One of the holy grails of wearable health tech is an optical sensor that can measure blood pressure accurately. Many companies are working toward such a solution, but for now, the most reliable results still come from devices that use a pressure cuff to restrict blood flow. These devices tend to be bulky and they use a lot of power so they cannot be used frequently throughout the day without recharging or changing batteries. It’s not a practical solution if you want to provide constant blood pressure monitoring.

ViCardio is a device developed by Tarilan Laser Technologies. It uses an optical sensor for measuring blood pressure on the wrist, but it does not work the same way that most optical sensors work. On most activity trackers and smart watches, LEDs shine light on the skin of the wrist and then optical sensors make measurements of the reflected light. This works well for detecting heartbeats, but so far has proven to be difficult to use for accurate blood pressure readings. The ViCardio device is actually an “opto-mechanical” sensor system. The change in blood pressure in a wrist artery causes a button to move inside the case, which in turn obstructs a light signal to varying degrees. With more pressure, the button rises higher and blocks more of the light. The amount of light reaching the sensor indicates the position of the button, and this relative change reveals the beat-to-beat changes in pressure. The result is a device that can take continuous blood pressure readings without resorting to a pressure cuff.

The Tarilan website points out that the device needs no calibration. The company also offers other devices that can be worn on other parts of the body, including arms and legs, wherever the motion of aterial blood flow can be sensed. Clinical trials have demonstrated that the technology meets CE and FDA standards. Since it is a mechanical device, however, it may be that its readings might be affected by external forces such as physical motion or pressure from clothing. On the other hand, it would be reasonable to expect that the technology could be made considerably smaller, which could increase accuracy and convenience.

This technology could be a useful tool in combating hypertension. It can help people identify high blood pressure conditions and provide constant monitoring of pressures during normal activities in addition to the normal at-rest readings taken in clinical settings.