Home-telecare of the elderly living alone using an new designed ear-wearable sensor

This paper presents a new ear-wearable vital sign sensor designed for homecare of the elderly or other vulnerable people living alone. The device was comprised of a sensing body equipped with a pair of infrared LED and phototransistor and a dual-axis accelerometer, and an MP3 device-like control box with batteries. The sensing body was worn on the subject's ear and could detect the photoplethysmography (PPG) signals from the back of the subject's auricle. The PPG signals were sent to a computer wirelessly for heart rate calculation and abnormality detection. The program could automatically alarm and transmit the saved data to a center through modem when the heart rate was out of the normal range which decided by a time-wise baseline algorithm. The acceleration signals were used to eliminate the motion artifacts in the calculation of the heart rate. The comparison of the results obtained by this ear-wearable sensor and a commercially available fingertip sensor showed that the accuracy and reliability of it were acceptable. It was also found in the field test that the ear-wearable sensor could be worn comfortably and inconspicuously by the subject and the system could work continuously for approximately 120 hours without replacement of the batteries.