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Rehabilitation Engineering and Applied Research Lab (REAR Lab)

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Now showing 1 - 10 of 10
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    Biomechanical responses to seated full body tilt and their relationship to clinical application
    (Georgia Institute of Technology, 2009-08-19) Sonenblum, Sharon Eve
    The overall goal of this research is to improve the use of seated tilt to increase function, health and quality of life for people using power wheelchairs. Specifically, the objective of this dissertation is to evaluate the biomechanical responses to seated full body tilt and their relationships to the actual use of tilt-in-space wheelchairs. In the first phase of this study, researchers remotely monitored how 45 fulltime power wheelchair users used their tilt-in-space systems. Participants spent an average of 12.1 hours in their wheelchair each day. They spent more than 2 hours seated at positions greater than 15° and performed tilts of 5° or greater every 27 minutes, but rarely performed tilts past 30°. Two distinct types of tilt behavior were identified: uni-modal (staying at a single position more than 80% of the time) and multi-modal (staying at a single position less than 80% of the time). Participants in the multi-modal group tilted significantly more frequently (4 times per hour) than the uni-modal group, and did not have a single typical position. Participants without sensation were more likely to exhibit uni-modal behavior. In the second phase of this study, researchers used interface pressure measurements and laser Doppler flowmetry to study changes in localized loading and superficial blood flow at the ischial tuberosities across different amounts of tilt. Eleven participants with spinal cord injuries were studied in a laboratory setting. Results showed that biomechanical responses to tilt were highly variable. Pressure reduction at the ischial tuberosity was not present at 15°, but did occur with tilts to 30° and greater, and could be explained by the tilt position and upright pressure. Unlike pressure, blood flow increased with all tilts from an upright position, but did not increase when tilting from 15° to 30°. Only 4 of 11 participants had a considerable increase (≥10%) in blood flow at 30° tilt, whereas 9 participants did during maximum tilt (i.e., 45°-60°). Based on the results of this study, tilting for pressure reliefs as far as the seating system permits is recommended to maximize the potential for significant blood flow increases and pressure relief.
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    The Effect of Model Design, Cushion Construction, and Thin Pressure Mats on Pressure Measurement
    (Georgia Institute of Technology, 2007-04-11) Pipkin, Leigh
    Wheelchair cushions are designed to protect skin by reducing and distributing pressure. Pressure sensors and buttock models are used in standardized testing of wheelchair cushions. The purpose of this study was to explore how the presence of a thin pressure measurement mat, cushion construction, and buttock model design affect interface pressure (IP), envelopment, and immersion. Aspects reported here are the effect of model design on IP and envelopment and the interaction between model design and cushion construction. Testing was performed with two indenters and seven cushions. Conclusion: Wheelchair cushions deform in response to a loaded indenter. The result is a change in the shape of the indenter-cushion interface, which may not be consistent across loading trials. This is influenced by cushion stiffness and the unloaded shape of the cushion. The data suggests that model design influences the pressure redistribution properties of cushions. Therefore, development of standardized tests should consider the interaction between models and cushions.
