Recommendations on Standards for the Design of Medical Diagnostic Equipment for Adults with Disabilities, Advisory Committee Final Report

Introduction

The proposed guidelines for medical diagnostic equipment recommends a minimum transfer surface 30 in. (760mm) wide and 15 in. (381mm) deep. At the request of the U.S. Access Board staff, a brief analysis was performed based on static anthropometry measurements previously collected to evaluate the adequacy of these transfer surface dimensions.

The Center for Inclusive Design and Environmental Access (IDeA) at the University at Buffalo conducted an anthropometric study of 500 individuals who use wheeled mobility devices (WMD)1. The research included the collection of demographic information and WMD characteristics, and the measurement of structural and functional anthropometry. Data collection included 3 dimensional measurements of approximately 90 points located on the body and device. Linear distances between pairs of measured points can be computed to provide dimensional estimates of body and mobility device sizes.

Four static body dimensions considered relevant to the width and depth dimensions of a seating surface were computed and analyzed to serve as a reference. These dimensions include: thigh breadth, shoulder breadth, buttock-popliteal length, and wheelchair seat depth. Dimension values are stratified by gender and mobility device type since significant differences in size and space requirements exist across these sub-groups. All dimensions are based on occupant static postures while seated in their own mobility device. As such, the analysis focuses only on the adequacy of the proposed transfer surface dimensions for a static seating surface. No measurements of transferring to or from the mobility device were recorded. Hence, the dimensions discussed in this report should only be considered as a starting point for accessible design of a seating surface. When determining space requirements for dynamic transfer tasks, there are additional space needs and functional abilities of the user population which must be considered. For example, individuals may need additional space to position their hands when conducting a side transfer. Issues of comfort and security need to be considered. Tasks that are performed on the table, like rolling over, need to be accommodated. Furthermore, the question of how to accommodate morbidly obese individuals still needs to be addressed.

The charts below were developed using a statistical analysis package with some built-in features. The reader will notice data points noted as “extreme values.” The statistical package analyses the data to identify “outliers,” or values that exceed expected values in data with a normal distribution. It then includes those values in the graphics as outside the range of maximum and minimum values in each distribution. The charts serve as a visual aid for understanding how the diversity or spread in measurement values within and between each of the six sub-groups of device users that were studied.

However, the “extreme values” are included in our assessment and recommendations on accommodating 95% of the sample, since these “extreme values” represent genuine cases of individuals (as opposed to errors in measurement) that need to be accommodated by design and hence should not be excluded from the analysis, and, the dimensions that we analyzed were not normal distributed due to a broad diversity in the observed measurements. Hence the percentiles were computed separately based on the observed data and not an implied normal distribution. Readers can assume that these “extreme values” represent unusually large or small dimensions for the population studied that might need special accommodation through design and/or some type of personal assistance.