Research Papers

Development and Experimental Validation of A Handheld Noninvasive Sensor for the Measurement of Compartment Pressures

[+] Author and Article Information
C. Flegel, K. Singal, R. Rajamani

Department of Mechanical Engineering,
University of Minnesota,
Minneapolis, MN 55455

R. Odland

Department of Orthopedic Surgery,
University of Minnesota,
Minneapolis, MN 55455

Manuscript received July 1, 2013; final manuscript received December 14, 2013; published online January 9, 2014. Assoc. Editor: Rosaire Mongrain.

J. Med. Devices 8(1), 011008 (Jan 09, 2014) (7 pages) Paper No: MED-13-1160; doi: 10.1115/1.4026295 History: Received July 01, 2013; Revised December 14, 2013

Compartment syndrome is a major concern in cases of extremity trauma, which occur in over 70% of military combat casualty. Without treatment, compartment syndrome can lead to paralysis, loss of limb, or death. This paper focuses on the development of a handheld sensor that can be used for the noninvasive diagnosis of compartment syndrome. Analytical development of the sensing principle is first presented in which a relation is obtained between the pressure in a fluid compartment and the stiffness experienced by a handheld probe pushing on the compartment. Then a handheld sensor that can measure stiffness of an object without requiring the use of any inertial reference is presented. The handheld sensor consists of an array of three miniature force-sensing spring loaded pistons placed together on a probe. The center spring is chosen to be significantly stiffer than the side springs. The ratio of forces between the stiff and soft springs is proportional to the stiffness of the soft object against which the probe is pushed. Small millimeter-sized magnets on the pistons and magnetic field measurement chips are used to measure the forces in the individual pistons. Experimental results are presented using both an in vitro pneumatic test rig and a compliant agarose gel chamber that replicates a fluid pressure compartment. The sensor is shown to measure pressure accurately with a resolution of 0.1 psi over the range 0.75–2.5 psi. The developed sensor has the potential to be useful for convenient handheld diagnosis of compartment syndrome in traumatic extremity injuries.

Copyright © 2014 by ASME
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Fig. 1

Handheld magnetic force sensor

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Fig. 2

Force on an infinite elastic half-space [11]

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Fig. 3

X-Z cross section of an elastic half-space deformed by a spherical indenter [11]

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Fig. 4

Sensor cut section diagram showing input forces and spring rates

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Fig. 5

Sensor pressed against pressurized surface

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Fig. 6

Sensor force output readings for one test trial

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Fig. 7

Raw Rf plot from Fig. 5 test trial

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Fig. 8

Rf plot with 1 N lower force bound

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Fig. 9

Movable stage and compressed air vessel setup

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Fig. 10

Pressure regulating valve and gauge

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Fig. 11

Linear correlation between internal vessel pressure and sensor response for compressed air

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Fig. 12

1.0% agarose gel pressure compartment setup: (a) overall system and (b) side-view showing polyurethane surface used to obtain sensor readings

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Fig. 13

Internal pressure transducer readings (gauge) during handheld testing

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Fig. 14

Linear correlation between internal vessel pressure and sensor response for agarose gel




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