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  • Articles  (5)
  • Mathematical modeling  (5)
  • 2000-2004
  • 1990-1994  (5)
  • 1985-1989
  • 1950-1954
  • 1945-1949
  • 1994  (5)
  • Technology  (5)
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  • Articles  (5)
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  • 2000-2004
  • 1990-1994  (5)
  • 1985-1989
  • 1950-1954
  • 1945-1949
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  • 1
    Electronic Resource
    Electronic Resource
    Clinical application of end-systolic pressure-volume relation (1994)
    Springer
    Annals of biomedical engineering 22 (1994), S. 212-217 
    Details
    ISSN: 1573-9686
    Keywords: Cardiac mechanics ; Ventricular function ; Pump function ; Mathematical modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract On the basis of a mathematical formalism derived in previous studies, properties of the end-systolic pressure-volume (P-V) relation were analyzed to define indexes that can characterize a normal or failing left ventricle. Careful analysis of different areas under the P-V line can lead to new indexes that describe the performance of the left ventricle. The possibility to distinguish between normal, midly depressed, or severely depressed left ventricles based on P-V relation is discussed. Implementation of the results for routine clinical work is examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02390379
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A mathematical model of thrombin production in blood coagulation, Part I: The sparsely covered membrane case (1994)
    Springer
    Annals of biomedical engineering 22 (1994), S. 357-370 
    Details
    ISSN: 1573-9686
    Keywords: Mathematical modeling ; Blood coagulation ; Thrombin ; Blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract This paper presents the first attempt to model the blood coagulation reactions in flowing blood. The model focuses on the common pathway and includes activation of factor X and prothrombin, including feedback activation of cofactors VIII and V by thrombin, and plasma inhibition of factor Xa and thrombin. In this paper, the first of two, the sparsely covered membrane (SCM) case is presented. This considers the limiting situation where platelet membrane binding sites are in excess, such that no membrane saturation or binding competition occurs. Under these conditions, the model predicts that the two positive feedback loops lead to multiple steady-state behavior in the range of intermediate mass transfer rates. It will be shown that this results in three parameter regions exhibiting very different thrombin production patterns. The model predicts the effect of flow on steady-state and dynamic thrombin production and attempts to explain the difference between venous and arterial thrombi. The reliance of thrombin production on precursor procoagulant protein concentrations is also assessed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02368242
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Parameter identification in coronary pressure flow models: A graphical approach (1994)
    Springer
    Annals of biomedical engineering 22 (1994), S. 622-637 
    Details
    ISSN: 1573-9686
    Keywords: Mathematical modeling ; Parameter identifications ; Sensitivity analysis ; Myocardium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The confident identification of parameters is important in the practical application of physiological modesl. However, the task of parameter identification is often complicated by interactions among parameters and by the fact that the sensitivity of the model to changes in a given parameter is generally a function of all the other parameters. Here we illustrate a graphical approach to parameter identification that allows the modeler to visualize the behavior of the model, the sensitivity functions, and certain functions characteristic of parameter interdependence. The visual display can be generated over any desired portion of parameter space. The technique is applied to a simple, four-parameter, myocardial pump model of the coronary circulation. The results indicate that over specified ranges of parameters, it is possible to distinguish among the four parameters of the model: the ratio of proximal-to-distal resistance, α; the overall resistance of the vascular bed, R; the compliance of the vascular bed, C; and a parameter, κ, relating tissue pressure to left ventricular pressure. It was found that in order to identify all parameters uniquely, it was necessary to regress upon both coronary inflow and outflow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02368288
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  • 4
    Electronic Resource
    Electronic Resource
    Theory of the oscillometric maximum and the systolic and diastolic detection ratios (1994)
    Springer
    Annals of biomedical engineering 22 (1994), S. 88-96 
    Details
    ISSN: 1573-9686
    Keywords: Oscillometry ; Blood pressure measurement ; Arterial mechanics ; Occlusive cuff ; Mathematical modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract It is proposed that the maximum in cuff pressure oscillations during oscillometry is due to the buckling of the brachial artery under a cuff. This theory is investigated by means of a mathematical model of oscillometry that includes the mechanics of the occlusive arm cuff, the arterial pressure pulse waveform, and the mechanics of the brachial artery. A numerical solution is provided for the oscillations in cuff pressure for one cycle of cuff inflation and deflation. The buckling pressure is determined from actual arterial data and the von Mises buckling criteria. The buckling of an artery under a cuff occurs near — 2 to 0 mm Hg transmural pressure. This effect corresponds with a maximum arterial compliance and maximum cuff pressure oscillations when cuff pressure is nearly equal to mean arterial pressure (MAP), in support of the suggested theory. The model was also found to demonstrate the basic characteristics of experimental oscillometry, such as an increasing and decreasing amplitude in oscillations as cuff pressure decreases, the oscillations that occur when cuff pressure is above systolic pressure, maximum oscillation amplitudes in the range of 1 to 4 mm Hg, and an oscillatory maximum at cuff pressure equal to MAP. These findings support the case that the model is representative of oscillometry. Finally, the model predicted values for the systolic and diastolic detection ratios of 0.593 and 0.717, respectively, similar to those found empirically. These ratios alter with blood pressure, but the tightness of the cuff wrap did not change their value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02368225
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  • 5
    Electronic Resource
    Electronic Resource
    A study of optimal configuration and control of a multi-chamber balloon for intraaortic balloon pumping (1994)
    Springer
    Annals of biomedical engineering 22 (1994), S. 524-531 
    Details
    ISSN: 1573-9686
    Keywords: Mathematical modeling ; Cardiovascular system ; Computer simulation ; Cardiac assist device
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Balloon configuration and control scheme are important for the optimization of assistance of the failing heart with an intraaortic balloon pumping device. In this work, the configuration of a multi-chamber balloon and control schemes have been investigated by using a hemodynamic model and computer simulation methods. Following the simulation study, physical testing and animal experiments were performed to demonstrate the simulation results. Results show that the optimal configuration and controlled multi-chamber balloon can provide better assistance to the failing heart. Based on the simulation and experimental results, it was found that the shape of the rear chamber of a multi-chamber balloon is critical. The optimal control scheme was to inflate the rear chamber first and deflate it last.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02367088
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