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Research Papers

A Wireless System for Evaluating Postural Position

[+] Author and Article Information
Amy R. Sipp

Department of Biomedical, Industrial, and Human Factors Engineering, Wright State University, 207 Russ Engineering Center, 3640 Colonel Glenn Highway, Dayton, OH 45435amysipp@umich.edu

Blair A. Rowley

Department of Biomedical, Industrial, and Human Factors Engineering, Wright State University, 207 Russ Engineering Center, 3640 Colonel Glenn Highway, Dayton, OH 45435blair.rowley@wright.edu

J. Med. Devices 3(4), 041001 (Nov 10, 2009) (8 pages) doi:10.1115/1.4000409 History: Received January 13, 2009; Revised September 11, 2009; Published November 10, 2009; Online November 10, 2009

Falls account for almost two million emergency department visits per year in the United States and are the leading cause of injury deaths among adults 65 years of age and older. Despite efforts to reduce fall risk factors, about one-third of community-dwelling older adults fall each year in the United States. New methods and devices are needed to prevent falls and to reduce morbidity and mortality related to falls. Presently, it is unknown if there is a measurable change in sway before a person falls as a result of age or medical condition. The purpose of this research is to develop a device that can be used to measure the prefall motion outside of a laboratory setting. To study human prefall motion, we developed a gyroscope-based sensor to test two concepts. The first was that a single-axis gyroscope could be used to directly measure angular position changes due to postural perturbations. The second was that a small widely used microprocessor could be used to distinguish normal from potentially problematic motion. This proof-of-concept prototype counted how many times perturbations occurred that were unlikely to be due to normal activities such as walking and stair climbing. With these basic concepts demonstrated, we sought to expand the device into a more versatile form using the same general approach. A wireless data acquisition system was developed. A fall was induced to allow the study of prefall motion on a healthy subject. The data collected showed a measureable change in postural motion. The developed device provides a viable approach to evaluating postural angular position that can be used outside of a laboratory facility. Further testing and development will involve additional subject testing and expansion of the device to function as an early fall detection or warning system. This research serves as a basis for further work in postural sway and interventions to prevent falls.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Proof-of-concept hardware

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Figure 2

Proof-of-concept software flowchart

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Figure 3

Proof-of-concept measure pulse width routine flowchart. The cut-off values used here are discussed in Proof-of-Concept Protocol.

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Figure 4

The three filters used are shown here. Filter A used the center exclusion band, filter B used the outer exclusion bands, and filter C used both the center and outer exclusion bands.

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Figure 5

The sensor unit comprised of the pulse generator, gyroscope, microprocessor, transmitter, printed circuit boards, and power supply (9 V battery)

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Figure 6

The sensor unit ready for placement on the subject

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Figure 7

Testing setup. To study motion in the frontal plane, the orientation shown in A was used. To study motion in the sagittal plane, the orientation shown in B was used.

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Figure 8

Angular position recorded with the sensor at hip level while the subject was standing on the narrow beam in a toe-to-heel position. The dark spots represent the actual measurement values, and the gray bars show the accuracy of the sensor.

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Figure 9

Angular position recorded with the sensor at hip level while the subject was standing on the narrow beam in a toe-to-heel position with the eyes closed, which resulted in a fall

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Figure 10

Elderly subject postural position recorded with the sensor at hip level, while the subject was standing on the narrow beam in a toe-to-heel position with the eyes open, which resulted in a fall

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