National Academies Press: OpenBook

Enabling America: Assessing the Role of Rehabilitation Science and Engineering (1997)

Chapter: 5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING

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Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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5
Functional Limitations Research in Rehabilitation Science and Engineering

Although rehabilitation interventions can effectively target impairments that can be remediated, little is known about the relationship between impairment and functional limitations (Jette, 1995). This chapter reviews knowledge and research in the area of functional limitation in the context of the enabling-disabling model (see Chapter 3). In this conceptual framework, the functional limitations result from impairment, and functional limitation may result in a disability. Reduction of functional limitation from arthritis alone by only 0.5 percent per year over 50 years could reduce disability by 4 million person-years, a savings of nearly $100 billion in 1993 dollars (Boult et al., 1996). Proper measurement of functional limitations is difficult and expensive, and many clinicians are not aware of the extraordinary deficiencies that exist in the functional limitations literature. For example, the functional benefits of strengthening exercises for older people with one or more weakness-producing impairments are essentially unknown, despite the obvious appeal of such a commonsensical notion. Although intervention strategies may be offered by the clinician, valid treatment outcomes have not been reported. Strength may have a nonlinear relationship to functional locomotion, because strength changes beyond some threshold may not engender further gait improvement (Buchner and deLateur, 1991).

At the opposite extreme, however, is the obvious and well-documented relationship between impairment from a lower limb amputation and the functional restoration provided by a leg prosthesis. Just as clearly, however, impairment does not always lead to functional limitation; in-

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

deed, disfiguring dermatological impairments may cause societal disability but engender no functional limitations.

Background

The term impairment, for example, describes abnormalities in specific organs or organ systems (see Chapter 4). Pain* and decrements in strength, range of motion, balance, and endurance are examples of impairments. Functional limitations are restrictions or lack of abilities in performance of the whole organism or individual, assessed in a manner to eliminate external environmental barriers to performance. An individual's gait and other locomotor activities as assessed in a gait laboratory are examples of functional limitations measures. As such, functional limitations reflect an attribute of the capacity of an individual. In this report functional limitation is used as defined and discussed by Nagi (1965) and further developed in Disability in America (Institute of Medicine, 1991).

Disability, in contrast to functional limitation, is a relational concept that describes any restriction or lack of ability to perform an activity in the manner or within the range considered normal for a human being. As a relational concept, disability reflects the individual's capacity to perform a task or activity necessary to achieve a role such as homemaker, worker, parent, or spouse, as well as the environmental conditions in which they are to be performed. These activities can be organized and assessed across different spheres of life. Thus, a subject's report of self-care performance (as reflected in the Sickness Impact Profile, Functional Independence Measure [FIM], Barthel, and other traditional activities of daily living [ADL] measures) is an activity, and measures of such are indicators of disability.

The link between changes in impairment and changes in functional limitation has long been assumed, but it has rarely been documented scientifically. New impairments have been shown to engender locomotor compensatory mechanisms; to date, however, no data are available to link impairments to such compensatory mechanisms in individuals with specific functional limitations or disabilities. Until this link is established, it will be impossible to discern compensatory mechanisms such as Trendelenburg gait resulting from primary disabling and functionally limiting mechanisms such as hip abductor muscle weakness or range of motion limitation.

*  

Most often, pain is considered an impairment, a result of a pathology or impairment, and a cause for functional limitation. Chronic pain, pain that persists for 3 months or longer, has implications across the enabling-disabling process, with most significant impact at the level of disability and quality of life. Thus, pain may be identified at multiple areas of the model and may be modified through a variety of interventions.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

It is therefore not known at present whether rehabilitation interventions should focus on the impairment, the primary functional limitation, or the compensatory functional limitations level. Rehabilitation demands that all levels of disability be addressed. Until more functional limitations research is done, however, it will be impossible to know how much activity limitation is imposed by the environment and how much is imposed by the whole person's functional capacity.

Virtually all rehabilitation texts suggest that strength, restriction of movement, and other impairments be measured during assessments of people with disabling conditions, but the current emphasis of health maintenance organizations and preferred provider organizations on rapidly returning patients to premorbid functional status is beginning to cause this paradigm to shift. Assessments of the level of home care support available and barriers to returning to work are causing disability and functional limitations to be measured first. Once established, the clinician can work to obviate the functional limitation by addressing it directly or, in the traditional way by fixing the impairment. Little research, however, supports either approach, and many more data are needed before such methods can be proven to be scientifically sound.

Cross-Cutting Issues

Two particular issues relative to functional limitations research must be addressed: (1) measurement of functional limitations and (2) time of onset or duration of impairment and functional limitation. Both of these issues affect the research and science in this area. Measurement in functional limitations research is essential, but it is poorly developed and often costly to complete. Measurement must be standardized for the age of the person with a disabling condition. It must also be recognized that people with disabling conditions age with their disabling conditions, and aging and secondary conditions affect the functional limitation and disability of those people.

Measurement

Measuring the effects of interventions has traditionally been at the impairment level. For example, clinicians frequently measure the levels of certain substances in blood, range of motion, and change in range of motion or strength in the laboratory. As well, burden of care or disability measures of performance are often confused as representing functional capacity measures. Typical examples of these measures are the FIM, Barthel, and other traditional measures. More recently, the FIM has been more consistently utilized to determine aggregate outcomes of a program

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

rather than individual measurement. Measuring functional capacity outcomes requires determination of the performance of the whole person. Standardized measures of functional outcomes for use in evaluation or diagnosis are being developed, but they are not routinely used to obtain outcomes measurements for specific interventions. Contextual and environmental factors, however, must be noted and controlled: frequently, there is a difference between capability (the ability to complete a task in an ideal situation) and real-life performance (the ability to complete a task in a typical situation). Such standardized measures would be important for monitoring individuals and for determination of the costs-benefits of rehabilitation programs and interventions to society. Care must be taken in using existing outcomes measures accurately, because measurement at the functional limitation level is expensive and difficult.

Functional limitations measures—obtained, for example, through gait studies and gait analysis—are few and incompletely validated. Although computerized locomotion analysis laboratories have been widely available for many years, few data support the need for gait analysis in clinical decision making, with the possible exception of presurgical decisions for children with cerebral palsy (Krebs, 1995). More studies of locomotor activities of daily living (ADL) are needed to assess functional performance pre- and postintervention and to provide descriptions of the nature of functional limitations. For example, it is known that people with balance disorders may have ataxic gait, but there is no quantitative clinical, bedside, or laboratory measure of ataxia. As a result, treatment for ataxia resulting from cerebellar lesions is entirely empiric. Measurement at the level of functional limitation requires at least whole-body, person-level measurements of performance of ADL. Such measures should include not only the gait on smooth, level surfaces but also sit-to-stand, stair ascent and descent, turning, reaching, and other locomotor ADL.

Basic ADL include locomotor ADL and bowel, bladder, and sexual functions; that is, those ADL that are usually performed without aids or instrumentation. Instrumented ADL (IADL), by contrast, include some device such as a telephone or toothbrush in the performance of a task. Thus, the adaptation (or lack thereof) of the device will affect performance capacity. For example, a child may write or brush her teeth much better with a large-diameter pencil or toothbrush than with regular devices designed for use by adults. Elderly people with impaired vision will perform as well as subjects without impaired vision if the numbers on an instrument are large and have high contrast. Functional limitations research usually attempts to obviate such IADL differences, but in practice, some standardization is required even in basic ADL. For example, stair or chair height contributes substantially to performance variation (Krebs et al., 1992). Burden-of-care measures such as the Functional Independence

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

Measurement usually attempt to estimate the impact of functional limitations on care providers, but they often ignore differences among IADL. As noted, these measures are disability-level measures.

Aging and Secondary Conditions

The age of onset of an impairment and the duration of impairment are recognized as important aspects of functional limitations knowledge and research. Aging must be considered in evaluating the functional status of a person with a disabling condition over time and in evaluating the appropriate interventions. Aging is a conception-to-death series of events that includes attaining, maintaining, and losing skills. Therefore, functional capacity changes with age. Growth and development affect the functional outcomes of interventions for infants and children with disabling conditions. No validated methods of discriminating between development and interventions in children with developmental disabling conditions exist.

The process of aging discriminates against no person. Everyone is a participant in the process of growing older—including people with disabilities. ''Nondisabled Americans are getting older; they're living longer, there are vastly more of them, and they're getting old nonfatally. In short, they're becoming more disabled.... All at once, it seems, there are a lot of formerly nondisabled people around." (Corbet, 1990) In the last two decades increasing attention has been directed toward disability and aging.

In people with disabling conditions, depending on the compensatory strategies used, secondary conditions and comorbidities, can affect functional status throughout a person's life. Secondary conditions are impairments, functional limitations, disabilities, diseases, injuries or other conditions that occur during the life of a person with a disability, where the primary disabling condition is a risk factor for that secondary condition, or may alter the management of health and medical conditions. This of course is based on the new paradigm that people with disabilities are healthy, that is a disabling condition does not imply illness and disease. Each factor in the interaction of disability and aging has the capability to become a "negative feedback loop" (Guralnick, 1994) which may lead to further disability or a new medical condition.

In recent years, a body of literature regarding the effects of aging and secondary conditions has been developing. Spinal cord injury and aging is the best developed, with information available in the areas of quality of life (Evans et al., 1994), functional changes over time (Gerhart et al., 1993; Pentland and Twomey, 1994), premature and interactive effects of disability and aging (Ohry et al., 1983; Lammertse and Yarkony, 1991; Bauman and Spungen, 1994), aging and secondary conditions (Charlifue,

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

1993), and psychological adjustment (Krause and Crewe, 1991), among other issues. Cerebral palsy (Turk et al., 1996), spina bifida (Lollar, 1994), and polio (Maynard et al., 1991), among other disabling conditions, have also been studied.

Identification of age-related changes and secondary conditions and their risk factors has been better developed (Whiteneck et al., 1992; Charlifue, 1993; Turk et al., 1995, 1996; White, Seekins, and Gutierrez, 1996) than prevention or intervention strategies. To illustrate, Table 5-1 provides some examples in various body systems of age-related changes, potential secondary conditions, and prevention strategies for people with mobility limitations such as spinal cord injury. This provides a heuristic and practical guide for examining the interactive effects among disabling conditions, aging, and secondary conditions.

The issue of disability and aging is one more dimension that should be considered with the enabling-disabling model. As a person with a disability ages, a series of new pathologies, impairments, and functional limitations become placed over the previous pathologies, impairments, and functional limitations. Thus, the model is a snapshot in time of an individual's status in the disabling process.

Relationship Between Functional Limitations and Impairments

The committee searched Medline files to determine the quantity of peer-reviewed publications from 1966 to November 1996 addressing functional limitations. Of the 31,612 publications that used the term rehabilitation anywhere in the Medline file, only 34 used the term functional limitations.

There were 4,980 publications that included the term "function," which might better represent "functional limitations" in rehabilitation research. Yet most of these articles focused on cell or organ function rather than whole-person function. Of the 34 publications that used the term "functional limitations," only a few examined changes in functional limitation. Therefore, it can be said that there is a paucity of published reports that truly represents research in functional limitations. This is in contrast to the relatively good support for functional limitations research by federal agencies as noted in Appendix A. This apparent mismatch of publications and funded research is likely related to confusion in terminology, difficulty in tracking systems, and unknowingly mixed impairment-functional limitations identifications, interventions, and measures. Funding agencies are increasingly supporting research intending to measure functional limitations, but few reports have emanated in part because functional limitations research is expensive and difficult to conduct.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

TABLE 5-1 Lifelong Motor Disabilities, Aging, and Secondary Conditions

Body System

Pathology, Impairment, or Other Conditions Leading to Potential Secondary Conditions

Potential Prevention Strategies

Skin and Subcutaneous Tissues

Insensate skin; increased areas of pressure due to poor positioning, obesity, or limited weight shifts because of cognitive, behavioral, or personal care issues; decreased elasticity or turgor in aging with top layer thinning resulting in increased susceptibility to shearing and tearing; urinary or bowel incontinence.

