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TECHNICAL BRIEFS

In Vitro Study of Flow Regulation for Pulmonary Insufficiency

[+] Author and Article Information
T. A. Camp, K. C. Stewart

Departments of Mechanical Engineering and Bioengineering,  Clemson University, Clemson, SC 29631

R. S. Figliola1

Departments of Mechanical Engineering and Bioengineering,  Clemson University, Clemson, SC 29631

T. McQuinn

Pediatric Cardiology,  Medical University of South Carolina, Charleston, SC

1

Author to whom correspondence should be directed.

J Biomech Eng 129(2), 284-288 (Aug 22, 2006) (5 pages) doi:10.1115/1.2540892 History: Received May 18, 2006; Revised August 22, 2006

Given the tolerance of the right heart circulation to mild regurgitation and gradient, we study the potential of using motionless devices to regulate the pulmonary circulation. In addition, we document the flow performance of two mechanical valves. A motionless diode, a nozzle, a mechanical bileaflet valve, and a tilting disk valve were tested in a pulmonary mock circulatory system over the normal human range of pulmonary vascular resistance (PVR). For the mechanical valves, regurgitant fractions (RFs) and transvalvular pressure gradients were found to be weak functions of PVR. On the low end of normal PVR, the bileaflet and tilting disk valves fluttered and would not fully close. Despite this anomaly, the regurgitant fraction of either valve did not change significantly. The values for RF and transvalvular gradient measured varied from 4 to 7% and 4to7mmHg, respectively, at 5lpm for all tests. The diode valve was able to regulate flow with mild regurgitant fraction and trivial gradient but with values higher than either mechanical valve tested. Regurgitant fraction ranged from 2 to 17% in tests extending from PVR values of 1to4.5mmHglpm at 5lpm and with concomitant increases in gradient up to 17mmHg. The regurgitant fraction for the nozzle increased from 2 to 23% over the range of PVR with gradients increasing to 18mmHg. The significant findings were: (1) the mechanical valves controlled regurgitation at normal physiological cardiac output and PVR even though they failed to close at some normal values of PVR and showed leaflet flutter; and (2) it may be possible to regulate the pulmonary circulation to tolerable levels using a motionless pulmonary valve device.

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Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 5

Physiological signals using diode valve (5lpm, 74bpm, 3.1mmHg∕lpm)

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Figure 6

Regurgitant fraction (RF) and peak-peak transvalvular pressure gradient (PPG) results at 5lpm

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Figure 1

Schematic of the mock circulatory system. Arrows indicate flow direction. 1. Atrial head tank with tricuspid valve. 2. Right ventricular chamber. 3. Flow meter. 4. Test chamber. 5. Mechanical heart valve. 6. Resistance elements. 7. Compliance chambers. 8. Reservoir. 9. Pump. 10. Pressurizing flow valve. 11. Venting flow valve. 12. Resistance head tank.

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Figure 2

Generic representations for flow nozzle and momentum-nozzle diode designs: Systolic flow is left to right

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Figure 3

Physiological signals using SJMBV (5lpm, 75bpm, 3.9mmHg∕lpm)

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Figure 4

Physiological signals using OTDV (5lpm, 75bpm, 2.9mmHg∕lpm)

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