Barbara A. Crane

Development of a consumer-driven Wheelchair Seating Discomfort Assessment Tool (WcS-DAT)

This study examined the concept of seating discomfort in a population of full-time wheelchair users with intact sensation. The goal was to construct a tool that would quantify seating discomfort experienced by wheelchair users. Ten participants were interviewed using ethnographic interview techniques. Data were analyzed using a cross-classifying matrix to examine commonalities among the 10 participants’ responses. There were 16 discomfort and 13 comfort descriptors used by the participants. Of these, eight discomfort and five comfort descriptors were selected to include in the Wheelchair Seating Discomfort Assessment Tool (WcS-DAT). The discomfort descriptors selected were: aches and pains, need to move, pressure points, feeling poorly positioned, unable to concentrate, instability, not comfortable, and feeling too hot, cold or damp. The comfort descriptors selected were: absence of discomfort, feeling good, having no pain, able to concentrate, and feeling stable. The WcS-DAT also includes general information, such as the amount of time spent sitting and whether the individual was transferred into the chair properly—factors thought to affect discomfort—and ratings of discomfort intensity—in general and differentiated by body area. The WcS-DAT is a comprehensive tool for quantification of wheelchair seat discomfort for this population.

Test-retest reliability, internal item consistency, and concurrent validity of the wheelchair seating discomfort assessment tool.

Discomfort is a common problem for wheelchair users. Few researchers have investigated discomfort among wheelchair users or potential solutions for this problem. One of the impediments to quantitative research on wheelchair seating discomfort has been the lack of a reliable method for quantifying seat discomfort. The purpose of this study was to establish the test-retest reliability, internal item consistency, and concurrent validity of a newly developed Wheelchair Seating Discomfort Assessment Tool (WcS-DAT). Thirty full-time, active wheelchair users with intact sensation were asked to use this and other tools in order to rate their levels of discomfort in a test-retest reliability study format. Data from these measures were analyzed in SPSS using an intraclass correlation coefficient (ICC) model (2,k) to measure the test-retest reliability. Cronbachs α was used to examine the internal consistency of the items within the WcS-DAT. Concurrent validity with similar measures was analyzed using Pearson product-moment correlations. ICC scores for all analyses were above the established lower bound of .80, indicating a highly stable and reliable tool. In addition, alpha scores indicated good consistency of all items without redundancy. Finally, correlations with similar tools, such as the Chair Evaluation Checklist and the Short Form of the McGill Pain Questionnaire, were significant at the .05 level, and many were significant at the .001 level. These results support the use of the WcS-DAT as a reliable and stable tool for quantifying wheelchair seating discomfort. Its application will enhance the ability to assess and to research this important problem and will provide a means to validate the outcomes of specialized seating interventions for the study population of wheelchairs users.

A dynamic seating intervention for wheelchair seating discomfort

Crane BA, Holm MB, Hobson D, Cooper RA, Reed MP: A dynamic seating intervention for wheelchair seating discomfort. Am J Phys Med Rehabil 2007;86:988–993. Objective:The objective of this study was to examine the effectiveness of a new user-adjustable wheelchair seating system designed to relieve discomfort for long-duration wheelchair users. Design:This objective was carried out using the newly developed Tool for Assessing Wheelchair disComfort (TAWC) as the primary outcome measure. Two wheelchair users each tested two different designs and feedback from the wheelchair users regarding the first design was used to guide development of the second design. A single-subject research methodology was used, allowing long-duration (up to 2 wks per test) evaluation of the wheelchair seating systems and comparison of subject discomfort levels with those experienced during a baseline period using their own wheelchairs. The experimental wheelchair seating systems employed existing automotive seating with embedded pneumatic bladders that allowed adjustment of the seat and back-support characteristics. The test wheelchair also had tilt, recline, and elevating leg rests. Results:The two subjects completed limited periods of testing with the first design, both finding poor results with either stable or increased levels of discomfort. Subject feedback was used to redesign the wheelchair seat. After redesign, both subjects tested the second design and found it substantially more comfortable. Conclusions:The selected research methodology was a very positive method for a progressive wheelchair seating design and the second design provided improved comfort for both users when compared with that experienced using their own wheelchairs and the first test wheelchair. Future research of this type of user-controlled technology is recommended.