Regular weight shift routine; appropriate seating systems and surfaces; good nutrition and hygiene habits; social or cognitive support to follow through with prevention.

Musculoskeletal System

Decreased strength and endurance; decreased range of motion; pain; osteoporosis (must recognize hereditary and all acquired forms); asymmetric motor performance; overuse or repetitive activities on unprepared system; aging issues of decreased flexibility, strength, endurance, and balance; risk of falls; obesity.

Maintenance of exercise programs (endurance, strength, flexibility); falls avoidance practices; osteoporosis prevention or management—must determine type of osteoporosis and state of clinical/ scientific information; use of proper body mechanics and posture; appropriate assistive devices utilization; environmental accessibility; consideration of ergonomically correct work and activity surroundings; use of energy conservation and joint protection techniques.

Cardiovascular System

Hypertension; atherosclerosis (similar risk factors as in nondisabled individuals); limited activity and exercise; deep venous thrombosis and resulting pulmonary emboli—more often an early complication; obesity; age-related changes of slower responsiveness to position or heart rate change.

Health practices to identify risk factors for atherosclerosis (hypertension, smoking, hypercholesterolemia or hyperlipidemia, diabetes, menopause, etc.) and initiation of prevention or management strategies; good nutrition; maintenance of exercise or activity programs.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

Genitourinary System

Urinary retention or incontinence; change in urinary function from existing underlying condition (expected or unexpected progressive changes); progressive and chronic kidney filtration changes from poor or unchanged bladder management techniques; chronic urinary tract infections; kidney stones; prostate enlargement; urinary continence changes with menstrual cycle; changing urinary function from aging (e.g., reduced bladder capacity, decreased tissue compliance, reduced flow rate).

Monitoring of fluid intake and output; maintaining regular voiding schedule (e.g., intermittent cath program, use of medication, timed voiding program); achieving acceptable hygiene program; participation in regular evaluation of urinary management (e.g., urodynamics, renal scans, postvoid residual checks); reporting of urinary habit changes; consideration of surgical options when appropriate; education in the consequences of urinary management, pros and cons of suggested interventions.

Respiratory System

Compromised breathing or cough due to underlying weakness; aspiration; existing obstructive or restrictive pulmonary disease or progression; breathing changes associated with aging (e.g., loss of reserve capacity, decreased tissue compliance); obesity; progressive weakness due to underlying condition; recurrent pneumonia.

Monitoring pulmonary function as appropriate and reporting changes; cessation of smoking or contact with secondary smoke; use of assistive coughing; maintaining exercise or activity program and health diet; education of management strategies in progressive conditions; use of vaccinations when appropriate.

Gastrointestinal System

Decreased bowel motility with increased transit time; esophageal reflux; peptic ulcer disease; constipation or obstipation; megacolon; abnormal swallow function; hemorrhoids or risk for hemorrhoids with bowel program; malabsorption.

Good nutrition with diet modification (e.g., consistencies, textures, tastes); maintaining and monitoring routine bowel evacuation with consideration of fiber, fluid, and medication; review of routine medications which could contribute to decreased bowel motility; avoiding overuse of bowel medications; monitoring diet history and weights; reporting changes in bowel evacuation.

NOTE: This is not an inclusive table and serves as a practical guide only.

SOURCE: Adapted from S. W. Charlifue (1993)

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

Functional Capacity Index and the 10 Dimensions of Function

As mentioned above, one of the current issues within functional limitations research is measurement and quantification of functional limitation in an individual. One proposed method of classification is embodied in the recently developed Functional Capacity Index (FCI). As a way to map out anatomic descriptions of the nature and extent of functional limitations, the FCI first defines 10 dimensions of function in which scientists can describe physical capacity (MacKenzie et al., 1996). Using the FCI as a guide to describing the different areas of research in functional limitation, this chapter reviews 10 dimensions of function: (1) locomotion, (2) hand and arm manipulation, (3) bending and lifting, (4) eating, (5) elimination, (6) sexual function, (7) visual function, (8) auditory function, (9) speech, and (10) cognitive function. The category of pain is excluded because it does not describe function but rather determines function. Thus, only to the extent that pain affects function in each of the dimensions will it be reflected in this schema. Pain can be considered an impairment, and intervention for pain is often at the organ system level. Cardiopulmonary function is not identified individually, but is felt to be included for performance of most of the functions. It should however be noted that rehabilitation science and engineering has had direct involvement in research and intervention in this area (e.g. cardiac rehabilitation, pulmonary rehabilitation, mechanical ventilation [noninvasive and invasive]). Psychosocial function is also excluded, consistent with the entire committee report.

It should be noted that much of what is reported in this section is a combination of impairment and functional limitations research, and at times consideration or recognition of disability and quality of life measures. This points out the difficulty in identification of this research realm, but as in rehabilitation science and practice, recognizes the often blurred and necessary distinctions.

Locomotion Functional Limitations

Strength Impairment Relationships to Locomotor Functional Limitations

Scant data exist on strength training among people with impairments, still fewer studies include people with functional limitations, and to date no reports relate strength changes to disability measures and locomotor activities among people with disabling conditions. "Although high-intensity training increases force-generating capacity, little is known about its effects on functional performance. Unless investigations are conducted in which different measures of functional performance are made prior to

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

and following resistance training, the validity of this approach to improving the quality of life of older persons cannot be established" (Hopp, 1993, p. 371).

Studying only outcomes and not the mechanisms by which strength contributes to function has produced limited and contradictory results. For example, Fiatarone et al. (1990) found that frail institutionalized subjects with a mean age of 90 ± 1 years experienced highly significant strength gains (mean strength gain, 174 ± 31 percent) following an 8-week high-resistance exercise training program, but they did not measure functional locomotor benefits or the real-life role changes, if any, that resulted.

Using cardiopulmonary and musculoskeletal outcomes measures, Morey et al. (1989) reported significant improvements in endurance, strength, and flexibility following regular exercise for 49 elderly people with chronic diseases including arthritis, heart or lung disease, and diabetes. By contrast, Thompson et al. (1988) reported that 16 weeks of exercise among 22 elderly people with hypertension, chronic obstructive pulmonary disease, or osteoarthritis resulted in no changes in cardiopulmonary performance, timed tasks, balance tests, and extremity muscle performance. One of the few extant studies showing a clear relationship between isokinetic strength and objectively tested gait and locomotion variables was limited primarily to young subjects following knee arthrotomy (Krebs, 1989).

Lord and colleagues (1993) used retrospective data to suggest that strength exercises engender better balance and gait in women ages 57 and older. Gehlsen and Whaley (1990), however, reported a low correlation between balance and strength outcomes in elderly subjects divided into fallers and nonfallers. Judge et al. (1993b) reported that gait measures improved insignificantly among 31 exercising elderly subjects (mean age, 82.1 years); self-selected gait velocity improved 8 percent, but maximal gait speed increased only 4 percent. Judge and colleagues (1993a) did find that combined exercise training (resistance exercise, brisk walking, postural control, and flexibility exercises) produced improved balance outcomes compared with those from flexibility exercise training among 21 women with a mean age of 67.8 years.

No study has examined the extent to which potentially destabilizing postural compensations for weakness, such as excess abductor lurch or forward trunk rotations, are ameliorated following strength gains.

Balance Impairment Relationships to Locomotor Functional Limitations

Rehabilitation scientists have begun to study whether exercise improves impairments and performance of ADL; the important missing component that should be addressed includes the relationship of impairments

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

and disabling conditions to compensatory mechanisms and functional limitations. Whole-body locomotor studies provide insight into postures substituted for or compensatory mechanisms for lower-limb weakness or other impairments.

One third to one half of all people over age 65 experience a fall, many of which are injurious, and most occur during locomotion (Overstall et al., 1977; Baker and Harvey, 1985; Pentland et al., 1986; Tinetti and Ginter, 1988). To date, most investigations of "balance" have investigated standing-still activities alone. Although compensating for an internal or external perturbation while trying to stand is still important, most exercise treatments have been developed in part because standing still is easily measured by timed tests or with force plates (Heitmann et al., 1989). Few facilities are capable of measuring whole-body posture and momentum during locomotor studies.

No studies have described objective changes in gait, balance, or locomotor function from exercise interventions among patients with cerebellar disorders (CbD). Rehabilitation of individuals with acute CbD has included the use of Frenkel's exercises, rhythmic stabilization (Littell, 1989), and walking aids and weights (Urbscheit, 1990; Morgan, 1975). Frenkel's exercises were the earliest exercises used to reduce lower-limb dysmetria. Frenkel's exercises can be performed in the supine, sitting, or standing position and can involve performance of slow active movements by the subject while the subject is carefully watching the extremity. Kabat described proprioceptive neuromuscular facilitation in 1955, including resistive exercises that were used to develop strength, endurance, balance, and gait (Littell, 1989). However, no systematic research studies of the efficacy of proprioceptive neuromuscular facilitation for patients with CbD have been reported. There is sparse evidence of successful treatment of chronic CbD, and it has been regarded as a condition refractive to treatment (Sage, 1984). Generally, rehabilitation intervention in individuals with chronic CbD has been restricted to substitution strategies and conservative management, such as recommending that affected individuals increase their base of support or use assistive devices (such as canes and wheelchairs) to improve stability and maintain their range of motion.

Most treatment-related publications lack adequate intervention descriptions. Balliet et al. (1987) were among the first investigators to propose neuromuscular retraining methods. They described five patients with chronic CbD and gait disorders who reacquired "proper motor control and associated balance through slow, successive adaptation to increasingly demanding conditions" (Balliet et al., 1987). All 5 individuals improved on all variables measured; however, the overall treatment duration varied from 3 months to 2 years. Brandt and colleagues (1981)

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

proposed similar ataxia treatment by progressively increasing body instability to activate "sensorimotor rearrangement."

To make rehabilitation science a secure and reliable science, descriptions of rehabilitative treatments are needed, as are more investigations of the benefits of such treatments to whole-body, functional locomotor performance.

Mobility and Ambulation

Many disabling impairments involve the lower limbs. The IOM report Disability in America indicates that mobility limitations make up the largest area of disability in the American population (38 percent). Because mobility is so important to general health (physiological and psychological), it is of much significance to rehabilitation. The ability to walk can be restored or assisted through the use of ambulation aids such as leg prostheses, leg orthoses, special shoes and shoe inserts, canes, crutches, functional electrical stimulation, and walkers. Engineering and technology, when combined with appropriate surgical management, with appropriate prosthetics and orthotics assistance, and with proper therapy and training will be able to advance the area of aided-ambulation at a rapid pace. Upright mobility can be significantly improved for persons with spinal cord injury, cerebral palsy, spina bifida, stroke, and other conditions through better engineering understanding of the biomechanics of walking and of aided walking.

Ambulation Restoration of Mobility has been one of the big successes of engineering in association with professionals in the fields of prosthetics and orthotics. Today leg amputees and persons with leg impairments ambulate with a speed and grace that was unthinkable at the end of World War II. In the 1996 Paralympics a bilateral leg amputee ran the 100 meter dash in 11.32 seconds. In limb prosthetics (artificial legs) and orthotics (limb and spinal bracing), biomechanics, biomaterials, materials engineering, bioelectronics, and other engineering areas are having increasing impact on the ability of persons to ambulate efficiently. Even more impressive perhaps have been the engineering advancements made with human joint replacements, particularly at the knee and hip. Bioengineering in combination with physicians and surgeons have had extraordinary success in the improvement of ambulation and the relief of debilitating pain in persons with severe arthritic joint conditions.

