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Research Papers

Pop-Up MEMS One-Way Endobronchial Valve for Treatment of Chronic Obstructive Pulmonary Disease

[+] Author and Article Information
Ronit E. Malka

Harvard Medical School,
HST Division,
Harvard School of Engineering and Applied
Sciences,
Cambridge, MA 02138
e-mail: ronit_malka@hms.harvard.edu

Joshua B. Gafford

Department Engineering and Applied Sciences,
Harvard University,
Cambridge, MA 02138
e-mail: jgafford@seas.harvard.edu

Steven C. Springmeyer

Clinical Professor of Medicine
Department of Medicine,
University of Washington School of Medicine,
Seattle, WA 98195
e-mail: sspring@uw.edu

Robert J. Wood

Charles River Professor of Engineering and
Applied Sciences
John A. Paulson School of Engineering and
Applied Sciences,
Wyss Institute for Biologically Inspired
Engineering,
Harvard University,
Cambridge, MA 02138
e-mail: rjwood@seas.harvard.edu

Manuscript received September 7, 2016; final manuscript received July 3, 2017; published online August 17, 2017. Assoc. Editor: Matthew R. Myers.

J. Med. Devices 11(4), 041003 (Aug 17, 2017) (10 pages) Paper No: MED-16-1314; doi: 10.1115/1.4037349 History: Received September 07, 2016; Revised July 03, 2017

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of morbidity in aging populations worldwide. One of the most debilitating effects of COPD is hyperinflation, which restricts the function of healthier portions of the lung, diaphragm, and heart. Bronchoscopic lung volume reduction (BLVR) is a minimally invasive technique to reduce hyperinflation, consisting of one-way valves inserted bronchoscopically that slowly drain the diseased lobe of its accumulated air. Presented here is a novel redesign of current BLVR devices using pop-up microelectromechanical systems (MEMS) manufacturing to create microscale check valves. These operate more reliably than current polymer valves and allow tunable airflow to accommodate widely varying patient physiologies. Analysis and ex vivo testing of the redesigned valve predicted the valve should outlast current valves with a lifetime of well over 8 yr and showed airflow controllability within desired physiological ranges of up to 1.2 SLM. The valve resists backflow twice as well as the current standard valves while permitting comparable forward flow.

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References

Figures

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Fig. 1

Illustration of a physiologically normal lung (a) and a lung affected by heterogeneous emphysema, showing the marked hyperinflation of the right upper lobe (b). Images used with permission from Pulmonx.

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Fig. 2

Pulmonx EBV, showing the outer stent and inner duckbill valve as they would be implanted in a target airway (a) and Spiration IBV, showing flutter valve and anchors as they would be implanted in a target airway (b). Expiratory airflow moves in direction of arrows. Images used with permission of Spiration and Pulmonx.

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Fig. 3

Computer-aided design model of the complete valve (a) and cross-sectional view of model highlighting key design features (b)

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Fig. 4

Pop-up MEMS stacking technique used to get a layered composite that can be released and popped up in 3D

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Fig. 5

Parylene coating of spars, showing flat, laser cut assembly placed on jig (a), spars formed around jig and anchors bent back into place (b), spar-jig interfaces coated with wax (c), entire assembly coated in parylene (d), spars released from jig (e), and wax melted away, leaving a finished parylene-coated device (f)

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Fig. 6

Visualization of the linear correlation between airflow rates and orifice plate area. Increased variability at small areas is visible.

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Fig. 7

Diagram of dimensions of a flexure hinge, showing length L, width w, thickness t, and bending angle θ

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Fig. 8

COMSOL FEA results of the applied stress on the IBV (a) and redesigned outer valve spar (b), with deflection magnified 10× and 1000×, respectively. Insets show points of maximum stress. Maximum stresses of the IBV and redesigned outer valve spar are 375 kN and 57 kN, respectively. Loading was applied as a purely vertical surface load on all components with a positive horizontal component (highlighted) and the anchors were fixed (outlined).

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Fig. 9

Video snapshots of the Spiration IBV during inspiration (a) and expiration (b), and of the redesigned outer valve module during inspiration (c) and expiration (d). Airflow through the valve is denoted at the bottom of each image.

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Fig. 10

Diagrams use a 90deg curvature in the airway to highlight the gap between the valve and airway walls. (a) Original IBV viewed from the side showing contact point on one valve edge and large gap created on the opposite edge. Cross section through IBV inset. Distance between the valve wall and the airway wall (d), the longitudinal profile of the valve (l), and the angle of curvature of the airway (ψ) are labeled. (b) Redesigned outer valve viewed from the side highlighting reduced gap. Cross section through the redesigned outer valve inset. (c) Diagram of gap area A calculation, showing the crescent shape seen in the 3D models shown above and the ring approximation using ring thickness d/2 (d) diagram of the triangle used to calculate d. Shown are d, l, and ψ.

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Fig. 11

Photograph of a manufactured final prototype, pictured next to a Singaporean ten cent coin for perspective (roughly same size as a dime)

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Fig. 12

The final prototype inner valve closed during inspiration (a) and opened during expiration (b). The inner valve opening is shown from the side in (c).

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