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Blood pressure reflects the status of our cardiovascular system. For the measurement of blood pressure, we typically use brachial devices on the upper arm, and much less often, the radial devices with pressure sensors on the wrist. Medical doctors know that this is an unfortunate case. The brachial pressure and even more, the radial pressure, both are poor replacements for the central aortic pressure (CAP). Moreover, the devices on the market cannot provide continuous measurements 24 h. In addition, most of the ambulatory and wearable monitors do not enable acquisition of the blood pressure curves in time. These circumstances limit the accuracy of diagnosing. The aim of this chapter is to introduce our experiments, experiences and results in developing the wearable monitor for central aortic blood pressure curve by using electrical bioimpedance sensing and measurement. First, electronic circuitry with embedded data acquisition and signal processing approaches is given. Second, finding appropriate materials, configurations and placements of electrodes is of interest. Third, the results of modelling and simulations are discussed for obtaining the best sensitivity and stability of the measurement procedures. Finally, the discussion on the provided provisional experiments evaluates the obtained results. The conclusions are drawn together with the need for further development.

Wearable devices that monitor our vital signs have been gaining more importance with each year. Non-invasive, continuous, accurate and precise blood pressure assessment method integrated in a wearable is a multidisciplinary challenge. This work presents an electrical bioimpedance (EBI) unit for multi-frequency measurements on pulsating artery for central aortic pressure (CAP) estimation. The developed device provides low complexity in the electronics design with a frequency range between 1 kHz and 200 kHz. It is able to register the impedance of blood vessel volume change simultaneously at different locations. Experiments were carried out in vivo by using the four-electrode configuration on human thorax, axillary artery and radial artery. Preliminary results show the applicability of the proposed impedance spectroscopy system to measure blood vessel volume changes. The impedance data can be later interpreted into the aortic blood pressure wave by using a generalized transfer function. In addition, experimental test-phantom and electrode design are introduced for testing purposes of the impedance system.