Wearable Ring-Based System for Measuring Hemodynamic Parameters

Currently there are no reliable and convenient wearable solutions for measuring blood pressure, which remains a key indicator of cardiovascular health. Many existing measuring systems are bulky, complex and expensive, which limits their practicality for everyday use for wearable application. We introduce a compact, ring-shaped blood pressure measurement device as a proof-of-concept. It is based on a local oscillometric spot measurement obtained from the base of the index finger. The ring is made of two parts, where the outer sleeve induces pressure to the finger, and the inner guide bushing houses a ring sensor unit, which incorporates a commercial photoplethysmography module and a force-sensitive resistor. Manual rotation of the outer part of the ring applies pressure that occludes the digital artery, allowing estimation of blood pressure. For evaluation, we compared the results from our device with reference measurements from a brachial cuff blood pressure monitor. Ten volunteers underwent three to six measurements. The ring was able to capture moderate-quality oscillometric responses. The results (Bland-Altman: Systolic mean difference $\mu$ =1.1mmHg and standard deviation $\sigma$ =9.5mmHg, diastolic $\mu$ =0.1mmHg and $\sigma$ =13.4mmHg) demonstrate the feasibility of the approach. There are still many sources of uncertainty, but these results highlight the potential of this new setup. As a proof-of-concept, the current setup lays the groundwork for future improvements. With further mechanical refinements and system simplifications, this wearable ring offers a promising pathway to accessible, comfortable, and portable blood pressure monitoring.