Our thesis is simple: Cuffless BP monitoring can be made possible with a pressure-less sensing modality that can capture arterial pressure waveform with the same sensitivity as applanation tonometry.
A Scientific Approach to Cuffless Blood Pressure Monitoring
Long considered the “holy grail” in health monitoring, many companies have attempted or are attempting to develop a cuffless blood pressure monitor that can be worn on the wrist and keep a tab on a person’s blood pressure around the clock.
In the past two decades, volume clamping and applanation tonometry have emerged as suitable techniques for measuring blood pressure without a cuff. Volume clamping-based blood pressure monitoring has not evolved beyond in-patient applications due to the bulk and the complexity in attaching the device to the patient.(ref) More recently, FDA cleared an ambulatory blood pressure monitor that uses applanation tonometry as its underlying technology. Applanation tonometry relies on the use of a cylindrical plunger to applanate the radial artery and necessitate the use of continuous external force upon the wrist which has shown to cause pain and bruising.(ref)
A number of startups have attempted to solve cuffless blood pressure monitoring by leveraging a combination of off-the-shelf ECG and photoplethysmography (PPG) sensors to estimate blood pressure. While promising, there is some evidence that the accuracy of blood pressure estimation of such a system may be affected by variability of pre-ejection period (PEP) measured by the ECG.(ref) Additionally, PPG can be susceptible to interference from variations in ambient light, the presence of tattoos, or perspiration at the site of measurement.(ref)
Blumio’s innovative sensor was specifically developed to overcome the limitations of the technologies currently available on the market. All the aforementioned approaches rely on sensors that measure signals through direct, constant contact with the body.
- Wearable Millimeter-Wave Device for Contactless Measurement of Arterial Pulses
- Arterial Pulse Measurement with Wearable Millimeter Wave Device
- Derivation of Central Aortic Pressure Using the Radial Pulse Waveform Acquired by Millimetre-Wave Radar
Radar has been used in the past to assess vital signs.(ref) By measuring electromagnetic waves reflected from a target area of the body, it is possible to capture and record signals corresponding to respiration and blood circulation. With the advent of lower power radar chipsets with high sensitivity and faster processors, Blumio is the first to combine the high sensitivity of a millimeter-wave radar with a wearable concept to create a new system for measuring arterial pulses at the wrist.
Principle of Operation
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With each beat of the heart, the pulsation travels along the artery and create microscopic motions on the surface of the skin.
Using radar, our sensor reads in these motions and translates them into a high fidelity arterial pressure waveform.
The arterial pressure waveform is analyzed by our proprietary algorithms to extract blood pressure and other cardiovascular metrics.