| MS Seminar

Name of the Speaker: Ms. Ishwarya S (EE22S058)
Guide: Dr. Jayaraj Joseph
Online meeting link: http://meet.google.com/dwf-bmnh-qka
Date/Time: 19th May 2025 (Monday), 2 PM
Title: Methods and systems for self-assessment of arterial stiffness : Taking early vascular assessment to home and primary care.

Abstract :

Cardiovascular disease (CVD) is the globally leading cause of death due to Non communicable disease (NCD). Effective early detection and prevention is hampered not by a lack of diagnostics, but by limited access to systems for reliable assessment of Early markers such as Endothelial function and vascular stiffness. Existing techniques, such as aortic pulse wave velocity (PWV) and local PWV, require costly, operator-dependent systems confined to tertiary care. This thesis proposes accessible, user-friendly, and cost-effective alternatives. It introduces a suite of non-invasive PWV measurement systems designed to minimize operator involvement and enable reliable arterial stiffness assessment in home and primary care settings.

An initial system employed acoustic plethysmography to record carotid pulse signals, showing strong correlation with in-vitro standards (r > 0.87) and high repeatability (CoV < 4%). However, signal integrity degraded in subjects with high adiposity due to soft tissue interference. To address this, a quad-LED PPG system using near-infrared illumination was developed. It improved waveform fidelity (CoV < 7%) and demonstrated good usability in a study (N=65), with strong inter-/intra-operator consistency, agreement with reference standards, and enhanced tissue penetration. Limitations included difficulty in femoral access and posture-induced variability.

Subsequently, a heart-to-carotid PWV system was developed using a chest-worn phonocardiogram (PCG) to detect aortic valve opening, coupled with a dual-PPG neckband for carotid waveform acquisition. While technically sound, the need for manual PCG probe placement reduced its suitability for unsupervised use. The final system integrates a dual-bladder brachial cuff with flexible piezoelectric film sensors at fixed proximal and distal sites, removing the need for anatomical alignment or distance estimation. The developed sensor system has a larger sensing area, ensuring consistent waveform capture across multiple arm morphologies. In-vivo validation studies demonstrated average pulse transit times (PTTs) of 36 ± 4.6 ms, 34 ± 3.9 ms, and 40 ± 3.9 ms for normal, moderate, and bulky arm types, corresponding to PWVs of 4.1 ± 0.3 m/s, 4.4 ± 0.38 m/s, and 3.6 ± 0.78 m/s, respectively. These values are consistent with reported literature. The system achieved SNR > 20 dB, beat-to-beat CoV < 11%, and intra-subject repeatability of ±0.06 m/s. Comprehensive phantom and human studies confirm its robustness, reliability, and suitability for scalable, low-cost EVA and cardiovascular risk monitoring in decentralized settings.