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    Tweel (TM) technology tires for wheelchairs and instrumentation for measuring everyday wheeled mobility
    (Georgia Institute of Technology, 2007-04-04) Meruani, Azeem
    This thesis is focused on two aspects related to wheeled mobility: 1) Evaluating the impact of a new tire design on powered mobility, and 2) Instrumentation that permits better monitoring and assessment of wheeled mobility in everyday use. The Tweel technology tires developed by Michelin USA are comprised of an outer polyurethane ring supported by polyurethane fins instead of metal spokes, which allow the tire to deflect under pressure. As a wheelchair tire they offer a potential breakthrough as they have deflection properties similar to a pneumatic tire while maintaining the low maintenance of a solid foam-core tire. A study was conducted to compare the Tweel technology tires to standard solid foam-core tires for vibration transmission, traction and overall life span. The Tweel technology tires failed produce any significant difference in vibration transmitted to the user compared to solid foam-core tires. Additionally, the Tweel technology tires showed significant signs of deterioration after a month long field trial, thus indicating a short life span. However, Tweel technology tires provided better traction on both dry and wet concrete. Overall, Tweel technology tires have to be re-engineered to provide better damping properties, leading to lower vibrational levels transmitted to the user. The second section this thesis addressed the need to develop a methodology of measuring mobility in everyday usage. This section is part of a greater ongoing research project at CATEA (Center for Assistive Technology and Environmental Access) aimed at understanding everyday wheelchair usage. Methodology was developed to measure bouts of mobility that characterize wheelchair usage; which includes the number of starts, stops, turns and distance traveled through the day. Three different technologies which included, Accelerometer unit on the rim of the drive wheel, Gyro-Accelerometer unit on the frame of the chair and Reed switches, were tested. Testing included various criteria for accuracy, durability and compatibility for measuring bouts of everyday wheeled mobility. Although a single technology could not be used to measure all aspects of mobility, the Accelerometer unit on the rim met the design criteria for measuring starts stops and distance, while the Gyro-Accelerometer unit met the requirements for measuring turns.
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    Assessing the Efficacy, Effectiveness, and Cost-Effectiveness of Assistive Technology Interventions for Enhancing Mobility
    (Georgia Institute of Technology, 2007) Fuhrer, Marcus J.
    PURPOSE: The aim of this paper is to highlight the contributions that complementary efficacy, effectiveness, and cost-effectiveness studies can make to assessing the outcomes of assistive technology interventions for enhancing mobility. METHOD: The terms, 'assistive technology outcomes research' and 'assistive technology interventions', are defined. Several bases are examined for the shortage of outcomes research pertaining to mobility-related assistive technology interventions. Three presuppositions are described for the research strategy of interlocking studies being recommended. They are assigning priority to evaluating both recently developed assistive technologies and ones that have long been available, acknowledging the complexity of assistive technology as an intervention, and appreciating the trade-offs necessary for strengthening studies' internal and external validity. Some key study preparations are considered, including treatment theory, treatment specification, and the selection of outcome domains and measures. The essential features of efficacy, effectiveness, and cost-effectiveness studies are outlined, and their interdependence is stressed. RESULTS AND CONCLUSIONS: To assess the outcomes of assistive technology interventions for mobility in ways that are both methodologically sound and relevant to stakeholder needs, a research strategy is required involving mutually reinforcing efficacy, effectiveness, and cost-effectiveness studies. Collaborative arrangements and funding methods are discussed for fostering the needed research.
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    Clinical Application of Pressure Mapping
    (Georgia Institute of Technology, 2007) Sprigle, Stephen ; Davis, Kim
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    Methodology to Measure the Adjustability of Skin Protection Features of Wheelchair Cushions
    (Georgia Institute of Technology, 2007) Linden, Maureen ; Sprigle, Stephen
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    Research Priorities: Seating and Positioning
    (Georgia Institute of Technology, 2007) Sprigle, Stephen
    The Wheeled Mobility State of the Science Conference, hosted by the mobilityRERC at the Georgia Institute of Technology, was a forum to identify and discuss important research topics. The Conference was configured around Breakout Groups which were assigned specific research topics. These topics were selected via dot-voting by Conference attendees. The charge to the Breakout Groups was simple, yet unattainable: “Configure your research topic into a research project”. They were provided with general guidelines to identify research questions, specific aims or hypotheses, significance, study design possibilities, recruitment considerations, measurement variables and tools, analysis considerations, and anticipated challenges. This article summarizes the discussions from the Seating and Positioning Breakout Groups. The four research topics selected for discussion were: Impact of a seating and mobility intervention, Defining a systematic clinical approach to cushion selection, Functional impact of wheelchair cushions, and Long term impact of sitting. One member of each Group documented the discussion and a summary presentation was made to all Conference attendees. The following synopses were compiled from the Group notes and presentation. They are presented in sequence and reflect variability in discussion, presentation and content. Some research topics were more amenable to the suggested guidelines than others.
