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TECHNICAL PAPERS

Harmonic Analysis of Perfusion Pumps

[+] Author and Article Information
F. Carroll Dougherty, F. M. Donovan

Department of Mechanical Engineering, University of South Alabama, Mobile, AL 36688

Mary I. Townsley

Department of Physiology, University of South Alabama, Mobile, AL 36688

J Biomech Eng 125(6), 814-822 (Jan 09, 2004) (9 pages) doi:10.1115/1.1632524 History: Received June 14, 2002; Revised July 07, 2003; Online January 09, 2004
Copyright © 2003 by ASME
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References

Figures

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Comparison of recorded signal with the approximation from Fourier Analysis, where (a), the approximation is computed using only the first 10 computed harmonics, frequency range of only about 2.5 Hz, or (b), a larger frequency range encompassing the first 10 key harmonics (the 10 largest amplitudes). The latter provides for a much improved approximation.
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Impact of changing perfusate viscosity. Pressure traces in the ex vivo circuit are compared for the Masterflex roller pump when saline (viscosity=1.06 centipoise) and Dextran (viscosity=3.6 centipoise) were used as the perfusate. Graphs (a) and (b) show the upstream pressure traces and approximations for saline and Dextran respectively. Graphs (c) and (d) compare the upstream and downstream pressure traces for both fluids. The downstream Dextran pressure signal is greatly attenuated by the increased viscosity.
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Harmonic signature for the Masterflex roller pump for the saline and Dextran cases. Note that the scale has been changed for the Dextran downstream pressure.
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Analysis of Masterflex roller pump with the compliance chamber in the test circuit. Graphs (a) and (b) show the pressure traces upstream and downstream of the compliance chamber. The harmonic signatures for each trace are shown in graphs (c) and (d). Note the change of scale in graph (d). Although the signal downstream of the compliance chamber is greatly attenuated, residual harmonics are still apparent.
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Impact of changing flow rate on the harmonic signature. Pressure traces from three different flow rates delivered by the Masterflex roller pump were analyzed: (a) Q∼300 mL/min, (b) Q∼600 mL/min, and (c) Q∼1000 mL/min. While the period of the key harmonics increases with the flow rate, the pattern of significant harmonics does not change.
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Sketch of extracorporeal circuit for pump studies. In the test section, a compliance chamber, isolated lung lobe, or tubing could be incorporated
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In vivo pressure trace (a) and resulting harmonic signature (b). Graph (a) shows both the recorded signal and the approximation computed using Fourier Analysis. The first harmonics in (b) are based on the ventilator; the first key harmonic occurs at about 2.5 Hz, which corresponds to the heart rate of the animal.
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Pressure traces for the isolated lung case using the Masterflex roller pump. The upstream pressures are shown in graphs (a) and (b). The pressure trace for graph (b) was taken with the ventilator turned off. Graphs (c) and (d) are pressure traces taken downstream of the lung lobe. Again, graph (d) is taken with the ventilator off. The effect of the ventilation is evident in (a) and (c) as a long, slow sinusoidal wave.
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Harmonic signatures for the isolated lung case using the Masterflex roller pump. Graphs (a) and (b) are the signatures for the upstream pressure with the ventilator on and off, respectively. Graphs (c) and (d) are the signatures for the downstream pressures (note scale change) with the ventilator on and off, respectively. The lack of ventilation is very evident at the low frequencies in (b) and (d), while the key harmonics remain unaffected.
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Pressure and flow traces for a different isolated lung using the Masterflex roller pump. Graph (a) shows the recorded upstream pressure trace and the computed approximation. The flow trace is shown in (b). The harmonic signatures for both traces are shown in (c) and (d). The key harmonics occur at the same frequencies in both plots.
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Harmonic signature comparisons for three typical perfusion pumps. The top two graphs show the upstream pressure trace and its harmonic signature for the Masterflex roller pump. The middle two graphs show the upstream pressure and harmonic signature for the Harvard peristaltic pump. The bottom two graphs are the pressure trace and harmonic signature for the Harvard piston pump. Note scale changes between pumps for the harmonic signatures. Each pump yields a unique signature.
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Comparison of harmonics derived from pressure and flow signals for the three perfusion pumps. The Masterflex roller pump pressure and flow harmonic signatures are shown in the top two graphs. The middle two graphs show the pressure and flow harmonic signatures for the Harvard peristaltic pump. Harmonic signatures for pressure and flow for the Harvard piston pump are shown in the bottom two graphs. Note the different scales for each pump. The harmonic signatures are consistent with those in Fig. 11.

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