Tilt In Space Research Articles

Problematic clinical features of children and adults with cerebral palsy who use electric powered indoor/outdoor wheelchairs: A cross-sectional study

ABSTRACTThis article aims to describe the clinical features of electric powered indoor/outdoor wheelchair (EPIOC) users with cerebral palsy (CP) that are problematic to optimal prescription and to explore comorbidities, features of CP, and conditions secondary to disability impacting on equipment provision for children and adults. The method is a cross-sectional study of EPIOC users (n = 102) with a primary diagnosis of CP. This is a retrospective review of electronic and case note records of EPIOC recipients attending a specialist wheelchair service in 2007–2008. Records were reviewed by a rehabilitation consultant. Data were extracted under three themes; demographic, diagnostic/clinical and wheelchair factors. There were 48 males mean age 27.5 (range 8–70, SD 13.9) years and 54 females, mean age 29.5 (range 7–68, SD 14.6) years with CP. Sixteen comorbidities, nine features of CP, and five features of disability influenced wheelchair prescription. Sixty-four users were provided with specialized seating (SS) and 47 with tilt-in-space (TIS) seats. Complex controls were provided to 16 users, 12 tray-mounted. The majority of users had both SS and TIS. Powered wheelchair prescription has important therapeutic roles in clinical management in addition to enhancing mobility, independence and participation. Clinical features such as spasticity and problematic pain appeared less well managed in adults than in children.

Use of tilt-in-space in seating systems for adults with physical disabilities

Aims: Clinicians increasingly recommend tilt-in-space (TIS) within wheelchair and seating prescriptions to reportedly prevent pressure ulcers; however, it is often unclear what the optimum tilt angle should be. This review aims to determine the use and effectiveness of TIS in seating systems.Methodology: A search of eight electronic databases was completed, namely, Medline, CINAHL, BNI, EMBASE, ASSIA, PubMed, OTDBase, and ISI Web of Science Conference Proceedings; using the keywords TIS, seating, wheelchairs, pressure ulcer, and pressure sores. Databases were searched for articles written in English between 2000 and the end of August 2012. Articles included primary research; TIS as the intervention; and had adult participants.Results: After removal of duplicates and application of inclusion criteria, 12 studies were eligible for this review. Findings show that TIS was used to manage pressure and fatigue, prevent sliding, aid skin perfusion, and facilitate user comfort.Conclusions: Reasons for using TIS will influence the degree of tilt required for the chair occupant; nonetheless, it remains difficult to specify either the optimum degree of tilt or the duration for use in TIS seating systems. In order to build an evidence base, clinicians need to be very explicit on their reasons for prescribing TIS.

Recipients of Electric-Powered Indoor/Outdoor Wheelchairs Provided by a National Health Service: A Cross-Sectional Study

ObjectiveTo describe the characteristics across all ages of powered wheelchair users and the assistive technology prescribed by a regional specialist wheelchair service. DesignCross-sectional study. SettingRegional wheelchair service. ParticipantsElectric-powered indoor/outdoor wheelchair (EPIOC) users (N=544) with 262 boys and men (mean age ± SD, 41.7±20.7y; range, 8–82y) and 282 girls and women (mean age ± SD, 47.2±19.7y; range, 7–92y). InterventionsNot applicable. Main Outcome MeasuresDemographic, clinical/diagnostic details of EPIOC recipients, including pain, (kypho)scoliosis, and ventilators. Technical features, including specialized (adaptive) seating, tilt in space, and modified control systems. Factors were related to age groups: 1 (0–15y), 2 (16–24y), 3 (25–54y), 4 (55–74y), and 5 (≥75y). ResultsNeurologic/neuromuscular conditions predominated (81%) with cerebral palsy (18.9%) and multiple sclerosis (16.4%). Conditions presenting at birth or during childhood constituted 39%. Of the participants, 99 had problematic pain, 83 had (kypho)scoliosis, and 11 used ventilators. Specialized (adaptive) seating was provided to 169 users (31%); most had cerebral palsy or muscular dystrophy. Tilt in space was used by 258 (53%) participants. Younger people were more likely to receive tilt in space than older ones. Only 92 had specialized (adaptive) seating and tilt in space (mean age ± SD, 29±17.8y; range, 8–72y). Of the participants, 52 used modified control systems. ConclusionsThe diversity of EPIOC users across age and diagnostic groups is shown. Their complex interrelations with these technical features of EPIOC prescriptions are explored. Younger users were more complex because of age-related changes. This study provides outcomes of the EPIOC prescription for this heterogeneous group of very severely disabled people.

