A system for assessing motion artifacts in the signal of a micro-optic in-ear vital signs sensor

Cardiovascular diseases are among the most common causes of death in developed industrial nations. It is of great interest of both physician and patient to determine the cardiovascular risk factors early in order to take preventive measures. To assist these investigations we develop a wearable in-ear measuring system (IN-MONIT) for 24/7 monitoring of heart rate and oxygen saturation (SpO2). The central component is a micro-optic remission/reflection sensor (MORES) located inside the auditory canal. From the measured photoplethysmographic curves the aforementioned vital signs can be derived. In the following we present a recording system for assessing motion artifact influence in the in-ear sensor data. Two accelerometer sensors record posture and motion while at the same time SpO2, heart rate and PPG are measured using both a commercial sensor and the in-ear sensor. The data is transmitted wirelessly to a control PC for storage and further investigation. Using this system we assessed the influence of motion artifacts produced by daily life activities on infrared and red in-ear PPG data and on readings of the reference sensor.