Portal de Periódicos da CAPES

Human Factors and Systems Engineering Approach to Patient Safety for Radiotherapy

2008; Elsevier BV; Volume: 71; Issue: 1 Linguagem: Inglês

10.1016/j.ijrobp.2007.06.088

1879-355X

A. Joy Rivera, Ben‐Tzion Karsh,

Musculoskeletal pain and rehabilitation

The traditional approach to solving patient safety problems in healthcare is to blame the last person to touch the patient. But since the publication of To Err is Human, the call has been instead to use human factors and systems engineering methods and principles to solve patient safety problems. However, an understanding of the human factors and systems engineering is lacking, and confusion remains about what it means to apply their principles. This paper provides a primer on them and their applications to patient safety. The traditional approach to solving patient safety problems in healthcare is to blame the last person to touch the patient. But since the publication of To Err is Human, the call has been instead to use human factors and systems engineering methods and principles to solve patient safety problems. However, an understanding of the human factors and systems engineering is lacking, and confusion remains about what it means to apply their principles. This paper provides a primer on them and their applications to patient safety. IntroductionSince the publication of To Err is Human: Building a Safer Health System (1Institute of Medicine To err is human: Building a safer health system. National Academy Press, Washington DC2000Google Scholar), there has been a call to use human factors and systems engineering methods and principles to solve patient safety problems. However, an understanding of human factors and systems engineering is lacking, and confusion remains about what it means to apply their principles. Therefore, this paper provides a primer on human factors and systems engineering and their application to patient safety. The information summarized in this paper was based on three recent publications by one of the authors that go into more extensive detail about systems engineering for patient safety (2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar, 3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google Scholar) and how to analyze healthcare systems (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar).Before discussing systems engineering, it is first necessary to develop an understating of systems. A system is a set of components that interact to accomplish a common goal. In a healthcare context, the ultimate goal is to provide safe, high-quality patient care. However, a healthcare delivery system has many other goals that need to be simultaneously addressed. Some of those other goals include supporting employee performance, addressing business needs such as profitability and positive image, and meeting external environment needs such as compliance with the Joint Commission (5Karsh B. Hamilton-Escoto K. Beasley J.W. et al.Toward and theoretical approach to medical error reporting system research and design.Appl Ergon. 2006; 37: 283-295Crossref PubMed Scopus (68) Google Scholar). If a healthcare delivery system is not been designed to address all of these goals, then the long-term likelihood of delivering safe, high-quality care diminishes.The basic components of a system are inputs, transformations, outputs, boundaries, environment, and feed processes. System inputs energize the system (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). Examples of inputs in a healthcare system include, but are not limited to, patients, medical staff, equipment required to care for patients, knowledge of the staff, the rules or procedures that must be followed, and lighting in the room. A system transformation is any process that converts the system inputs into outputs (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). Transformations within a healthcare system include communication among staff, communicating with the patient or the patient's family, giving the patient medicine, turning off the lights in the patient's room, and so forth. System outputs are the final products of the transformations (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). Examples of outputs that correspond to the examples of transformations we have listed include a more informed care provider, a more at-ease patient or family, a medicated patient, and a dark patient room.System boundaries define where one system ends and another one begins (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). Systems can be bounded by temporal boundaries (e.g., first shift, second shift), hierarchical boundaries (e.g., a hospital unit within a hospital), spatial boundaries (e.g., a patient's room, the cafeteria), and process boundaries (e.g., scrubbing in for surgery, performing surgery) (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). Anything external to the system's boundaries is the system's environment. If a system is bounded within the radiology unit, the hallway, all other units, and the hospital are a part of that system's environment.The last basic elements of a system are its feed processes. There are three types of feed processes: feedback, feedforward, and feedwithin. Feedback, the most common type, refers to any information that is sent back into the system to help guide it and to allow it to adapt. Examples of feedback in a healthcare system include information from patient monitors or treatment records, communication among staff (the answers are the feedback), and tactile sensations received from using a tool (the nurse feels the feedback when inserting an intravenous line). Feedforward occurs when a system obtains information from its inputs. Patient census trends, when used to predict demands and then adjust unit staffing levels accordingly, is an example of feedforward. Depending on how a system is