Future Needs and Best Strategies

Much of the locomotion literature concerning clinical evaluation has focused on time-distance gait measures or, at best, has emphasized only

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

lower-extremity kinematics during gait. A number of studies have reported on differences between the gaits of young and old people that can be summarized follows: older people walk more slowly (Sudarsky, 1990). The most obvious conclusion to be drawn is that tests of exercise interventions among people with balance problems must include (although not necessarily be limited to) whole-body locomotor tests. A more subtle problem with current gait assessment is that studying lower-limb movements (kinematics) and forces (kinetics) can reveal only details of human locomotion. Hence, because most studies of the human gait have focused on these details, the few extant treatments that even address locomotor stability focus on the role of the lower extremities. The upper body's mass accounts for roughly two thirds of the total body mass, and its center of gravity (CG) is located nearly two thirds of the person's height above the ground (Winter et al., 1990). Ignoring upper-body dynamics provides at best an incomplete picture of locomotor functional limitations.

During dynamic activities such as locomotion, the body's mass must be displaced outside its support base, requiring either good muscle strength or compensatory postures. The key difference between static balance and dynamic stability is that static balance assumes the center of gravity control within the base of support, whereas dynamic stability encompasses CG control outside the base of support as well, such as in gait and stair climbing. Even standing still is not truly static; CG is in constant motion. Although the static standing impairment of excessive postural sway may contribute to a better understanding of standing balance, more research is needed to determine if static standing is related to dynamic locomotor stability. If so, then a continued focus on improving static standing may be beneficial for people with balance disorders; if static standing sway (impairment) improvements are not related to dynamic functional locomotor performance, then current impairment-level interventions should be abandoned.

More studies of whole-body locomotion during naturalistic gait, rising from a chair, climbing stairs, and other locomotor ADL should be investigated following the implementation of interventions to determine the relevance of such impairment rehabilitation to whole-person functional limitations (Krebs and Lockert, 1995).

The engineering design of technologies for aided ambulation is inhibited by lack of an effective theoretical and scientific foundation for human gait. The deep understanding of walking necessary to guide the design of ambulation technology for people who have walking impairments is still not available. The work needed to assist people with mobility limitations, whether through engineering, surgery, physical therapy, drug therapy, functional electrical stimulation, or some other approach, is handicapped by this lack of a theoretical foundation on which to base new designs.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

Similarly, gait analysis studies cannot be really effective until there is a scientific paradigm that scientists and engineers can agree upon and work under. Less complex and lower-cost gait analysis instruments cannot be created until it is known what key variables should be measured. Although orthopedic surgeons have used gait analysis measurements to guide some decisions associated with the surgical management of children with cerebral palsy, the decisions could likely be much improved if a strong theoretical and scientific basis for human walking existed. It should be possible for future gait analysis data to be used in ambulation studies the way that electrocardiographic analysis is used in cardiology.

The field of orthotics has much unmet potential for ambulation assistance. There does not seem to be any technical reason why people who require orthoses cannot ambulate more rapidly, with more assurance, and with less expenditure of energy than is typical today. Improved understanding of human ambulation will enable functional electrical stimulation to be used more effectively. The orthotic field in general can be complemented with new engineering ideas and with advanced materials and fabrication techniques. Engineering and technology can improve upright ambulation of elderly people, reduce morbidity due to falls, provide better artificial limbs, walkers, and canes, and prevent foot ulcerations by creating improved footwear. In addition to restoring mobility, engineering and technology can be used to accurately measure human performance and to provide objective measurement systems for the evaluation of functional outcomes and for the evaluation of risk factors (e.g., risk of falling). In other cases, engineering contributes to mobility in another way: wheeled locomotion (see Box 5-1).

Manipulation and Physical Control

The hand is more than an unusual instrument of grasp and manipulation; it is also an important sensory organ (e.g., for touch and sensing temperature), as well as an important organ of communication (e.g., for touching, gesticulation, and making signs). The importance and the varied roles that hands play in people's lives make restoration, repair, care, or replacement of a damaged or dysfunctional hand an extremely important area of rehabilitation, that often involves psychological assistance as well as skilled surgical and rehabilitative care to maximize functional abilities.

The human hand is a complicated mechanism, and hand surgery has been one of the most successful approaches to caring for an injured or disfigured hand. Hand surgery is an advanced specialty within orthopedic surgery and involves not only hand repairs but also reconstruction of the hand to create new functional holding and grasping patterns. Recon-

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

BOX 5-1

Wheeled Locomotion

Body-powered, wheeled locomotion is an engineering success story of this generation. The performance of modem wheelchairs has advanced dramatically, and this advance has resulted from work by wheelchair users, research engineers, and designers in commercial companies. Wheelchair racers can now beat the best world-class runners In all races 800 meters and longer and the margin of victory increases as the length of the race gets longer. People such as these top athletes with limb paralysis, some with engineering degrees, have shown by using mobile, reliable, lightweight wheelchairs how technology can be used creatively in the lives of people with disabling conditions.

Many improvements can still be made, however Weight can still be reduced without reducing reliability or other features. As people who use wheelchairs age, they may need lighter chairs to maintain the same level of mobility. Hybrid wheelchairs that use some body power and some electric power also have considerable potential, especially in work situations.

Comfort and prevention of secondary conditions are continuing issues with wheelchairs. Appropriate seating and positioning technologies have emerged over the last few decades for wheelchair users. These systems have improved function for the user and have helped to prevent secondary conditions due to improper positioning of the body or inappropriate tissue loading during sitting The technology for customized seating is now highly automated, and new use of the materials and mechanisms has resulted in greatly improved seat cushions and the creation of proper seating support systems. Nevertheless, the creation of proper seating and positioning is still largely an empirical art that can be significantly enhanced through science and engineering

Powered wheelchairs have advanced rapidly since federally funded research programs demonstrated new design possibilities and highlighted the deficiencies and limitations of the few Systems that were available in the early 1970s Nevertheless, current powered wheelchairs are often heavy and bulky and are difficult to control easily, for example, by people with high-level spinal cord injury who do not have the use of their arms, hands, or feet for control of the chair. Since powered wheelchairs are so heavy and large, they frequently require large vans for easy accommodation and are sometimes too large for small dwellings. Smaller powered wheelchairs are needed

struction may involve transfer of toes to the hand When coupled with good therapeutic follow-up—often by occupational therapists—remarkable rehabilitation of hand injuries can be achieved

Amputation may be preferable when a hand is severely damaged because in the end surgery may not be successful, particularly from a functional point of view, and because over long periods of time surgical repairs can be debilitating and can keep patients from moving along with their lives Decisions concerning amputation are almost always difficult to make and should be based on common sense, experience, consultations, and careful deliberations

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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Hand surgery and hand rehabilitation are largely based on empiricism. Rehabilitation science and engineering will be able to enhance understanding of hand biomechanics, hand surgery, replacement parts, hand orthotics, and hand therapies and thereby enhance the hand and arm rehabilitation process.

Impairment Relationships to Functional Limitations

Arthritis is a common disabling pathology of the hand. Joint replacements for the fingers are still not as successful as they should be. The benefits of different kinds of physical medicine therapies for arthritis need further study.

Disabling conditions of the hand or arm system due to stroke, spinal cord injury, and brachial plexus injuries may be mediated through therapeutic techniques such as exercises, range-of-motion equipment, electrical stimulation, functional training, compensatory skill development, and splinting. Therapies should be used to keep the hand and arm supple and flexible, to avoid secondary conditions due to contractures and joint adhesions. Functional electrical stimulation is showing promise for controlling hand function in paralyzed hands following high-level spinal cord injury. Hand orthoses and orthoses for the arm can be helpful but are mostly successful only from a therapeutic (e.g., protection of joint tissues) rather than a functional viewpoint. The functional gains resulting from arm orthoses are often not great enough to compensate for the disadvantages of current arm orthoses, particularly those for the nonsensate flail limb. Arm orthoses are currently mostly of external design. It may be that internal designs based on surgical revisions, muscle transplants, electrical stimulation, and the implantation of artificial tendons (spring-like devices) could be successful, but time costs and benefits of such procedures would need to be considered closely. The disadvantages resulting from possible long periods of recuperation from surgery and rehabilitation also must be taken into account.

Environmental modifications based on good ergonomic practices and the use of protective devices can help avoid hand injuries or conditions such as carpal tunnel syndrome, arthritis, and trauma due to repetitive actions of the hand and arm during work or recreational activities. Similarly, the environment can be modified to enable dysfunctional hand to be functional through the use of lever handles on doors and on kitchen and bathroom faucets. Special tools such as devices for helping with the removal of jar lids, reachers for picking up light objects at a distance, and sliding boards in the kitchen that enable heavy objects to be safely moved from a countertop to a serving cart without heavy lifting are examples of environmental modifications. Modifications of living environments so

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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that working surfaces are easily accessible, so that one does not have to reach for items above the shoulder level, or so that electrical outlets are available at convenient heights are ways to solve problems associated with poor hand or arm function.

Eating is important in social relationships, and being able to eat independently is a matter of dignity for many people. Consequently, the ability to eat with some degree of gracefulness and with a high degree of independence is an important ability for many people with impairments. Engineering and rehabilitation science has made a few inroads in the section of this field that is concerned with bringing food from the plate to the mouth, but much needs to be accomplished. One approach is the use of personal robots to pick up food and make it conveniently available. Another approach, when the lower limbs can be controlled, is to couple use of a leg or a foot through a linking mechanism to guide food to the area of the mouth. Both of these approaches have had limited success so far. A hybrid approach that uses some robotic features and some direct body-control features may perhaps be more practical. In any case, eating aids will likely have to be customized to the user in most cases.

Future Needs

Artificial hands, artificial arms, upper-limb orthoses, and robots that assist with rehabilitation provide the capacity for people with disabling conditions to physically manipulate unstructured environments (the kind most of people find on their desks). Artificial hands have made big strides since the 1960s. Control of paralyzed or prosthetic arms is more problematic, as is the control of robotic assistants, but progress is being made in these difficult areas of human-machine interaction. Prosthetic substitution of a hand or arm can be achieved in many ways through current prosthetics technology. Actually, replacement in the physiological sense is not possible, but it is possible to replace the missing hand-arm system with devices that are useful assistive tools for the wearers. Electrically powered prosthetic hands provide arm amputees with strong grip force and fairly rapid motion, and their external appearance has good resemblance to a natural hand. Nevertheless, they would be much more useful if their weight could be reduced by half or more, without the loss of function. Durability and high reliability need to be emphasized. Lighter-weight artificial arms should be a priority, along with lightweight orthoses. Body-powered components are still used by a majority of artificial arm users in the United States, and body-actuated systems should continually be improved. Body control through Bowden cable systems, not unlike the brake cables on bicycles, provide the user with good proprioceptive and sensory control of prosthesis usage. This kind of approach to control can also be advantageous for electrically powered prosthetic

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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systems. The human-prosthesis interface needs to be ergonomically configured so that the user can achieve effective multifunctional control without much mental loading. Bilateral, high-level arm amputees have the most disabling upper-limb losses. Although they are few in number, their needs are great and special consideration (as with orphan drugs) and attention need to be given to the research and development of hand-arm prostheses on their behalf.

Rehabilitation of people with dysfunctional or missing upper arms is a difficult task because of the daunting engineering problems associated with arm and hand replacement or assistance, but also because of the psychological issues that greatly compound the problem. Much more research and development work is needed in the field of hand and arm rehabilitation, work that brings engineers, surgeons, physicians, and therapists together with the injured person so that problems that are priorities can be articulated and so that important problems that appear to have feasible solutions, that would be achievable within a reasonable time frame can be worked upon in a creative fashion.

