Hsin-Yi Liu

Evaluation of aluminum ultralight rigid wheelchairs versus other ultralight wheelchairs using ANSI/RESNA standards.

Previous studies found that select titanium ultralight rigid wheelchairs (TURWs) had fewer equivalent cycles and less value than select aluminum ultralight folding wheelchairs (AUFWs). The causes of premature failure of TURWs were not clear because the TURWs had different frame material and design than the AUFWs. We tested 12 aluminum ultralight rigid wheelchairs (AURWs) with similar frame designs and dimensions as the TURWs using the American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society of North America and International Organization for Standardization wheelchair standards and hypothesized that the AURWs would be more durable than the TURWs. Across wheelchair models, no significant differences were found in the test results between the AURWs and TURWs, except in their overall length. Tire pressure, tube-wall thickness, and tube manufacturing were proposed to be the factors affecting wheelchair durability through comparison of the failure modes, frames, and components. The frame material did not directly affect the performance of AURWs and TURWs, but proper wheelchair manufacture and design based on mechanical properties are important.

Relationship between wheelchair durability and wheelchair type and years of test

Objective. To investigate the relationship between the durability of wheelchairs according to American National Standard for Wheechairs/Rehabilitation Engineering and Assistive Technology Society of North America (ANSI/RESNA) Wheelchair Standards and wheelchair type as well as year of test. Design. A retrospective study design with a sample of 246 wheelchairs that were tested in accordance with the ANSI/RESNA standards from 1992 to 2008 including four types of wheelchairs: manual wheelchair (MWC), electrical powered wheelchair (EPW), scooters and pushrim-activated power-assisted wheelchair (PAPAW). Unconditional binary logic regression analysis was chosen to evaluate the relationship between test results and test year as well as wheelchair type. Setting. Rehabilitation Engineering Research Center. Main Outcome Measures: Wheelchair durability test result (fatigue test: pass or fail) Results. There was no significant correlation between the year when tested and equivalent cycles. A significant relation was found between test results and wheelchair type (Wald score = 10.845, degree of freedom = 3, p = 0.013) with scooters having a significantly higher pass ratio than MWC (OR = 15.629, 95% CI = 2.026–120.579). EPW also had significantly higher pass ratio than MWC (OR = 1.953, 95% CI = 1.049–3.636). No significant difference on pass ratio was found between PAPAW and MWC. Conclusions. No significant improvements in wheelchair test results during the time frame from 1992 to 2008 were discovered. Wheelchair standard tests should be conducted to assure minimum quality of the wheelchairs and for improving the design of wheelchairs. Although the ANSI/RESNA wheelchair durability test procedures have remained consistent, it does not appear that the introduction of new materials, designs and the availability of test data have improved wheelchair fatigue life.

Seating virtual coach: A smart reminder for power seat function usage

The virtual coach is designed to guide power seat function users to use those functions safely and appropriately. The virtual coach can monitor user compliance with clinician prescriptions, and provide feedback to the user via reminders and alerts. An array of pressure, tilt, and IR sensors provides data to the virtual coach. The results from a user study are presented.

Design and Development of a Lightweight, Durable, Adjustable Composite Backrest Mounting

ABSTRACT Rigid backrest systems for wheelchairs provide a stable and comfortable base of support to help users maintain good posture while propelling and sitting static. Unfortunately, these backrest systems lack the adjustability necessary to allow users to comfortably perform some tasks, such as dressing; consequently, many users retain their sling-style backrests. We developed a lightweight, durable, adjustable composite (LWDAC) backrest mounting system to address these shortcomings and performed engineering and human subjects testing to evaluate the feasibility of the device. The LWDAC prototype passed the static engineering evaluation, as well as nearly all of the fatigue testing prior to failure of the device. Clinicians (n = 9) and users (n = 8) who evaluated the device in a focus group forum had an overall positive response. The participants agreed the backrest mounting can be operated with one hand and felt comfortable when participants were seated. Wheelchair users were interested in purchasing the backrest, and clinicians indicated they would recommend the LDWAC.

Evaluating the usability of a smartphone virtual seating coach application for powered wheelchair users

The aim of the smartphone virtual seating coach (SVSC) was to provide a personalized reminder/warning system to encourage powered wheelchair users to use their powered seating functions (PSFs) as clinically recommended. This study evaluated the usability of the SVSC system by gathering feedback from five powered wheelchair users and five rehabilitation professionals through questionnaires and interviews. The results indicated that clear and understandable instructions to adjust the PSFs are the most important requirement for SVSC application. The instructions must be intuitive, could benefit from animations or indications of PSFs control buttons so powered wheelchair users can adjust their PSFs immediately and appropriately.