bounded, feedwithin is either feedback or feedfoward processes within a system. For example, if a system is bounded temporally by the first shift, a patient care note left by a nurse working the first shift for a nurse on the next shift would be considered a feedfoward process for the second shift nurse. However, if the system boundaries have expanded to include all three shifts, that feedforward process becomes a feedwithin process.Systems and Human Factors EngineeringSystems engineering refers to the design of the overall system. The focus is on effectively designing and integrating the components of a system proactively, instead of building the components separately and trying to fit them together later. When people are involved in systems, the process is often referred to as sociotechnical systems engineering. Sociotechnical systems engineering is a systems engineering method focused on designing the social aspects of the system (which consists of the people in the system, such as the healthcare professionals and patients, and all that is human about their presence, such as their knowledge and skills) and the technical aspect (i.e., tools, techniques, technology, procedures) to work together effectively. The basic science of sociotechnical systems engineering is known as human factors engineering.Human factors engineering “discovers and applies information about human behavior, abilities, limitations, and other characteristics to the design of tools, machines, systems, tasks, jobs, and environments for productive, safe, comfortable, and effective human use” (6Chapanis A. Some reflections on progress. Presented at the Human Factors Society 29th Annual Meeting, 1985, Santa Monica, CA.Google Scholar). Simply put, human factors engineers design systems to better fit the people in the system. “Fit” is achieved when the system components are designed such that the people in the system can perform with a low probability of error, injury, illness, or stress and a high probability of productivity, quality, safety, and job satisfaction.Healthcare has traditionally concentrated on improving safety by focusing on the healthcare providers (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar) instead of on the system. With this line of thinking emerged the concept that retraining the care provider, rather than redesigning the system, could improve patient safety (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). With the Institute of Medicine's reports (1Institute of Medicine To err is human: Building a safer health system. National Academy Press, Washington DC2000Google Scholar, 7Institute of Medicine Crossing the quality chasm: A new health system for the 21st century. National Academy Press, Washington DC2001Google Scholar) calling for fundamental changes to redesigning America's health system, healthcare is slowly seeing the need to implement systems and human factors engineering tools and methods into its processes (1Institute of Medicine To err is human: Building a safer health system. National Academy Press, Washington DC2000Google Scholar, 7Institute of Medicine Crossing the quality chasm: A new health system for the 21st century. National Academy Press, Washington DC2001Google Scholar).Systems and human factors engineering principles are now, albeit slowly, being used to improve patient safety (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). The subsequent sections present introductions to three tools for better understanding how systems and human factors engineering can be used to improve patient safety.Work System AnalysisA good first way to apply systems engineering principles for healthcare safety is to learn to analyze a system. Analyzing a system is an important first step in planning changes, implementing technology, or conducting safety analyses (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar).The outcome of a systems analysis is typically a graphic map depicting the inputs, transformations, and outputs of the system under study. These are drawn as flowcharts showing how the various processes and steps within processes in the system interact. A work system analysis can help identify problems in current processes, it can be used as a proactive approach to designing new systems with fewer hazards, and it can be used in research to help understand why problems exist within the patient care process. For more information on how to conduct work system analyses, see the publications by Karsh and Alper (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar), Pasmore (8Pasmore W. Designing effective organizations: The sociotechnical systems perspective. John Wiley and Sons, New York1988Google Scholar), and Hendrick and Kleiner (9Hendrick H. Kleiner B. Macroergonomics: An introduction to work system design. Human Factors and Ergonomics Society, Santa Monica, CA2001Google Scholar, 10Hendrick H. Kleiner B.M. Macroergonomics: Theory, methods, and applications. 1st ed. Lawrence Erlbaum Associates, Mahwah2002Google Scholar).Systems Engineering Initiative for Patient Safety ModelAnother tool for understanding systems engineering concepts is the Systems Engineering Initiative for Patient Safety (SEIPS) model of work system and patient safety (2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar) (Fig. 1). This systems engineering conceptual framework is targeted at those interested in applying systems engineering ideas for patient safety goals. The SEIPS model uses the work system model developed by Smith and Sainfort (11Smith M.J. Sainfort P.C. Balance theory of job design for stress reduction.Int J Ind Ergon. 