Expertise needs to be increased in this area of rehabilitation engineering and occupational therapy. This expertise will lead, if not to theories, at least to general principles that can guide people with information and ideas on how to best provide eating assistance to the people who need it. Experimental technical equipment for this purpose needs to be developed and tested in close conjunction with the users, caregivers, and occupational therapists skilled in this area. The problem is somewhat similar to the provision of effective artificial arms for high-level bilateral arm amputees so that they can eat and do other thing independently. Occupational therapists have many tools and utensils with modifications that can assist people with managing foodstuffs, but these devices can be expanded and combined, where needed, with more technical devices of many sorts. Developing devices that work effectively, that are simple to use and not too expensive, that are generally small in size and aesthetically pleasing, and that can be customized for individual needs is a challenge, but one that is not impossible for science and engineering.

Bending and Lifting

Spinal dysfunction in general and back pain in particular, because they limit lifting capacity, are the leading causes of disability and result in lost workdays and restricted functioning related to the societal role. Pain as a cause of lifting functional limitations must be further delineated; most rehabilitation interventions address spinal mobility, trunk strength, and fatigue and deconditioning of peripheral muscle, as well as the cardiovascular system. For example, transporting loads and manual lifting capacity are key to manual laborers' productivity, but their supervisors

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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also lose workdays because of back pain and an inability to transport paper file folders or to perform other light office tasks involving lifting.

Relationship of Impairment to Lifting Functional Limitations

Although few data comparing impairments and gait locomotor function are available, to date no studies have systematically reported on the relationship of specific impairments to lifting functional limitations. A definitional problem may be blamed in part: lifting capacity is an impairment-level measure of strength. Athletes in Olympic weight-lifting trials, for example, are judged solely by the total mass lifted. In people desiring rehabilitation, functional lifting capacity may be impaired by a lack of coordination, a lack of limb or spinal flexibility, a lack of movement speed, hypertension and other diseases and impairments that contraindicate Valsalva maneuvers, and pain, in addition to primary strength impairment such as that which occurs following neuropathy or muscular dystrophy. Therefore, in rehabilitation lifting impediments are considered in the context of daily activity limitations, including their restrictions on vocational and other social role functions.

Measurement of the disability caused by lifting limitations is relatively straightforward. Once the cause is defined as a lifting limitation, economic analyses of lost workdays and cost to society are quite direct (Troup, 1965). One of the major problems in determining lifting functional limitations, however, is the lack of standard, objective measures that can be applied by employers, insurers, and governments. Indeed, most employment disability eligibility determinations are performed by physicians with little or no data other than the patient's subjective complaints. Although one can take the position that reliance on the patient's assertions should be sufficient to determine eligibility for benefits, including paid time off, the experience of Scandinavian and, more recently, Polynesian social democratic societies is that such practices can prevent an equitable distribution of resources to other people with physical limitations (Moore, 1996). Hence, a ''job test" that could objectively determine if the same or some less demanding job can be performed would benefit rehabilitation and society substantially. Indeed, any test that could be used to relate strength, range of motion, and other impairments to lifting functional limitations would provide an important improvement to rehabilitation strategies.

Future Needs and Best Strategies

Most prior and current research on lifting in general and back pain in particular focus on impairment and capacity measures, typically focusing

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

on leg and back strength. Lifting style and coordination have received scant attention, probably because they require a whole-body, functional limitations level of analysis. For example, Hagen et al. (1994) reported that workers often prefer the more back-straining technique of lifting with the back because they are less metabolically costly than the correct techniques of lifting with the legs. As the lifted load increases, subjects tend to change from lifting with the legs to lifting with the back, further thwarting the advice of rehabilitation professionals (Schipplein et al., 1990). Hence, more research is needed to determine the most mechanically efficient and cost-effective means of lifting, with costs being determined for limb and spine wear and tear as well as metabolism (Luepongsak et al., in press).

Many resources have been devoted to research on the psychological factors that prevent a return to work following acute low back pain studies (Fordyce, 1995): it is now widely accepted that workers return to work if they get along well with their supervisor (Bigos et al., 1992). These psychological studies, however, typically ignore the impairment and functional limitations levels of analysis. For example, a double-blind study of chiropractic versus conventional medical care (Carey et al., 1995) reported the effects of various pathologies and impairment-level interventions on return to work and the Survey of Income and Program Participation (SIPP), but functional limitations were assessed only by asking patients "whether they had returned to their previous functional status." Hence, Carey et al. (1995) may have wrongly concluded that chiropractic care is just as effective as conventional medical care because the appropriate functional measurements were not obtained. An inability to validly quantify lifting functional limitations is an important shortcoming of the rehabilitation research arena (Vasudevan, 1992; Fordyce, 1995).

An important problem in lifting research is measuring impairments such as strength and mobility, but reporting these as if they are functional limitations measures. Functional limitations reports must include the context and environment in which the person was asked to perform the lifting. Clearly, isometrically pulling a floor-mounted cable tensiometer in a quiet laboratory is very different from lifting materials in an unpredictably busy construction site.

In summary, substantial research resources should be devoted to determining the relationship between the easily studied pathology and impairment measures of lifting capacity and the functional limitations induced under more natural, usual conditions in the workplace where lifting is performed. Objective measures that are not effort dependent and, especially, that are not dependent on the person's psychological state must be developed.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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Eating

Difficulty eating is characterized by problems with chewing, swallowing, and digesting food. In traditional rehabilitation research, issues of dysphagia and drooling are notable, and these two topics are covered here. It should be noted that by this definition, the ability to eat is independent of the ability to hold and use utensils. Problems with the use of eating utensils is covered above in the section "Manipulation and Physical Control."

Impairment Relationships to Functional Limitations

Dysphagia is difficulty in eating as a result of disruption in the chewing and swallowing process. The inability to swallow without coughing or choking, and the inability to control drooling with or without eating can be caused by a variety of impairments and diagnoses. An estimated 6 million to 10 million Americans have been found to have some degree of dysphagia. It has been reported that more than 40 percent of patients in acute-care rehabilitation settings have dysphagia (Logemann, 1995).

The coordinated swallowing process is divided into three stages, and impairments can be noted at any and all three stages (Noll, Bender, and Nelson, 1996). The first phase, the oral stage, is chewing and preparation of a food bolus for transport. It requires proper oral motor structure activity for lip closure, tongue mobility, mastication muscle function, and saliva production. The pharyngeal stage is the second stage and involves food bolus transport without aspiration. More coordinated oral motor pharyngeal structures must be intact to prevent oral and nasal regurgitation, to prevent tracheal aspiration, and to allow bolus transport through the pharynx. The pharynx is a used for both deglutition and respiration. Hence, prevention of regurgitation and aspiration is of significance. The third and final stage is the esophageal phase, which completes the bolus transport to the stomach with limited gastroesophageal reflux. This stage inquires coordinated peristalsis of the esophagus and control of the esophageal sphincter.

The organization of deglutition is generally highly complex. The process requires an intact central and peripheral sensory input, a functioning coordinating center, and a subsequent motor response. Impairments at any stage from mechanical or neuromusculoskeletal disorders, and with consideration of age and state of development, can result in an eating functional limitation. Dysphagia can result from congenital or acquired central neurological disorders (e.g., stroke, cerebral palsy, traumatic brain injury, or polio), treatment for head and neck cancer, progressive neurologic diseases (e.g., Parkinson's disease, myasthenia gravis, motor neuron

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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disease, multiple sclerosis), or systemic diseases (e.g., scleroderma or dermatomyositis).

Drooling is an inability to manage secretions. This problem involves impairment at the oral stage and as in dysphagia, requires a certain level of cognitive function. Drooling can often be seen in individuals with cerebral palsy, traumatic brain injury, stroke, and mental retardation. Often, an association between drooling and dysphagia is found.

Current Status of Science and Research

The majority of research has been in documentation of the impairment, visualization of treatment strategies, and case reports or case series identifying the problem or evaluating interventions. Logemann has contributed significantly to this body of literature (Logemann, 1983).

Technical assessment of dysphagia has progressed considerably with this research. Visualization techniques have allowed investigators to have a better appreciation of the phases of swallowing and has allowed knowledge related to pathology and impairment to progress. Videofluoroscopy of swallowing (modified barium swallow study) has become the diagnostic tool of choice (Splaingard et al., 1988). The procedure has been standardized and individualized (DePippo et al., 1992; Gray et al., 1989), and seating issues for the study have also been addressed (Cameron and Guy, 1990). Other imaging techniques have been explored (Holt et al., 1990; Langmore et al., 1991; Silver et al., 1991; Schima et al., 1992). Positional or textural intervention strategies are also viewed by videofluoroscopy to determine success (Johnson et al., 1992; Rasley et al., 1993).

Dysphagia in people with specific disorders has been better described. Dysphagia in individuals with cerebral palsy, stroke, and brain injury have been studied the most. Dysphagia in people who have had a stroke has been reported to be as high at 30 to 45 percent (Horner et al., 1990; Teasell et al., 1993). The occurrence of dysphagia in individuals who experienced a brain injury is reported to be about 27 percent, and cognitive impairment is often the most significant factor (Winstein, 1983). Children with cerebral palsy often require treatment programs that address tonal abnormalities, postural control, adverse behavior, and primitive reflexes, along with the specific oral motor dysfunctions (Morris, 1989; Morton, 1993). Aspiration pneumonia and malnutrition are common secondary conditions associated with dysphagia (Sitzmann, 1990; Martin et al., 1994).

Review of interventions include compensatory strategies, direct treatment strategies, and surgery, which often result in reduced aspiration and pneumonia, improved nutrition, and improved quality of life and socialization (Logemann, 1995). Compensatory strategies such

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

as postural techniques of head turning or body positioning can eliminate aspiration of thin liquids in about 75 to 80 percent of people with dysphagia (Logemann, 1983). Exercises designed to facilitate oral motor strength and coordination, to facilitate a swallow reflex, and to desensitize oral structures have been described, but with limited supporting research (Braddom, 1996). Surgical interventions are focused and individualized; other than those have received tracheostomies, few individuals who have received surgical interventions have been studied and generalization is difficult (Baredes, 1988; Lindgren and Ekberg, 1990).

Interventions for drooling include oral motor exercises, behavior modification programs, medications, and surgery. Case series and controlled studies are at the base of the research. Behavior modification programs require reenforcement. Medications with anticholinergic properties have been helpful, but not universally.

Future Needs

More rigorous research is needed to determine the effectiveness of interventions for dysphagia and drooling. In particular, exercise and direct feeding techniques need to be evaluated in a controlled manner and over an extended period to determine their efficacy.

Videofluoroscopy is used diagnostically, and in some cases periodically, for ongoing evaluation but standardized interpretation is lacking. The indications for its use initially and for periodic follow-up have not been determined. In addition, individuals with acute and chronic conditions may have different requirements.

Issues of cost-effectiveness for diagnostic testing and interventions have not been defined. Suggestions of cost-containment are based on projections and limited hospital costs. Standardized outcomes measures regarding functional limitations are needed for better comparison of different studies and different interventions. Finally, research is needed to determine the impact of different interventions on disability and quality of life, particularly over a lifetime.

Elimination

Bladder

A pathology of the central or peripheral nervous system's supply to the bladder may result in a neuropathic bladder or, as it is more commonly termed, a neurogenic bladder. The neurogenic bladder has partial or total loss of normal function (impairment), which may be caused by

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

different types of pathology such as spinal cord injury, stroke, multiple sclerosis, or a tumor.

Micturition or voiding requires fine coordination between the bladder and the urethral sphincter such that bladder contraction is associated with urethral sphincter relaxation. Any pathological process that causes a neurogenic bladder may result in the following problems or functional limitations: (1) the inability to void voluntarily, (2) the inability to empty the bladder completely with voiding, (3) the inability to remain continent of urine between voids, (4) the inability to sense bladder fullness, and (5) the inability to inhibit the urge to void.

