Pumps – Condition responsive control of pump drive motor – With condition responsive control of pump fluid valve
Patent
1992-10-27
1994-02-08
Bertsch, Richard A.
Pumps
Condition responsive control of pump drive motor
With condition responsive control of pump fluid valve
417 45, 417415, F04B 4900
Patent
active
052844234
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates in general to flow simulation devices and more particularly to a computer-controlled positive displacement pump for producing simulated physiological flow waveforms.
BACKGROUND OF THE INVENTION
The ability to reproduce realistic arterial flow waveforms in vitro is essential in the study of vascular haemodynamics. Simulated pulsatile flow has been used extensively in previous investigation of flow in arterial models with bifurcations and stenoses. Many different techniques have been used to measure flow in these models, including (1) laser Doppler anemometry (Ku, D. N, and Giddens, D. P. (1987): Laser Doppler Anemometer Measurements of Pulsatile Flow in a Model Carotid Bifurcation J. Biomechanics, 20, 407-421), (2) Doppler ultrasound (Cho, Y. I., Back, L. H., Crawford, D. W., Cuffel, R. F. (1983): Experimental Study of Pulsatile and Steady Flow Through a Smooth Tube and an Athersclerotic Coronary Artery Casting of Man, J. Biomechanics, 16, 933-946.); and (Fei D. Y., Billian, C., Rittgers, S. E. (1988): Flow Dynamics in a Stenosed Carotid Bifurcation Model-Part 1: Basic Velocity Measurements, Ultrasound in Med. & Biol., 14, 21-31), (3) magnetic resonance (Evans, A. J., Hedlund, L. W., Herfkens, R. J., Utz, J. A., Fram, E. K., (1987): Evaluation of Steady and Pulsatile Flow with Dynamic MRI Using Limited Flip Angles and Gradient Refocused Echoes, Magnetic Resonance Imaging, 5, 475-482); and (4) digital radiography (Cunningham, I. A., Yamada, S., Hobbs, B. B., Fenster A., (1989): Arterial Flow Characterization with a Photodiode Array Based Imaging System. Med. Phys., 16, 179-187).
Physiological pulsatile flow waveforms are also required to investigate the role of pulsatility in tissue perfusion (Tranmer, B. I., Gross, C. E., Kindt, G. W., Adey, G. R., (1986): Pulsatile Versus Nonpulatile Cardiovascular Studies, Med. & Biol. Eng. & Comput., 22, 86-89).
Finally, the ability to mimic arterial flow is essential for quality assurance and calibration of all clinical techniques of blood flow measurement, such as Doppler ultrasound (McDicken, W. N. (1986): A Versatile Test-object for the Calibration of Ultrasonic Doppler Flow Instruments, Ultrasound in Med. & Biol., 26, 245-249); and Shortland, A. P., Cochrane, T., (1989): Doppler Spectral Waveform Generation in vitro: An Aid to Diagnosis of Vascular Disease, Ultrasound in Med. & Biol., 15, 737-748).
Most of the prior art techniques for the investigation of time-varying flow require gated acquisition of many cardiac cycles, so cycle-to-cycle variability in the flow waveform must be small. Longterm stability is equally important for quality assurance applications where the flow source may be used for absolute calibration of clinical instruments. Therefore, a blood flow simulator must be capable of producing a wide range of flow rates in order to simulate flow in the peripheral vasculature, where peak flow rates of 30 ml s.sup.-1 have been reported (Marquis, C., Meister, J.-J., Mooser, E., and Misoman, R., (1986): Quantitative Pulsed Doppler Measurement of Common Femoral Artery Blood Flow Variable during Postocclusive Reactive Hyperemia, J. Clin. Ultrasound, 14, 165-170). It must be easily programmed to produce a variety of pulsatile waveforms, including waveforms with flow reversal. The simulator must be capable of producing continuous steady flow, which is required as the basis for many experimental investigations and calibration procedures. It is essential that a pumping mechanism not produce gas bubbles or cavitation, since bubbles change the hydrodynamic properties of the fluid, and their presence will produce measurement artifacts, particularly with ultrasound instrumentation. Finally, a device to stimulate physiological flow should operate as an ideal flow source, capable of generating sufficient pressure to be unaffected by changes in the peripheral resistance of the model vascular system under investigation.
Many different pumps have been proposed to meet these requirements, and Law, Y. F., Cobbold, R. S. C., Jo
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Dranova Maria
Fenster Aaron
Holdsworth David
Miller John
Rickey Daniel W.
Bertsch Richard A.
Scheuermann David W.
University Hospital (London) Development Corporation
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