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    Acoustic Imaging of Bruises
    (Georgia Institute of Technology, 2006-05-22) Prabhakara, Sandeep
    Ultrasound is a valuable tool to monitor wound healing. In this report, ultrasound is used to determine the features in the B-scans that correspond to a bruise. High frequency ultrasound scans show clear and distinct features that correspond to a laceration or a late stage pressure ulcer. This is because of the extensive damage and the rupture of the epidermis in both the cases. This study assumes significance because it is an effort to find such artifacts in the ultrasound scans of bruises caused by blunt forces where the epidermis remains intact. In this study, the structure of the skin was visualized using a 20 MHz ultrasound scanner. Skin thickness and echogenicity changes may result due to blood extravasations or edema. The thickness and the echogenicity values are plotted against time to determine the trend in the variation of these parameters. We see an intraday and a daily fluctuation of skin thickness and echogenicity albeit with no distinct trend on a day to day basis or between subjects. The results also give us a good estimation of the variation observable in these parameters in the event of an injury. A snapshot analysis is also performed, which describes qualitatively the structural changes in the B-scan of the bruise site compared to the control site. There are six different types of qualitative changes which can appear in the B-scan of a bruised site compared to the control. In the event of an injury, usually, more than one of these changes is manifested in the scan of a bruise. Skin thickness and echogenicity vary considerably due to a number of physiological factors which can seldom be controlled. Therefore, these parameters can give conclusive evidence of a bruise only if the change between a bruised region and a control region is much greater than the daily, normal variations. Snapshot analysis can help detect a bruise or a deep tissue injury. Further work involves the application of pattern recognition or face recognition algorithms to automate the detection.
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    Design of Wheelchair Seating Systems for Users with High-Tone Extensor Thrust
    (Georgia Institute of Technology, 2006-05-22) Kitchen, James Patrick
    High-tone extensor thrust is common to those with cerebral palsy and those suffering spinal cord injuries. It is a muscle-control phenomenon that causes the body to straighten spastically. One goal of this thesis is to design a dynamic seating system that moves with respect to the wheelchair frame, allowing the seat to move with the user during an extensor thrust and reduce forces. One unique challenge is that the seat needs to remain rigid during normal functional activities and only become dynamic when an involuntary thrust is detected. A second goal of this thesis is to design a control scheme that is able to differentiate between these two types of motion. These design goals are initially investigated with a hinged-seatback system, instrumented with sensors to allow for the detection of thrusts and to actively control seating components. A full seating system is then built to allow for full-body extensor thrusts, involving the seatback, seat bottom, and leg rest of the wheelchair. This system is analyzed for effectiveness of reducing forces on the body during an extensor thrust. Another serious problem for this segment of the population is pressure ulcers. These are caused by prolonged pressure on the skin from weight-bearing bony prominences. Various seating system configurations are known to help with pressure relief. The three standard configurations for a chair are tilt, recline, and standing. The final goal of this thesis is to measure and compare the effectiveness of these three methods for their ability to relieve pressure on the seat bottom. To accomplish this, a powered wheelchair with built-in capabilities for recline and standing is mounted to a tilting mechanism. Test subjects are used to experimentally compare the effectiveness of each method for pressure reduction using pressure mats on all weight-bearing surfaces. A 2D model is also developed and validated with the experimental results.
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    Development of a Concept Wheelchair for the Elderly
    (Georgia Institute of Technology, 2006-04-12) Cope, Clinton D.
    This thesis describes the research, design, and development of a mid-drive wheelchair for use by the elders living independently, in assisted living facilities, and in nursing homes created by a design team at Georgia Tech's Center for Assistive Technology and Environmental Access (CATEA). This wheelchair stands to significantly improve the mobility of elders through better drive wheel placement and design features that could stand to improve their quality of life.