1989; 4: 67-79Crossref Scopus (319) Google Scholar) to categorize interactions between the person and the system and then identifies where these interactions can be improved (2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar). As shown on the left side of Fig. 1, the work system model categorizes a system into five main components: person, tools and technologies, organization, physical environment, and tasks (2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar). These components are interrelated and influence one another; changes to one component affect the other components (2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar). Table 1 provides a simple list of the components and their possible attributes; each consists of tangible and intangible attributes.Table 1Work system componentsPersonCare provider, other hospital staff, the patient 3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google Scholar, the patient's family, a person's education, skills and motivation 2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google ScholarTools and technologiesSurgical instruments, hospital beds, computer provider order entry system, usability, integration capabilities, and maintenance requirements 2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar, 3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google ScholarOrganizationPolicies, regulations, work schedules, culture, hierarchy of supervision, and teamwork 2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar, 3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google ScholarPhysical environmentLayout of facility, lighting, noise 2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar, 3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google Scholar, and temperature 3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google ScholarTasksOrdering medications, administering medications, lifting patient, performing surgery, difficulty of task 2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar, and time pressures 2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar Open table in a new tab The interaction of these five components produces processes (i.e., system transformations) and these processes lead to outcomes (i.e., system outputs) (2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar). To show these other elements of a system, the SEIPS model integrates the work system model and Donabedian's structure-process-outcome framework (12Donabedian A. The quality of care: How can it be assessed?.JAMA. 1988; 260: 1743-1748Crossref PubMed Scopus (4388) Google Scholar).The SEIPS model provides a view of the entire system (2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar). This helps clinicians, safety engineers, and patient safety researchers take a systems approach to uncovering the causes of errors and safely designing healthcare systems (2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar).Human Factors Paradigm for Patient SafetyAnother conceptual framework for understanding human factors and systems engineering applications to patient safety was presented by Karsh et al. (3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google Scholar) (Fig. 2). This framework was developed from the SEIPS model but focused on demonstrating how the structure of the healthcare system (Fig. 2, left) can influence healthcare provider performance (Fig. 2, middle) and subsequently outcomes such as patient and provider safety (Fig. 2, right). This model can be used as a checklist to consider the various types of provider performance when designing or redesigning systems. The central message of the model is that much of the road to patient safety runs through the healthcare professional; thus, it is imperative that systems be designed that support the physical, cognitive, and social needs of the healthcare professional.Fig. 2Input-transformation-output model of healthcare professional performance (3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google Scholar). This model provides a hierarchy of inputs that affect human performance, which produce system transformations that generate system performance outputs. Reprinted, with permission, from Karsh et al. (3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google Scholar).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Physical performance is any action that involves the musculoskeletal system. This includes walking, lifting patients, checking and recording vital signs, and so forth. Cognitive performance occurs when the human brain generates a transformation. Examples include thinking, perceiving, and remembering. Social/behavioral performance also refers to transformations produced by the brain; however, these transformations have traditionally only been addressed by the social science community. Attributing causality, emotional self-regulation, social learning, and motivation are examples of social/behavioral performance. Depending on the type of human performance generating the transformations, different system outputs will emerge (Fig. 2) (3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google Scholar).Feedback is an essential component of the model. Information from the system's outputs is fed back to the system's inputs, and the system regulates accordingly (3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google Scholar). For example, if an output was produced that did not meet expectations (i.e., a patient was given a medication too late), the reaction of the organization to this event serves as feedback to others, in effect changing their behavior to be consistent with the organization's reactions. For example, if nobody reacts to the lateness, the feedback is that late administration is tolerated. If the reaction is punishment, nurses might react by either giving medications on time or concealing late administrations. If the reaction is one of studying methods to make the system facilitate on-time administration, the nurses will be more likely to participate in developing solutions.ConclusionThe quality of patient care and the efficiency of the healthcare system must be improved. Healthcare's past remedy