Bladder Impairment Relationships to Functional Limitations

Urinary incontinence (UI) affects approximately 13 million Americans and 30 percent of those over age 60. Estimates of the cost of managing this problem are $15 billion annually (Agency for Health Care Policy and Research, 1996). The etiologies of UI vary. Although much research on the best methods for treatment has been conducted, less is known about the relationships of UI to functional limitation or disability. In one of the few studies to address the impact of UI on function, McDowell et al. (1996) described the characteristics of UI in 90 homebound adults over 60 years of age with good cognitive skills. The subjects had a mean age of 75.8 years and reported a mean of 8.4 medical problems, and 80 percent had functional limitations in ambulation. Eighty were women and 10 were men. The majority (73.3 percent) had more than 10 episodes of UI per week. About half (54.4 percent) reported that UI further restricted their activities, and 52.2 percent reported that UI was extremely disturbing. However, 90.5 percent believed that UI could be treated.

Most studies of interventions for UI do not use a functional outcomes measure to determine success but often count the number of pads used, the number of leakage episodes, or the amount of leakage. Geriatric patients with urge incontinence lose different amounts of urine and respond differently to pharmacological treatments. Some of the factors that predict the severity of UI are underperfusion of the cerebral cortex, reduced bladder sensation, and impaired orientation (Griffiths et al., 1996). In a descriptive study, 251 consecutive geriatric patients admitted into a geriatric rehabilitation unit received medications and teaching about medication during each daytime administration of medication by nurses. The authors reported a decrease in the incidences of UI and urinary retention and an increase in the level of knowledge about medication regimens (Resnick et al., 1996).

Complicating matters is a trend to avoid seeking health care for such problems. Talbot and Cox (1995) examined 117 adults ages 58 to 93 who were mentally competent, not confined to bed, and residing in the com-

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

munity. The subjects were divided into three groups: those with dysfunctional continence (ineffective coping mechanisms; 28.2 percent), those with functional continence (effective coping; 32.5 percent), and those with UI (39.2 percent). Coping methods were determined with a four-point Likert-like scale. A total of 73 to 85 percent of the groups with dysfunctional continence and actual UI never talked to any health care provider about their UI-related concerns.

Many older adults with UI or other problems of bladder control are deterred from seeking treatment by factors such as social disapproval and a belief that bladder symptoms are normal or untreatable (Umlauf et al., 1996). Elderly people who experience loss of bladder or bowel control are frequently depressed, isolated, and fearful of being discovered. Left untreated, these individuals are prone to mental and social deterioration that may lead to social isolation or institutionalization (Gray et al., 1996).

Quality of Life and Urinary Incontinence A few studies have begun to examine the issue of quality of life and UI. In one study pelvic floor electrical stimulation therapy daily or every other day was effective in treating genuine stress incontinence. No differences in leakage episodes, pad count, leakage amount, subject subjective assessment, and quality of life were found comparing daily and every other day electrical stimulation (Richardson et al., 1996).

A self-report quality-of-life measure specific to urinary incontinence (I-QOL) was developed and tested for its validity and reproducibility with a group of 62 people with UI (Wagner et al., 1996). The I-QOL, developed as an outcome measure for clinical trials and patient care, was compared with measures of psychological well-being and functional status (Short Form 36-Item Health Survey). The I-QOL was more sensitive at detecting levels of self-perceived UI severity than either the psychological general well-being or the Short Form 36-Item Health Survey).

Jackson et al. (1996) developed the Bristol Female Lower Urinary Tract Symptoms questionnaire that is sensitive to changes in the symptomatology of the female lower urinary tract, particularly UI, providing an instrument that can characterize symptom severity and effect on quality of life, and that can evaluate treatment outcome.

Functional Limitations and Disabilities The function of the bladder should be viewed from the total aspect of the person's ability to function in the society in which he or she lives (Cardenas, 1992). The expectations of society are that older children and adults can maintain continence and empty the bladder at acceptable intervals, usually not more than once in 3 to 4 hours. Certain working conditions are less conducive to frequent voiding, for example, truck driving and assembly line work. People with

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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neurogenic bladders who must void frequently, even if they are ambulatory, might become disabled in such a job setting. In other job settings toilet facilities may not be wheelchair accessible. The most obvious examples are portable toilets at construction sites, but even some office buildings have minimal or no wheelchair-accessible bathrooms. The person with a neurogenic bladder who is unable to void and performs intermittent catheterization, one of the preferred methods of drainage from a health perspective, is often using a wheelchair for mobility and thus needs access to an adequately constructed wheelchair-accessible bathroom. If the job site or office building does not offer a wheelchair-accessible toilet, such people also become disabled because of a nonaccommodating environment.

Another alternative to bladder emptying used by some people with neurogenic bladders is an external or an internal indwelling catheter that is connected by a tube to a plastic receptacle (leg bag). Even with such a system, emptying the plastic bag is necessary after several hours of filling. Again, a wheelchair-accessible toilet is needed or the person will likely become disabled.

The following case report exemplifies the predicament of people with disabling conditions. A young man with a spinal cord injury that resulted in paralysis of most of the muscles of his arms and all of his trunk and leg muscles was hired at a bank in an urban community. The bank building did not have a wheelchair-accessible toilet, and the young man managed his neurogenic bladder by performing intermittent catheterization every 6 hours. He was forced to go to his wheelchair-accessible vehicle, a van, in the parking lot each midday to perform intermittent catheterization. As society complies with the legal mandates established under the Americans with Disabilities Act of 1990, increased physical access will allow people with disabling conditions to live and work in environments that allow their full participation.

Related Secondary Conditions More than 1 million nosocomial (hospital-acquired) urinary tract infections occur each year in the United States (Haley et al., 1985), and about half of these originate in the urinary tract in association with urinary catheters and other drainage devices (Kunin, 1994). Although no randomized comparative trials have been performed to determine the relative risks of indwelling catheterization, intermittent catheterization, and condom catheterization in predisposing patients to urinary tract infections, there is a general consensus that the greatest risk is with the use of indwelling catheterization (Cardenas and Hooton, 1995). Most studies on the urinary tract have not been conducted with patients with neurogenic bladders. Long-term complications of neurogenic bladders also have

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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not received much attention. It is known, however, that the incidence of renal failure as the cause of death in individuals with spinal cord injuries has been reduced during the past two decades and that during this period intermittent catheterization replaced indwelling catheters as the major mode of bladder management. Other changes in the treatment of spinal cord injury have also occurred, however, including the introduction of newer antibiotics and formalized systems of rehabilitative care and follow-up. Physiological urinary tract changes over time have received minimal attention. A recent cross-sectional study showed that bladder pressures were lower in those who use intermittent catheterization with a longer duration of spinal cord injury, regardless of age (Cardenas and Mayo, 1995). Adequate longitudinal studies determining the effects of both aging and the duration of impairment of the bladder have not been performed. The roles of health beliefs, nutrition, and hygiene have received minimal attention in the research literature on the prevention of urinary tract infection in patients with neurogenic bladders.

Future Needs Research is needed not only to determine optimal strategies for bladder management but also to determine the educational needs of primary care providers in the appropriate management of urinary tract infections in those with neurogenic bladders. Research is also needed to determine the optimal duration of antimicrobial treatment of urinary tract infections in the person with a neurogenic bladder.

Longitudinal studies are needed to determine the long-term consequences of asymptomatic bacteriuria for the neurogenic bladder. Funded workshops are needed to train urologists in the state-of-the-art surgical options that may reduce the functional losses of the bladder, such as electrode implantation. New stimulation methods and approaches for the control of micturition and defecation are making bowel and bladder continence practical for persons with spinal cord injury and other pathologies. Dramatic advances are possible and should be pursued. Research is needed to determine the best prevention strategies for complications associated with a neurogenic bladder. Such secondary conditions include urinary tract infections; stones in the kidneys, ureters, or bladder; and renal insufficiency. Research on methods for changing the role expectations of employers and others toward the person with a neurogenic bladder, and on newer pharmacological agents or other treatments that can improve bladder functioning, including UI is also needed.

New electrical stimulation methods and approaches for the control of micturition and defecation are making bowel and bladder continence practical for people who have sustained spinal cord injuries and those

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

with other pathologies. Investigators have devised technical stimulation methods that can stimulate small nerve fibers before they stimulate the large nerve fibers. This stimulation approach, along with other techniques, promises to provide dramatic advances in the voluntary control of micturition and defecation through the use of implants and small external technical apparatuses. Engineering and medicine appear to be on the brink of making significant practical advances with these technologies. These potentially major breakthroughs may dramatically alter the future care of people with bladder and bowel control problems.

Bowel

Functional Limitations The normal function of the bowel, like the bladder, may be altered by various types of pathologies, especially those that cause primary damage to the central nervous system and autonomic nervous system. This can result in the loss of the urge to defecate or an inability to inhibit a bowel movement. The impairment is the loss of normal bowel function, whereas the functional limitation relates to the possible loss of the normal ability to sit for prolonged periods of time without a potential "bowel accident," to loss of the ability to travel, and to a loss of potential cleanliness and personal hygiene.

An uncontrolled bowel movement with fecal incontinence may lead to loss of employment. The expectation of society is that older children and adults will not have fecal incontinence or soiling that can produce odor and lead to leaving the job task at hand to clean up and change clothing, tasks with which a person with a neurogenic bowel may require assistance. The person with a neurogenic bowel who has difficulty controlling "bowel accidents" may thus have a disability.

Historically, occupational therapists have worked with clients, their families, and caregivers to facilitate use of the bathroom and toilet for elimination of wastes and bathing, washing, brushing, shaving, etc. As with systems for assistance with eating, bathrooms must be customized for people with disabling conditions, their families, and their assistants. Again, as with eating assistance, there is a need to develop principles of bathroom treatments, if not theories, that will help guide families, architects, carpenters, and plumbers in creating customized facilities that make ergonomic sense, that can be altered as the level of disability increases or decreases, and that are compatible for use by other members of the family (universal design). Sensitivity needs to be given to issues of privacy. Independence of use needs to be maximized where possible. Engineers, architects, therapists, and others need to give more attention to the bathroom and toilet needs of persons with disabling conditions, particularly those people with significant disabling conditions.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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Current Status of Science and Research No data are available on methods for changing the role expectations of employers or others toward people with functional limitations as a result of a neurogenic bowel. Minimal research regarding optimizing bowel management for avoiding fecal incontinence exists, although much clinical experience has provided good bowel care for many.

Future Needs Methods for reducing the time necessary for adequate bowel evacuation need further study. More research is needed on methods of triggering defecation, such as electrodefecation by sacral root stimulation. Additionally, research is needed to empirically examine the long-term effects of aging with a disability in noninstitutional settings, and how to maintain maximal bowel function over the lifespan. Research is also needed on methods for changing the role expectations of employers and others toward the person with a neurogenic bowel.

Sexual Functioning

Functional Limitations

Sexual functioning is an important aspect of human life and well-being. Impairment of sexual functioning may result from disease processes that alter neurological, vascular, or endocrine function such as spinal cord injury, multiple sclerosis, atherosclerosis, and diabetes mellitus, as well as from mental disorders and even common medications used to treat numerous conditions. Sexual functioning encompasses arousal, lubrication, erection, ejaculation, and orgasm. Sexual functioning involves reflex (neurogenic), hormonal, and psychogenic mechanisms that have not been completely described for humans with or without dysfunction. Loss of genital sensation or loss of motor input to the genitalia can result in severe loss of sexual function.

Functional limitations in sexual functioning involve (1) the inability to become aroused or lubricated, (2) the inability to develop adequate erections, (3) the inability to ejaculate, and (4) the inability to experience orgasm.

