The objective of this study was to determine the instantaneous arterial blood pressure by the peripheral bio-impedance. To achieve this goal, the equation of Ben Salah and Flaud, initially meant to determine the instantaneous aortic pressure according to the signal of thoracic bioimpedance, was successfully applied for the determination of the instantaneous arterial pressure according to the signal of peripheral bio-impedance. The problem was that this equation depends directly on systolic and diastolic pressures which were manually obtained by an electronic sphygmomanometer. Yet the objective was to determine the instantaneous arterial blood pressure without having to measure beforehand diastolic and systolic pressures by the electronic sphygmomanometer. To solve this problem, interpolation function linking respectively the pulse pressure to the impedance variation (with 2,97% error for the determination of the systolic pressure) and the diastolic pressure to the basic impedance were determined (with an error close to zero for the determination of the diastolic pressure). With the proposed method, for each new measurement on a subject we acquire its bioimpedance signal, and then use the interpolation functions to deduce its diastolic and systolic pressures and then, using the Ben Salah equation, in real time, to determine its instantaneous arterial blood pressure. The bio-impedance signal processing, the user interface and the display were managed by LabVIEW.
Key words: Instantaneous arterial pressure, cubic spline interpolation, bioimpedance, electric plethysmography, LabVIEW.
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