Estimation of blood flow rate from blood pressure measurements

Srinivas Sathyanarayana Dagalur

doi:10.17918/00000638

The purpose of this study was to develop an algorithm to estimate arterial blood flow using intra-arterial blood pressure measurements. This study was based on modeling the arterial vasculature by an seven element hemodynamic model comprising of a four-element lumped transmission-line model and a three-element Westkessel model. Using circuit analysis, the hemodynamic model was represented by equations relating the two intra-arterial blood pressures to the seven hemodynamic parameters in the Frequency Domain and Discrete-Time Domain. In the Frequency Domain representation, the hemodynamic model was represented as a system of linear equations. The model was estimated using the following Linear Algebra techniques: Gauss Elimination, QR factorization, Singular Value Decomposition, and Non-Negative Least Squares methods. In the Discrete-Time Domain representation, the hemodynamic model was represented as an AutoRegressive model with eXternal input (ARX model). The model was estimated using the following System identification techniques: Least Squares and Instrumental Variable methods. Following estimation of the model, blood flow was calculated from equations generated using circuit analysis. Hemodynamic model simulation involved calculating the lumped circuit elements, calculating pressures and blood flow. Different data sets based on different arterial properties were used to provide sensitivity analysis. The comparison between the estimated flow and the model-simulated flow, suggested that the algorithm could estimate blood flow with high accuracy. It was also observed that the algorithm estimated blood flow in the presence of random additive noise. The algorithm was also validated using in vitro experimental data. The experimental data consisted of measured flow and of two pressure measurements. The algorithm determined the hemodynamic model from the measured two pressures and estimated the flow. The estimated flow was compared with measured flow and the results had a high degree of correlation. Currently there is no clinically accepted method to measure blood flow continuously. The proposed algorithm utilizes two continuous blood pressure measurements and estimates the blood flow using existing clinical procedures. Further, measurements in the absence of noise indicated that this algorithm does not require any calibration.

Estimation of blood flow rate from blood pressure measurements

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Estimation of blood flow rate from blood pressure measurements

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