A wearable signal acquisition system for physiological signs including throat PPG

This paper presents a wearable signal acquisition system, which can measure physiological signs, i.e., electrocardiogram (ECG) and photoplethysmogram (PPG). The system is comprised of two parts: (1) an ECG sensor implemented in the master board which will be mounted on the chest and, (2) a combined PPG and motion sensor implemented in the slave board which will be worn around the neck area. The single-lead ECG, the single-channel PPG, and the 3-channel accelerometer signals are all sampled at 200Hz, and transmitted to an Android app through Bluetooth® low energy (BLE) in real time. The system is powered by a 3.7V lithium polymer battery, with an average current consumption of 10mA. In addition to giving an overview of the system design and implementation decisions, we summarize the finding of a PPG test region study based on our system, which indicates that the highest PPG stability is in the mid-throat region over the thyroid gland, and the PPG in the lower throat region is an excellent choice for respiration rate extraction with an average error less than 5%. With the assistance of the motion sensor, an obvious swallow motion can also be easily identified.