Pressure Waveform Estimation in Elastic Vessels Using Exciter-Detector Devices: Towards a Novel Approach for Cardiovascular Condition Assessment

Objective: This work finds its motivation in the impact that non-invasive, accurate and non-expert operable instrumentation may have on the monitoring of cardiovascular condition and proposes a new class of exciter-detector devices suited to the extraction of multiple hemodynamic parameters. Materials: The devices' sensing unit is based on an innovative piezoelectric (PZ) sensor - MEMs accelerometer combination that enables the accelerometer to sense the vibrations produced by the PZ. The method for pressure waveform estimation relies on the amplitude modulation effect that occurs when the fluid pressure transmitted through the vessel wall attenuates the PZ oscillations sensed by the accelerometer. Methods: Two generations of devices were developed and characterized in a dedicated bench test system that was able to replicate the variability of a wide range of clinically relevant properties of the cardiovascular system. Results: The demodulation process yielded excellent results in recovering the morphology of pressure wave in bench test conditions. For the two developed prototypes, several waveforms were accurately extracted from the acceleration, current or power modulated carriers using the envelope and product detector algorithms. It was possible to reproduce the pressure waveform for successive higher applanation positions of the elastic tube at the bench test with a root mean square error of 2.4 ± 0.51%, when considering the best extracting method. Conclusion: The results obtained provide great prospects regarding the use of this group of devices as valid alternatives to currently available systems for pressure waveform assessment in physiological arteries.