in paper-based directives, such as procedures, policies, drawing, and design bases documentation. 

The systems approach seeks to identify situations or factors likely to contribute to human error. James Reason s analysis of industrial accidents revealed that catastrophic safety failures almost never result from isolated errors conunitted by individuals. Most incidents result from smaller and multiple errors in components and environments with underlying system flaws. Reason s Swiss Cheese Model describes this phenomenon. Errors made by individuals can result in disastrous consequences due to flawed systans that are represented by the holes in the cheese. Reason believed human error would happen in complex systems. Striving for perfection or punishing individuals who make errors does not appreciably improve safety. A systems approach stresses efforts to catch or anticipate human errors before they occur. Reason used the terms active errors and latent errors to distinguish individual errors from system errors. Active errors almost always involve frontline personnel. They occur at the point of contact between a human and some element of a larger system. Latent errors occur due to failures of the organization or designs that allow inevitable active errors to cause harm. The terms sharp end and blunt end correspond to active error and latent error. The systems approach provides a framework for analysis of errors and efforts to improve safety. 

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