Loss of erectile function can be treated with various technologies, but not always successfully. Some men do not accept artificial methods for achieving an erection. Others are unable to afford treatment, which is not funded by many health plans. Owing to the role expectations of sexual functioning in marital or intimate relationships, the loss of erectile functioning may result in a disability. The same can be said for the loss of ejaculation, which affects not only sexual functioning but also the ability to procreate naturally. Again, technological advances such as electroejaculation are not always available or affordable.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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Current Status of Science and Research

Research into sexual functioning related to neurogenic or vascular causes has focused primarily on men. For example, estimates of the incidence of erection after spinal cord injury have been determined for individuals with complete injuries according to the level of injury, but the incidence has not been determined for individuals with incomplete injuries. Testicular biopsies have revealed a high incidence of abnormalities of spermatogenesis in those with spinal cord injuries. Pregnancy and delivery may be associated with certain risks such as autonomic dysreflexia in women with spinal cord disorders, but with appropriate obstetrical care, minimal increased morbidity to the mother or baby her infant is achievable (Baker et al., 1992). Orgasm is less well studied than erection, lubrication, or ejaculation. The subjective experience of orgasm is paralleled by certain physiological changes, but measuring these changes has not received much attention in those with a loss of sensation such as may occur after spinal cord injury.

Future Needs

Psychological factors such as stress and anxiety as well as medications can affect all aspects of sexual functioning, but the disability that results is not well documented.

More research is needed on sexual functioning in women with impairments, such as loss of genital sensation, and research is needed to determine the educational needs of obstetricians and family practitioners caring for pregnant women with spinal cord dysfunction. More research is needed to determine the causes of abnormal spermatogenesis and methods for improving spermatogenesis.

Vision

Relationship of Impairment and Functional Limitation

Vision, the most developed sense in humans, provides people with most of their knowledge of the external world (Zeki, 1993). The visual system allows for the visualization of detail (acuity), color, form, movement, depth, and contrast (Livingstone and Hubel, 1987) and contributes to a capacity to attend to tasks of daily living. The visual system is complex and includes numerous structures, from those that receive stimuli from the environment (e.g., the cornea, lens, aqueous humor, and retina) to the areas of the brain where visual function becomes specialized at interpreting and combining stimuli (e.g., the retina, lateral geniculate

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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nucleus, superior colliculus, and the various areas of the visual cortex). Maturation problems, diseases, and injury can cause functional limitations of low vision or blindness. Common impairments are cataracts, macular degeneration, which results in the gradual loss of central vision, and glaucoma, which results in loss of peripheral vision. These impairments often result in disability when they affect driving, reading, taking medications, and walking.

The higher areas of visual performance, the P pathway and the M pathway, can also be affected by disease (dementia of the Alzheimer's disease-associated type and Parkinson's disease), lesions (stroke or trauma), or aging. Insults to the visual pathways can cause the slowing of information processing. The functional impairments that result are impaired depth perception, contrast sensitivity, movement detection, and form recognition. The perception of depth is a complex process involving the unconscious interpretation of multiple visual cues and physiological responses. The primary visual cues are all binocular in nature, meaning that they require the use of both eyes to be effective. One of the most important binocular cues is known as stereopsis. In stereopsis, a phenomenon called binocular disparity occurs, which is a direct result of having two eyes separated horizontally on the head (DeAngelis et al., 1991). The loss of stereopsis can result in falls due to misjudging short distances between objects (e.g., steps) and vehicle accidents (e.g., errors in parking, merging, stopping, and turning across traffic). Loss of these visual processes may contribute to personal-injury accidents. When depth perception is adversely affected by poor lighting, lack of color or visual contrast, or deceptive visual patterns, depth cues send the brain erroneous information about one's immediate environment, and then a loss of function can occur.

Another functional limitation is contrast sensitivity, which is a function of the M pathway and which is the difference in light intensity between an object and its immediate surroundings. People with impaired contrast sensitivity cannot see objects in their environment, and it is believed to be a cause of vehicle accidents. Gunsburg et al. (1982) found that pilots who saw an obstacle from the greatest distances were those who had the highest contrast sensitivities. Pilots who had to get close to the obstacle before seeing it had the lowest contrast sensitivities. People with multiple sclerosis, a disease that attacks the insulation on nerve fibers, complain that the world appears ''washed out." Presumably, this washed-out appearance of the world is related to the nervous system's diminished capacity to code contrast.

Movement detection helps with sight. For example, one may not notice an insect on the wall until it starts to move. Movement can also provide information about form. Motion serves several different percep-

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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tual purposes, including detection, segregation of an object from its background, and definition of an object's shape. The brain sees form before it sees detail. Research shows that types of dyslexia may result from the inability to see form before detail; also, some types of dyslexia result from an individual's inability to detect movement patterns (Frith and Frith, 1996). Parkinson's disease offers insight into how these impaired visual processes affect performance. Hunt et al. (1995) reviewed how Parkinson's disease impairs vision and, consequently, function in reading, balance, driving, and socializing.

Vision: Technical Aids and Advances

Computers and other technologies now enable machines to read printed text and to turn it into speech with considerable ease. Electronic text is easily converted into voice or braille output at reasonable speeds and at reasonable cost. Interfaces for graphical information such as that found on the Internet are being developed. Modern communications systems help facilitate safe travel by people without vision and future geographical positioning systems may be able to provide these people with highly accurate positioning and orientation information. Many technologies such as video magnification and other aids are benefiting persons with partial sight. Restoration of human vision through technical and biological means remains a long-range possibility.

Rehabilitation science and engineering has much potential to assist in the further development of technical aids for people with low vision or blindness. If the science and engineering can be carried out in close proximity to rehabilitation centers for blind people and in close proximity to blind and partially sighted people and their caregivers, the potential for major practical advances is enhanced.

Future Needs

The mechanisms of vision are beginning to be understood. How visual impairments relate to disability and the strategies used to support recovery in individuals with neurological damage provide challenges to rehabilitation scientists. Visual impairments can complicate assessment and rehabilitation. The process of learning required for recovery is best accomplished by a person with good visual and visual processing skills. Visual perception problems are prevalent in people with neurological damage. Vision scientists are not normally involved in the rehabilitation process, so that there is a gap between rehabilitation and vision scientists. This gap should be filled by multidisciplinary research that could lead to improvements in rehabilitation outcomes and in the quality of life for

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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people with functional impairments that, in the absence of proven intervention strategies, have limitations that lead to disability.

Research needs to be done to gain an understanding of how damage to the visual pathways affects disability. This may help in the development of visual training programs, behavioral strategies, and environmental adaptations that can contribute to the optimal functioning of individuals with disabling conditions that otherwise may be ignored.

Hearing

Relationship of Impairment and Functional Limitation

The sense of hearing is used primarily for communication, for localizing sounds in the environment, and for aesthetic purposes such as the enjoyment of music. For most people, the communication function is by far the most important for carrying out the everyday activities of life. The ability to talk relies on auditory capability (Newby and Popelka, 1992) in concert with the capacity for language (Gleason, 1985) and the ability to produce speech sounds (Hegde, 1995). This ability develops naturally and functions effectively when the auditory system, a speech production system, and a central nervous system capable of language are in place at birth. Furthermore, the communication ability will be sustained if these separate systems remain functional throughout life. Thus, the auditory system plays a substantial role in the development and maintenance of the communication ability after oral language and speech abilities have developed.

An impairment of the auditory function affects the communication ability in ways that depend on the magnitude of the hearing loss, when the hearing impairment occurred in relation to the individual's stage of language and speech development, and the portion of the auditory system that is affected. A significant auditory impairment that is present at birth or that occurs before language and speech ability have begun to develop can interfere with the development of language and speech and may affect the ability to communicate. This type of hearing impairment has been termed perilingual and can result in a hearing disability that substantially affects oral communication ability. However, those with prelingual hearing impairments can learn to communicate effectively through the use of sign language. Neither their communication abilities nor their other academic abilities need be affected. In fact, "baby talk" in deaf children raised by signing parents will begin earlier than will baby talk in hearing babies. The key factor here is that early and consistent exposure to signing, lipreading, and speaking can be taught as successfully later as earlier, but linguistic ability will be lost if accessible language is not provided during critical developmental periods.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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A significant hearing impairment sustained in later life, after language and speech abilities have developed fully, is termed a postlingual hearing impairment. This type of hearing impairment does not affect the development of language and speech but can affect the ability to communicate, resulting from an inability to perceive speech correctly. A significant hearing impairment that occurs at a point during speech and language development, termed perilingual, can result in a disability with some characteristics of both pre- and postlingual hearing impairments.

The peripheral auditory system consists of a right and a left side and includes the external ear and a variety of internal structures that process auditory information and send it to the brain. Some of these peripheral structures optimize sensitivity to sounds; that is, they increase the ability of the ear to hear the quietest sounds. Other peripheral auditory structures optimize sound discrimination, which is the ability of the ear to discriminate among different sounds. A peripheral auditory impairment often reduces hearing sensitivity so that sounds may not even be heard. A peripheral auditory impairment also can reduce the ability to discriminate sounds so that, for example, the "t" sound cannot be discriminated from the "d" sound in speech, even if the speech sounds are intense enough to be detected. Virtually all peripheral hearing impairments result in some degree of hearing loss, that is, a reduction in hearing sensitivity, and as a result, sounds must be made more intense for the individual to detect them. In many cases, the peripheral hearing impairment also results in a decrement in the ability to discriminate sounds, so that even if the sounds are made intense enough to be detected, they are still not perceived correctly.

Deficits of central nervous system function that do not involve the peripheral auditory system also may affect auditory capability, particularly regarding the ability to understand speech (Katz, 1994). A head injury or stroke usually does not cause a peripheral hearing loss, but may impair the communication ability related to deficits in the auditory processing capability in the central nervous system. Auditory processing associated with the auditory portions of the central nervous system generally does not include auditory sensitivity or simple sound discrimination, but it does involve more complex processing such as the ability to separate or integrate auditory input from both ears, interpret timing effects such as the temporal order or sequence of auditory sounds, separate speech sounds from background noise, and other kinds of processing that may interact with language functions and even learning and memory.

Hearing loss is defined in terms of hearing sensitivity for particular pitches in each ear and the average hearing sensitivity for speech categorized in increments ranging from mild to profound. Hearing loss is further defined in terms of the ability to understand speech including speech

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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that is amplified enough to overcome the hearing loss and be detected. The disability resulting from the hearing loss involves a consideration of the magnitude of the hearing loss, the measured decrement in speech discrimination ability if any, and many other factors including when the hearing loss was sustained (pre-, peri-, or postlingual), whether or not both ears were affected, and the types of sounds most important to the individual (speech, music, etc.) (Newby and Popelka, 1992). A person with a profound, bilateral, perilingual hearing loss who relies on sign language may not have any disability related to the hearing loss because of his or her reliance on a communication system that does not require auditory function. A person with a severe, bilateral, postlingual hearing loss may be significantly disabled as a result of difficulties in perceiving speech at normal conversational levels. A professional musician with a very mild hearing loss in one ear that may not affect communication ability but that may still reduce the ability to play a musical instrument may be considered substantially disabled.

Some hearing impairments are the result of transient diseases or are able to be corrected with medical or surgical intervention. If the surgical or medical intervention is successful and is invoked as soon as possible after the hearing impairment has been identified, the hearing impairment usually will have no long-term effect on the auditory capability. If, however, the medical or surgical intervention is ineffective or such an intervention is impossible for various reasons, the hearing impairment can be considered permanent and can affect the auditory ability. For people with permanent hearing impairments, rehabilitative strategies other than medical or surgical intervention can help ameliorate the effect of the hearing impairment. If the hearing impairment is severe enough and if it is pre- or perilingual, the educational setting itself is a consideration. Schools for people who are deaf use teaching techniques that foster the development of oral language and speech (oralism), sign language (manualism), or a combination of both (total communication) (Northern and Downs, 1991). These schools teach language and communication ability simultaneously with traditional elementary school subjects; however, those that emphasize oral skills spend a disproportionate amount of time teaching those skills.

