Technion prototype cuffless blood pressure sensor on silicon photonics tested on volunteers

A team at the Technion-Israel Institute of Technology has described a wearable sensor that monitors blood pressure without an inflatable cuff, in Nature Communications. The device was developed by Prof. Amir Rosenthal, Prof. Daniel Lange and doctoral student Gil Gelbert of the Andrew and Erna Viterbi Faculty of Electrical and Computer Engineering. In proof-of-concept tests with volunteers, it captured features of the blood pressure waveform from the radial artery at 100 measurements per second, and its output agreed with a reference cuff-based monitor nature.comNature Communicationsnature.comOpen source ↗.

A cuff gives a reading at a single point in time. The Technion device is intended to measure continuously, with no action required from the user.

How the optoacoustic detector works

The device combines silicon photonics with optoacoustic excitation. Short light pulses generate ultrasound waves inside the artery, and a highly miniaturized silicon-photonics acoustic detector, named SPADE, picks them up. SPADE measures both the absolute diameter of the artery and its minute changes with each heartbeat. From these measurements the full blood pressure waveform can be reconstructed and pressure estimated in real time and over extended periods.

According to the Technion, this is the first time the absolute artery diameter has been measured with such a miniature sensing approach. Existing wearable solutions rely on pulse-echo ultrasound patches that track the pulsating arterial diameter. The authors note that their multi-element designs and need for precise alignment complicate use as a fully wearable device nature.comNature Communicationsnature.comOpen source ↗.

One element, tolerance to position

The optoacoustic signals have high contrast, and the detector has semi-isotropic sensitivity. Together they allow artery diameter to be monitored with a single detection element and give high tolerance to translation and rotation of the sensor. Despite its small size, the detector is sensitive enough to record optoacoustic signals from the radial artery with high contrast at 100 Hz.

The authors state that the agreement with the cuff-based reference monitor shows the potential of silicon-photonics optoacoustic sensing for continuous, cuffless monitoring in daily life. The work is at the proof-of-concept stage. Ron Moisseev, Yoav Hazan and Tamar Harary also took part in the study.