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Device Technologies and Biomedical Robotics

Device Technologies and Biomedical Robotics - Poster Session E

Poster W4 - Preliminary Design and Validation of an IMU Based Wearable Balance Assessment System

Saturday, October 26, 2024
10:00 AM - 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction: According to the Centers for Disease Control and Prevention (CDC), individuals over 65 years of age report about 36 million falls in the United States each year, resulting in over 32,000 deaths and serious injuries [1]. This demonstrates the need for prevention through assessing fall risk. Currently, clinicians utilize task-based balance tests and stationary medical devices, such as the Biodex Balance System, to assess fall risk [2] [3]. These assessments are inadequate predictions of long-term fall risk due to a lack of precision, allowed motion, or accessibility. Therefore, a low-cost portable medical device that assesses fall risk through long-term monitoring could provide a more reliable assessment of one’s stability, ultimately resulting in a reduction of falls in geriatric adults [3] [4]. Two of the most common metrics used to estimate fall risk are postural sway and sway velocity, which are respectively the movement of an individual’s center of mass during core stabilization and the speed of this sway [3]. A wearable balance assessment system is being developed to provide a fall risk assessment through calculating minimum and maximum sway displacements, sum of squares of velocity, and root mean squared values of this velocity over a designated time interval. These calculations are interpreted by the device to report a low, medium, or high fall risk rating that clinicians can use to recommend fall prevention strategies and devices. Preliminary prototype testing was conducted to validate the device’s fall risk assessment features to inform design revisions prior to usage on geriatric adults.

Materials and

Methods: The balance assessment system’s physical construction includes a main housing and an ergonomic back piece that are secured onto a belt and 3D printed with ABS. The main housing contains a microprocessor, an LCD screen, and powering components. Enclosed in the backpiece is a six degrees of freedom inertial measurement unit (IMU) that is positioned between the L3 and L5 vertebrae. The IMU processes data from the accelerometer X and Y axes to calculate postural sway and average sway speed based on the minimum and maximum displacements over a specified time interval (10 milliseconds). Utilizing the calculated postural sway and sway speed in the mediolateral and anteroposterior directions, the device reports on the LCD screen an estimated fall risk in the ranges of low, medium, and high. The accuracy of the device’s design was initially compared to the Biodex Balance System, which has been experimentally verified to be effective and is clinically used to estimate stability. During this test, the user completed the Biodex Fall Risk Screening and Conditioning Program while standing on the Biodex and wearing the prototyped balance assessment device. Additionally, the device’s accuracy in measuring postural sway and sway velocity was assessed by engaging participants in the following tasks: standing in anatomical position, standing on a Bosu Balance Ball, walking in a straight line, and walking with eyes closed. The five tests were completed for one-minute durations and repeated three times with four healthy young adults to validate system performance and inform future design and algorithm iterations.

Results, Conclusions, and Discussions: Comparing the wearable balance assessment system to the commercial Biodex Balance System indicated that the wearable system was able to provide a functionally equivalent fall risk assessment over the course of multiple trials. The balance score produced by the Biodex system was a unitless value, but the results correlated to the wearable device’s ranking of a low, medium, or high risk. High fall risk was detected accurately by the wearable balance assessment system as participants experienced decreased core stability while standing on the Bosu Balance Ball. The device provided the desired high-fidelity postural sway and sway velocity of the user while standing in anatomical position to determine their likelihood of experiencing future falls. However, flaws in the software’s filtering process were exposed during the trials with participants walking. Analysis of the data collected during the walking trials revealed that forward acceleration due to walking distorted the desired measurement of anteroposterior sway. This necessitated software refinements to disregard forward strides and varied cadences during gait while identifying changes in core stability during walking. Future work should focus on further algorithm refinement and validation for balance assessment during walking. Additionally, a second IMU placed at the thigh should be integrated in the device to detect whether a person is sitting, standing, or walking. With these refinements, this low-cost, long-duration wearable balance assessment system could have a global impact by helping to reduce falls of geriatric patients around the world, ultimately saving lives.

Acknowledgements (Optional):

References:
[1] CDC, “Keep on Your Feet,” Centers for Disease Control and Prevention, Dec. 16, 2020. https://www.cdc.gov/injury/features/older-adult- falls/index.html#:~:text=About%2036%20million%20falls%20are
[2] S. Subramaniam, A. I. Faisal, and M. J. Deen, “Wearable Sensor Systems for Fall Risk

Assessment: A Review,” Frontiers, Jul. 14, 2022. https://www.frontiersin.org/journals/digital-health/articles/10.3389/fdgth.2022.921506/full
[3] Howcroft, J., Kofman, J. & Lemaire, E.D. Review of Fall Risk Assessment in Geriatric Populations Using Inertial Sensors. J NeuroEngineering Rehabil 10, 91 (2013). https://doi.org/10.1186/1743-0003-10-91
[4] Dubois, A., Bihl, T., & Bresciani, J. P. (2021). Identifying Fall Risk Predictors by Monitoring Daily Activities at Home Using a Depth Sensor Coupled to Machine Learning Algorithms. Sensors (Basel, Switzerland), 21(6), 1957. https://doi.org/10.3390/s21061957