Why and how we perceive tilt perception in space—an experimental plan during long-term space lifein the international space station—

We are planning an experiment to determine why and how we perceive tilt in space. Tilt perception was thought to disappear in space, where gravity does not exist as a reference for tilt. Nevertheless, astronauts reported perceived head roll-tilt and ocular counter-rolling (OCR) in a centrifuge experiment in space. To explain these unexpected findings, during long-term space life we will measure the subjective visual body axis (SVBA) and OCR at various body roll-tilt angles relative to the inner-cabin vertical, with and without head roll-tilt relative to the body, with and without visual information. We are also currently performing ground-based experiments to collect control data. In this article, we introduce these space and terrestrial experiments.

Modulation of human vestibular-evoked postural responses by alterations in load

The effects of body loading and unloading on human postural responses elicited by 1 mA bilateral, bipolar galvanic vestibular stimulation (GVS) were investigated. Subjects stood symmetrically, and in separate experiments were either loaded by 16, 33 and 50 % of their body weight with weights attached to the trunk, or unloaded by 10, 20 and 30 % using a whole-body harness that partially lifted the body but was free to translate horizontally. Randomised blocks of stimuli for each loading/unloading condition were compared to a non-loaded control condition. The rate of lateral reaction force development over the period 200–350 ms poststimulus increased in both legs with loading and decreased with unloading. The rate of force development was always larger from the leg on the side of cathodal stimulation. Vertical force responses were equal and opposite in the two legs, increasing on the side of the cathode and decreasing on the side of the anode. The rate of vertical force development over the period 200–350 ms after stimulus onset was increased with loading and decreased with unloading. In the frontal plane, the rate of head and trunk tilt in space was increased and decreased with loading and unloading, respectively. However, the relative rate of head tilt with respect to the trunk was not affected by loading conditions. These experiments provide further evidence that load-related afferent feedback influences the processing of vestibular information for the control of balance.

Revolutionary Advances in Adaptive Seating Systems for the Elderly and Persons with Disabilities that Assist Sit-to-Stand Transfers

The independence of elderly and arthritic patients as well as persons with disabilities is influenced considerably by their ability to stand from a chair. The presence of pain, reduced joint range of motion, stiffness, and muscle weakness often limit the ability to achieve a sit-to-stand position (STS). Realizing the enormous implications of STS performance, physicians, scientists, and industry have joined together to design and manufacture a wide variety of adaptive seating systems that facilitate therising process. These systems can be divided into three groups: those without mechanical devices, those with mechanical lifts, and those that can lift, tilt in space, recline, or rock. The design of mechanical seating systems without mechanical assists have been influenced by several factors, including chair height, armrest height, and foot position of the occupant. The evaluation of STS performance involves a variety of measurements to include joint angles and moments, speed of time to rise, functional reach and sway, and perception of patient stability (or perceived safety) in rising from a chair. These studies reported that chair seat height, use of armrest, and foot position had a major influence on the ability to do a STS movement. The use of higher chair seats resulted in lower moments at the knee and hip level. Investigators reported that lowering the chair height increased the need for momentum generation or repositioning of the feet to lower the needed moments. They found that the use of an armrest reduced the moments needed at the hip without altering the range of motion of the joints. These investigators found that repositioning of the feet influenced the strategy of STS movement, allowing lower mean extension moments at the hipwhen the foot position changed from anterior to posterior. Adaptive seating systems with lifts include the spring-booster chair spring-loaded flap seat, and ejector chair. Innovative investigators reported that increased seat height complemented by the mechanical lift enhanced STS transfers by persons with disabilities. The investigators noted that it was easier to perform STS transfer when using a mechanical lift than when rising unassisted or from a raised seat height. The latest adaptive seating system, the elevator chair, has the unique ability to assist the occupant to the STS position. The rear section of this chair remains in a fixed position to support the buttocks of the user during the mechanical lift. The front portion of the seat folds down incrementally as the chair rises to allow the feet of the user to be positioned firmly on the floor. Using an elevator chair, the height that the chair rises will vary with the length of the occupant's legs. When the user reaches a point when his/her legs are comfortably straight and the body is in an erect position, the occupant will walk unassisted from the chair. This elevator chair will soon be available with a tilt-in-space capability as well as a gently rocking motion. The elevator chairs are ideally suited for offices, waiting rooms, hospitals, long-term care facilities, and homes. While persons with disabilities appreciate the benefits of these adaptive seating systems, which allow them to achieve a STS position without assistance, healthcare personnel also value the benefits of these adaptive seating systems because they eliminate their need to lift the occupant to a standing position--an invitation for a potentially serious back injury.

