Graduate Student Seminar Series – Rawad Alkallas

Graduate Student Seminar Series
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Location: MS2158 – 1 King’s College Circle
Presentation Title: Multimodal cardiovascular sensing for hemodynamic characterization beyond blood pressure
Abstract:
Blood pressure (BP) is a central marker of cardiovascular status, but intermittent measurements may not reveal the cause or severity of hemodynamic dysfunction. In heart failure, neurohormonal compensation and increased systemic vascular resistance (SVR) can preserve a normal BP despite reduced cardiac output (CO) and impaired tissue perfusion. Similarly, in septic shock, vasopressors may restore arterial pressure while abnormalities in CO, SVR, and microvascular perfusion persist. Continuous assessment of hemodynamic variables may reveal deterioration missed by BP alone and support earlier intervention beyond episodic clinical evaluations.
This research develops a multimodal wearable platform for remote, continuous, non-invasive estimation of BP, CO, SVR, and peripheral perfusion using electrocardiography (ECG), multispectral photoplethysmography (PPG), and transthoracic impedance cardiography (ICG). Fourteen healthy participants completed three sessions incorporating baseline, cold pressor, maximal-inspiratory breath hold, sustained handgrip, graded cycling, and sauna exposure. These stimuli perturb cardiovascular regulation through distinct physiological entry points: cold induces sympathetic vasoconstriction, cycling increases metabolic demand and CO, breath holding alters intrathoracic pressure, handgrip activates the exercise pressor reflex, and heat promotes peripheral vasodilation. Together, they generate diverse hemodynamic states for evaluating multimodal monitoring.
Signals were recorded synchronously with Finapres Nova and PeriFlux laser Doppler flowmetry references. ECG and PPG provided heart rate and pulse arrival time, while ICG provided stroke volume and CO estimates. Multi-wavelength time delay (MWTD), derived from timing differences across visible-to-near-infrared PPG wavelengths, was investigated as a marker of peripheral vascular dynamics and perfusion and compared with PeriFlux measurements. Complementary, partially redundant signals were integrated through physiologically informed sensor fusion to improve robustness and accuracy of BP, CO, and SVR estimation.
Using participant-wise leave-one-out cross-validation, a full feature set comprising pulse arrival time, MWTD, CO, stroke volume, and heart rate achieved 86.4% accuracy in classifying physiological conditions, compared with 75.9% using pulse arrival time and heart rate alone. Ongoing work will validate hemodynamic and perfusion estimation in patients with heart failure and miniaturize the platform into a wearable chest module and finger ring. The system is intended to enable longitudinal monitoring at home, identify meaningful changes between visits, and characterize why BP changes rather than whether it changes.
Supervisor Name: Daniel Franklin
Year of Study: 5
Program of Study: PhD
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