Rehabilitation Engineering and Assistive Technology Society of North America’s Position on the Application of Tilt, Recline, and Elevating Legrests for Wheelchairs Literature Update

Official RESNA Position Papers articulate issues in assistive technology and rehabilitation engineering important to researchers, practitioners, policy makers, and funding sources. These positions are based on a strong evidential foundation, supplemented by the authors’ extensive expertise and strengthened by input from others in the field. Development of these position papers follow specific guidelines, which are available on the RESNA website: http://www.resna.org/knowledge-center/position-papers-and-provision-guides.

Spectral Machine Learning for Predicting Power Wheelchair Exercise Compliance

Pressure ulcers are a common and devastating condition faced by users of power wheelchairs. However, proper use of power wheelchair tilt and recline functions can alleviate pressure and reduce the risk of ulcer occurrence. In this work, we show that when using data from a sensor instrumented power wheelchair, we are able to predict with an average accuracy of 92% whether a subject will successfully complete a repositioning exercise when prompted. We present two models of compliance prediction. The first, a spectral Hidden Markov Model, uses fast, optimal optimization techniques to train a sequential classifier. The second, a decision tree using information gain, is computationally efficient and produces an output that is easy for clinicians and wheelchair users to understand. These prediction algorithms will be a key component in an intelligent reminding system that will prompt users to complete a repositioning exercise only in contexts in which the user is most likely to comply.

A Survey of Feedback Modalities for Wheelchair Power Seat Functions

Power seat functions (PSFs) let power wheelchair users adjust their posture independently. The Virtual Seating Coach aims to prompt users to use PSFs appropriately and warn against improper use. The authors surveyed users about their preferences for PSF feedback modalities.

Power seat function usage and wheelchair discomfort for power wheelchair users

Objectives: To investigate correlations between power seat functions (PSFs) usage and wheelchair discomfort. Design: Quasi-experimental design: Time series design. Setting: In-home trial in participants’ home/community. Participants: Thirteen power wheelchair users who independently used power wheelchairs equipped with PSFs as their primary means of mobility. Main Outcome Measures: PSF usage variables include the frequency of performing repositioning and using PSFs (tilt, recline, legrests and seat elevation), wheelchair occupancy, and driving distance. The Tool for Assessing Wheelchair disComfort (TAWC) were used to evaluate general discomfort and discomfort intensity. Results: Spearman correlation coefficient showed that the frequency of using tilt, recline, and legrest is significantly correlated with discomfort intensity. Multiple regression analysis with backward stepwise indicated that these functions can explain 43.8% of the variance (R2 = .438, F(3,33) = 8.588, P < 0.01) in the discomfort intensity score. The best-first decision tree shows that the frequency of using the legrest function was the top node, followed by recline and tilt functions. The overall accuracy of prediction with ten-fold cross validation for discomfort intensity was 79.4%. Conclusions: For people who used power wheelchairs equipped with PSFs, correlation analysis and regression modeling provided evidence from the quantitative data that increasing the frequency of using PSFs may decrease wheelchair discomfort. Future studies should include interventions to encourage people to use their PSFs appropriately.

The clinical trials mosaic: Toward a range of clinical trials designs to optimize evidence-based treatment

Objective: Dichotomizing clinical trials designs into nomothetic (e.g., randomized clinical trials or RCTs) versus idiographic (e.g., N-of-1 or case studies) precludes use of an array of hybrid designs and potential research questions between these extremes. This paper describes unique clinical evidence that can be garnered using idiographic clinical trials (ICTs) to complement RCT data. Proposed and illustrated herein is that innovative combinations of design features from RCTs and ICTs could provide clinicians with far more comprehensive information for testing treatments, conducting pragmatic trials, and making evidence-based clinical decisions. Method: Mixed model trajectory analysis and unified structural equations modeling were coupled with multiple baseline designs in (a) a true N-of-1 pilot study to improve severe autism-related communication deficits and (b) a small sample preliminary study of two complimentary interventions to relieve wheelchair discomfort. Results: Evidence supported certain mechanisms of treatment outcomes and ruled out others. Effect sizes included mean phase differences (i.e., effectiveness), trajectory slopes, and differences in path coefficients between study phases. Conclusions: ICTs can be analyzed with equivalent rigor as, and generate effect sizes comparable to, RCTs for the purpose of developing hybrid designs to augment RCTs for pilot testing innovative treatment, efficacy research on rare diseases or other small populations, quantifying within-person processes, and conducting clinical trials in many situations when RCTs are not feasible.