Photoplethysmogram analysis and applications: An Integrative Review (Preprint)

UNSTRUCTURED Photoplethysmogram is a biological signal with a high possibility of providing various hemodynamic information. Its measurement principle is simple and easy to implement. With the development of wireless communication technology, photoplethysmogram is increasingly used for the purpose of measuring the physiological state of an individual in a daily life beyond its use in a clinical environment. An example of this is that wearable devices such as smart watches and smartphones are increasingly providing healthcare services based on photoplethysmogram measurement. Despite increased spread and use of photoplethysmogram, it is not possible to specify the processing method of photoplethysmogram. Such method is considered a gold standard, including its pre-processing method. It is being studied in various ways by individual researchers. Unlike other reviews focusing on the measurement principle and clinical application of photoplethysmogram, this review examines existing research cases on photoplethysmogram about its generation mechanisms, measurement principles, clinical applications, noise definition, pre-processing techniques, feature detection techniques, and post-processing techniques for photoplethysmogram processing, especially from an engineering point of view. Furthermore, this review describes the flow of current signal processing techniques for photoplethysmogram and suggests future directions that photoplethysmogram processing research will be directed. In particular, this review looks at photoplethysmogram noise reduction technology using peak detection technology and signal quality assessment technology known to be important elements for the practical use of photoplethysmogram from a technical perspective.