Abstract
The social and economic impact of cardiovascular diseases and the importance of efficient early diagnostic tools are self-evident. This project finds its motivation in the foreseeable impact that an accurate, non-invasive and easy-to-use instrument for hemodynamic condition assessment could introduce on the diagnosis and follow-up of these diseases. It aims at developing and testing of a microcontroller based signal monitoring device for cardiovascular studies. The advantages of this system show up in decreasing the associated cost, as well as in increasing its functionality, making the necessary human intervention minimal. The algorithmic component of the project will focus on the main hemodynamic issues currently addressed in literature: separating incident from reflected pulse waves (augmentation index), waveform variability and transfer function Although, additional studies are still required to attain clinical validation, this system seems to be a valid, low cost and easy to use alternative to the highly costly devices in the market. © 2011 IEEE.

Abstract
Four optical probes were developed to measure the arterial distension waveform generated by the ventricular contraction and assess clinically relevant information. The pressure wave propagates through the arterial tree and can be measured in the peripheral arteries. The probes make use of two distinct photo-detectors: planar and avalanche photodiodes. Independently, two different light sources were tested: visible and infrared light. Performance of the probes was evaluated in a test setup that simulates the fatty deposits commonly seen in the obese, between skin and the artery. The probes show good overall performance in the test setup with less than 8% root mean square error (RMSE). However, the probes lit with IR sources show better results for the more extreme cases, with a better resolution in the waveform, higher definition of notable points and higher SNR when compared to the visible source signals. In vivo, the IR probes allow easier waveform detection, even more relevant with the increasing of the deposit structures.

Abstract
In this work, we discuss an algorithm that reliable and accurately identifies the prominent points of the cardiac cycle: the systolic peak (SP), reflection point (RP), dicrotic notch, (DN) and dicrotic peak (DP). The prominent point's identifier algorithm (PPIA) action is based on the analysis a number of features of the arterial pressure waveform and its first derivative, and is part of the fundamental software analysis pack for a new piezoelectric probe designed to reproduce the arterial pressure waveform from the pulsatile activity taken non-invasively at the vicinity of a superficial artery. The output PPIA is the coordinates (in time and amplitude) of the above referred points. To assess the accuracy of the algorithm, a reference database of 173 pulses from eight volunteers, was established and the values yielded by the PPIA were compared to annotations from a human expert engineer (HEE). The quality of the results is statistically quantified either in time as in amplitude. Average values of 4.20% for error, 99.09% for sensitivity and 96.77% for positive predictive value were found to be associated to time information while amplitude yields averages of 2.68%, 99.08% and 98.22%, respectively, for the same parameters.

Abstract
Pulse wave velocity (PWV) is a clinically interesting parameter associated to cardiac risk due to arterial stiffness, generally evaluated by the time that the pressure wave spends to travel between two arbitrary points. Optic sensors are an attractive instrumental solution in this kind of time assessment applications due to their truly non-contact operation capability, which ensures an interference free measurement. On the other hand, they can pose different challenges to the designer, mostly related to the features of the signals they produce and to the associated signal processing burden required to extract error free, reliable information. In this work we evaluate two prototype optical probes dedicated to pulse transit time (PTT) evaluation as well as three algorithms for its assessment. Although the tests were carried out at the test bench, where "well behaved" signals can be obtained, the transition to a probe for use in humans is also considered. Results demonstrated the possibility of measuring pulse transit times as short as 1 ms with less than 1% error.

Abstract
The present work proposes a new device for local pulse wave velocity (PWV), by using an innovative configuration of a double piezoelectric (PZ) sensor probe. PWV is assessed in one single location and involves the determination of time delay, between the signals acquired simultaneously by two PZs, 23 mm apart. The double probe (DP) is characterized in a dedicated test bench system, where two main studies were carried out. In the first one, the impulse response (IR) for each PZ sensor is determined and evaluated through the deconvolution method. In the second one, DP time resolution is estimated from a set of time delay algorithms and compared with the reference values, obtained through the signals of two pressure sensors. Results demonstrate the effectiveness of the inferred IRs in deconvolution purposes and the possibility of measure higher PWV values (approximate to 19m/s), through the DP, with an error less than 10%.

Abstract
The problem of using a piezoelectric (PZ) probe to non-invasively measuring the pressure wave propagation through a fluid contained in an elastic tube is considered in this paper. In particular, we describe a probe system designed to non-invasively reproduce the morphology of the pulsatile arterial pressure waveform (APW). The study is focused in three main issues: the mechanical interface that transmits the forces associated to the distension of the wall of the tube to the sensor, the electronic conditioning circuit and the methods to assess the global accuracy of the system. The circuit, incorporates a, new to our knowledge, baseline restorer (BLR) that contributes to maintaining a stable (non-floating) baseline of the cardiac pressure pulses, making real-time observations more effective. Identification and correction of the systematic errors, responsible for deviations of the correct output morphology, are also discussed and tested for different waveforms. To assess the performance of the probe a special purpose test bench was developed that can originate an arbitrarily shaped pressure wave and launch it through a silicone-rubber tube. Finally, preliminary results, taken at the carotid site of a set of human volunteers, are shown. The probe can be incorporated in a collar, and its pulse waveforms exhibit high intra-patient repeatability. It has the potential of being used as an alternative to costly techniques such as ultrasound or applanation tonometry. The root mean square error (RMSE) of the probe when reproducing cardiac-like pressure waveforms yielded a value of 1.8 +/- 0.22%.