Medical Engineering Thesis Defense, Alessio Tamborini

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Abstract: Current diagnostic methodologies in cardiology face large tradeoffs between procedure invasiveness and diagnostic reliability, ultimately requiring individuals to undergo cardiac catheterization for accurate diagnosis. Given the current societal burden of cardiovascular disease, there is a need for translational medical devices that bridge the accuracy gap between invasive and non-invasive measurement in the assessment of heart health. This thesis focuses on the development and validation of a high-resolution cuff-based system for assessment of central cardiovascular health.

Traditional pressure cuffs suffer low signal resolution when applied to non-invasive pulse waveform acquisition. In the first section of this thesis we develop a cuff-based device with a pneumatic filter for high fidelity pulse waveform acquisition. This work discusses the design and functionality of the cuff-device, and investigates the repeatability of the cuff-based measurement. Furthermore, the derived mathematical model of the pneumatic filter is shown to have an equivalent behavior to an electrical low-pass filter inclusive of a time constant and a frequency response curve.

The accuracy and reliability of the pulse waveform features from the cuff-device are evaluated with human study data. Firstly, an IRB study is performed at Caltech on a young and healthy population showing that the cuff-device data lies within a narrow distribution indicative of the healthy nature of the population. Secondly, data from a clinical trial collecting simultaneous invasive catheter, cuff and electrocardiogram is analyzed. The first analysis compared waveform parameters from the cuff in supra-systolic hold pressure with simultaneous aortic catheter, showing strong correlations between the two measurement modalities for both magnitude and fluctuations thereof.

Lastly, this work investigated the relationship between cuff-based parameters and left ventricular functions. We introduced a cuff-based method for extraction of the pressure-sound waveform, a pressure based surrogate of heart sounds. The results from this analysis showed that the pressure-sound features correlate with the strength of the left ventricular isovolumetric contraction and relaxation. Other important results from this work demonstrated the correlations between the heart-lung interactions in the left ventricle and cuff parameters: breathing fluctuations proportionally affect left ventricular pressures and cuff supra-systolic waveform parameters. Overall these results support

the accuracy and reliability of a cuff-based device for central cardiovascular health assessments.