Editorial

To describe the characteristics across all ages of powered wheelchair users and the assistive technology prescribed by a regional specialist wheelchair service.Cross-sectional study.Regional wheelchair service.Electric-powered indoor/outdoor wheelchair (EPIOC) users (N=544) with 262 boys and men (mean age ± SD, 41.7±20.7y; range, 8–82y) and 282 girls and women (mean age ± SD, 47.2±19.7y; range, 7–92y).Not applicable.Demographic, clinical/diagnostic details of EPIOC recipients, including pain, (kypho)scoliosis, and ventilators. Technical features, including specialized (adaptive) seating, tilt in space, and modified control systems. Factors were related to age groups: 1 (0–15y), 2 (16–24y), 3 (25–54y), 4 (55–74y), and 5 (≥75y).Neurologic/neuromuscular conditions predominated (81%) with cerebral palsy (18.9%) and multiple sclerosis (16.4%). Conditions presenting at birth or during childhood constituted 39%. Of the participants, 99 had problematic pain, 83 had (kypho)scoliosis, and 11 used ventilators. Specialized (adaptive) seating was provided to 169 users (31%); most had cerebral palsy or muscular dystrophy. Tilt in space was used by 258 (53%) participants. Younger people were more likely to receive tilt in space than older ones. Only 92 had specialized (adaptive) seating and tilt in space (mean age ± SD, 29±17.8y; range, 8–72y). Of the participants, 52 used modified control systems.The diversity of EPIOC users across age and diagnostic groups is shown. Their complex interrelations with these technical features of EPIOC prescriptions are explored. Younger users were more complex because of age-related changes. This study provides outcomes of the EPIOC prescription for this heterogeneous group of very severely disabled people.

Spatiotemporal response properties of cerebellar Purkinje cells to animal displacement: a population analysis

