Reliability assessment of power wheelchairs

To develop and assess new reliability performance measures for wheelchair devices using reliability engineering methods and compare them across wheelchair models.

This retrospective study analyzes wheelchair repair data from n = 1092 power wheelchairs prescribed by the National Health Service (NHS) through the West of Scotland Mobility and Rehabilitation Centre (WestMARC) between December 2007 and October 2013 in Greater Glasgow, Scotland, UK. This dataset was received by The Ohio State University in 2022, and repairable systems reliability analysis was performed.

Not applicable.

Reliability performance measures derived from the reliability engineering modeling of the mean cumulative number of repairs included Repair Trend, Mean Time Between Failures (MTBF), and a Wheelchair Reliability Index (WRI). It was hypothesized that there are no differences in the repair distributions between standard and complex wheelchair seating models in the dataset, and repair distributions of models stratified by age into two groups: adults and seniors. Additionally, the relationships between recurrent repair events and demographics were tested.Results: Four wheelchair models were analyzed: two standard (S1, S2) and two complex (C1, C2) seating models. Models S2 and C2 demonstrated a linear repair trend, while the other two had an exponential one. Consistent with previous evidence, the complex seating models had significantly different repair distribution and lower reliability compared to standard seating models, p < .05. About 68-80% of units failed among the models and had an MTBF ranging from 4-8 months over five years. Model C1, which is used outdoors actively, is twice as costly but has one-fourth the WRI compared to standard seating models. There is a significant difference among repair distributions of adults and seniors, p < .05. No significant associations were found between recurrent repair events and demographic variables of age and sex.

This is the first study, to the authors' knowledge, that modeled wheelchair field failure data to develop reliability performance measures and compare the reliability of standard and complex seating power wheelchair models. The study found a lower overall MTBF value, indicating that all study wheelchairs demonstrate poor reliability and require condition inspections every 3-6 months. Individuals requiring the highest level of care utilize complex seating wheelchair models and deserve enhanced wheelchair reliability and safety. Our study findings underscore the urgent need for reliability performance monitoring and subsequent improvements in the areas of wheelchair selection, standards, servicing innovation, and provision systems.