Comparison of Muscle and Skin Perfusion Over the Ischial Tuberosities in Response to Wheelchair Tilt-in-Space and Recline Angles in People With Spinal Cord Injury

OBJECTIVE To compare the efficacy of wheelchair tilt-in-space and recline on enhancing muscle and skin perfusion over the ischial tuberosities in people with spinal cord injury (SCI). DESIGN Repeated-measures and before-after trial design. SETTING University research laboratory. PARTICIPANTS Power wheelchair users with SCI (N=20). INTERVENTIONS Six combinations of wheelchair tilt-in-space and recline angles were presented to participants in a random order. The testing protocol consisted of a baseline 5 minutes sitting with no tilt/recline and 5 minutes positioned in a tilted and reclined position at each of 6 conditions, including: (1) 15° tilt-in-space and 100° recline, (2) 25° tilt-in-space and 100° recline, (3) 35° tilt-in-space and 100° recline, (4) 15° tilt-in-space and 120° recline, (5) 25° tilt-in-space and 120° recline, and (6) 35° tilt-in-space and 120° recline. MAIN OUTCOME MEASURES Muscle and skin perfusion were assessed by near-infrared spectroscopy and laser Doppler flowmetry, respectively. RESULTS Muscle perfusion was significantly increased at 25° and 35° tilt-in-space when combined with 120° recline, and skin perfusion was significantly increased at 3 tilt-in-space angles (15°, 25°, 35°) when combined with 120° recline and at 35° tilt-in-space when combined with 100° recline (P<.05). Even in the positions of increased muscle perfusion and skin perfusion (25° and 35° of tilt-in-space combined with 120° of recline), the amount of muscle perfusion change was significantly lower than the amount of skin perfusion change (P<.05). CONCLUSIONS Our results indicate that a larger angle of tilt-in-space and recline is needed to improve muscle perfusion compared with skin perfusion. A position of 25° tilt-in-space combined with 120° recline is effective in enhancing muscle and skin perfusion of weight-bearing soft tissues at the ischial tuberosities.

Wheelchair Seating: A State of the Science Report

Regardless of the field, agenda-setting processes are integral to establishing research and development priorities. Beginning in 1998, the National Institute on Disability and Rehabilitation Research mandated that each newly funded Rehabilitation Engineering and Research Center (RERC) hold a state-of-the-science consensus forum during the third year of its 5-year funding cycle. NIDRRs aim in formalizing this agenda-setting process was to facilitate the formulation of future research and development priorities for each respective RERC. In February 2001, the RERC on Wheeled Mobility, University of Pittsburgh, conducted one of the first such forums. The scope encompassed both current scientific knowledge and clinical issues. In preparation, expert interviews were carried out to establish the focus for the forum. Because a stakeholder forum on wheelchair technology had recently been held, opinion favored wheelchair seating as the focus and included the following core areas: seating for use in wheelchair transportation, seated postural control, seating discomfort, and tissue integrity management. The aim of this report is to present a summary of the workshop outcomes, describe the process, and increase awareness of this agenda-setting process in order to enhance future participation in a process that critically influences the field of wheeled mobility.

Wheelchair tilt-in-space and recline does not reduce sacral skin perfusion as changing from the upright to the tilted and reclined position in people with spinal cord injury.

OBJECTIVE To investigate the effect of various wheelchair tilt-in-space and recline angles on sacral skin perfusion in wheelchair users with spinal cord injury. DESIGN Repeated-measures, intervention and outcomes measure design. SETTING University research laboratory. PARTICIPANTS Power wheelchair users with spinal cord injury (N=11). INTERVENTIONS Six protocols of various wheelchair tilt-in-space and recline angles were randomly assigned to the participants: (1) 15° tilt-in-space and 100° recline, (2) 25° tilt-in-space and 100° recline, (3) 35° tilt-in-space and 100° recline, (4) 15° tilt-in-space and 120° recline, (5) 25° tilt-in-space and 120° recline, and (6) 35° tilt-in-space and 120° recline. Each protocol consisted of a 5-minute upright sitting and a 5-minute tilted and reclined period. MAIN OUTCOME MEASURES Skin perfusion over the sacrum (midpoint between the right posterior superior iliac spine and the adjacent spinous process) and right ischial tuberosity was measured using laser Doppler flowmetry. RESULTS Sacral skin perfusion did not show a significant difference in all 6 protocols of various tilt-in-space and recline angles when changing from an upright to a tilted and reclined position (not significant). However, as previously reported, skin perfusion over the ischial tuberosity showed a significant increase at 15°, 25°, and 35° tilt-in-space when combined with 120° recline and at 35° tilt-in-space when combined with 100° recline (P<.008). CONCLUSIONS Our results indicate that wheelchair tilt-in-space and recline enhances skin perfusion over the ischial tuberosities without reducing sacral skin perfusion when changing from an upright to a tilted and reclined position.

