bring to the home health care experience. As a result, they vary with respect to their cognitive, perceptual, and physical capabilities with which to interact with tasks and equipment/technology. Interactions are represented by the double arrows in the model. Tasks and equipment/technology also have different characteristics. The type and magnitude of cognitive, sensory, and physical demands placed on people by these tasks and equipment/technology vary and are directly related to personal capabilities. The multiple environments in which the person(s), tasks, and equipment/technology reside interact with each other and are represented by overlapping circles in the model. These environments also have different characteristics and place varying enablers and barriers on a person’s successful completion of tasks and use of equipment/technology. It is also important to note that systems are dynamic and the attributes of the people, tasks, equipment/technology, and environments change over time.

A diabetes management example can be used to illustrate the model. In this case, we examine the interactions involved when an older man with diabetes uses a glucometer in his home to track his glucose level with the goal of maintaining his serum blood glucose within recommended limits in order to prevent complications. The man performing the task may have low health literacy, visual problems, and some mild cognitive impairment, and his caregiver may be his wife, who is close to him in age. The person components of the interactions may also include a nurse at a distant clinic who monitors the medical data of the care recipient via telemonitoring1 and a nurse and home health aide who visit weekly to check on the general health status of the care recipient, measure his vital signs, and assist with personal care. In terms of tasks, the man may be required to monitor his glucose according to a prescribed protocol. Both he and his wife may take several medications on varying schedules. The wife may need to help her husband with various activities and operate the telemonitoring equipment. Use of both the glucometer and the telemonitoring equipment requires the ability to read labels and displays, operate controls, calibrate the equipment, and understand and remember operating procedures. The environment also plays an important role. In this case, the couple may live in a small apartment in a rural location with unreliable Internet access. However, they may have neighbors who check on them and children who visit regularly. A basic tenet of human factors is that “optimization” of this system requires understanding the characteristics of and interactions among all of the components of the system. As illustrated in this example, even relatively modest home health care systems can be complex and may


1Telemonitoring may involve a personal computer with Internet or e-mail connectivity to send data electronically to the clinic.

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