For children with auditory impairments who rely on oralism for the development of language and speech or for adults with postlingual hearing impairments whose language and speech skills have already been developed, a variety of technologies are available to assist the impaired auditory system. The first of these is a conventional hearing aid. A hearing aid is a small, portable, battery-operated device worn in the impaired ear. The device has the capability of amplifying sounds in the environment so that they are intense enough to be detected. Furthermore, the

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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hearing aid may be adjusted so that some pitches are amplified more than others and so that the hearing aid is tailored to the specific hearing loss, resulting in some improvement in sound discrimination ability. The use of hearing aids can be a very effective rehabilitation strategy, especially for individuals with mild, moderate hearing impairments and combined with rehabilitation strategies that capitalize on the visual perception of speech (lipreading).

For some individuals with hearing impairments, a cochlear implant may be an effective option. A cochlear implant is a small, portable, battery-operated device much like a hearing aid, but instead of providing more intense sounds, it electrically activates the remaining auditory nerve fibers over wires surgically implanted in the inner ear. A cochlear implant may allow more severely hearing impaired individuals to detect sounds in the environment and, if multiple wires have been implanted, to achieve some degree of sound discrimination ability through the perception of multiple channels of sound information. A comprehensive rehabilitation program that incorporates a cochlear implant may be able to enhance speech development in people with perilingual impairments and to enhance oral communication ability for those with pre-, or postlingual impairments. However, the evidence about cochlear implants remains controversial. It must also be noted that some members of the deaf community feel very strongly that cochlear implants are not needed, especially among children, for whom signing can provide an optimal, comprehensive, and noninvasive communication technique, while others believe that speech production is enhanced by cochlear implants, even in the prelingual deaf.

Much of the available technology can enhance a person's communication ability by using modes that completely bypass the impaired auditory system. Alarm systems such as smoke detectors, fire alarms, door bells, and alarm clocks can be modified to emit signals that can be detected by other senses such as vision (flashing lights) or touch (vibrators). Other technologies permit the simultaneous display of speech as text in closed-captioned television, and telecommunications devices for the deaf display telephone voices as text.

Environments can be restrictive in their accessibility for people with hearing losses, and technology or policies can be invoked to improve accessibility. In larger venues (theaters, churches, stadia, lecture halls, classrooms, etc.) a microphone (lapel microphone worn by the lecturer, classroom teacher, or performer) can be positioned to pick up the acoustic signals of interest and transmit the signals wirelessly to special earphone devices or personal hearing aids worn by the people in the audience with hearing losses. Captioning can be provided in real time for situations in which closed captioning is unavailable or not able to be prepared ahead of time. Public telephones can have amplifiers, hearing aid compatibility,

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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or companion telecommunication devices for people who are deaf. Interpreters for both oral and manual communication can be provided in other situations. Strategies for enhancing visual communication, including lighting and seating positions, may be used.

An auditory impairment can greatly complicate assessment and rehabilitation of other physical impairments. Assessments of cognitive or receptive language ability following a stroke may be based on hearing-based tasks that usually assume that the auditory system is healthy. This is a tenuous assumption because of possible preexisting peripheral auditory pathology. Incorrect responses to certain questions by an individual who has experienced a stroke may be interpreted as a cognitive deficit when in fact the responses may be the result of misperceptions due to a preexisting, mild peripheral hearing impairment, a common condition in people who are elderly.

Hearing: Engineering Advances

Hearing loss, after having normal hearing, is common, particularly among elderly people. Engineering advances have made hearing aids much smaller and more effective than earlier versions. Although hearing aids are useful they have many shortcomings that signal processing theory, technology (e.g., digital processors), and better understanding of the auditory system and its pathologies should be able to improve. The ability to place computers within hearing aids opens up a whole new world for hearing assistance. These new technical opportunities may produce changes in hearing aid performance that are as dramatic in nature as the changes that computers have brought about in society in general.

Future Needs

All of the technological devices mentioned above can be improved. Furthermore, as the technology is improved, behavior-based rehabilitation procedures need to be modified accordingly. Therefore, research projects need to center on both improvements to the devices themselves and improvements related to rehabilitation strategies, particularly as they interact with various technologies. Research projects can be at the cellular level (e.g., development of improved electrodes for cochlear implants), the signal processing level (e.g., development of improved digital processing software for enhancing speech perception with computer-based hearing aids), the assessment level (developing physiologically based techniques for detecting and quantifying hearing impairments in neonates), and the environmental level (developing strategies for supporting the communications abilities of all people).

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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Speech

Limitations of speech include difficulties in voice production and articulation, not in language, content, or structure of communication. The latter group are determined by cognition and are noted in the "Cognitive Function" section. Speech function is characterized by articulation and audibility and ability to produce and sustain a reasonably fast rate of speech.

Impairment Relationship to Functional Limitation

The normal process of human speech is accomplished through controlled and sequenced respiration, phonation, and articulation, with adequate resonance from the cavities of mouth, nose, and pharynx. Voice production through the vocal mechanism is accomplished through active inspiration (through activity of thoracic and neck muscles and intrathoracic pressure changes), and expiration through the larynx that is both passive (muscle relaxation and gravity) and supported (abdominal and intercostal muscle activity) for prolonged exhalation for speech.

Phonation and articulation require steady maintenance of air pressures, balanced vocal cords, and coordinated actions of tongue, lips, jaw, and soft palate. Resonance in the pharyngeal, oral, and nasal cavities are modified by changing the shape of the vocal tract, again requiring intact musculature and intra vocal tract pressure control. The coordination, sequencing, and programming of these activities is directed by the brain, most specifically, the left frontal cortex. An impairment at any organ level involved in the process will influence speech production, and lead to a functional limitation in speech.

Assessment of the impairment focuses on the speech production process. Impairments often occur at varying levels of severity and at numerous points in the process, all of which are interdependent. The speech functional limitation is focused most on intelligibility, and measures have been used to determine intelligibility in the clinic setting (functional limitation). It is recognized that intelligibility scores can be influenced by the speakers' task, the transmission system, and the judges' task (disability) (Yorkston et al., 1984; Yorkston and Beukelman, 1981)

Current Status of Science and Research

There are a variety of conditions that describe limitations in speech. Etiologies for speech limitations can be at a central or peripheral area, can involve motor control, and can be mechanically related. Dysarthrias are characterized by slow, weak, imprecise, or uncoordinated movements of

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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the speech musculature, which results in reduced speech intelligibility. A number of diagnoses can be associated with dysarthria, and includes cerebral palsy, stroke, parkinsonism, multiple sclerosis, brain injury, muscle diseases, and amyotrophic lateral sclerosis. All or several speech subsystems may be involved in varying degrees (respiratory, phonatory, pharyngeal, and articulatory) (Miller et al., 1993). The dysarthrias can be described and diagnosed based on a cluster of features. (Darley, 1969a,b; Rosenbek and LaPoint, 1985). There are a variety of assessments that measure speech performance (Netsell, 1973; Netsell et al., 1989; Gerratt et al., 1991), since intelligibility is the hallmark of functional speech. Most tools are perceptual, and rely on a trained observer. However, at an impairment level, respiratory performance can be measured aerodynamically (Netsell, 1973); acoustic analysis can be performed (Keller et al., 1991); and measures of laryngeal resistance can be obtained (Smitheran and Hixon, 1981). Application of these technologies as a measure of intervention assessment could be helpful, but measures only a limited portion of speech function. Standard tools have been developed to measure sentence and single word intelligibility and speaking rate in a more structured fashion (Yorkston et al., 1984).

Those with severe limitations in speech may require augmentative or alternative communication devices. Treatment goals are to establish a functional means of communication. Systems range from communication boards and books to computer based speech synthesis systems (Brandenburg and Vanderheiden, 1987; Yorkston and Beukelman, 1991). Simple low tech strategies must also be considered and may be preferred. The selection of the most appropriate intervention requires careful consideration of the individual's capabilities (e.g., cognitive function, vision, hearing, hand and arm manipulation, positioning for function), proposed use in the selected environments, and financial issues. Lifelong use of these devices or staging of interventions need to be investigated more fully.

A moderate or mild limitation in intelligibility may require exercises to improve respiratory control (Netsell and Daniel, 1979; Bellaire et al., 1986), change speech rate to improve intelligibility (Yorkston et al., 1990), or focusing on phonation (Ramig, 1992). Effectiveness of speech interventions for individuals with spastic dysarthrias has been documented through case reports, single-subject design studies, and uncontrolled group treatments (Aten, 1988). Study outcomes measure changes in muscle strength and control, reduction in consonant imprecision, and improved intelligibility and speaking rate (Yorkston, 1995). A prosthetic lift at the nasopharyngeal area may improve dysarthria by controlling oral air pressures (Gonzalez and Aronson, 1970). Interventions for per-

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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sons with progressive disorders require changing interventions, based on function (Hillel et al., 1989).

Articulation and phonologic disorders comprise a large portion of speech limitations. Disruptions in speech, or stuttering, vary greatly in frequency, duration, type, and severity. Stuttering is characterized by hesitations, prolongations, and repetitions of speech. Treatment effectiveness studies in school aged children show about a 61% reduction (Conture and Guitar, 1993). In adults, 60 to 80% improve with treatment (Bloodstein, 1987). Treatment approaches are determined by a variety of factors, and may be intensive or extensive (Conture, 1995). Articulation and phonologic disorders are among the most prevalent speech limitation in preschool and school aged children, affecting 10% of this population (Geirut, 1995). Interventions in this age group have been long-standing (Sommers, 1992). Hearing impairments must be considered in the pediatric group in particular when speech delays are noted.

Laryngeal-based voice disorders are characterized by abnormal pitch, loudness, or vocal quality and ranges from mild hoarseness to complete voice loss. Voice therapy can improve the characteristics of voice and reduce laryngeal pathology (Ramig, 1995). Voice treatment has been found to improve vocal nodules and to reduce recurrence if instituted after surgery (Lancer et al., 1988). Speech options after laryngectomies include external prosthetic devices (electrolarynxes and pneumatic reeds) (Miller et al., 1993), tracheal-esophageal puncture (one-way valved voice prosthesis) (Singer and Blom, 1980), and esophageal speech (Gates et al., 1982). Outcome studies have shown both difficulties (Schaefer and Johns, 1982; Miller et al., 1993) and success (Singer et al., 1981; Wetmore et al., 1985; Miller et al., 1993). Technology has assisted speech production for persons with chronic tracheostomies. In particular, the Passy-Muir tracheostomy speaking valve allows speech production through a one-way valve which opens with inspiration, and closes with expiration, redirecting air into the trachea and vocal cords creating sound through the oral and nasal cavities.

Speech: Engineering and Technical Advances

Communication aids for people who are unable to speak came into existence about 30 years ago, and the application of the sciences of information theory, computational linguistics, and coding theory, along with new computer technologies, have had a material influence on the ability of people to generate messages through standard alphabetic notation, speech input, or symbolic methods. Nevertheless, not all people who are unable to speak are able to communicate in these novel ways. Engineering and rehabilitation science can make big advances in this area, as well

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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as in the recognition of speech that is difficult to understand through the translation of utterances into understandable artificial speech.

Cellular telephone links (voice and data), fax services, e-mail, and the Internet have opened up wide communication channels for everyone and it is incumbent upon rehabilitation technology to make these links accessible to people with disabling conditions, using universal design where possible. These communications systems can also provide much assistance to people with sensory losses (e.g., hearing or visual losses).

Future Needs

Currently, the majority of outcome measures in speech rehabilitation are perceptual or observational, and lack standardization. Research into the development of standardized instrumental and observational measures would move evaluation to the functional limitations level. Research regarding the effectiveness of interventions using rigorous descriptions of interventions and outcome measures would provide a basis for duration and frequency of treatments and indications for treatment options. Application of speech intelligibility measures into the disability realm would allow a realistic measure of intervention success.

