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  • 1
    Electronic Resource
    Electronic Resource
    Estimation of arterial compliance in aortic regurgitation: three methods evaluated in pigs (1990)
    Springer
    Medical & biological engineering & computing 28 (1990), S. 293-299 
    Details
    ISSN: 1741-0444
    Keywords: Aortic regurgitation ; Arterial compliance ; Fourier analysis ; Impedance ; Mean aortic pressure ; Peripheral resistance ; Windkessel model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Three methods for measuring arterial compliance when aortic regurgitation is present are examined. The first two methods are based on a Windkessel model composed of two elements, compliance C and resistance R. Arterial compliance was estimated from diastolic pressure waveforms and diastolic regurgitant flow for one method, and from systolic aortic pressure waveforms and systolic flow for the other method. The third method was based on a three-element Windkessel model, composed of characteristic resistance r, compliance C and resistance R. In this method arterial compliance was calculated by adjusting the model to the modulus and phase of the first harmonic term of the aortic input impedance. The three methods were compared and validated in six anaesthetised pigs over a broad range of aortic pressures. The three methods were found to give quantitatively similar estimates of arterial compliance at mean aortic pressures above 60 mm Hg. Below 60 mm Hg, estimates of arterial compliance varied widely, probably because of poor validity of the Windkessel models in the low pressure range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02446145
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Quantification of aortic regurgitation by Doppler echocardiography: a new method evaluated in pigs (1990)
    Springer
    Medical & biological engineering & computing 28 (1990), S. 300-305 
    Details
    ISSN: 1741-0444
    Keywords: Aortic regurgitation ; Doppler ultrasound ; Electromagnetic flow probes ; Parameter estimation ; Regurgitant orifice ; Regurgitant volume ; Windkessel model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We have developed a method to quantify aortic regurgitant orifice and volume, based on measurements of the velocity of the regurgitant jet, aortic systolic flow, the systolic and diastolic arterial pressures, a Windkessel arterial model, and a parameter estimation technique. In six pigs we produced aortic regurgitant flows between 2·1 and 17·8 ml per beat, i.e. regurgitant fractions from 0·06 to 0·58. Pulmonary and aortic flows were measured with electromagnetic flow probes, aortic pressure was measured invasively, and the regurgitant jet velocity was obtained with continuous-wave Doppler. The parameter estimation procedure was based on the Kalman filter principle, resulting primarily in an estimate of the regurgitant orifice area. The area was multiplied by the velocity integral of the regurgitant jet to estimate regurgitant volume. A strong correlation was found between the regurgitant volumes obtained by parameter estimation and the electromagnetic flow measurement. These results from our study in pigs suggest that it may be possible to quantify regurgitant orifice and volume in patients completely noninvasively from Doppler and blood pressure measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02446146
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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