SCH: A biomechanics-guided wireless ultrasonic e-tattoo with an application specific integrated circuit for ambulatory blood pressure monitoring

Although ambulatory blood pressure monitoring (ABPM) has been used to detect sources of cardiovascular mortality (e.g., hypertension and abnormal BP rhythms) for over six decades, current ABPM devices are still not yet widely adopted by the general population. Cuffless ABPM approaches are clearly more user-friendly, but have yet to achieve acceptable accuracy. The objective of this SCH project

is to create a paradigm-shifting cuffless ABPM device based on biomechanics-guided wireless ultrasound e-tattoo sensors. The specific aims include (1) designing an ultra-low-power and millimeter-size application-specific integrated circuit (ASIC) capable of duplex mode ultrasound to be used in a soft,

wrist-laminated, wireless ultrasound e-tattoo (WUET) for continuous monitoring of absolute anatomic and fluidic features. (2) establishing a fundamental biomechanics model to extract BP using the aforementioned hemodynamic measurables. (3) pilot clinical validation of the WUET on patients with arterial catheter insertions in Dell Children's Medical Center using SickbayTM virtual patient monitors for

simultaneous data acquisition. The four PIs bring together well-established expertise in analog/mixed ASIC design (Jia), low-power wireless e-tattoos (Lu), cardiovascular biomechanics (Han), and pediatric cardiac intensive care (Mery) to synergistically tackle this grand challenge. This approach fundamentally

differs from previous cuffless continuous noninvasive BP (cNIBP) sensing methods that rely on traditional wearables modalities only capable of measuring relative and indirect hemodynamic features. Such modalities then require empirical (e.g., machine learning) models for cNIBP despite inherent inaccuracies

and constant calibration requirements caused by poor understanding of the underlying mechanisms and bias to training data. While ultrasound can capture the absolute metrics required for biomechanics-based models, state-of-the-art wearable ultrasound sensors are still constrained by bulky back-end control and

data acquisition systems. The proposed analog-edge-computing of hemodynamic feature extraction enables true wireless implementation by dramatically reducing power consumption and sensor size. Our preliminary results demonstrate the feasibility of anatomic and Doppler-based feature extraction purely using analog circuitry. The proposed ABPM WUET can ultimately replace invasive arterial catheters in

clinical spaces while also enabling ambulatory monitoring of the broader outpatient populations. RELEVANCE (See instructions): Cardiovascular disease is most effectively treated through early diagnosis and preventative measures, and this project provides a new method of cuffless blood pressure monitoring that is still accessible and

patient-friendly. A greater fundamental understanding of vascular biomechanics and a new wearable vascular measurement modality will be established. This project is committed to NHLBI's mission for advancing translational research, with focuses on real patient usability in clinical and outpatient settings.