Geoff R. Fernie

Aging and postural control : A comparison of spontaneous- and induced-sway balance tests

Two different balance testing methods were compared: (1) measurement of spontaneous postural sway during quiet standing, and (2) measurement of induced postural sway in response to an applied postural perturbation. Eyes‐open tests were performed in 64 healthy young and elderly adults and in five elderly subjects with a history of falling. In both balance tests, the sway was defined in terms of the displacement of the center of pressure on the feet. Spontaneous sway was quantified using a number of different amplitude‐ and frequency‐based parameters. Induced sway was measured in response to anterior‐posterior acceleration of a platform on which the subject stood. The induced‐sway test was specially designed to be safe and nonthreatening for elderly subjects; thus, the platform perturbation was confined to small accelerations and a gentle pseudorandom motion was used. To derive a measure of postural stability, the data from this test were fitted with a model that was then used to predict the response to sudden (transient) perturbations, thereby simulating the response in actual falls. Although both induced‐ and spontaneous‐sway measures demonstrated significant aging‐related decreases in stability, the differences were more pronounced for the induced‐sway data. Conversely, some of the spontaneous‐sway measures were much more successful in distinguishing the fallers from the nonfallers. There was a significant correlation between induced‐sway and certain spontaneous‐sway measures in the normal young adults; however, in the elderly normals and fallers, the data from the two types of balance tests either showed no correlation or, for certain spontaneous‐sway measures, tended to show an inverse relationship.

A Posture Control Model and Balance Test for the Prediction of Relative Postural Stability

A balance testing methodology has been developed based on a posture control model which defines relative stability by the degree to which a transient postural perturbation causes the center-of-pressure on the feet to approach the limits of the base-of-support. To minimize anticipatory adaptations and to ensure subject safety, the balance test uses a small-amplitude continuous random or pseudo-random perturbation. The data are used to identify an input-output model, which is then used to predict large-amplitude transient response. Sixtyfour normal subjects were tested, as well as five patients with vestibular lesions and five elderly subjects with a history of falling. Tests were performed with eyes open (EO) and blindfolded (BF), and the EO/BF ratio was calculated. The results showed highly significant differences between young (20-40) and elderly (61-79) normals, but no differences between males and females. In using the balance test to identify the balance-impaired individuals, the BF and EO/BF data provided higher success rates than the EO data. Depending on the modeling method used, the balance test was able to identify up to three of five vestibular patients and five of five elderly fallers, at a false positive rate of 25 percent in the normal subjects.

Urinary Dysfunction in a Geriatric Long-Term Care Population: Prevalence and Patterns*

ABSTRACT: More complete data on the prevalence and types of urinary dysfunction in geriatric institutional patients are essential for the management of their urologic problems. Over a 13‐month period, a prospective study was conducted of all new admissions to a hospital for long‐term care. Eighty percent (277/347) of the newly admitted patients were geriatric (65 or older). Urinary dysfunction was identified in 69.3 percent of the geriatric group; 38.3 percent were incontinent, 20.2 percent bore a urinary diversion device, and 10.8 percent were symptomatic without incontinence. Obtaining reliable information about urologic status posed a significant problem, particularly as 27 percent of the subjects had a mental disorder, including organic brain syndrome or confusion. Thirty percent of all patients questioned were unable to give any history of their own health status. Questioning of both staff and patient to determine reliability of the data revealed that the given information was correct in 77 percent of patients who acknowledged genitourinary dysfunction, and in 83 percent of those who denied it. The study failed to elicit useful data concerning the specificity of symptoms, urologic history, diagnosis and management of urinary dysfunction in this series of geriatric patients under long‐term institutional care.

Impact attenuation of floor coverings in simulated falling accidents

An experimental study was performed to assess to what extent the magnitudes of the impact forces generated in human falling accidents are affected by the nature of the floor covering. Peak decelerations were measured for impacts at the hip and at the hand, using a simple inverted-pendulum anthropomorphic fall simulator. Thirteen different floor coverings were tested, including five hard surfaces and four types of carpet, with and without underpad. It was found that floor coverings can differ significantly in terms of the peak impact force occurring during a fall. For hip impacts, the mean differences between the different floorings ranged up to 23%, with the padded carpets providing the best impact attenuation. In hand impacts, the impact forces were found to be relatively independent of the type of floor covering.