Responsiveness of the TAWC tool for assessing wheelchair discomfort

Purpose. The purpose of this research was to determine the clinical usefulness of the Tool for Assessing Wheelchair disComfort (TAWC) by examining floor and ceiling effects and responsiveness when used with two groups of wheelchair users – one known to have experienced real changes in discomfort levels and the other with unchanged levels. Method. In a retrospective analysis of data from two previous studies, change scores were compared across two groups of subjects – one stable group (NON-CHANGERS) and one experiencing a seating intervention (CHANGERS) intended to decreased seating discomfort. Results. No significant floor or ceiling effects were found. The average General Discomfort Score (GDS) change among the NON-CHANGERS was 2.0 (with a possible score range of 13 – 91) and average Discomfort Intensity Score (DIS) change was 1.8 (with a possible score range of 8 – 99) for the same group. Conversely, average GDS change among the CHANGERS was 8.7 and the average DIS change was 7.7. Additionally, both scores demonstrated a moderate effect size (d) for two tested treatments (GDS = 0.53 and 0.50, DIS = 0.31 and 0.33) and the standardized response means were 0.78 and 0.77 for the GDS and 0.80 and 1.2 for the DIS. Conclusions. All analyses indicate good responsiveness of the TAWC, supporting its use clinically and in future research.

Investigation of peak pressure index parameters for people with spinal cord injury using wheelchair tilt-in-space and recline: methodology and preliminary report.

The purpose of this study was to determine the effect of the sensel windows location and size when calculating the peak pressure index (PPI) of pressure mapping with varying degrees of wheelchair tilt-in-space (tilt) and recline in people with spinal cord injury (SCI). Thirteen power wheelchair users were recruited into this study. Six combinations of wheelchair tilt (15°, 25°, and 35°) and recline (10° and 30°) were used by the participants in random order. Displacements of peak pressure and center of pressure were extracted from the left side of the mapping system. Normalized PPI was computed for three sensel window dimensions (3 sensels × 3 sensels, 5 × 5, and 7 × 7). At least 3.33 cm of Euclidean displacement of peak pressures was observed in the tilt and recline. For every tilt angle, peak pressure displacement was not significantly different between 10° and 30° recline, while center of pressure displacement was significantly different (P < .05). For each recline angle, peak pressure displacement was not significantly different between pairs of 15°, 25°, and 35° tilt, while center of pressure displacement was significantly different between 15° versus 35° and 25° versus 35°. Our study showed that peak pressure displacement occurs in response to wheelchair tilt and recline, suggesting that the selected sensel window locations used to calculate PPI should be adjusted during changes in wheelchair configuration.

Intrarater and Interrater Reliability of 22 Clinical Measures Associated With Lower Quarter Malalignment

OBJECTIVE The purpose of this study was to assess the intrarater and interrater reliability of a broad range of techniques commonly used to assess the lower quarter. METHODS A test-retest single group design was used to investigate the intrarater and interrater reliability of 22 lower quarter evaluation measures. Two raters conducted each measure twice on a total of 18 unimpaired subjects with an average age of 23.7 years. This study was conducted in the Human Performance Research laboratory in a university setting. Intraclass correlation coefficients were used to assess reliability of continuous variables, and weighted kappa was used to assess nominal or ordinal results. RESULTS Side differences were not found (P > .05); thus, data for right and left legs were pooled (n = 36) where applicable. Intraclass correlation coefficient and weighted kappa results ranged from a low of 0.06 to a high of 0.99. Intrarater reliability results were generally higher than interrater reliability results. CONCLUSION Many of the clinical measures demonstrated good overall reliability. For those tests where acceptable intrarater and interrater reliability cannot be demonstrated, additional training of raters, modification of the technique, or elimination of the techniques use should be considered.

Prevalence of Sensor Saturation in Wheelchair Seat Interface Pressure Mapping

Pressure mapping is a frequently used tool with great power to provide information about the forces between a patient and a wheelchair seat. One widely recognized limitation to this paradigm is the possibility of data loss due to sensor saturation. In this study, we seek to quantify and describe the saturation observed in the measurement of interface pressures of wheelchair users. We recorded approximately two minutes of interface pressure data from 22 elderly wheelchair users (11M/11F, 80 ± 10 years) and found that 4.7% of data frames had 1 saturated sensor, and 9.0% had more than one saturated sensor, for a total of 13.7% of all frames of data. Data from three of the 22 subjects (13.6%) were substantially affected by the persistent presence of saturated sensors. We conclude that for this population of elderly wheelchair users, sensor saturation may be a concern and should be factored properly into study design a priori.