Effects of Different Blood Flow Models on the Determination of Arterial Characteristic Impedance

• Published in: IFAC Proceedings Volumes Vol. 45; no. 2; pp. 918 - 923
• Main Authors: Hametner, Bernhard, Weber, Thomas, Mayer, Christopher, Kropf, Johannes, Wassertheurer, Siegfried
• Format: Journal Article
• Language: English
• Published: 2012
• Subjects: arterial characteristic impedance; arterial stiffness; blood flow model; pulse wave analysis; wave separation; arterial stiffness; blood flow model; wave separation; arterial characteristic impedance; pulse wave analysis
• ISSN: 1474-6670
• DOI: 10.3182/20120215-3-AT-3016.00162

Within the concept of pulse wave analysis, arterial pressure and flow curves over a whole cardiac cycle are analyzed. The ratio of pressure to flow in the frequency domain is called impedance. The characteristic impedance (Zc) is obtained when pressure and flow waves are not influenced by wave reflection. The aim of this work is to evaluate the effects of different blood flow models on the determination of the characteristic impedance compared to flow curves gained from ultrasound measurements. The simplest model to approximate aortic blood flow is a curve of triangular shape. Another approach is to use an averaged flow curve from readings of different subjects, and recently a new blood flow model based on Windkessel theory was developed (ARCSolver flow model). In a study population of 148 patients for the evaluation of the different models the input impedance and subsequently the characteristic impedance is calculated in the frequency domain. The mean characteristic impedance using flow curves from ultrasound images is 0.22 (0.08 SD) AU. For the triangular flow a mean difference to the ultrasound flow for Zc of -0.148 (0.097 SD) is found. For the averaged flow a mean difference for Zc of 0.027 (0.036 SD) AU and for the ARCSolver flow a mean difference of 0.016 (0.039 SD) AU compared to the ultrasound flow is obtained. These results indicate that the characteristic impedance strongly depends on the accuracy of the used flow model. While the averaged and the ARCSolver flow provide good estimates for impedance, the triangular flow curve seems to be too simplistic for getting accurate values.