Wheelchair in-seat monitoring design considerations

Wheelchair in-seat activity trackers are developed to monitor and provide feedback about the pressure redistributing movements of wheelchair users, including weight shifts and other postural shifts that redistribute buttocks pressures. From a design perspective, in-seat activity trackers reflect myriad design decisions that impact performance, function, and usability. Many, if not all, of these decisions involve interconnections across system components, and can have significant impact on tracker operation and user-experience. Technology developers will have to manage many benefits and trade-offs that accompany design of each subsystem. Two documents were created based upon real-world use of in-seat trackers to briefly identify design criteria and constraints that should be considered.U.S. Army Medical Research and Materiel Command Spinal Cord Injury Research Program, Translational Research Award W81XWH-17-1-022

Measuring Activity and Participation in Outcomes Research

Presented at the RESNA Annual Meeting. 2006. Atlanta, GA

Monitoring Power Upright and Tilt-In-Space Wheelchair Use

Presented at the RESNA Annual Meeting. 2006. Atlanta, GA.This study examines the use of power upright and power tilt-in-space (TIS) wheelchairs. An occupancy detector, wheel revolution counter, and position sensor comprise the Wheelchair Activity Monitoring Instrument as used in this study. On average, subjects sat in their wheelchairs for 10 hours per day, spent 50 (±24) minutes wheeling with an average daily distance traveled of 0.84 miles. The majority of mobility bouts were less than 30 seconds and shorter than 25 feet. Subjects with TIS used their tilt feature (at least a 15° change in position) 16±10 times and spent between 0 and 108 minutes at a fully tilted (>40°) position daily.occupancy detector, wheel revolution counter, and position sensor comprise the Wheelchair Activity Monitoring Instrument as used in this study. On average, subjects sat in their wheelchairs for 10 hours per day, spent 50 (±24) minutes wheeling with an average daily distance traveled of 0.84 miles. The majority of mobility bouts were less than 30 seconds and shorter than 25 feet. Subjects with TIS used their tilt feature (at least a 15° change in position) 16±10 times and spent between 0 and 108 minutes at a fully tilted (>40°) position daily

A Case Study Comparing Activity and Participation Measurement in Two Subjects

Presented at the RESNA Annual Meeting. 2007. Phoenix, AZ.This case study compares the differences between complementary methodologies that measure activity and participation in two subjects who use wheeled mobility devices. Data collection consisted of 1) a self-report participation measure for people with mobility disabilities - the Community Participation and Perceived Receptivity Survey (CPPRS) - and 2) a passive instrumentation data-gathering methodology that includes a global positioning system (GPS) data logger, followed by a prompted recall interview (PRI) to confirm GPS data location and query activity purpose. Many of the destination types (e.g., grocery stores) named in the CPPRS were confirmed by GPS/PRI data. Issues affecting subject responses in both methods included ambiguous categories and researcher assumptions about the nature of activity. Differences between self-report and instrumentation data are discussed as they impact understanding activity and community participation among wheeled mobility users and the development of self-report participation instruments

Characterization of Power Wheelchair Use in the Home and Community

Published in the Archives of Physical Medicine and Rehabilitation, 89(3), 486-491. doi:10.1016/j.apmr.2007.09.029Objective: To characterize the use of power wheelchairs and to determine if multiple measures of mobility and occupancy jointly provide a more comprehensive picture of wheelchair usage and daily activity in full-time power wheelchair users than daily distance alone. Design: Prospective observational study. Setting: Subjects’ everyday mobility was measured in their homes and communities for two weeks and prompted recall interviews were conducted by phone. Participants: A convenience sample of 25 non-ambulatory, full-time power wheelchair users. Interventions: Not applicable. Main Outcome Measures: Wheelchair usage was logged electronically and GPS / interview data were used to isolate chair use to home, indoors but not at home and outdoor environments. Distance wheeled, time spent wheeling, number of bouts, time spent in the wheelchair and the percent of time in the wheelchair spent wheeling were measured to describe wheelchair use. Results: The median wheelchair user spent 10.6 hours (5.0-16.6) in his/her wheelchair daily and wheeled 1.085 km (0.238-10.585) over 58 minutes (16-173) and 110 bouts (36-282). Wheelchair use varied across subjects, within subjects from day-to-day, and between environments. Mobility bouts outdoors were longer and faster than those wheeled indoors. In a regression analysis, distance wheeled explained only 33% of the variation in the number of bouts and 75% in the time spent wheeling. Conclusions: Power wheelchair use varies widely both within and between individuals. Measuring distance, time and number of bouts provides a clearer picture of mobility patterns than measuring distance alone, while occupancy helps to measure wheelchair function in daily activities

Biomechanical responses to seated full body tilt and their relationship to clinical application

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.Ph.D.Committee Chair: Sprigle, Stephen; Committee Member: Brani Vidakovic; Committee Member: Charlie Lachenbruch; Committee Member: John L. Lin; Committee Member: Rudy Gleaso

Why Full-time Power Wheelchair Users Tilt

Presented at the Rehabilitation Engineering and Assistive Technology Society of North America (RESNA) Annual Conference, 2008, Arlington, VA