to the lack of patient safety, blaming individuals, has not solved the problem. Thus, alternative approaches are needed. One approach that has worked in other industries is to use the principles and methods of systems and human factors engineering. The three systems approaches explained in this paper can aid in designing safer and more efficient systems. IntroductionSince the publication of To Err is Human: Building a Safer Health System (1Institute of Medicine To err is human: Building a safer health system. National Academy Press, Washington DC2000Google Scholar), there has been a call to use human factors and systems engineering methods and principles to solve patient safety problems. However, an understanding of human factors and systems engineering is lacking, and confusion remains about what it means to apply their principles. Therefore, this paper provides a primer on human factors and systems engineering and their application to patient safety. The information summarized in this paper was based on three recent publications by one of the authors that go into more extensive detail about systems engineering for patient safety (2Carayon P. Hundt A.S. Karsh B. et al.Work system design for patient safety: The SEIPS model.Qual Safety Healthcare. 2006; 15: i50-i58Crossref PubMed Scopus (911) Google Scholar, 3Karsh B. Alper S.J. Holden R.J. et al.A human factors engineering paradigm for patient safety—designing to support the performance of the health care professional.Qual Safety Healthcare. 2006; 15: i59-i65Crossref PubMed Scopus (254) Google Scholar) and how to analyze healthcare systems (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar).Before discussing systems engineering, it is first necessary to develop an understating of systems. A system is a set of components that interact to accomplish a common goal. In a healthcare context, the ultimate goal is to provide safe, high-quality patient care. However, a healthcare delivery system has many other goals that need to be simultaneously addressed. Some of those other goals include supporting employee performance, addressing business needs such as profitability and positive image, and meeting external environment needs such as compliance with the Joint Commission (5Karsh B. Hamilton-Escoto K. Beasley J.W. et al.Toward and theoretical approach to medical error reporting system research and design.Appl Ergon. 2006; 37: 283-295Crossref PubMed Scopus (68) Google Scholar). If a healthcare delivery system is not been designed to address all of these goals, then the long-term likelihood of delivering safe, high-quality care diminishes.The basic components of a system are inputs, transformations, outputs, boundaries, environment, and feed processes. System inputs energize the system (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). Examples of inputs in a healthcare system include, but are not limited to, patients, medical staff, equipment required to care for patients, knowledge of the staff, the rules or procedures that must be followed, and lighting in the room. A system transformation is any process that converts the system inputs into outputs (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). Transformations within a healthcare system include communication among staff, communicating with the patient or the patient's family, giving the patient medicine, turning off the lights in the patient's room, and so forth. System outputs are the final products of the transformations (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). Examples of outputs that correspond to the examples of transformations we have listed include a more informed care provider, a more at-ease patient or family, a medicated patient, and a dark patient room.System boundaries define where one system ends and another one begins (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). Systems can be bounded by temporal boundaries (e.g., first shift, second shift), hierarchical boundaries (e.g., a hospital unit within a hospital), spatial boundaries (e.g., a patient's room, the cafeteria), and process boundaries (e.g., scrubbing in for surgery, performing surgery) (4Karsh B, Alper SJ. Work system analysis: The key to understanding health care systems. In: Agency for Healthcare Research and Quality, editor. Advances in patient safety: From research to implementation. Rockville, MD: Agency for Healthcare Research and Quality; 2005. Vol. 2, p. 337–348.Google Scholar). Anything external to the system's boundaries is the system's environment. If a system is bounded within the radiology unit, the hallway, all other units, and the hospital are a part of that system's environment.The last basic elements of a system are its feed processes. There are three types of feed processes: feedback, feedforward, and feedwithin. Feedback, the most common type, refers to any information that is sent back into the system to help guide it and to allow it to adapt. Examples of feedback in a healthcare system include information from patient monitors or treatment records, communication among staff (the answers are the feedback), and tactile sensations received from using a tool (the nurse feels the feedback when inserting an intravenous line). Feedforward occurs when a system obtains information from its inputs. Patient census trends, when used to predict demands and then adjust unit staffing levels accordingly, is an example of feedforward. Depending on how a system is bounded, feedwithin is either feedback or feedfoward processes within a system. For example, if a system is bounded temporally by the first shift, a patient care note left by a nurse working the first shift for a nurse on the next shift would be considered a feedfoward process for the second shift nurse. However, if the system boundaries have expanded to include all three shifts, that feedforward process becomes a feedwithin process.