Abstract 4115642: Resonance Sonomanometry in an Early Prototype Device Effectively Measures Continuous, Noninvasive Blood Pressure

Background: Nearly half of American adults have hypertension; however, reliable, continuous, noninvasive blood pressure (BP) measurement (cNIBP) for inpatient and outpatient use is not currently available. This study evaluated a new method for cNIBP measurement called resonance sonomanometry (RSM). RSM derives blood pressure using first-principles physics, is applicable to any artery, and requires no calibration, blood vessel deformation, or dependence on demographic inputs. Methods: A prospective, observational feasibility study was undertaken to compare carotid artery BP measurements with a prototype ultrasound-based cNIBP device incorporating RSM, to arterial catheter BP measurements in the radial arteries of 60 test subjects. Catheter measurements were obtained from a distal peripheral artery (radial), oscillometric cuff from the brachial artery, and RSM was obtained from a central artery (carotid). This study was the first-in-human study for the RSM method in comparison to arterial catheters. Results: RSM-induced arterial resonance was observed in all tested subjects. For each of the subjects, the arterial resonant frequency increased with increasing BP during systole, and decreased with diastole (consistent with the cardiac cycle), as predicted by the physical model. RSM-derived BP traces were qualitatively similar to catheter data, exhibiting features such as the dicrotic notch. The RSM method yielded similar diastolic BP (DBP), but lower systolic BP (SBP) compared to the arterial catheter, likely due to expected peripheral pulse amplification. RSM DBP was not significantly different from the catheter (+1.5mmHg, p = 0.187), while BP cuff DBP was significantly different from the catheter (−4.3mmHg, p=0.002). There were significant differences in the catheter to RSM SBP (34.1 mmHg, p < 0.01), consistent with the aforementioned expectations from a central-versus-peripheral continuous pressure measurement. Conclusions: RSM is a novel BP measurement technique that could enable cNIBP measurements with accuracy required in hospitals. While the data are promising, significant future work remains. The study was meant to test the RSM method, not the device or form factor. Consequently, the form factor will need to be improved prior to clinical use. The prototype was designed for manual operation; thus, future work will also be needed to enhance the ability of the device to autonomously locate and track the artery for ease of use.