OLAM: A wearable, non-contact sensor for continuous heart-rate and activity monitoring

A wearable, multi-modal sensor is presented that can non-invasively monitor a patient's activity level and heart function concurrently for more than a week. The 4in² sensor incorporates both a non-contact heartrate sensor and a 5-axis inertial measurement unit (IMU), allowing simultaneous heart, respiration, and movement monitoring without requiring physical contact with the skin [1]. Hence, this Oregon State University Life and Activity Monitor (OLAM) provides the unique opportunity to combine motion data with heart-rate information, enabling assessment of actual physical activity beyond conventional movement sensors. OLAM also provides a unique platform for non-contact sensing, enabling the filtering of movement artifacts generated by the non-contact capacitive interface, using the IMU data as a movement noise channel. Intended to be used in clinical trials for weeks at a time with no physician intervention, the OLAM allows continuous non-invasive monitoring of patients, providing the opportunity for long-term observation into a patient's physical activity and subtle longitudinal changes.

I. Introduction

Continuous monitoring of patients is becoming increasingly important in personalized healthcare. Conventional data obtained from a medical clinic – such as blood tests, saliva swabs, and vital sign measurements (blood pressure, pulse rate, respiration) – are typically coarsely captured at infrequent doctor's visits, thereby offering a limited glimpse into the condition of a patient's health. This paper presents the Oregon State University Life and Activity Monitor (OLAM), a low-cost, robust, non-invasive device designed for monitoring the activity of patients continuously for weeks at a time. The OLAM is composed of a contactless heart-rate sensor similar to [2] coupled with a five-axis inertial measurement unit (IMU). This combination of movement fused with heart-rate data provides a more accurate measurement of activity over these extended periods compared with sensors that capture either of these senses individually.