Radar-Based Blood Pressure Sensors on the Way

Infineon Technologies has announced an agreement with Blumio to jointly develop a wearable blood pressure sensor based on Infineon’s Xenxiv chipset. The new sensor is expected to make a strong contribution to the wearable cardiovascular monitoring device market, enabling continuous and accurate measurement without a cuff.

The project combines Infineon’s radar sensor expertise with Blumio’s software technology. A kit combining the two technologies should facilitate time-to-market for easy integration into blood pressure monitoring devices.

“Blood pressure is the single most important indicator of someone’s health. Its fluctuation is based on anything that you’re doing for your body to react to both internal influences in the body as well as external influences”, said Catherine Liao founder and CEO of Blumio.

The collaboration with Blumio shows the work that Infineon is doing to support innovative start-ups with its Silicon Valley Innovation Center (SVIC), which is dedicated to developing cutting-edge technologies that make our life easier, safer, and greener. With SVIC, Infineon is looking to promote regional startups and bring new technologies to the market.

Radar technology
Knowing your blood pressure rate can be critical, and the ability to monitor it is considered the Holy Grail when it comes to health. Nowadays, everyone wears a Fitbit that keeps track of their heartbeats and their sleep. But there is still no ability to track blood pressure. The only way to monitor blood pressure is to use a blood pressure cuff that inflates and deflates.

“And if you want to see what your blood pressure fluctuation is over a day, you have to wear an ambulatory blood pressure cuff that takes a measurement every half an hour or so,” said Liao.

She continued, “if you think about what’s available off-the-shelf, ECG sensors and optical sensors that you see in wearables, none of these sensors can really tell you what they are measuring and what is happening inside of your cardiovascular system. The ECG is measuring the heartbeats’ electrical signal and the optical sensor is measuring blood volume.”

The Blumio Infineon collaboration is coming up with a possible solution that measures blood pressure without a cuff using radar that monitors a person’s blood pressure 24 hours a day.

The radar offers several advantages over passive infrared (PIR) technology in motion detection applications. These include higher accuracy and more precise measurement of detected objects, paving the way for new solutions in various fields.

“We wanted to know how to use the radar to measure things that are very, very close, and with tiny movements, I’m sure all of us have measured our heart rate by either putting our finger on our neck or our wrists and felt the pulsation of the artery with each heartbeat. The strength of the pulsation is caused by the amount of pressure that is traversing through your body, and propagates outwards from your vessel out to the surface of the skin,” said Catherine.

In the past two decades, volume clamping and applanation tonometry have emerged as suitable techniques for measuring blood pressure without a cuff. These techniques have found limited acceptance beyond the hospital field.

Several startup companies have attempted to solve blood pressure monitoring without a cuff by using a combination of ECG and photoplethysmographic (PPG) sensors to estimate blood pressure but have been struggling to achieve a sufficiently clean signal. Light-based solutions can also suffer from interference problems due to the presence of external light variations or tattoos.

Radar differs from other technologies as it is impervious to skin color and variations in ambient light. By measuring electromagnetic waves reflected from a target area of the body, it is possible to capture and record signals corresponding to breathing and blood circulation through the use of low power chipsets with high sensitivity.

With each heartbeat, the pulse travels along the artery and creates microscopic movements on the surface of the skin. The radar reads these movements and translates them into a waveform. The blood pressure waveform is analyzed by the algorithm to extract blood pressure and other cardiovascular metrics.

Figure 2: how the radar technology works for blood pressure measurement.
Figure 2: how radar technology works for blood pressure measurement.

Blumio & Infineon
The sensor Infineon and Blumio developed is designed to overcome the limits of the technologies currently available on the market through direct and constant contact with the body.

The main challenges are related to the capturing and detecting of the signal, i.e. ensuring the sensor is placed in the right location to capture the pulsation of the artery and ensuring the radar is sensitive enough to capture the motion accurately. The second challenge is related to the solutions’ ability to reject motion artifacts not related the pulse. Once these problems are solved, the advantage of the radar is that it provides a high-speed acquisition without creating uncomfortable pressure points, while allowing many measurements to be made throughout the day.

“Now, the second challenge is really a must. How do we know that’s the actual signal that you think that you’re measuring? And this is where the majority of our time is spent in. Because in anything that’s scientific, you have to validate your signal with a known reference,” said Catherine.

What has been done is to acquire a considerable amount of data and compare the signals with those from cuff-based blood pressure monitors, thus perfecting the algorithm.

Blumio and Infineon are working on perfecting the acquisition hardware and its measurement error. “There’s an ISO standard that requires an error of less than plus or minus five millimeters of mercury with a standard deviation of less than eight millimeters. And so that is the target that we’re working on. We are currently in the process of performing clinical data collections on humans,” said Adrian.

SVIC and Blumio are partnering to develop a sensor that produces high-quality arterial waveforms that may be used to measure blood pressure continuously throughout the day, without a cuff, for a better management of heart health. Unobtrusive measurement makes it possible for the device to be worn throughout the day and night.

Source: EE Times


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