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Research Papers

A Shape Memory Alloy-Based Compression Therapy Prototype Tested With Individuals in Seated Position

[+] Author and Article Information
Hadi Moein

Mem. ASME
MENRVA Research Group,
Schools of Mechatronic Systems Engineering
and Engineering Science,
Simon Fraser University,
Metro Vancouver,
Burnaby, BC V5A-1S6, Canada
e-mail: hmoein@sfu.ca

Alex Wu

MENRVA Research Group,
Schools of Mechatronic Systems Engineering
and Engineering Science,
Simon Fraser University,
Metro Vancouver,
Burnaby, BC V5A-1S6, Canada
e-mail: wualexw@sfu.ca

Carlo Menon

Mem. ASME
MENRVA Research Group,
Schools of Mechatronic Systems Engineering
and Engineering Science,
Simon Fraser University,
Metro Vancouver,
Burnaby, BC V5A-1S6, Canada
e-mail: cmenon@sfu.ca

Manuscript received September 1, 2016; final manuscript received July 26, 2017; published online August 16, 2017. Assoc. Editor: Elizabeth Hsiao-Wecksler.

J. Med. Devices 11(4), 041002 (Aug 16, 2017) (10 pages) Paper No: MED-16-1312; doi: 10.1115/1.4037441 History: Received September 01, 2016; Revised July 26, 2017

Orthostatic intolerance in patients can occur secondary to concomitant venous pooling and enhanced capillary filtration when standing upright, and is one of the principle causes of syncope or fainting. Compression therapy is commonly recommended for the management of syncope based on the assumption that it increases venous return. Technologies currently used include compression stockings, whose efficacy has, however, been challenged, and intermittent pneumatic pressure devices, which highly restrict the patients' mobility. This paper therefore investigates a novel active compression brace (ACB), which could potentially provide intermittent pressure while not restricting movements. The ACB, actuated by shape memory alloy (SMA) wires, in this work was tested with twelve healthy individuals in a seated position. The experimental observation showed that the ACB can apply a constant initial pressure to the leg similar to commercial compression stockings and also produce intermittent pressure exceeding 30 mmHg. A comparison between analytical and experimental results showed a maximum of 2.08 mmHg absolute averaged difference among all the participants. A correlation analysis showed that the normalized root-mean-square deviation (NRMSD) between the experimental and analytical results had a significant negative correlation with the estimated total calf circumference minus the calf fat cross-sectional area (CSA). A calibration formula, accounting for fat and circumference of the leg, was introduced to account for these two parameters. The comfort of the ACB was also compared to two other available compression devices using questionnaires. No participants reported discomfort in terms of pressure, skin irritation, or heat generated by the ACB.

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Figures

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Fig. 1

(a) Active compression brace, (b) experimental setup, and (c) active compression brace wrapped around the calf

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Fig. 2

Cyclic tests setup: the ACB was wrapped around a rigid leg mannequin having the PicoPress probe in the interface

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Fig. 3

Cyclic tests results for three trials of applied current: (a) 100 mA, (b) 150 mA, and (c) 200 mA

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Fig. 4

(a) A representative example from one of the participants showing the trace of total interface pressure exerted by the ACB on the calf and applied electrical current and (b) experimental and simulation results for actuation pressure versus applied current per SMA wire

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Fig. 5

Experimental and simulation differences versus current for each participant

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Fig. 6

Relationships between RMSD of simulation and experimental results with calf CSA minus calf fat CSA

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Fig. 7

(a) NRMSD between simulation and experimental results for produced pressure by ACB before and after analytical model calibration (a) for each applied current and (b) for each participant

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Fig. 8

Mean and standard error of participant ratings of comfort obtained (a) after the human tests with ACB and (b) after comparative tests of three different devices

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