In addition to the specific areas identified above, research along the lifecourse regarding interventions and devices is needed. Issues of patient and family choices should be considered.

Cognitive Function

Relationship of Impairment and Functional Limitation

The performance of everyday activities is supported by a number of physiological and psychological processes. Cognition represents one of these processes that guides individuals as they acquire and use information to support their actions. Cognition at the impairment level involves the mechanisms of language comprehension and production, pattern recognition, task organization, reasoning, attention, and memory (Duchek, 1991). When these mechanisms are intact, they support the person in learning, communicating, moving, and observing. When the mechanisms are deficient, they create functional limitations for individuals who require rehabilitation services to learn strategies to bypass the deficit or compensate for the loss, or both. They also create functional limitations for the families of such individuals.

Cognitive problems are common following stroke or head injury in people with Parkinson's and Alzheimer's disease and in some people with multiple sclerosis and other chronic conditions. It is the beginning of

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
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a new era in the study of cognition as ''we understand how experiences generate changes in the nervous system that shape our language, our visual world, our coordinated movements, our cognition" (Merzenich et al., 1993, p. 17). It should be the goal of rehabilitation to minimize the consequences of brain injury in the lives of those who suddenly are impaired by difficulties in living, social interaction, family life, and vocational and educational pursuits. The major cognitive deficits that create functional limitations are described below.

Aphasia is the term attributed to difficulties with language comprehension and expression. It is the absence or impairment of the ability to communicate through speech, writing, or signing and may limit the person's ability to comprehend or express language making it very difficult for the person to communicate wants, needs, and ideas to others.

Agnosia refers to problems with pattern recognition. Agnosia can impair the recognition of objects, facial discrimination (Allender and Kaszniak, 1989), and the recognition of voice tone (Eslinger and Damasio, 1986), making it very difficult to recognize familiar people and voices and common objects such as a fork, toothbrush, or razor. Agnosia presents a difficult challenge, requiring rehabilitation and education for the affected individual and the family.

Apraxia describes the deficit that occurs when an individual has difficulty in organizing and executing purposeful movements. Functional limitations occur when the person cannot perform tasks such as putting an arm in a sleeve, reaching for a glass to take a drink, or even putting one leg in front of the other to take a step.

Deficits in reasoning and problem solving are frequently the result of frontal and temporal lobe damage (Mayer et al., 1986; Sullivan et al., 1989). Functional limitations occur because a person cannot put steps together in a sequence to accomplish a goal or may not be able to choose the items or tools necessary to perform even a simple task such as putting on a robe. Such a deficit makes tasks such as driving a car, paying bills, preparing food, and using the telephone problematic without training in compensatory strategies and environmental modifications.

Executive function comprises the mental capacities required to formulate goals, plan how to achieve them, and carry out the task effectively (Stuss, 1992). A person with impaired executive function has a functional limitation that results in difficulty beginning an activity, monitoring his or her performance during an activity, inhibiting irrelevant information, and maintaining attention. This configuration of cognitive problems makes independent living and productive work a challenge for a person who has sustained an injury and for the rehabilitation professional who needs to help the person and the family learn how to give the cognitive support that will make performance possible.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

Memory plays a very important role in everyday functioning. Different types of memory can be impaired, depending on the location of the brain damage. Deficits in short-term memory, which holds information for further processing, can make new learning difficult. Individuals with memory loss often need rehabilitation to develop strategies to access long-term memory for personal events and general knowledge, to remember future events, and to support the procedures required to perform an activity. Cognitive deficits that impair memory have a profound impact on the performance of people as they recover from physical impairments and move on to try to reestablish independence following injury or illness.

Cognitive Issues: Engineering and Technical Advancements

Few investigators have examined if or how technical devices might be helpful in cases in which and individual is impaired because of the loss of cognitive ability. Nevertheless, it is known that developments in this area will not occur de novo. Positive action needs to be taken to investigate how assistive technical aids may be useful in this area. Action needs to come through the interaction of scientists, clinicians, and engineers. Memory aids and the use of step-by-step instructions are areas tailor-made for providing technical assistance, and engineering may be able to help make significant advances in this area. However, collaboration with families and caregivers, will be necessary for the problems to be understood and for design iterations to be based on realistic clinical experiences.

Future Needs

Cognition plays a critical role in the performance of the tasks of living. When any of these deficits occur (and many of these deficits occur simultaneously), the person is disabled until environmental and compensatory strategies are put in place to support him or her. During the past decade, the emphasis on biomedical science has generated new knowledge about brain plasticity and brain structure-function relationships. As this emphasis expands to include issues of functional limitation and disability, it should be possible to test the application of these findings in clinical interventions to determine how individuals with brain injuries can improve their performance of functional, real-world tasks (e.g., self-care, meal preparation, parenting, and employment).

Most cognitive research has been performed at the impairment level and has involved the administration of experimental and neuropsychological tests. As more clinical studies have been funded, investigators

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

have learned that patterns of behavior in the real-life context differ from those that would have been predicted from neuropsychological tests (Prigatano and Altman, 1990). When a cognitive deficit occurs, the person also experiences changes in emotion, social interaction, and communication; these changes can range from subtle to severe changes and can create complex difficulties for the individual and his or her family, coworkers, and friends.

Rehabilitation strategies to overcome problems presented by aphasia, agnosia, and apraxia require further development and testing and will be understood more fully when scientists and engineers interact with clinicians and patients to understand the impact of these conditions on people's lives.

The research needed to understand the impact of cognition on the individual and society and the potential of environmental and learning strategies on recovery and functioning is yet to be done. It will require research of issues beyond the current biomedical mechanisms that exist today and involve interdisciplinary teams of professionals from fields that span education, philosophy, cognitive psychology, and neuroscience, including neurobiology and neuroradiology. The research must also include rehabilitation professionals such as occupational therapists, speech language pathologists, physicians, and neuropsychologists.

Such teams working together may begin to obtain an understanding of the mechanisms that underlie the recovery and preservation of cognitive functions after brain damage. It will be important to determine if there are aspects of affective disorders that can be distinguished from the cognitive sequelae of acquired brain injury and determine if the brain has different processing pathways for different types of information after brain injury (Buckner et al., 1996). For example, it would be possible to explore whether the cerebellum's contributions to motor learning generalize beyond the purely motor domain and whether the preserved function demonstrated by some people with disabling conditions is mediated by sparing of critical tissue or by compensatory neural pathways. It would be important to know how a deficit in inhibitory control affects everyday function; that is, can different aspects of attentional processing (e.g., divided attention, visual search, and vigilance) predict everyday functioning, including a complex task like driving or work.

Not all disability comes from within the individual. Each person needs a supportive environment to perform at his or her best. A study of cognition prompts investigators to ask new questions. How does cognitive activity relate to specific environmental contexts? What is the role of mediated action in the actual performance of cognitive and functional tasks in people with acquired brain injury and those with no cognitive loss? What role does the environment play in the internal representation and

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

processing of visual information? Also, how is it possible to prepare spouses and families for the multitude of tasks required for life with a person who is severely disabled because of an acquired head injury?

Such questions can only be addressed when there is a level of analysis and method of measurement that allows for the description of cognitive deficits in real-life activities. Functional means of measuring intellect, motivation, mood, judgment, visual perception, auditory perception, motor control, visual attention, vigilance and arousal, working memory, procedural memory, declarative memory, and motion in context must be developed. The challenge of preventing disabilities in those with cognitive loss cannot be left at the level of functional limitation. New means of addressing the cognitive needs of individuals must come to the forefront in science to reduce the devastation of a cognitive impairment on the lives of the people and their families who must live with the consequences of the functional limitations brought on by injury and disease.

Conclusions

Although there is little published research on functional limitations' responsiveness to rehabilitation, this is only partially traceable to the limited funded research in this domain. Functional limitations research requires whole-person studies, which are costly and difficult to perform. Only clinical research that involves the whole person is, by definition, relevant to functional limitations research. Until functional limitations are properly studied, the role of the environment in preventing the physical expression of the person's capacity (i.e., disability) cannot be understood. The process of rehabilitation has heretofore focused on impairment-level interventions, but the economics of rehabilitation, especially in the managed health care sphere, is requiring that people be discharged home as soon as possible. In turn, functional limitations become paramount concerns because they alone prevent the person from returning to the premorbid environment after rehabilitation. Altering the environment to accommodate functional limitations, such as by adding a raised toilet seat following hip replacement or providing durable medical equipment following major amputation or spinal cord injury, are time-honored rehabilitation approaches. The historic reluctance of insurers to pay for such environmental modifications is understandable if one appreciates that society, not the insurer, benefits from improved functional capacity and thus decreased need for "external" support. If the functional capacity of a person, for example, a person with chronic back pain, increases as a result of rehabilitation and the person is able to return to work, society obtains an income tax-paying and less healthcare resource-consuming, member. The insurer benefits directly only inasmuch as the person consumes fewer

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

health care resources. More functional limitations research is urgently needed to determine the optimal role of rehabilitation for individuals with disabling conditions compared with interventions at the societal or environmental level.

Recommendations

Recommendation 5.1 The National Institutes of Health (NIH) should ensure that rehabilitation scientists in general, and functional limitation researchers in particular, are well represented on study sections. NIH also should expand the research capacity of its Institutes to include functional limitations and rehabilitation research as important aspects of their missions.

Recommendation 5.2 A mechanism should be established, possibly through consensus panels, to frame the questions about functional limitations that would help to draw the link between impairments and functional limitations for the purpose of building the science of rehabilitation.

Recommendation 5.3 The Computer Retrieval of Information on Scientific Projects system and other databases used to track research funded by federal agencies should use a government-wide code or coding mechanism to describe rehabilitation research that includes the concepts and definitions of pathology, impairment, functional limitation, and disability presented in this report. This would allow for the more appropriate classification of functional limitations and rehabilitation research.

Recommendation 5.4 A commonly used terminology and taxonomy* should be developed and used that would allow scientists and professionals to communicate more effectively with each other across disciplines. This would include terminology regarding methodologies, measures, the enabling-disabling process, and other descriptors of performance and functional limitations.

Recommendation 5.5 More research is needed to obtain an understanding of the factors that determine the changes in and causal relationships among impairments, functional limitations, and disabilities, and move-

*  

Appendix C contains a preliminary draft of an outline of a taxonomy.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×

ment among these states. Such research should be clearly focused on improving public health from a lifelong perspective.

Recommendation 5.6 More research is needed to improve the understanding of the impact of aging and other lifelong disabling conditions on functional limitations and secondary conditions.

Recommendation 5.7 The science supporting functional limitations depends on integrative studies of the whole person. Behavioral measurement and the development of valid functional limitation measures, should be high priorities in rehabilitation research.

Suggested Citation:"5 FUNCTIONAL LIMITATIONS RESEARCH IN REHABILITATION SCIENCE AND ENGINEERING." Institute of Medicine. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: The National Academies Press. doi: 10.17226/5799.
×
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The most recent high-profile advocate for Americans with disabilities, actor Christopher Reeve, has highlighted for the public the economic and social costs of disability and the importance of rehabilitation. Enabling America is a major analysis of the field of rehabilitation science and engineering. The book explains how to achieve recognition for this evolving field of study, how to set priorities, and how to improve the organization and administration of the numerous federal research programs in this area.

The committee introduces the "enabling-disability process" model, which enhances the concepts of disability and rehabilitation, and reviews what is known and what research priorities are emerging in the areas of:

  • Pathology and impairment, including differences between children and adults.
  • Functional limitations—in a person's ability to eat or walk, for example.
  • Disability as the interaction between a person's pathologies, impairments, and functional limitations and the surrounding physical and social environments.

This landmark volume will be of special interest to anyone involved in rehabilitation science and engineering: federal policymakers, rehabilitation practitioners and administrators, researchers, and advocates for persons with disabilities.

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