Design a Moving Artifacts Detection System for a Radial Pulse Wave Analyzer

Despite recent studies on development of pulse wave analyzers and needs for commercializing them, the reproducibility is one of the most controversial issues as ever. Because the pulse pressure value, which is one of the important parameters to evaluate reproducibility, is very vulnerable to moving artifacts, the reproducibility can not be obtained easily. In this paper, we designed a moving artifacts detection system for a radial pulse wave analyzer so that it can be robust to this kinds of artifacts by excluding the contaminated parts from the pulse wave signal to be analyzed. This moving artifacts detection system was designed to consist of a three-axis accelerometer, an electromyography amplifier and a two-axis tilt sensor. To assess the suitability of the system, we examined the characteristics of each sensor's output signals with regard to the three motions such as extension, flexion and rotation. And, we also examined the each sensor's response to the highfrequency and low-frequency moving artifacts while the pulse wave signal was acquired from a pressure sensor for the pulse diagnosis. From these results, we could find that the response to subject's motions would be reflected in electromyography signal first, accelerometer signals and tilt sensor sequentially. And, the facts that a stable pulse wave can be acquired in two seconds after high frequency or low frequency motions ended were also found. Consequently, based on these findings, we set up some rules on the moving artifacts detection and designed an algorithm which is fit for our moving artifacts detection system.