The hypothesis that corticocerebellar units projecting to vestibulospinal neurons contribute to the spatiotemporal response characteristics of forelimb extensors to animal displacement was tested in decerebrate cats in which the activity of Purkinje cells and unidentified cells located in the cerebellar anterior vermis was recorded during wobble of the whole animal. This stimulus imposed to the animal a tilt of fixed amplitude (5°) 1 This stimulus amplitude was used since, in a previous study, [18]the responses to a roll tilt of a large population of P-cells located in the vermal cortex of the cerebellar anterior lobe showed a linearity in the range of 2–15°. 1 , with a direction moving at a constant angular velocity (56.2°/s), both in the clockwise and counterclockwise directions over the horizontal plane. Eighty-three percent (143/173) of Purkinje cells and 81% (42/52) of unidentified cells responded to clockwise and/or counterclockwise rotations. In particular, 116/143 Purkinje cells (81%) and 32/42 unidentified cells (76%) responded to both clockwise and counterclockwise rotations (bidirectional units), while 27/143 Purkinje cells (19%) and 10/42 unidentified cells (24%) responded to wobble in one direction only (unidirectional units). For the bidirectional units, the direction of maximum sensitivity to tilt ( S max) was identified. Among these units, 24% of the Purkinje cells and 26% of the unidentified cells displayed an equal amplitude of modulation during clockwise and counterclockwise rotations, indicating a cosine-tuned behavior. For this unit type, the temporal phase of the response to a given direction of tilt should remain constant, while the sensitivity would be maximal along the S max direction, declining with the cosine of the angle between S max and the tilt direction. The remaining bidirectional units, i.e. 57% of the Purkinje cells and 50% of the unidentified cells displayed unequal amplitudes of modulation during clockwise and counterclockwise rotations. For these neurons, a non-zero sensitivity along the null direction is expected, with a response phase varying as a function of stimulus direction. As to the unidirectional units, their responses to wobble in one direction predict equal sensitivities along any tilt direction in the horizontal plane and a response phase that changes linearly with the stimulus direction. By comparing these data with those obtained previously during selective stimulation of macular receptors by a 5° off-vertical axis rotation, it appeared that the directions of maximum sensitivity to tilt were distributed over the whole horizontal plane of stimulation, in both conditions. However, co-stimulation of macular and canal receptors during wobble decreased the proportion of unidirectional units, while that of the bidirectional, namely broadly tuned units, increased. In addition, while the average gain of the S max vector of the bidirectional units was comparable, the temporal phase of this vector tended to show a more prominent phase leading behavior during wobble with respect to off-vertical axis rotation. The possibility that the tested neurons formed a population which coded the direction of head tilt in space was also investigated using a modified version of the classical population vector analysis. It was shown that for each selected time in the tilt cycle the direction of the population vector closely corresponded to that of the head tilt, while its amplitude was related to that of the stimulus. We conclude that the broad distribution of the response vector orientation of units located in the cerebellar anterior vermis represents an appropriate substrate for the cerebellar control of vestibulospinal reflexes involving extensor muscles during a variety of head tilts. In view of their efferent projections to the vestibular and fastigial nuclei, the cerebellar anterior vermis may provide a framework for the spatial coding of vestibular inputs, giving equal emphasis to both side-to-side and fore–aft stability.

Responses of Purkinje cells in the cerebellar anterior vermis to off-vertical axis rotation.

Responses of 67 Purkinje cells (P-cells) and 44 unidentified neurons (U-cells) located in the cerebellar anterior vermis were recorded in decerebrate cats during off-vertical axis rotation (OVAR). This stimulus consisted of a slow constant velocity (9.4%/s) rotation in the clockwise (CW) and counterclockwise (CCW) directions around an axis inclined by 5 degrees with respect to the vertical. OVAR imposes on the animal head a 5 degrees tilt, whose direction changes continuously over the horizontal plane, thus eliciting a selective stimulation of macular receptors. A total of 27/67 P-cells (40%) and 24/44 U-cells (55%) responded to both CW and CCW rotations. For these bidirectional units, the direction of maximum sensitivity to tilt (Smax) could be identified. Smax directions were distributed over the whole horizontal plane of stimulation. Among bidirectional neurons, 48% of the P-cells and 33% of the U-cells displayed an equal amplitude of modulation during CW and CCW rotations, indicating a cosine-tuned behaviour. In these instances, the temporal phase of the unit response to a given direction of tilt remained constant, while the sensitivity was maximal along the Smax direction and declined with the cosine of the angle between Smax and the tilt direction. The remaining bidirectional units displayed unequal amplitudes of modulation during CW and CCW rotations. For these neurons, a nonzero sensitivity along the null direction was expected and the response phase varied as a function of stimulus direction. Finally, 31% and 23% of P-cells and U-cells, respectively, responded during OVAR in one direction only (unidirectional units). This behaviour predicts equal sensitivities along any tilt direction in the horizontal plane and a response phase that changes linearly with the stimulus direction. The posibility that the tested neurons formed a population which coded the direction of head tilt in space was also investigated. The data from the whole population of cells were analysed using a modified version of vectorial analysis. This model assumes that for a particular tilt each cell makes vectorial contributions; the vectorial sum of these contributions represent the outcome of the population code and points in the direction of head tilt in space. Thus, a dynamic head tilt along four representative directions was simulated. For each of the four directions, 12 population vectors were calculated at regular time intervals so as to cover an entire cycle of head tilt. The results indicate that for each selected time in the cycle the direction of the population vector closely corresponded to that of the head tilt, while its amplitude was related to the amount of head tilt. These data were particularly obtained for the P-cells. In view of their efferent connections, the cerebellar anterior vermis may provide a framework for the spatial organization of vestibulospinal reflexes induced by stimulation of otolith receptors.