Chwee Teck Lim, James C.H. Goh (Eds.): ICBME 2008, Proceedings 23, pp. 481–484, 2009 www.springerlink.com An Oscillometry-Based Approach for Measuring Blood Flow of Brachial Arteries S.-H. Liu 1 , J.-J. Wang 2 and K.-S. Huang 3 1 Department of Computer Science & Information Engineering, Chaoyang University of Technology, Taiwan 2 Department of Biomedical Engineering, I-Shou University, Taiwan 3 Hsinchu General Hospital, Department of Health, Executive Yuan, Taiwan Abstract — Although the oscillometric method has been widely used to measure arterial systolic and diastolic blood pressures, its potential for arterial blood flow measurement is still remained to be explored. Thus, the aim of the study was to noninvasively determine the arterial artery blood flow using an oscillometric blood flow measurement system. The system consisted of an elastic cuff, an air-pumping motor, a releaser valve, a pressure transducer, and an airflow meter. To build a nonlinear air cuff model, we detected the pumped airflow into the cuff and the cuff pressure using the airflow meter and pressure transducer during the inflation period, respectively. During the deflation period, only the pressure transducer was used to record the cuff pressure. Based on the air cuff model, the oscillometric blood flow waveform could be obtained by integrating the oscillometric pressure waveform. We compared the derived artery blood flow from the maximum amplitude of the oscillometric blood flow waveform with the Doppler-based blood flow calculated with diameters and blood velocities of the brachial arteries in 32 subjects undergoing diagnostic evaluation for peripheral arterial embolism. A linear regression coefficient of r = 0.72 was found between the oscillometry- and Doppler-based blood flow measurements for the 32 subjects. In conclusion, the oscillometric method can be applied to quantitatively measure the blood flow through a brachial artery. Keywords — Oscillometry, Blood flow, Cuff mode, Doppler, Brachial artery. I. INTRODUCTION The profile of the arterial blood flow is a potential marker of generalized arteriosclerotic disease. Several artery-related diseases, such as stenosis [1], aneurysm [2], atherosclerosis[3] and arterial stiffness[4], can be directly or indirectly diagnosed by measuring changes in the arterial blood flow. Therefore, the ability to measure the blood flow significantly helps medical physicians and researchers to understand not only the patency but also the hemo- dynamic characteristics of the artery of interest. Several methods have been proposed for non-invasively assessing the forearm blood flow in normal, stress and dis- eased conditions. Doppler ultrasound can yield the maxi- mum or average blood velocity in an artery of interest, and then the arterial blood flow can be obtained by multiplying the measured velocity by the cross-sectional area if the diameter of the artery is assumed to remain constant [5]. In the photoplethysmographic approach, the arterial blood flow is indirectly derived from the absorption of incident light by red blood cells and other constituents in an arterial vessel [6]. In electrical-impedance plethysmo-graphy, the blood flow is implicitly assessed by measuring changes in impedance for electrical current passing through the arterial lumen [7]. Oscillometry is most frequently used to measure the arterial blood pressure, but it can also quantify the blood flow in an artery of interest. This study investigated a proposed oscillometric flow measurement system for determining the brachial arterial blood flow. II. OSCILLOMETRIC FLOW MEASUREMENT A. System design Fig. 1 shows a block diagram of our proposed oscil- lometric blood flow measurement system. The relationship between the cuff pressure and the cuff air volume (i.e. the cuff model) was constructed using a non-linear regression approach. During the deflation period, only the pressure Fig. 1 Block diagram of the proposed measurement system. The thick arrows represent the air pathways and the thin arrows the electric current flow. F is the pumped flow, P C_I is the cuff pressure during the inflation period, P osci is the oscillometric pressure waveform during the deflation period, V C is the cuff volume, C cuff represents the slope of the cuff model, and F osci is the oscillometric flow waveform.