Aging and the Use of Pedestrian Facilities in Winter—The Need for Improved Design and Better Technology

Walking outdoors is often difficult or impossible for many seniors and people with disabilities during winter. We present a novel approach for conducting winter accessibility evaluations of commonly used pedestrian facilities, including sidewalks, street crossings, curb ramps (curb cuts and dropped curbs), outdoor stairs and ramps, building and transit entrances, bus stops, and driveways. A total of 183 individuals, aged 18–85 completed our survey. The results show that cold weather itself had little impact on the frequency of outdoor excursions among middle-aged and older adults while the presence of snow and/or ice on the ground noticeably kept people, especially older adults at home. The survey found that the key elements decreasing winter accessibility were icy sidewalks and puddles at street crossings and curb ramps. While communities have recognized the need to improve snow and ice removal, little attention has been paid to curb ramp design which is especially ineffective in winter when the bottom of the ramps pool with rain, snow, and ice, making it hazardous and inaccessible to nearly all users. We conclude that investigations of alternative designs of curb ramp are needed.

INFLUENCE OF STAIRWAY HANDRAIL HEIGHT ON THE ABILITY TO GENERATE STABILIZING FORCES AND MOMENTS

An experimental study was performed investigating the influence of handrail height on the ability of stairway users to generate stabilizing forces and moments, with the aim of improving stairway safety by developing better handrail design standards. The experiments involved measurement of the maximum forces and moments that subjects were able to exert on a handrail while they stood stationary in an upright position. Two age groups were tested: young (20 to 45 years) and elderly (59 years and over), with a total of 35 subjects. All subjects showed a strong linear dependence on handrail height in generating stabilizing forces and moments. Ability to generate forward/backward forces and forward/backward moments increased linearly with increasing handrail height. Ability to generate upward force decreased linearly with increasing handrail height. Based on the results, an optimal design range for handrail height was estimated.

Usability testing of multimodal feedback interface and simulated collision-avoidance power wheelchair for long-term-care home residents with cognitive impairments

Many older adults in long-term-care homes have complex physical and cognitive impairments and have difficulty propelling manual wheelchairs. Power wheelchair use is restricted owing to safety concerns. Power wheelchairs with collision-avoidance features are being developed to enable safe and independent mobility; however, a paucity of information exists on interface features to help users navigate away from obstacles. We developed a system combining an interface with auditory, visual, and haptic feedback and a simulated collision-avoidance power wheelchair. This device allowed the investigator to stop movement of the power wheelchair when users approached obstacles and to deliver feedback to help them navigate. Five long-term-care home residents with mild or moderate cognitive impairments evaluated device usability, which included effectiveness, efficiency, and user satisfaction. Each resident used the device for six 1 h sessions. Observations, feedback interviews, and outcome questionnaires were completed during and after the sessions. We found the device effective in enabling residents to achieve basic driving tasks and self-identified indoor mobility goals. Furthermore, residents perceived workload to be low and were satisfied with the device. Residents also felt that the feedback was useful to help them navigate away from obstacles.

The impact of new lifting technology in long term care: a pilot study.

1. The researchers conducted a pilot study to test a new lifting system developed with the assistance of nurses. 2. The lift system consists of a portable battery operated power unit that the nurse carries to the bedside and attaches to an overhead track; the ability to share the portable power unit among several track locations is economical. 3. The new lifting system was found to reduce the number of staff necessary to execute patient lifts. This staff saving amounted to 50% of one full time equivalent person per nursing unit. 4. Nurses perceived that less effort was required using the new lifting system compared to a conventional floor model wheeled lifting device.

Shape sensing for computer aided below-knee prosthetic socket design

Shape sensing is useful in the computer aided prosthetic fitting process for two purposes. 1. To input characteristic prosthetic shapes that have been developed over the years through the experience of prosthetists. 2. To provide an accurate and rapid measurement of the anatomical shape of the stump. This paper describes two instruments which have been built to meet these objectives.

Utilization of ultrasound sensors for anti-collision systems of powered wheelchairs

Anti-collision systems have been developed for use with powered wheelchairs in order to enable people with cognitive or physical impairments to safely operate a powered wheelchair. Anti-collision systems consist of sensors that have the ability to detect objects near the wheelchair and a computer that can stop the chair if a collision is determined to be likely. This investigation considered the suitability of using ultrasound sensors in such a system when encountering objects typically found within a home or a long-term care facility. An ultrasound sensors ability to detect an object was dependent on the objects size, shape, specularity, reflectivity, and sound absorption characteristics. Ultrasound sensors, by themselves, were found to be unsuitable for anti-collision systems due to an inability to detect objects commonly encountered in the target environment (the home or long-term care facility) without increasing the complexity of the system to such a degree that it would be prohibitive to deploy this technology to the public.