A Downloadable Oscillometric BP Monitor for All Smartphones with No Attachments

Investigators:
Edward Jay Wang, Billion Labs Inc.

MassAITC Cohort: Year 3 (Aging)

Project Accomplishments: Billion Labs developed VibroBP—a smartphone application that measures blood pressure at the fingertip using oscillometry without requiring any external attachments. The technology uses a novel Smartphone Force Vibrometry (SFV) technique where a user places their finger on the phone’s camera while the screen illumination and camera measure pulse amplitude via photoplethysmography (PPG), and applied pressure is determined by vibrating the phone and analyzing changes in vibration amplitude with the onboard inertial measurement unit (IMU). The project had three aims: developing a cross-model smartphone force vibrometry algorithm (Aim 1), conducting human subject validation with 85 subjects including a naturally hypertensive population (Aim 2), and performing usability assessment with older adults (Aim 3). All aims were successfully achieved, including completion of the 85-subject clinical validation study at UCSD ACTRI and usability studies with 24 participants at Belmont Senior Living and UCSD. 

Major breakthroughs during the project included enabling fully handheld measurement (removing the requirement that the phone rest on a table), an iOS sensing breakthrough using an acoustic side channel with a provisional patent filed, and a successful FDA Q-sub meeting that determined the device requires a De Novo regulatory pathway.

Initial Proposal Abstract: Hypertension has long been regarded as a key marker for screening towards healthy aging, being a key risk factor for cardiovascular diseases such as strokes and heart failure.Also, hypertension is more recently established as a risk factor for cognitive impairments. Currently, an estimated 46% of the 1.28 billion adults with hypertension are unaware of hypertensive condition and not seeking treatment. Diagnosing the nearly 500 million adults unaware of their hypertensive condition is an imperative first step towards addressing this crisis. This proposal aims to establish accessible early screening of hypertension by democratizing BP monitoring. We aim to achieve this by converting the billions of smartphones, focusing on the cheapest models, into oscillometric BP monitors without no hardware add-ons.

Our solution, VibroBP, performs BP measurement using a technique called oscillometry, which is the same underlying technology used in upper-arm cuff devices. To measure BP, two key measurements are required: (1) the PRESSURE applied to the artery and (2) the AMPLITUDE of the pulse in the artery being measured. Our system, called VibroBP, captures these two measurements in the following way. A user places their finger over the front facing camera while the phone is resting on a flat surface. The screen illuminates the finger while the camera measures the amplitude of the pulse through the use of photoplethysmogram (PPG). The novel insight that underly our proposed solution is a technique called Smartphone Vibrometric Force Estimation (VFE). VFE is based on a simple concept that a vibrating object will dampen when force is applied to it. By vibrating a phone with its internal vibration motor, our app can measure the force being applied by a user’s finger by measuring the vibration amplitude with the on-board inertial measurement unit (IMU). By measuring the force applied in real-time, the app guides the user to press in increasing pressure, until the pulse is cut off, which is measured by the camera. Finally, the pressure and pulse amplitude profile are converted to a BP oscillogram, which is used to calculate SBP/DBP.

In this pilot study, we aim to develop, validate, and refine our VibroBP solution through a series of user testing. Further, we plan to work closely with older adults to ensure our proposed solution works well for geriatric use. Through the success of this pilot, our goal is to pursue regulatory clearance of the VibroBP app for over-the-counter distribution for mass consumer use.

Outcomes: